MAX14871 Datasheet by Analog Devices Inc./Maxim Integrated

View All Related Products | Download PDF Datasheet
maxim integrated ,,
General Description
The MAX14871 DC motor driver provides a low-power
and simple solution for driving and controlling brushed
motors with voltages between 4.5V and 36V. Very low
driver on resistance reduces power during dissipation.
The MAX14871 features a charge-pump-less design for
reduced external components and low supply current.
Integrated current regulation allows user-defined peak startup
motor currents and requires minimal external components.
The MAX14871 includes 3 modes of current regulation:
fast decay, slow decay, and 25% current ripple modes.
Current regulation based on 25% ripple simplifies the
design and enables regulation independent of motor
characteristics. A separate voltage sense input (SNS) reduc-
es current-sensing errors due to parasitic trace resistance.
The MAX14871 features shoot-through protection and
internal free-wheeling diodes that absorb inductive motor
currents. Driver outputs are short-circuit-protected from
shorts to ground, to the supply, and between M1 and M2.
An active-low FAULT output signals thermal overload and
overcurrents during fault conditions.
The MAX14871 is available in a 16-pin TSSOP-EP package
and operates over the -40°C to +85°C temperature range.
Applications
Printers and Scanners
Industrial Automation
Vending and Gaming Machines
Benefits and Features
Drive More Power and Reduce Footprint
Up to 2.8A Peak Motor-Current Package
Flexible 4.5V–36V Supply Enables Longer Runtime
Low Power Consumption Runs Cooler and Longer
334mΩ (typ) Total Bridge On-Resistance
1mA (typ) Supply Current at 30kHz/24V
10µA (max) Standby Current at 12V
Simplified Designs Reduces Time to Market
Charge-Pump-Less Architecture
Current Regulation Only Requires a Sense Resistor
Current-Sense Input Simplifies PCB Layout
Internal/External VREF for Current Regulation
Fast/Slow/25% Ripple Current Regulation Modes
Integrated Protection Provides Robust Driving Solutions
Short-Circuit-Protected Drivers
Thermal Shutdown Undervoltage Lockout
Diagnostic FAULT Output
-40°C to +85°C Temperature Range
Ordering Information appears at end of data sheet.
19-7063; Rev 0; 9/14
DRIVER
V
DD
SNS
PWM
DIR
MAX14871
GND
COM
M1 M2
EN
FAULT
DRIVER
V
DD
V
DD
CURRENT
REGULATION
R
SENSE
MODE
V
REF
TCOFF
µC
IRQ
PWM
GPO
24V
3.3V
3.3V
M
3.3V
C
OFF
Typical Application Circuit
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
EVALUATION KIT AVAILABLE
(All voltages referenced to GND)
VDD ........................................................................-0.3V to +40V
M1, M2 ....................................................... -0.3V to (VDD+0.3V)
PWM, DIR, FAULT, EN, SNS, VREF,
MODE, TCOFF ............................................................... -0.3V to +6.0V
COM .....................................................................-0.3V to +0.3V
Current Into M1, M2 .............................................................±3A
Continuous Power Dissipation (TA = +70°C)
Single-Layer Board (derate at 21.3mW/°C
above +70°C) ............................................................1702mW
Multiple-Layer Board (derate at 26.1mW/°C
above +70°C) ............................................................2088mW
Operating Temperature Range ........................... -40°C to +85°C
Junction Temperature ...................................................... +150ºC
Storage Temperature Range .............................-65ºC to +150°C
Lead Temperature (Soldering, 10s) ................................+300°C
Solder Temperature (Reflow) .........................................+260°C
Junction-to-Case Thermal Resistance (θJC)
TSSOP-EP (Single-Layer Board) ..................................3°C/W
TSSOP-EP (Multiple-Layer Board) ................................3°C/W
Junction-to-Ambient Thermal Resistance (θJA)
TSSOP-EP (Single-Layer Board) ................................47°C/W
TSSOP-EP (Multiple-Layer Board) ...........................38.3°C/W
(Note 1)
(VDD = 4.5V to 36V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VDD = 12V, TA = +25°C)(Note 3)
Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
POWER SUPPLY
Supply Voltage VDD 4.5 36 V
Supply Current IDD
EN = low, M1/M2
not connected
fPWM = 50kHz 1
mA
No switching 0.5 1.2
Shutdown Supply Current ISHDN
EN = high, Driver
is in shutdown
VDD = 12V 3.7 10 μA
VDD = 36V 10 20
Undervoltage Lockout
Threshold VUVLO VDD rising 3.3 3.8 4.3 V
Undervoltage Lockout
Threshold Hysteresis VUVLO_HYST 400 mV
DRIVER (M1, M2)
Driver Output Resistance
(High-Side + Low-Side) RON IM_ = 2.8A TJ = 25°C 334 435
TJ = 125°C 465 620
Driver Overload Current Limit IM_OL 3 A
M1, M2 Leakage Current IM_LKG EN = High, VM1 = VM2 = 0V or VDD -1 +1 μA
M1, M2 Body Diode Forward-
Voltage VBF
Low-side diode, EN = High, IF = 2.8A 1.5
V
High-side diode, EN = High, IF = 2.8A 1.5
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
www.maximintegrated.com Maxim Integrated
2
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Package Thermal Characteristics
Electrical Characteristics
(VDD = 4.5V to 36V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VDD = 12V, TA = +25°C)(Note 3)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
CURRENT REGULATION (VREF, SNS, COM, TCOFF, MODE)
MODE Select Threshold VMODE_TH
Fixed Off-Time, Fast Decay Current
Regulation 0.2
V
25% Ripple Current Regulation 0.5 1
Fixed Off-Time, Slow Decay Current
Regulation 1.5
MODE Internal Pulldown
Resistance RMODE_PD VMODE = 5V 0.6 1 2.2
VREF Internal/External Select
Threshold VVREF_TH 0.2 0.4 V
VREF Voltage Range for Exter-
nal VREF Current Regulation VVREF
VDD ≥ 5V 0.5 2 V
VDD < 5V 0.5 1.3
VREF Input Leakage IVREF_LKG VREF = 2V -1 +1 μA
SNS Threshold for Internal
VVREF Current Regulation
VSNS_IVR_
THR
VSNS rising, VVREF < VVREF_TH, All
current regulation modes 94 100 110
mV
VSNS_IVR_THF
VSNS falling, 25% Ripple Mode,
VVREF < VVREF_TH
-82 -75 -69
SNS Threshold for External
VVREF Current Regulation
VSNS_ER_THR
VSNS rising, VVREF > VVREF_TH,
All current regulation modes
VVREF
/ AV
V
VSNS_ER_THF
VSNS falling, 25% Ripple Mode,
VVREF > VVREF_TH
0.75 x
VVREF
/AV
Current-Sense Amplifier Gain AVVVREF = 1V (Note 4) 9.6 10 10.5 V/V
SNS Input Leakage Current ISNS_LKG VSNS = ±250mV -1 +1 μA
COM Leakage Current ICOM_LKG EN = High, VCOM = ±250mV -1 +1 μA
TCOFF Current ITCOFF TCOFF is connected to GND 6 10 15 μA
TCOFF Threshold VTCOFF 0.92 1 1.08 V
LOGIC SIGNALS (PWM, DIR, EN, FAULT)
Input Logic-High Voltage VIH PWM, DIR 2 V
Input Logic-Low Voltage VIL PWM, DIR 0.8 V
EN Input Logic-High Voltage VEN_IH 1.6 V
EN Input Logic-Low Voltage VEN_IL 0.4 V
Input Leakage Current IIL PWM, DIR, EN, VINPUT = 5.5V or 0V -1 +1 μA
FAULT Output Low Voltage VOL FAULT asserted, ISINK = 5mA 0.5 V
FAULT Off Leakage Current IF_LKG FAULT deasserted, VFAULT = 5.5V -1 +1 μA
PROTECTION
Thermal-Shutdown Threshold TSHDN Temperature rising, FAULT asserted +160 °C
Thermal-Shutdown Hysteresis TSHDN_HYST 10 °C
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
www.maximintegrated.com Maxim Integrated
3
Electrical Characteristics (continued)
(VDD = 4.5V to 36V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VDD = 12V, TA = +25°C)(Note 3)
Note 2: All units are production tested at TA = +25°C. Specifications over temperature are guaranteed by design.
Note 3: AV is the fixed voltage gain of the internal current sense amplifier. It is the factor by which the VSNS voltage is multiplied for
comparison with the external VREF voltage when using external VREF current regulation. See the Applications Information
section for more information.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
PWM Frequency fSW
EN = Low, Switching signal applied
at PWM 50 kHz
Dead Time tDEAD 140 ns
M1, M2 Slew Rate SR 200 V/μs
M1, M2 High-Side Propagation
Delay tPR
RL = 1kΩ, CL = 50pF, PWM/DIR ris-
ing, Figure 1 620 ns
M1, M2 Low-Side Propagation
Delay tPF
RL = 1kΩ, CL = 50pF, PWM/DIR fall-
ing, Figure 1 583 ns
Fixed Off-Time with Internal
VREF Current Regulation tOFF_D
PWM = High, EN = Low, VSNS >
VSNS_IVR_THR, VVREF < VVREF_
TH, TCOFF unconnected
7.8 15 22 μs
Current Regulation Minimum
On-Time tCR_BL
PWM = High, EN = Low, VSNS >
VSNS_IR_THR or VSNS_ER_THF 2.5 μs
Overcurrent Blanking Time tOC_BL
M1/M2 is shorted to VDD or GND,
Figure 2 1μs
Overcurrent Autoretry Timeout tOC_TO
PWM = High, EN = Low, IM or IM2 >
IM_OL, Figure 2 2 ms
Enable Turn-on Delay tEN_ON
PWM = High, RL = 1kΩ, CL = 50pF,
EN falling, M1/M2 rising to 10%,
Figure 3
23 μs
Enable Turn-off Delay tEN_OFF
PWM = High, RL = 1kΩ, CL = 50pF,
EN rising, M1/M2 falling to 90%,
Figure 3
50 μs
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
www.maximintegrated.com Maxim Integrated
4
AC Electrical Characteristics
Figure 1. M1/M2 Propagation Delays
R
L
C
L
M1/ M2
tPR tPF
0V
VL
VDD
0V
PWM/DIR
M1/M2
1V
1V
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
www.maximintegrated.com Maxim Integrated
5
Test Circuits/Timing Diagrams
FAULT
Figure 2. Overcurrent Autoretry Timeout
Figure 3. Enable/Disable Delays
FAULT
tOC_BL
VL
0V
IM1 or IM2
tOC_TO
IM_OL
0A
RLCL
M1/ M2
tEN_ON tEN_OFF
0V
VL
VDD
0V
EN
M1/M2
1.5V 1.5V
10%
90%
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
www.maximintegrated.com Maxim Integrated
6
Test Circuits/Timing Diagrams (continued)
:25 v w)
(VDD = 24V, TA = +25°C, unless otherwise noted.)
0
2
4
6
8
10
12
-45 -30 -15 015 30 45 60 75 90
ISHDN (µA)
TEMPERATURE (oC)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
toc04
VDD = 4.5V
VDD = 36V
VDD = 24V
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0 1000 2000 3000
ON-RESISTANCE ()
LOAD CURRENT (mA)
HIGH-SIDE ON RESISTANCE
vs. LOAD CURRENT
toc01
VDD = 4.5V
VDD =36V
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 1 2 3
VBF (V)
LOAD CURRENT (A)
HIGH-SIDE M1/M2 BODY DIODE
FORWARD-VOLTAGE vs. LOAD
toc07
TA= 25°C
TA= 85°C
TA= -40°C
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
01000 2000 3000
ON-RESISTANCE ()
LOAD CURRENT (mA)
LOW-SIDE ON RESISTANCE
vs. LOAD CURRENT
toc02
VDD = 4.5V
VDD = 36V
0
5
10
15
20
25
30
35
40
45
50
55
100 150 200 250 300 350 400 450 500
tOFF (µs)
COFF (pF)
OFF-TIME vs COFF CAPACITANCE
toc08
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
-45 -20 5 30 55 80 105 130
ON-RESISTANCE ()
TEMPERATURE (oC)
ON-RESISTANCE
vs. TEMPERATUREtoc03
LOW-SIDE
HIGH-SIDE
ILOAD = 1A
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0 5 10 15 20 25 30 35 40 45 50
ICC (mA)
DATA RATE (kHz)
SUPPLY CURRENT
vs. SWITCHING RATE toc05
VDD = 5V
VDD = 36V
CL= 10pF on M1/M2
VDD = 24V
VDD = 12V
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 1 2 3
V
BF
(V)
LOAD CURRENT (A)
LOW-SIDE M1/M2 BODY DIODE
FORWARD-VOLTAGE vs. LOAD toc06
TA= 25°C
TA= 85°C
TA= -40°C
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
Maxim Integrated
7
www.maximintegrated.com
Typical Operating Characteristics
PIN NAME FUNCTION
1, 16 COM COM Current Output. Connect a sense resistor, RSENSE, from COM to GND to use internal current
regulation and/or external current control. Connect both COM pins together.
2, 3 M1 Motor Driver Output 1. See the Function Tables for more information. Connect both M1 pins together.
4, 13 VDD
Power Supply Input. Bypass VDD to GND with a 1μF ceramic capacitor as close to the device as
possible. Connect both VDD pins together.
5 SNS Current Sense Input. Connect SNS to COM to enable current regulation. To bypass current regulation,
connect SNS to GND.
6 PWM PWM Control Logic Input. PWM and DIR control M1 and M2. See the Function Tables for more
information.
7 DIR Direction Control Logic Input. PWM and DIR control M1 and M2. See the Function Tables for more
information.
8 MODE
Current Regulation Mode Select Input. Connect MODE to GND for fast decay regulation. Connect
VMODE > 1.5V for slow decay current regulation. Connect 0.5V ≤ VMODE ≤ 1V for fast decay with 25%
ripple. MODE has a 1MΩ internal pull-down resistor.
9 TCOFF
Current Regulation Timing Control. For external VREF-based current regulation, connect a capacitor
to TCOFF to set the off-time (tOFF). For internal VREF-based current regulation leave TCOFF uncon-
nected when using internal VREF-based current regulation. See the Current Regulation section for more
information.
TOP VIEW
* EP = Exposed Pad. Connect to ground plane.
16
15
14
13
12
11
9
1
2
3
4
5
6
8
COM
+
M2
M2
VDD
VDD
M1
M1
COM
MAX14871
VREF
EN
TCOFF
MODE
PWM
10
7FAULT
DIR
SNS
TSSOP-EP
*EP
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
www.maximintegrated.com Maxim Integrated
8
Pin Configuration
Pin Description
PIN NAME FUNCTION
10 FAULT Open-Drain Active-Low Fault Output. FAULT goes low during an overcurrent condition and thermal
shutdown.
11 EN Active-Low Enable Input. Drive EN low to enable the driver outputs. Drive EN high to tri-state the driver
outputs.
EP GND Ground
14, 15 M2 Motor Driver Output 2. See the Function Tables for more information. Connect both M2 pins together.
12 VREF
Reference Voltage Input. The voltage applied to VVREF sets the maximum motor current during external
VVREF-based current regulation. Set VVREF<VREF_TH for internal VVREF-based current regulation.
See the Function Tables and the Current Regulation section for more information.
- EP Exposed Pad. Connect to ground.
INPUTS OUTPUTS OPERATING MODE
EN PWM DIR M1 M2
1 X X High-Impedance High-Impedance Shutdown
0 0 X GND GND Brake
0 1 0 GND VDD Counter-Clockwise/Reverse
0 1 1 VDD GND Clockwise/Forward
INPUTS OPERATING MODE (SEE TABLE 1)
EN VREF MODE VSNS
0 < 0.2V X < 0.1V Normal PWM Operation. No current regulation.
0 < 0.2V VMODE < 0.5V > 0.1V Current regulation based on 15μs (typ) fixed off-time control
with fast decay using internal VREF.
0 < 0.2V 0.5V < VMODE < 1V > 0.1V Current regulation based on 25% current ripple fast decay
using internal VREF.
0 < 0.2V VMODE > 1.5V > 0.1V Current regulation based on 15μs (typ) fixed off-time control
with slow decay using internal VREF.
0 > 0.4V X < VVREF/10 Normal PWM Operation. No current regulation.
0 > 0.4V VMODE < 0.5V > VVREF/10 Current regulation based on fixed TOFF-time control with fast
decay using external VREF.
0 > 0.4V 0.5V < VMODE < 1V > VVREF/10 Current regulation based on 25% current ripple fast decay
using external VREF.
0 > 0.4V VMODE > 1.5V > VVREF/10 Current regulation based on fixed TOFF-time control with
slow decay using external VREF.
Current Regulation Logic
PWM/DIR Control Logic
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
www.maximintegrated.com Maxim Integrated
9
Pin Description (continued)
Function Table
X = Don’t care
X = Don’t care
Rig» 74> 74> FA—w 7 EH 74> 74>
Detailed Description
The MAX14871 DC brushed motor driver provides a
low-power and flexible solution for driving and controlling
brushed motors with voltages between 4.5V and 36V.
Peak motor currents of up to 2.8A ensure for large motor
torque that is controllable by an external PWM signal and/
or by autonomous internal current regulation.
Charge-pump-less design ensures for minimal external
components and low supply current.
Integrated current regulation allows limiting peak startup
motor currents. Shoot-through protection with a 140ns
(typ) dead time ensures low operating current. Internal
free-wheeling diodes absorb inductive motor currents. The
FAULT output signals thermal overload and overcurrents.
Overcurrent Protection
The MAX14871 is protected against shorts on M1/M2 to
any voltages between VDD and GND, including shorts
to GND, VDD and between M1 and M2 via overcurrent
limiting. When a current above 6A (typ) flows through
M1 or M2 for longer than 1µs, an overcurrent condition
is detected and the H-bridge drivers are automatically
disabled and the FAULT output asserts.
If the overcurrent condition continues for longer than the
overcurrent autoretry timeout (2ms (typ)) the MAX14871
enters autoretry mode. In autoretry mode, the M1 and M2
outputs are re-enabled for 1µs (typ) and FAULT goes high
impedance. The drivers are disabled again and FAULT is
re-asserted if the overcurrent condition persists.
PWM Control
The PWM input is used for motor speed/torque control.
Increasing or decreasing the duty cycle at PWM sets the
effective (average) voltage across the motor terminals
and allows first-order speed control.
When PWM is logic-high, the motor is driven in the
direction defined by DIR. When PWM is logic low, the
bridge is in brake mode. In brake mode, the motor current
continues flowing and recirculates through the low-side
transistors of the H-bridge driver, due to its inductive
impedance and back EMF.
DRIVER
VDD
SNS
PWM
DIR
MAX14871
GND
COM
M1 M2
EN
FAULT DRIVER
VDD VDD
CURRENT
REGULATION
RSENSE
MODE
VREF
TCOFF
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
www.maximintegrated.com Maxim Integrated
10
Functional Diagram
Slope Control
The MAX14871 drivers turn-on and turn-off with active
slope control during the M1/M2 transition times. This
integrated slew rate limiting reduces EMC, like conducted
and radiated EMI, associated with high di/dt and dv/dt
rates.
Thermal Shutdown
The MAX14871 includes integrated protection against
thermal overload. When the junction temperature exceeds
160°C (typ), the H-bridge is tri-stated and FAULT asserted.
M1 and M2 are automatically re-enabled when the
junction temperature falls to 150°C (typ).
Current Sensing
Connect a sense resistor (RSENSE) between COM and
GND to monitor the motor current during operation. Select
RSENSE such that the voltage at COM created by motor
current flowing through the sense resistor is limited to with-
in 250mV relative to GND (-250mV ≤ VCOM +250mV).
Minimize series trace resistance from RSENSE to GND to
minimize voltage sense errors due to parasitic trace inter-
connect resistance. Use a star ground connection between
the MAX14871 GND pins and the GND-side of RSENSE.
Connect the SNS trace close to the RSENSE resistor in
order to minimize current-sensing error introduced by IR
voltage created by the trace resistance of the high-current
COM to RSENSE trace. If external current monitoring/
regulation is used, as shown in Figure 5, connect the
voltage sense inputs close to the RSENSE resistor. Optionally
use differential voltage sensing for higher accuracy
sensing. Connect the voltage sense close to the RSENSE
resistor and/or use differential voltage-sensing. See Figure 4.
Current Regulation
The MAX14871 features internal current-regulation to limit
the stall current. Current regulation is based on the maxi-
mum motor current (set with the RSENSE resistor) and
the voltage at VREF. When the motor current exceeds the
value, the motor current is automatically reduced, either
by driving both H-bridge outputs low (braking/slow decay),
Table 1. Current Regulation Modes
INPUTS CURRENT REGULATION MODE
MODE VREF Regulation Mode Decay Type VREF TCOFF
0.75V GND 25% Ripple FAST Internal (=1V) -
0.75V > 0.4V 25% Ripple FAST External -
GND GND TCOFF FAST Internal (=1V) 15µs
> 1.5V GND TCOFF SLOW Internal (=1V) 15µs
GND > 0.4V TCOFF FAST External Tof f
> 1.5V > 0.4V TCOFF SLOW External To ff
Figure 4. Star connection between COM, SNS, and GND
EP
M1
M2
To SNS
COM
COM
RSENSE
GND
GND GND
GND
GND
GND
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
www.maximintegrated.com Maxim Integrated
11
or by reversing the H-bridge direction (fast decay). The
H-bridge is turned back to normal polarity after a defined
delay time (TOFF mode) or after the motor current has
reduced by 25% (25% ripple mode). See Table 1. The
MAX14871 Function Tables show how to set the regula-
tion mode.
Regulation Modes
The MAX14871 offers two internal current regulation
modes: Constant off-time (TOFF) and 25% current ripple
regulation. For both modes, regulation is set when the
motor current (IM) exceeds the current limit defined by the
VREF voltage and the sense resistor:
IM_MAX = VVREF/(AV x RSENSE)
VREF
Either the internal VVREF voltage or an external voltage
on VREF can be used for current regulation. Select inter-
nal VREF-based regulation by setting VVREF < VREF_TH.
The internal VVREF is 1V (typ).
When an external voltage is used, the range of VREF is
defined by VVREF.
Fixed Off-Time (TOFF-time) Regulation
Fixed off-time regulation turns the H-bridge driver off for
a fixed time (tOFF time), as defined by the value of the
COFF capacitor connected between TCOFF and GND:
tOFF (µs)= COFF(pF)/10.
If VVREF < VVREF_TH and TCOFF is left unconnected,
then tOFF is 15µs (typ).
During the fixed TOFF-time regulation, the H-bridge can
operate in either slow or fast decay mode. See Table 1.
Slow Decay Mode
Slow decay, also called brake mode, is selected by set-
ting VMODE > 1.5V. In slow decay, both H-bridge low-side
drivers are turned on so that the inductive motor
current recirculates through the low-side transistors and
the motor’s terminals see a differential voltage near
zero (VDIFF = 2 x IM x RON_LS). During the slow-decay
TOFF period (tOFF) motor current does not flow through
the external VDD/GND supply and the voltage across
RSENSE is zero. The current decay during tOFF is a
first-order exponential decay with a time constant equal
to the motor’s electrical time constant (L/R). The rate of
current decay during tOFF is proportional to the motor’s
back EMF/rotational speed.
Fast Decay Mode
Fast decay mode can be used as an alternative to slow
decay during fixed off-time regulation. Fast decay is
enabled by setting VMODE < 0.2V. In fast decay, the
H-bridge polarity is reversed during the tOFF period,
which results in faster motor current decay, since –VDD
is applied across the motor’s terminals. The motor
current decrease is first order with an L/R time constant
and proportional to (VDD + VEMF).
Note that if tOFF is larger than the motor’s L/R electrical
time constant, the inductive current can reverse direction,
causing the motor not to start-up. If fixed off-time regula-
tion with fast decay is used, select TOFF carefully, based
on the motor’s electrical characteristics.
During fast decay, the motor’s inductive current recircu-
lates through the external VDD supply, which charges up
the VDD bypass capacitor. Thus the voltage seen across
RSENSE is negative during the tOFF delay.
25% Ripple Regulation
25% ripple regulation is based on the H-bridge switching
to fast decay period until the motor current falls by 25%.
When IM reaches the regulation limit, the bridge enters
fast decay until the IM falls to 75% of the current limit. The
H-bridge polarity is then turned back to normal drive. Thus
the motor current ramps up and down between 75% and
100% of the set-point current.
25% ripple regulation eliminates tOFF time tuning and the
TCOFF capacitor, allowing motors to be exchanged without
redesign.
Since 25% ripple regulation uses fast decay, the voltage
seen across RSENSE is negative during the time period
that the H-bridge polarity is reversed.
Select 25% ripple regulation mode by setting 0.5V <
VMODE < 1.0V. Leave TCOFF unconnected when 25%
ripple is used.
Applications Information
Layout Considerations
Connect duplicate pins (COM pins and VDD pins) togeth-
er with low-resistance traces. See the Current Sensing
section for further layout recommendations.
Power Considerations
The MAX14871 driver can generate more power than the
package for the device can safely dissipate. Total power
dissipation for the device is calculated using the following
equation:
PTOTAL = PDRIVER + PSW + PD
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
www.maximintegrated.com Maxim Integrated
12
The power dissipated inside of the driver is calculated as:
PDRIVER = IM_LOAD2 x RON
where IM_LOAD is the motor current and RON is the on-
resistance of the high and low-side FETs.
PSW is the power generated by the driver during the rise/
fall times in switching, and includes both arms of the bridge.
Calculate PSW using the following equation:
PSW = IM_LOAD x 2 x VDS
= IM_LOAD x 2 x (1/2 x VDD x fSW x tR)
where IM_LOAD is the motor current, tR is the 200ns
(typ) rise or fall time of the driver output, and fSW is the
switching frequency.
The internal diodes dissipate power during switching, as
well. Calculate the power dissipated in the diodes as:
PD = IM_LOAD x 2 x VBF x tDEAD x fSW
Operation Without Internal Current Regulation
To operate the MAX14871 without internal or external
current regulation, connect SNS directly to GND. No
sense resistor is required for this configuration. See
Figure 4.
Operation with External Current Regulation
The motor current can be controlled by external PWM
regulation using sense-resistor feedback in a control loop.
To disable the internal current regulation circuitry of the
MAX14871 and use external regulation, connect SNS
directly to ground. See Figure 5.
Note that, if fast decay control is used, the COM voltage
pulses negatively when the H-bridge direction is inverted.
Use of External Capacitors
Maxim does not recommend using external capacitors
across the motor terminals. Added capacitance between
H-bridge outputs increases the power dissipated in the
H-bridge by:
PD = VDD2 x C x fSW
where C is the capacitance across M1/M2 and fSW is
the M1/M2 switching frequency. This power is dissipated
without good reason.
Note that conducted EMI on the VDD lines is also
worsened due to the high-capacitive current spikes.
Figure 5. Operation with External Current Regulation
DRIVER
VDD
SNS
PWM
DIR
MAX14871
GND
COM
M1 M2
EN
FAULT
DRIVER
VDD VDD
CURRENT
REGULATION
R
SENSE
MODE
VREF
TCOFF
µC
IRQ
PWM
GPO
ADC
9V
3.3V
3.3V
M
A
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
www.maximintegrated.com Maxim Integrated
13
Package Information
For the latest package outline information and land patterns (foot-
prints), go to www.maximintegrated.com/packages. Note that
a “+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but the
drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
16 TSSOP-EP U16E+3 21-0108 90-0120
Ordering Information
PART TEMP RANGE PIN-PACKAGE
MAX14871EUE+ -40°C to +85°C 16 TSSOP-EP
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
www.maximintegrated.com Maxim Integrated
14
Chip Information
PROCESS: BiCMOS
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 9/14 Initial release
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
MAX14871 4.5V to 36V Full-Bridge DC Motor Driver
© 2014 Maxim Integrated Products, Inc.
15
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.

Products related to this Datasheet

IC MOTOR DRIVER 4.5V-36V 16TSSOP
Available Quantity: 1,861
Unit Price: 6.41
IC MOTOR DRIVER 4.5V-36V 16TSSOP
Available Quantity: 417
Unit Price: 6.41
EVAL KIT FOR MAX14871
Available Quantity: 1
Unit Price: 146.2
IC MOTOR DRIVER 4.5V-36V 16TSSOP
Available Quantity: 0
Unit Price: 3.62544
IC MOTOR DRIVER 4.5V-36V 16TSSOP
Available Quantity: 1,861
Unit Price: 6.41