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ltc2954 1 2954fb pushbutton on/off controller with p 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 (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. 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: 6a 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 p 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 v in v out en int kill int kill ltc2954-2 ont pdt dc/dc p/c 9v 10k t pdt = 6.4 seconds 100k 100k 2954 ta01a 1f pb gnd v in + turn-on pulse turns on stays on interrupt interrupt turns off short pulse long pulse pb int 2954 ta01b en
ltc2954 2 2954fb supply voltage (v in ) .................................. C0.3v to 33v input voltages pb ............................................................ C6v to 33v ont ...................................................... C0.3v to 2.7v pdt ....................................................... C0.3v to 2.7v kill ......................................................... C0.3v to 7v output voltages int ......................................................... C0.3v to 10v en/ en .................................................... C0.3v to 33v (note 1) operating temperature range ltc2954c-1 ............................................. 0c to 70c ltc2954c-2 ............................................. 0c to 70c ltc2954i-1 ..........................................C40c to 85c ltc2954i-2 ..........................................C40c to 85c storage temperature range dfn package ..................................... C65c to 125c tsot-23 ............................................. C65c to 150c lead temperature (soldering, 10 sec) ................... 300c 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 0c to 70c ltc2954cddb-2#pbf ltc2954cddb-2#trpbf lcnj 8-lead (3mm 2mm) plastic dfn 0c to 70c ltc2954iddb-1#pbf ltc2954iddb-1#trpbf lcjg 8-lead (3mm 2mm) plastic dfn C40c to 85c ltc2954iddb-2#pbf ltc2954iddb-2#trpbf lcnj 8-lead (3mm 2mm) plastic dfn C40c to 85c ltc2954cts8-1#pbf ltc2954cts8-1#trpbf ltcjh 8-lead plastic tsot-23 0c to 70c ltc2954cts8-2#pbf ltc2954cts8-2#trpbf ltcnk 8-lead plastic tsot-23 0c to 70c ltc2954its8-1#pbf ltc2954its8-1#trpbf ltcjh 8-lead plastic tsot-23 C40c to 85c ltc2954its8-2#pbf ltc2954its8-2#trpbf ltcnk 8-lead plastic tsot-23 C40c to 85c lead based finish tape and reel part marking* package description temperature range ltc2954cddb-1 ltc2954cddb-1#tr lcjg 8-lead (3mm 2mm) plastic dfn 0c to 70c ltc2954cddb-2 ltc2954cddb-2#tr lcnj 8-lead (3mm 2mm) plastic dfn 0c to 70c ltc2954iddb-1 ltc2954iddb-1#tr lcjg 8-lead (3mm 2mm) plastic dfn C40c to 85c ltc2954iddb-2 ltc2954iddb-2#tr lcnj 8-lead (3mm 2mm) plastic dfn C40c to 85c ltc2954cts8-1 ltc2954cts8-1#tr ltcjh 8-lead plastic tsot-23 0c to 70c ltc2954cts8-2 ltc2954cts8-2#tr ltcnk 8-lead plastic tsot-23 0c to 70c ltc2954its8-1 ltc2954its8-1#tr ltcjh 8-lead plastic tsot-23 C40c to 85c ltc2954its8-2 ltc2954its8-2#tr ltcnk 8-lead plastic tsot-23 C40c to 85c 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 v in int en/en pdt kill t jmax = 125c, ja = 165c/w exposed pad (pin 9) pcb gnd connection optional v in 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 t jmax = 125c, ja = 140c/w pin configuration
ltc2954 3 2954fb the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. v in = 2.7v to 26.4v, unless otherwise noted. (note 2) symbol parameter conditions min typ max units v in supply voltage range steady state operation l 2.7 26.4 v i in v in supply current system power-on, v in = 2.7v to 24v l 612 a v uvl v in undervoltage lockout v in falling l 2.2 2.3 2.5 v v uvl(hyst) v in undervoltage lockout hysteresis 50 400 700 mv pushbutton, enable (pb, en/en)) v pb(min, max) pb voltage range single-ended l C1 26.4 v i pb pb input current 2.5v < v pb < 26.4v v pb = 1v v pb = 0.6v l l l C1 C3 C6 C9 1 C12 C15 a a a v pb (vth) pb input threshold pb falling l 0.6 0.8 1 v v pb(voc) pb open circuit voltage i pb = C 1a 1 1.6 2 v t en, lockout en/en lockout time (note 5) enable released enable asserted l 200 256 325 ms i en(lkg) en/en leakage current v en/ en = 1v, sink current off v en/ en = 26.4v, sink current off l l 0.1 1 a a v en(vol) en/en voltage output low i en/ en = 500a l 0.11 0.4 v power-on timing pin (ont) i ont(pu) ont pull-up current v ont = 0v l C2.4 C3 C3.6 a i ont(pd) ont pull-down current v ont = 1.3v l 2.4 3 3.6 a t db, on internal turn-on debounce time ont pin float, pb falling enable asserted l 26 32 41 ms t ont additional adjustable turn-on time c ont = 1500pf l 9 11.5 13.5 ms power-down timing pin (pdt) i pdt(pu) pdt pull-up current v pdt = 0v l C2.4 C3 C3.6 a i pdt(pd) pdt pull-down current v pdt = 1.3v l 2.4 3 3.6 a t db, off turn-off interrupt debounce time pb falling int falling l 26 32 41 ms t pd,min internal pb power-down debounce t ime (note 4) pdt pin float, pb falling enable released l 52 64 82 ms t pdt additional adjustable pb power-down debounce time c pdt = 1500pf l 9 11.5 13.5 ms t int ,min minimum int pulse width int asserted int released l 26 32 41 ms t int ,max maximum int pulse width c pdt = 1500pf, int asserted int released l 35 43.5 54.5 ms p handshake pins (int, kill) i int(lkg) int leakage current v int = 3v l 1 a v int(vol) int output voltage low i int = 3ma l 0.11 0.4 v v kill(th) kill input threshold voltage kill falling l 0.57 0.6 0.63 v v kill(hyst) kill input threshold hysteresis l 10 30 50 mv i kill(lkg) kill leakage current v kill = 0.6v l 0.1 a t kill (pw) kill minimum pulse width l 30 s t kill(pd) kill propagation delay kill falling enable released l 30 s t kill , on blank kill turn-on blanking (note 3) kill = low, enable asserted enable released l 400 512 650 ms electrical characteristics
ltc2954 4 2954fb supply current vs temperature turn-on debounce time (t db, on + t ont ) vs ont external capacitance supply current vs supply voltage ont pull-up current vs temperature turn-off debounce time (t db, off ) vs v in internal default turn-on debounce time (t db, on ) vs v in 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 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 t db,on or t ont . note 4: to manually force an immediate release of the en/en pin, the pushbutton input must be held low for at least t pd,min (internal default power-down timer) + t pdt (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 t db,on or t ont . 2954 g01 temperature (c) C50 i vin (a) 10 8 6 4 2 0 C25 02550 75 100 v in = 26.4v v in = 3.3v v in = 2.7v 2954 g02 0 5 10 15 20 25 30 35 v in (v) i vin (a) 15 12 9 6 3 0 t = 85c t = C 40c t = 25c 2954 g03 v in (v) 0 0 t db, on (ms) 10 20 30 40 50 5 10 15 20 25 30 t a = 25c 2954 g04 1 t db, on + t ont (ms) 100 1000 1000 10 10 100 10000 t a = 25c v in = 3.3v ont external capacitance (nf) 2954 g05 temperature (c) C50 C25 0 25 50 75 100 ont pull-up current (a) C3.4 C3.2 C3.0 C2.8 C2.6 v in = 26.4v v in = 2.7v 2954 g06 v in (v) 0 t db, off (ms) 5 1015202530 50 40 30 20 10 0 t a = 25c
ltc2954 5 2954fb pb power-down debounce time (t pd,min + t pdt ) 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 v ol vs current load en (ltc2954-2) voltage vs v in en (ltc2954-1) voltage vs v in internal default pb power-down debounce time (t pd,min ) vs v in typical performance characteristics 2954 g07 v in (v) 0 5 10 15 20 25 30 t pd, min (ms) 70 60 40 50 30 20 10 0 t a = 25c 2954 g08 1 t pd, min + t pdt (ms) 100 1000 1000 10 10 100 10000 t a = 25c v in = 3.3v pdt external capacitance (nf) 2954 g09 temperature (c) C50 C25 0 25 50 75 100 pdt pull-up current (a) C3.4 C3.2 C3.0 C2.8 C2.6 v in = 26.4v v in = 2.7v 2954 g10 pb current (a) C10010 20 30 C5 5 15 25 C250 C200 C150 C100 C50 0 pb voltage (v) t a = 25c v in = 3.3v 2954 g11 0 0 50 100 150 200 250 300 5101520 v in = 3.3v t a = 25c pb voltage (mv) external pb resistance to ground (k) t a = C45c t a = 100c 2954 g13 v in (v) 0 en (v) 4 1 2 3 t a = 25c 100k pull-up from en to v in 1.0 0.8 0.6 0.4 0.2 0 2954 g14 en (v) v in (v) 04 1 2 3 4 3 2 1 0 t a = 25c 100k pull-up from en to v in 2954 g12 en/en current load (ma) 0.0 en/en voltage (mv) 600 500 400 300 200 100 0 2.0 0.5 1.0 1.5 2.5 t a = 25c v in = 3.3v
ltc2954 6 2954fb v in (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/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 pushbutton turn-off event is detected (t db,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 t pd,min + t pdt , 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 (t db,on + t ont ). en is 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 (t pd,min + t pdt ) 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 (t db,on + t ont ). 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 (t pd,min + t pdt ) 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/f) 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 (t kill,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 7 2954fb block diagram timing diagrams logic oscillator oscillator debounce 10s filter 2.4v 29v zener 2.4v 1.5k 100k v in 2.7v to 26.4v pb gnd en (C1) en (C2) kill int ont pdt 0.8v 0.6v 2954 bd regulator high voltage kill en/en t kill (pw) t kill(pd) 2954 td01
ltc2954 8 2954fb 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 > (t pd,min + t pdt ) timing diagrams t db, on t ont pb ont 16 cycles pb & kill ignored en (ltc2954-1) t kill, on blank 2954 td02 t db, off t int ,min t < t pdt pb int pdt t pd,min 2954 td03 pb ignored pb int pdt 2954 td04 16 cycles en (ltc2954-1) t db, off pb ignored t pdt t pd,min t int ,max
ltc2954 9 2954fb 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 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 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 (t db , on ). the ltc2954 provides additional turn-on debounce time (t ont ) 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. c ont is the ont external capacitor (f): c ont = 1.56 10 C4 [f/ms] ? (t ont C 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 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 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 (t db,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 pushbutton. the length of time that pb must be held low is given by a fixed internal 64ms delay (t pd, min ) plus an adjustable power- down timer delay (t pdt , 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. c pdt is the pdt external capacitor (f): c pdt = 1.56 10 -4 [f/ms] ? (t pdt C 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 (t 1 ) 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 (t 2 Ct 1 ). once en goes high (t 2 ), 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 applications information
ltc2954 10 2954fb figure 1. simplified power on/off sequence for ltc2954-1. p asserts kill after an interrupt figure 2. kill remaining low aborts power-on sequence for ltc2954-1 applications information t 1 t 2 t db, on xxx don't care t 3 t 4 t 5 t 6 t 8 t 9 t 7 pb ont pdt en kill int pb & kill ignored 2954 f01 t kill, on blank t db, off t pd, min t ont t < t pdt pb ignored p drives kill low t abort t db,on + t ont pb kill power-on timing en 512ms internal timer power turned off 2954 f02 p failed to set kill high
ltc2954 11 2954fb 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 t abort , 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 nor- mally, 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 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 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 t en/en, lockout in (figure 4). figure 3. p 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 (t 4 ), 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 6a of supply current. a high to low transition on pb (t 5 ) 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 (t 6 Ct 5 ). at the comple- tion of the power-down debounce timer (t 6 ), an internal interrupt timer keeps the interrupt output low for at least 32ms, even if pb is released between t 6 and t 7 . if pb is low at the end of this 32ms internal timer (t 7 ), 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 (t 8 ). 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 t 9 , 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 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 (6a) and pb is monitored for a high to low transition. applications information t kill pb en dc/dc turns off 2954 f03 kill xxx dont care p sets kill low pb pb ignored en kill pb blanking (internal signal) xxx dont care 256ms power on 2954 f04 dc/dc turns off p sets kill low t en/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 v in , pb and en/en pins can operate at voltages up to 26.4v. pb can, additionally, operate below ground (C 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 v in 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 0.1f capacitor on the pb pin would lessen the impact of parasitic capacitive coupling. figure 5. input voltage monitoring with kill input figure 6. no p 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 p . it is also connected to a resistive divider that monitors battery voltage (v in ). 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 v in v out shdn** v in = 9v en int kill int kill (open drain) ltc2954-1 gnd ont pdt lt1767-3.3 p r1 10k 3.3v 2954 f05 c4 0.1f r3 806k 1% r2 100k 1% * optional ** shdn internally pulled up by the lt1767-3.3 v in c ont * 0.033f c pdt * 1f v in = 9v 3.3v r1 100k c3* 0.01f 2954 f06 + c4 0.1f pb en int kill ltc2954-1 gnd ont pdt v in c ont * 0.033f c pdt * 1f * optional ** shdn internally pulled up by the lt1767-3.3 v in v out 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 p 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 30s. if there are glitches on the resis- tor 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 c pdt 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 v out r1 909k 1% r4 100k 1% c3* 0.1f 2954 f07 c4 0.1f ceramic *optional v th = 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 v out ,trip point = 6v pb en int kill ltc2954-2 gnd ont pdt v in c ont * 0.033f pfet through a resistive divider. the kill pin serves as a voltage monitor. when v out drops below 6v, causing a kill voltage below v kill(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 environ- ments. transients below ground (> C6v) and above v in (<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). figure 8. noisy pb trace pb v in ltc2954-1 gnd ont r6 5.1k 2954 f08 trace capacitance parasitics c5 0.1f details omitted for clarity trace inductance noise en int kill pdt v in
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 (>2a), the pb voltage may fall close to the threshold window. to mitigate the effect of the board leakage, a 10k resistor to v in 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 v in pin (see figure 10). typical applications pb v in ltc2954-1/ ltc2954-2 gnd external board leakage current 100k 2.4v r7 10k 2954 f09 >2a pins omitted for clarity if external parasitic board leakage >2a, use external pull-up resistor v in
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?xposed 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) 1 4 8 5 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 C 1.75 (note 4) 2.80 bsc 0.22 C 0.36 8 plcs (note 3) datum a 0.09 C 0.20 (note 3) ts8 tsot-23 0710 rev a 2.90 bsc (note 4) 0.65 bsc 1.95 bsc 0.80 C 0.90 1.00 max 0.01 C 0.10 0.20 bsc 0.30 C 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 v in shdn v out int kill lt1761-1.8 r1 10k r8 1k r5 910k 2954 ta02 c4 0.1f p 1.8v 9v battery pb en int kill ltc2954-1 gnd ont pdt c ont * 0.033f v in c pdt * 1f *optional +

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