LTC2954 Pushbutton On/Off Controller with µP Interrupt FEATURES DESCRIPTION n Adjustable Power On/Off Timers The LTC®2954 is a pushbutton on/off controller that n Low Supply Current: 6μA manages system power via a pushbutton interface. An n Wide Operating Voltage Range: 2.7V to 26.4V enable output toggles system power while an interrupt n Low Leakage EN Output (LTC2954-1) Allows DC/DC output provides debounced pushbutton status. The inter- Converter Control rupt output can be used in menu driven applications to n High Voltage EN Output (LTC2954-2) Allows Circuit request a system power-down. A power kill input allows Breaker Control a microprocessor or system to reset the enable output, n Simple Interface Allows Graceful μP Shutdown effectively powering down the system. Independently n High Input Voltage PB Pin with Internal Pull-Up adjustable on and off timers allow dependable pushbutton Resistor control of the enable output and resistance to accidental n ±10kV ESD HBM on PB Input toggling of system power. n Accurate 0.6V Threshold on KILL Comparator Input The LTC2954 operates over a wide 2.7V to 26.4V input volt- n 8-Pin 3mm × 2mm DFN and ThinSOT™ Packages age range to accommodate a wide variety of input power supplies. Very low quiescent current (6μA typical) makes APPLICATIONS the LTC2954 ideally suited for battery powered applications. Two versions of the part are available to accommodate n Pushbutton PowerPath™ Control either positive or negative enable polarities. n Portable Instrumentation Meters L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and n Blade Servers PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks n Portable Customer Service PDA are the property of their respective owners. n Desktop and Notebook Computers TYPICAL APPLICATION Pushbutton On/Off with Interrupt VIN VOUT TURN-ON PULSE SHORT PULSE LONG PULSE DC/DC + PB 100k 100k 9V EN TURNS ON STAYS ON TURNS OFF VIN EN 10k LTC2954-2 INT INT INT μP/μC INTERRUPT INTERRUPT PB KILL KILL 2954 TA01b GND ONT PDT 2954 TA01a 1μF tPDT = 6.4 SECONDS 2954fb 1

LTC2954 ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage (V ) ..................................–0.3V to 33V Operating Temperature Range IN Input Voltages LTC2954C-1 .............................................0°C to 70°C PB ............................................................–6V to 33V LTC2954C-2 .............................................0°C to 70°C ONT ......................................................–0.3V to 2.7V LTC2954I-1 ..........................................–40°C to 85°C PDT .......................................................–0.3V to 2.7V LTC2954I-2 ..........................................–40°C to 85°C KILL .........................................................–0.3V to 7V Storage Temperature Range Output Voltages DFN Package .....................................–65°C to 125°C INT .........................................................–0.3V to 10V TSOT-23 .............................................–65°C to 150°C EN/EN ....................................................–0.3V to 33V Lead Temperature (Soldering, 10 sec) ...................300°C PIN CONFIGURATION TOP VIEW TOP VIEW GND 1 8 INT VIN 1 8 KILL ONT 2 7 EN/EN 9 PB 2 7 PDT PB 3 6 PDT ONT 3 6 EN/EN VIN 4 5 KILL GND 4 5 INT TS8 PACKAGE DDB PACKAGE 8-LEAD PLASTIC TSOT-23 8-LEAD (3mm (cid:115) 2mm) PLASTIC DFN TJMAX = 125°C, θJA = 140°C/W TJMAX = 125°C, θJA = 165°C/W EXPOSED PAD (PIN 9) PCB GND CONNECTION OPTIONAL 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/ 2954fb 2

LTC2954 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25°C. V = 2.7V to 26.4V, unless otherwise noted. (Note 2) A IN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Supply Voltage Range Steady State Operation l 2.7 26.4 V IN I V Supply Current System Power-On, V = 2.7V to 24V l 6 12 μA IN IN IN V V Undervoltage Lockout V Falling l 2.2 2.3 2.5 V UVL IN IN V V Undervoltage Lockout 50 400 700 mV UVL(HYST) IN Hysteresis Pushbutton, Enable (PB, EN/EN)) V PB Voltage Range Single-Ended l –1 26.4 V PB(MIN, MAX) I PB Input Current 2.5V < V < 26.4V l ±1 μA PB PB V = 1V l –1 –6 –12 μA PB V = 0.6V l –3 –9 –15 μA PB V PB Input Threshold PB Falling l 0.6 0.8 1 V PB(VTH) V PB Open Circuit Voltage I = –1μA 1 1.6 2 V PB(VOC) PB tEN,LOCKOUT EN/EN Lockout Time (Note 5) Enable Released → Enable Asserted l 200 256 325 ms I EN/EN Leakage Current V = 1V, Sink Current Off l ±0.1 μA EN(LKG) EN/EN V = 26.4V, Sink Current Off l ±1 μA EN/EN V EN/EN Voltage Output Low I = 500μA l 0.11 0.4 V EN(VOL) EN/EN Power-On Timing Pin (ONT) I ONT Pull-Up Current V = 0V l –2.4 –3 –3.6 μA ONT(PU) ONT I ONT Pull-Down Current V = 1.3V l 2.4 3 3.6 μA ONT(PD) ONT tDB, ON Internal Turn-On Debounce Time ONT Pin Float, PB Falling → Enable Asserted l 26 32 41 ms t Additional Adjustable Turn-On Time C = 1500pF l 9 11.5 13.5 ms ONT ONT Power-Down Timing Pin (PDT) I PDT Pull-Up Current V = 0V l –2.4 –3 –3.6 μA PDT(PU) PDT I PDT Pull-Down Current V = 1.3V l 2.4 3 3.6 μA PDT(PD) PDT tDB,OFF Turn-Off Interrupt Debounce Time PB Falling → INT Falling l 26 32 41 ms tPD,MIN Internal PB Power-Down Debounce PDT Pin Float, PB Falling → Enable Released l 52 64 82 ms Time (Note 4) t Additional Adjustable PB C = 1500pF l 9 11.5 13.5 ms PDT PDT Power-Down Debounce Time tINT,MIN Minimum INT Pulse Width INT Asserted → INT Released l 26 32 41 ms tINT,MAX Maximum INT Pulse Width CPDT = 1500pF, INT Asserted → INT Released l 35 43.5 54.5 ms μP Handshake Pins (INT, KILL) I INT Leakage Current V = 3V l ±1 μA INT(LKG) INT V INT Output Voltage Low I = 3mA l 0.11 0.4 V INT(VOL) INT V KILL Input Threshold Voltage KILL Falling l 0.57 0.6 0.63 V KILL(TH) V KILL Input Threshold Hysteresis l 10 30 50 mV KILL(HYST) I KILL Leakage Current V = 0.6V l ±0.1 μA KILL(LKG) KILL t KILL Minimum Pulse Width l 30 μs KILL(PW) t KILL(PD) KILL Propagation Delay KILL Falling → Enable Released l 30 μs t KILL,ON BLANK KILL Turn-On Blanking (Note 3) KILL = Low, Enable Asserted → Enable Released l 400 512 650 ms 2954fb 3

LTC2954 ELECTRICAL CHARACTERISTICS Note 1: Stresses beyond those listed under Absolute Maximum Ratings thus turning off system power. This time delay does not include t DB,ON may cause permanent damage to the device. Exposure to any Absolute or t . ONT Maximum Rating condition for extended periods may affect device Note 4: To manually force an immediate release of the EN/EN pin, the reliability and lifetime. pushbutton input must be held low for at least t (internal default PD,MIN Note 2: All currents into pins are positive; all voltages are referenced to power-down timer) + t (adjustable by placing external capacitor at PDT GND unless otherwise noted. PDT pin). Note 3: The KILL turn-on blanking timer period is the waiting period Note 5: The enable lockout time is designed to allow an application to immediately after the enable output is asserted. This blanking time allows properly power-down such that the next power-up sequence starts from a sufficient time for the DC/DC converter and the μP to perform power-up consistent powered-down configuration. PB is ignored during this lockout tasks. The KILL and PB inputs are ignored during this period. If KILL time. This time delay does not include t or t . DB,ON ONT remains low at the end of this time period, the enable output is released, TYPICAL PERFORMANCE CHARACTERISTICS Internal Default Turn-On Supply Current vs Temperature Supply Current vs Supply Voltage Debounce Time (t ) vs V DB, ON IN 10 15 50 VIN = 26.4V TA = 25°C 8 12 T = 25°C 40 T = 85°C VIN = 3.3V I (μA)VIN 64 VIN = 2.7V I (μA)VIN 96 T = –40°C (ms)DB, ON 2300 t 2 3 10 0 0 0 –50 –25 0 25 50 75 100 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 TEMPERATURE (°C) VIN (V) VIN (V) 2954 G01 2954 G02 2954 G03 Turn-On Debounce Time (t + ONT Pull-Up Current Turn-Off Debounce Time (t ) DB, ON DB, OFF t ) vs ONT External Capacitance vs Temperature vs V ONT IN 10000 –3.4 50 TA = 25°C TA = 25°C VIN = 3.3V A) 40 μ –3.2 ms) 1000 NT ( + t (DB, ONONT 100 ULL-UP CURRE –3.0 VIN = 2.7VVIN = 26.4V t (ms)DB, OFF 3200 t P NT –2.8 O 10 10 –2.6 0 1 10 100 1000 –50 –25 0 25 50 75 100 0 5 10 15 20 25 30 ONT EXTERNAL CAPACITANCE (nF) TEMPERATURE (°C) VIN (V) 2954 G04 2954 G05 2954 G06 2954fb 4

LTC2954 TYPICAL PERFORMANCE CHARACTERISTICS PB Power-Down Debounce Time Internal Default PB Power-Down (tPD,MIN + tPDT) vs PDT External PDT Pull-Up Current Debounce Time (t ) vs V Capacitance vs Temperature PD,MIN IN 70 10000 –3.4 TA = 25°C 60 VIN = 3.3V TA = 25°C A) μ –3.2 50 ms) 1000 NT ( ms) 40 (DT RRE VIN = 26.4V t (PD, MIN 3200 t + tPD, MINP 100 DT PULL-UP CU ––32..08 VIN = 2.7V P 10 0 10 –2.6 0 5 10 15 20 25 30 1 10 100 1000 –50 –25 0 25 50 75 100 VIN (V) PDT EXTERNAL CAPACITANCE (nF) TEMPERATURE (°C) 2954 G07 2954 G08 2954 G09 PB Voltage vs External PB PB Current vs PB Voltage Resistance to Ground –250 300 TA = 25°C VIN = 3.3V VIN = 3.3V 250 –200 RRENT (μA)–150 LTAGE (mV)125000 TA = 100°C TA = 25°C PB CU–100 PB VO100 TA = –45°C –50 50 0 0 –10 –5 0 5 10 15 20 25 30 0 5 10 15 20 PB VOLTAGE (V) EXTERNAL PB RESISTANCE TO GROUND (kΩ) 2954 G10 2954 G11 EN/EN VOL vs Current Load EN (LTC2954-1) Voltage vs VIN EN (LTC2954-2) Voltage vs VIN 600 1.0 4 TA = 25°C TA = 25°C TA = 25°C VIN = 3.3V 100k PULL-UP FROM EN TO VIN 100k PULL-UP FROM EN TO VIN 500 0.8 3 mV) 400 E ( 0.6 LTAG 300 N (V) N (V) 2 O E E N V 0.4 N/E 200 E 1 0.2 100 0 0 0 0.0 0.5 1.0 1.5 2.0 2.5 0 1 2 3 4 0 1 2 3 4 EN/EN CURRENT LOAD (mA) VIN (V) VIN (V) 2954 G12 2954 G13 2954 G14 2954fb 5

LTC2954 PIN FUNCTIONS (TSOT-23/DFN) V (Pin 1/Pin 4): Power Supply Input: 2.7V to 26.4V. and held low (t + t ) during normal operation. This IN PD,MIN PDT pin can connect directly to a DC/DC converter shutdown PB (Pin 2/Pin 3): Pushbutton Input. Connecting PB to pin that provides an internal pull-up. Otherwise a pull-up ground through a momentary switch provides on/off resistor to an external supply is required. The operating control via the EN/EN and INT outputs. An internal 100k range for this low leakage pin is 0V to 26.4V. pull-up resistor connects to an internal 1.9V bias voltage. The rugged PB input withstands ±10kV ESD HBM and EN (LTC2954-2, Pin 6/Pin 7): Open Drain Enable Bar can be pulled up to 26.4V externally without consuming Output. This pin is intended to enable system power. EN is extra current. asserted low after a valid PB turn-on event (t + t ). DB,ON ONT EN releases high if: a) KILL is not driven high (by μP) within ONT (Pin 3/Pin 2): Turn-On Time Input. Placing an external 512ms of the initial valid PB power turn-on event, b) KILL capacitor to ground determines the additional time (6.4 is driven low during normal operation, c) PB is pressed seconds/μF) the PB pin must be held low before the enable and held low (t + t ) during normal operation. This output is asserted. Floating this pin results in a default PD,MIN PDT pin can connect directly to a DC/DC converter shutdown turn on debounce time of 32ms. pin that provides an internal pull-up. Otherwise a pull-up GND (Pin 4/Pin 1): Device Ground. resistor to an external supply is required. The operating range of this pin is 0V to 26.4V. INT (Pin 5/Pin 8): Open Drain Interrupt Output. After a pushbutton turn-off event is detected (tDB,OFF), the LTC2954 PDT (Pin 7/Pin 6): Power-Down Time Input. A capacitor interrupts the system (μP) by asserting the INT pin low. to ground determines the additional time (6.4 seconds/μF) The μP would perform power-down and housekeeping that the pushbutton must be held low before immediately tasks and then assert the KILL pin low, thus releasing the releasing the EN/EN and INT outputs. Floating this pin enable output. The INT pulse width is a minimum of 32ms results in a pushbutton power-down time of 64ms. and stays low as long as PB is asserted. If PB is asserted KILL (Pin 8/Pin 5): Kill Input. Forcing KILL low releases the for longer than t + t , the INT and EN/EN outputs PD,MIN PDT enable output. During system turn-on, this pin is blanked by are immediately released. a 512ms internal timer (t ) to allow the system KILL,ON BLANK EN (LTC2954-1, Pin 6/Pin 7): Open Drain Enable Output. to pull KILL high. This pin has an accurate 0.6V threshold This pin is intended to enable system power. EN is asserted and can be used as a voltage monitor input. If unused, high after a valid PB turn-on event (tDB,ON + tONT). EN is connect to a low voltage output supply (see Figure 6). released low if: a) KILL is not driven high (by μP) within Exposed Pad (Pin 9 DFN Only): Exposed Pad may be left 512ms of the initial valid PB power turn-on event, b) KILL open or connected to device ground. is driven low during normal operation, c) PB is pressed 2954fb 6

LTC2954 BLOCK DIAGRAM EN (–1) EN (–2) HIGH VOLTAGE VIN 1.5k REGULATOR 2.4V 2.7V TO 26.4V 29V 2.4V ZENER OSCILLATOR KILL 100k PB LOGIC 10μS FILTER DEBOUNCE 0.6V 0.8V INT OSCILLATOR GND ONT PDT 2954 BD TIMING DIAGRAMS tKILL(PW) KILL tKILL(PD) EN/EN 2954 TD01 2954fb 7

LTC2954 TIMING DIAGRAMS PB PB & KILL IGNORED tDB, ON tONT tKILL, ON BLANK ONT 16 CYCLES EN (LTC2954-1) 2954 TD02 Power-On Timing PB PB IGNORED tDB, OFF t < tPDT PDT tPD,MIN INT tINT,MIN 2954 TD03 Off Interrupt Timing, PB Pressed and Released, Enable Remains Active PB PB IGNORED tDB, OFF 16 CYCLES PDT tPD,MIN tPDT INT tINT,MAX EN (LTC2954-1) 2954 TD04 Forced Off, Power-Down Timing, PB Pressed and Held Low for t > (t + t ) PD,MIN PDT 2954fb 8

LTC2954 APPLICATIONS INFORMATION Description maximum time required to power up the DC/DC converter and the μP. If KILL is not brought high during this 512ms The LTC2954 is a pushbutton on/off controller that provides time window, the enable output is released. The assump- control of system power via a pushbutton interface. An tion is that 512ms is sufficient time for the system to enable output toggles system power while an interrupt power up. output provides debounced pushbutton status. The inter- rupt output can be used in menu driven applications to Turn Off request a system power-down. A power kill input allows a microprocessor or system to release the enable output, To initiate a power-down sequence, assert the INT output effectively powering down the system. Independently ad- low by pressing the pushbutton for a minimum of 32ms justable on and off timers allow dependable pushbutton (tDB,OFF). The interrupt signal serves as a power-down control of the enable output and resistance to accidental request to the μP. The μP would then perform power-down toggling of system power. and housekeeping tasks and assert KILL low when done. This in turn releases the enable output, thus shutting off The length of time the pushbutton input (PB) must be held system power. low in order to toggle the enable (EN/EN) output on and off is independently adjustable with external capacitors Adjustable Power-Down Timer at the ONT/PDT pins, respectively. During normal opera- The LTC2954 provides a failsafe feature that allows the tion, the interrupt output (INT) is asserted 32ms after PB user to turn off system power (via PB) under system fault goes low. INT then tracks PB until either PB or EN/EN is conditions. For cases when the μP fails to respond to the released. See Timing Diagrams on page 8. interrupt signal, the user can force an immediate power- The KILL input is used to immediately release the enable down by pressing and holding down the pushbutton. The output. During a normal power-down sequence, INT re- length of time that PB must be held low is given by a fixed quests a system power-down. The μP then performs its internal 64ms delay (t ) plus an adjustable power- PD,MIN housekeeping tasks and then sets KILL low. If the μP fails down timer delay (t , see Timing Diagrams on page 8). PDT to set KILL low, the user can force a system shutdown by The adjustable delay is set by placing an optional external pressing and holding the pushbutton until the PDT timer capacitor on the PDT pin. Use the following equation to expires. calculate the capacitance for the desired delay. C is the PDT PDT external capacitor (μF): Turn On C = 1.56 × 10-4 [μF/ms] • (t – 1ms) PDT PDT When power is first applied to the LTC2954, the part ini- tializes the output pins. Any DC/DC converters connected Simplified Power On/Off Sequence to the EN/EN pin will therefore be held off. To assert the Figure 1 shows a simplified LTC2954-1 power-on and enable output, PB must be held low for a minimum of power-off sequence. A high to low transition on PB (t ) 32ms (t , ). The LTC2954 provides additional turn-on 1 DB ON initiates the power on sequence. In order to assert the debounce time (t ) via an optional capacitor connected ONT enable output, the PB pin must stay low continuously (PB to the ONT pin. The following equation describes the ad- high resets timers) for a time controlled by the default ditional time that PB must be held low before asserting the 32ms and the external ONT capacitor (t –t ). Once EN enable output. C is the ONT external capacitor (μF): 2 1 ONT goes high (t ), an internal 512ms blanking timer is started. 2 C = 1.56 × 10–4 [μF/ms] • (t – 1ms) ONT ONT This blanking timer is designed to give sufficient time for Once the enable output is asserted, any DC/DC converters the DC/DC converter to reach its final voltage, and to allow connected to this pin are turned on. The KILL input from the μP enough time to perform power-on tasks. the μP is ignored during a succeeding 512ms blanking The KILL pin must be pulled high within 512ms of the EN time (t ). This blanking time represents the KILL,ON BLANK pin going high. Failure to do so results in the EN pin going 2954fb 9

LTC2954 APPLICATIONS INFORMATION t1 t2 t3 t4 t5 t6 t7 t8 t9 PB PB & KILL IGNORED PB IGNORED tDB, ON tKILL, ON BLANK tDB, OFF ONT tONT PDT tPD, MIN INT t < tPDT KILL XXX DON'T CARE μP DRIVES KILL LOW EN 2954 F01 Figure 1. Simplified Power On/Off Sequence for LTC2954-1. μP Asserts KILL After an Interrupt tABORT PB tDB,ON + tONT 512ms INTERNAL TIMER POWER-ON TIMING POWER TURNED OFF EN μP FAILED TO SET KILL HIGH KILL 2954 F02 Figure 2. KILL Remaining Low Aborts Power-On Sequence for LTC2954-1 2954fb 10

LTC2954 APPLICATIONS INFORMATION low 512ms after it went high. Note that the LTC2954 does Aborted Power-On Sequence not sample KILL and PB until after the 512ms internal timer The power-on sequence is aborted when the KILL remains has expired. The reason PB is ignored is to ensure that low at the end of the 512ms blanking time. Figure 2 is a the system is not forced off while powering on. Once the simplified version of an aborted power-on sequence. At 512ms timer expires (t ), the release of the PB pin is then 4 time t , since KILL is still low, EN pulls low (thus ABORT debounced with an internal 32ms timer. The system has turning off the DC/DC converter). now properly powered on and the LTC2954 monitors PB and KILL for a turn-off command while consuming only μP Turns Off Power During Normal Operation 6μA of supply current. Once the system has powered on and is operating nor- A high to low transition on PB (t ) starts the power-off 5 mally, the μP can turn off power by setting KILL low, as sequence debounce timer. In order to assert the interrupt shown in (Figure 3). At time t , KILL is set low by the KILL output (INT), PB must stay low continuously (PB high μP. This immediately pulls EN low, thus turning off the resets debounce timer) for 32ms (t –t ). At the comple- 6 5 DC/DC converter. tion of the power-down debounce timer (t ), an internal 6 interrupt timer keeps the interrupt output low for at least DC/DC Turn Off Blanking 32ms, even if PB is released between t and t . If PB is 6 7 When the DC/DC converter is turned off, it can take a sig- low at the end of this 32ms internal timer (t ), the external 7 nificant amount of time for its output to decay to ground. It adjustable power-down timer is started. The capacitor is desirable to wait until the output of the DC/DC converter placed at the PDT pin will determine the time period of is near ground before allowing the user (via PB) to restart this timer. If the pushbutton is released prior to 16 cycles the converter. This condition guarantees that the μP has of the PDT pin, the interrupt output will go high (t ). Note 8 always powered down completely before it is restarted. that the enable output is not directly changed by this interrupt pulse. The function of the interrupt signal is to Figure 4 shows the μP turning power off. After a low on initiate a software shutdown. At t , the μP has performed KILL releases enable, the internal 256ms timer ignores the 9 its power-down functions and asserted the KILL input PB pin. This is shown as t in (Figure 4). EN/EN, LOCKOUT 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 tEN/EN, LOCKOUT to low transition. PB POWER ON PB IGNORED tKILL DC/DC TURNS OFF PB 256ms PB BLANKING (INTERNAL DC/DC SIGNAL) TURNS OFF EN EN μP SETS KILL LOW μP SETS KILL LOW KILL XXX DON’T CARE KILL XXX DON’T CARE 2954 F03 2954 F04 Figure 3. μP Turns Off Power (LTC2954-1) Figure 4. DC/DC Turn-Off Blanking (LTC2954-1) 2954fb 11

LTC2954 APPLICATIONS INFORMATION LTC2954-1, LTC2954-2 Versions without latching up the device. PB has an ESD HBM rating of ±10kV. If the pushbutton switch connected to PB exhib- The LTC2954-1 (high true EN) and LTC2954-2 (low true its high leakage current, then an external pull-up resistor EN) differ only by the polarity of the high voltage (33V ABS to V is recommended. Furthermore, if the pushbutton MAX), enable pin. The LTC2954-1 EN pin is a low leakage IN switch is physically located far from the LTC2954 PB pin, high true open drain output designed to drive the shutdown parasitic capacitances may couple onto the high imped- pin of DC/DC converters. The LTC2954-2 is a low leakage, ance PB input. Additionally, parasitic series inductance low true open drain enable output designed to drive the may cause unpredictable ringing at the PB pin. Placing gate of an external PFET. The LTC2954-2 provides a user a 5.1k resistor from the PB pin to the pushbutton switch manual power path control. would mitigate parasitic inductance problems. Placing a 0.1μF capacitor on the PB pin would lessen the impact of High Voltage Pins parasitic capacitive coupling. The V , PB and EN/EN pins can operate at voltages up to IN 26.4V. PB can, additionally, operate below ground (–6V) TYPICAL APPLICATIONS Voltage Monitoring with KILL Input enough to keep leakage currents from tripping the 0.6V KILL comparator. The KILL pin can be used as a voltage monitor. Figure 5 shows an application where the KILL pin has a dual func- The DC/DC converter shown has an internal pull-up cur- tion. It is driven by a low leakage open drain output of the rent on its SHDN pin. A pull-up resistor on EN is thus not μP. It is also connected to a resistive divider that monitors needed. battery voltage (V ). When the battery voltage falls be- IN low the set value, the voltage at the KILL pin falls below Operation Without μP 0.6V and the EN pin is quickly pulled low. Note that the Figure 6 shows how to connect the KILL pin when there resistor values should be as large as possible, but small is no circuitry available to drive it. The minimum pulse VIN = 9V VIN = 9V VIN VOUT 3.3V VIN VOUT 3.3V LT1767-3.3 LT1767-3.3 R3 806k SHDN** SHDN** 1% R2 100k 1% R1 100k R1 C4 VIN EN 10k C4 VIN EN LTC2954-1 LTC2954-1 0.1μF 0.1μF INT INT INT μP PB KILL KILL PB KILL GND ONT PDT (OPEN DRAIN) GNDONT PDT + C3* 2954 F05 CONT* CPDT* 0.01μF CONT* CPDT* * OPTIONAL 0.033μF 1μF * OPTIONAL 0.033μF 1μF ** SHDN INTERNALLY PULLED ** SHDN INTERNALLY 2954 F06 UP BY THE LT1767-3.3 PULLED UP BY THE LT1767-3.3 Figure 5. Input Voltage Monitoring with KILL Input Figure 6. No μP Application 2954fb 12

LTC2954 TYPICAL APPLICATIONS width detected is 30μs. If there are glitches on the resis- PFET through a resistive divider. The KILL pin serves as tor pull-up voltage that are wider than 30μs and transition a voltage monitor. When V drops below 6V, causing a OUT below 0.6V, then an appropriate bypass capacitor should KILL voltage below V , the EN pin becomes an open KILL(TH) be connected to the KILL pin. The optional C external circuit 30μs later. Since the PDT pin is open-circuited, the PDT capacitor extends the length of time (beyond 64ms) that power-down debounce time defaults to 64ms. the PB input must be held low before releasing the enable output. PB Pin in a Noisy Environment The rugged PB pin is designed to operate in noisy environ- High Voltage PowerPath Switching ments. Transients below ground (>–6V) and above V IN The high voltage EN open drain output of the LTC2954-2 (<33V) will not damage the rugged PB pin. Additionally, is designed to switch on/off an external power PFET. This the PB pin can withstand ESD HBM strikes up to ±10kV. allows a user to connect/disconnect a power supply (or In order to keep external noise from coupling inside the battery) to its load by toggling the PB pin. Figure 7 shows LTC2954, place an R-C network close to the PB pin. A 5.1k the LTC2954-2 controlling a two cell Li-Ion battery ap- resistor and a 0.1μF capacitor should suffice for most noisy plication. The KILL pin is connected to the output of the applications (see Figure 8). VOUT R5 M1 100k VOUT,TRIP POINT = 6V R9 100k R1 4.2V + 909k SINGLE CELL 1% Li-Ion BATTERY C4 VIN EN 0.1μF CERAMIC LTC2954-2 INT 4.2V + OPTIONAL GLITCH SINGLE CELL PB KILL VTH = 0.6V INPUT FILTER CAPACITOR Li-Ion BATTERY GND ONT PDT R4 C3* 100k 0.1μF CONT* 1% 0.033μF *OPTIONAL 2954 F07 Figure 7. PowerPath Control with 6V Undervoltage Detect VIN PARASITICS TRACE CAPACITANCE R6 VIN EN 5.1k PB LTC2954-1 INT NOISE TRACE C5 KILL INDUCTANCE 0.1μF GND ONT PDT DETAILS OMITTED FOR CLARITY 2954 F08 Figure 8. Noisy PB Trace 2954fb 13

LTC2954 TYPICAL APPLICATIONS External Pull-Up Resistor On PB Reverse Battery Protection An internal pull-up resistor on the PB pin makes an ex- To protect the LTC2954 from a reverse battery connec- ternal pull-up resistor unnecessary. Leakage current on tion, place a 1k resistor in series with the V pin (see IN the PB board trace, however, will affect the open circuit Figure 10). 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 V is recommended (see Figure 9). IN LTC2954-1/ VIN VIN LTC2954-2 2.4V R7 10k 100k PB EXTERNAL BOARD LEAKAGE CURRENT >2μA GND PINS OMITTED FOR CLARITY 2954 F09 IF EXTERNAL PARASITIC BOARD LEAKAGE >2μA, USE EXTERNAL PULL-UP RESISTOR Figure 9. External Pull-Up Resistor On PB Pin 2954fb 14

LTC2954 PACKAGE DESCRIPTION DDB Package 8-Lead Plastic DFN (3mm × 2mm) (Reference LTC DWG # 05-08-1702 Rev B) 0.61 ±0.05 3.00 ±0.10 R = 0.115 0.40 ± 0.10 (2 SIDES) R = 0.05 TYP (2 SIDES) TYP 5 8 0.70 ±0.05 2.55 ±0.05 2.00 ±0.10 1.15 ±0.05 PIN 1 BAR (2 SIDES) PIN 1 TOP MARK R = 0.20 OR PACKAGE (SEE NOTE 6) 0.56 ± 0.05 0.25 × 45° OUTLINE (2 SIDES) 4 1 CHAMFER 0.25 ± 0.05 0.200 REF 0.75 ±0.05 0.25 ± 0.05 (DDB8) DFN 0905 REV B 0.50 BSC 0.50 BSC 2.20 ±0.05 2.15 ±0.05 (2 SIDES) (2 SIDES) 0 – 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS BOTTOM VIEW—EXPOSED PAD 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 2954fb 15

LTC2954 PACKAGE DESCRIPTION TS8 Package 8-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1637 Rev A) 2.90 BSC 0.40 0.65 (NOTE 4) MAX REF 1.22 REF 1.50 – 1.75 3.85 MAX2.62 REF 1.4 MIN 2.80 BSC (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT 0.22 – 0.36 0.65 BSC PER IPC CALCULATOR 8 PLCS (NOTE 3) 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 1.95 BSC 0.09 – 0.20 TS8 TSOT-23 0710 REV A (NOTE 3) 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 2954fb 16

LTC2954 REVISION HISTORY (Revision history begins at Rev B) REV DATE DESCRIPTION PAGE NUMBER B 2/11 Revised Pin Descriptions for EN and EN pins 6 Revised notes for Figures 5 and 6 in Typical Applications 12 2954fb Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, 17 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.

LTC2954 TYPICAL APPLICATION VIN VOUT + 9V R8 R5 BATTERY 1k 910k LT1761-1.8 SHDN 1.8V R1 C4 VIN EN 10k 0.1μF LTC2954-1 INT INT μP PB KILL KILL GND ONT PDT CONT* CPDT* 0.033μF 1μF *OPTIONAL 2954 TA02 Figure 10. Reverse Battery Protection RELATED PARTS 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 6.5V Shunt Regulator for High Voltage Operation Voltage Monitor 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 Automatic Low Loss Switchover Between DC Sources Supervisor LTC2953 Pushbutton ON/OFF Controller with Voltage High Voltage Pushbutton Controller with 200ms Voltage Reset Monitor Monitoring 2954fb 18 Linear Technology Corporation LT 0211 REV B • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2006

Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: A nalog Devices Inc.: LTC2954CTS8-1#TRPBF LTC2954CTS8-2#PBF LTC2954IDDB-2#TRM LTC2954ITS8-1#TRM LTC2954IDDB- 1#TRMPBF LTC2954CDDB-1#PBF LTC2954ITS8-2#TRM LTC2954CDDB-1#TR LTC2954IDDB-2#TRPBF LTC2954IDDB-1#PBF LTC2954CDDB-1#TRMPBF LTC2954CDDB-2#TR LTC2954IDDB-2 LTC2954ITS8-2#PBF LTC2954ITS8-1#PBF LTC2954ITS8-1#TRMPBF LTC2954CDDB-2#TRM LTC2954ITS8-2#TR LTC2954IDDB- 2#TRMPBF LTC2954CTS8-1#PBF LTC2954CDDB-2#TRPBF LTC2954ITS8-2#TRMPBF LTC2954ITS8-1 LTC2954CDDB-1#TRM LTC2954CTS8-1#TR LTC2954IDDB-2#PBF LTC2954CTS8-2#TR LTC2954CDDB-1 LTC2954CTS8-1#TRMPBF LTC2954CTS8-2#TRMPBF LTC2954IDDB-1#TR LTC2954ITS8-1#TRPBF LTC2954CTS8-2#TRM LTC2954CTS8-2#TRPBF LTC2954ITS8-1#TR LTC2954CTS8-2 LTC2954CDDB-2 LTC2954CTS8-1 LTC2954CDDB-2#PBF LTC2954CDDB-1#TRPBF LTC2954IDDB-2#TR LTC2954IDDB-1 LTC2954IDDB-1#TRM LTC2954CDDB-2#TRMPBF LTC2954ITS8-2 LTC2954IDDB-1#TRPBF LTC2954CTS8-1#TRM LTC2954ITS8-2#TRPBF