ADXL362 Datasheet

Analog Devices Inc.

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Datasheet

Micropower, 3-Axis, ±2 g/±4 g/±8 g
Digital Output MEMS Accelerometer
Data Sheet
ADXL362
Rev. F Document Feedback
Infor
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Technical Support www.analog.com
FEATURES
Ultralow power
Power can be derived from coin cell battery
1.8 µA at 100 Hz ODR, 2.0 V supply
3.0 µA at 400 Hz ODR, 2.0 V supply
270 nA motion activated wake-up mode
10 nA standby current
High resolution: 1 mg/LSB
Built-in features for system-level power savings:
Adjustable threshold sleep/wake modes for motion
activation
Autonomous interrupt processing, without need for
microcontroller intervention, to allow the rest of the
system to be turned off completely
Deep embedded FIFO minimizes host processor load
Awake state output enables implementation of
standalone, motion activated switch
Low noise down to 175 µg/√Hz
Wide supply and I/O voltage ranges: 1.6 V to 3.5 V
Operates off 1.8 V to 3.3 V rails
Acceleration sample synchronization via external trigger
On-chip temperature sensor
SPI digital interface
Measurement ranges selectable via SPI command
Small and thin 3 mm × 3.25 mm × 1.06 mm package
APPLICATIONS
Hearing aids
Home healthcare devices
Motion enabled power save switches
Wireless sensors
Motion enabled metering devices
GENERAL DESCRIPTION
The ADXL362 is an ultralow power, 3-axis MEMS accelerometer
that consumes less than 2 µA at a 100 Hz output data rate and
270 nA when in motion triggered wake-up mode. Unlike
accelerometers that use power duty cycling to achieve low power
consumption, the ADXL362 does not alias input signals by
undersampling; it samples the full bandwidth of the sensor at all
data rates.
The ADXL362 always provides 12-bit output resolution; 8-bit
formatted data is also provided for more efficient single-byte
transfers when a lower resolution is sufficient. Measurement
ranges of ±2 g, ±4 g, and ±8 g are available, with a resolution of
1 mg/LSB on the ±2 g range. For applications where a noise level
lower than the normal 550 µg/√Hz of the ADXL362 is desired,
either of two lower noise modes (down to 175 µg/√Hz typical)
can be selected at minimal increase in supply current.
In addition to its ultralow power consumption, the ADXL362
has many features to enable true system level power reduction.
It includes a deep multimode output FIFO, a built-in micropower
temperature sensor, and several activity detection modes including
adjustable threshold sleep and wake-up operation that can run
as low as 270 nA at a 6 Hz (approximate) measurement rate. A
pin output is provided to directly control an external switch when
activity is detected, if desired. In addition, the ADXL362 has
provisions for external control of sampling time and/or an
external clock.
The ADXL362 operates on a wide 1.6 V to 3.5 V supply range,
and can interface, if necessary, to a host operating on a separate,
lower supply voltage. The ADXL362 is available in a 3 mm ×
3.25 mm × 1.06 mm package.
FUNCTIONAL BLOCK DIAGRAM
V
S
V
DDI/O
GND
3-AXIS
MEMS
SENSOR
TEMPERATURE
SENSOR
AXIS
DEMODULATORS ANTIALIASING
FILTERS
ADXL362
12-BIT
ADC DIGITAL
LOGIC,
FIFO,
AND
SPI
INT1
INT2
MOSI
MISO
CS
SCLK
10776-001
Figure 1.
ADXL362 Data Sheet
Rev. F | Page 2 of 43
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 3
Specifications ..................................................................................... 4
Absolute Maximum Ratings ............................................................ 6
Thermal Resistance ...................................................................... 6
Package Information .................................................................... 6
Recommended Soldering Profile ............................................... 6
ESD Caution .................................................................................. 6
Pin Configuration and Function Descriptions ............................. 7
Typical Performance Characteristics ............................................. 8
Theory of Operation ...................................................................... 13
Mechanical Device Operation .................................................. 13
Operating Modes ........................................................................ 13
Selectable Measurement Ranges ............................................... 13
Selectable Output Data Rates .................................................... 13
Power/Noise Tradeoff ................................................................ 14
Power Savings Features .................................................................. 15
Ultralow Power Consumption in All Modes .......................... 15
Motion Detection ....................................................................... 15
FIFO ............................................................................................. 17
Communications ........................................................................ 17
Additional Features ........................................................................ 18
Free Fall Detection ..................................................................... 18
External Clock ............................................................................ 18
Synchronized Data Sampling .................................................... 18
Self Test ........................................................................................ 18
User Register Protection ............................................................ 18
Temperature Sensor ................................................................... 18
Serial Communications ................................................................. 19
SPI Commands ........................................................................... 19
Multibyte Transfers .................................................................... 19
Invalid Addresses and Address Folding .................................. 19
Latency Restrictions ................................................................... 19
Invalid Commands ..................................................................... 19
Register Map .................................................................................... 23
Register Details ............................................................................... 24
Device ID Register ..................................................................... 24
Device ID: 0x1D Register .......................................................... 24
Part ID: 0xF2 Register ................................................................ 24
Silicon Revision ID Register ..................................................... 24
X-Axis Data (8 MSB) Register .................................................. 24
Y-Axis Data (8 MSB) Register .................................................. 24
Z-Axis Data (8 MSB) Register .................................................. 24
Status Register ............................................................................. 25
FIFO Entries Registers ............................................................... 26
X-Axis Data Registers ................................................................ 26
Y-Axis Data Registers ................................................................ 26
Z-Axis Data Registers ................................................................ 26
Temperature Data Registers ...................................................... 26
Soft Reset Register ...................................................................... 26
Activity Threshold Registers ..................................................... 27
Activity Time Register ............................................................... 27
Inactivity Threshold Registers .................................................. 27
Inactivity Time Registers ........................................................... 27
Activity/Inactivity Control Register ........................................ 29
FIFO Control Register ............................................................... 30
FIFO Samples Register .............................................................. 31
INT1/INT2 Function Map Registers ....................................... 31
Filter Control Register ............................................................... 33
Power Control Register.............................................................. 34
Self Test Register ......................................................................... 35
Applications Information .............................................................. 36
Application Examples ................................................................ 36
Power............................................................................................ 37
FIFO Modes ................................................................................ 38
Interrupts ..................................................................................... 39
Using Synchronized Data Sampling ........................................ 40
Using an External Clock ............................................................ 41
Using Self Test ............................................................................. 41
Mechanical Considerations for Mounting .............................. 41
Operation at Voltages Other Than 2.0 V ................................ 41
Axes of Acceleration Sensitivity ............................................... 42
Layout and Design Recommendations ................................... 42
Outline Dimensions ....................................................................... 43
Ordering Guide .......................................................................... 43
Data Sheet ADXL362
Rev. F | Page 3 of 43
REVISION HISTORY
5/2019—Rev. E to Rev. F
Changes to Table 1 .............................................................................. 4
Changes to Default Mode Section ................................................. 16
Changes to Ordering Guide ........................................................... 43
11/2016—Rev. D to Rev. E
Changes to Endnote 3, Table 1 ........................................................ 5
Changes to Using Self Test Section and Table 22 Title ............... 41
11/2015—Rev. C to Rev. D
Change to Sensor Resonant Frequency Parameter, Table 1......... 4
Added Endnote 4, Table 1 ................................................................ 4
Changes to Figure 10 ........................................................................ 8
Changes to Selectable Measurement Ranges Section ................ 13
Changes to Bus Keepers Section ................................................... 17
Changes to Figure 36 to Figure 40 ................................................ 20
Changes to Figure 41 and Figure 42 ............................................. 21
Changes to Table 10 ........................................................................ 22
Change to Start-Up Routine Section ............................................ 37
Change to Table 22 .......................................................................... 41
Updated Outline Dimensions ........................................................ 43
12/2014—Rev. B to Rev. C
Changes to Table 1 ............................................................................ 4
Changes to Figure 14 and Figure 15 ............................................... 9
Change to Serial Communications Section ................................. 19
Change to Table 10 .......................................................................... 22
Changes to Soft Reset Register Section ........................................ 26
Changes to Example: Implementing Free Fall Detection
Section .............................................................................................. 37
Changes to Using Self Test Section and Table 22 ........................ 41
Changes to Figure 51 ...................................................................... 42
Updated Outline Dimensions ........................................................ 43
2/2013—Rev. A to Rev. B
Change to Figure 7 ............................................................................ 8
Changes to Figure 11, Figure 12, and Figure 13 ............................ 9
Changes to Table 7 and Table 8 ..................................................... 14
Changes to Figure 31 ...................................................................... 16
Change to Table 10 .......................................................................... 22
Change to Bit 6, Table 12 ................................................................ 25
Changes to Inactivity Time Registers Section ............................. 28
Change to LINK/LOOP Bit, Table 13 ........................................... 29
Change to ODR Bit, Table 17 ......................................................... 33
Changes to Figure 43, Figure 44, and Figure 45 .......................... 36
Changes to Start-up Routine Section, Figure 46, and
Figure 47 ........................................................................................... 37
Change to Figure 52 ........................................................................ 42
9/2012—Rev. 0 to Rev. A
Moved Revision History Section ..................................................... 3
Changes to Linking Activity and Inactivity Detection Section;
Added Figure 31, Figure 32, and Figure 33, Renumbered
Sequentially ...................................................................................... 16
Change to Table 13 .......................................................................... 29
Changes to Figure 44 ...................................................................... 36
Moved Power Supply Decoupling Section ................................... 37
Added Power Section, Power Supply Requirements Section,
and Figure 47 ................................................................................... 37
Updated Outline Dimensions ........................................................ 43
Changes to Ordering Guide ........................................................... 43
8/2012—Revision 0: Initial Version
ADXL362 Data Sheet
Rev. F | Page 4 of 43
SPECIFICATIONS
TA = 25°C, VS = 2.0 V, VDD I/O = 2.0 V, 100 Hz ODR, HALF_BW = 0, ±2 g range, acceleration = 0 g, default settings for other registers,
unless otherwise noted.1
Table 1.
Parameter Test Conditions/Comments Min Typ Max Unit
SENSOR INPUT
Each axis
Measurement Range User selectable ±2, ±4, ±8 g
Nonlinearity Percentage of full scale ±0.5 %
Sensor Resonant Frequency 3000 Hz
Cross Axis Sensitivity2 ±1.5 %
OUTPUT RESOLUTION Each axis
All g Ranges 12 Bits
SENSITIVITY Each axis
Sensitivity Calibration Error ±10 %
Sensitivity at XOUT, YOUT, ZOUT 2 g range 1 mg/LSB
4 g range 2 mg/LSB
8
g
range
m
g
/LSB
Scale Factor at XOUT, YOUT, ZOUT 2 g range 1000 LSB/g
4 g range 500 LSB/g
8 g range 235 LSB/g
Sensitivity Change Due to Temperature3 40°C to +85°C 0.05 %/°C
0 g OFFSET Each axis
0 g Output4 XOUT, YOUT 150 +150 mg
ZOUT 250 +250 mg
0 g Offset vs. Temperature3
Normal Operation XOUT, YOUT ±0.5 mg/°C
ZOUT ±0.6 mg/°C
Low Noise Mode and Ultralow Noise
Mode
XOUT, YOUT, ZOUT ±0.35 mg/°C
NOISE PERFORMANCE
Noise Density
Normal Operation XOUT, YOUT 550 µg/√Hz
ZOUT 920 µg/√Hz
Low Noise Mode XOUT, YOUT 400 µg/√Hz
ZOUT 550 µg/√Hz
Ultralow Noise Mode XOUT, YOUT 250 µg/√Hz
ZOUT 350 µg/√Hz
V
S
= 3.5 V; X
OUT
, Y
OUT
µ
g
/√Hz
VS = 3.5 V; ZOUT 250 µg/√Hz
BANDWIDTH
Low Pass (Antialiasing) Filter, −3 dB
Corner
HALF_BW = 0 ODR/2 Hz
HALF_BW = 1 ODR/4 Hz
Output Data Rate (ODR) User selectable in 8 steps 12.5 400 Hz
SELF TEST
Output Change5 XOUT 230 550 870 mg
YOUT 870 550 230 mg
ZOUT 270 535 800 mg
POWER SUPPLY
Operating Voltage Range (VS) 1.6 2.0 3.5 V
I/O Voltage Range (VDD I/O) 1.6 2.0 VS V
Data Sheet ADXL362
Rev. F | Page 5 of 43
Parameter Test Conditions/Comments Min Typ Max Unit
Supply Current
Measurement Mode 100 Hz ODR (50 Hz bandwidth)6
Normal Operation 1.8 µA
Low Noise Mode 3.3 µA
Ultralow Noise Mode
µA
Wake-Up Mode 0.27 µA
Standby 0.01 µA
Power Supply Rejection Ratio (PSRR) CS = 1.0 µF, RS = 100 Ω, CIO = 1.1 µF, input
is 100 mV sine wave on VS
Input Frequency 100 Hz to 1 kHz 13 dB
Input Frequency 1 kHz to 250 kHz
dB
Turn-On Time 100 Hz ODR (50 Hz bandwidth)
Power-Up to Standby 5 ms
Measurement Mode Instruction to
Valid Data
4/ODR
TEMPERATURE SENSOR
Bias Average @ 25°C 350 LSB
Standard Deviation 290 LSB
Sensitivity Average
°C/LSB
Standard Deviation 0.0025 °C/LSB
Sensitivity Repeatability ±0.5 °C
Resolution 12 Bits
ENVIRONMENTAL
Operating Temperature Range 40 +85 °C
1 All minimum and maximum specifications are guaranteed. Typical specifications may not be guaranteed.
2 Cross axis sensitivity is defined as coupling between any two axes.
3 −40°C to +25°C or +25°C to +85°C.
4 Different processes may cause the typical offset to vary from lot to lot. For operation at different voltages, see offset performance across voltage in Figure 49.
5 Self test change is defined as the output change in g when self test is asserted. Different supplies cause different self test changes. These limits apply to the specific
test conditions stated in Table 1. For variations over the full Vs supply range, see Table 22.
6 Refer to Figure 30 for current consumption at other bandwidth settings.
ADXL362 Data Sheet
Rev. F | Page 6 of 43
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
Acceleration (Any Axis, Unpowered) 5000 g
Acceleration (Any Axis, Powered)
5000
g
VS 0.3 V to +3.6 V
VDD I/O 0.3 V to +3.6 V
All Other Pins 0.3 V to VS
Output Short-Circuit Duration
(Any Pin to Ground)
Indefinite
ESD
2000 V (HBM)
Short Term Maximum Temperature
Four Hours 150°C
One Minute 260°C
Temperature Range (Powered) −50°C to +150°C
Temperature Range (Storage) 50°C to +150°C
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
THERMAL RESISTANCE
Table 3. Package Characteristics
Package Type θJA θJC Device Weight
16-Terminal LGA 150°C/W 85°C/W 18 mg
PACKAGE INFORMATION
Figure 2 and Table 4 provide details about the package branding
for the ADXL362. For a complete listing of product availability,
see the Ordering Guide section.
• 3 6 2 B
# y w w
v v v v
10776-002
Figure 2. Product Information on Package (Top View)
Table 4. Package Branding Information
Branding Key Field Description
362B Pin 1 indicator and device identifier
#yww Pb-free designator (#) and date code
vvvv Factory lot code
RECOMMENDED SOLDERING PROFILE
Figure 3 and Table 5 provide details about the recommended
soldering profile.
t
P
t
L
t25°C TO PEAK
t
S
PREHEAT
CRITICAL ZONE
T
L
TO T
P
TEMPERATURE
TIME
RAMP-DOWN
RAMP-UP
T
SMIN
T
SMAX
T
P
T
L
10776-003
Figure 3. Recommended Soldering Profile
Table 5. Recommended Soldering Profile
Profile Feature
Condition
Sn63/Pb37 Pb-Free
Average Ramp Rate (TL to TP) 3°C/sec max C/sec max
Preheat
Minimum Temperature (T
SMIN
)
100°C
150°C
Maximum Temperature (TSMAX) 150°C 200°C
Time (TSMIN to TSMAX)(tS) 60 sec to 120 sec 60 sec to 180 sec
TSMAX to TL Ramp-Up Rate 3°C/sec max 3°C/sec max
Time Maintained Above
Liquidous (TL)
Liquidous Temperature (TL) 183°C 217°C
Time (tL) 60 sec to 150 sec 60 sec to 150 sec
Peak Temperature (TP) 240 + 0/−5°C 260 + 0/−5°C
Time Within 5°C of Actual
Peak Temperature (tP)
10 sec to 30 sec 20 sec to 40 sec
Ramp-Down Rate 6°C/sec max 6°C/sec max
Time 25°C to Peak
Temperature
6 minutes max 8 minutes max
ESD CAUTION
Data Sheet ADXL362
Rev. F | Page 7 of 43
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
NC
GND
V
S
MISO
MOSI
CS
NOTES
1. NC = NO CONNECT. THIS PIN IS NOT
INTERNALLY CONNECTED.
NC
V
DDI/O
RESERVED
SCLK
RESERVED
GND
GND
INT1
RESERVED
INT2
ADXL362
TOP VIEW
(Not to Scale)
1
2
3
4
5
13
12
11
10
9
678
16 15 14
10776-004
Figure 4. Pin Configuration (Top View)
Table 6. Pin Function Descriptions
Pin No. Mnemonic Description
1 VDD I/O Supply Voltage for Digital I/O.
2 NC No Connect. Not internally connected.
3 Reserved Reserved. Can be left unconnected or connected to GND.
4 SCLK SPI Communications Clock.
5
Reserved
Reserved. Can be left unconnected or connected to GND.
6 MOSI Master Output, Slave Input. SPI serial data input.
7 MISO Master Input, Slave Output. SPI serial data output.
8 CS SPI Chip Select, Active Low. Must be low during SPI communications.
9 INT2 Interrupt 2 Output. INT2 also serves as an input for synchronized sampling.
10 Reserved Reserved. Can be left unconnected, or connected to GND.
11 INT1 Interrupt 1 Output. INT1 also serves as an input for external clocking.
12 GND Ground. This pin must be grounded.
13 GND Ground. This pin must be grounded.
14 VS Supply Voltage.
15 NC No Connect. Not internally connected.
16
GND
Ground. This pin must be grounded.
ADXL362 Data Sheet
Rev. F | Page 8 of 43
TYPICAL PERFORMANCE CHARACTERISTICS
25
20
15
10
5
0
PERCENT OF POPULATION (%)
–80–70–60–50–40–30–20–10 010 20 30 40 50 60 70 80
ZERO g OFFSET (mg)
10776-005
Figure 5. X-Axis Zero g Offset at 25°C, VS = 2 V
PERCENT OF POPULATION (%)
–80–70–60–50–40–30–20–10 010 20 30 40 50 60 70 80
ZERO g OFFSET (mg)
0
5
10
15
20
25
30
10776-006
Figure 6. Y-Axis Zero g Offset at 25°C, VS = 2 V
ZERO g OFFSET (mg)
0
2
4
6
8
10
12
14
16
18
20
–170 –140 110 –80 –50 –20 10 40 70 100
PERCENT OF POPULATION (%)
10776-007
Figure 7. Z-Axis Zero g Offset at 25°C, VS = 2 V
40
35
30
25
20
15
10
5
0
PERCENTAGE OF POPULATION (%)
SENSITIVITY (mg/LSB)
930 950 970 990 1010 1030 1050 1070 1090 1110 1130
10776-008
Figure 8. X-Axis Sensitivity at 25°C, VS = 2 V, ±2 g Range
50
45
40
35
30
25
20
15
10
5
0
PERCENTAGE OF POPULATION (%)
SENSITIVITY (mg/LSB)
930 950 970 990 1010 1030 1050 1070 1090 1110 1130
10776-009
Figure 9. Y-Axis Sensitivity at 25°C, VS = 2 V, ±2 g Range
PERCENTAGE OF POPULATION (%)
SENSITIVITY (mg/LSB)
0
2
4
6
8
10
12
14
16
18
975 990 1005 1020 1035 1050 1065 1080 1095 1110 1125
10776-010
Figure 10. Z-Axis Sensitivity at 25°C, VS = 2 V, ±2 g Range
Data Sheet ADXL362
Rev. F | Page 9 of 43
0
5
10
15
20
25
–1.0 –0.8 –0.6 –0.4 –0.2 00.2 0.4 0.6 0.8 1.0
PERCENT OF POPULATION (%)
ZERO g OFFSET TEMPERATURE COEFFICIENT (mg/°C)
10776-011
Figure 11. X-Axis Zero g Offset Temperature Coefficient, VS = 2 V
–1.0 –0.8 –0.6 –0.4 –0.2 00.2 0.4 0.6 0.8 1.0
0
5
10
15
20
25
30
35
PERCENT OF POPULATION (%)
ZERO g OFFSET TEMPERATURE COEFFICIENT (mgC)
10776-012
Figure 12. Y-Axis Zero g Offset Temperature Coefficient, VS = 2 V
0
5
10
15
20
25
–0.5 –0.3 –0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9
PERCENT OF POPULATION (%)
ZERO g OFFSET TEMPERATURE COEFFICIENT (mg/°C)
10776-013
Figure 13. Z-Axis Zero g Offset Temperature Coefficient, VS = 2 V
–100
–50
0
50
100
150
–60 –40 –20 020 40 60 80 100
OUTPUT (mg)
TEMPERATUREC)
10776-014
Figure 14. X-Axis Zero g Offset vs. Temperature
16 Parts Soldered to PCB, ODR = 100 Hz, VS = 2 V
–100
–50
0
50
100
150
60 40 20 020 40 60 80 100
OUTPUT (mg)
TEMPERATURE (°C)
10776-015
Figure 15. Y-Axis Zero g Offset vs. Temperature
16 Parts Soldered to PCB, ODR = 100 Hz, VS = 2 V
–100
–50
0
50
100
150
–60 –40 –20 020 40 60 80 100
OUTPUT (mg)
TEMPERATURE (°C)
10776-016
Figure 16. Z-Axis Zero g Offset vs. Temperature
16 Parts Soldered to PCB, ODR = 100 Hz, VS = 2 V
ADXL362 Data Sheet
Rev. F | Page 10 of 43
–10
–8
–6
–4
–2
0
2
4
6
8
10
–60 –40 –20 020 40 60 80 100
SENSITIVITY DEVIATION FROM 25°C (%)
TEMPERATURE (°C)
10776-017
Figure 17. X-Axis Sensitivity Deviation from 25°C vs. Temperature
16 Parts Soldered to PCB, ODR = 100 Hz, VS = 2 V
TEMPERATURE (°C)
–10
–8
–6
–4
–2
0
2
4
6
8
10
60
40
20 020 40 60 80 100
SENSITIVITY DEVIATION FROM 25°C (%)
10776-018
Figure 18. Y-Axis Sensitivity Deviation from 25°C vs. Temperature
16 Parts Soldered to PCB, ODR = 100 Hz, VS = 2 V
–10
–8
–6
–4
–2
0
2
4
6
8
10
–60 –40 –20 020 40 60 80 100
SENSITIVITY DEVIATION FROM 25°C (%)
TEMPERATURE (°C)
10776-019
Figure 19. Z-Axis Sensitivity Deviation from 25°C vs. Temperature
16 Parts Soldered to PCB, ODR = 100 Hz, VS = 2 V
0
5
10
15
20
25
30
35
40
450 475 500 525 550 575 600 625 650 675 700
PERCENT OF POPULATION (%)
SELF TEST DELTA (mg)
10776-020
Figure 20. X-Axis Self Test Response at 25°C, VS = 2 V
0
5
10
15
20
25
30
35
40
–700 –675 –650 –625 –600 –575 –550 –525 –500 –475 –450
PERCENT OF POPULATION (%)
SELF TEST DELTA (mg)
10776-021
Figure 21. Y-Axis Self Test Response at 25°C, VS = 2 V
0
5
10
15
20
25
30
35
40
350 375 400 425 450 475 500 525 550 575 600 625 650
PERCENT OF POPULATION (%)
SELF TEST DELTA (mg)
10776-022
Figure 22. Z-Axis Self Test Response at 25°C, VS = 2 V
Data Sheet ADXL362
Rev. F | Page 11 of 43
0
5
10
15
20
25
30
35
1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.05
CURRENT CONSUMPTION (µA)
PERCENT OF POPULATION (%)
10776-023
Figure 23. Current Consumption at 25°C, Normal Mode,
ODR = 100 Hz, VS = 2 V
PERCENT OF POPULATION (%)
0
5
10
15
20
25
30
2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8
CURRENT CONSUMPTION (µA)
10776-024
Figure 24. Current Consumption at 25°C, Low Noise Mode,
ODR = 100 Hz, VS = 2 V
PERCENT OF POPULATION (%)
0
5
10
15
20
25
30
35
8 9 10 1112 13 14 15 16
CURRENT CONSUMPTION (µA)
10776-025
Figure 25. Current Consumption at 25°C, Ultralow Noise Mode,
ODR = 100 Hz, VS = 2 V
PERCENT OF POPULATION (%)
0
10
20
30
40
50
60
70
50 100 150 200 250 300 350 400
CURRENT CONSUMPTION (nA)
10776-026
Figure 26. Current Consumption at 25°C, Wake-Up Mode, VS = 2 V
0
2
4
6
8
10
12
–200 0200 400 600 800 1000
PERCENT OF POPULATION (%)
TEMPERATURE SENSOR BIAS AT 25°C (LSB)
10776-027
Figure 27. Temperature Sensor Response at 25°C, VS = 2 V
0
5
10
15
20
25
30
35
40
14.4 14.6 14.8 15.0 15.2 15.4 15.6 15.8 16.0 16.2 16.4 16.6 16.8
PERCENT OF POPULATION (%)
TEMPERATURE SENSOR SCALE FACTOR (LSB/°C)
10776-028
Figure 28. Temperature Sensor Scale Factor, VS = 2 V
ADXL362 Data Sheet
Rev. F | Page 12 of 43
0
5
10
15
20
25
30
–20 –16 –12 –8 –4 04 8 12 16 20
PERCENT OF POPULATION (%)
CLOCK FREQUENCY DEVIATION FROM IDEAL (%)
10776-029
Figure 29. Clock Frequency Deviation from Ideal at 25°C, VS = 2 V
Data Sheet ADXL362
Rev. F | Page 13 of 43
THEORY OF OPERATION
The ADXL362 is a complete 3-axis acceleration measurement
system that operates at extremely low power consumption levels. It
measures both dynamic acceleration, resulting from motion or
shock, and static acceleration, such as tilt. Acceleration is reported
digitally and the device communicates via the SPI protocol. Built-
in digital logic enables autonomous operation and implements
functionality that enhances system level power savings.
MECHANICAL DEVICE OPERATION
The moving component of the sensor is a polysilicon surface-
micromachined structure that is built on top of a silicon wafer.
Polysilicon springs suspend the structure over the surface of the
wafer and provide a resistance against acceleration forces.
Deflection of the structure is measured using differential
capacitors that consist of independent fixed plates and plates
attached to the moving mass. Acceleration deflects the structure
and unbalances the differential capacitor, resulting in a sensor
output whose amplitude is proportional to acceleration. Phase
sensitive demodulation determines the magnitude and polarity
of the acceleration.
OPERATING MODES
The ADXL362 has two operating modes: measurement mode for
continuous, wide bandwidth sensing; and wake-up mode for
limited bandwidth activity detection. In addition, measurement can
be suspended altogether by placing the device in standby.
Measurement Mode
Measurement mode is the normal operating mode of the
ADXL362. In this mode, acceleration data is read continuously
and the accelerometer consumes less than 3 µA (typical) across
its entire range of output data rates of up to 400 Hz using a 2.0 V
supply. All features described in this datasheet are available
when operating the ADXL362 in this mode.
The ability to continuously output data from the minimum
12.5 Hz to the maximum 400 Hz data rate while still delivering
less than 3 µA (typical) of current consumption is what defines
the ADXL362 as an ultralow power accelerometer. Other accel-
erometers derive low current by using a specific low power mode
that power cycles acceleration sensing. The result is a small
effective bandwidth in the low power modes and undersampling
of input data; therefore, unwanted aliasing can occur. Under-
sampling and aliasing do not occur with the ADXL362 because
it continuously samples the full bandwidth of its sensor at all
data rates.
Wake-Up Mode
Wake-up mode is ideal for simple detection of the presence or
absence of motion at extremely low power consumption (270 nA
at a 2.0 V supply voltage). Wake-up mode is useful particularly for
implementation of a motion activated on/off switch, allowing the
rest of the system to be powered down until activity is detected.
Wake-up mode reduces current consumption to a very low level
by measuring acceleration only about six times per second to
determine whether motion is present. If motion is detected, the
accelerometer can respond autonomously in the following ways:
Switch into full bandwidth measurement mode
Signal an interrupt to a microcontroller
Wake up downstream circuitry, depending on the
configuration
In wake-up mode, all accelerometer features are available
with the exception of the activity timer. All registers can be
accessed, and real-time data can be read and/or stored in
the FIFO.
Standby
Placing the ADXL362 in standby suspends measurement and
reduces current consumption to 10 nA (typical). Pending
interrupts and data are preserved and no new interrupts are
generated.
The ADXL362 powers up in standby with all sensor functions
turned off.
SELECTABLE MEASUREMENT RANGES
The ADXL362 has selectable measurement ranges of ±2 g, ±4 g,
and ±8 g. Acceleration samples are always converted by a 12-bit
ADC; therefore, sensitivity scales with g range. Ranges and
corresponding sensitivity values are listed in Table 1. Data can
temporarily not represent maximum gees while overranging
but no damage is caused to the accelerometer when acceleration
exceeds the corresponding range maximum. Table 2 lists the
absolute maximum ratings for acceleration, indicating the
acceleration level that can cause permanent damage to the device.
SELECTABLE OUTPUT DATA RATES
The ADXL362 can report acceleration data at various data rates
ranging from 12.5 Hz to 400 Hz. The internal low-pass filter pole is
automatically set to ¼ or ½ the selected ODR (based on the
HALF_BW setting) to ensure the Nyquist sampling criterion is
met and no aliasing occurs.
ADXL362 Data Sheet
Rev. F | Page 14 of 43
Current consumption varies somewhat with output data rate as
shown in Figure 30, remaining below 5.0 µA over the entire
range of data rates and operating voltages.
6
5
4
3
2
1
0
CURRENT CONSUMPTION (µA)
OUTPUT DATA RATE (Hz)
0100 200 300 400
V
S
= 1.6V
V
S
= 2.0V
V
S
= 2.5V
V
S
= 3.0V
V
S
= 3.5V
10776-030
Figure 30. Current Consumption vs. Output Data Rate at Several
Supply Voltages
Antialiasing
The analog-to-digital converter (ADC) of the ADXL362 samples
at the (user selected) output data rate. In the absence of anti-
aliasing filtering, it aliases any input signals whose frequency is
more than half the data rate. To mitigate this, a two-pole low-
pass filter is provided at the input of the ADC.
The user can set this antialiasing filter to a bandwidth that is at ½
the data rate or ¼ the data rate. Setting the antialiasing filter pole
to ½ of the output data rate provides less aggressive antialiasing
filtering, but maximizes bandwidth and is adequate for most
applications. Setting the pole to ¼ of the data rate reduces
bandwidth for a given data rate, but provides more aggressive
antialiasing.
The antialiasing filter of the ADXL362 defaults to the more
conservative setting, where bandwidth is set to one-fourth the
output data rate.
POWER/NOISE TRADEOFF
The ADXL362 offers a few options for decreasing noise at the
expense of only a small increase in current consumption.
The noise performance of the ADXL362 in normal operation,
typically 7 LSB rms at 100 Hz bandwidth, is adequate for most
applications, depending upon bandwidth and the desired reso-
lution. For cases where lower noise is needed, the ADXL362
provides two lower noise operating modes that trade reduced
noise for a somewhat higher current consumption.
Table 7 lists the current consumption and noise densities obtained
for normal operation and the two lower noise modes at a typical
2.0 V supply.
Table 7. Noise and Current Consumption: Normal Operation,
Low Noise Mode, and Ultralow Noise Mode at VS = 2.0 V,
ODR = 100 Hz
Mode
Noise
g/√Hz)
Typical
Current
Consumption (µA)
Typical
Normal Operation 550 1.8
Low Noise 400 3.3
Ultralow Noise 250 13
Operating the ADXL362 at a higher supply voltage also decreases
noise. Table 8 lists the current consumption and noise densities
obtained for normal operation and the two lower noise modes
at the highest recommended supply, 3.3 V.
Table 8. Noise and Current Consumption: Normal Operation,
Low Noise Mode, and Ultralow Noise Mode at VS = 3.3 V,
ODR = 100 Hz
Mode
Noise
g/√Hz)
Typical
Current
Consumption (µA)
Typical
Normal Operation 380 2.7
Low Noise
280
4.5
Ultralow Noise 175 15
Data Sheet ADXL362
Rev. F | Page 15 of 43
POWER SAVINGS FEATURES
Designed for the most power conscious applications, the ADXL362
includes several features (as described in this section) for enabling
power savings at the system level, as well as at the device level.
ULTRALOW POWER CONSUMPTION IN ALL
MODES
At the device level, the most obvious power saving feature of the
ADXL362 is its ultralow current consumption in all configurations.
The ADXL362 consumes between 1.1 µA (typical) and 5 µA
(typical) across all data rates up to 400 Hz and all supply voltages
up to 3.5 V (see Figure 30). An even lower power, 270 nA (typical)
motion triggered wake-up mode is provided for simple motion
detection applications that require a power consumption lower
than 1 µA.
At these current levels, the accelerometer consumes less power
in full operation than the standby currents of many other system
components, and is, therefore, optimal for applications that require
continuous acceleration monitoring and very long battery life.
Because the accelerometer is always on, it can act as a motion
activation switch. The accelerometer signals to the rest of the
system when to turn on, thereby managing power at the
system level.
As important as its low operating current, the 10 nA (typical)
standby current of the ADXL362 contributes to a much longer
battery life in applications that spend most of their time in a
sleep state and wake up via an external trigger.
MOTION DETECTION
The ADXL362 features built-in logic that detects activity
(presence of acceleration above a threshold) and inactivity (lack
of acceleration above a threshold). Activity and inactivity events
can be used as triggers to manage the accelerometer mode of
operation, trigger an interrupt to a host processor, and/or
autonomously drive a motion switch.
Detection of an activity or inactivity event is indicated in the
status register and can be configured to generate an interrupt.
In addition, the activity status of the device, that is, whether it is
moving or stationary, is indicated by the AWAKE bit, described
in the Using the AWA KE Bit section.
Activity and inactivity detection can be used when the accel-
erometer is in either measurement mode or wake-up mode.
Activity Detection
An activity event is detected when acceleration remains above a
specified threshold for a specified time period.
Referenced and Absolute Configurations
Activity detection can be configured as referenced or absolute.
When using absolute activity detection, acceleration samples are
compared to a user set threshold to determine whether motion
is present. For example, if a threshold of 0.5 g is set and the
acceleration on the z-axis is 1 g for longer than the user defined
activity time, the activity status asserts.
In many applications, it is advantageous for activity detection to
be based not on an absolute threshold, but on a deviation from
a reference point or orientation. This is particularly useful because
it removes the effect on activity detection of the static 1 g imposed
by gravity. When an accelerometer is stationary, its output can
reach 1 g, even when it is not moving. In absolute activity, when
the threshold is set to less than 1 g, activity is immediately detected
in this case.
In the referenced configuration, activity is detected when
acceleration samples are at least a user set amount above an
internally defined reference for the user defined amount of time,
as described in Equation 1.
ABS(AccelerationReference) > Threshold (1)
Consequently, activity is detected only when the acceleration
has deviated sufficiently from the initial orientation. The
reference for activity detection is calculated when activity
detection is engaged in the following scenarios:
When the activity function is turned on and measurement
mode is engaged;
If link mode is enabled: when inactivity is detected and
activity detection begins; or
If link mode is not enabled: when activity is detected and
activity detection repeats.
The referenced configuration results in a very sensitive activity
detection that detects even the most subtle motion events.
Fewer False Positives
Ideally, the intent of activity detection is to wake up a system only
when motion is intentional, ignoring noise or small, unintentional
movements. In addition to being sensitive to subtle motion events,
the ADXL362 activity detection algorithm is designed to be
robust in filtering out undesired triggers.
The ADXL362 activity detection functionality includes a timer
to filter out unwanted motion and ensure that only sustained
motion is recognized as activity. The duration of this timer, as
well as the acceleration threshold, are user adjustable from one
sample (that is, no timer) to up to 20 seconds of motion.
Note that the activity timer is operational in measurement mode
only. In wake-up mode, one-sample activity detection is used.
Inactivity Detection
An inactivity event is detected when acceleration remains below
a specified threshold for a specified time. Inactivity detection is
also configurable as referenced or absolute.
When using absolute inactivity detection, acceleration samples
are compared to a user set threshold for the user set time to
determine the absence of motion. Inactivity is detected when
enough consecutive samples are all below the threshold. The
absolute configuration of inactivity must be used for
implementing free fall detection.
ADXL362 Data Sheet
Rev. F | Page 16 of 43
When using referenced inactivity detection, inactivity is detected
when acceleration samples are within a user specified amount
of an internally defined reference (as described by Equation 2)
for a user defined amount of time.
ABS(AccelerationReference) < Threshold (2)
Referenced inactivity, like referenced activity, is particularly
useful for eliminating the effects of the static acceleration due to
gravity. With absolute inactivity, if the inactivity threshold is set
lower than 1 g, a device resting motionless may never detect
inactivity. With referenced inactivity, the same device under the
same configuration detects inactivity.
The inactivity timer can be set to anywhere from 2.5 ms (a single
sample at 400 Hz ODR) to almost 90 minutes (65,535 samples
at 12.5 Hz ODR) of inactivity. A requirement for inactivity detec-
tion is that for whatever period of time the inactivity timer has
been configured, the accelerometer detects inactivity only when
it has been stationary for that amount of time.
For example, if the accelerometer has been configured for
90 minutes, the accelerometer detects inactivity when it has
been stationary for 90 minutes. The wide range of timer settings
means that in applications where power conservation is critical,
the system can be put to sleep after very short periods of inactivity.
In applications where continuous operation is critical, the system
stays on for as long as any motion is present.
Linking Activity and Inactivity Detection
The activity and inactivity detection functions can be used
concurrently and processed manually by a host processor, or
they can be configured to interact in several other ways, as
follows.
Default Mode
The user must enable the activity and inactivity functions because
these functions are not automatically enabled by default. After
the user enables the activity and inactivity functions, the ADXL362
exhibits the following behavior when it enters default mode: Both
activity and inactivity detection remain enabled and all interrupts
must be serviced by a host processor; that is, a processor must
read each interrupt before it is cleared and can be used again.
Default mode operation is illustrated in the flowchart in Figure 31.
Linked Mode
In linked mode, activity and inactivity detection are linked to
each other such that only one of the functions is enabled at any
given time. As soon as activity is detected, the device is assumed
to be moving (or awake) and stops looking for activity; rather,
inactivity is expected as the next event. Therefore, only inactivity
detection operates.
Similarly, when inactivity is detected, the device is assumed to
be stationary (or asleep). Thus, activity is expected as the next
event; therefore, only activity detection operates.
WAIT FOR
ACTIVITY
EVENT
ACTIVITY
INTERRUPT
TRIGGERS
NOTES
1. THE AWAKE BIT DEFAULTS TO 1 WHEN ACTIVITY AND INACTIVITY
ARE NOT LINKED.
WAIT FOR
INACTIVITY
EVENT
INACTIVITY
INTERRUPT
TRIGGERS
WAIT FOR
PROCESSOR TO
CLEAR INTERRUPT
WAIT FOR
PROCESSOR TO
CLEAR INTERRUPT
AWAKE = 1
AWAKE = 1
10776-131
Figure 31. Flowchart Illustrating Activity and Inactivity Operation in Default Mode
In linked mode, each interrupt must be serviced by a host
processor before the next interrupt is enabled.
Linked mode operation is illustrated in the flowchart in Figure 32.
WAIT FOR
ACTIVITY
EVENT
ACTIVITY
INTERRUPT
WAIT FOR
INACTIVITY
EVENT
INACTIVITY
INTERRUPT
AWAKE = 0
AWAKE = 1
WAIT FOR
PROCESSOR TO
CLEAR INTERRUP
WAIT FOR
PROCESSOR TO
CLEAR INTERRUPT
10776-132
Figure 32. Flowchart Illustrating Activity and Inactivity Operation in Linked Mode
Loop Mode
In loop mode, motion detection operates as described in the
Linked Mode section, but interrupts do not need to be serviced
by a host processor. This configuration simplifies the implemen-
tation of commonly used motion detection and enhances power
savings by reducing the amount of power used in bus communi-
cation.
Loop mode operation is illustrated in the flowchart in Figure 33.
WAIT FOR
ACTIVITY
EVENT
WAIT FOR
INACTIVITY
EVENT
AWAKE = 0
A
WAKE = 1
10776-133
Figure 33. Flowchart Illustrating Activity and Inactivity Operation in Loop Mode
Autosleep
When in linked or loop mode, enabling autosleep causes the
device to enter wake-up mode autonomously (see the Wake-Up
Mode section) when inactivity is detected, and to reenter
measurement mode when activity is detected.
The autosleep configuration is active only if linked or loop modes
are enabled. In the default mode, the autosleep setting is ignored.
Data Sheet ADXL362
Rev. F | Page 17 of 43
Using the AWAKE Bit
The AWAKE bit is a status bit that indicates whether the ADXL362
is awake or asleep. The device is awake when it has experienced
an activity condition, and it is asleep when it has experienced an
inactivity condition.
The awake signal can be mapped to the INT1 or INT2 pin,
allowing the pin to serve as a status output to connect or dis-
connect power to downstream circuitry based on the awake
status of the accelerometer. Used in conjunction with loop
mode, this configuration implements a trivial, autonomous
motion activated switch, as shown in Figure 43.
If the turn-on time of downstream circuitry can be tolerated,
this motion switch configuration can save significant system
level power by eliminating the standby current consumption of
the remainder of the application. This standby current can often
exceed the full operating current of the ADXL362.
FIFO
The ADXL362 includes a deep 512-sample first in, first out (FIFO)
buffer. The FIFO provides benefits primarily in two ways, as
follows.
System Level Power Savings
Appropriate use of the FIFO enables system level power savings
by enabling the host processor to sleep for extended periods of
time while the accelerometer autonomously collects data. Alter-
natively, using the FIFO to collect data can unburden the host
while it tends to other tasks.
Data Recording/Event Context
The FIFO can be used in a triggered mode to record all data
leading up to an activity detection event, thereby providing con-
text for the event. In the case of a system that identifies impact
events, for example, the accelerometer can keep the entire system
off while it stores acceleration data in its FIFO and looks for an
activity event. When the impact event occurs, data that was
collected prior to the event is frozen in the FIFO. The accel-
erometer can then wake the rest of the system and transfer this
data to the host processor, thereby providing context for the
impact event.
Generally, the more context available, the more intelligent
decisions a system can achieve, making a deep FIFO especially
useful. The ADXL362 FIFO can store up to more than 13 seconds
of data, providing a clear picture of events prior to an activity
trigger.
All FIFO modes of operation, as well as the structure of the FIFO
and instructions for retrieving data from it, are described in further
detail in the FIFO Modes section of this data sheet.
COMMUNICATIONS
SPI Instructions
The digital interface of the ADXL362 is implemented with
system level power savings in mind. The following features
enhance power savings:
Burst reads and writes reduce the number of SPI
communication cycles required to configure the device
and retrieve data.
Concurrent operation of activity and inactivity detection
enables “set it and forget it operation. Loop mode further
reduces communications power by enabling the clearing of
interrupts without processor intervention.
The FIFO is implemented such that consecutive samples
can be read continuously via a multibyte read of unlimited
length; thus, one read FIFO instruction can clear the entire
contents of the FIFO. In many other accelerometers, each
read instruction retrieves a single sample only. In addition, the
ADXL362 FIFO construction allows the use of direct memory
access (DMA) to read the FIFO contents.
Bus Keepers
The ADXL362 includes bus keepers on all pins that can be
configured as digital inputs: MOSI, SCLK, CS, INT1, and INT2.
Bus keepers prevent tristate bus lines from floating when nothing
is driving them, thus preventing through current in any gate
inputs that are on the bus.
MSB Registers
Acceleration and temperature measurements are converted to
12-bit values and transmitted via SPI using two registers per
measurement. To read a full sample set of 3-axis acceleration
data, six registers must be read.
Many applications do not require the accuracy that 12-bit data
provides and prefer, instead, to save system level power. The MSB
registers XDATA, YDATA, and ZDATA enable this tradeoff.
These registers contain the eight MSBs of the x-, y-, and z-axis
acceleration data; reading them effectively provides 8-bit accel-
eration values. Importantly, only three (consecutive) registers must
be read to retrieve a full data set, significantly reducing the time
during which the SPI bus is active and drawing current.
12-bit and 8-bit data are available simultaneously so that both
data formats can be used in a single application, depending on
the needs of the application at a given time. For example, the pro-
cessor can read 12-bit data when higher resolution is required, and
switch to 8-bit data (simply by reading a different set of registers)
when application requirements change.
ADXL362 Data Sheet
Rev. F | Page 18 of 43
ADDITIONAL FEATURES
FREE FALL DETECTION
Many digital output accelerometers include a built-in free fall
detection feature. In the ADXL362, this function can be imple-
mented using the inactivity interrupt. Refer to the Applications
Information section for more details, including suggested
threshold and timing values.
EXTERNAL CLOCK
The ADXL362 has a built-in 51.2 kHz (typical) clock that, by
default, serves as the time base for internal operations.
ODR and bandwidth scale proportionally with the clock. The
ADXL362 provides a discrete number of options for ODR, such
as 100 Hz, 50 Hz, 25 Hz, and so forth, in factors of 2, (see the
Filter Control Register section for a complete listing). To achieve
data rates other than those provided, an external clock can be
used at the appropriate clock frequency. The output data rate
scales with the clock frequency, as shown in Equation 3.
kHz2.51
f
ODRODR
SELECTEDACTUAL
×=
(3)
For example, to achieve an 80 Hz ODR, select the 100 Hz ODR
setting and provide a clock frequency that is 80% of nominal, or
41.0 kHz.
The ADXL362 can operate with external clock frequencies
ranging from the nominal 51.2 kHz down to 25.6 kHz to allow
the user to achieve any desired output data rate.
Alternatively, an external clock can improve clock frequency
accuracy. The distribution of clock frequencies among a sampling
of >1000 parts has a standard deviation of approximately 3%. To
achieve tighter tolerances, a more accurate clock can be
provided externally.
Bandwidth automatically scales to ½ or ¼ of the ODR (based
on the HALF_BW setting), and this ratio is preserved, regardless
of clock frequency. Power consumption also scales with clock
frequency: higher clock rates increase power consumption.
Figure 34 shows how power consumption varies with clock rate.
3.0
2.5
2.0
1.5
1.0
0.5
0
CURRENT CONSUMPTION (µA)
EXTERNAL CLOCK FREQUENCY (kHz)
43 44 45 46 47 48 49 50 51 52
V
S
= 1.6V
V
S
= 2.0V
V
S
= 3.5V
10776-031
Figure 34. Current Consumption vs. External Clock Rate
SYNCHRONIZED DATA SAMPLING
For applications that require a precisely timed acceleration
measurement, the ADXL362 features an option to synchronize
acceleration sampling to an external trigger.
SELF TEST
The ADXL362 incorporates a self test feature that effectively
tests its mechanical and electronic systems simultaneously.
When the self test function is invoked, an electrostatic force is
applied to the mechanical sensor. This electrostatic force moves the
mechanical sensing element in the same manner as acceleration,
and it is additive to the acceleration experienced by the device.
This added electrostatic force results in an output change on all
three axes.
USER REGISTER PROTECTION
The ADXL362 includes user register protection for single event
upsets (SEUs). An SEU is a change of state caused by ions or
electromagnetic radiation striking a sensitive node in a micro-
electronic device. The state change is a result of the free charge
created by ionization in or close to an important node of a logic
element (for example, a memory bit). The SEU, itself, is not con-
sidered permanently damaging to transistor or circuit functionality,
but it can create erroneous register values. The ADXL362 registers
that are protected from SEU are Register 0x20 to Register 0x2E.
SEU protection is implemented via a 99-bit error correcting
(Hamming-type) code that detects both single- and double-bit
errors. The check bits are recomputed any time a write to any of
the protected registers occurs. At any time, if the stored version
of the check bits is not in agreement with the current check bit
calculation, the ERR_USER_REGS status bit is set.
The SEU bit in the status register is set on power-up prior to
device configuration; it clears upon the first register write to
that device.
TEMPERATURE SENSOR
The ADXL362 includes an integrated temperature sensor that
can monitor internal system temperature or improve the tempera-
ture stability of the device via calibration. For example, acceleration
outputs vary with temperature at a rate of ±0.5 mgC (typical),
but the relationship to temperature is repeatable and can be
calibrated.
To use the temperature sensor to monitor absolute temperature,
it is recommended that its initial bias (its output at some known
temperature) is measured and calibrated.
Data Sheet ADXL362
Rev. F | Page 19 of 43
SERIAL COMMUNICATIONS
The ADXL362 communicates via a 4-wire SPI and operates as a
slave. Ignore data that is transmitted from the ADXL362 to the
master device during writes to the ADXL362.
As shown in Figure 36 to Figure 40, the MISO pin is in a high
impedance state, held by a bus keeper, except when the ADXL362
is sending read data (to conserve bus power).
Wire the ADXL362 for SPI communication as shown in the
connection diagram in Figure 35. The recommended SPI clock
speeds are 1 MHz to 8 MHz, with 12 pF maximum loading.
The SPI timing scheme follows CPHA = CPOL = 0.
For correct operation of the device, the logic thresholds and
timing parameters in Table 9 and Table 10 must be met at all
times. Refer to Figure 41 and Figure 42 for visual diagrams of
the timing parameters.
ADXL362
PROCESSOR
CS
MOSI
MISO
SCLK
DOUT
DOUT
DIN
DOUT
10776-032
Figure 35. 4-Wire SPI Connection Diagram
SPI COMMANDS
The SPI port uses a multibyte structure wherein the first byte is
a command. The ADXL362 command set is
0x0A: write register
0x0B: read register
0x0D: read FIFO
Read and Write Register Commands
The command structure for the read register and write register
commands is as follows (see Figure 36 and Figure 37):
</CS down> <command byte (0x0A or 0x0B)> <address
byte> <data byte> <additional data bytes for multi-byte> …
</CS up>
The read and write register commands support multibyte
(burst) read/write access. The waveform diagrams for multi-
byte read and write commands are shown in Figure 38 and
Figure 39.
Read FIFO Command
Reading from the FIFO buffer is a command structure that does
not have an address.
</CS down> <command byte (0x0D)> <data byte> <data
byte> … </CS up>
It is recommended that an even number of bytes be read (using
a multibyte transaction) because each sample consists of two
bytes: 2 bits of axis information and 14 bits of data. If an odd
number of bytes is read, it is assumed that the desired data was
read; therefore, the second half of the last sample is discarded so
a read from the FIFO always starts on a properly aligned even-
byte boundary. Data is presented least significant byte first,
followed by the most significant byte.
MULTIBYTE TRANSFERS
Multibyte transfers, also known as burst transfers, are supported for
all SPI commands: register read, register write, and FIFO read
commands. It is recommended that data be read using multibyte
transfers to ensure that a concurrent and complete set of x-, y-,
and z-acceleration (and temperature, where applicable) data is
read.
The FIFO runs on the serial port clock during FIFO reads and
can sustain bursting at the SPI clock rate as long as the SPI clock
is 1 MHz or faster.
Register Read/Write Auto-Increment
A register read or write command begins with the address specified
in the command and auto-increments for each additional byte in
the transfer. To avoid address wrapping and side effects of reading
registers multiple times, the auto-increment halts at the invalid
Register Address 63 (0x3F).
INVALID ADDRESSES AND ADDRESS FOLDING
The ADXL362 has a 6-bit address bus, mapping only 64 registers in
the possible 256 register address space. The addresses do not fold to
repeat the registers at addresses above 64. Attempted access to
register addresses above 64 are mapped to the invalid register at
63 (0x3F) and have no functional effect.
Address 0x00 to Address 0x2E are for customer access, as
described in the register map. Address 0x2F to Address 0x3F are
reserved for factory use.
LATENCY RESTRICTIONS
Reading any of the data registers (0x08 to 0x0A or 0x0E to
0x15) clears the data ready interrupt. There can be as much as
an 80 μs delay from reading a register to the clearing of the data
ready interrupt.
Other register reads, register writes, and FIFO reads have no
latency restrictions.
INVALID COMMANDS
Commands other than 0x0A, 0x0B, and 0x0D have no effect.
The MISO output remains in a high impedance state, and the
bus keeper holds the MISO line at its last value.
ADXL362 Data Sheet
Rev. F | Page 20 of 43
0 1 5432 6 7 8 910 11 12 13 14 15 16 17 18 19 20 21 22 23
711010000 6 5 4 3 2 1 0
INSTRUCTION 8-BIT ADDRESS
DATA OUT
76543210
CS
SCLK
MOSI
MISO
7
7
7
6
6
6
6
6
6
6
7
7
7
0
0
0
0
0
0
1
0
1
0
0
0
7
5
5
5
8B
5
8
I
5
BI
5
BI
T
5
4
4
4
T AD
4
T
D
4
D
4
D
D
4
3
3
3
DRES
3
D
S
3
S
3
ES
S
3
2
2
2
S
2
S
2
2
2
1
1
1
1
1
0
0
0
0
0
0
0
1
1
1
10776-239
Figure 36. Register Read
0 1 5432 6 7 8 910 11 12 13 14 15 16 17 18 19 20 21 22 23
701010000 6 5 4 3 2 1 0
INSTRUCTION 8-BIT ADDRESS
76543210
DATA BYTE
CS
SCLK
MOSI
MISO
7
7
7
7
6
6
6
6
6
5
8
B
B
5
B
BI
5
5
5
5
4
IT A
A
BI
A
4
A
3
D
4
4
4
3
DDR
D
E
RE
2
3
RE
ES
3
3
3
2
SS
S
2
2
2
2
1
1
1
0
HIGH IMPEDANCE
10776-240
Figure 37. Register Write (Receive Instruction Only)
0 1 5432 6 7 8 910 11 12 13 14 15 16 17 18 19 20 21 22 23
7
1
010000
654321 0
INSTRUCTION 8-BIT ADDRESS
CS
SCLK
1
OUTPUT BYTE 1 OUTPUT BYTE n
MOSI
MISO
76543210 76543210
10776-241
Figure 38. Burst Read
HIGH IMPEDANCE
0 1 5432 6 7 8 910 11 12 13 14 15 16 17 18 19 20 21 22 23
7
1
010000
65 4 321 0
INSTRUCTION 8-BIT ADDRESS
CS
SCLK
0
MOSI
MISO
DATA BYTE 1 DATA BYTE n
7 6 5 4 3210 765 4 3 2 1 0
10776-242
Figure 39. Burst Write (Receive Instruction Only)
0 1 5432 6 7 8 910 11 12 13 14 15
10110000
INSTRUCTION
CS
SCLK
MOSI
MISO
7 6
5 4
3 2 1 0 7 65 4 3 2 1 0
7
7
7
6
6
6
5
5
5
4
4
4
3
3
3
2
2
2
1
1
0
OUTPUT BYTE 1 OUTPUT BYTE n
10776-243
Figure 40. FIFO Read
Data Sheet ADXL362
Rev. F | Page 21 of 43
MISO
SCLK
MOSI MSB IN LSB IN
HIGH IMPEDANCE
t
CSD
t
CSH
t
CLE
t
SU
t
HD
C
SS
CS
10776-244
Figure 41. Timing Diagram for SPI Receive Instructions
t
CSH
10776-245
MISO
SCLK
MOSI MSB OUT
DON’T CARE
LSB OUT
t
HIGH
t
LOW
t
DIS
t
V
CS
Figure 42. Timing Diagram for SPI Send Instructions (Shaded Portions of Figure 36, Figure 38, and Figure 40)
Table 9. SPI Digital Input/Output
Limit1
Parameter Test Conditions/Comments Min Max Unit
Digital Input
Low Level Input Voltage (VIL) 0.3 × VDD I/O V
High Level Input Voltage (VIH) 0.7 × VDD I/O V
Low Level Input Current (IIL) VIN = VDD I/O 0.1 µA
High Level Input Current (IIH) VIN = 0 V 0.1 µA
Digital Output
Low Level Output Voltage (VOL) IOL = 10 mA 0.2 × VDD I/O V
High Level Output Voltage (VOH) IOH = −4 mA 0.8 × VDD I/O V
Low Level Output Current (IOL) VOL = VOL, max 10 mA
High Level Output Current (IOH) VOH = VOH, min −4 mA
1 Limits based on characterization results, not production tested.
ADXL362 Data Sheet
Rev. F | Page 22 of 43
Table 10. SPI Timing (TA = 2C, VS = 2.0 V, VDD I/O = 2.0 V)
Limit1, 2
Parameter
Min
Max
Unit
Description
fCLK3 2.4 8000 kHz Clock Frequency
CSS 100 ns CS Setup Time
tCSH 20 ns CS Hold Time
tCSD 20 ns CS Disable Time
tSU 20 ns Data Setup Time
tHD 20 ns Data Hold Time
tHIGH 50 ns Clock High Time
tLOW 50 ns Clock Low Time
tCLE 25 ns Clock Enable Time
tV 0 35 ns Output Valid from Clock Low
tDIS 0 25 ns Output Disable Time
1 Limits based on design targets; not production tested.
2 The timing values are measured corresponding to the input thresholds (VIL and VIH) given in Table 9.
3 The minimum limit is only necessary when using FIFO.
Data Sheet ADXL362
Rev. F | Page 23 of 43
REGISTER MAP
Table 11. Register Summary
Reg Name Bits Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset
RW
0x00 DEVID_AD [7:0] DEVID_AD[7:0] 0xAD R
0x01 DEVID_MST [7:0] DEVID_MST[7:0] 0x1D R
0x02 PARTID [7:0] PARTID[7:0] 0xF2 R
0x03 REVID [7:0] REVID[7:0] 0x01 R
0x08 XDATA [7:0] XDATA[7:0] 0x00 R
0x09 YDATA [7:0] YDATA[7:0] 0x00 R
0x0A
ZDATA [7:0] ZDATA[7:0] 0x00 R
0x0B
STATUS [7:0] ERR_USER_
REGS
AWAKE INACT ACT FIFO_OVER-
RUN
FIFO_WATER-
MARK
FIFO_READY DATA_READY
0x40 R
0x0C
FIFO_ENTRIES_L
[7:0]
FIFO_ENTRIES_L[7:0]
0x00
R
0x0D
FIFO_ENTRIES_H [7:0] UNUSED FIFO_ENTRIES_H[1:0] 0x00 R
0x0E XDATA_L [7:0] XDATA_L[7:0] 0x00 R
0x0F XDATA_H [7:0] SX XDATA_H[3:0] 0x00 R
0x10 YDATA_L [7:0] YDATA_L[7:0] 0x00 R
0x11 YDATA_H [7:0] SX YDATA_H[3:0] 0x00 R
0x12 ZDATA_L [7:0] ZDATA_L[7:0] 0x00 R
0x13 ZDATA_H [7:0] SX ZDATA_H[3:0] 0x00 R
0x14 TEMP_L [7:0] TEMP_L[7:0] 0x00 R
0x15 TEMP_H [7:0] SX TEMP_H[3:0] 0x00 R
0x16 Reserved [7:0] Reserved[7:0] 0x00 R
0x17 Reserved [7:0] Reserved[7:0] 0x00 R
0x1F SOFT_RESET [7:0] SOFT_RESET[7:0] 0x00 W
0x20 THRESH_ACT_L [7:0] THRESH_ACT_L[7:0] 0x00 RW
0x21 THRESH_ACT_H [7:0] UNUSED THRESH_ACT_H[2:0] 0x00 RW
0x22 TIME_ACT [7:0] TIME_ACT[7:0] 0x00 RW
0x23 THRESH_INACT_L [7:0] THRESH_INACT_L[7:0] 0x00 RW
0x24 THRESH_INACT_H [7:0] UNUSED THRESH_INACT_H[2:0] 0x00 RW
0x25
TIME_INACT_L
[7:0]
TIME_INACT_L[7:0]
0x00
RW
0x26 TIME_INACT_H [7:0] TIME_INACT_H[7:0] 0x00 RW
0x27
ACT_INACT_CTL
[7:0]
RES
LINKLOOP
INACT_REF
INACT_EN
ACT_REF
ACT_EN
0x00
RW
0x28 FIFO_CONTROL [7:0] UNUSED AH FIFO_TEMP FIFO_MODE 0x00 RW
0x29 FIFO_SAMPLES [7:0] FIFO_SAMPLES[7:0] 0x80 RW
0x2A
INTMAP1 [7:0] INT_LOW AWAKE INACT ACT FIFO_OVER-
RUN
FIFO_WATER-
MARK
FIFO_READY DATA_READY
0x00 RW
0x2B
INTMAP2 [7:0] INT_LOW AWAKE INACT ACT FIFO_OVER-
RUN
FIFO_WATER-
MARK
FIFO_READY DATA_READY
0x00 RW
0x2C
FILTER_CTL [7:0] RANGE RES HALF_BW EXT_SAMPLE ODR 0x13 RW
0x2D
POWER_CTL [7:0] RES EXT_CLK LOW_NOISE WAKEUP AUTOSLEEP MEASURE 0x00 RW
0x2E
SELF_TEST
[7:0]
UNUSED
ST
0x00
RW
ADXL362 Data Sheet
Rev. F | Page 24 of 43
REGISTER DETAILS
This section describes the functions of the ADXL362 registers.
The ADXL362 powers up with default register values in the as
shown in the Reset column of Table 11 in the Register Map
section.
Note that any changes to the registers before the POWER_CTL
register (Register 0x00 to Register 0x2C) must be made with the
device in standby. If changes are made while the ADXL362 is in
measurement mode, they can be effective for only part of a
measurement.
DEVICE ID REGISTER
Address: 0x00, Reset: 0xAD, Name: DEVID_AD
This register contains the Analog Devices device ID, 0xAD.
DEVICE ID: 0x1D REGISTER
Address: 0x01, Reset: 0x1D, Name: DEVID_MST
This register contains the Analog Devices MEMS device
ID, 0x1D.
PART ID: 0xF2 REGISTER
Address: 0x02, Reset: 0xF2, Name: PARTID
This register contains the device ID, 0xF2 (362 octal).
SILICON REVISION ID REGISTER
Address: 0x03, Reset: 0x01, Name: REVID
This register contains the product revision ID, beginning with
0x01 and incrementing for each subsequent revision.
X-AXIS DATA (8 MSB) REGISTER
Address: 0x08, Reset: 0x00, Name: XDATA
This register holds the eight most significant bits of the x-axis
acceleration data. This limited resolution data register is used in
power conscious applications where eight bits of data are sufficient:
energy can be conserved by reading only one byte of data per
axis, rather than two.
Y-AXIS DATA (8 MSB) REGISTER
Address: 0x09, Reset: 0x00, Name: YDATA
This register holds the eight most significant bits of the y-axis
acceleration data. This limited resolution data register is used in
power conscious applications where eight bits of data are sufficient:
energy can be conserved by reading only one byte of data per
axis, rather than two.
Z-AXIS DATA (8 MSB) REGISTER
Address: 0x0A, Reset: 0x00, Name: ZDATA
This register holds the eight most significant bits of the z-axis
acceleration data. This limited resolution data register is used in
power conscious applications where eight bits of data are sufficient:
energy can be conserved by reading only one byte of data per
axis, rather than two.
Data Sheet ADXL362
Rev. F | Page 25 of 43
STATUS REGISTER
Address: 0x0B, Reset: 0x40, Name: STATUS
This register includes the following bits that describe various conditions of the ADXL362.
Table 12. Bit Descriptions for STATUS
Bits Bit Name Settings Description Reset Access
7 ERR_USER_REGS SEU Error Detect. 1 indicates one of two conditions: either an SEU event,
such as an alpha particle of a power glitch, has disturbed a user register
setting or the ADXL362 is not configured. This bit is high upon both
startup and soft reset, and resets as soon as any register write commands
are performed.
0x0 R
6 AWAKE Indicates whether the accelerometer is in an active (AWAKE = 1) or
inactive (AWAKE = 0) state, based on the activity and inactivity
functionality. To enable autosleep, activity and inactivity detection must
be in linked mode or loop mode (LINK/LOOP bits in the ACT_INACT_CTL
register); otherwise, this bit defaults to 1 and must be ignored.
0x1 R
5 INACT Inactivity. 1 indicates that the inactivity detection function has detected
an inactivity or a free fall condition.
0x0 R
4
ACT
Activity. 1 indicates that the activity detection function has detected an
overthreshold condition.
0x0
R
3 FIFO_OVERRUN FIFO Overrun. 1 indicates that the FIFO has overrun or overflowed, such
that new data replaces unread data. See the Using FIFO Interrupts
section for details.
0x0 R
2 FIFO_WATERMARK FIFO Watermark. 1 indicates that the FIFO contains at least the desired
number of samples, as set in the FIFO_SAMPLES register. See the Using
FIFO Interrupts section for details.
0x0 R
1 FIFO_READY FIFO Ready. 1 indicates that there is at least one sample available in the
FIFO output buffer. See the Using FIFO Interrupts section for details.
0x0 R
0 DATA_READY Data Ready. 1 indicates that a new valid sample is available to be read.
This bit clears when a FIFO read is performed. See the Data Ready
Interrupt section for more details.
0x0 R
ADXL362 Data Sheet
Rev. F | Page 26 of 43
FIFO ENTRIES REGISTERS
These registers indicate the number of valid data samples
present in the FIFO buffer. This number ranges from 0 to 512
or 0x00 to 0x200. FIFO_ENTRIES_L contains the least significant
byte. FIFO_ENTRIES_H contains the two most significant bits.
Bits[15:10] of FIFO_ENTRIES_H are unused (represented as X
= don’t care).
Address: 0x0C, Reset: 0x00, Name: FIFO_ENTRIES_L
Address: 0x0D, Reset: 0x00, Name: FIFO_ENTRIES_H
X-AXIS DATA REGISTERS
These two registers contain the sign extended (SX) x-axis
acceleration data. XDATA_L contains the eight least significant
bits (LSBs), and XDATA_H contains the four most significant
bits (MSBs) of the 12-bit value.
The sign extension bits (B[15:12], denoted as SX in the
XDATA_H bit map that follows) have the same value as the
MSB (B11).
Address: 0x0E, Reset: 0x00, Name: XDATA_L
Address: 0x0F, Reset: 0x00, Name: XDATA_H
Y-AXIS DATA REGISTERS
These two registers contain the sign extended (SX) y-axis
acceleration data. YDATA_L contains the eight LSBs and
YDATA_H contains the four MSBs of the 12-bit value.
The sign extension bits (B[15:12], denoted as SX in the
YDATA_H bit map that follows) have the same value as the
MSB (B11).
Address: 0x10, Reset: 0x00, Name: YDATA_L
Address: 0x11, Reset: 0x00, Name: YDATA_H
Z-AXIS DATA REGISTERS
These two registers contain the sign extended (SX) z-axis
acceleration data. ZDATA_L contains the eight LSBs, and
ZDATA_H contains the four MSBs of the 12-bit value.
The sign extension bits (B[15:12], denoted as SX in the
ZDATA_H bit map that follows) have the same value as the
MSB (B11).
Address: 0x12, Reset: 0x00, Name: ZDATA_L
Address: 0x13, Reset: 0x00, Name: ZDATA_H
TEMPERATURE DATA REGISTERS
These two registers contain the sign extended (SX) tempera-
ture sensor output data. TEMP_L contains the eight LSBs, and
TEMP_H contains the four MSBs of the 12-bit value. The value is
sign extended; therefore, Bits[B15:B12] of TEMP_H are all 0s or
all 1s, based on the value of Bit B11.
The sign extension bits (B[15:12], denoted as SX in the TEMP_H
bit map that follows) have the same value as the MSB (B11).
Address: 0x14, Reset: 0x00, Name: TEMP_L
Address: 0x15, Reset: 0x00, Name: TEMP_H
SOFT RESET REGISTER
Address: 0x1F, Reset: 0x00, Name: SOFT_RESET
Writing Code 0x52 (representing the letter, R, in ASCII or
unicode) to this register immediately resets the ADXL362. All
register settings are cleared, and the sensor is placed in standby.
Interrupt pins are configured to a high output impedance mode
and held to a valid state by bus keepers.
This is a write-only register. If read, data in it is always 0x00.
A latency of approximately 0.5 ms is required after soft reset.
Data Sheet ADXL362
Rev. F | Page 27 of 43
ACTIVITY THRESHOLD REGISTERS
To detect activity, the ADXL362 compares the absolute value of
the 12-bit (signed) acceleration data with the 11-bit (unsigned)
THRESH_ACT value. See the Motion Detection section for
more information on activity detection.
The term, THRESH_ACT, refers to an 11-bit unsigned value com-
prising the THRESH_ACT_L register, which holds its eight LSBs;
and the THRESH_ACT_H register, which holds its three MSBs.
THRESH_ACT is set in codes; the value in g depends on the
measurement range setting that is selected.
THRESH_ACT [g] = THRESH_ACT [codes]/Sensitivity
[codes per g]
Address: 0x20, Reset: 0x00, Name: THRESH_ACT_L
Address: 0x21, Reset: 0x00, Name: THRESH_ACT_H
ACTIVITY TIME REGISTER
Address: 0x22, Reset: 0x00, Name: TIME_ACT
The activity timer implements a robust activity detection that
minimizes false positive motion triggers. When the timer is
used, only sustained motion can trigger activity detection. Refer
to the Fewer False Positives section for additional information.
The value in this register sets the number of consecutive
samples that must have at least one axis greater than the activity
threshold (set by THRESH_ACT) for an activity event to be
detected.
The time (in seconds) is given by the following equation:
Time = TIME_ACT/ODR
where:
TIME_ACT is the value set in this register.
ODR is the output data rate set in the FILTER_CTL register
(Address 0x2C).
Setting the activity time to 0x00 has the same result as setting
this time to 0x01: Activity is detected when a single acceleration
sample has at least one axis greater than the activity threshold
(THRESH_ACT).
When the accelerometer is in wake-up mode, the TIME_ACT
value is ignored and activity is detected based on a single
acceleration sample.
INACTIVITY THRESHOLD REGISTERS
To detect inactivity, the absolute value of the 12-bit acceleration
data is compared with the 11-bit (unsigned) THRESH_INACT
value. See the Motion Detection section for more information.
The term, THRESH_INACT, refers to an 11-bit unsigned value
comprised of the THRESH_INACT_L registers, which holds its
eight LSBs and the THRESH_INACT_H register, which holds
its three MSBs.
This 11-bit unsigned value sets the threshold for inactivity
detection. This value is set in codes; the value (in g) depends on
the measurement range setting selected:
THRESH_INACT [g] =
THRESH_INACT [codes]/Sensitivity [codes per g]
Address: 0x23, Reset: 0x00, Name: THRESH_INACT_L
Address: 0x24, Reset: 0x00, Name: THRESH_INACT_H
INACTIVITY TIME REGISTERS
The 16-bit value in these registers sets the number of consecu-
tive samples that must have all axes lower than the inactivity
threshold (set by THRESH_INACT) for an inactivity event to
be detected.
The TIME_INACT_L register holds the eight LSBs and the
TIME_INACT_H register holds the eight MSBs of the 16-bit
TIME_INACT value.
The time in seconds can be calculated as
Time = TIME_INACT/ODR
where:
TIME_INACT is the 16-bit value set by the TIME_INACT_L reg-
ister (eight LSBs) and the TIME_INACT_H register (eight MSBs).
ODR is the output data rate set in the FILTER_CTL register
(Address 0x2C).
ADXL362 Data Sheet
Rev. F | Page 28 of 43
The 16-bit value allows for long inactivity detection times. The
maximum value is 0xFFFF or 65,535 samples. At the lowest output
data rate, 12.5 Hz, this equates to almost 90 minutes. In this con-
figuration, the accelerometer must be stationary for 90 minutes
before putting its system to sleep.
Setting the inactivity time to 0x00 has the same result as setting
this time to 0x01: Inactivity is detected when a single acceleration
sample has all axes lower than the inactivity threshold
(THRESH_INACT).
Address: 0x25, Reset: 0x00, Name: TIME_INACT_L
Address: 0x26, Reset: 0x00, Name: TIME_INACT_H
Data Sheet ADXL362
Rev. F | Page 29 of 43
ACTIVITY/INACTIVITY CONTROL REGISTER
Address: 0x27, Reset: 0x00, Name: ACT_INACT_CTL
Table 13. Bit Descriptions for ACT_INACT_CTL
Bits Bit Name Settings Description Reset Access
[7:6] UNUSED Unused Bits. 0x0 RW
[5:4] LINK/LOOP X0 Default Mode. 0x0 RW
Activity and inactivity detection are both enabled, and their interrupts (if
mapped) must be acknowledged by the host processor by reading the
STATUS register. Autosleep is disabled in this mode. Use this mode for free
fall detection applications.
01 Linked Mode.
Activity and inactivity detection are linked sequentially such that only one
is enabled at a time. Their interrupts (if mapped) must be acknowledged
by the host processor by reading the STATUS register.
11 Loop Mode.
Activity and inactivity detection are linked sequentially such that only one
is enabled at a time, and their interrupts are internally acknowledged (do
not need to be serviced by the host processor).
To use either linked or looped mode, both ACT_EN (Bit 0) and INACT_EN
(Bit 2) must be set to 1; otherwise, the default mode is used. For additional
information, refer to the Linking Activity and Inactivity Detection section.
3 INACT_REF Referenced/Absolute Inactivity Select. 0x0 RW
1 = inactivity detection function operates in referenced mode.
0= inactivity detection function operates in absolute mode.
2 INACT_EN Inactivity Enable. 0x0 RW
1 = enables the inactivity (underthreshold) functionality.
1 ACT_REF Referenced/Absolute Activity Select. 0x0 RW
1 = activity detection function operates in referenced mode.
0 = activity detection function operates in absolute mode.
0 ACT_EN Activity Enable. 0x0 RW
1 = enables the activity (overthreshold) functionality.
ADXL362 Data Sheet
Rev. F | Page 30 of 43
FIFO CONTROL REGISTER
Address: 0x28, Reset: 0x00, Name: FIFO_CONTROL
Table 14. Bit Descriptions for FIFO_CONTROL
Bits Bit Name Settings Description Reset Access
[7:4] UNUSED Unused Bits. 0x0 RW
3 AH Above Half. 0x0 RW
This bit is the MSB of the FIFO_SAMPLES register, allowing FIFO samples a
range of 0 to 511.
2 FIFO_TEMP Store Temperature Data to FIFO. 1 = temperature data is stored in the FIFO
together with x-, y-, and z-axis acceleration data.
0x0 RW
[1:0] FIFO_MODE Enable FIFO and Mode Selection. 0x0 RW
00 FIFO is disabled.
01 Oldest saved mode.
10 Stream mode.
11 Triggered mode.
Data Sheet ADXL362
Rev. F | Page 31 of 43
FIFO SAMPLES REGISTER
Address: 0x29, Reset: 0x80, Name: FIFO_SAMPLES
The value in this register specifies the number of samples to
store in the FIFO. The AH bit in the FIFO_CONTROL register
(Address 0x28) is used as the MSB of this value. The full range
of FIFO samples is 0 to 511.
The default value of this register is 0x80 to avoid triggering the
FIFO watermark interrupt (see the FIFO Watermark section for
more information).
The following bit map is duplicated from the FIFO Control
Register section to indicate the AH bit.
INT1/INT2 FUNCTION MAP REGISTERS
The INT1 and INT2 registers configure the INT1/INT2
interrupt pins, respectively. Bits[B6:B0] select which function(s)
generate an interrupt on the pin. If its corresponding bit is set to
1, the function generates an interrupt on the INT pin. Bit B7
configures whether the pin operates in active high (B7 low) or
active low (B7 high) mode.
Any number of functions can be selected simultaneously for
each pin. If multiple functions are selected, their conditions are
OR'ed together to determine the INT pin state. The status of
each individual function can be determined by reading the
STATUS register. If no interrupts are mapped to an INT pin, the
pin remains in a high impedance state, held to a valid logic state
by a bus keeper.
Address: 0x2A, Reset: 0x00, Name: INTMAP1
Table 15. Bit Descriptions for INTMAP1
Bits Bit Name Settings Description Reset Access
7 INT_LOW 1 = INT1 pin is active low. 0x0 RW
6 AWAKE 1 = maps the awake status to INT1 pin. 0x0 RW
5 INACT 1 = maps the inactivity status to INT1 pin. 0x0 RW
4 ACT 1 = maps the activity status to INT1 pin. 0x0 RW
3 FIFO_OVERRUN 1 = maps the FIFO overrun status to INT1 pin. 0x0 RW
2 FIFO_WATERMARK 1 = maps the FIFO watermark status to INT1 pin. 0x0 RW
1 FIFO_READY 1 = maps the FIFO ready status to INT1 pin. 0x0 RW
0 DATA_READY 1 = maps the data ready status to INT1 pin. 0x0 RW
ADXL362 Data Sheet
Rev. F | Page 32 of 43
Address: 0x2B, Reset: 0x00, Name: INTMAP2
Table 16. Bit Descriptions for INTMAP2
Bits Bit Name Settings Description Reset Access
7 INT_LOW 1 = INT2 pin is active low. 0x0 RW
6 AWAKE 1 = maps the awake status to INT2 pin. 0x0 RW
5 INACT 1 = maps the inactivity status to INT2 pin. 0x0 RW
4 ACT 1 = maps the activity status to INT2 pin. 0x0 RW
3 FIFO_OVERRUN 1 = maps the FIFO overrun status to INT2 pin. 0x0 RW
2
FIFO_WATERMARK
1 = maps the FIFO watermark status to INT2 pin.
0x0
RW
1 FIFO_READY 1 = maps the FIFO ready status to INT2 pin. 0x0 RW
0 DATA_READY 1 = maps the data ready status to INT2 pin. 0x0 RW
Data Sheet ADXL362
Rev. F | Page 33 of 43
FILTER CONTROL REGISTER
Address: 0x2C, Reset: 0x13, Name: FILTER_CTL
Table 17. Bit Descriptions for FILTER_CTL
Bits Bit Name Settings Description Reset Access
[7:6] RANGE Measurement Range Selection. 0x0 RW
00 ±2 g (reset default)
01 ±4 g
1X ±8 g
5 RES Reserved. 0x0 RW
4 HALF_BW Halved Bandwidth. Additional information is provided in the Antialiasing section. 0x1
1 = the bandwidth of the antialiasing filters is set to ¼ the output data rate (ODR) for
more conservative filtering.
0 = the bandwidth of the filters is set to ½ the ODR for a wider bandwidth.
3 EXT_SAMPLE External Sampling Trigger. 1 = the INT2 pin is used for external conversion timing
control. Refer to the Using Synchronized Data Sampling section for more
information.
0x0 RW
[2:0] ODR Output Data Rate. Selects ODR and configures internal filters to a bandwidth of ½ or
¼ the selected ODR, depending on the HALF_BW bit setting.
0x3 RW
000 12.5 Hz
001 25 Hz
010 50 Hz
011 100 Hz (reset default)
100 200 Hz
101111 400 Hz
ADXL362 Data Sheet
Rev. F | Page 34 of 43
POWER CONTROL REGISTER
Address: 0x2D, Reset: 0x00, Name: POWER_CTL
Table 18. Bit Descriptions for POWER_CTL
Bits Bit Name Settings Description Reset Access
7 Reserved Reserved. 0x0 RW
6 EXT_CLK External Clock. See the Using an External Clock section for additional details. 0x0 RW
1 = the accelerometer runs off the external clock provided on the INT1 pin.
[5:4] LOW_NOISE Selects Power vs. Noise Tradeoff: 0x0 RW
00
Normal operation (reset default).
01 Low noise mode.
10 Ultralow noise mode.
11 Reserved.
3 WAKEUP Wake-Up Mode. See the Operating Modes section for a detailed
description of wake-up mode.
0x0 RW
1 = the part operates in wake-up mode.
2 AUTOSLEEP Autosleep. Activity and inactivity detection must be in linked mode or
loop mode (LINK/LOOP bits in ACT_INACT_CTL register) to enable
autosleep; otherwise, the bit is ignored. See the Motion Detection section
for details.
0x0 RW
1 = autosleep is enabled, and the device enters wake-up mode
automatically upon detection of inactivity.
[1:0] MEASURE Selects Measurement Mode or Standby. 0x0 RW
00
Standby.
01 Reserved.
10 Measurement mode.
11 Reserved.
Data Sheet ADXL362
Rev. F | Page 35 of 43
SELF TEST REGISTER
Address: 0x2E, Reset: 0x00, Name: SELF_TEST
Refer to the Self Test section for information on the operation of the self test feature, and see the Using Self Test section for guidelines on
how to use this functionality.
Table 19. Bit Descriptions for SELF_TEST
Bits Bit Name Settings Description Reset Access
[7:1] UNUSED 0x0 RW
0 ST Self Test. 0x0 RW
1 = a self test force is applied to the x-, y-, and z-axes.
ADXL362 Data Sheet
Rev. F | Page 36 of 43
APPLICATIONS INFORMATION
APPLICATION EXAMPLES
This section includes a few application circuits, highlighting
useful features of the ADXL362.
Device Configuration
This section outlines the procedure for configuring the device
and acquiring data. In general, the procedure follows the sequence
of the register map, starting with Register 0x20, THRESH_ACT_L.
1. Set activity and inactivity thresholds and timers.
a. Write to Register 0x20 to Register 0x26.
b. To minimize false positive motion triggers, set the
TIME_ACT register greater than 1.
2. Configure activity and inactivity functions.
a. Write to Register 0x27.
3. Configure FIFO.
a. Write to Register 0x28 and Register 0x29.
4. Map interrupts.
a. Write to Register 0x2A and Register 0x2B.
5. Configure general device settings.
a. Write to Register 0x2C.
6. Turn measurement on.
a. Write to Register 0x2D.
Settings for each of the registers vary based on application
requirements. For more information, see the Register Details
section.
Autonomous Motion Switch
The features of the ADXL362 make it ideal for use as an
autonomous motion switch. The example outlined here
implements a switch that, once configured, operates without the
intervention of a host processor to intelligently manage system
power. In this example, the awake signal, mapped to the INT2
pin, drives a high-side power switch, such as the ADP195, to
control power to the downstream circuitry.
ADXL362
GND
INT1
INT2 CS
SCLK
MISO
MOSI
SPI
INTERFACE
V
S
V
S
C
S
V
DD I/O
V
DD I/O
C
IO
INTERRUPT
CONTROL
AWAKE
GND
EN
VIN
VS
LOAD
VOUT
ADP195
LEVEL SHIFT
AND SLEW
RATE CONTROL
REVERSE
POLARITY
PROTECTION
10776-041
Figure 43. Awake Signal to Control Power to Downstream Circuitry
Start-up Routine
This routine assumes a ±2 g measurement range and operation
in wake-up mode.
1. Write 250 decimal (0xFA) to Register 0x20, and write 0 to
Register 0x21: sets activity threshold to 250 mg.
2. Write 150 decimal (0x96) to Register 0x23, and write 0 to
Register 0x24: sets inactivity threshold to 150 mg.
3. Write 30 decimal (0x1E) to Register 0x25: sets inactivity
timer to 30 samples or about 5 seconds.
4. Write 0x3F to Register 0x27: configures motion detection in
loop mode and enables referenced activity and inactivity
detection.
5. Write 0x40 to Register 0x2B: map the AWAKE bit to INT2.
The INT2 pin is tied to the gate of the switch.
6. Write 0x0A to Register 0x2D: begins the measurement in
wake-up mode.
Using External Timing Triggers
Figure 44 shows an application diagram for using the INT1 pin
as the input for an external clock. In this mode, the external
clock determines all accelerometer timing, including the output
data rate and bandwidth.
To enable this feature, at the end of the desired start-up routine,
set Bit 6 in the POWER_CTL register; for example, write 0x42
to this register to enable the use of an external clock and place
the accelerometer into measurement mode.
ADXL362
GND
INT1
INT2 CS
SCLK
MISO
MOSI
SPI
INTERFACE
V
S
V
S
C
S
V
DD I/O
V
DD I/O
C
IO
INTERRUPT
CONTROL
EXTERNAL
CLOCK
10776-042
Figure 44. INT1 Pin as the Input for the External Clock
Figure 45 is an application diagram for using the INT2 pin as a
trigger for synchronized sampling. Acceleration samples are
produced every time this trigger is activated. To enable this
feature, near the end of the desired start-up routine, set Bit 3 in
the FILTER_CTL register; for example, write 0x4B to this register
to enable the trigger and configure the accelerometer for ±8 g
measurement range and 100 Hz ODR.
Data Sheet ADXL362
Rev. F | Page 37 of 43
ADXL362
GND
INT1
INT2 CS
SCLK
MISO
MOSI
SPI
INTERFACE
V
S
V
S
C
S
V
DD I/O
V
DD I/O
C
IO
INTERRUPT
CONTROL
SAMPLING
TRIGGER
10776-043
Figure 45. Using the INT2 Pin to Trigger Synchronized Sampling
Example: Implementing Free Fall Detection
Many digital output accelerometers include a built-in free fall
detection feature. In the ADXL362, implement this function
using the inactivity interrupt.
When an object is in true free fall, acceleration on all axes is 0 g.
Thus, free fall detection is achieved by looking for acceleration
on all axes to fall below a certain threshold (close to 0 g) for a
certain amount of time. The inactivity detection functionality,
when used in absolute mode, does exactly this.
To use inactivity to implement free fall detection, set the value
in THRESH_INACT to the desired free fall threshold. Values
between 300 mg and 600 mg are recommended; the register
setting for these values varies based on the g range setting of the
device, as follows:
THRESH_INACT =
Threshold Value [g] × Scale Factor [LSB per g]
Set the value in TIME_INACT to implement the minimum
amount of time that the acceleration on all axes must be less
than the free fall threshold to generate a free fall condition.
Values between 100 ms and 350 ms are recommended; the
register setting for this varies based on the output data rate.
TIME_INACT = Time [sec] × Data Rate [Hz]
When a free fall condition is detected, the inactivity status is set
to 1 and, if the function is mapped to an interrupt pin, an
inactivity interrupt triggers on that pin.
Start-up Routine
The following start-up routine configures the ADXL362 for a
typical free fall application. This routine assumes a ±8 g
measurement range and 100 Hz output data rate. Thresholds
and timing values can be modified to suit particular application
needs.
1. Write 0x96 (150 codes) to Register 0x23: sets free fall
threshold to 600 mg.
2. Write 0x03 to Register 0x25: sets free fall time to 30 ms.
3. Write 0x04 to Register 0x27: enables absolute inactivity
detection.
4. Write 0x20 to Register 0x2A or Register 0x2B to map the
inactivity interrupt to INT1 or INT2, respectively.
5. Write 0x83 to Register 0x2C: configures the accelerometer
to ±8 g range, 100 Hz ODR (output data rate).
6. Write 0x02 to Register 0x2D to begin measurement.
POWER
Power Supply Decoupling
Figure 46 shows the recommended bypass capacitors for use
with the ADXL362.
ADXL362
GND
INT1
INT2 CS
SCLK
MISO
MOSI
SPI
INTERFACE
V
S
V
S
C
S
V
DD I/O
V
DD I/O
C
IO
INTERRUPT
CONTROL
10776-040
Figure 46. Recommended Bypass Capacitors
A 0.1 µF ceramic capacitor (CS) at VS and a 0.1 µF ceramic capacitor
(CIO) at VDD I/O placed as close as possible to the ADXL362. Supply
pins are recommended to adequately decouple the accelerometer
from noise on the power supply. It is also recommended that VS
and VDD I/O be separate supplies to minimize digital clocking
noise on the VS supply. If this is not possible, additional filtering
of the supplies may be necessary.
If additional decoupling is necessary, place a resistor or ferrite
bead, no larger than 100 Ω, in series with VS. Additionally,
increasing the bypass capacitance on VS to a 1 µF tantalum
capacitor in parallel with a 0.1 µF ceramic capacitor can also
improve noise.
Ensure that the connection from the ADXL362 ground to the
power supply ground has low impedance because noise transmitted
through ground has an effect similar to noise transmitted through VS.
Power Supply Requirements
The ADXL362 is designed to operate using supply voltage rails
ranging from 1.8 V to 3.3 V. The operating voltage range (VS),
specified in Table 1, ranges from 1.6 V to 3.5 V to account for
inaccuracies and transients of up to ±10% on the supply voltage.
The ADXL362 does not require any particular start-up transient
characteristics, except that it must always be started up from 0 V.
When the device is in operation, any time power is removed
from the ADXL362, or falls below the operating voltage range,
the supplies (VS, VDD I/O, and any bypass capacitors) must be
discharged completely before power is reapplied. To enable
supply discharge, it is recommended to power the device from
a microcontroller GPIO, connect a shutdown discharge switch
to the supply (Figure 47), or use a voltage regulator with a
shutdown discharge feature, such as the ADP160.
ADXL362 Data Sheet
Rev. F | Page 38 of 43
ADXL362
GND
INT1
SHUTDOWN
NOTES
1. THE ADXL362 SUPPLIES MUST BE DISCHARGED FULLY EACH TIME
THE VOLTAGE ON THEM DROPS BELOW THE SPECIFIED OPERATING
RANGE. A SHUTDOWN SWITCH IS ONE WAY TO DISCHARGE THE SUPPLIES.
VIN
R1
INT2 CS
SCLK
MISO
MOSI
SPI
INTERFACE
V
S
V
S
C
S
V
DD I/O
V
DD I/O
C
IO
10776-141
Figure 47. Using a Switch to Discharge the ADXL362 Supplies
FIFO MODES
The FIFO is a 512-sample memory buffer that can save power,
unburden the host processor, and autonomously record data.
The 512 FIFO samples can be allotted as either:
170 sample sets of concurrent 3-axis data; or
128 sample sets of concurrent 3-axis and temperature data
The FIFO operates in one of the four modes described in this
section.
FIFO Disabled
When the FIFO is disabled, no data is stored in it and any data
already stored in it is cleared.
The FIFO is disabled by setting the FIFO_MODE bits in the
FIFO_CONTROL register (Address 0x28) to Binary Value 0b00.
Oldest Saved Mode
In oldest saved mode, the FIFO accumulates data until it is full
and then stops. Additional data is collected only when space is
made available by reading samples out of the FIFO buffer. (This
mode of operation is sometimes referred to as “First N.”)
The FIFO is placed into oldest saved mode by setting the
FIFO_MODE bits in the FIFO_CONTROL register (Address
0x28) to Binary Value 0b01.
Stream Mode
In stream mode, the FIFO always contains the most recent data.
The oldest sample is discarded when space is needed to make
room for a newer sample. (This mode of operation is sometimes
referred to as “Last N.”)
Stream mode is useful for unburdening a host processor. The
processor can tend to other tasks while data is being collected in
the FIFO. When the FIFO fills to a certain number of samples
(specified by the FIFO_SAMPLES register along with the AH
bit in the FIFO_CONTROL register), it triggers a FIFO
watermark interrupt (if this interrupt is enabled). At this point,
the host processor can read the contents of the entire FIFO and
then return to its other tasks as the FIFO fills again.
The FIFO is placed into stream mode by setting the FIFO_MODE
bits in the FIFO_CONTROL register (Address 0x28) to Binary
Value 0b10.
Triggered Mode
In triggered mode, the FIFO saves samples surrounding an
activity detection event. The operation