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LTC2951-1/ltc2951-2 1 295112fa en 2v/div pb 25ms/div 2951 ta01b 128ms push button on/off controller the ltc ? 2951 is a micropower, wide input voltage range push button on/off controller. the part contains a push button input which controls the toggling of an open drain enable output. the push button turn off debounce time is externally programmable, while the turn on debounce time is ? xed at 128ms. a simple microprocessor interface allows for proper system housekeeping prior to power down. under system fault conditions, an adjustable ? k ? i ? l ? l timeout delay ensures proper power down. the ltc2951 operates over a 2.7v to 26v input voltage range to accommodate a variety of input power supplies. very low quiescent current (6a typical) makes the ltc2951 ideally suited for battery powered applications. two versions of the part are available to accommodate either positive or negative enable polarities. the parts are available in 8-pin 3mm 2mm dfn and thinsot packages. portable instrumentation meters blade servers portable customer service pda desktop and notebook computers adjustable push button debounce and delay timers low supply current: 6a wide operating voltage range: 2.7v to 26v en output (LTC2951-1) allows dc/dc converter control ? e ? n output (ltc2951-2) allows circuit breaker control simple interface allows graceful p shut down high input voltage ? p ? b pin with internal pull up resistor 10kv esd hbm on ? p ? b input accurate 0.6v threshold on ? k ? i ? l ? l comparator input 8-pin 3mm 2mm dfn and thinsot tm packages v in shdn v in v out en int kill int kill LTC2951-1 killt offt dc/dc buck p/ c 3v ?26v *optional r1 10k 2951 ta01 c killt * 0.033 f c offt * 0.033 f pb gnd v in , lt, ltc and ltm are registered trademarks of linear technology corporation. thinsot is a trademark of linear technology corporation. all other trademarks are the property of their respective owners. applicatio s u features descriptio u typical applicatio u turn on debounce
LTC2951-1/ltc2951-2 2 295112fa supply voltage (v in ) ..................................C 0.3v to 33v input voltages ? p ? b ............................................................C 6v to 33v killt ....................................................C 0.3v to 2.7v offt .....................................................C 0.3v to 2.7v ? k ? i ? l ? l .........................................................C 0.3v to 7v output voltages ? i ? ? n ? t .........................................................C 0.3v to 10v en/ ? e ? n ....................................................C 0.3v to 10v (note 1) operating temperature range ltc2951c-1 .............................................. 0c to 70c ltc2951c-2 .............................................. 0c to 70c ltc2951i-1 .......................................... C 40c to 85c ltc2951i-2 .......................................... C 40c to 85c storage temperature range dfn package ..................................... C 65c to 125c tsot-23 ............................................ C 65c to 150c lead temperature (soldering, 10 sec) .................. 300c order part number ddb part* marking t jmax = 125c, ja = 165c/w exposed pad (pin 9) unconnected lbtb lbtd lbtb lbtd t jmax = 125c, ja = 140c/w order part number ts8 part* marking ltbtc ltbtf ltbtc ltbtf ltc2951cddb-1 ltc2951cddb-2 ltc2951iddb-1 ltc2951iddb-2 ltc2951cts8-1 ltc2951cts8-2 ltc2951its8-1 ltc2951its8-2 v in 1 pb 2 killt 3 gnd 4 8 kill 7 offt 6 en/en 5 int top view ts8 package 8-lead plastic tsot-23 top view ddb8 package 8-lead (3mm 2mm) plastic dfn 5 6 7 8 9 4 3 2 1 int en/en offt kill gnd killt pb v in the denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations 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 2.7 26.4 v i in v in supply current system power on, v in = 2.7v to 24v 6 12 a v uvl v in undervoltage lockout v in falling 2.2 2.3 2.4 v v uvl(hyst) v in undervoltage lockout hysteresis 50 300 600 mv absolute axi u rati gs w ww u package/order i for atio uu w electrical characteristics consult factory for parts speci? ed with wider operating temperature ranges. * the temperature grade is identi? ed by a label on the shipping container. order options tape and reel: add #tr lead free: add #pbf lead free tape and reel: add #trpbf lead free part marking: http://www.linear.com/leadfree/
LTC2951-1/ltc2951-2 3 295112fa the denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. v in = 2.7v to 26.4v, unless otherwise noted. (note 2) symbol parameter conditions min typ max units push button pin ( ? p ? b) v ? p ? b(min, max) ? p ? b voltage range single-ended C1 26.4 v i ? p ? b ? p ? b input current 2.5v < v ? p ? b < 26.4v v ? p ? b = 1v v ? p ? b = 0.6v C1 C3 C6 C9 1 C12 C15 a a a v ? p ? b(vth) ? p ? b input threshold ? p ? b falling 0.6 0.8 1 v v ? p ? b(voc) ? p ? b open circuit voltage i ? p ? b = C 1a 11.62 v timing pins (killt, offt) i killt, offt(pu) killt/offt pull up current v killt, offt = 0v C2.4 C3 C3.6 a i killt, offt(pd) killt/offt pull down current v killt, offt = 1.3v 2.4 3 3.6 a t db, on turn on debounce time ? p ? b falling enable asserted 100 128 163 ms t db, off internal turn off debounce time offt pin float, ? p ? b falling ? i ? n ? t falling 26 32 41 ms t offt additional adjustable turn off time c offt = 1500pf 9 11.5 13.5 ms p handshake pins ( ? i ? n ? t, ? k ? i ? l ? l) i ? i ? n ? t(lkg) ? i ? n ? t leakage current v ? ? ? i ? n ? t = 3v 1 a v ? i ? n ? t(vol) ? i ? n ? t output voltage low i ? ? ? i ? n ? t = 3ma 0.11 0.4 v v ? k ? i ? l ? l(th) ? k ? i ? l ? l input threshold voltage ? k ? i ? l ? l falling 0.57 0.6 0.63 v v ? k ? i ? l ? l(hyst) ? k ? i ? l ? l input threshold hysteresis 10 30 50 mv i ? k ? i ? l ? l(lkg) ? k ? i ? l ? l leakage current v ? k ? i ? l ? l = 0.6v 0.1 a t ? k ? i ? l ? l(pw) ? k ? i ? l ? l minimum pulse width 30 s t ? k ? i ? l ? l(pd) ? k ? i ? l ? l propagation delay ? k ? i ? l ? l falling enable released 30 s t ? k ? i ? l ? l, on blank ? k ? i ? l ? l turn on blanking (note 3) ? k ? i ? l ? l = low, enable asserted enable released 400 512 650 ms t ? k ? i ? l ? l, off delay internal ? k ? i ? l ? l turn off delay (note 4) killt pin float, ? k ? i ? l ? l = high, ? ? i ?? ? n ?? ? t asserted enable released 100 128 163 ms t ? k ? i ? l ? l, off delay, additional additional adjustable ? k ? i ? l ? l turn off delay (note 4) c killt = 1500pf 9 11.5 13.5 ms t en/ ? e ? n, lock out en/ ? e ? n lock out time (note 5) enable released enable asserted 200 256 325 ms i en/ ? e ? n(lkg) en/ ? e ? n leakage current v en/ ? e ? n = 1v, sink current off 0.1 a v en/ ? e ? n(vol) en/ ? e ? n voltage output low i en/ ? e ? n = 3ma 0.11 0.4 v 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 ? k ? i ? l ? l turn on blanking timer period is the waiting period immediately after the enable output is asserted. this blanking time allows suf? cient time for the dc/dc converter and the p to perform power up tasks. the ? k ? i ? l ? l and ? p ? b inputs are ignored during this period. if ? k ? i ? l ? l 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 . note 4: the internal ? k ? i ? l ? l turn off delay (t ? k ? i ? l ? l , off delay ) is the default delay from the initiation of a power off sequence ( ? i ? n ? t falling, ? k ? i ? l ? l = high), to the release of the enable output. the additional, adjustable ? k ? i ? l ? l turn off delay (t ? k ? i ? l ? l , off delay, additional ) uses an optional external capacitor (c killt ) to provide extra delay from ? i ? n ? t falling to the release of the enable output. if the ? k ? i ? l ? l input switches low at any time during ? k ? i ? l ? l turn off delay, enable is released, thus turning off system power. note 5: the enable lock out time is designed to allow an application to properly power down such that the next power up sequence starts from a consistent powered down con? guration. ? p ? b is ignored during this lock out time. this time delay does not include t db, on . electrical characteristics
LTC2951-1/ltc2951-2 4 295112fa typical perfor a ce characteristics uw temperature ( c) ?0 i vin ( a) 10 8 6 4 2 0 ?5 02550 2951 g01 75 100 0 5 10 15 20 25 30 temperature ( c) ?0 ?5 0 25 50 75 100 v in (v) i vin ( a) 10 8 6 4 2 0 2951 g02 2951 g03 killt pull-down current ( a) 1 t kill, off delay + t kill, off delay, additional (ms) 100 1000 1000 2951 g04 10 10 100 10000 2951 g05 v in (v) 0 t db, off (ms) 5101520 2951 g06 25 30 2951 g07 2951 g08 v in = 26.4v v in = 3.3v v in = 2.7v t a = 25 c v in (v) 0 0 t kill, off delay (ms) 40 80 120 160 200 5 10 15 20 25 30 t a = 25 c killt external capacitor (nf) 1 t db, off + t offt (ms) 100 1000 1000 10 10 100 10000 t a = 25 c v in = 3.3v offt external capacitor (nf) ?.4 ?.2 ?.0 ?.8 ?.6 v in = 26.4v v in = 2.7v temperature ( c) ?0 ?5 0 25 50 75 100 offt pull-down current ( a) ?.4 ?.2 ?.0 ?.8 ?.6 v in = 26.4v v in = 2.7v 50 40 30 20 10 0 t a = 25 c 2951 g14 v in (v) 0 0 t db, on (ms) 40 80 120 160 200 5 10 15 20 25 30 t a = 25 c supply current vs temperature ? k ? i ? l ? l turn off delay vs killt external capacitor supply current vs supply voltage killt pull-down current vs temperature internal default turn off debounce time (t db, off ) vs v in turn off debounce time (t db, off + t offt ) vs offt external capacitor offt pull-down current vs temperature internal default ? k ? i ? l ? l turn off delay (t ? k ? i ? l ? l, off delay ) vs v in turn on debounce time (t db, on ) vs v in
LTC2951-1/ltc2951-2 5 295112fa en (v) pb current ( a) 2951 g09 2951 g10 en/en current load (ma) 0 en/en voltage (mv) 500 400 300 200 100 0 8 2951 g11 2 4 6 10 2951 g13 v in (v) 10010 20 30 ? 5 15 25 ?50 ?00 ?50 ?00 ?0 0 pb voltage (v) t a = 25 c v in = 3.3v 0 0 50 100 150 200 250 300 5101520 v in = 3.3v t a = 25 c pb voltage (mv) external pb resistance to ground (k ? ) t a = ?5 c t a = 100 c t a = 25 c v in = 3.3v 04 1 2 3 4 3 2 1 0 t a = 25 c 100k pull-up from en to v in v in (v) 0 en (v) 4 2951 g12 1 2 3 t a = 25 c 100k pull-up from en to v in 1.0 0.8 0.6 0.4 0.2 0 typical perfor a ce characteristics uw ? p ? b current vs ? p ? b voltage ? p ? b voltage vs external ? p ? b resistance to ground en/ ? e ? n v ol vs current load ? e ? n (ltc2951-2) voltage vs v in en (LTC2951-1) voltage vs v in
LTC2951-1/ltc2951-2 6 295112fa v in (pin 1/pin 4): power supply input: 2.7v to 26.4v. ? p ? b (pin 2/pin 3): push button input. connecting ? p ? b to ground through a momentary switch provides on/off control via the en/ ? e ? n pin. an internal 100k pull-up resis- tor connects to an internal 1.9v bias voltage. the rugged ? p ? b input can be pulled up to 26.4v externally without consuming extra current. killt (pin 3/pin 2): additional, adjustable ? k ? i ? l ? l turn off delay input (t ? k ? i ? l ? l, off delay, additional ). a capacitor to ground provides additional delay time (beyond the internal default 128ms, t ? k ? i ? l ? l, off delay ) from ? i ? n ? t falling to the automatic release of the enable output. the ? k ? i ? l ? l turn off delay feature ensures the release of the enable pin under system fault conditions, such as the p not responding to the ltc2951 interrupt signal ( ? i ? n ? t low). gnd (pin 4/pin 1): device ground. ? i ? n ? t (pin 5/pin 8): open drain interrupt output. after a push button turn-off event is detected (t db, off + t offt ), the ltc2951 interrupts the system (p) by bringing the ? i ? n ? t pin low. once the system ? nishes its power down and housekeeping tasks, it sets ? k ? i ? l ? l low, which in turn releases the enable output. if at the end of the power down timer period (t ? k ? i ? l ? l, off delay + t ? k ? i ? l ? l, off delay, ad- ditional ) ? k ? i ? l ? l is still high, the enable output is released immediately. ? i ? n ? t may optionally be tied to ? k ? i ? l ? l to release the enable output immediately after the turn-off event has been detected ( ? i ? n ? t low). en (LTC2951-1, pin 6/pin 7): open drain enable output. this pin is intended to enable system power. en goes high after a valid ? p ? b turn on event (t db, on ). en goes low if: a) ? k ? i ? l ? l is not driven high within 512ms of the initial valid ? p ? b power turn-on event, b) ? k ? i ? l ? l is driven low during normal operation, or c) a second valid ? p ? b event (power turn-off) is detected. the operating range for this pin is 0v to 10v. a 100k pull-up is recommended if not available in the dc/dc converter. ?? e ? n (ltc2951-2, pin 6/pin 7): open drain enable output. this pin is intended to enable system power. ? e ? n is asserted low after a valid ? p ? b turn-on event (t db, on ). ? e ? n releases high if: a) ? k ? i ? l ? l is not driven high within 512ms of the initial valid ? p ? b power turn-on event, b) ? k ? i ? l ? l is driven low during normal operation, or c) a second valid ? p ? b event (power turn-off) is detected. the operating range of this pin is 0v to 10v. a 100k pull-up is recommended if not available in the dc/dc converter. offt (pin 7/pin 6): additional adjustable turn off time input (t offt ). a capacitor to ground determines the ad- ditional time (beyond the internal default 32ms, t db, off ) that the ? p ? b pin must be held low before initiating a power down sequence ( ? i ? n ? t falling). floating this pin results in a default turn off debounce time of 32ms. ? k ? i ? l ? l (pin 8/pin 5): ? k ? i ? l ? l input. forcing ? k ? i ? l ? l low releases the enable output. during system turn on, this pin is blanked by a 512ms internal timer (t ? k ? i ? l ? l, on blank ) to allow the system to pull ? k ? i ? l ? l high. this pin has an accurate 0.6v threshold and can be used as a voltage monitor input. exposed pad (pin 9): exposed pad may be left open or connected to device ground. (tsot-23/dfn) pi fu ctio s uuu
LTC2951-1/ltc2951-2 7 295112fa ti i g diagra s w u w kill en/en t kill(pw) t kill(pd) 2951 td01 logic oscillator oscillator debounce 2.4v 2.4v 100k v in 2.7v to 26.4v pb gnd en/en kill int killt offt 0.8v 0.6v 2951 bd regulator block diagra w
LTC2951-1/ltc2951-2 8 295112fa ti i g diagra s w u w power on timing power off timing, ? k ? i ? l ? l > 0.6v t db, on pb pb & kill ignored en (LTC2951-1) en (ltc2951-2) t kill, on blank 2951 td02 t db, off t offt pb int offt pb ignored t kill, off delay 2951 td03 16 cycles 16 cycles t kill, off delay, additional en (LTC2951-1) killt en (ltc2951-2)
LTC2951-1/ltc2951-2 9 295112fa description the ltc2951 is a low power (6a), wide input voltage range (2.7v to 26.4v), push button on/off controller that can interface to a p and a power supply. the part incorporates all the ? exible timing needed to debounce the push button input ( ? p ? b). the ltc2951 also provides a simple interface ( ? i ? n ? t output, ? k ? i ? l ? l input) to allow a system to power on and power off in a controlled manner. the wide input voltage range allows a system designer to operate from single cell to multi-cell battery stacks. very low quiescent current makes the ltc2951 ideal for continuously monitoring the on/off push button of a handheld device. turn on when power is ? rst applied to the ltc2951, the part initial- izes the output pins. any dc/dc converters connected to the en/ ? e ? n pin will therefore be off. to assert the enable output, ? p ? b must be held low for a minimum of 128ms (t db , on ). once the enable output is asserted, any dc/dc converters connected to this pin are turned on. the ? k ? i ? l ? l input from the p is ignored during the succeeding 512ms blanking time (t ? k ? i ? l ? l , on blank ). this blanking time represents the maximum time required to power up the dc/dc converter and the p. if ? k ? i ? l ? l is not brought high during this 512ms time window, the enable output is released. the assump- tion is that 512ms is suf? cient time for the system to power up. turn off to initiate a power off sequence, ? p ? b must be held low for a minimum of 32ms (t db , off ). additional turn off debounce time may be added via an optional capacitor connected to the offt pin (t offt ). the following equation describes the additional time that ? p ? b must be held low to initiate a power off sequence. c offt is the offt external capacitor: c offt = 1.56e-4 [ f/ms] ? (t offt C 1ms) once ? p ? b has been validly pressed, ? i ? n ? t is switched low. this alerts the p to perform its power down and house- keeping tasks. ? k ? i ? l ? l turn off delay the ltc2951 provides a failsafe feature that allows the user to turn off system power (via ? p ? b) under system fault conditions. during a normal power down sequence, the ltc2951 ? rst interrupts the p by setting ? i ? n ? t low. the p then performs power down and housekeeping tasks and drives ? k ? i ? l ? l low when done. the ltc2951 releases the enable output, thus turning off system power. the ? k ? i ? l ? l turn off timer starts when ? i ? n ? t is driven low. if the p fails to respond during this timeout period, the enable output will automatically release. the default power down timeout period is 128ms (t ? k ? i ? l ? l , off delay ), which can be extended by placing an optional capacitor on the killt pin (t ? k ? i ? l ? l , off delay, additional ). the following equation describes the additional power down timeout period. c killt is the killt external capacitor: c killt = 1.56e-4 [f/ms] ? (t ? k ? i ? l ? l , off delay, additional C 1ms) note that ? k ? i ? l ? l can be driven low (thereby releasing the enable output) at any time after t ? k ? i ? l ? l , on blank period. simpli? ed power on/off sequence figure 1 shows a simpli? ed LTC2951-1 power on and power off sequence. a high to low transition on ? p ? b (t 1 ) initiates the power on sequence. this diagram does not show any bounce on ? p ? b. in order to assert the enable output, the ? p ? b pin must stay low continuously ( ? p ? b high resets timers) for 128ms (t 2 Ct 1 ). once en goes high (t 2 ), an internal 512ms blanking timer is started. this blanking timer is designed to give suf? cient time for the dc/dc converter to reach its ? nal voltage, and to allow the p enough time to perform power on tasks. the ? k ? i ? l ? l pin must be pulled high within 512ms of the en pin going high. failure to do so results in the en pin going low 512ms after it went high. (en = low, see figure 2). note that the ltc2951 does not sample ? k ? i ? l ? l and ? p ? b until after the 512ms internal timer has expired. the reason ? p ? b 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 ? p ? b pin is then debounced with an internal 32ms timer. the system has now properly powered on and the ltc2951 monitors ? p ? b applicatio s i for atio wu u u
LTC2951-1/ltc2951-2 10 295112fa figure 1. simpli? ed power on/off sequence for LTC2951-1 figure 2. aborted power on sequence for LTC2951-1 t abort pb kill power on timing en 512ms internal timer t db, on power turned off 2951 f02 p failed to set kill high t 1 t 2 t db, on t 3 t 4 t 5 t 6 t 7 pb offt en kill int pb & kill ignored pb ignored 2951 f01 t kill, on blank t db, off t offt < t kill , off delay applicatio s i for atio wu u u
LTC2951-1/ltc2951-2 11 295112fa 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- ni? cant 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 ? p ? b) 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 ? k ? i ? l ? l releases enable, ? p ? b is ignored during the internal 256ms timer period. this is shown as t en/ ? e ? n, lockout in figure 4. LTC2951-1, ltc2951-2 versions the LTC2951-1 (high true en) and ltc2951-2 (low true ? e ? n) differ only by the polarity of the en/ ? e ? n pin. both ver- sions allow the user to extend the amount of time that the ? p ? b must be held low in order to begin a valid power off sequence. an external capacitor placed on the offt pin adds additional time to the turn off debounce time. if no capacitor is placed on the offt pin, then the turn off de- bounce time is given by an internally ? xed 32ms timer. both versions of the ltc2951 provide extendable ? k ? i ? l ? l turn off timer, t ? k ? i ? l ? l, off delay, additional , by connecting an optional external capacitor on the killt pin. the default ? k ? i ? l ? l turn off delay time is 128ms, t ? k ? i ? l ? l , off delay . figure 3. p turns off power (LTC2951-1) pb & kill ignored t kill pb en dc/dc turns off 2951 f03 kill xxx don? care p sets kill low pb & kill ignored pb pb ignored en kill pb blanking xxx don? care 256ms power on 2951 f04 dc/dc turns off p sets kill low t en/en, lockout figure 4. dc/dc turn off blanking (LTC2951-1) applicatio s i for atio wu u u and ? k ? i ? l ? l (for a turnoff command) while consuming only 6a of supply current. a high to low transition on ? p ? b (t 5 ) initiates the power off sequence. ? p ? b must stay low continuously ( ? p ? b high resets debounce timer) for a period controlled by the default 32ms and the external offt capacitor (t 6 Ct 5 ). at the completion of the offt timing (t 6 ), an interrupt ( ? i ? n ? t) is set, signifying that en will be switched low after the ? k ? i ? l ? l turn off (t ? k ? i ? l ? l , off delay + t ? k ? i ? l ? l , off delay, additional ) timeout period. once a system has ? nished performing its power down operations, it can set ? k ? i ? l ? l low (t 7 ) and thus immediately set en low, terminating the ? k ? i ? l ? l turn off timer. the release of the ? p ? b pin is then debounced with an internal 32ms timer. the system is now in its reset state: where the ltc2951 is in low power mode (6a). ? p ? b is monitored for a high to low transition. aborted power on sequence the power on sequence is aborted when the ? k ? i ? l ? l remains low after the end of the 512ms blanking time. figure 2 is a simpli? ed version of an aborted power on sequence. at time t abort , since ? k ? i ? l ? l 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 ? k ? i ? l ? l low, as shown in figure 3. at time t ? k ? i ? l ? l , ? k ? i ? l ? l is set low by the
LTC2951-1/ltc2951-2 12 295112fa high voltage pins the v in and ? p ? b pins can operate at voltages up to 26.4v. ? p ? b can, additionally, operate below ground (C 6v) without latching up the device. ? p ? b has an esd hbm rating of 10kv. if the push button switch connected to ? p ? b exhibits high leakage current, then an external pull-up resistor to v in is recommended. furthermore, if the push button switch is physically located far from the ltc2951 ? p ? b pin, parasitic capacitances may couple onto the high impedance ? p ? b input. additionally, parasitic series inductance may cause unpredictable ringing at the ? p ? b pin. placing a 5k resistor from the ? p ? b pin to the push button switch would mitigate parasitic inductance problems. placing a 0.1f capacitor on the ? p ? b pin would lessen the impact of parasitic capaci- tive coupling. voltage monitoring with ? k ? i ? l ? l input the ? k ? i ? l ? l pin can be used as a voltage monitor. figure 5 shows an application where the ? k ? i ? l ? l pin has a dual function. it is driven by a low leakage open drain output of the p. it is also connected to a resistor divider that monitors battery voltage (v in ). when the battery voltage falls below the set value, the voltage at the ? k ? i ? l ? l pin falls below 0.6v and the en pin is quickly pulled low. note that the resistor values should be as large as possible, but small enough to keep leakage currents from tripping the 0.6v ? k ? i ? l ? l comparator. the dc/dc converter shown has an internal pull-up cur- rent on its ? s ? h ? d ? n pin. a pull-up resistor on en is thus not needed. operation without p figure 6 shows how to connect the ? k ? i ? l ? l pin when there is no circuitry available to drive it. the minimum pulse 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 ? k ? i ? l ? l pin. figure 5. input voltage monitoring with ? k ? i ? l ? l input figure 6. no p application pb v in shdn v in v out en int kill int kill (open drain) LTC2951-1 gnd offt lt1767-3.3 p 9v r1 10k 3.3v 2951 f05 c4 0.1 f r3 806k 1% r2 100k 1% 5.4v threshold *optional v in c killt * 0.033 f c offt * 0.033 f killt v in shdn v in v out lt1767-3.3 9v 3.3v r1 100k c3* 0.01 f 2951 f06 + c4 0.1 f *optional pb en int kill LTC2951-1 gnd killt offt v in c killt * 0.033 f c offt * 0.033 f applicatio s i for atio wu u u typical applicatio s u
LTC2951-1/ltc2951-2 13 295112fa power path switching the ? e ? n open drain output of the ltc2951-2 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 ? p ? b pin. figure 7 shows the ltc2951-2 controlling a two cell li-ion battery application. the ? i ? n ? t and ? k ? i ? l ? l pins are connected to the output of the pfet through a resistor divider. the ? k ? i ? l ? l pin serves as a voltage monitor. when v out drops below 6v, the ? e ? n pin is open circuited 30s later. v out r1 909k 1% r4 100k 1% c3* 0.1 f 2951 f07 c4 0.1 f ceramic *optional open drain output v th = 0.6v input r5 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 ltc2951-2 gnd offt v in c killt * 0.033 f c offt * 0.033 f killt pb v in LTC2951-1 gnd r6 5k 2951 f08 trace capacitance parasitics c5 0.1 f details omitted for clarity trace inductance noise en int kill offt v in killt figure 7. power path control with 6v under voltage detect figure 8. filtering for noisy ? p ? b traces ? p ? b pin in a noisy environment the rugged ? p ? b pin is designed to operate in noisy envi- ronments. transients below ground (> C6v) and above v in (<33v) will not damage the rugged ? p ? b pin. additionally, the ? p ? b pin can withstand esd hbm strikes up to 10kv. in order to keep external noise from coupling inside the ltc2951, place an r-c network close to the ? p ? b pin. a 5k resistor and a 0.1f capacitor should suf? ce for most noisy applications (see figure 8). typical applicatio s u
LTC2951-1/ltc2951-2 14 295112fa external pull-up resistor on ? p ? b an internal pull-up resistor on the ? p ? b pin makes an ex- ternal pull-up resistor unnecessary. leakage current on the ? p ? b board trace, however, will affect the open circuit voltage on the ? p ? b pin. if the leakage is too large (>2a), the ? p ? b 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). pb v in LTC2951-1/ ltc2951-2 gnd external board leakage current 100k 2.4v r7 10k 2951 f09 >2 a pins omitted for clarity if external parasitic board leakage >2 a, use external pull-up resistor v in figure 9. external pull-up resistor on ? p ? b pin reverse battery protection to protect the ltc2951 from a reverse battery connec- tion, place a 1k resistor (r8) in series with the v in pin (see figure 10). typical applicatio s u
LTC2951-1/ltc2951-2 15 295112fa 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. ddb package 8-lead plastic dfn (3mm 2mm) (reference ltc dwg # 05-08-1702) ts8 package 8-lead plastic tsot-23 (reference ltc dwg # 05-08-1637) 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 1.50 ?1.75 (note 4) 2.80 bsc 0.22 ?0.36 8 plcs (note 3) datum ? 0.09 ?0.20 (note 3) ts8 tsot-23 0802 2.90 bsc (note 4) 0.65 bsc 1.95 bsc 0.80 ?0.90 1.00 max 0.01 ?0.10 0.20 bsc 0.30 ?0.50 ref pin one id note: 1. dimensions are in millimeters 2. drawing not to scale 3. dimensions are inclusive of plating 4. dimensions are exclusive of mold flash and metal burr 5. mold flash shall not exceed 0.254mm 6. jedec package reference is mo-193 3.85 max 0.52 max 0.65 ref recommended solder pad layout per ipc calculator 1.4 min 2.62 ref 1.22 ref package descriptio u
LTC2951-1/ltc2951-2 16 295112fa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2005 lt/lwi 0706 rev a ? printed in usa part number description comments ltc2900 programmable quad supply monitor adjustable ? r ? e ? s ? e ? t, 10-lead msop and 3mm x 3mm dfn packages ltc2904/2905 pin-programmable dual supply monitors adjustable ? r ? e ? s ? e ? t and tolerance, 8-lead sot-23 and 3mm 2mm dfn packages ltc2950 micropower push button on/off controller high voltage push button controller with p interface and adjustable on time ltc4411 2.6a low loss ideal diode in thinsot no external mosfet, automatic switching between dc sources ltc4412hv power path controller in thinsot ef? cient 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 v in shdn v out int kill lt1761-1.8 r1 10k r8 1k r5 910k 2951 f10 c4 0.1 f + p 1.8v 9v battery pb en int kill LTC2951-1 gnd killt offt c killt * 0.033 f v in c offt * 0.033 f *optional figure 10. reverse battery protection using r8 typical applicatio u related parts

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