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LTC2954 Push Button On/Off Controller with P Interrupt U
SHORT PULSE LONG PULSE STAYS ON TURNS OFF INTERRUPT INTERRUPT
2954 TD01b 2954 TA01
FEATURES

DESCRIPTIO

Adjustable Power On/Off Timers Low Supply Current: 6A Wide Operating Voltage Range: 2.7V to 26.4V Low Leakage EN Output (LTC2954-1) Allows DC/DC Converter Control High Voltage EN Output (LTC2954-2) Allows Circuit Breaker Control Simple Interface Allows Graceful P Shut Down High Input Voltage PB Pin with Internal Pull Up Resistor 10kV ESD HBM on PB Input Accurate 0.6V Threshold on KILL Comparator Input 8-Pin 3mm x 2mm DFN and ThinSOTTM Packages
The LTC(R)2954 is a push button On/Off controller that manages system power via a push button interface. An enable output toggles system power while an interrupt output provides debounced push button status. The interrupt 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 push button 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 voltage range to accommodate a wide variety of input power supplies. Very low quiescent current (6A 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.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.
APPLICATIO S

Push Button Power Path Control Portable Instrumentation Meters Blade Servers Portable Customer Service PDA Desktop and Notebook Computers
+
9V
100k
VIN LTC2954-2 PB GND ONT
EN INT KILL PDT 1F
tPDT = 6.4 SECONDS
U
TYPICAL APPLICATIO
U
Push Button On/Off with Interrupt
VIN VOUT DC/DC 100k PB TURN ON PULSE
EN 10k INT KILL P/C INT
TURNS ON
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1
LTC2954
(Note 1)
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
TOP VIEW GND 1 ONT 2 PB 3 VIN 4 9 8 7 6 5 INT EN/EN PDT KILL TOP VIEW VIN 1 PB 2 ONT 3 GND 4 8 KILL 7 PDT 6 EN/EN 5 INT
DDB PACKAGE 8-LEAD (3mm x 2mm) PLASTIC DFN TJMAX = 125C, JA = 165C/W EXPOSED PAD (PIN 9) UNCONNECTED
ORDER PART NUMBER LTC2954CDDB-1 LTC2954CDDB-2 LTC2954IDDB-1 LTC2954IDDB-2
DDB PART MARKING* LCJG LCNJ LCJG LCNJ
Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
ELECTRICAL CHARACTERISTICS
SYMBOL VIN IIN VUVL VUVL(HYST) PARAMETER Supply Voltage Range VIN Supply Current VIN Undervoltage Lockout VIN Undervoltage Lockout Hysteresis PB Voltage Range
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 2.7V to 26.4V, unless otherwise noted. (Note 2)
CONDITIONS Steady State Operation System Power On, VIN = 2.7V to 24V VIN Falling

Push Button, Enable (PB, EN/EN)) VPB(MIN, MAX) Single-Ended
2
U
PACKAGE/ORDER I FOR ATIO W U
U
WW
W
ABSOLUTE
AXI U RATI GS
Operating Temperature Range LTC2954C-1 .............................................. 0C to 70C LTC2954C-2 .............................................. 0C to 70C LTC2954I-1 .......................................... - 40C to 85C LTC2954I-2 .......................................... - 40C to 85C Storage Temperature Range DFN Package..................................... - 65C to 125C TSOT-23............................................ - 65C to 150C Lead Temperature (Soldering, 10 sec) .................. 300C
TS8 PACKAGE 8-LEAD PLASTIC TSOT-23 TJMAX = 125C, JA = 140C/W
ORDER PART NUMBER LTC2954CTS8-1 LTC2954CTS8-2 LTC2954ITS8-1 LTC2954ITS8-2
TS8 PART MARKING* LTCJH LTCNK LTCJH LTCNK
MIN 2.7
TYP 6
MAX 26.4 12 2.5 700
UNITS V A V mV
2.2 50
2.3 400
-1
26.4
V
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LTC2954 ELECTRICAL CHARACTERISTICS
SYMBOL IPB PARAMETER PB Input Current
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 2.7V to 26.4V, unless otherwise noted. (Note 2)
CONDITIONS 2.5V < VPB < 26.4V VPB = 1V VPB = 0.6V PB Falling IPB = -1A Enable Released Enable Asserted VEN/ EN = 1V, Sink Current Off VEN/ EN = 26.4V, Sink Current Off IEN/ EN = 500A VONT = 0V VONT = 1.3V ONT Pin Float, PB Falling Enable Asserted

MIN -1 -3 0.6 1 200
TYP -6 -9 0.8 1.6 256
MAX 1 -12 -15 1 2 325 0.1 1
UNITS A A A V V ms A A V A A ms ms A A ms ms ms ms ms A V V mV A s s ms
VPB(VTH) VPB(VOC) tEN, Lock Out IEN(LKG) VEN(VOL) IONT(PU) IONT(PD) tDB, ON tONT
PB Input Threshold PB Open Circuit Voltage EN/EN Lock Out Time (Note 5) EN/EN Leakage Current EN/EN Voltage Output Low ONT Pull Up Current ONT Pull Down Current Internal Turn On Debounce Time
0.11 -2.4 2.4 26 9 -2.4 2.4 26 52 9 26 35 -3 3 32 11.5 -3 3 32 64 11.5 32 43.5
0.4 -3.6 3.6 41 13.5 -3.6 3.6 41 82 13.5 41 54.5 1
Power On Timing Pin (ONT)

Additional Adjustable Turn On Time CONT = 1500pF Power Down Timing Pin (PDT) IPDT(PU) IPDT(PD) tDB, OFF tPD, Min tPDT t INT, Min t INT, Max IINT(LKG) VINT(VOL) VKILL(TH) VKILL(HYST) IKILL(LKG) t KILL(PW) t KILL(PD) t KILL, On Blank PDT Pull Up Current PDT Pull Down Current Turn Off Interrupt Debounce Time Internal PB Power Down DebounceTime (Note 4) Additional Adjustable PB Power Down Debounce Time Minimum INT Pulse Width Maximum INT Pulse Width INT Leakage Current INT Output Voltage Low KILL Input Threshold Voltage KILL Input Threshold Hysteresis KILL Leakage Current KILL Minimum Pulse Width KILL Propagation Delay KILL Turn On Blanking (Note 3) KILL Falling Enable Released KILL = Low, Enable Asserted Enable Released V KILL = 0.6V VPDT = 0V VPDT = 1.3V PB Falling INT Falling PDT Pin Float, PB Falling Enable Released CPDT = 1500pF INT Asserted INT Released CPDT = 1500pF, INT Asserted INT Released V INT = 3V I INT = 3mA KILL Falling

P Handshake Pins (INT, KILL)

0.11 0.57 10 30 0.6 30
0.4 0.63 50 0.1 30
400
512
650
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 P 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 push button 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 lock out 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 lock out time. This time delay does not include tDB, ON or tONT.
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LTC2954 TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Temperature
10 VIN = 26.4V 8 VIN = 3.3V VIN = 2.7V 4 IVIN (A) 12 T = 85C 9 T = -40C 6 tDB, ON (ms) 30 T = 25C 40 15
IVIN (A)
6
2
0 -50
-25
0 25 50 TEMPERATURE (C)
10000
Turn On Debounce Time (tDB, ON + tONT) vs ONT External Capacitance
TA = 25C VIN = 3.3V ONT PULL-UP CURRENT (A)
tDB, ON + tONT (ms)
1000
tDB, OFF (ms)
100
10
1
100 10 ONT EXTERNAL CAPACITANCE (nF)
Internal Default PB Power Down Debounce Time (tPD, Min) vs VIN
70 60 50 tPD, MIN (ms) 40 30 20 10 0 0 5 10 15 VIN (V) 20 25 30
2954 G14
PDT PULL-UP CURRENT (A)
TA = 25C tPD, MIN + tPDT (ms) 1000
4
UW
75
2954 G01 2954 G04
Supply Current vs Supply Voltage
50
Internal Default Turn On Debounce Time (tDB, ON) vs VIN
TA = 25C
20
3
10 0
100
0
0
5
10
15
20
25
30
35
0
5
10
VIN (V)
2954 G02
15 VIN (V)
20
25
30
2954 G03
ONT Pull-Up Current vs Temperature
-3.4 50
Turn Off Debounce Time (tDB, OFF) vs VIN
TA = 25C
-3.2 VIN = 26.4V -3.0 VIN = 2.7V -2.8
40
30
20
10
1000
-2.6 -50
-25
0 25 50 TEMPERATURE (C)
75
100
2954 G05
0
0
5
10
15 VIN (V)
20
25
30
2954 G06
PB Power Down Debounce Time (tPD, Min + tPDT) vs PDT External Capacitance
10000 TA = 25C VIN = 3.3V -3.4
PDT Pull-Up Current vs Temperature
-3.2 VIN = 26.4V -3.0 VIN = 2.7V -2.8
100
10
1
100 10 PDT EXTERNAL CAPACITANCE (nF)
1000
-2.6 -50
-25
0 25 50 TEMPERATURE (C)
75
100
2954 G08
2954 G07
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LTC2954 TYPICAL PERFOR A CE CHARACTERISTICS
-250
PB Current vs PB Voltage
TA = 25C VIN = 3.3V
-200 PB VOLTAGE (mV) PB CURRENT (A)
-150
-100
-50
0 -10
-5
600 500 EN/EN VOLTAGE (mV) 400 300 200 100
EN/EN VOL vs Current Load
TA = 25C VIN = 3.3V
EN (V)
EN (V)
0 0.0
0.5 1.5 2.0 1.0 EN/EN CURRENT LOAD (mA)
UW
0
2954 G11
300 250 200 150 100 50 0
PB Voltage vs External PB Resistance to Ground
VIN = 3.3V
TA = 100C TA = 25C TA = -45C
5 10 15 PB VOLTAGE (V)
20
25
30
0 5 10 15 20 EXTERNAL PB RESISTANCE TO GROUND (k)
2954 G10
2954 G09
1.0
EN (LTC2954-1) Voltage vs VIN
TA = 25C 100k PULL-UP FROM EN TO VIN
4
EN (LTC2954-2) Voltage vs VIN
TA = 25C 100k PULL-UP FROM EN TO VIN
0.8
3
0.6
2
0.4 1
0.2
2.5
0
0
1
2 VIN (V)
3
4
2954 G12
0
0
1
2 VIN (V)
3
4
2954 G13
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LTC2954 PI FU CTIO S U U U
(TSOT-23/DFN) released low if: a) KILL is not driven high (by P) 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. 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 P) 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. 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/F) that the push button must be held low before immediately releasing the EN/EN and INT outputs. Floating this pin results in a push button 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. Exposed Pad (Pin 9 DFN Only): Exposed Pad may be left open or connected to device ground. VIN (Pin 1/Pin 4): Power Supply Input: 2.7V to 26.4V. PB (Pin 2/Pin 3): Push Button 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/F) 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 push button turn off event is detected (tDB,OFF), the LTC2954 interrupts the system (P) by asserting the INT pin low. The P 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
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LTC2954 W
HIGH VOLTAGE VIN 2.7V TO 26.4V 1.5k 29V ZENER REGULATOR 2.4V EN (-1) EN (-2) OSCILLATOR LOGIC 10S FILTER 0.8V OSCILLATOR INT DEBOUNCE 0.6V KILL
2954 BD
BLOCK DIAGRA
2.4V
100k PB
GND
ONT
PDT
TI I G DIAGRA S W UW
tKILL(PW) KILL
tKILL(PD) EN/EN
2954 TD01
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7
LTC2954 TI I G DIAGRA S
PB tDB, ON tONT
EN (LTC2954-1)
2954 TD02
PB tDB, OFF PDT
INT tINT, Min
PB tDB, OFF PDT
INT tINT, Max EN (LTC2954-1)
2954 TD04
Forced Off, Power Down Timing, PB Pressed and Held Low for t > (tPD, Min + tPDT)
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8
W
UW
PB & KILL IGNORED tKILL, ON BLANK
16 CYCLES
Power On Timing
PB IGNORED t < tPDT
tPD, Min
2954 TD03
Off Interrupt Timing, PB Pressed and Released, Enable Remains Active
PB IGNORED
16 CYCLES
tPD, Min
tPDT
LTC2954
Description The LTC2954 is a push button On/Off controller that provides control of system power via a push button interface. An enable output toggles system power while an interrupt output provides debounced push button status. The interrupt 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 adjustable On and Off timers allow dependable push button control of the enable output and resistance to accidental toggling of system power. The length of time the push button 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 operation, 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 requests a system power down. The P then performs its housekeeping tasks and then sets KILL low. If the P fails to set KILL low, the user can force a system shutdown by pressing and holding the push button until the PDT timer expires. Turn On When power is first applied to the LTC2954, the part initializes 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 additional time that PB must be held low before asserting the enable output. CONT is the ONT external capacitor (F): CONT = 1.56 x 10-4 [F/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 P is ignored during a succeeding 512ms blanking time (t KILL, ON BLANK). This blanking time represents the
U
maximum time required to power up the DC/DC converter and the P. If KILL is not brought high during this 512ms time window, the enable output is released. The assumption 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 push button for a minimum of 32ms (tDB,OFF). The interrupt signal serves as a power down request to the P. The P 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 P fails to respond to the interrupt signal, the user can force an immediate power down by pressing and holding down the push button. 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 diagram 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 (F): CPDT = 1.56 x 10-4 [F/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 P 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
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APPLICATIO S I FOR ATIO W U U
9
LTC2954 U
t4 t5 t6 t7 t8 t9 PB IGNORED tDB, OFF tPD, MIN INT t < tPDT KILL
XXX DON'T CARE
APPLICATIO S I FOR ATIO
t1 PB tDB, ON ONT tONT PDT
EN
2954 F01
Figure 1. Simplified Power On/Off Sequence for LTC2954-1. P Asserts KILL after an Interrupt
POWER ON TIMING POWER TURNED OFF EN
Figure 2. KILL Remaining Low Aborts Power On Sequence for LTC2954-1
10
W
t2
U
U
t3 PB & KILL IGNORED tKILL, ON BLANK
P DRIVES KILL LOW
tABORT
PB tDB, ON + tONT 512ms INTERNAL TIMER
P FAILED TO SET KILL HIGH
KILL
2954 F02
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LTC2954
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 turnoff command while consuming only 6A 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 completion 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 push button 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 P 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 push button is held long enough to count 16 cycles at the PDT pin, the enable pin would be released immediately after the 16th cycle. The
tKILL PB DC/DC TURNS OFF EN
DC/DC TURNS OFF
PB BLANKING (INTERNAL SIGNAL) EN 256ms
P SETS KILL LOW KILL XXX DON'T CARE
2954 F03
Figure 3. P Turns Off Power (LTC2954-1)
U
system is now in its reset state where the LTC2954 is in low power mode (6A) and PB is monitored for a high to low transition. 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). P Turns Off Power During Normal Operation Once the system has powered on and is operating normally, the P can turn off power by setting KILL low, as shown in (Figure 3). At time t KILL, KILL is set low by the P. 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 significant 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 P has always powered down completely before it is restarted. Figure 4 shows the P 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).
tEN/EN, Lockout
PB POWER ON PB IGNORED
APPLICATIO S I FOR ATIO W U U
P SETS KILL LOW
KILL XXX DON'T CARE
2954 F04
Figure 4. DC/DC Turn Off Blanking (LTC2954-1)
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LTC2954
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)
TYPICAL APPLICATIO S
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 function. It is driven by a low leakage open drain output of the P. 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 0.6V 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 0.6V KILL comparator.
VIN = 9V VIN R3 806k 1% R2 100k 1% R1 10k INT P PB GND ONT VOUT 3.3V
LT1767-3.3 SHDN
C4 0.1F
VIN
EN LTC2954-1 INT KILL PDT CONT* 0.033F CPDT* 1F
PB GND ONT
KILL (OPEN DRAIN)
2954 F05
*OPTIONAL
Figure 5. Input Voltage Monitoring with KILL Input
12
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without latching up the device. PB has an ESD HBM rating of 10kV. If the push button switch connected to PB exhibits high leakage current, then an external pull-up resistor to VIN is recommended. Furthermore, if the push button switch is physically located far from the LTC2954 PB pin, parasitic capacitances may couple onto the high impedance 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 push button switch would mitigate parasitic inductance problems. Placing a 0.1F capacitor on the PB pin would lessen the impact of parasitic capacitive coupling. The DC/DC converter shown has an internal pull-up current on its SHDN pin. A pull-up resistor on EN is thus not needed. Operation Without P Figure 6 shows how to connect the KILL pin when there is no circuitry available to drive it. The minimum pulse width detected is 30s. If there are glitches on the resistor pull-up voltage that are wider than 30s and transition below 0.6V, then an appropriate bypass capacitor should be connected to the KILL pin. The optional CPDT external
VIN = 9V VIN VOUT 3.3V LT1767-3.3 SHDN R1 100k C4 0.1F VIN EN LTC2954-1 INT KILL PDT CONT* 0.033F CPDT* 1F
APPLICATIO S I FOR ATIO W U U
U
+
*OPTIONAL
C3* 0.01F
2954 F06
Figure 6. No P Application
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LTC2954 TYPICAL APPLICATIO S
capacitor extends the length of time (beyond 64ms) that the PB input must be held low before releasing the enable output. High Voltage Power Path 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 application. The KILL pin is connected to the output of the PFET through a resistive divider. The KILL pin serves as a voltage monitor. When VOUT drops below 6V, causing a
4.2V SINGLE CELL Li-Ion BATTERY
+
C4 0.1F CERAMIC VIN LTC2954-2 PB GND ONT EN INT KILL PDT CONT* 0.033F
4.2V SINGLE CELL Li-Ion BATTERY
+
Figure 7. Power Path Control with 6V Under Voltage Detect
PARASITICS TRACE CAPACITANCE NOISE TRACE INDUCTANCE C5 0.1F R6 5.1k VIN PB LTC2954-1 EN INT KILL GND ONT PDT
U
KILL voltage below VKILL(TH), the EN pin becomes an open circuit 30s 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 environments. 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 0.1F capacitor should suffice for most noisy applications (see Figure 8).
R5 100K
M1 R9 100K
VOUT VOUT,TRIP POINT = 6V R1 909k 1%
VTH = 0.6V INPUT R4 100k 1% *OPTIONAL
OPTIONAL GLITCH FILTER CAPACITOR C3* 0.1F
2954 F07
VIN
DETAILS OMITTED FOR CLARITY
2954 F08
Figure 8. Noisy PB Trace
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13
LTC2954 TYPICAL APPLICATIO S
External Pull-Up Resistor on PB An internal 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 (>2A), 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).
14
U
Reverse Battery Protection To protect the LTC2954 from a reverse battery connection, place a 1k resistor in series with the VIN pin (see Figure 10).
VIN R7 10k
VIN
LTC2954-1/ LTC2954-2 2.4V
PB EXTERNAL BOARD LEAKAGE CURRENT >2A
100k
GND PINS OMITTED FOR CLARITY
IF EXTERNAL PARASITIC BOARD LEAKAGE >2A, USE EXTERNAL PULL-UP RESISTOR
2954 F09
Figure 9. External Pull-Up Resistor on PB Pin
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LTC2954 U
(Reference LTC DWG # 05-08-1702 Rev B)
0.61 0.05 (2 SIDES) 0.70 0.05 2.55 0.05 1.15 0.05 PACKAGE OUTLINE 0.25 0.05 0.50 BSC 2.20 0.05 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 0.200 REF 2.00 0.10 (2 SIDES) 0.56 0.05 (2 SIDES) 0.75 0.05 3.00 0.10 (2 SIDES) R = 0.05 TYP R = 0.115 TYP 5 0.40 0.10 8
PACKAGE DESCRIPTIO
DDB Package 8-Lead Plastic DFN (3mm x 2mm)
4 0.25 0.05 2.15 0.05 (2 SIDES)
1 0.50 BSC
PIN 1 R = 0.20 OR 0.25 x 45 CHAMFER
(DDB8) DFN 0905 REV B
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 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 - 0.05
BOTTOM VIEW--EXPOSED PAD
(Reference LTC DWG # 05-08-1637)
0.52 MAX 0.65 REF 2.90 BSC (NOTE 4)
TS8 Package 8-Lead Plastic TSOT-23
1.22 REF
3.85 MAX 2.62 REF
1.4 MIN
2.80 BSC
1.50 - 1.75 (NOTE 4) PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR
0.65 BSC 0.80 - 0.90
0.22 - 0.36 8 PLCS (NOTE 3)
0.20 BSC DATUM `A' 1.00 MAX
0.01 - 0.10
0.30 - 0.50 REF
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
0.09 - 0.20 (NOTE 3)
1.95 BSC
TS8 TSOT-23 0802
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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.
15
LTC2954 U
+
VIN R8 1k R5 910k VOUT LT1761-1.8 SHDN 1.8V C4 0.1F VIN LTC2954-1 PB GND ONT CONT* 0.033F EN INT KILL PDT CPDT* 1F R1 10k INT KILL P *OPTIONAL
2954 TA02
TYPICAL APPLICATIO
9V BATTERY
Figure 10. Reverse Battery Protection
RELATED PARTS
PART NUMBER LTC2900 TC2909 LTC2910 LTC2914 LTC2950/LTC2951 LTC4411 LTC4412HV LTC4055 LT4351 DESCRIPTION Programmable Quad Supply Monitor Precision Triple/Dual Input UV, OV and Negative Voltage Monitor Octal Positive/Negative Voltage Monitor Quad UV/OV Positive/Negative Voltage Monitor Push Button On/Off Controllers 2.6A Low Loss Ideal Diode in ThinSOT Power Path Controller in ThinSOT MOSFET Diode-OR Controller COMMENTS Adjustable RESET, 10-Lead MSOP and 3mm x 3mm DFN Packages 6.5V Shunt Regulator for High Voltage Operation Eight Adjustable Inputs (0.5V) Adjustable UV and OV Trip Values High Voltage, Low Power Push Button Controller with Power Down Fault Detect KILL Timer No External MOSFET, Automatic Switching Between DC Sources Efficient Diode-ORing, Automatic Switching Between DC Sources, 3V to 36V Wide Input Range: 1.2V to 18V LLTC2904/LTC2905 Pin-Programmable Dual Supply Monitors Adjustable RESET and Tolerance, 8-Lead SOT-23 and 3mm x 2mm DFN Packages
USB Power Controller and Li-Ion Charger Automatic Switchover, Charges 1-Cell Li-Ion Batteries
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16 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
LT 0606 * PRINTED IN USA
FAX: (408) 434-0507 www.linear.com
LINEAR TECHNOLOGY CORPORATION 2006

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