LTC2954 Datasheet

Linear Technology/Analog Devices

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Datasheet

LTC2954
1
2954fb
Pushbutton On/Off
Controller with µP Interrupt
The LTC
®
2954 is a pushbutton on/off controller that
manages system power via a pushbutton interface. An
enable output toggles system power while an interrupt
output provides debounced pushbutton status. The inter-
rupt output can be used in menu driven applications to
request a system power-down. A power kill input allows
a microprocessor or system to reset the enable output,
effectively powering down the system. Independently
adjustable on and off timers allow dependable pushbutton
control of the enable output and resistance to accidental
toggling of system power.
The LTC2954 operates over a wide 2.7V to 26.4V input volt-
age range to accommodate a wide variety of input power
supplies. Very low quiescent current (6μA typical) makes
the LTC2954 ideally suited for battery powered applications.
Two versions of the part are available to accommodate
either positive or negative enable polarities.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
n Pushbutton PowerPath™ Control
n Portable Instrumentation Meters
n Blade Servers
n Portable Customer Service PDA
n Desktop and Notebook Computers
n Adjustable Power On/Off Timers
n Low Supply Current: 6μA
n Wide Operating Voltage Range: 2.7V to 26.4V
n Low Leakage EN Output (LTC2954-1) Allows DC/DC
Converter Control
n High Voltage EN Output (LTC2954-2) Allows Circuit
Breaker Control
n Simple Interface Allows Graceful μP Shutdown
n High Input Voltage PB Pin with Internal Pull-Up
Resistor
n ±10kV ESD HBM on PB Input
n Accurate 0.6V Threshold on KILL Comparator Input
n 8-Pin 3mm × 2mm DFN and ThinSOT™ Packages
TYPICAL APPLICATION
FEATURES DESCRIPTION
APPLICATIONS
Pushbutton On/Off with Interrupt
VIN VOUT
EN
INT
KILL
INT
KILL
LTC2954-2
ONT PDT
DC/DC
μP/μC
9V
10k
tPDT = 6.4 SECONDS
100k 100k
2954 TA01a
F
PB
GND
VIN
+
TURN-ON PULSE
TURNS ON STAYS ON
INTERRUPT INTERRUPT
TURNS OFF
SHORT PULSE LONG PULSE
PB
INT
2954 TA01b
EN
LTC2954
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Supply Voltage (VIN) .................................. 0.3V to 33V
Input Voltages
PB ............................................................ 6V to 33V
ONT ...................................................... 0.3V to 2.7V
PDT ....................................................... 0.3V to 2.7V
KILL ......................................................... 0.3V to 7V
Output Voltages
INT ......................................................... 0.3V to 10V
EN/EN .................................................... 0.3V to 33V
(Note 1)
Operating Temperature Range
LTC2954C-1 ............................................. 0°C to 70°C
LTC2954C-2 ............................................. 0°C to 70°C
LTC2954I-1 ..........................................40°C to 85°C
LTC2954I-2 ..........................................40°C to 85°C
Storage Temperature Range
DFN Package ..................................... 65°C to 125°C
TSOT-23 .............................................65°C to 150°C
Lead Temperature (Soldering, 10 sec) ...................300°C
ABSOLUTE MAXIMUM RATINGS
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC2954CDDB-1#PBF LTC2954CDDB-1#TRPBF LCJG 8-Lead (3mm × 2mm) Plastic DFN 0°C to 70°C
LTC2954CDDB-2#PBF LTC2954CDDB-2#TRPBF LCNJ 8-Lead (3mm × 2mm) Plastic DFN 0°C to 70°C
LTC2954IDDB-1#PBF LTC2954IDDB-1#TRPBF LCJG 8-Lead (3mm × 2mm) Plastic DFN –40°C to 85°C
LTC2954IDDB-2#PBF LTC2954IDDB-2#TRPBF LCNJ 8-Lead (3mm × 2mm) Plastic DFN –40°C to 85°C
LTC2954CTS8-1#PBF LTC2954CTS8-1#TRPBF LTCJH 8-Lead Plastic TSOT-23 0°C to 70°C
LTC2954CTS8-2#PBF LTC2954CTS8-2#TRPBF LTCNK 8-Lead Plastic TSOT-23 0°C to 70°C
LTC2954ITS8-1#PBF LTC2954ITS8-1#TRPBF LTCJH 8-Lead Plastic TSOT-23 –40°C to 85°C
LTC2954ITS8-2#PBF LTC2954ITS8-2#TRPBF LTCNK 8-Lead Plastic TSOT-23 –40°C to 85°C
LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC2954CDDB-1 LTC2954CDDB-1#TR LCJG 8-Lead (3mm × 2mm) Plastic DFN 0°C to 70°C
LTC2954CDDB-2 LTC2954CDDB-2#TR LCNJ 8-Lead (3mm × 2mm) Plastic DFN 0°C to 70°C
LTC2954IDDB-1 LTC2954IDDB-1#TR LCJG 8-Lead (3mm × 2mm) Plastic DFN –40°C to 85°C
LTC2954IDDB-2 LTC2954IDDB-2#TR LCNJ 8-Lead (3mm × 2mm) Plastic DFN –40°C to 85°C
LTC2954CTS8-1 LTC2954CTS8-1#TR LTCJH 8-Lead Plastic TSOT-23 0°C to 70°C
LTC2954CTS8-2 LTC2954CTS8-2#TR LTCNK 8-Lead Plastic TSOT-23 0°C to 70°C
LTC2954ITS8-1 LTC2954ITS8-1#TR LTCJH 8-Lead Plastic TSOT-23 –40°C to 85°C
LTC2954ITS8-2 LTC2954ITS8-2#TR LTCNK 8-Lead Plastic TSOT-23 –40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/
TOP VIEW
DDB PACKAGE
8-LEAD (3mm s 2mm) PLASTIC DFN
5
6
7
8
9
4
3
2
1GND
ONT
PB
VIN
INT
EN/EN
PDT
KILL
TJMAX = 125°C, θJA = 165°C/W
EXPOSED PAD (PIN 9) PCB GND CONNECTION OPTIONAL
VIN 1
PB 2
ONT 3
GND 4
8 KILL
7 PDT
6 EN/EN
5 INT
TOP VIEW
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
TJMAX = 125°C, θJA = 140°C/W
PIN CONFIGURATION
LTC2954
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The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 2.7V to 26.4V, unless otherwise noted. (Note 2)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Supply Voltage Range Steady State Operation l2.7 26.4 V
IIN VIN Supply Current System Power-On, VIN = 2.7V to 24V l612 μA
VUVL VIN Undervoltage Lockout VIN Falling l2.2 2.3 2.5 V
VUVL(HYST) VIN Undervoltage Lockout
Hysteresis
50 400 700 mV
Pushbutton, Enable (PB, EN/EN))
VPB(MIN, MAX) PB Voltage Range Single-Ended l–1 26.4 V
IPB PB Input Current 2.5V < VPB < 26.4V
VPB = 1V
VPB = 0.6V
l
l
l
–1
–3
–6
–9
±1
–12
–15
μA
μA
μA
VPB(VTH) PB Input Threshold PB Falling l0.6 0.8 1 V
VPB(VOC) PB Open Circuit Voltage IPB = –1μA 1 1.6 2 V
tEN,LOCKOUT EN/EN Lockout Time (Note 5) Enable Released Enable Asserted l200 256 325 ms
IEN(LKG) EN/EN Leakage Current VEN/
EN = 1V, Sink Current Off
VEN/
EN = 26.4V, Sink Current Off
l
l
±0.1
±1
μA
μA
VEN(VOL) EN/EN Voltage Output Low IEN/
EN = 500μA l0.11 0.4 V
Power-On Timing Pin (ONT)
IONT(PU) ONT Pull-Up Current VONT = 0V l–2.4 –3 –3.6 μA
IONT(PD) ONT Pull-Down Current VONT = 1.3V l2.4 3 3.6 μA
tDB, ON Internal Turn-On Debounce Time ONT Pin Float, PB Falling Enable Asserted l26 32 41 ms
tONT Additional Adjustable Turn-On Time CONT = 1500pF l9 11.5 13.5 ms
Power-Down Timing Pin (PDT)
IPDT(PU) PDT Pull-Up Current VPDT = 0V l–2.4 –3 –3.6 μA
IPDT(PD) PDT Pull-Down Current VPDT = 1.3V l2.4 3 3.6 μA
tDB,OFF Turn-Off Interrupt Debounce Time PB Falling INT Falling l26 32 41 ms
tPD,MIN Internal PB Power-Down Debounce
Time (Note 4) PDT Pin Float, PB Falling Enable Released l52 64 82 ms
tPDT Additional Adjustable PB
Power-Down Debounce Time
CPDT = 1500pF l9 11.5 13.5 ms
tINT,MIN Minimum INT Pulse Width INT Asserted INT Released l26 32 41 ms
tINT,MAX Maximum INT Pulse Width CPDT = 1500pF, INT Asserted INT Released l35 43.5 54.5 ms
μP Handshake Pins (INT, KILL)
IINT(LKG) INT Leakage Current VINT = 3V l±1 μA
VINT(VOL) INT Output Voltage Low IINT = 3mA l0.11 0.4 V
VKILL(TH) KILL Input Threshold Voltage KILL Falling l0.57 0.6 0.63 V
VKILL(HYST) KILL Input Threshold Hysteresis l10 30 50 mV
IKILL(LKG) KILL Leakage Current V
KILL = 0.6V l±0.1 μA
t
KILL(PW) KILL Minimum Pulse Width l30 μs
t
KILL(PD) KILL Propagation Delay KILL Falling Enable Released l30 μs
t
KILL,ON BLANK KILL Turn-On Blanking (Note 3) KILL = Low, Enable Asserted Enable Released l400 512 650 ms
ELECTRICAL CHARACTERISTICS
LTC2954
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Supply Current vs Temperature
Turn-On Debounce Time (tDB, ON +
tONT) vs ONT External Capacitance
Supply Current vs Supply Voltage
ONT Pull-Up Current
vs Temperature
Turn-Off Debounce Time (tDB, OFF)
vs VIN
Internal Default Turn-On
Debounce Time (tDB, ON) vs VIN
TYPICAL PERFORMANCE CHARACTERISTICS
ELECTRICAL CHARACTERISTICS
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: The KILL turn-on blanking timer period is the waiting period
immediately after the enable output is asserted. This blanking time allows
sufficient time for the DC/DC converter and the μP to perform power-up
tasks. The KILL and PB inputs are ignored during this period. If KILL
remains low at the end of this time period, the enable output is released,
thus turning off system power. This time delay does not include tDB,ON
or tONT.
Note 4: To manually force an immediate release of the EN/EN pin, the
pushbutton input must be held low for at least tPD,MIN (internal default
power-down timer) + tPDT (adjustable by placing external capacitor at
PDT pin).
Note 5: The enable lockout time is designed to allow an application to
properly power-down such that the next power-up sequence starts from a
consistent powered-down configuration. PB is ignored during this lockout
time. This time delay does not include tDB,ON or tONT.
2954 G01
TEMPERATURE (°C)
–50
IVIN (μA)
10
8
6
4
2
0
–25 02550
75 100
VIN = 26.4V
VIN = 3.3V
VIN = 2.7V
2954 G02
0510 15 20 25 30 35
VIN (V)
IVIN (μA)
15
12
9
6
3
0
T = 85°C
T = –40°C
T = 25°C
2954 G03
VIN (V)
0
0
tDB, ON (ms)
10
20
30
40
50
510 15 20 25 30
TA = 25°C
2954 G04
1
tDB, ON + tONT (ms)
100
1000
1000
10 10 100
10000 TA = 25°C
VIN = 3.3V
ONT EXTERNAL CAPACITANCE (nF)
2954 G05
TEMPERATURE (°C)
–50 –25 0 25 50 75 100
ONT PULL-UP CURRENT (μA)
–3.4
–3.2
–3.0
–2.8
–2.6
VIN = 26.4V
VIN = 2.7V
2954 G06
VIN (V)
0
tDB, OFF (ms)
5 1015202530
50
40
30
20
10
0
TA = 25°C
LTC2954
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PB Power-Down Debounce Time
(tPD,MIN + tPDT) vs PDT External
Capacitance
PDT Pull-Up Current
vs Temperature
PB Current vs PB Voltage
PB Voltage vs External PB
Resistance to Ground
EN/EN VOL vs Current Load EN (LTC2954-2) Voltage vs VIN
EN (LTC2954-1) Voltage vs VIN
Internal Default PB Power-Down
Debounce Time (tPD,MIN) vs VIN
TYPICAL PERFORMANCE CHARACTERISTICS
2954 G07
VIN (V)
0510 15 20 25 30
tPD, MIN (ms)
70
60
40
50
30
20
10
0
TA = 25°C
2954 G08
1
tPD, MIN + tPDT (ms)
100
1000
1000
10 10 100
10000 TA = 25°C
VIN = 3.3V
PDT EXTERNAL CAPACITANCE (nF)
2954 G09
TEMPERATURE (°C)
–50 –25 0 25 50 75 100
PDT PULL-UP CURRENT (μA)
–3.4
–3.2
–3.0
–2.8
–2.6
VIN = 26.4V
VIN = 2.7V
2954 G10
PB CURRENT (μA)
10010
20 30–5 5 15 25
–250
–200
–150
–100
–50
0
PB VOLTAGE (V)
TA = 25°C
VIN = 3.3V
2954 G11
0
0
50
100
150
200
250
300
5101520
VIN = 3.3V
TA = 25°C
PB VOLTAGE (mV)
EXTERNAL PB RESISTANCE TO GROUND (kΩ)
TA = –45°C
TA = 100°C
2954 G13
VIN (V)
0
EN (V)
4
123
TA = 25°C
100k PULL-UP FROM EN TO VIN
1.0
0.8
0.6
0.4
0.2
0
2954 G14
EN (V)
VIN (V)
04
123
4
3
2
1
0
TA = 25°C
100k PULL-UP FROM EN TO VIN
2954 G12
EN/EN CURRENT LOAD (mA)
0.0
EN/EN VOLTAGE (mV)
600
500
400
300
200
100
02.0
0.5 1.0 1.5 2.5
TA = 25°C
VIN = 3.3V
LTC2954
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VIN (Pin 1/Pin 4): Power Supply Input: 2.7V to 26.4V.
PB (Pin 2/Pin 3): Pushbutton Input. Connecting PB to
ground through a momentary switch provides on/off
control via the EN/EN and INT outputs. An internal 100k
pull-up resistor connects to an internal 1.9V bias voltage.
The rugged PB input withstands ±10kV ESD HBM and
can be pulled up to 26.4V externally without consuming
extra current.
ONT (Pin 3/Pin 2): Turn-On Time Input. Placing an external
capacitor to ground determines the additional time (6.4
seconds/μF) the PB pin must be held low before the enable
output is asserted. Floating this pin results in a default
turn on debounce time of 32ms.
GND (Pin 4/Pin 1): Device Ground.
INT (Pin 5/Pin 8): Open Drain Interrupt Output. After a
pushbutton turn-off event is detected (tDB,OFF), the LTC2954
interrupts the system (μP) by asserting the INT pin low.
The μP would perform power-down and housekeeping
tasks and then assert the KILL pin low, thus releasing the
enable output. The INT pulse width is a minimum of 32ms
and stays low as long as PB is asserted. If PB is asserted
for longer than tPD,MIN + tPDT, the INT and EN/EN outputs
are immediately released.
EN (LTC2954-1, Pin 6/Pin 7): Open Drain Enable Output.
This pin is intended to enable system power. EN is asserted
high after a valid PB turn-on event (tDB,ON + tONT). EN is
released low if: a) KILL is not driven high (by μP) within
512ms of the initial valid PB power turn-on event, b) KILL
is driven low during normal operation, c) PB is pressed
and held low (tPD,MIN + tPDT) during normal operation. This
pin can connect directly to a DC/DC converter shutdown
pin that provides an internal pull-up. Otherwise a pull-up
resistor to an external supply is required. The operating
range for this low leakage pin is 0V to 26.4V.
EN (LTC2954-2, Pin 6/Pin 7): Open Drain Enable Bar
Output. This pin is intended to enable system power. EN is
asserted low after a valid PB turn-on event (tDB,ON + tONT).
EN releases high if: a) KILL is not driven high (by μP) within
512ms of the initial valid PB power turn-on event, b) KILL
is driven low during normal operation, c) PB is pressed
and held low (tPD,MIN + tPDT) during normal operation. This
pin can connect directly to a DC/DC converter shutdown
pin that provides an internal pull-up. Otherwise a pull-up
resistor to an external supply is required. The operating
range of this pin is 0V to 26.4V.
PDT (Pin 7/Pin 6): Power-Down Time Input. A capacitor
to ground determines the additional time (6.4 seconds/μF)
that the pushbutton must be held low before immediately
releasing the EN/EN and INT outputs. Floating this pin
results in a pushbutton power-down time of 64ms.
KILL (Pin 8/Pin 5): Kill Input. Forcing KILL low releases the
enable output. During system turn-on, this pin is blanked by
a 512ms internal timer (tKILL,ON BLANK) to allow the system
to pull KILL high. This pin has an accurate 0.6V threshold
and can be used as a voltage monitor input. If unused,
connect to a low voltage output supply (see Figure 6).
Exposed Pad (Pin 9 DFN Only): Exposed Pad may be left
open or connected to device ground.
(TSOT-23/DFN)
PIN FUNCTIONS
LTC2954
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BLOCK DIAGRAM
TIMING DIAGRAMS
LOGIC
OSCILLATOR
OSCILLATOR
DEBOUNCE
10μS
FILTER
2.4V
29V
ZENER
2.4V
1.5k
100k
VIN
2.7V TO 26.4V
PB
GND
EN (–1)
EN (–2)
KILL
INT
ONT PDT
0.8V
0.6V
2954 BD
REGULATOR
HIGH VOLTAGE
KILL
EN/EN
tKILL(PW)
tKILL(PD)
2954 TD01
LTC2954
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Power-On Timing
Off Interrupt Timing, PB Pressed and Released, Enable Remains Active
Forced Off, Power-Down Timing, PB Pressed and Held Low for t > (tPD,MIN + tPDT)
TIMING DIAGRAMS
tDB, ON tONT
PB
ONT
16 CYCLES
PB & KILL IGNORED
EN
(LTC2954-1)
tKILL, ON BLANK
2954 TD02
tDB, OFF
tINT,MIN
t < tPDT
PB
INT
PDT
tPD,MIN
2954 TD03
PB IGNORED
PB
INT
PDT
2954 TD04
16 CYCLES
EN
(LTC2954-1)
tDB, OFF
PB
IGNORED
tPDT
tPD,MIN
tINT,MAX
LTC2954
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Description
The LTC2954 is a pushbutton on/off controller that provides
control of system power via a pushbutton interface. An
enable output toggles system power while an interrupt
output provides debounced pushbutton status. The inter-
rupt output can be used in menu driven applications to
request a system power-down. A power kill input allows
a microprocessor or system to release the enable output,
effectively powering down the system. Independently ad-
justable on and off timers allow dependable pushbutton
control of the enable output and resistance to accidental
toggling of system power.
The length of time the pushbutton input (PB) must be held
low in order to toggle the enable (EN/EN) output on and
off is independently adjustable with external capacitors
at the ONT/PDT pins, respectively. During normal opera-
tion, the interrupt output (INT) is asserted 32ms after PB
goes low. INT then tracks PB until either PB or EN/EN is
released. See Timing Diagrams on page 8.
The KILL input is used to immediately release the enable
output. During a normal power-down sequence, INT re-
quests a system power-down. The μP then performs its
housekeeping tasks and then sets KILL low. If the μP fails
to set KILL low, the user can force a system shutdown by
pressing and holding the pushbutton until the PDT timer
expires.
Turn On
When power is first applied to the LTC2954, the part ini-
tializes the output pins. Any DC/DC converters connected
to the EN/EN pin will therefore be held off. To assert the
enable output, PB must be held low for a minimum of
32ms (tDB,ON). The LTC2954 provides additional turn-on
debounce time (tONT) via an optional capacitor connected
to the ONT pin. The following equation describes the ad-
ditional time that PB must be held low before asserting the
enable output. CONT is the ONT external capacitor (μF):
C
ONT = 1.56 × 10–4 [μF/ms] • (tONT – 1ms)
Once the enable output is asserted, any DC/DC converters
connected to this pin are turned on. The KILL input from
the μP is ignored during a succeeding 512ms blanking
time (tKILL,ON BLANK). This blanking time represents the
maximum time required to power up the DC/DC converter
and the μP. If KILL is not brought high during this 512ms
time window, the enable output is released. The assump-
tion is that 512ms is sufficient time for the system to
power up.
Turn Off
To initiate a power-down sequence, assert the INT output
low by pressing the pushbutton for a minimum of 32ms
(tDB,OFF). The interrupt signal serves as a power-down
request to the μP. The μP would then perform power-down
and housekeeping tasks and assert KILL low when done.
This in turn releases the enable output, thus shutting off
system power.
Adjustable Power-Down Timer
The LTC2954 provides a failsafe feature that allows the
user to turn off system power (via PB) under system fault
conditions. For cases when the μP fails to respond to the
interrupt signal, the user can force an immediate power-
down by pressing and holding down the pushbutton. The
length of time that PB must be held low is given by a fixed
internal 64ms delay (tPD,MIN) plus an adjustable power-
down timer delay (tPDT
, see Timing Diagrams on page 8).
The adjustable delay is set by placing an optional external
capacitor on the PDT pin. Use the following equation to
calculate the capacitance for the desired delay. CPDT is the
PDT external capacitor (μF):
C
PDT = 1.56 × 10-4 [μF/ms] • (tPDT – 1ms)
Simplified Power On/Off Sequence
Figure 1 shows a simplified LTC2954-1 power-on and
power-off sequence. A high to low transition on PB (t1)
initiates the power on sequence. In order to assert the
enable output, the PB pin must stay low continuously (PB
high resets timers) for a time controlled by the default
32ms and the external ONT capacitor (t2–t1). Once EN
goes high (t2), an internal 512ms blanking timer is started.
This blanking timer is designed to give sufficient time for
the DC/DC converter to reach its final voltage, and to allow
the μP enough time to perform power-on tasks.
The KILL pin must be pulled high within 512ms of the EN
pin going high. Failure to do so results in the EN pin going
APPLICATIONS INFORMATION
LTC2954
10
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Figure 1. Simplified Power On/Off Sequence for LTC2954-1. μP Asserts KILL After an Interrupt
Figure 2. KILL Remaining Low Aborts Power-On Sequence for LTC2954-1
APPLICATIONS INFORMATION
t1t2
tDB, ON
XXX DON'T CARE
t3t4t5t6t8t9
t7
PB
ONT
PDT
EN
KILL
INT
PB & KILL IGNORED
2954 F01
tKILL, ON BLANK tDB, OFF
tPD, MIN
tONT
t < tPDT
PB IGNORED
μP DRIVES
KILL LOW
tABORT
tDB,ON + tONT
PB
KILL
POWER-ON
TIMING
EN
512ms
INTERNAL
TIMER
POWER
TURNED OFF
2954 F02
μP FAILED TO SET
KILL HIGH
LTC2954
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Aborted Power-On Sequence
The power-on sequence is aborted when the KILL remains
low at the end of the 512ms blanking time. Figure 2 is a
simplified version of an aborted power-on sequence. At
time tABORT, since KILL is still low, EN pulls low (thus
turning off the DC/DC converter).
μP Turns Off Power During Normal Operation
Once the system has powered on and is operating nor-
mally, the μP can turn off power by setting KILL low, as
shown in (Figure 3). At time tKILL, KILL is set low by the
μP. This immediately pulls EN low, thus turning off the
DC/DC converter.
DC/DC Turn Off Blanking
When the DC/DC converter is turned off, it can take a sig-
nificant amount of time for its output to decay to ground. It
is desirable to wait until the output of the DC/DC converter
is near ground before allowing the user (via PB) to restart
the converter. This condition guarantees that the μP has
always powered down completely before it is restarted.
Figure 4 shows the μP turning power off. After a low on
KILL releases enable, the internal 256ms timer ignores the
PB pin. This is shown as tEN/EN, LOCKOUT in (Figure 4).
Figure 3. μP Turns Off Power (LTC2954-1) Figure 4. DC/DC Turn-Off Blanking (LTC2954-1)
low 512ms after it went high. Note that the LTC2954 does
not sample KILL and PB until after the 512ms internal timer
has expired. The reason PB is ignored is to ensure that
the system is not forced off while powering on. Once the
512ms timer expires (t4), the release of the PB pin is then
debounced with an internal 32ms timer. The system has
now properly powered on and the LTC2954 monitors PB
and KILL for a turn-off command while consuming only
6μA of supply current.
A high to low transition on PB (t5) starts the power-off
sequence debounce timer. In order to assert the interrupt
output (INT), PB must stay low continuously (PB high
resets debounce timer) for 32ms (t6–t5). At the comple-
tion of the power-down debounce timer (t6), an internal
interrupt timer keeps the interrupt output low for at least
32ms, even if PB is released between t6 and t7. If PB is
low at the end of this 32ms internal timer (t7), the external
adjustable power-down timer is started. The capacitor
placed at the PDT pin will determine the time period of
this timer. If the pushbutton is released prior to 16 cycles
of the PDT pin, the interrupt output will go high (t8). Note
that the enable output is not directly changed by this
interrupt pulse. The function of the interrupt signal is to
initiate a software shutdown. At t9, the μP has performed
its power-down functions and asserted the KILL input
low. This releases the enable output, which in turn shuts
down system power. Note that if the pushbutton is held
long enough to count 16 cycles at the PDT pin, the enable
pin would be released immediately after the 16th cycle.
The system is now in its reset state where the LTC2954 is
in low power mode (6μA) and PB is monitored for a high
to low transition.
APPLICATIONS INFORMATION
tKILL
PB
EN
DC/DC
TURNS OFF
2954 F03
KILL XXX DON’T CARE
μP SETS
KILL LOW
PB PB IGNORED
EN
KILL
PB BLANKING
(INTERNAL
SIGNAL)
XXX DON’T CARE
256ms
POWER ON
2954 F04
DC/DC
TURNS OFF
μP SETS
KILL LOW
tEN/EN, LOCKOUT
LTC2954
12
2954fb
LTC2954-1, LTC2954-2 Versions
The LTC2954-1 (high true EN) and LTC2954-2 (low true
EN) differ only by the polarity of the high voltage (33V ABS
MAX), enable pin. The LTC2954-1 EN pin is a low leakage
high true open drain output designed to drive the shutdown
pin of DC/DC converters. The LTC2954-2 is a low leakage,
low true open drain enable output designed to drive the
gate of an external PFET. The LTC2954-2 provides a user
manual power path control.
High Voltage Pins
The VIN, PB and EN/EN pins can operate at voltages up to
26.4V. PB can, additionally, operate below ground (–6V)
without latching up the device. PB has an ESD HBM rating
of ±10kV. If the pushbutton switch connected to PB exhib-
its high leakage current, then an external pull-up resistor
to VIN is recommended. Furthermore, if the pushbutton
switch is physically located far from the LTC2954 PB pin,
parasitic capacitances may couple onto the high imped-
ance PB input. Additionally, parasitic series inductance
may cause unpredictable ringing at the PB pin. Placing
a 5.1k resistor from the PB pin to the pushbutton switch
would mitigate parasitic inductance problems. Placing a
0.1μF capacitor on the PB pin would lessen the impact of
parasitic capacitive coupling.
Figure 5. Input Voltage Monitoring with KILL Input Figure 6. No μP Application
Voltage Monitoring with KILL Input
The KILL pin can be used as a voltage monitor. Figure 5
shows an application where the KILL pin has a dual func-
tion. 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 be-
low the set value, the voltage at the KILL pin falls below
0.6V and the EN pin is quickly pulled low. Note that the
resistor values should be as large as possible, but small
APPLICATIONS INFORMATION
PB
VIN VOUT
SHDN**
VIN = 9V
EN
INT
KILL
INT
KILL
(OPEN DRAIN)
LTC2954-1
GND ONT PDT
LT1767-3.3
μP
R1
10k
3.3V
2954 F05
C4
0.1μF
R3
806k
1%
R2
100k
1%
* OPTIONAL
** SHDN INTERNALLY PULLED
UP BY THE LT1767-3.3
VIN
CONT*
0.033μF
CPDT*
F
VIN = 9V
3.3V
R1
100k
C3*
0.01μF
2954 F06
+
C4
0.1μF
PB
EN
INT
KILL
LTC2954-1
GND ONT PDT
VIN
CONT*
0.033μF
CPDT*
F * OPTIONAL
** SHDN INTERNALLY
PULLED UP BY
THE LT1767-3.3
VIN VOUT
SHDN**
LT1767-3.3
TYPICAL APPLICATIONS
enough to keep leakage currents from tripping the 0.6V
KILL comparator.
The DC/DC converter shown has an internal pull-up cur-
rent on its SHDN pin. A pull-up resistor on EN is thus not
needed.
Operation Without μP
Figure 6 shows how to connect the KILL pin when there
is no circuitry available to drive it. The minimum pulse
LTC2954
13
2954fb
Figure 7. PowerPath Control with 6V Undervoltage Detect
width detected is 30μs. If there are glitches on the resis-
tor pull-up voltage that are wider than 30μs and transition
below 0.6V, then an appropriate bypass capacitor should
be connected to the KILL pin. The optional CPDT external
capacitor extends the length of time (beyond 64ms) that
the PB input must be held low before releasing the enable
output.
High Voltage PowerPath Switching
The high voltage EN open drain output of the LTC2954-2
is designed to switch on/off an external power PFET. This
allows a user to connect/disconnect a power supply (or
battery) to its load by toggling the PB pin. Figure 7 shows
the LTC2954-2 controlling a two cell Li-Ion battery ap-
plication. The KILL pin is connected to the output of the
TYPICAL APPLICATIONS
VOUT
R1
909k
1%
R4
100k
1%
C3*
0.1μF
2954 F07
C4
0.1μF
CERAMIC
*OPTIONAL
VTH = 0.6V INPUT
R5
100k R9
100k
M1
+
4.2V
SINGLE CELL
Li-Ion BATTERY
+
4.2V
SINGLE CELL
Li-Ion BATTERY
OPTIONAL GLITCH
FILTER CAPACITOR
VOUT,TRIP POINT = 6V
PB
EN
INT
KILL
LTC2954-2
GND ONT PDT
VIN
CONT*
0.033μF
PFET through a resistive divider. The KILL pin serves as
a voltage monitor. When VOUT drops below 6V, causing a
KILL voltage below VKILL(TH), the EN pin becomes an open
circuit 30μs later. Since the PDT pin is open-circuited, the
power-down debounce time defaults to 64ms.
PB Pin in a Noisy Environment
The rugged PB pin is designed to operate in noisy environ-
ments. Transients below ground (>6V) and above VIN
(<33V) will not damage the rugged PB pin. Additionally,
the PB pin can withstand ESD HBM strikes up to ±10kV.
In order to keep external noise from coupling inside the
LTC2954, place an R-C network close to the PB pin. A 5.1k
resistor and a 0.1μF capacitor should suffice for most noisy
applications (see Figure 8).
Figure 8. Noisy PB Trace
PB
VIN
LTC2954-1
GND ONT
R6
5.1k
2954 F08
TRACE
CAPACITANCE
PARASITICS
C5
0.1μF
DETAILS OMITTED
FOR CLARITY
TRACE
INDUCTANCE
NOISE
EN
INT
KILL
PDT
VIN
LTC2954
14
2954fb
External Pull-Up Resistor On PB
An internal pull-up resistor on the PB pin makes an ex-
ternal 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 (>2μA),
the PB voltage may fall close to the threshold window. To
mitigate the effect of the board leakage, a 10k resistor to
VIN is recommended (see Figure 9).
Figure 9. External Pull-Up Resistor On PB Pin
Reverse Battery Protection
To protect the LTC2954 from a reverse battery connec-
tion, place a 1k resistor in series with the VIN pin (see
Figure 10).
TYPICAL APPLICATIONS
PB
VIN
LTC2954-1/
LTC2954-2
GND
EXTERNAL BOARD
LEAKAGE CURRENT
100k
2.4V
R7
10k
2954 F09
>2μA
PINS OMITTED
FOR CLARITY
IF EXTERNAL PARASITIC BOARD
LEAKAGE >2μA, USE EXTERNAL
PULL-UP RESISTOR
VIN
LTC2954
15
2954fb
DDB Package
8-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1702 Rev B)
PACKAGE DESCRIPTION
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
0.56 ± 0.05
(2 SIDES)
0.75 ±0.05
R = 0.115
TYP
R = 0.05
TYP
2.15 ±0.05
(2 SIDES)
3.00 ±0.10
(2 SIDES)
14
85
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.200 REF
0 – 0.05
(DDB8) DFN 0905 REV B
0.25 ± 0.05
2.20 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.61 ±0.05
(2 SIDES)
1.15 ±0.05
0.70 ±0.05
2.55 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
0.50 BSC
PIN 1
R = 0.20 OR
0.25 × 45°
CHAMFER
0.50 BSC
LTC2954
16
2954fb
TS8 Package
8-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1637 Rev A)
PACKAGE DESCRIPTION
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
LTC2954
17
2954fb
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However,
no responsibility is assumed for its use. Linear Technology Corporation makes no representation that
the interconnection of its circuits as described herein will not infringe on existing patent rights.
REVISION HISTORY
REV DATE DESCRIPTION PAGE NUMBER
B 2/11 Revised Pin Descriptions for EN and EN pins
Revised notes for Figures 5 and 6 in Typical Applications
6
12
(Revision history begins at Rev B)
LTC2954
18
2954fb
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2006
LT 0211 REV B • PRINTED IN USA
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 Controller with
Power-Down Fault Detect KILL Timer
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
LT4351 MOSFET Diode-OR Controller Wide Input Range: 1.2V to 18V
LTC2952 Pushbutton PowerPath™ Controller with
Supervisor
Automatic Low Loss Switchover Between DC Sources
LTC2953 Pushbutton ON/OFF Controller with Voltage
Monitoring
High Voltage Pushbutton Controller with 200ms Voltage Reset Monitor
Figure 10. Reverse Battery Protection
RELATED PARTS
TYPICAL APPLICATION
VIN
SHDN
VOUT
INT
KILL
LT1761-1.8
R1
10k
R8
1k
R5
910k
2954 TA02
C4
0.1μF
μP
1.8V
9V
BATTERY
PB
EN
INT
KILL
LTC2954-1
GND ONT PDT
CONT*
0.033μF
VIN
CPDT*
F
*OPTIONAL
+

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