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LTC2955 Datasheet

Linear Technology/Analog Devices

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Datasheet

LTC2955
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For more information www.linear.com/LTC2955
LT3008-3.3
VOUT
VIN
PB
ON
INT
KILL
PGD
VIN
SEL
LTC2955DDB-1
2955 TA01a
GNDTMR
EN
3.3V
1M R7
1M
2.32M
SHDN
0.1µF
8.4V
VTRIP = 5.4V
µP
POWER-FAIL
402k
Typical applicaTion
FeaTures DescripTion
Pushbutton On/Off
Controller with Automatic
Turn-On
The LTC
®
2955 is a micropower, pushbutton on/off control-
ler that manages system power by generating a clean enable
output from the supply monitor input and the debounced
pushbutton input. It features an interrupt output that
notifies the system of a pushbutton or low supply event.
When the system is ready, it may use the power kill input
to shut off power. If the pushbutton remains pressed for
more than the configurable turn-off duration, the system
power is forced off.
The supply input covers a wide range from 1.5V to 36V.
The robust pushbutton input handles wide voltage swings
of ±36V and ESD strikes to ±25kV (human body model)
without latchup or damage. A low 1.2µA supply current
maximizes battery run time. Separate versions are avail-
able for positive or negative enable polarities.
Pushbutton On/Off with Interrupt
applicaTions
n Automatic Turn-On Via Voltage Monitor Input
n Wide Input Supply Range: 1.5V to 36V
n Low Supply Current: 1.2µA
n ±25kV ESD HBM on PB Input
n ±36V Wide Input Voltage for PB Input
n Low Leakage EN Output Allows DC/DC Converter
Control (LTC2955-1)
n High Voltage EN Output Drives External P-Channel
MOSFET (LTC2955-2)
n Simple Interface Allows Graceful µP Shutdown
n Adjustable Turn-Off Timer
n 10-Lead 3mm × 2mm DFN and 8-Lead ThinSOT™
Packages
n Desktop and Notebook Computers
n GPS Devices
n Portable Instruments
n Automotive Electronics
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT and PowerPath are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
TURN ON PULSE SHORT PULSE LONG PULSE
TURNS ON STAYS ON
INTERRUPT INTERRUPT
TURNS OFF
PB
2955 TA01b
EN
INT
Automatic Turn-On with Power-Fail Indication
LTC2955
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pin conFiguraTion
absoluTe MaxiMuM raTings
VIN ............................................................. 0.3V to 40V
Input Voltages
PB ........................................................... 40V to 40V
ON ......................................................... 0.3V to 40V
SEL ........................................................ 0.3V to 40V
KILL ......................................................... 0.3V to 6V
Output Voltages
EN/EN .................................................... 0.3V to 40V
INT ........................................................... 0.3V to 6V
PGD ......................................................... 0.3V to 6V
TMR ...................................................... 0.3V to 2.7V
(Note 1)
TOP VIEW
11
DDB PACKAGE
10-LEAD (3mm × 2mm) PLASTIC DFN
INT
PGD
*EN/EN
VIN
PB
ON
KILL
TMR
SEL
GND
6
8
7
9
10
5
4
2
3
1
TJMAX = 125°C, θJA = 55°C/W
EXPOSED PAD (PIN 11) PCB GND CONNECTION OPTIONAL
*PIN 3 IS EN FOR LTC2955-1
AND IS EN FOR L
TC2955-2
1
2
3
4
8
7
6
5
TOP VIEW
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
INT
EN/EN*
VIN
PB
ON
KILL
TMR
GND
TJMAX = 125°C, θJA = 195°C/W
*PIN 7 IS EN FOR LTC2955-1
AND IS EN FOR LTC2955-2
orDer inForMaTion
Operating Temperature Range
LTC2955C ................................................ 0°C to 70°C
LTC2955I .............................................40°C to 85°C
Storage Temperature Range .................. 65°C to 150°C
Lead Temperature (Soldering, 10 sec)
TSOT-23 Package .............................................300°C
Lead Free Finish
TAPE AND REEL (MINI) TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC2955CDDB-1#TRMPBF LTC2955CDDB-1#TRPBF LGBJ 10-Lead (3mm × 2mm) Plastic DFN 0°C to 70°C
LTC2955CDDB-2#TRMPBF LTC2955CDDB-2#TRPBF LGBM 10-Lead (3mm × 2mm) Plastic DFN 0°C to 70°C
LTC2955IDDB-1#TRMPBF LTC2955IDDB-1#TRPBF LGBJ 10-Lead (3mm × 2mm) Plastic DFN –40°C to 85°C
LTC2955IDDB-2#TRMPBF LTC2955IDDB-2#TRPBF LGBM 10-Lead (3mm × 2mm) Plastic DFN –40°C to 85°C
LTC2955CTS8-1#TRMPBF LTC2955CTS8-1#TRPBF LTGBK 8-Lead Plastic TSOT-23 0°C to 70°C
LTC2955CTS8-2#TRMPBF LTC2955CTS8-2#TRPBF LTGBN 8-Lead Plastic TSOT-23 0°C to 70°C
LTC2955ITS8-1#TRMPBF LTC2955ITS8-1#TRPBF LTGBK 8-Lead Plastic TSOT-23 –40°C to 85°C
LTC2955ITS8-2#TRMPBF LTC2955ITS8-2#TRPBF LTGBN 8-Lead Plastic TSOT-23 –40°C to 85°C
TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/. Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
(http://www.linear.com/product/LTC2955#orderinfo)
LTC2955
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elecTrical characTerisTics
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Supply
VIN Supply Voltage Range l1.5 36 V
IIN VIN Supply Current l0.5 1.2 3 µA
VUVL VIN Undervoltage Lockout VIN Rising l1.0 1.15 1.3 V
VUVL(HYST) VIN Undervoltage Lockout Hysteresis l30 85 200 mV
Input Pins
VPB(MIN(MAX)) PB Voltage Range l–36 36 V
VPB PB Input Threshold PB Falling l0.6 0.8 1 V
VPB(HYST) PB Input Threshold Hysteresis (Note 3) 40 mV
VPB(VOC) PB Open Circuit Voltage I = –1µA l3.0 4.3 5.5 V
IPB PB Input Leakage Current 6V < PB < 36V
PB = 1V
PB = –36V
l
l
l
–1
–4
±10
–8
–400
µA
µA
µA
VON ON Threshold ON Rising l0.76 0.80 0.84 V
VON(HYST) ON Hysteresis DFN Package Only 40 mV
ION ON Input Leakage Current ON = 1V
ON = 36V
l
l
±10
±100
nA
nA
VKILL KILL Input Threshold Voltage KILL Falling l0.76 0.80 0.84 V
VKILL(HYST) KILL Input Threshold Hysteresis (Note 3) 30 mV
IKILL KILL Input Leakage Current KILL = 1V l±50 nA
VSEL SEL Input Threshold l0.4 0.8 1.2 V
ISEL SEL Input Current SEL = 1V
SEL = 36V
l
l
±50
±100
nA
nA
Output Pins
VEN/EN(VOL) EN/EN Voltage Output Low I = 1mA l0.175 0.4 V
VEN(VOH) EN Voltage Output High (LTC2955-1) I = 0µA, –0.5µA l1.5 5.5 V
VEN(VOH) EN Voltage Output High (LTC2955-2) I = 0µA, –0.5µA lVIN – 1.5 V
IEN EN Pull-Up Current (LTC2955-1) EN = 0V l–1.2 –2 –2.8 µA
IEN EN Pull-Up Resistance (LTC2955-2) l0.45 0.9 1.35
VINT(VOL) INT Voltage Output Low I = 3mA l0.4 V
IINT INT Leakage Current INT = 5V l±50 nA
VPGD(VOH) PGD Voltage Output High I = 0µA, –0.5µA l1.5 5.5 V
VPGD(VOL) PGD Voltage Output Low I = 3mA l0.4 V
IPGD PGD Pull-Up Current PGD = 0V l–1.2 –2 –2.8 µA
ITMR(PU) TMR Pull-Up Current TMR = 0V l–2 –3 –4 µA
ITMR(PD) TMR Pull-Down Current TMR = 1.5V l2 3 4 µA
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 7V unless otherwise noted. (Note 2)
LTC2955
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SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Timing
tDB(ON) PB, ON Turn-On Debounce Time PB Falling or ON Rising Enable Asserted l19 32 45 ms
tDB(OFF) PB Interrupt Debounce Time PB Falling INT Falling l19 32 45 ms
tTMR Additional Turn-Off Debounce Time CTMR = 2200pF l5.8 11.5 17.2 ms
tINT(MIN) Minimum INT Pulse Width INT Falling TMR Rising l19 32 45 ms
tON(PD) ON Interrupt Delay ON Falling INT Falling, VSEL > 0.8V l200 µs
tPGD(PD) PGD Propagation Delay ON Falling PGD Falling l200 µs
tKILL(PD) KILL Propagation Delay KILL Falling Enable Released l60 µs
tKILL(PW) KILL Minimum Pulse Width l60 µs
tKILL(ON BLANK) KILL Turn-On Blanking (Note 4) KILL Low, Enable Asserted Enable
Released
l304 512 720 ms
tEN(LOCK OUT) EN/EN Lockout Time (Note 5) Enable Released Enable Asserted l0.6 1 1.4 s
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 7V unless otherwise noted. (Note 2)
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: All currents into pins are positive; all voltages are referenced to
GND unless otherwise noted.
Note 3: Guaranteed by design, not subject to test.
Note 4: The KILL turn-on blanking time is the waiting period immediately
after the enable output is asserted. This blanking time allows sufficient
time for the regulator and the µP to perform power-up tasks. The KILL, PB,
and ON inputs are ignored during this period.
Note 5: The enable lockout time is the waiting period immediately after the
enable output is released. It allows an application to properly power-down
such that the next power-up sequence starts from a consistent powered
down configuration. PB and ON are ignored during this period.
Typical perForMance characTerisTics
Supply Current vs Temperature Supply Current vs Supply Voltage
Undervoltage Lockout vs
Temperature
VIN = 7V, TA = 25°C, unless otherwise noted.
TEMPERATURE (°C)
–50
V
UVL
(V)
1.10
1.12
1.14
1.20
1.16
050 75
2955 G03
1.18
–25 25 100
125
TEMPERATURE (°C)
–50
IVIN (µA)
0.8
1.0
1.1
1.2
1.6
1.3
050 75
2955 G01
0.9
1.4
1.5
–25 25 100 125
VIN (V)
0
IVIN (µA)
0.6
0.8
1.0
1.2
10 20 25
2955 G02
1.4
1.6
515 30 4035
TA = –40°C
TA = 25°C
TA = 85°C
LTC2955
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Typical perForMance characTerisTics
TMR Pull-Up Current
vs Temperature
EN Output High Voltage vs
Temperature
EN Output High Voltage vs Supply
Voltage
EN/EN Output Low Voltage vs
Temperature PB Input Current vs PB Voltage
PB Voltage vs External PB
Resistance to Ground
ON/KILL Threshold vs
Temperature
Turn-On Debounce Time
vs Temperature
Additional Turn-Off Debounce
Time vs TMR External Capacitance
VIN = 7V, TA = 25°C, unless otherwise noted.
TEMPERATURE (°C)
–50
t
DB(ON)
(ms)
30
32
31
36
33
050 75
2955 G05
35
34
–25 25 100
125
EXTERNAL PB RESISTANCE TO GROUND (kΩ)
0
0
50
100
150
200
10 20
250
4030
TA = –40°C
TA = 25°C
TA = 85°C
TEMPERATURE (°C)
–50
V
ON/KILL
(V)
0.790
0.795
0.810
0.800
050 75
2955 G04
0.805
–25 25 100
125
TEMPERATURE (°C)
–50
V
EN(VOH)
(V)
3.6
4.0
4.2
4.4
5.0
4.6
050 75
2955 G08
3.8
4.8
–25 25 100
125
TMR EXTERNAL CAPACITANCE (nF)
1
1
tTMR (ms)
100
10000
10 100 1000
2955 G06
10
1000
TEMPERATURE (°C)
–50
ITMR(PU) (µA)
–2.6
–2.8
–2.9
–3.0
–3.4
–3.1
050 75
2955 G07
–2.7
–3.2
–3.3
–25 25 100 125
VIN (V)
1
VEN(VOH) (V)
0.0
1.0
5.0
2.0
3 5
2955 G09
4.0
3.0
2476
TA = –40°C
TA = 25°C
TA = 85°C
PB VOLTAGE (V)
–40
IPB (µA)
40
–40
–80
–200
–120
0
2955 G11
0
–160
–20 20 40
TEMPERATURE (°C)
–50
VEN/EN(VOL) (mV)
50
200
150
250
300
450
350
050 75
2955 G10
100
400
–25 25 100 125
VIN = 1.5V
VIN = 7V
I = 1mA
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pin FuncTions
EN: Enable Output (LTC2955-1). EN is an active high output
to control the turn-on/off of the system power. Connect this
pin to the RUN or SHUTDOWN pin of the voltage regulator.
The LTC2955 asserts EN high when the pushbutton is
pressed or when ON goes high. The output high voltage
follows the internal LDO output which provides sufficient
margin for most SHUTDOWN pin thresholds.
EN: Inverted Enable Output (LTC2955-2). EN is an active
low output to control the turn-on/off of the system power.
It may drive a voltage regulator’s active low enable input,
or it may drive the gate of a P-channel MOSFET. In the
turn-off state, the LTC2955 pulls this pin to VIN through
an internal 900k resistor. The LTC2955 pulls EN to GND
when the pushbutton is pressed or when ON goes high.
Exposed Pad (DFN only): Exposed pad. Leave open or
connect to device ground.
GND: Device Ground.
INT: Open Drain Interrupt Output. Connect this pin to the
interrupt input of the system with a pull-up resistor to the
system supply. The LTC2955 asserts the INT pin low when
it receives the turn-off command from the pushbutton or
the ON pin. The minimum pulse width of the INT signal is
32ms and can be extended through the TMR pin.
KILL: Kill Input. A low at KILL releases the enable output
(EN/EN). This pin can be driven by the microprocessor or it
can be used as a voltage monitor input. Tie to the system
power supply or an external voltage of 1.2V~5V if unused.
ON: Monitor Input. Connect this pin to an external resistive
divider from the monitored voltage. This allows automatic
system turn-on when the monitored voltage transitions
high. For the DFN part, if the SEL pin is tied high, it also
allows automatic system turn-off when the monitored
voltage transitions low. Tie to GND if unused.
PB: Pushbutton Input. This is an active low input with a
900k pull-up to an internal LDO. Connect one terminal of
the pushbutton to this pin and connect the other terminal of
the pushbutton to GND. The pin may be left open if unused.
PGD (DFN only): ON Status Output. A high on this pin
indicates that the voltage at the ON pin is above the input
threshold of 0.8V. This pin can be used as a system input
to inform the system whether the turn-on was triggered by
the ON pin or the pushbutton pin. Leave open if unused.
SEL (DFN only): Mode Select Input. Connect SEL to GND
to block the ON pin falling edge from activating system
turn-off. Connect SEL to VIN to allow both the ON pin rising
and falling edges to activate system turn-on and turn-off
respectively. For the TSOT package, SEL is internally tied
to GND. Do not leave open.
TMR: Timer Pin. A capacitor to ground determines the
additional time (5.2 seconds/μF) beyond the default 64ms
that the pushbutton must be held low before immediately
releasing the EN/EN and INT outputs. The turn-off debounce
time defaults to 64ms if this pin is left open. To disable the
ability to force a system power-down with a pushbutton
press, ground the TMR pin.
VIN: Power Supply Input. For > 20V applications, connect
VIN to the power source through a 1k resistor and bypass
VIN to GND with a 10nF low ESR capacitor.
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block DiagraM
2955 BD
VIN
PB
ON
ON
OFF
*DFN ONLY
TMR
SEL*
GND
VLDO
REGULATOR VLDO ≈ 5.2V
VLDO
2µA
EN CONTROL
900k
0.8V
0.8V
0.8V
0.8V
KILL
INT
PGD*
+
+
+
+
OSCILLATOR
f = 1kHz
OSCILLATOR
DEBOUNCE
LOGIC
2µA
(2955-1)
EN
EN CONTROL
LTC2955-1
VIN
(2955-2)
EN
EN CONTROL
LTC2955-2
900k
VLDO
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Figure 1. Pushbutton Turn-On Timing
operaTion
Overview
The LTC2955 is a pushbutton on/off controller that man-
ages system power based on a pushbutton input (PB pin)
and a voltage monitor input (ON pin). In a typical application,
the enable output (EN/EN) turns on system power when
the pushbutton is pressed or the supply monitor detects
the presence of a primary or secondary supply such as a
wall adaptor or car battery.
After the system is powered up, a pushbutton event as-
serts the interrupt output (INT) which can be used in menu
driven applications to request for a system power-down.
A power kill input (KILL) allows a microprocessor or sys-
tem to release the enable output immediately, effectively
powering down the system. System power is also forced
off if the pushbutton remains asserted for more than the
forced turn-off activation time configurable via the TMR pin.
The LTC2955 is also designed with a blanking time after
each system turn on and off event. During this blanking
time, the LTC2955 ignores the KILL, ON and PB pins,
thus ensuring that the system stays on/off for a minimum
amount of time. This provides sufficient time for the voltage
regulator to turn on/off and allows it to charge/discharge
its output to the final voltage. It also allows the µP suf-
ficient time to perform power on/off tasks.
The PGD output indicates the status of the ON pin to allow
the system to differentiate between pushbutton turn-on
or supply plug-in events.
Turn-On Sequence and KILL Blanking Time
The LTC2955-1 asserts the EN output high if the pushbut-
ton is pressed or the ON pin goes high. This is typically
used to turn on a DC/DC converter or linear regulator.
Figure 1 shows the turn-on sequence of the LTC2955-1
initiated by the PB pin. When the button is pressed at time
t1, a high to low transition on the PB pin initiates the turn-
on sequence. The PB pin must stay low continuously for
a period of 32ms (tDB(ON)) before the LTC2955-1 asserts
the EN output high. Once EN goes high (t2), an internal
512ms blanking time (tKILL(OnBlank)) is started. During
this blanking time, the LTC2955-1 ignores the KILL, ON
and PB pins and keeps EN high for at least 512ms. This
provides sufficient time for the voltage regulator to turn
on and charge its output to the final voltage and allows
the µP enough time to perform power on tasks. The µP
must pull the KILL pin high during this 512ms blanking
time, or else EN will go low at the end of this time (t3).
tDB(ON) tKILL(ON BLANK)
PB AND KILL IGNORED
PB
2955 F01
EN
(LTC2955-1)
t1t2t3
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Figure 2.ON Pin Turn-On Timing
Figure 3. Pushbutton Turn-Off Timing
operaTion
At the end of this blanking time, the LTC2955-1 will check
that the PB pin is high. If the PB pin remains low, it will be
ignored until a high is detected on the pin. The next low
on the PB pin will initiate a turn-off sequence.
Figure 2 shows a similar LTC2955-1 turn-on sequence
with the ON pin going high. The timing sequence is very
similar to that initiated by the pushbutton. The PGD output
follows the ON pin.
PB Pin Turn-Off Sequence
Figure 3 shows the turn-off sequence of the LTC2955-1
initiated through the PB pin. A turn-off sequence refers
to the LTC2955-1 releasing the EN output. This turns off
the voltage regulator.
A high to low transition on PB (t1) starts the turn-off
sequence. In order to assert INT (interrupt output) low,
PB must stay low continuously for 32ms (tDB(OFF)). At
the end of the 32ms (t2), the INT pin is asserted low and
will stay low for at least 32ms (tINT(MIN)), even if the PB
pin goes high during this period (t2 to t4). When the µP
receives this interrupt signal, it should start to perform
its power-down functions and assert KILL low (t3) once
it is done. The LTC2955-1 will then release INT and pull
EN low, thus turning off the system power, as shown with
dotted lines in Figure 3.
The user can also force the system to power-down if the
µP fails to respond to the interrupt signal (KILL pin remains
16 CYCLES
KILL
TMR
tDB(OFF)
PB
IGNORED
PB
IGNORED
PB
tEN(LOCKOUT)
tTMR
tINT(MIN)
INT
EN
(LTC2955-1)
2955 F03
t1t2t3t4t5t6t7
IGNORED
tDB(ON) tKILL(ON BLANK)
ON AND KILL IGNORED
ON
t
1
t
2
t
3
2955 F02
EN
(LTC2955-1)
PGD
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operaTion
the PB and ON inputs are ignored. This is to allow time for
the voltage regulator to turn off and for its output to decay
to 0V. This ensures that the µP has completely powered
down before it is allowed to restart. After the one second
lockout time, the LTC2955-1 proceeds to the next stage
to wait for a turn-on command and the cycle will repeat
as above. If the PB pin remains low after the EN output
goes low, the LTC2955-1 will delay the start of this lockout
time until the PB pin goes high.
If the PB pin goes high when the external timer is still
counting, as shown in Figure 4, the turn-off sequence will
be aborted. The INT pin is forced high immediately and
the EN pin remains high.
high). This can be done by holding the pushbutton down
for a long period (> tDB(OFF) + tINT(MIN) + tTMR) as shown
with the solid lines in Figure 3. If the PB pin remains low at
the end of the 32ms minimum INT pulse width (tINT(MIN)),
the external timer will start counting (t4).
The capacitance at the TMR pin determines the duration
of this timer and it will count for 16 cycles (tTMR). If the
PB pin remains low at the end of the 16 cycles (t5), the
LTC2955-1 will force the EN pin low and the INT pin high.
See Applications Information for adjusting tTMR.
After the EN output goes low and the PB pin goes high,
the LTC2955-1 starts the one second lockout time
(tEN(LOCKOUT)). During this lockout time (t6 to t7 in Figure 3)
Figure 4. Pushbutton Turn-Off Aborted
tDB(OFF)
PB IGNORED
t < tTMR
PB
TMR
tINT(MIN)
2955 F04
INT
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ON Pin Turn-Off Sequence (DFN Package Only)
Figure 5 shows the turn-off sequence of the LTC2955-1
initiated by the ON pin. The timing sequence is slightly
different from that by the pushbutton as there is no de-
bounce time (tDB(OFF)) before the INT pin pulls low. The
ON pin falling edge can start the turn-off sequence only
if the following two conditions are met: (1) The preceding
turn-on sequence was initiated by the ON pin rising edge,
and (2) The SEL pin must be tied high (>0.8V). For TS8
package, the ON pin falling edge is ignored.
In Figure 5, a high to low transition at ON (t1) starts the
turn-off sequence. The interrupt output (INT) is asserted
immediately when the ON pin goes low. Unlike the PB
pin turn-off sequence, there is no 32ms debounce time
(tDB(FF)) for the ON pin going low. This allows the system
to initiate a shutdown as soon as the monitored supply is
removed and allows the µP the maximum amount of time
to perform power-down functions. The INT pin will stay
low for at least 32ms (tINT(MIN)). When the µP receives
this interrupt signal, it should start to perform its power-
down functions and assert the KILL input low (t2) once it
is done. The LTC2955-1 will then release the EN and INT
outputs, thus turning off the system power, as shown with
dotted lines in Figure 5.
If the µP fails to respond (KILL pin remains high, as shown
with solid line in Figure 5) and the ON pin remains low 32ms
after INT goes low, the external timer will start counting
for 16 cycles (tTMR, t3 to t4). If the ON pin remains low
at the end of the 16 cycles (t4), the LTC2955-1 will force
the EN pin low and the INT pin high. See Applications
Information for adjusting tTMR.
After the EN output goes low, the LTC2955-1 starts the
one second lockout time (tEN(LOCKOUT)). During this lockout
time (t4 to t5), the PB and ON inputs are ignored.
operaTion
Figure 5. ON Pin Turn-Off Timing (DFN Only, VSEL > 1.2V and the Preceding Turn-On Sequence Was
Initiated by the ON Pin Rising Edge
16 CYCLES
ON
t1t2t5
t4
t3
TMR
tINT(MIN)
tTMR
tEN(LOCKOUT)
INT
PGD
EN
(LTC2955-1)
2955 F05
KILL IGNORED
IGNORED
LTC2955
12
2955fa
For more information www.linear.com/LTC2955
operaTion
PB vs ON Pin
With the DFN package, if the turn-on sequence is initi-
ated by the pushbutton, the ON input is ignored until the
pushbutton is pressed again to initiate a turn-off sequence.
As shown in Figure 6, the PB pin initiates a turn-on sequence
at time t1 before the ON pin goes high at time t2. Once EN
goes high (t3), the ON input is ignored, so a falling edge
at the ON pin (t4) will not initiate a turn-off sequence even
if the SEL pin is high. This allows the system to remain
powered up if it is plugged in and out of a secondary power
source while the system is already turned on.
If the turn-on sequence is initiated by the ON pin, both
the pushbutton and the ON pin falling edge can initiate
the turn-off sequence. For the TS8 package, ON pin falling
edge is always ignored regardless of which pins initiate
the turn-on.
The PB pin has priority over the ON pin, so if the PB pin
goes low and ON pin goes high at the same time, the
LTC2955-1 will monitor the PB pin for the 32ms debounce
time and ignore the ON pin unless the PB pin bounces
during the 32ms.
ON Pin Initial Turn-On
If the LTC2955-1 powers up with the ON pin already high,
the EN pin will go high after a power-up delay of about
one second. Subsequently, if the pushbutton is pressed
to force EN low, the LTC2955-1 will not initiate another
turn-on even if the ON pin remains high. The LTC2955-1
needs a rising edge at the ON pin or a falling edge on the
PB pin to initiate the subsequent turn-on.
Figure 6. Pushbutton Is Pressed Before the ON Pin Goes High
TURN-ON BY PB
PB PIN
PGD PIN
ON PIN
ON GOING LOW IS IGNORED,
SINCE THE EN IS ASSERTED
BY THE PUSHBUTTON
ON PIN IS IGNORED, SINCE
PUSHBUTTON IS PRESSED
FIRST
EN PIN
2955 F06
t1t2t3t4t5
LTC2955
13
2955fa
For more information www.linear.com/LTC2955
operaTion
As shown in Figure 7, if the ON pin is high when power is
first applied to the LTC2955-1 at time t1, the EN pin will
go high (at t2) after the one second EN lockout time. At
time t3, the pushbutton is pressed to activate turn-off
while the ON pin remains high. The LTC2955-1 will wait
for a rising edge at the ON pin or a low at the PB pin to
activate the next turn-on. As shown at time t4, after the
one second lockout time, the EN stays low with ON high.
At time t5, only the rising edge of the ON pin or a PB event
will trigger the next turn-on again.
LTC2955-1, LTC2955-2 Versions
The LTC2955-1 and LTC2955-2 differ only by the polarity
of the high voltage (36V absolute maximum) enable pin.
The LTC2955-1 EN pin is a high true output designed to
drive the SHUTDOWN pin of most voltage regulators. In
turn-on mode, this pin is pulled high by a pull-up current of
2µA powered by an internal LDO, which gives a high level
output voltage (VOH) of typically 4.3V. In turn-off mode,
this pin is pulled low by an internal N-channel MOSFET. If
a higher VOH or higher pull-up current is required, connect
the EN pin to an external source through a pull-up resistor.
The LTC2955-2 EN pin is a low true enable output designed
to drive the gate of an external P-channel MOSFET. In
turn-on mode, the EN pin is pulled low by an internal
N-channel MOSFET. In turn-off mode, this pin is pulled
high to VIN through an internal 900k resistor. An external
pull-up resistor can be connected between this pin and
VIN to increase the pull-up current.
Figure 7. Power First Applied to LTC2955-1
TURN-ON BY ON
RISING EDGE
TURN-OFF BY
PUSHBUTTON
ON PIN
PB PIN
VIN A HIGH AT ON PIN IS IGNORED AFTER
THE FIRST TURN-ON/OFF SEQUENCE ON RISING EDGE
POWER FIRST APPLIED TO
LTC2955 VIN PIN
EN PIN
2955 F07
t1t2t3t4t5
TURN-ON BY ON
HIGH LEVEL
tEN(LOCKOUT) tEN(LOCKOUT)
LTC2955
14
2955fa
For more information www.linear.com/LTC2955
applicaTions inForMaTion
Adjusting the Forced Turn-Off Timing
The LTC2955 allows the user to force the system power to
turn off if the µP fails to respond during fault conditions. As
shown by the solid lines in Figure 3 and Figure 5, when the
µP fails to bring the KILL pin low after the interrupt signal
is asserted, the user can force a turn-off by holding down
the pushbutton. The length of time that PB must be held
low is given by a fixed 64ms delay (tDB(OFF) + tINT(MIN))
plus an adjustable power-down timer delay (tTMR). The
adjustable delay is set by placing an optional external
capacitor on the TMR pin. Use the following equation to
calculate the capacitance for the desired delay. CTMR is
the external capacitor at the TMR pin:
CTMR = 0.19 • tTMR [µF/sec]
As an example, if the required turn-off debounce time is
one second:
tTMR = (1000ms – 64ms)
CTMR = 0.19 • 0.936
Required CTMR is 0.178µF
The ON pin turn-off debounce time is 32ms less than the
PB pin debounce time since there is no tDB(OFF). If the
TMR pin is left open, the turn-off debounce time defaults
to 64ms for the PB pin and 32ms for the ON pin.
Voltage Monitoring with KILL Input
The KILL pin can also be used as a voltage monitor input.
Figure 8 shows an application where the KILL pin has a dual
function. It is driven by a low leakage open drain output
of the µP. It is also connected to a resistive divider that
monitors battery voltage (VIN). When the battery voltage
falls below the set value, the voltage at the KILL pin falls
below 0.8V and the EN pin is quickly pulled low. Note that
the resistor values should be as large as possible, but
small enough to keep leakage currents from tripping the
0.8V KILL comparator.
Operation Without µP
If there is no circuitry available to drive the KILL pin,
this pin can be connected to a voltage regulator output
through a resistive divider or RC network as shown in
Figure 9. The KILL pin acts as a voltage monitor pin that
shuts down the regulator when its output voltage drops
below a certain level.
The minimum pulse width needed to trigger KILL is 30µs.
If there are glitches on the resistor pull-up voltage that
are wider than 30µs and transition below 0.8V, then an
appropriate bypass capacitor should be connected to the
KILL pin.
Figure 8. Input Voltage Monitoring with KILL Input
Figure 9. Application without µP
*OPTIONAL
PB
INT
KILL
VIN
LTC2955TS8-1
GND TMR
CTMR*
F
ON
EN
C4
0.1µF
VIN = 9V
2955 F09
R1
10k
VOUT
VIN VOUT
LT3060
SHDN
C3*
0.01µF
+
*OPTIONAL
PB
INT
KILL
VIN
LTC2955TS8-1
GND TMR
CTMR*
F
ON
EN
C4
0.1µF
R3
583k
1%
VIN = 9V
R2
100k
1%
2955 F08
µP
R1
10k
KILL
(OPEN DRAIN)
INT
VOUT
VIN VOUT
LT3060
SHDN
LTC2955
15
2955fa
For more information www.linear.com/LTC2955
VTH = 0.8V INPUT
*OPTIONAL
2955 F10
PB
INT
KILL
VIN
LTC2955TS8-2
R4
100k
1%
GND TMR
CTMR*
0.033µF
EN
VOUT
VOUT,TRIP POINT = 6V
ON
C4
0.1µF
R1
649k
1%
R9
100k
M1
R5*
100k
C3*
0.1µF
OPTIONAL GLITCH
FILTER CAPACITOR
4.2V
SINGLE CELL
Li-ION BATTERY
+
4.2V
SINGLE CELL
Li-ION BATTERY
+
High Voltage PowerPath™ Switching
The high voltage EN open drain output of the LTC2955-2
is designed to switch on/off an external power P-channel
MOSFET. This allows a user to connect/disconnect a power
supply (or battery) to its load by toggling the PB pin. Figure 10
shows the LTC2955-2 controlling a two cell Li-Ion battery
application. The KILL pin is connected to the output of the
external MOSFET through a resistive divider. The KILL pin
serves as a voltage monitor. When VOUT drops below 6V,
the EN pin is pulled high (to VIN) after 15µs later. R9 slows
down the turning on of M1 so as to limit the inrush current
when M1 turns on to charge up the capacitor at VOUT. R5
helps to speed up the turning off of M1 and also to keep
M1 off when the input voltage rise time is fast.
PB Pin in a Noisy Environment
The rugged PB pin is designed to operate in noisy environ-
ments. Transients below ground and above VIN (36V <
VIN < 36V) will not damage the rugged PB pin. Additionally,
the PB pin can withstand ESD HBM strikes of up to ±25kV.
However, if the pushbutton switch is located physically far
from the LTC2955 PB pin, the parasitic capacitance and
parasitic series inductance of the connecting cable or PCB
trace can create problems. The parasitic capacitance can
couple external noise onto the PB input; placing a 0.1µF
capacitor at the pin lessens the impact of this coupling.
The parasitic series inductance may cause unpredictable
ringing at the PB pin; placing a 5.1k resistor from the PB
pin to the pushbutton switch reduces this ringing. Figure 11
shows an example of this RC network at the PB pin.
External Pull-Up Resistor on PB Pin
An internal 900k pull-up resistor on the PB pin makes an
external pull-up resistor unnecessary. Leakage current on
the PB board trace, however, will affect the open circuit
voltage on the PB pin. If the leakage is too large (>1µA),
the PB voltage may fall close to the threshold window. To
applicaTions inForMaTion
Figure 10. PowerPath Control with 6V Undervoltage Detect
Figure 11. Noisy PB Trace
DETAILS OMITTED
FOR CLARITY
PB INT
KILL
VIN
LTC2955-1
GND TMR
EN
C5
0.1µF
R6
5.1k
TRACE
CAPACITANCE
PARASITICS
TRACE
INDUCTANCE
NOISE
VIN
2955 F11
LTC2955
16
2955fa
For more information www.linear.com/LTC2955
mitigate the effect of the board leakage, a 10k resistor to
VIN is recommended (see Figure 12).
applicaTions inForMaTion
Enhancing VIN Ruggedness
Placing a 1k resistor and a 10nF capacitor at the VIN pin
can be used to enhance ruggedness in some applications.
A 1k resistor in series with the VIN pin allows the LTC2955
to withstand reverse-input voltages. The LTC2955’s VIN pin
is internally clamped to one diode voltage below ground.
In battery operated applications where a battery could be
inserted improperly, this resistor will limit the current and
allow internal clamping to protect the pin.
Figure 12. External Pull-Up Resistor on PB Pin
Figure 13. Enhancing VIN Ruggedness
Figure 14. Using a Slide Switch to Prevent Accidental
Turn-On/Off
Figure 15. Using a Slide or Toggle Switch to Turn-On/Off
Adding a 10nF capacitor in addition to the 1k resistor can
protect against high voltage input transients that would
exceed the 40V Absolute Maximum Voltage rating of the
VIN pin. These could occur during hot-plugging into a
battery or AC adapter. This can also protect against tran-
sients that may appear on the PCB ground during large
ESD strikes at the PB pin.
The maximum operating current of the LTC2955 is less
than 3µA, creating an insignificant voltage drop across
the resistor. Using a capacitor value of 10nF provides
sufficient filtering for most applications and larger values
can actually diminish its effectiveness.
Applications with Slide Switch
In some applications, to prevent accidental toggling of the
system power, a slide switch is preferred over a pushbut-
ton. Figure 14 shows a slide switch added in series with
the pushbutton. The user can slide the switch open to
activate the HOLD/LOCK function, where the pushbutton
is disabled. Figure 15 shows a slide switch connected to
the LTC2955 ON pin resistive divider. If the user slides
the switch to the ON position, the LTC2955 ON pin is high
*OPTIONAL
PB
INT
KILL
ON
VIN
LTC2955TS8-1
GND TMR
CONT*
0.033µF
EN
C4
10nF
R8
1k
9V
BATTERY
2955 F13
µP
R1
10k
KILL
INT
VIN VOUT
LT3060
SHDN
+
PINS OMITTED
FOR CLARITY
EXTERNAL BOARD
LEAKAGE CURRENT
R7
10k
IF EXTERNAL PARASITIC BOARD
LEAKAGE >2µA USE EXTERNAL
PULL-UP RESISTOR
PB
VIN
VIN
900k
VLDO
LTC2955-1/
LTC2955-2
GND
0.8V
>2µA
2955 F12
NORMAL
HOLD/LOCK
PB
VIN
VIN
ON
SEL
LTC2955DDB-1
GND
EN
2955 F14
PB
VIN
V
IN
SEL
ON
LTC2955DDB-1
GND
OFF
ON
EN
2955 F15
LTC2955
17
2955fa
For more information www.linear.com/LTC2955
applicaTions inForMaTion
If a higher VEN(VOH) is required, an external pull-up resistor
can be connected from the EN pin to any higher voltage
(<36V). The EN pin is designed to be able to sink at least
1mA of current during turn-off, so this external pull-up
resistor value must be selected to source less than 1mA
with EN at 0V.
The LTC2955-1 EN pin can also be connected to switching
regulators with a RUN/SS pin. RUN/SS has a dual func-
tion of a SHUTDOWN threshold and soft-start, with an
internal soft-start pull-up current and an external soft-start
capacitor. The LTC2955 EN pin pull-up current of 2µA will
add to the soft-start pull-up current of the regulator. The
and the device turns on. If the user slides the switch to
the OFF position, the ON pin voltage drops to 0V and the
LTC2955 activates a turn-off since the SEL pin is high
(DFN package only).
Interface with Switching Regulators
The LTC2955-1 EN pin can be connected directly to most
switching regulator SHUTDOWN inputs. The EN pin high
level output voltage (VEN(VOH)) is typically 4.3V with
VIN >5V, and VEN(VOH) = VIN – 0.5V if VIN <5V. With a
minimum VIN of 1.5V, VEN(VOH) is still higher than most
SHUTDOWN thresholds (usually <1.2V). Figure 16 shows
one such application. The regulator is a boost converter
with a SHUTDOWN high threshold of 0.88V (maximum).
Figure 16. 2-Cell with 3.3V Output
Figure 17. Turn-On/Off a DC/DC Regulator Through the
RUN/SS Pin
Figure 18. Recommended Layout for the VIN Bypass
Capacitor
LTC3528
VOUT
FB
VIN
PGOOD
SHDN
VIN
PB
INT
KILL
VIN TMR
LTC2955TS8-1
2955 F16
499k
GND
ON
EN
VOUT
3.3V
0.4A
287k
GND
SW
4.7µF
1.5V TO 3.2V
1M
22pF
22µF
4.7µH
DC/DC
VOUT
RUN/SS VOUT
GND
CSS
COUT
VIN
VIN
PB
INT
VIN
LTC2955TS8-1
2955 F17
µP
1M
GND
ON
EN
TMR
KILL
CIN
soft-start capacitor may need to be increased to maintain
the same soft-start time. The soft-start behavior of the
regulator will remain the same.
Figure 17 shows the LTC2955-1 EN pin connected to a
DC/DC regulator RUN/SS pin.
Layout Considerations
Figure 18 shows example PCB layouts for placing the VIN
pin bypass capacitor. Position the bypass capacitor close
to the LTC2955 on the same side of the PCB and keep the
traces short. For the DFN package, a PCB via should be
placed near the LTC2955 to connect the PB pin (Pin 5)
to the pushbutton. This allows an unbroken trace to be
placed between the VIN pin and the bypass capacitor.
Placing the bypass capacitor close to the LTC2955 gives
the optimum protection against PB pin ESD transients.
2955 F18
GND
CVIN
LTC2955DDB
11
6
8
7
9
10
5
4
2
3
1
V
IN
VIN
1
2
3
4
8
7
6
5
LTC2955TS8
GND
CVIN
LTC2955
18
2955fa
For more information www.linear.com/LTC2955
Typical applicaTions
Low Voltage Pushbutton Controller Enables Charge Pump Automatic Power-Up with Pushbutton On/Off
PowerPath Control with Immediate KILL
LTC3204-3.3
VOUT
C+
C
VIN
GND
PB
INT
KILL
VIN
LTC2955TS8-1
2955 TA02
µP
1M
GND ONTMR
EN
2.2µF
3.3V
SHDN
2.2µF
1.8V
LT1763-5
VOUT
VIN
PB
INT
KILL
PGD
TMR
VIN
ON
LTC2955DDB-1
2955 TA03
µP
1M
GNDSEL
EN
*OPTIONAL RC NETWORK RECOMMENDED TO IMPROVE NOISE IMMUNITY
SHDN
F
12V
0.1µF*
5.1k*
LT3009
VOUT
VIN
PB
KILL
INT
VIN
LTC2955TS8-2
2955 TA04
1M
GND ONTMR
EN
3.3V
100k
SHDN
0.1µF
12V
LTC2955
19
2955fa
For more information www.linear.com/LTC2955
package DescripTion
Please refer to http://www.linear.com/product/LTC2955#packaging for the most recent package drawings.
2.00 ±0.10
(2 SIDES)
NOTE:
1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
0.40 ±0.10
BOTTOM VIEW—EXPOSED PAD
0.64 ±0.05
(2 SIDES)
0.75 ±0.05
R = 0.115
TYP
R = 0.05
TYP
2.39 ±0.05
(2 SIDES)
3.00 ±0.10
(2 SIDES)
15
106
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.200 REF
0 – 0.05
(DDB10) DFN 0905 REV Ø
0.25 ±0.05
0.50 BSC
PIN 1
R = 0.20 OR
0.25 × 45°
CHAMFER
0.25 ±0.05
2.39 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.64 ±0.05
(2 SIDES)
1.15 ±0.05
0.70 ±0.05
2.55 ±0.05
PACKAGE
OUTLINE
0.50 BSC
DDB Package
10-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1722 Rev Ø)
LTC2955
20
2955fa
For more information www.linear.com/LTC2955
Please refer to http://www.linear.com/product/LTC2955#packaging for the most recent package drawings.
1.50 – 1.75
(NOTE 4)
2.80 BSC
0.22 – 0.36
8 PLCS (NOTE 3)
DATUM ‘A
0.09 – 0.20
(NOTE 3)
TS8 TSOT-23 0710 REV A
2.90 BSC
(NOTE 4)
0.65 BSC
1.95 BSC
0.80 – 0.90
1.00 MAX 0.01 – 0.10
0.20 BSC
0.30 – 0.50 REF
PIN ONE ID
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
3.85 MAX
0.40
MAX
0.65
REF
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
1.4 MIN
2.62 REF
1.22 REF
package DescripTion
LTC2955
21
2955fa
For more information www.linear.com/LTC2955
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibilit y is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
revision hisTory
REV DATE DESCRIPTION PAGE NUMBER
A 04/16 Clarified requirements for turn-on 4, 12
LTC2955
22
2955fa
For more information www.linear.com/LTC2955
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
LINEAR TECHNOLOGY CORPORATION 2012
LT 0416 REV A • PRINTED IN USA
(408) 432-1900 FAX: (408) 434-0507 www.linear.com/LTC2955
relaTeD parTs
Typical applicaTion
PART NUMBER DESCRIPTION COMMENTS
LTC2900 Programmable Quad Supply Monitor Adjustable RESET, 10-Lead MSOP and 3mm × 3mm DFN Packages
LTC2904/LTC2905 Pin-Programmable Dual Supply Monitors Adjustable RESET and Tolerance, 8-Lead SOT-23 and 3mm × 2mm DFN Packages
LTC2909 Precision Triple/Dual Input UV, OV and
Negative Voltage Monitor
6.5V Shunt Regulator for High Voltage Operation
LTC2910 Octal Positive/Negative Voltage Monitor Eight Adjustable Inputs (0.5V)
LTC2914 Quad UV/OV Positive/Negative Voltage
Monitor
Adjustable UV and OV Trip Values
LTC2950/LTC2951 Pushbutton On/Off Controllers High Voltage, Low Power Pushbutton Controllers with Power-Down Fault Detect KILL
Timer
LTC2952 Pushbutton PowerPath Controller with
Supervisor
Automatic Low Loss Switchover Between DC Sources
LTC2953 Pushbutton Controller with Voltage
Monitoring
Adjustable Supply Monitor with 200ms Reset
LTC2954 Pushbutton On/Off Controller with µP
Interrupt
Adjustable Turn On/Off Timers
LTC4411 2.6A Low Loss Ideal Diode in ThinSOT No External MOSFET, Automatic Switching Between DC Sources
LTC4412HV Power Path Controller in ThinSOT Efficient Diode-ORing, Automatic Switching Between DC Sources, 3V to 36V
LTC4055 USB Power Controller and Li-Ion Charger Automatic Switchover, Charges 1-Cell Li-Ion Batteries
LTC4352 Ideal Diode Controller with Monitoring Controls N-Channel MOSFET, OV to 18V Operation
9.6V THRESHOLD
P-CHANNEL
MOSFET
PB
PGD
INT
KILL
VIN
SEL
ON
TMR
LTC2955DDB-1
2955 TA05
µP
1M
2.21M
200k
33nF
12V
4.5V
GND
EN
SHDN
LT3009-3.3
LTC4412
GATE
SENSE
STAT
VIN
GND
CTL
Pushbutton On/Off Control with Automatic Turn-On
When 12V Applied

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