View LTC2955-15_8347503.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

ltc2955 1 2955f lt3008-3.3 v out v in pb on int kill pgd v in sel ltc2955ddb-1 2955 ta01a gnd tmr en 3.3v 1m r7 1m 2.32m shdn 0.1f 8.4v v trip = 5.4v p power-fail 402k typical application features description pushbutton on/off controller with automatic turn-on the ltc ? 2955 is a micropower, pushbutton on/off control- ler that manages system power by generating a clean enable output from the supply monitor input and the debounced pushbutton input. it features an interrupt output that notifies the system of a pushbutton or low supply event. when the system is ready, it may use the power kill input to shut off power. if the pushbutton remains pressed for more than the configurable turn-off duration, the system power is forced off. the supply input covers a wide range from 1.5v to 36v. the robust pushbutton input handles wide voltage swings of 36v and esd strikes to 25kv (human body model) without latchup or damage. a low 1.2a supply current maximizes battery run time. separate versions are avail- able for positive or negative enable polarities. pushbutton on/off with interrupt applications n automatic turn-on via voltage monitor input n wide input supply range: 1.5v to 36v n low supply current: 1.2a n 25kv esd hbm on pb input n 36v wide input voltage for pb input n low leakage en output allows dc/dc converter control (ltc2955-1) n high voltage en output drives external p-channel mosfet (ltc2955-2) n simple interface allows graceful p shutdown n adjustable turn-off timer n 10-lead 3mm 2mm dfn and 8-lead thinsot? packages n desktop and notebook computers n gps devices n portable instruments n automotive electronics l , lt, ltc, ltm, linear technology and the linear logo are registered trademarks and thinsot and powerpath are trademarks of linear technology corporation. all other trademarks are the property of their respective owners. turn on pulse short pulse long pulse turns on stays on interrupt interrupt turns off pb 2955 ta01b en int automatic turn-on with power-fail indication
ltc2955 2 2955f pin configuration absolute maximum ratings v in ............................................................. C0.3v to 40v input voltages pb ........................................................... C40v to 40v on ......................................................... C0.3v to 40v sel ........................................................ C0.3v to 40v kill ......................................................... C0.3v to 6v output voltages en/ en .................................................... C0.3v to 40v int ........................................................... C0.3v to 6v pgd ......................................................... C0.3v to 6v tmr ...................................................... C0.3v to 2.7v (note 1) top view 11 ddb package 10-lead (3mm 2mm) plastic dfn int pgd *en/ en v in pb on kill tmr sel gnd 6 8 7 9 10 5 4 2 3 1 t jmax = 125c, ja = 55c/w exposed pad (pin 11) pcb gnd connection optional *pin 3 is en for ltc2955-1 and is en for ltc2955-2 1 2 3 4 8 7 6 5 top view ts8 package 8-lead plastic tsot-23 int en/ en * v in pb on kill tmr gnd t jmax = 125c, ja = 195c/w *pin 7 is en for ltc2955-1 and is en for ltc2955-2 order information operating temperature range ltc2955c ................................................ 0c to 70c ltc2955i ............................................. C40c to 85c storage temperature range .................. C65c to 150c lead temperature (soldering, 10 sec) tsot-23 package ............................................. 300c lead free finish tape and reel (mini) tape and reel part marking* package description temperature range ltc2955cddb-1#trmpbf ltc2955cddb-1#trpbf lgbj 10-lead (3mm 2mm) plastic dfn 0c to 70c ltc2955cddb-2#trmpbf ltc2955cddb-2#trpbf lgbm 10-lead (3mm 2mm) plastic dfn 0c to 70c ltc2955iddb-1#trmpbf ltc2955iddb-1#trpbf lgbj 10-lead (3mm 2mm) plastic dfn C40c to 85c ltc2955iddb-2#trmpbf ltc2955iddb-2#trpbf lgbm 10-lead (3mm 2mm) plastic dfn C40c to 85c ltc2955cts8-1#trmpbf ltc2955cts8-1#trpbf ltgbk 8-lead plastic tsot-23 0c to 70c ltc2955cts8-2#trmpbf ltc2955cts8-2#trpbf ltgbn 8-lead plastic tsot-23 0c to 70c ltc2955its8-1#trmpbf ltc2955its8-1#trpbf ltgbk 8-lead plastic tsot-23 C40c to 85c ltc2955its8-2#trmpbf ltc2955its8-2#trpbf ltgbn 8-lead plastic tsot-23 C40c to 85c trm = 500 pieces. *temperature grades are identified by a label on the shipping container. consult ltc marketing for parts specified with wider operating temperature ranges. consult ltc marketing for information on lead based finish parts. 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/
ltc2955 3 2955f electrical characteristics symbol parameter conditions min typ max units supply v in supply voltage range l 1.5 36 v i in v in supply current l 0.5 1.2 3 a v uvl v in undervoltage lockout v in rising l 1.0 1.15 1.3 v v uvl(hyst) v in undervoltage lockout hysteresis l 30 85 200 mv input pins v pb(min(max)) pb voltage range l C36 36 v v pb pb input threshold pb falling l 0.6 0.8 1 v v pb(hyst) pb input threshold hysteresis (note 3) 40 mv v pb(voc) pb open circuit voltage i = C1a l 3.0 4.3 5.5 v i pb pb input leakage current 6v < pb < 36v pb = 1v pb = C36v l l l C1 C4 10 C8 C400 a a a v on on threshold on rising l 0.76 0.80 0.84 v v on(hyst) on hysteresis dfn package only 40 mv i on on input leakage current on = 1v on = 36v l l 10 100 na na v kill kill input threshold voltage kill falling l 0.76 0.80 0.84 v v kill(hyst) kill input threshold hysteresis (note 3) 30 mv i kill kill input leakage current kill = 1v l 50 na v sel sel input threshold l 0.4 0.8 1.2 v i sel sel input current sel = 1v sel = 36v l l 50 100 na na output pins v en/ en (vol) en/ en voltage output low i = 1ma l 0.175 0.4 v v en(voh) en voltage output high (ltc2955-1) i = 0a, C0.5a l 1.5 5.5 v v en (voh) en voltage output high (ltc2955-2) i = 0a, C0.5a l v in C 1.5 v i en en pull-up current (ltc2955-1) en = 0v l C1.2 C2 C2.8 a i en en pull-up resistance (ltc2955-2) l 0.45 0.9 1.35 m v int(vol) int voltage output low i = 3ma l 0.4 v i int int leakage current int = 5v l 50 na v pgd(voh) pgd voltage output high i = 0a, C0.5a l 1.5 5.5 v v pgd(vol) pgd voltage output low i = 3ma l 0.4 v i pgd pgd pull-up current pgd = 0v l C1.2 C2 C2.8 a i tmr(pu) tmr pull-up current tmr = 0v l C2 C3 C4 a i tmr(pd) tmr pull-down current tmr = 1.5v l 234a the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. v in = 7v unless otherwise noted. (note 2)
ltc2955 4 2955f symbol parameter conditions min typ max units timing t db(on) pb , on turn-on debounce time pb , on falling enable asserted l 19 32 45 ms t db(off) pb interrupt debounce time pb falling int falling l 19 32 45 ms t tmr additional turn-off debounce time c tmr = 2200pf l 5.8 11.5 17.2 ms t int(min) minimum int pulse width int falling tmr rising l 19 32 45 ms t on(pd) on interrupt delay on falling int falling, v sel > 0.8v l 200 s t pgd(pd) pgd propagation delay on falling pgd falling l 200 s t kill(pd) kill propagation delay kill falling enable released l 60 s t kill(pw) kill minimum pulse width l 60 s t kill(on blank) kill turn-on blanking (note 4) kill low, enable asserted enable released l 304 512 720 ms t en(lock out) en/ en lockout time (note 5) enable released enable asserted l 0.6 1 1.4 s electrical characteristics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. v in = 7v unless otherwise noted. (note 2) note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: all currents into pins are positive; all voltages are referenced to gnd unless otherwise noted. note 3: guaranteed by design, not subject to test. note 4: the kill turn-on blanking time is the waiting period immediately after the enable output is asserted. this blanking time allows sufficient time for the regulator and the p to perform power-up tasks. the kill , pb , and on inputs are ignored during this period. note 5: the enable lockout time is the waiting period immediately after the enable output is released. it allows an application to properly power-down such that the next power-up sequence starts from a consistent powered down configuration. pb and on are ignored during this period. typical performance characteristics supply current vs temperature supply current vs supply voltage undervoltage lockout vs temperature v in = 7v, t a = 25c, unless otherwise noted. temperature (c) C50 v uvl (v) 1.10 1.12 1.14 1.20 1.16 0 50 75 2955 g03 1.18 C25 25 100 125 temperature (c) C50 i vin (a) 0.8 1.0 1.1 1.2 1.6 1.3 0 50 75 2955 g01 0.9 1.4 1.5 C25 25 100 125 v in (v) 0 i vin (a) 0.6 0.8 1.0 1.2 10 20 25 2955 g02 1.4 1.6 5 15 30 40 35 t a = C40c t a = 25c t a = 85c
ltc2955 5 2955f typical performance characteristics tmr pull-up current vs temperature en output high voltage vs temperature en output high voltage vs supply voltage en/ en output low voltage vs temperature pb input current vs pb voltage pb voltage vs external pb resistance to ground on/ kill threshold vs temperature turn-on debounce time vs temperature additional turn-off debounce time vs tmr external capacitance v in = 7v, t a = 25c, unless otherwise noted. temperature (c) C50 t db(on) (ms) 30 32 31 36 33 0 50 75 2955 g05 35 34 C25 25 100 125 external pb resistance to ground (k) 0 pb oltae t a t a t a teperature on kill (v) 0.790 0.795 0.810 0.800 0 50 75 2955 g04 0.805 C25 25 100 125 temperature (c) C50 v en(voh) (v) 3.6 4.0 4.2 4.4 5.0 4.6 0 50 75 2955 g08 3.8 4.8 C25 25 100 125 tmr external capacitance (nf) 1 1 t tmr (ms) 100 10000 10 100 1000 2955 g06 10 1000 temperature (c) C50 i tmr(pu) (a) C2.6 C2.8 C2.9 C3.0 C3.4 C3.1 0 50 75 2955 g07 C2.7 C3.2 C3.3 C25 25 100 125 v in (v) 1 v en(voh) (v) 0.0 1.0 5.0 2.0 35 2955 g09 4.0 3.0 2 4 7 6 t a = C40c t a = 25c t a = 85c pb voltage (v) C40 i pb (a) 40 C40 C80 C200 C120 0 2955 g11 0 C160 C20 20 40 temperature (c) C50 v en/ en (vol) (mv) 50 200 150 250 300 450 350 0 50 75 2955 g10 100 400 C25 25 100 125 v in = 1.5v v in = 7v i = 1ma
ltc2955 6 2955f pin functions en: e n a b l e o u t p u t ( lt c 2 9 5 5 -1). e n i s a n a c t i v e h i g h o u t p u t to control the turn-on/off of the system power. connect this pin to the run or shutdown pin of the voltage regulator. the ltc2955 asserts en high when the pushbutton is pressed or when on goes high. the output high voltage follows the internal ldo output which provides sufficient margin for most shutdown pin thresholds. en : inverted enable output (ltc2955-2). en is an active low output to control the turn-on/off of the system power. it may drive a voltage regulators active low enable input, or it may drive the gate of a p-channel mosfet. in the turn-off state, the ltc2955 pulls this pin to v in through an internal 900k resistor. the ltc2955 pulls en to gnd when the pushbutton is pressed or when on goes high. exposed pad (dfn only): exposed pad. leave open or connect to device ground. gnd : device ground. int : open drain interrupt output. connect this pin to the interrupt input of the system with a pull-up resistor to the system supply. the ltc2955 asserts the int pin low when it receives the turn-off command from the pushbutton or the on pin. the minimum pulse width of the int signal is 32ms and can be extended through the tmr pin. kill : kill input. a low at kill releases the enable output (en/ en ). this pin can be driven by the microprocessor or it can be used as a voltage monitor input. tie to the system power supply or an external voltage of 1.2v~5v if unused. on: monitor input. connect this pin to an external resistive divider from the monitored voltage. this allows automatic system turn-on when the monitored voltage transitions high. for the dfn part, if the sel pin is tied high, it also allows automatic system turn-off when the monitored voltage transitions low. tie to gnd if unused. pb : pushbutton input. this is an active low input with a 900k pull-up to an internal ldo. connect one terminal of the pushbutton to this pin and connect the other terminal of the pushbutton to gnd. the pin may be left open if unused. pgd (dfn only): on status output. a high on this pin indicates that the voltage at the on pin is above the input threshold of 0.8v. this pin can be used as a system input to inform the system whether the turn-on was triggered by the on pin or the pushbutton pin. leave open if unused. sel (dfn only): mode select input. connect sel to gnd to block the on pin falling edge from activating system turn-off. connect sel to v in to allow both the on pin rising and falling edges to activate system turn-on and turn-off respectively. for the tsot package, sel is internally tied to gnd. do not leave open. tmr: timer pin. a capacitor to ground determines the additional time (5.2 seconds/f) beyond the default 64ms that the pushbutton must be held low before immediately releasing the en/ en and int o u t p u t s . t h e t u r n - o f f d e b o u n c e time defaults to 6 4ms if this pin is lef t open. to disable the ability to force a system power-down with a pushbutton press, ground the tmr pin. v in : power supply input. for > 20v applications, connect v in to the power source through a 1k resistor and bypass v in to gnd with a 10nf low esr capacitor.
ltc2955 7 2955f block diagram 2955 bd v in pb on on off *dfn only tmr sel* gnd v ldo regulator v ldo 5.2v v ldo 2a en control 900k 0.8v 0.8v 0.8v 0.8v kill int pgd* C + C + C + C + oscillator f = 1khz oscillator debounce logic 2a (2955-1) en en control ltc2955-1 v in (2955-2) en en control ltc2955-2 900k v ldo
ltc2955 8 2955f figure 1. pushbutton turn-on timing operation overview the ltc2955 is a pushbutton on/off controller that man- ages system power based on a pushbutton input ( pb pin) and a voltage monitor input (on pin). in a typical application, the enable output (en/ en ) turns on system power when the pushbutton is pressed or the supply monitor detects the presence of a primary or secondary supply such as a wall adaptor or car battery. after the system is powered up, a pushbutton event as- serts the interrupt output ( int ) which can be used in menu driven applications to request for a system power-down. a power kill input ( kill ) allows a microprocessor or sys- tem to release the enable output immediately, effectively powering down the system. system power is also forced off if the pushbutton remains asserted for more than the forced turn-off activation time configurable via the tmr pin. the ltc2955 is also designed with a blanking time after each system turn on and off event. during this blanking time, the ltc2955 ignores the kill , on and pb pins, thus ensuring that the system stays on/off for a minimum amount of time. this provides sufficient time for the voltage regulator to turn on/off and allows it to charge/discharge its output to the final voltage. it also allows the p suf- ficient time to perform power on/off tasks. the pgd output indicates the status of the on pin to allow the system to differentiate between pushbutton turn-on or supply plug-in events. turn-on sequence and kill blanking time the ltc2955-1 asserts the en output high if the pushbut- ton is pressed or the on pin goes high. this is typically used to turn on a dc/dc converter or linear regulator. figure 1 shows the turn-on sequence of the ltc2955-1 initiated by the pb pin. when the but ton is pressed at time t 1 , a high to low transition on the pb pin initiates the turn- on sequence. the pb pin must stay low continuously for a period of 32ms (t db(on) ) before the ltc2955-1 asserts the en output high. once en goes high (t 2 ), an internal 512ms blanking time (t kill (onblank) ) is started. during this blanking time, the ltc2955-1 ignores the kill , on and pb pins and keeps en high for at least 512ms. this provides sufficient time for the voltage regulator to turn on and charge its output to the final voltage and allows the p enough time to perform power on tasks. the p must pull the kill pin high during this 512ms blanking time, or else en will go low at the end of this time (t 3 ). t db(on) t kill(on blank) pb and kill ignored pb 2955 f01 en (ltc2955-1) t 1 t 2 t 3
ltc2955 9 2955f figure 2.on pin turn-on timing figure 3. pushbutton turn-off timing operation at the end of this blanking time, the ltc2955-1 will check that the pb pin is high. if the pb pin remains low, it will be ignored until a high is detected on the pin. the next low on the pb pin will initiate a turn-off sequence. figure 2 shows a similar ltc2955-1 turn-on sequence with the on pin going high. the timing sequence is very similar to that initiated by the pushbutton. the pgd output follows the on pin. pb pin turn-off sequence figure 3 shows the turn-off sequence of the ltc2955-1 initiated through the pb pin. a turn-off sequence refers to the ltc2955-1 releasing the en output. this turns off the voltage regulator. a high to low transition on pb (t 1 ) starts the turn-off sequence. in order to assert int (interrupt output) low, pb must stay low continuously for 32ms (t db(off) ). at the end of the 32ms (t 2 ), the int pin is asserted low and will stay low for at least 32ms (t int(min) ), even if the pb pin goes high during this period (t 2 to t 4 ). when the p receives this interrupt signal, it should start to perform its power-down functions and assert kill low (t 3 ) once it is done. the ltc2955-1 will then release int and pull en low, thus turning off the system power, as shown with dotted lines in figure 3. the user can also force the system to power-down if the p fails to respond to the interrupt signal ( kill pin remains 16 cycles kill tmr t db(off) pb ignored pb ignored pb t en(lockout) t tmr t int(min) int en (ltc2955-1) 2955 f03 t 1 t 2 t 3 t 4 t 5 t 6 t 7 ignored t db(on) t kill(on blank) on and kill ignored on t 1 t 2 t 3 2955 f02 en (ltc2955-1) pgd
ltc2955 10 2955f operation operation the pb and on inputs are ignored. this is to allow time for the voltage regulator to turn off and for its output to decay to 0v. this ensures that the p has completely powered down before it is allowed to restart. after the one second lockout time, the ltc2955-1 proceeds to the next stage to wait for a turn-on command and the cycle will repeat as above. if the pb pin remains low after the en output goes low, the ltc2955-1 will delay the start of this lockout time until the pb pin goes high. if the pb pin goes high when the external timer is still counting, as shown in figure 4, the turn-off sequence will be aborted. the int pin is forced high immediately and the en pin remains high. high). this can be done by holding the pushbutton down for a long period (> t db(off) + t int(min) + t tmr ) as shown with the solid lines in figure 3. if the pb pin remains low at the end of the 32ms minimum int pulse width (t int(min) ), the external timer will start counting (t 4 ). the capacitance at the tmr pin determines the duration of this timer and it will count for 16 cycles (t tmr ). if the pb pin remains low at the end of the 16 cycles (t 5 ), the ltc2955-1 will force the en pin low and the int pin high. see applications information for adjusting t tmr . after the en output goes low and the pb pin goes high, the ltc2955-1 starts the one second lockout time (t en(lockout) ). during this lockout time (t 6 to t 7 i n f i g u r e 3) figure 4. pushbutton turn-off aborted t db(off) pb ignored t < t tmr pb tmr t int(min) 2955 f04 int
ltc2955 11 2955f on pin turn-off sequence (dfn package only) figure 5 shows the turn-off sequence of the ltc2955-1 initiated by the on pin. the timing sequence is slightly different from that by the pushbutton as there is no de- bounce time (t db(off) ) before the int pin pulls low. the on pin falling edge can start the turn-off sequence only if the following two conditions are met: (1) the preceding turn-on sequence was initiated by the on pin rising edge, and (2) the sel pin must be tied high (>0.8v). for ts8 package, the on pin falling edge is ignored. in figure 5, a high to low transition at on (t 1 ) starts the turn-off sequence. the interrupt output ( int ) is asserted immediately when the on pin goes low. unlike the pb pin turn-off sequence, there is no 32ms debounce time (t db(ff) ) for the on pin going low. this allows the system to initiate a shutdown as soon as the monitored supply is removed and allows the p the maximum amount of time to perform power-down functions. the int pin will stay low for at least 32ms (t int(min) ). when the p receives this interrupt signal, it should start to perform its power- down functions and assert the kill input low (t 2 ) once it is done. the ltc2955-1 will then release the en and int outputs, thus turning off the system power, as shown with dotted lines in figure 5. if the p fails to respond ( kill pin remains high, as shown with solid line in figure 5) and the on pin remains low 32ms after int goes low, the external timer will start counting for 16 cycles (t tmr , t 3 to t 4 ). if the on pin remains low at the end of the 16 cycles (t 4 ), the ltc2955-1 will force the en pin low and the int pin high. see applications information for adjusting t tmr . after the en output goes low, the ltc2955-1 starts the one second lockout time (t en(lockout) ). d u r i n g t h i s l o c k o u t time (t 4 to t 5 ), the pb and on inputs are ignored. operation figure 5. on pin turn-off timing (dfn only, v sel > 1.2v and the preceding turn-on sequence was initiated by the on pin rising edge 16 cycles on t 1 t 2 t 5 t 4 t 3 tmr t int(min) t tmr t en(lockout) int pgd en (ltc2955-1) 2955 f05 kill ignored ignored
ltc2955 12 2955f operation pb vs on pin with the dfn package, if the turn-on sequence is initi- ated by the pushbutton, the on input is ignored until the pushbutton is pressed again to initiate a turn-off sequence. a s s h o w n i n f i g u r e 6 , t h e pb pin initiates a turn-on sequence at time t 1 before the on pin goes high at time t 2 . once en goes high (t 3 ), the on input is ignored, so a falling edge at the on pin (t 4 ) will not initiate a turn-off sequence even if the sel pin is high. this allows the system to remain powered up if it is plugged in and out of a secondary power source while the system is already turned on. if the turn-on sequence is initiated by the on pin, both the pushbutton and the on pin falling edge can initiate the turn-off sequence. for the ts8 package, on pin falling edge is always ignored regardless of which pins initiate the turn-on. the pb pin has priority over the on pin, so if the pb pin goes low and on pin goes high at the same time, the ltc2955-1 will monitor the pb pin for the 32ms debounce time and ignore the on pin unless the pb pin bounces during the 32ms. on pin initial turn-on if the ltc2955-1 powers up with the on pin already high, the en pin will go high after a power-up delay of about one second. subsequently, if the pushbutton is pressed to force en low, the ltc2955-1 will not initiate another turn-on even if the on pin remains high. the ltc2955-1 needs a rising edge at the on pin to initiate the subsequent turn-on. figure 6. pushbutton is pressed before the on pin goes high turn-on by pb pb pin pgd pin on pin on going low is ignored, since the en is asserted by the pushbutton on pin is ignored, since pushbutton is pressed first en pin 2955 f06 t 1 t 2 t 3 t 4 t 5
ltc2955 13 2955f operation as shown in figure 7, if the on pin is high when power is first applied to the ltc2955-1 at time t 1 , the en pin will go high (at t 2 ) after the one second en lockout time. at time t 3 , the pushbutton is pressed to activate turn-off while the on pin remains high. the ltc2955-1 will wait for a rising edge at the on pin or a low at the pb pin to activate the next turn-on. as shown at time t 4 , after the one second lockout time, the en stays low with on high. at time t 5 , only the rising edge of the on pin or a pb event will trigger the next turn-on again. ltc2955-1, ltc2955-2 versions the ltc2955-1 and ltc2955-2 differ only by the polarity of the high voltage (36v absolute maximum) enable pin. the ltc2955-1 en pin is a high true output designed to drive the shutdown pin of most voltage regulators. in turn-on mode, this pin is pulled high by a pull-up current of 2a powered by an internal ldo, which gives a high level output voltage (v oh ) of typically 4.3v. in turn-off mode, this pin is pulled low by an internal n-channel mosfet. if a higher v oh or higher pull-up current is required, connect the en pin to an external source through a pull-up resistor. the ltc2955-2 en pin is a low true enable output designed to drive the gate of an external p-channel mosfet. in turn-on mode, the en pin is pulled low by an internal n-channel mosfet. in turn-off mode, this pin is pulled high to v in through an internal 900k resistor. an external pull-up resistor can be connected between this pin and v in to increase the pull-up current. figure 7. power first applied to ltc2955-1 turn-on by on rising edge turn-off by pushbutton on pin pb pin v in a high at on pin is ignored after the first turn-on/off sequence on rising edge power first applied to ltc2955 v in pin en pin 2955 f07 t 1 t 2 t 3 t 4 t 5 turn-on by on high level t en(lockout) t en(lockout)
ltc2955 14 2955f applications information adjusting the forced turn-off timing the ltc2955 allows the user to force the system power to turn off if the p fails to respond during fault conditions. as shown by the solid lines in figure 3 and figure 5, when the p fails to bring the kill pin low after the interrupt signal is asserted, the user can force a turn-off by holding down the pushbutton. the length of time that pb must be held low is given by a fixed 64ms delay (t db(off) + t int(min) ) plus an adjustable power-down timer delay (t tmr ). the adjustable delay is set by placing an optional external capacitor on the tmr pin. use the following equation to calculate the capacitance for the desired delay. c tmr is the external capacitor at the tmr pin: c tmr = 0.19 ? t tmr [f/sec] as an example, if the required turn-off debounce time is one second: t tmr = (1000ms C 64ms) c tmr = 0.19 ? 0.936 required c tmr is 0.178f the on pin turn-off debounce time is 32ms less than the pb pin debounce time since there is no t db(off) . if the tmr pin is left open, the turn-off debounce time defaults to 64ms for the pb pin and 32ms for the on pin. voltage monitoring with kill input the kill pin can also be used as a voltage monitor input. figure 8 shows an application where the kill pin has a dual function. it is driven by a low leakage open drain output of the p. it is also connected to a resistive divider that monitors battery voltage (v in ). when the battery voltage falls below the set value, the voltage at the kill pin falls below 0.8v and the en pin is quickly pulled low. note that the resistor values should be as large as possible, but small enough to keep leakage currents from tripping the 0.8v kill comparator. operation without p if there is no circuitry available to drive the kill pin, this pin can be connected to a voltage regulator output through a resistive divider or rc network as shown in figure 9. the kill pin acts as a voltage monitor pin that shuts down the regulator when its output voltage drops below a certain level. the minimum pulse width needed to trigger kill is 30s. if there are glitches on the resistor pull-up voltage that are wider than 30s and transition below 0.8v, then an appropriate bypass capacitor should be connected to the kill pin. figure 8. input voltage monitoring with kill input figure 9. application without p *optional pb int kill v in ltc2955ts8-1 gnd tmr c tmr* 1f on en c4 0.1f v in = 9v 2955 f09 r1 10k v out v in v out lt3060 shdn c3* 0.01f + *optional pb int kill v in ltc2955ts8-1 gnd tmr c tmr* 1f on en c4 0.1f r3 583k 1% v in = 9v r2 100k 1% 2955 f08 p r1 10k kill (open drain) int v out v in v out lt3060 shdn
ltc2955 15 2955f v th = 0.8v input *optional 2955 f10 pb int kill v in ltc2955ts8-2 r4 100k 1% gnd tmr c tmr* 0.033f en v out v out ,trip point = 6v on c4 0.1f r1 649k 1% r9 100k m1 r5* 100k c3* 0.1f optional glitch filter capacitor 4.2v single cell li-ion battery + 4.2v single cell li-ion battery + high voltage powerpath? switching the high voltage en open drain output of the ltc2955-2 is designed to switch on/off an external power p-channel mosfet. this allows a user to connect/disconnect a power s u p p l y (o r b a t t e r y ) t o i t s l o a d b y t o g g l i n g t h e pb pin. figure 10 shows the ltc2955-2 controlling a two cell li-ion battery application. the kill pin is connected to the output of the external mosfet through a resistive divider. the kill pin serves as a voltage monitor. when v out drops below 6v, the en pin is pulled high (to v in ) after 15s later. r9 slows down the turning on of m1 so as to limit the inrush current when m1 turns on to charge up the capacitor at v out . r5 helps to speed up the turning off of m1 and also to keep m1 off when the input voltage rise time is fast. pb pin in a noisy environment the rugged pb pin is designed to operate in noisy environ- ments. transients below ground and above v in (C36v < v in < 36v) will not damage the rugged pb pin. additionally, the pb pin can withstand esd hbm strikes of up to 25kv. h ow e ver, i f t h e pu shbu t ton sw i t c h i s l o c a t e d ph y si c a ll y f ar from the ltc2955 pb pin, the parasitic capacitance and parasitic series inductance of the connecting cable or pcb trace can create problems. the parasitic capacitance can couple external noise onto the pb input; placing a 0.1f capacitor at the pin lessens the impact of this coupling. the parasitic series inductance may cause unpredictable ringing at the pb pin; placing a 5.1k resistor from the pb pin to the pushbutton switch reduces this ringing. figure 11 shows an example of this rc network at the pb pin. external pull-up resistor on pb pin an internal 900k pull-up resistor on the pb pin makes an external pull-up resistor unnecessary. leakage current on the pb board trace, however, will affect the open circuit voltage on the pb pin. if the leakage is too large (>1a), the pb voltage may fall close to the threshold window. to applications information figure 10. powerpath control with 6v undervoltage detect figure 11. noisy pb trace details omitted for clarity pb int kill v in ltc2955-1 gnd tmr en c5 0.1f r6 5.1k trace capacitance parasitics trace inductance noise v in 2955 f11
ltc2955 16 2955f mitigate the effect of the board leakage, a 10k resistor to v in is recommended (see figure 12). applications information enhancing v in ruggedness placing a 1k resistor and a 10nf capacitor at the v in pin can be used to enhance ruggedness in some applications. a 1k resistor in series with the v in pin allows the ltc2955 to withstand reverse-input voltages. the ltc2955s v in pin is internally clamped to one diode voltage below ground. in battery operated applications where a battery could be inserted improperly, this resistor will limit the current and allow internal clamping to protect the pin. figure 12. external pull-up resistor on pb pin figure 13. enhancing v in ruggedness figure 14. using a slide switch to prevent accidental turn-on/off figure 15. using a slide or toggle switch to turn-on/off adding a 10nf capacitor in addition to the 1k resistor can protect against high voltage input transients that would exceed the 40v absolute maximum voltage rating of the v in pin. these could occur during hot-plugging into a battery or ac adapter. this can also protect against tran- sients that may appear on the pcb ground during large esd strikes at the pb pin. the maximum operating current of the ltc2955 is less than 3a, creating an insignificant voltage drop across the resistor. using a capacitor value of 10nf provides sufficient filtering for most applications and larger values can actually diminish its effectiveness. applications with slide switch in some applications, to prevent accidental toggling of the system power, a slide switch is preferred over a pushbut- ton. figure 14 shows a slide switch added in series with the pushbutton. the user can slide the switch open to activate the hold/lock function, where the pushbutton is disabled. figure 15 shows a slide switch connected to the ltc2955 on pin resistive divider. if the user slides the switch to the on position, the ltc2955 on pin is high *optional pb int kill on v in ltc2955ts8-1 gnd tmr c ont* 0.033f en c4 10nf r8 1k 9v battery 2955 f13 p r1 10k kill int v in v out lt3060 shdn + pins omitted for clarity external board leakage current r7 10k if external parasitic board leakage >2a use external pull-up resistor pb v in v in 900k v ldo ltc2955-1/ ltc2955-2 gnd 0.8v >2a 2955 f12 normal hold/lock pb v in v in on sel ltc2955ddb-1 gnd en 2955 f14 pb v in v in sel on ltc2955ddb-1 gnd off on en 2955 f15
ltc2955 17 2955f applications information if a higher v en(voh) is required, an external pull-up resistor can be connected from the en pin to any higher voltage (<36v). the en pin is designed to be able to sink at least 1ma of current during turn-off, so this external pull-up resistor value must be selected to source less than 1ma with en at 0v. the ltc2955-1 en pin can also be connected to switching regulators with a run/ss pin. run/ss has a dual func- tion of a shutdown threshold and soft-start, with an internal soft-start pull-up current and an external soft-start capacitor. the ltc2955 en pin pull-up current of 2a will add to the soft-start pull-up current of the regulator. the and the device turns on. if the user slides the switch to the off position, the on pin voltage drops to 0v and the ltc2955 activates a turn-off since the sel pin is high (dfn package only). interface with switching regulators the ltc2955-1 en pin can be connected directly to most switching regulator shutdown inputs. the en pin high level output voltage (v en(voh) ) is typically 4.3v with v in >5v, and v en(voh) = v in C 0.5v if v in <5v. with a minimum v in of 1.5v, v en(voh) is still higher than most shutdown thresholds (usually <1.2v). figure 16 shows one such application. the regulator is a boost converter with a shutdown high threshold of 0.88v (maximum). figure 16. 2-cell with 3.3v output figure 17. turn-on/off a dc/dc regulator through the run/ss pin figure 18. recommended layout for the v in bypass capacitor ltc3528 v out fb v in pgood shdn v in pb int kill v in tmr ltc2955ts8-1 2955 f16 499k gnd on en v out 3.3v 0.4a 287k gnd sw 4.7f 1.5v to 3.2v 1m 22pf 22f 4.7h dc/dc v out run/ss v out gnd c ss c out v in v in pb int v in ltc2955ts8-1 2955 f17 p 1m gnd on en tmr kill c in soft-start capacitor may need to be increased to maintain the same soft-start time. the soft-start behavior of the regulator will remain the same. figure 17 shows the ltc2955-1 en pin connected to a dc/dc regulator run/ss pin. layout considerations figure 18 shows example pcb layouts for placing the v in pin bypass capacitor. position the bypass capacitor close to the ltc2955 on the same side of the pcb and keep the traces short. for the dfn package, a pcb via should be placed near the ltc2955 to connect the pb pin (pin 5) to the pushbutton. this allows an unbroken trace to be placed between the v in pin and the bypass capacitor. placing the bypass capacitor close to the ltc2955 gives the optimum protection against pb pin esd transients. 2955 f18 gnd c vin ltc2955ddb 11 6 8 7 9 10 5 4 2 3 1 v in v in 1 2 3 4 8 7 6 5 ltc2955ts8 gnd c vin
ltc2955 18 2955f typical applications low voltage pushbutton controller enables charge pump automatic power-up with pushbutton on/off powerpath control with immediate kill ltc3204-3.3 v out c + c C v in gnd pb int kill v in ltc2955ts8-1 2955 ta02 p 1m gnd on tmr en 2.2f 3.3v shdn 2.2f 1.8v lt1763-5 v out v in pb int kill pgd tmr v in on ltc2955ddb-1 2955 ta03 p 1m gnd sel en *optional rc network recommended to improve noise immunity shdn 1f 12v 0.1f* 5.1k* lt3009 v out v in pb kill int v in ltc2955ts8-2 2955 ta04 1m gnd on tmr en 3.3v 100k shdn 0.1f 12v
ltc2955 19 2955f 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 representa- t i o n t h a t t h e i n t e r c o n n e c t i o n o f i t s c i r c u i t s a s d e s c r i b e d h e r e i n w i l l n o t i n f r i n g e o n e x i s t i n g p a t e n t r i g h t s . package description ts8 package 8-lead plastic tsot-23 (reference ltc dwg # 05-08-1637 rev a) 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 ddb package 10-lead plastic dfn (3mm 2mm) (reference ltc dwg # 05-08-1722 rev ?) please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. 2.00 0.10 (2 sides) note: 1. drawing conforms to version (wecd-1) in jedec package outline m0-229 2. drawing not to scale 3. all dimensions are in millimeters 4. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.15mm on any side 5. exposed pad shall be solder plated 6. shaded area is only a reference for pin 1 location on the top and bottom of package 0.40 0.10 bottom viewexposed pad 0.64 0.05 (2 sides) 0.75 0.05 r = 0.115 typ r = 0.05 typ 2.39 0.05 (2 sides) 3.00 0.10 (2 sides) 1 5 10 6 pin 1 bar top mark (see note 6) 0.200 ref 0 C 0.05 (ddb10) dfn 0905 rev ? 0.25 0.05 2.39 0.05 (2 sides) recommended solder pad pitch and dimensions 0.64 0.05 (2 sides) 1.15 0.05 0.70 0.05 2.55 0.05 package outline 0.25 0.05 0.50 bsc pin 1 r = 0.20 or 0.25 45 chamfer 0.50 bsc
ltc2955 20 2955f linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2012 lt 0212 ? printed in usa related parts typical application part number description comments ltc2900 programmable quad supply monitor adjustable reset , 10-lead msop and 3mm 3mm dfn packages ltc2904/ltc2905 pin-programmable dual supply monitors adjustable reset and tolerance, 8-lead sot-23 and 3mm 2mm dfn packages ltc2909 precision triple/dual input uv, ov and negative voltage monitor 6.5v shunt regulator for high voltage operation ltc2910 octal positive/negative voltage monitor eight adjustable inputs (0.5v) ltc2914 quad uv/ov positive/negative voltage monitor adjustable uv and ov trip values ltc2950/ltc2951 pushbutton on/off controllers high voltage, low power pushbutton controllers with power-down fault detect kill timer ltc2952 pushbutton powerpath controller with supervisor automatic low loss switchover between dc sources ltc2953 pushbutton controller with voltage monitoring adjustable supply monitor with 200ms reset ltc2954 pushbutton on/off controller with p interrupt adjustable turn on/off timers ltc4411 2.6a low loss ideal diode in thinsot no external mosfet, automatic switching between dc sources ltc4412hv power path controller in thinsot efficient diode-oring, automatic switching between dc sources, 3v to 36v ltc4055 usb power controller and li-ion charger automatic switchover, charges 1-cell li-ion batteries ltc4352 ideal diode controller with monitoring controls n-channel mosfet, ov to 18v operation 9.6v threshold p-channel mosfet pb pgd int kill v in sel on tmr ltc2955ddb-1 2955 ta05 p 1m 2.21m 200k 33nf 12v 4.5v gnd en shdn lt3009-3.3 ltc4412 gate sense stat v in gnd ctl pushbutton on/off control with automatic turn-on when 12v applied

▲Up To Search▲

Price & Availability of LTC2955-15

	To Download LTC2955-15 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .