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1 LTC1174 LTC1174-3.3/LTC1174-5 1174fe high efficiency step-down and inverting dc/dc converter high efficiency step-down converter LTC1174-5 efficiency high efficiency: up to 94% peak inductor current independent of inductor value short-circuit protection optimized for 5v to 5v applications wide v in range: 4v to 18.5v low dropout operation low-battery detector pin selectable current limit internal 0.9 ? power switch: v in = 9v only four external components required 130 a standby current active low micropower shutdown distributed power systems step-down converters inverting converters memory backup supply portable instruments battery-powered equipment the ltc 1174 is a simple current mode dc/dc converter ideally suited for 9v to 5v, 5v to 3.3v or 5v to 5v operation. with an internal 0.9 ? switch (at a supply voltage of 9v), the LTC1174 requires only four external components to construct a complete high efficiency dc/dc converter. under a no load condition the LTC1174 draws only 130 a. in shutdown, it draws a mere 1 a making this converter ideal for current sensitive applications. in dropout, the internal p-channel mosfet switch is turned on continu- ously allowing the user to maximize the life of the battery source. the maximum inductor current of the LTC1174 family is pin selectable to either 340ma or 600ma, optimizing efficiency for a wide range of applications. operation up to 200khz permits the use of small surface mount inductors and capacitors. for applications requiring higher output current or ultra- high efficiency, see the ltc1148 data sheet. features descriptio u applicatio s u typical applicatio u v in 9v 3 LTC1174-5 lb in lb out i pgm gnd v in shutdown v out sw 2 7 6 8 1 5 4 100 h ? 100 f** 10v 5v 175ma 15 f* 25v 3 1n5818 1174 ta01 * ** ? (3) avx tpsd156k025 avx tpsd107k010 coiltronics ctx100-4 + + load current (ma) 1 efficiency (%) 100 95 90 85 80 75 70 10 100 1174 ta02 200 v in = 6v v in = 9v l = 100 h v out = 5v i pgm = 0v , lt, ltc and ltm are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners.
2 LTC1174 LTC1174-3.3/LTC1174-5 1174fe (note 1) (voltage referred to gnd pin) input supply voltage (pin 6) LTC1174 ........................................... 0.3v to 13.5v LTC1174hv ...................................... 0.3v to 18.5v switch current (pin 5) .............................................. 1a switch voltage (pin 5) LTC1174 ................................................. v in ?13.5v LTC1174hv ............................................ v in ?18.5v operating temperature range LTC1174cx ............................................ 0 c to 70 c LTC1174ix ........................................ 40 c to 85 c junction temperature (note 2) ............................ 125 c storage temperature range ................ 65 c to 150 c lead temperature (soldering, 10 sec)................. 300 c order part number s8 part marking LTC1174cs8 LTC1174cs8-3.3 LTC1174cs8-5 LTC1174is8 LTC1174hvcs8 LTC1174hvcs8-3.3 LTC1174hvcs8-5 LTC1174hvis8 1174 117433 117450 1174i 1174h 1174h3 1174h5 1174hi t jmax = 125 c, ja = 150 c/w order part number LTC1174cn8 LTC1174cn8-3.3 LTC1174cn8-5 LTC1174in8 LTC1174hvcn8 LTC1174hvcn8-3.3 LTC1174hvcn8-5 t jmax = 125 c, ja = 110 c/w absolute axi u rati gs w ww u package/order i for atio uu w 1 2 3 4 8 7 6 5 top view v out (v fb *) lb out lb in gnd shutdown i pgm v in sw n8 package 8-lead pdip * adjustable output version 1 2 3 4 8 7 6 5 top view s8 package 8-lead plastic so * adjustable output version v out (v fb *) lb out lb in gnd shutdown i pgm v in sw order options tape and reel: add #tr lead free: add #pbf lead free tape and reel: add #trpbf lead free part marking: http://www.linear.com/leadfree/ consult ltc marketing for parts specified with wider operating temperature ranges. the denotes specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v in = 9v, v shutdown = v in , i pgm = 0v, unless otherwise noted. symbol parameter conditions min typ max units i fb feedback current LTC1174/LTC1174hv 1 a v fb feedback voltage LTC1174/LTC1174hv 1.20 1.25 1.30 v v out regulated output voltage LTC1174-3.3/LTC1174hv-3.3 3.14 3.30 3.46 v LTC1174-5/LTC1174v-5 4.75 5.00 5.25 v ? v out output voltage line regulation v in = 6v to 12v, i load = 100ma, i pgm = v in (note 3) 10 70 mv electrical characteristics
3 LTC1174 LTC1174-3.3/LTC1174-5 1174fe symbol parameter conditions min typ max units output voltage load regulation LTC1174-3.3 (note 3) 20ma < i load < 175ma, i pgm = 0v ? ?0 mv 20ma < i load < 400ma, i pgm = v in ?5 ?0 mv LTC1174-5 (note 3) 20ma < i load < 175ma, i pgm = 0v ? ?0 mv 20ma < i load < 400ma, i pgm = v in ?0 ?0 mv i q input dc supply current (note 4) active mode LTC1174: 4v < v in < 12v, i pgm = 0v 450 600 a LTC1174hv: 4v < v in < 16v, i pgm = 0v 450 600 a sleep mode LTC1174: 4v < v in < 12v 130 180 a LTC1174hv: 4v < v in < 16v 130 180 a shutdown (note 4) LTC1174: v shutdown = 0v, 4v < v in < 12v 1 10 a LTC1174hv: v shutdown = 0v, 4v < v in < 16v 2 25 a v lbtrip low-battery trip point 1.25 1.4 v i lbin current into pin 3 0.5 a i lbout current sunk by pin 2 LTC1174: v lbout = 0.4v 1.0 1.2 1.5 ma LTC1174hv: v lbout = 0.4v 0.6 0.8 1.5 ma v hyst comparator hysteresis LTC1174/LTC1174hv 7.5 15 30 mv i peak current limit i pgm = v in , v out = 0v 0.54 0.60 0.83 a i pgm = 0v, v out = 0v 0.27 0.34 0.53 a r on on resistance of switch LTC1174 0.75 1.30 ? LTC1174hv 0.90 1.55 ? t off switch off-time (note 6) v out at regulated value 3 4 5 s v ih shutdown pin high minimum voltage at pin 8 for device to be active 1.2 v v il shutdown pin low maximum voltage at pin 8 for device to be in shutdown 0.75 v i ih shutdown pin input current LTC1174: v shutdown = 12v 0.5 a LTC1174hv: v shutdown = 16v 2.0 a i il shutdown pin input current 0 v shutdown 0.8v 0.5 a the denotes specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v in = 9v, v shutdown = v in , i pgm = 0v, unless otherwise noted. electrical characteristics symbol parameter conditions min typ max units v fb feedback voltage LTC1174i/LTC1174hvi 1.18 1.25 1.31 v i lbout current sunk by pin 2 v lbout = 0.4v (LTC1174i) 0.75 1.2 2.0 ma v lbout = 0.4v (LTC1174hvi) 0.50 0.8 1.6 ma i peak current limit i pgm = v in , v out = 0v (LTC1174i) 0.54 0.60 0.84 a i pgm = 0v, v out = 0v (LTC1174i) 0.34 a i pgm = v in , v out = 0v (LTC1174hvi) 0.5 0.60 0.86 a i pgm = 0v, v out = 0v (LTC1174hvi) 0.34 a t off switch off-time (note 6) v out at regulated value (LTC1174i) 2.0 4 6.0 s v out at regulated value (LTC1174hvi) 1.8 4 6.2 s r on switch on resistance LTC1174i/LTC1174hvi 0.9 1.7 ? 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. the denotes specifications which apply over the full operating temperature range, otherwise specifications are at 40 c t a 85 c. LTC1174i and LTC1174hvi only. note 2: t j is calculated from the ambient temperature t a and power dissipation p d according to the following formulas: LTC1174cn8, LTC1174cn8-3.3, LTC1174cn8-5: t j = t a + (p d 110 c/w) LTC1174cs8, LTC1174cs8-3.3, LTC1174cs8-5: t j = t a + (p d 150 c/w)
4 LTC1174 LTC1174-3.3/LTC1174-5 1174fe efficiency vs load current efficiency vs load current efficiency vs load current efficiency vs load current efficiency vs load current efficiency vs load current typical perfor a ce characteristics uw load current (ma) 1 efficiency (%) 100 95 90 85 80 75 70 10 100 1174 g01 200 v in = 6v v in = 9v l = 50 h v out = 5v i pgm = 0v coil = ctx50-4 load current (ma) 1 efficiency (%) 10 100 1174 g02 400 100 95 90 85 80 75 70 l = 50 h v out = 5v i pgm = v in coil = ctx50-4 v in = 6v v in = 9v load current (ma) 1 efficiency (%) 10 100 1174 g03 500 100 95 90 85 80 75 70 l = 100 h v out = 5v i pgm = v in coil = ctx100-4 v in = 6v v in = 9v load current (ma) 1 efficiency (%) 10 100 1174 g04 300 100 90 80 70 60 50 l = 50 h v out = 3.3v i pgm = 0v coil = ctx50-4 v in = 5v v in = 9v load current (ma) 1 efficiency (%) 10 100 1174 g06 500 100 90 80 70 60 50 l = 100 h v out = 3.3v i pgm = v in coil = ctx100-4 v in = 5v v in = 9v load current (ma) 1 efficiency (%) 10 100 1174 g05 500 100 90 80 70 60 50 l = 50 h v out = 3.3v i pgm = v in coil = ctx50-4 v in = 5v v in = 9v note 3: guaranteed by design. note 4: dynamic supply current is higher due to the gate charge being delivered at the switching frequency. electrical characteristics note 5: current into pin 6 only, measured without electrolytic input capacitor. note 6: the off-time is wafer-sort trimmed.
5 LTC1174 LTC1174-3.3/LTC1174-5 1174fe supply current in shutdown switch resistance vs input voltage efficiency vs input voltage dc supply current operating frequency vs v in ?v out off-time vs output voltage typical perfor a ce characteristics uw input voltage (v) 5 efficiency (%) 7 9 10 14 1174 g10 68 11 12 13 95 94 93 92 91 90 89 v out = 5v l = 100 h coil = ctx100-4 i load = 300ma i pgm = v in i load = 100ma i pgm = 0v input voltage (v) 0 supply current ( a) 8 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 1174 g11 414 2 6 10 12 shutdown = 0v t a = 25 c current into pin 6 only input voltage (v) 0 supply current ( a) 500 450 400 350 300 250 200 150 100 50 0 4 8 10 1174 g12 2 6 12 14 active mode i pgm = v in sleep mode i pgm = 0v t a = 25 c (v in ?v out ) voltage (v) 0 normalized frequency 9 1174 g13 2 57 2.0 1.5 1.0 0.5 0 1 3 4 6 8 v out = 5v t a = 25 c t a = 70 c input voltage (v) 4 rds (on) ( ? ) 12 1174 g14 6 8 10 14 16 18 20 t a = 25 c 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 LTC1174hv LTC1174 output voltage (v) 0 off-time ( s) 50 40 30 20 10 0 4 1174 g15 1 2 3 5 LTC1174-5 LTC1174hv-5 LTC1174-3.3 LTC1174hv-3.3 line regulation switch leakage current vs temperature efficiency vs input voltage input voltage (v) 0 ? v out (mv) 6 4 2 0 ? ? ? ? ?0 ?2 ?4 4 8 10 1174 g07 2 6 12 14 i load = 100ma i pgm = 0v temperature ( c) 0 leakage current (na) 180 160 140 120 100 80 60 40 20 0 40 80 100 1174 g08 20 60 v in = 13.5v input voltage (v) 5 efficiency (%) 14 1174 g09 7 9 12 95 94 93 92 91 90 89 88 87 68 10 11 13 l = 100 h l = 50 h v out = 5v i pgm = 0v i load = 75ma core = ctx (kool m )
6 LTC1174 LTC1174-3.3/LTC1174-5 1174fe (pin 1 connection shown for LTC1174-3.3 and LTC1174-5, changes create LTC1174) fu ctio al diagra u u w + v th2 + + v lim2 v lim1 i pgm r sense 0.1 ? reset v th1 lb out 2 1174 bd g m v fb 1.25v reference q gnd 4 5 sw 1 v out (v fb ) 7 + a1 r1* 31.5k set 6 v in lb in 3 shutdown 8 c t sleep + a3 a4 a5 v fb * r1 = 51k for LTC1174-3.3 r1 = 93.5k for LTC1174-5 a2 sw (pin 5): drain of the p-channel mosfet switch. cathode of schottky diode must be closely connected to this pin. v in (pin 6): input supply voltage. it must be decoupled close to ground pin 4. i pgm (pin 7): selects the current limit of the p-channel switch. with i pgm = v in , the current trip point is 600ma and with i pgm = 0v, the current trip value is reduced to 340ma. shutdown (pin 8): pulling this pin to ground keeps the internal switch off and puts the LTC1174 in micropower shutdown. v out (v fb ) (pin 1): for the LTC1174, this pin connects to the main voltage comparator? input. on the LTC1174-3.3 and LTC1174-5 this pin goes to an internal resistive divider which sets the output voltage. lb out (pin 2): open drain of an n-channel pull-down. this pin will sink current when pin 3 (lb in ) goes below 1.25v. during shutdown the state of this pin is indeterminate. lb in (pin 3): the ?input of the low-battery voltage comparator. the ??input is connected to a reference voltage of 1.25v. gnd (pin 4): ground pin. uu u pi fu ctio s
7 LTC1174 LTC1174-3.3/LTC1174-5 1174fe (refer to functional diagram) the LTC1174 uses a constant off-time architecture to switch its internal p-channel power mosfet. the off-time is set by an internal timing capacitor and the operating frequency is a function of v in . the output voltage is set by an internal resistive divider (LTC1174-3.3 and LTC1174-5) or an external divider re- turned to v fb pin 1 (LTC1174). a voltage comparator a1 compares the divided output voltage to a reference voltage of 1.25v. to optimize efficiency, the LTC1174 automatically switches between continuous and burst mode operation. the volt- age comparator is the primary control element when the device is in burst mode operation, while the current com- parator controls the output voltage in continuous mode. during the switch?n?time, switch current flows through the 0.1 ? sense resistor. when this current reaches the threshold of the current comparator a2, its output signal will change state, setting the flip-flop and turning the switch off. the timing capacitor, c t , begins to discharge until its voltage goes below v th1 . comparator a4 will then trip, which resets the flip-flop and causes the switch to turn on again. also, the timing capacitor is recharged. the inductor current will again ramp up until the current comparator a2 trips. the cycle then repeats. when the load is relatively light, the LTC1174 automatically goes into burst mode operation. the current mode loop is interrupted when the output voltage reaches the desired regulated value. the hysteretic voltage comparator a1 trips when v out is above the desired output voltage, shutting off the switch and causing the timing capacitor to discharge. this capacitor discharges past v th1 until its voltage drops below v th2 . comparator a5 then trips and a sleep signal is generated. in sleep mode, the LTC1174 is in standby and the load current is supplied by the output capacitor. all unused circuitry is shut off, reducing quiescent current from 0.45ma to 0.13ma. when the output capacitor discharges by the amount of the hysteresis of the comparator a1, the p-channel switch turns on again and the process repeats itself. operating frequency and inductor since the LTC1174 utilizes a constant off-time architecture, its operating frequency is dependent on the value of v in . the frequency of operation can be expressed as: f t vv vv hz off in out in d = ? + ? ? ? ? ? ? () 1 where t off = 4 s and v d is the voltage drop across the diode. note that the operating frequency is a function of the input and ouput voltage. although the size of the inductor does not affect the fre- quency, it does affect the ripple current. the peak-to-peak ripple current is given by: i vv l a ripple out d pp = + ? ? ? ? ? ? () ? ? 410 6 by choosing a smaller inductor, a low esr output filter capacitor has to be used (see c in and c out ). moreover, core loss will also increase (see inductor core selection section) due to higher ripple current. operatio u burst mode is a registered trademark of linear technology corporation.
8 LTC1174 LTC1174-3.3/LTC1174-5 1174fe inductor core selection with the value of l selected, the type of inductor must be chosen. basically there are two kinds of losses in an inductor, core and copper core losses are dependent on the peak-to-peak ripple current and the core material. however it is independent of the physical size of the core. by increasing the inductance the inductor? peak-to-peak ripple current will decrease, therefore reducing core loss. utilizing low core loss mate- rial, such as molypermalloy or kool m will allow users to concentrate on reducing copper loss and preventing satu- ration. figure 1 shows the effect of different core material on the efficiency of the LTC1174. the ctx core is kool m and the ctxp core is powdered iron (material 52). although higher inductance reduces core loss, it increases copper loss as it requires more windings. when space is not figure 1. efficiency using different types of inductor core material applicatio s i for atio wu uu load current (ma) 1 efficiency (%) 10 100 500 100 90 80 70 60 50 v in = 5v v out = 3.3v i pgm = v in ctx50-4 ctx50-4p 1174 f01 load current (ma) 1 efficiency (%) 10 100 500 100 90 80 70 60 50 v in = 5v v out = 3.3v i pgm = v in ctx100-4 ctx100-4p a premium larger gauge wire can be used to reduce the wire resistance. this also prevents excessive heat dissipation. c in in continuous mode the source current of the p-channel mosfet is a square wave of duty cycle v out /v in . to prevent large voltage transients, a low esr input capacitor sized for the maximum rms current must be used. the c in rms current is given by: i ivvv v a rms out out in out in rms ? () [] () 12 / this formula has a maximum at v in = 2v out , where i rms = i out /2. this simple worst case is commonly used for design because even significant deviations do not offer much relief. note that ripple current directly affects capacitor? lifetime. do not underspecify this component. an additional 0.1 f ceramic capacitor is also required on v in for high frequency decoupling. c out to avoid overheating, the output capacitor must be sized to handle the ripple current generated by the inductor. the worst case rms ripple current in the output capacitor is given by: i i a ma rms peak rms () = 2 170 or 300ma although the output voltage ripple is determined by the hysteresis of the voltage comparator, esr of the output capacitor is also a concern. too high of an esr will create a higher ripple output voltage and at the same time cause the LTC1174 to sleep less often. this will affect the efficiency of the LTC1174. for a given technology, esr is a direct function of the volume of the capacitor. several small-sized capacitors can also be paralleled to obtain the same esr as one large can. manufacturers such as nichicon, chemicon and sprague should be considered for high performance capacitors. the os-con semiconductor dielectric capaci- tor available from sanyo has the lowest esr for its size, at a higher price.
9 LTC1174 LTC1174-3.3/LTC1174-5 1174fe catch diode selection the catch diode carries load current during the off-time. the average diode current is therefore dependent on the p-channel switch duty cycle. at high input voltages the diode conducts most of the time. as v in approaches v out the diode conducts only a small fraction of the time. the most stressful condition for the diode is when the output is short-circuited. under this condition the diode must safely handle i peak at close to 100% duty cycle. a fast switching diode must also be used to optimize efficiency. schottky diodes are a good choice for low forward drop and fast switching times. most LTC1174 circuits will be well served by either a 1n5818, a mbrs140t3 or a mbr0520l schottky diode. short-circuit protection the LTC1174 is protected from output short by its internal current limit. depending on the condition of i pgm pin, the limit is either set to 340ma or 600ma. in addition, the off- time of the switch is increased to allow the inductor? current to decay far enough to prevent any current build-up (see figure 2). applicatio s i for atio wu uu compared with a 1.25v reference voltage. with the current going into pin 3 being negligible, the following expression is used for setting the trip limit: v r r lbtrip =+ ? ? ? ? ? ? 125 1 4 3 . when the LTC1174 is shut down, the low-battery detector is inactive. i pgm = v in i pgm = 0 gnd l = 100 h v in = 13.5v 20 s/div 1174 f02 figure 2. inductor's current with output shorted low-battery detector the low-battery indicator senses the input voltage through an external resistive divider. this divided voltage connects to the ?input of a voltage comparator (pin 3) which is figure 3. low-battery comparator LTC1174 + 1.25v reference r4 r3 3 v in 1174 f03 LTC1174 adjustable/low noise applications the LTC1174 develops a 1.25v reference voltage between the feedback (pin 1) terminal and ground (see figure 4). by selecting resistor r1, a constant current is caused to flow through r1 and r2 to set the overall output voltage. the regulated output voltage is determined by: v r r out =+ ? ? ? ? ? ? 125 1 2 1 . for most applications, a 30k resistor is suggested for r1. to prevent stray pickup, a 100pf capacitor is suggested across r1 located close to the LTC1174. alternatively, a capacitor across r2 can be used to increase the switching frequency for low noise operation. inverting applications the LTC1174 can easily be set up for a negative output voltage. if 5v is desired, the LTC1174-5 is ideal for this application as it requires the least components. figure 5 shows the schematic for this application. note that the
10 LTC1174 LTC1174-3.3/LTC1174-5 1174fe applicatio s i for atio wu uu output voltage is now taken off the gnd pin. therefore, the maximum input voltage is now determined by the difference between the absolute maximum voltage rating and the output voltage. a maximum of 12v is specified in figure 5, giving the circuit a 1.5v of headroom for v in . note that the circuit can operate from a minimum of 4v, making it ideal for a 4 nicad cell application. for a higher output current circuit, please refer to the typical applications section. absolute maximum ratings and latchup prevention the absolute maximum ratings specify that sw (pin 5) can never exceed v in (pin 6) by more than 0.3v. normally this situation should never occur. it could, however, if the output is held up while the supply is pulled down. a con- dition where this could potentially occur is when a battery is supplying power to an LTC1174/LTC1174-3.3/ LTC1174-5 regulator and also to one or more loads in parallel with the the regulator? v in . if the battery is dis- connected while the LTC1174/LTC1174-3.3/LTC1174-5 regulator is supplying a light load and one of the parallel circuits is a heavy load, the input capacitor of the LTC1174/ LTC1174-3.3/LTC1174-5 regulator could be pulled down faster than the output capacitor, causing the absolute maximum ratings to be exceeded. the result is often a latchup which can be destructive if v in is reapplied. bat- tery disconnect is possible as a result of mechanical stress, bad battery contacts or use of a lithium-ion battery with a built-in internal disconnect. the user needs to assess his/her application to determine whether this situation could occur. if so, additional protection is necessary. prevention against latchup can be accomplished by sim- ply connecting a schottky diode across the sw and v in pins as shown in figure 6. the diode will normally be reverse biased unless v in is pulled below v out at which time the diode will clamp the (v out ?v in ) potential to less than the 0.6v required for latchup. note that a low leakage schottky should be used to minimize the effect on no-load supply current. schottky diodes such as mbr0530, bas85 and bat84 work well. another more serious effect of the protection diode leakage is that at no load with nothing to provide a sink for this leakage current, the output voltage can potentially float above the maximum allowable toler- ance. to prevent this from occuring, a resistor must be connected between v out and ground with a value low enough to sink the maximum possible leakage current. figure 4. LTC1174 adjustable configuration r2 r1 1 v out 1174 f04 100pf* 6.8nf** * ** adjustable applications low noise applications LTC1174 v fb figure 5. positive-to-negative 5v converter 3 shutdown 2 7 6 8 1 5 4 50 h** v out ?v 45ma mbrs140t3 1174 f05 * ** avx tpsd476k016 coiltronics ctx50-4 input voltage 4v to 12v 0.1 f 47 f* 16v 2 47 f* 16v 2 LTC1174hv-5 lb in lb out i pgm gnd v in v out sw + + figure 6. preventing absolute maximum ratings from being exceeded 1174 f06 v in v out latchup protection schottky sw LTC1174 LTC1174-3.3 LTC1174-5 +
11 LTC1174 LTC1174-3.3/LTC1174-5 1174fe figure 7. LTC1174 layout diagram (see board layout checklist) applicatio s i for atio wu uu board layout checklist when laying out the printed circuit board, the following checklist should be used to ensure proper operation of the LTC1174. these items are also illustrated graphically in the layout diagram in figure 7. check the following in your layout: 1. is the schottky catch diode closely connected between ground (pin 4) and switch (pin 5)? 2. is the ??plate of c in closely connected to v in (pin 6)? this capacitor provides the ac current to the internal p-channel mosfet. 3. is the 0.1 f v in decoupling capacitor closely conected between v in (pin 6) and ground (pin 4)? this capacitor carries the high frequency peak currents. 4. is the shutdown (pin 8) actively pulled to v in during normal operation? the shutdown pin is high imped- ance and must not be allowed to float. 5. is the i pgm (pin 7) pulled either to v in or ground? the i pgm pin is high impedance and must not be allowed to float. 3 LTC1174 2 sw r1 8 7 6 1 5 4 l v out d 1174 f07 output divider required with adjustable version only 0.1 f lb out lb in gnd shutdown i pgm v in r2 bold lines indicate high current path v in c in c out v out (v fb ) + + design example as a design example, assume v in = 9v (nominal), v out = 5v, and i out = 350ma maximum. the LTC1174-5 is used for this application, with i pgm (pin 7) connected to v in . the minmum value of l is determined by assuming the LTC1174-5 is operating in continuous mode. figure 8. continuous inductor current inductor current time i peak i v avg current = i out = = 350ma i peak + i v 2 1174 f08 with i out = 350ma and i peak = 0.6a (i pgm = v in ), i v = 0.1a.the peak-to-peak ripple inductor current, i ripple , is 0.5a and is also equal to: i vv l a ripple out d pp = + ? ? ? ? ? ? () ? ? 410 6
12 LTC1174 LTC1174-3.3/LTC1174-5 1174fe applicatio s i for atio wu uu solving for l in the above equation and with v d = 0.6v, l = 44.8 h. the next higher standard value of l is 50 h (example: coiltronics ctx50-4). the operating frequency, neglecting voltage across diode v d is: f v v khz out in ? ? ? ? ? ? ? = 2 5 10 1 111 5 . with the value of l determined, the requirements for c in and c out are calculated. for c in , its rms current rating should be at least: i ivvv v a ma rms out out in out in rms = ? () [] () = 12 174 / for c out , the rms current rating should be at least: i i a ma rms peak rms () = 2 300 now allow v in to drop to 6v. at this minimum input voltage the operating frequency will decrease. the new frequency is 42khz. table 1. inductor manufacturers manufacturer part number coilcraft dt3316 series 1102 silver lake road cary, il 60013 (708) 639-2361 coiltronics inc. econo-pac 6000 park of commerce blvd. octa-pac boca raton, fl 33487 (407) 241-7876 gowanda electronics corporation ga10 series 1 industrial place gowanda, ny 14070 (716) 532-2234 sumida electric co. ltd. cd 54 series 637 e. golf road, suite 209 cd 75 series arlington heights, il 60005 (708) 956-0666/7 table 2. capacitor manufacturers manufacturer part number avx corporation tps series p.o. box 887 taj series myrtle beach, sc 29578 (803) 448-9411 nichicon america corporation pl series 927 east state parkway schaberg, il 60173 (708) 843-7500 sanyo video components os-con series 2001 sanyo avenue san diego, ca 92173 (619) 661-6385 attn: sales dept.
13 LTC1174 LTC1174-3.3/LTC1174-5 1174fe typical applicatio s u high efficiency 3.3v regulator 6v to 5v step-down regulator with low-battery detection 1174 ta03 input voltage 6v 3 LTC1174-5 lb in lb out i pgm gnd v in shutdown v out sw 2 7 6 8 1 5 4 l1 ? 100 h v out 5v 365ma 47 f** 16v 2 d1 0.1 f *low- battery indicator 4.7k 162k 47.5k * ** d1 ? low-battery indicator is set to trip at v in = 5.5v avx tpsd476k016 = mbrs140t3 (surface mount) 1n5818 l1 selection manufacturer coiltronics sumida gowanda part no. ctx100-4 cd75-101 ga10-103k type surface mount surface mount through hole + 47 f** 16v 2 + 1174 ta04 3 LTC1174-3.3 lb in lb out i pgm gnd v in shutdown v out sw 2 7 6 8 1 5 4 50 h ? v out 3.3v 425ma 22 f* 25v 3 1n5818 0.1 f 47 f** 16v 2 input voltage 4v to 12.5v * ** ? avx tpsd226k025 avx tpsd476k016 coiltronics ctx50-4 + +
14 LTC1174 LTC1174-3.3/LTC1174-5 1174fe low noise 3v regulator positive-to-negative ( 5v) converter typical applicatio s u 1174 ta05 3 LTC1174 lb in lb out i pgm gnd v in shutdown v fb sw 2 7 6 8 1 5 4 50 h ? v out 3v 450ma 22 f* 25v 3 1n5818 0.1 f 100 f** 10v 2 input voltage 4v to 12.5v * ** ? avx tpsd226k025 avx tpsd105k010 coiltronics ctx50-4 42k 30k 6.8nf + + * ** *** d1 ? low-battery indicator is set to trip at v in = 4.4v avx tpsd106k035 avx tpsd105k010 = mbrs130lt3 (surface mount) 1n5818 l1 selection manufacturer coiltronics coilcraft sumida gowanda part no. ctx50-3 dt3316-473 cd54-470 ga10-472k type surface mount surface mount surface mount through hole 1174 ta06 input voltage 4v to 12.5v 3 LTC1174hv-5 lb in lb out i pgm gnd v in shutdown v out sw 2 7 6 8 1 5 4 l1 ? 50 h v out ?v 10 f** 35v 2 d1 0.1 f 100 f*** 10v *low- battery indicator 4.7k 280k 43k v in (v) 4 6 8 10 12.5 i out max (ma) 110 140 170 200 235 + +
15 LTC1174 LTC1174-3.3/LTC1174-5 1174fe positive-to-negative ( 3.3v) converter negative boost converter 1174 ta07 input voltage 4v to 13.5v 3 LTC1174hv-3.3 lb in lb out i pgm gnd v in shutdown v out sw 2 7 6 8 1 5 4 l1 ? 50 h v out 3.3v 210ma 33 f** 20v 2 d1 0.1 f 100 f*** 10v 2 *low- battery indicator 4.7k 220k 43k * ** *** d1 ? low-battery indicator is set to trip at v in = 4.4v avx tpsd336k020 avx tpsd105k010 = mbrs140t3 (surface mount) 1n5818 l1 selection manufacturer coiltronics coilcraft sumida gowanda part no. ctx50-3 dt3316-473 cd54-470 ga10-472k type surface mount surface mount surface mount through hole i out max (ma) 175 205 230 255 v in (v) 4 5 6 7 + + 1174 ta08 input voltage ?v 3 LTC1174-3.3 lb in lb out i pgm gnd v in shutdown v out sw 2 7 6 8 1 5 4 l1 ? 50 h v out ?v 175ma 33 f* 16v 2 d1 0.1 f 33 f* 20v 2 310k 50k * d1 ? avx tpsd336k020 = mbrs140t3 (surface mount) 1n5818 l1 selection 0.1 f manufacturer coiltronics coilcraft sumida gowanda part no. ctx50-3 dt3316-473 cd54-470 ga10-472k type surface mount surface mount surface mount through hole + + typical applicatio s u
16 LTC1174 LTC1174-3.3/LTC1174-5 1174fe lcd display power supply 9v to 5v pre-post regulator 1174 ta09 input voltage 6v to 12.5v 3 LTC1174 lb in lb out i pgm gnd v in shutdown v fb sw 2 7 6 8 1 5 4 l1 ? 50 h v out 5v 150ma d1 1 f solid tantalum 47 f** 16v, 2 110k ?? 0.1 f * ** d1 ? sanyo os-con avx tpsd476k016 = mbrs140t3 (surface mount) 1n5818 l1 selection manufacturer coiltronics coilcraft sumida gowanda part no. ctx50-3 dt3316-473 cd54-470 ga10-472k type surface mount surface mount surface mount through hole ?? use 1% metal film resistors 30.1k ?? lt 1121-5 out gnd 8 1 5 v in shutdown 3 0.1 f 100 f* 16v 100pf + + + 1174 ta10 input voltage 4v to 12.5v 3 LTC1174 lb in lb out i pgm gnd v in shutdown v fb sw 2 7 6 8 1 5 4 l1 ? 100 h v out 24v 50ma at v in = 9v 47 f** 16v 2 0.1 f 10 f* 50v 4 1n914 998k ?? v in (v) 4 5 6 7 8 9 10 11 12 i out max (ma) 20 25 30 35 43 50 55 60 65 si9435 d1 50k ?? 56.2k ?? 0.1 f * ** d1 ? avx taje106k050 avx tpsd476k016 = mbrs140t3 (surface mount) 1n5818 l1 selection manufacturer coiltronics coilcraft sumida gowanda part no. ctx100-3 dt3316-104 cd75-101 ga10-103k type surface mount surface mount surface mount through hole ?? use 1% metal film resistors 2n2222 2n5210 + + typical applicatio s u
17 LTC1174 LTC1174-3.3/LTC1174-5 1174fe 9v to 5v, 5v outputs 9v to 12v, 12v outputs typical applicatio s u 1174 ta11 input voltage 4v to 12.5v 3 LTC1174hv-5 lb in lb out i pgm gnd v in shutdown v out sw 2 7 6 8 1 5 4 l1b ? 100 h ? out ?v 135ma at v in = 9v 3.3 f** 100 f* 16v mbrs140t3 l1a ? 100 h v out 5v 135ma at v in = 9v 0.1 f 0.1 f * ** ? sanyo os-con wima mks2 coiltronics ctx100-4 v in (v) 4 6 8 10 12 13 i out max (ma) 75 100 125 145 160 180 100 f* 20v 100 f* 16v l1a l1b 2 3 4 1 ctx100-4 mbrs140t3 + + + 1174 ta12 input voltage 4v to 12.5v 3 LTC1174 lb in lb out i pgm gnd v in shutdown v fb sw 2 7 6 8 1 5 4 l1b ? 100 h ? out ?2v 55ma at v in = 9v 3.3 f** 1n914 si9430dy mbrs140t3 mbrs140t3 l1a ? 100 h 1 2 4 3 v out 12v 55ma at v in = 9v 0.1 f * ** ? ?? avx tajd226k035 wima mks2 coiltronics ctx100-4 use 1% metal film resistors v in (v) 4 5 6 7 8 9 10 11 12 i out max (ma) 20 25 35 45 50 55 62 67 73 22 f* 35v 3 l1a l1b 2 3 4 1 ctx100-4 301k ?? 22 f* 35v 2 34k ?? + + 22 f* 35v 2 +
18 LTC1174 LTC1174-3.3/LTC1174-5 1174fe automatic current selection buck-boost converter typical applicatio s u 1174 ta13 input voltage 6v to 12.5v 3 LTC1174-5 lb in lb out i pgm gnd v in shutdown v out sw 2 7 6 8 1 5 4 50 h ? v out 5v 0ma to 320ma 100 f* 20v 100 f* 16v 1n5818 100k * ? sanyo os-con capacitor coiltronics ctx50-4 0.1 f 100k 36.5k tpo610l 100k + + 1174 ta14 input voltage 4v to 12v 3 LTC1174hv-5 lb in lb out i pgm gnd v in shutdown v out sw 2 7 6 8 1 5 4 3.3 f** l1a ? 100 h 1 2 l2a ? 100 h 4 3 v out 5v 160ma 0.1 f * ** ? sanyo os-con wima mks2 coiltronics ctx100-4 100 f* 20v l1a l1b 2 3 4 1 ctx100-4 100 f* 16v 1n5818 + +
19 LTC1174 LTC1174-3.3/LTC1174-5 1174fe 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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. u package descriptio n8 package 8-lead pdip (narrow .300 inch) (reference ltc dwg # 05-08-1510) s8 package 8-lead plastic small outline (narrow .150 inch) (reference ltc dwg # 05-08-1610) n8 1002 .065 (1.651) typ .045 ?.065 (1.143 ?1.651) .130 .005 (3.302 0.127) .020 (0.508) min .018 .003 (0.457 0.076) .120 (3.048) min .008 ?.015 (0.203 ?0.381) .300 ?.325 (7.620 ?8.255) .325 +.035 ?015 +0.889 0.381 8.255 () 12 3 4 87 6 5 .255 .015* (6.477 0.381) .400* (10.160) max note: 1. dimensions are inches millimeters *these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .010 inch (0.254mm) .100 (2.54) bsc .016 ?.050 (0.406 ?1.270) .010 ?.020 (0.254 ?0.508) 45 0 ?8 typ .008 ?.010 (0.203 ?0.254) so8 0303 .053 ?.069 (1.346 ?1.752) .014 ?.019 (0.355 ?0.483) typ .004 ?.010 (0.101 ?0.254) .050 (1.270) bsc 1 2 3 4 .150 ?.157 (3.810 ?3.988) note 3 8 7 6 5 .189 ?.197 (4.801 ?5.004) note 3 .228 ?.244 (5.791 ?6.197) .245 min .160 .005 recommended solder pad layout .045 .005 .050 bsc .030 .005 typ inches (millimeters) note: 1. dimensions in 2. drawing not to scale 3. these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .006" (0.15mm)
20 LTC1174 LTC1174-3.3/LTC1174-5 1174fe ? linear technology corporation 1994 lt 1006 rev e ?printed in usa battery charger related parts part number description comments lt 1074/lt1076 step-down switching regulator 100khz, 5a (lt1074) or 2a (lt1076) monolithic ltc1147 high efficiency step-down dc/dc controller 8-pin controller ltc1265 1.2a high efficiency step-down dc/dc regulator burst mode operation, monolithic lt1375/lt1376 1.5a 500khz step-down switching regulator high frequency small inductor ltc1574 high efficiency step-down dc/dc regulator LTC1174 with internal schottky diode lt1611 inverting 1.4mhz switching regulator in sot-23 5v at 150ma from 5v input, 1mv p-p output ripple, sot-23 package ltc1701 1mhz step-down dc/dc converter in sot-23 v in = 2.5v to 5.5v, i q = 135 a, v out = 5v to 1.25v ltc1707 high efficiency synchronous step-down regulator v in = 2.85 to 8.5v, selectable burst mode operation, 600ma output current, so-8 package ltc1877 high efficiency synchronous step-down regulator 600ma at v in = 5v, 2.65v to 10v = v in , i q = 10 a linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com typical applicatio u 1174 ta15 input voltage 8v to 12.5v 3 LTC1174 lb in lb out i pgm gnd v in shutdown v fb sw 2 7 6 8 1 5 4 d1 l1 ? 50 h v out to 4 nicad battery 0.1 f 100 f** 10v 33k 150k v in (v) 8 9 10 11 12 i out max (ma) 320 325 330 335 335 * ** d1,d2 ? avx tajd226k020 avx tajd107k010 = mbrs140t3 (surface mount) 1n5818 l1 selection manufacturer coiltronics coilcraft sumida gowanda part no. ctx50-2p dt3316-473 cd54-470 ga10-472k type surface mount surface mount surface mount through hole 22 f* 20v 2 d2 + +

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