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1 lt1529 lt1529-3.3/lt1529-5 152935fb 3a low dropout regulators with micropower quiescent current and shutdown the lt 1529/lt1529-3.3/lt1529-5 are 3a low dropout regulators with micropower quiescent current and shut- down. the devices are capable of supplying 3a of output current with a dropout voltage of 0.6v. designed for use in battery-powered systems, the low quiescent current, 50 a operating and 16 a in shutdown, make them an ideal choice. the quiescent current is well controlled; it does not rise in dropout as it does with many other low dropout pnp regulators. other features of the lt1529 /lt1529-3.3/lt1529-5 in- clude the ability to operate with small output capacitors. they are stable with 22 f on the output while most older devices require up to 100 f for stability. small ceramic capacitors can be used, enhancing manufacturabiltiy. also the input may be connected to voltages lower than the output voltage, including negative voltages, without re- verse current flow from output to input. this makes the lt1529/lt1529-3.3/lt1529-5 ideal for backup power situations where the output is held high and the input is at ground or reversed. under these conditions, only 16 a will flow from the output pin to ground. the devices are available in 5-lead to-220 and 5-lead dd packages. dropout voltage: 0.6v at i out = 3a output current: 3a quiescent current: 50 a no protection diodes needed adjustable output from 3.8v to 14v 3.3v and 5v fixed output voltages controlled quiescent current in dropout shutdown i q = 16 a stable with 22 f output capacitor reverse battery protection no reverse current thermal limiting output current (a) 0 0 dropout voltage (v) 0.1 0.2 0.3 0.4 0.6 0.5 1.0 1.5 2.0 lt1529 ?ta02 2.5 3.0 0.5 dropout voltage 5v supply with shutdown high efficiency regulator regulator for battery-powered systems post regulator for switching supplies 5v to 3.3v logic regulator + v in v in > 5.5v 22 f 5v 3a 1 2 3 lt1529 ?ta01 5 4 output sense lt1529-5 shdn gnd v shdn (pin 4) < 0.25 > 2.8 nc output off on on descriptio u features applicatio s u typical applicatio u , ltc and lt are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners.
2 lt1529 lt1529-3.3/lt1529-5 152935fb output short-circuit duration ......................... indefinite storage temperature range ................ 65 c to 150 c operating junction temperature range commercial .......................................... 0 c to 125 c industrial ......................................... 45 c to 125 c lead temperature (soldering, 10 sec).................. 300 c * for applications requiring input voltage ratings greater than 15v, contact the factory. a u g w a w u w a r b s o lu t exi t i s input voltage ...................................................... 15v* output pin reverse current .............................. 10ma sense pin current .............................................. 10ma adj pin current ................................................... 10ma shdn pin input voltage (note 2) .............. 6.5v, 0.6v shdn pin input current (note 2) .......................... 5ma wu u package / o rder i for atio order part number lt1529cq lt1529cq-3.3 lt1529cq-5 lt1529iq lt1529iq-3.3 lt1529iq-5 *pin 2 = sense for lt1529-3.3/lt1529-5 = adj for lt1529 order part number lt1529ct lt1529ct-3.3 lt1529ct-5 lt1529it lt1529it-3.3 lt1529it-5 *pin 2 = sense for lt1529-3.3/lt1529-5 = adj for lt1529 t jmax = 125 c, ja 30 c/ w parameter conditions min typ max units regulated output voltage lt1529-3.3 v in = 3.8v, i out = 1ma, t j = 25 c 3.250 3.300 3.350 v (note 4) 4.3v < v in < 15v, 1ma < i out < 3a 3.200 3.300 3.400 v lt1529-5 v in = 5.5v, i out = 1ma, t j = 25 c 4.925 5.000 5.075 v 6v < v in < 15v, 1ma < i out < 3a 4.850 5.000 5.150 v lt1529 (note 5) v in = 4.3v, i out = 1ma, t j = 25 c 3.695 3.750 3.805 v 4.8v < v in < 15v, 1ma < i out < 3a 3.640 3.750 3.860 v line regulation lt1529-3.3 ? v in = 3.8v to 15v, i out = 1ma 1.5 10 mv lt1529-5 ? v in = 5.5v to 15v, i out = 1ma 1.5 10 mv lt1529 (note 5) ? v in = 4.3v to 15v, i out = 1ma 1.5 10 mv load regulation lt1529-3.3 ? i load = 1ma to 3a, v in = 4.3v, t j = 25 c520mv ? i load = 1ma to 3a, v in = 4.3v 12 30 mv lt1529-5 ? i load = 1ma to 3a, v in = 6v, t j = 25 c520mv ? i load = 1ma to 3a, v in = 6v 12 30 mv lt1529 (note 5) ? i load = 1ma to 3a, v in = 4.8v, t j = 25 c520mv ? i load = 1ma to 3a, v in = 4.8v 12 30 mv dropout voltage i load = 10ma, t j = 25 c 110 180 mv (note 6) i load = 10ma 250 mv i load = 100ma, t j = 25 c 200 300 mv i load = 100ma 400 mv e lectr ic al c c hara terist ics v in shdn gnd sense/adj* output q package 5-lead plastic dd pak tab is gnd front view 5 4 3 2 1 t package 5-lead plastic to-220 front view tab is gnd 5 4 3 2 1 v in shdn gnd sense/adj* output (note 1) t jmax = 125 c, ja 50 c/ w the denotes specifications which apply over the operating temperature range, otherwise specificatons are at t a = 25 c. (note 3) consult ltc marketing for parts specified with wider operating temperature ranges.
3 lt1529 lt1529-3.3/lt1529-5 152935fb e lectr ic al c c hara terist ics parameter conditions min typ max units dropout voltage i load = 700ma, t j = 25 c 320 430 mv (note 6) i load = 700ma 550 mv i load = 1.5a, t j = 25 c 430 550 mv i load = 1.5a 700 mv i load = 3a, t j = 25 c 600 750 mv i load = 3a 950 mv gnd pin current i load = 0ma, t j = 25 c 50 100 a (note 7) i load = 0ma, t j = 125 c (note 8) 400 a i load = 100ma, t j = 25 c 0.6 1.0 ma i load = 100ma, t j = 125 c (note 8) 1.0 ma i load = 700ma 5.5 12 ma i load = 1.5a 20 40 ma i load = 3a 80 160 ma adj pin bias current (notes 5, 9) t j = 25 c 150 300 na shutdown threshold v out = off to on 1.20 2.8 v v out = on to off 0.25 0.75 v shdn pin current (note 10) v shdn = 0v 4.5 10 a quiescent current in shutdown v in = v out (nominal) + 1v, v shdn = 0v 15 30 a (note 11) ripple rejection v in ?v out = 1v (avg), v ripple = 0.5v p-p ,5062db f ripple = 120hz, i load = 1.5a current limit v in ?v out = 7v, t j = 25 c5a v in = v out (nominal) + 1.5v, ? v out = 0.1v 3.2 4.7 a input reverse leakage current v in = 15v, v out = 0v 1.0 ma reverse output current (note 12) lt1529-3.3 v out = 3.3v, v in = 0v 16 a lt1529-5 v out = 5v, v in = 0v 16 a lt1529 (note 6) v out = 3.8v, v in = 0v 16 a note 1: absolute maximum ratings are those values beyond which the life of a device may be impaired. note 2: the shdn pin input voltage rating is required for a low impedance source. internal protection devices connected to the shdn pin will turn on and clamp the pin to approximately 7v or 0.6v. this range allows the use of 5v logic devices to drive the pin directly. for high impedance sources or logic running on supply voltages greater than 5.5v, the maximum current driven into the shdn pin must be limited to less than 5ma. note 3: the device is tested under pulse load conditions such that t j = t a . note 4: operating conditions are limited by maximum junction temperature. the regulated output voltage specification will not apply for all possible combinations of input voltage and output current. when operating at maximum input voltage, the output current range must be limited. when operating at maximum output current the input voltage range must be limited. note 5: the lt1529 is tested and specified with the adj pin connected to the output pin. note 6: dropout voltage is the minimum input/output voltage required to maintain regulation at the specified output current. in dropout the output voltage will be equal to (v in ?v dropout ). note 7: gnd pin current is tested with v in = v out (nominal) and a current source load. this means that the device is tested while operating in its dropout region. this is the worst-case gnd pin current. the gnd pin current will decrease slightly at higher input voltages. note 8: gnd pin current will rise at t j > 75 c. this is due to internal circuitry designed to compensate for leakage currents in the output transistor at high temperatures. this allows quiescent current to be minimized at lower temperatures, yet maintain output regulation at high temperatures with light loads. see quiescent current curve in typical performance characteristics. note 9: adj pin bias current flows into the adj pin. note 10: shdn pin current at v shdn = 0v flows out of the shdn pin. note 11: quiescent current in shutdown is equal to the sum total of the shdn pin current (5 a) and the gnd pin current (10 a). note 12: reverse output current is tested with the v in pin grounded and the output pin forced to the rated output voltage. this current flows into the output pin and out of the gnd pin. the denotes specifications which apply over the operating temperature range, otherwise specificatons are at t a = 25 c. (note 3)
4 lt1529 lt1529-3.3/lt1529-5 152935fb quiescent current cc hara terist ics uw a t y p i ca lper f o r c e temperature ( c) ?0 0 quiescent current ( a) 100 250 0 50 75 lt1529 ?g03 50 200 150 ?5 25 100 125 v in = 6v r l = v shdn = open v shdn = 0v guaranteed dropout voltage dropout voltage temperature ( c) ?0 dropout voltage (v) 0.7 a b c d e f 25 lt1529 ?g02 0.4 0.2 ?5 0 50 0.1 0 0.8 0.6 0.5 0.3 75 100 125 a: i load = 3a b: i load = 1.5a c: i load = 700ma d: i load = 300ma e: i load = 100ma f: i load = 10ma lt1529 quiescent current input voltage (v) 0 quiescent current ( a) 150 200 250 8 lt1529 ?g06 100 50 125 175 225 75 25 0 2 4 6 19 3 5 7 10 i load = 0 r l = v out = v adj v shdn = open (high) v shdn = 0v lt1529-3.3 quiescent current input voltage (v) 0 quiescent current ( a) 150 200 250 8 lt1529 ?g04 100 50 125 175 225 75 25 0 2 4 6 19 3 5 7 10 i load = 0 r l = v shdn = open (high) v shdn = 0v lt1529-5 quiescent current input voltage (v) 0 quiescent current ( a) 150 200 250 8 lt1529 ?g05 100 50 125 175 225 75 25 0 2 4 6 19 3 5 7 10 i load = 0 r l = v shdn = open (high) v shdn = 0v lt1529-3.3 output voltage temperature ( c) ?0 output voltage (v) 3.375 25 lt1529 ?g07 3.300 3.250 ?5 0 50 3.225 3.200 3.400 3.350 3.325 3.275 75 100 125 i load = 1ma lt1529-5 output voltage temperature ( c) ?0 output voltage (v) 5.075 25 lt1529 ?g08 5.000 4.950 ?5 0 50 4.925 4.900 5.100 5.050 5.025 4.975 75 100 125 i load = 1ma lt1529 adj pin voltage temperature ( c) ?0 adj pin voltage (v) 3.825 25 lt1529 ?g09 3.750 3.700 ?5 0 50 3.675 3.650 3.850 3.800 3.775 3.725 75 100 125 i load = 1ma output current (a) 0 0 dropout voltage (v) 0.2 0.3 0.4 0.5 0.6 0.7 0.5 1.0 1.5 2.0 lt1529 ?g01 2.5 0.8 0.9 1.0 0.1 3.0 = test point
5 lt1529 lt1529-3.3/lt1529-5 152935fb cc hara terist ics uw a t y p i ca lper f o r c e lt1529-3.3 gnd pin current lt1529-5 gnd pin current lt1529 gnd pin current lt1529-5 gnd pin current gnd pin current shdn pin threshold (off-to-on) lt1529-3.3 gnd pin current lt1529 gnd pin current input voltage (v) 0 gnd pin current (ma) 60 80 100 8 lt1529 ?g15 40 20 50 70 90 30 10 0 2 4 6 19 3 5 7 10 t j = 25 c v out = v adj *for v out = 3.75v r load = 1.25w i load = 3a* r load = 2.5 ? i load = 1.5a* r load = 5.3 ? i load = 700ma* output current (a) 0 0 gnd pin current (ma) 20 30 40 50 60 70 0.5 1.0 1.5 2.0 lt1529 ?g16 2.5 80 90 100 10 3.0 v in = 3.75v (lt1529) v in = 3.3v (lt1529-3.3) v in = 5v (lt1529-5) device is operating in dropout t j = 125 c t j = 50 c t j = 25 c shdn pin threshold (on-to-off) temperature ( c) ?0 0 shdn threshold (v) 0.2 0.6 0.8 1.0 2.0 1.4 0 50 75 lt1529 ?g17 0.4 1.6 1.8 1.2 ?5 25 100 125 i load = 1ma temperature ( c) ?0 0 shdn threshold (v) 0.2 0.6 0.8 1.0 2.0 1.4 0 50 75 lt1529 ?g18 0.4 1.6 1.8 1.2 ?5 25 100 125 i load = 3a i load = 1ma input voltage (v) 0 gnd pin current (ma) 3.0 4.0 5.0 8 lt1529 ?g10 2.0 1.0 2.5 3.5 4.5 1.5 0.5 0 2 4 6 19 3 5 7 10 t j = 25 c v out = v sense *for v out = 3.3v r load = 6.6 ? i load = 500ma* r load = 11 ? i load = 300ma* r load = 33 ? i load = 100ma* r load = 330 ? i load = 10ma* input voltage (v) 0 gnd pin current (ma) 60 80 100 8 lt1529 ?g13 40 20 50 70 90 30 10 0 2 4 6 19 3 5 7 10 t j = 25 c v out = v sense r load = 1.1 ? i load = 3a* r load = 2.2 ? i load = 1.5a* r load = 4.7 ? i load = 700ma* *for v out = 3.3v input voltage (v) 0 gnd pin current (ma) 60 80 100 8 lt1529 ?g14 40 20 50 70 90 30 10 0 2 4 6 19 3 5 7 10 t j = 25 c v out = v sense *for v out = 5v r load = 1.7 ? i load = 3a* r load = 3.3 ? i load = 1.5a* r load = 7.1 ? i load = 700ma* input voltage (v) 0 gnd pin current (ma) 3.0 4.0 5.0 8 lt1529 ?g11 2.0 1.0 2.5 3.5 4.5 1.5 0.5 0 2 4 6 19 3 5 7 10 t j = 25 c v out = v sense *for v out = 5v r load = 10 ? i load = 500ma* r load = 16.6 ? i load = 300ma* r load = 500 ? i load = 10ma* r load = 50 ? i load = 100ma* input voltage (v) 0 gnd pin current (ma) 3.0 4.0 5.0 8 lt1529 ?g12 2.0 1.0 2.5 3.5 4.5 1.5 0.5 0 2 4 6 19 3 5 7 10 t j = 25 c v out = v adj *for v out = 3.75v r load = 7.5 ? i load = 500ma* r load = 12.5 ? i load = 300ma* r load = 375 ? i load = 10ma* r load = 38 ? i load = 100ma*
6 lt1529 lt1529-3.3/lt1529-5 152935fb cc hara terist ics uw a t y p i ca lper f o r c e shdn pin current adj pin bias current temperature ( c) ?0 0 shdn pin current ( a) 1 3 4 5 10 7 0 50 75 lt1529 ?g19 2 8 9 6 ?5 25 100 125 v shdn = 0v shdn pin input current shdn pin voltage (v) 0 0 shdn pin input current (ma) 5 15 20 25 2 4 59 lt1529 ?g20 10 13 6 7 8 temperature ( c) ?0 0 adj pin bias current (na) 50 150 200 250 500 350 0 50 75 lt1529 ?g21 100 400 450 300 ?5 25 100 125 v adj = v out = 3.75v current limit current limit reverse output current temperature ( c) ?0 output current ( a) 100 125 150 25 75 lt1529 ?g22 75 50 ?5 0 50 100 125 25 0 input voltage (v) 0 short-circuit current (a) 4 5 6 35 lt1529 ?g23 3 2 12 467 1 0 v out = 0v temperature ( c) ?0 short-circuit current (a) 4 5 6 25 75 lt1529 ?g24 3 2 ?5 0 50 100 125 1 0 v in = 7v v out = 0v reverse output current output voltage (v) 0 output current ( a) 60 80 100 8 lt1529 ?g25 40 20 50 70 90 30 10 0 2 4 6 19 3 5 7 10 lt1529 lt1529-5 lt1529-3.3 t j = 25 c, v in = 0v v out = v sense (lt1529-3.3/lt1529-5) v out = v adj (lt1529) current flows into device ripple rejection temperature ( c) ?0 56 58 62 25 75 lt 1529 ?g26 54 52 ?5 0 50 100 125 50 48 60 ripple rejection (db) (v in ?v out )avg = 1v v ripple = 0.5v p-p i load = 1.5a f = 120hz ripple rejection frequency (hz) 20 ripple rejection (db) 40 60 50 80 100 10 30 70 90 10 1k 10k 100k lt1529 ?g27 0 100 i out = 1.5a v in = v out (nominal) + 1 + 50mv rms ripple c out = 47 f c out = 22 f
7 lt1529 lt1529-3.3/lt1529-5 152935fb cc hara terist ics uw a t y p i ca lper f o r c e pi fu ctio s u uu output (pin 1): output pin. the output pin supplies power to the load. a minimum output capacitor of 22 f is required to prevent oscillations. larger values will be required to optimize transient response for large load current deltas. see the applications information section for further information on output capacitance and reverse output characteristics. sense (pin 2): sense pin. for fixed voltage versions of the lt1529 (lt1529-3.3, lt1529-5) the sense pin is the input to the error amplifier. optimum regulation will be obtained at the point where the sense pin is connected to the output pin. for most applications the sense pin is connected directly to the output pin at the regulator. in critical applications small voltage drops caused by the resistance (r p ) of pc traces between the regulator and the load, which would normally degrade regulation, may be eliminated by connecting the sense pin to the output pin at the load as shown in figure 1 (kelvin sense connec- tion). note that the voltage drop across the external pc traces will add to the dropout voltage of the regulator. the sense pin bias current is 15 a at the nominal regulated output voltage. this pin is internally clamped to 0.6v (one v be ). adj (pin 2): adjust pin. for the lt1529 (adjustable version) the adj pin is the input to the error amplifier. this + v in v in 1 2 3 lt1529 ?f01 5 4 output sense lt1529-5 r p shdn gnd load + r p figure 1. kelvin sense connection pin is internally clamped to 6v and 0.6v (one v be ). this pin has a bias current of 150na which flows into the pin. see bias current curve in the typical performance char- acteristics. the adj pin reference voltage is equal to 3.75v referenced to ground. shdn (pin 4): shutdown pin. this pin is used to put the device into shutdown. in shutdown the output of the device is turned off. this pin is active low. the device will be shut down if the shdn pin is actively pulled low. the shdn pin current with the pin pulled to ground will be 6 a. the shdn pin is internally clamped to 7v and 0.6v (one v be ). this allows the shdn pin to be driven directly by 5v logic or by open-collector logic with a pull-up resistor. the pull-up resistor is only required to supply the leakage current of the open-collector gate, normally several mi- croamperes. pull-up current must be limited to a maxi- mum of 5ma. a curve of shdn pin input current as a load regulation temperature ( c) ?0 load regulation (mv) ? 0 5 25 75 lt1529 ?g28 ?0 ?5 ?5 0 50 100 125 ?0 ?5 lt1529-5 lt1529-3.3 lt1529 v in = v out (nominal) + 1v ? i load = 100ma to 3a v adj = v out time ( s) 0 output voltage deviation (v) load current (a) 0.1 0.1 160 lt1529 ?g30 2 0.2 0 0.2 3 1 40 80 120 20 180 60 100 140 200 v in = 6v c in = 10 f c out = 22 f lt1529-5 transient response time ( s) 0 output voltage deviation (v) load current (a) 0.1 0.1 800 lt1529 ?g29 2 0.2 0 0.2 3 1 200 400 600 100 900 300 500 700 1000 v in = 6v c in = 3.3 f c out = 47 f lt1529-5 transient response
8 lt1529 lt1529-3.3/lt1529-5 152935fb pi fu ctio s u uu function of voltage appears in the typical performance characteristics. if the shdn pin is not used it can be left open circuit. the device will be active, output on, if the shdn pin is not connected. v in (pin 5): input pin. power is supplied to the device through the v in pin. the v in pin should be bypassed to ground if the device is more than six inches away from the main input filter capacitor. in general, the output imped- ance of a battery rises with frequency so it is advisable to u s a o pp l ic at i wu u i for atio the lt1529 is a 3a low dropout regulator with mi- cropower quiescent current and shutdown capable of supplying 3a of output current at a dropout voltage of 0.6v. the device operates with very low quiescent current (50 a). in shutdown the quiescent current drops to only 16 a. in addition to the low quiescent current the lt1529 incorporates several protection features which make it ideal for use in battery-powered systems. the device is protected against reverse input voltages. in battery backup applications where the output can be held up by a backup battery when the input is pulled to ground, the lt1529 acts like it has a diode in series with its output and prevents reverse current flow. adjustable operation the adjustable version of the lt1529 has an output voltage range of 3.75v to 14v. the output voltage is set by the ratio of two external resistors as shown in figure 2. the device servos the output voltage to maintain the voltage at the adj pin at 3.75v. the current in r1 is then equal to 3.75v/r1. the current in r2 is equal to the sum of the current in r1 and the adj pin bias current. the adj pin bias current, 150na at 25 c, flows through r2 into the adj pin. the output voltage can be calculated according to the formula in figure 2. the value of r1 should be less than 400k to minimize errors in the output voltage caused by the adj pin bias current. note that in shutdown the output is turned off and the divider current will be zero. curves of adj pin voltage vs temperature and adj pin include a bypass capacitor in battery-powered circuits. a bypass capacitor in the range of 1 f to 10 f is sufficient. the lt1529 is designed to withstand reverse voltages on the v in pin with respect to ground and output pin. in the case of a reversed input, which can happen if a battery is plugged in backwards, the lt1529 will act as if there is a diode in series with its input. there will be no reverse current flow into the lt1529 and no reverse voltage will appear at the load. the device will protect both itself and the load. + v in v out = 3.75v + (i adj r2) v in v out r2 r1 1 2 3 lt1529 ?f02 5 4 output sense lt1529 shdn gnd () 1 + r2 r1 v adj = 3.75v i adj = 150na at 25 c output range = 3.3v to 14v figure 2. adjustable operation bias current vs temperature appear in the typical perfor- mance characteristics. the reference voltage at the adj pin has a positive temperature coefficient of approxi- mately 15ppm/ c. the adj pin bias current has a negative temperature coefficient. these effects will tend to cancel each other. the adjustable device is specified with the adj pin tied to the output pin. this sets the output voltage to 3.75v. specifications for output voltage greater than 3.75v will be proportional to the ratio of the desired output voltage to 3.75v (v out /3.75v). for example: load regulation for an output current change of 1ma to 3a is 0.5mv typical at v out = 3.75v. at v out = 12v, load regulation would be: 12 375 05 16 v v mv mv . ? . ? ? ? ? ? ? () = ()
9 lt1529 lt1529-3.3/lt1529-5 152935fb u s a o pp l ic at i wu u i for atio thermal considerations the power handling capability of the device will be limited by the maximum rated junction temperature (125 c). the power dissipated by the device will be made up of two components: 1. output current multiplied by the input/output voltage differential: i out ?(v in ?v out ), and 2. ground pin current multiplied by the input voltage: i gnd ?v in . the gnd pin current can be found by examining the gnd pin current curves in the typical performance character- istics. power dissipation will be equal to the sum of the two components listed above. the lt1529 series regulators have internal thermal limit- ing designed to protect the device during overload condi- tions. for continuous normal load conditions the maxi- mum junction temperature rating of 125 c must not be exceeded. it is important to give careful consideration to all sources of thermal resistance from junction to ambient. additional heat sources mounted nearby must also be considered. for surface mount devices heat sinking is accomplished by using the heat spreading capabilities of the pc board and its copper traces. experiments have shown that the heat spreading copper layer does not need to be electri- cally connected to the tab of the device. the pc material can be very effective at transmitting heat between the pad area, attached to the tab of the device, and a ground or power plane layer either inside or on the opposite side of the board. although the actual thermal resistance of the pc material is high, the length/area ratio of the thermal resistor between layers is small. copper board stiffeners and plated through-holes can also be used to spread the heat generated by power devices. the following tables list thermal resistances for each package. for the to-220 package, thermal resistance is given for junction-to-case only since this package is usually mounted to a heat sink. measured values of thermal resistance for several different copper areas are listed for the dd package. all measurements were taken in still air on 3/32" fr-4 board with 1-oz copper. this data can be used as a rough guideline in estimating thermal resis- tance. the thermal resistance for each application will be affected by thermal interactions with other components as well as board size and shape. some experimentation will be necessary to determine the actual value. table 1. q package, 5-lead dd copper area topside* backside board area 2500 sq. mm 2500 sq. mm 2500 sq. mm 23 c/w 1000 sq. mm 2500 sq. mm 2500 sq. mm 25 c/w 125 sq. mm 2500 sq. mm 2500 sq. mm 33 c/w * device is mounted on topside. thermal resistance (junction-to-ambient) calculating junction temperature example: given an output voltage of 3.3v, an input voltage range of 4.5v to 5.5v, an output current range of 0ma to 500ma, and a maximum ambient temperature of 50 c, what will the maximum junction temperature be? the power dissipated by the device will be equal to: i out(max) ?(v in(max) ?v out ) + (i gnd ?v in(max) ) where, i out(max) = 500ma v in(max) = 5.5v i gnd at (i out = 500ma, v in = 5.5v) = 3.6ma so, p = 500ma ?(5.5v ?3.3v) + (3.6ma ?5.5v) = 1.12w if we use a dd package, then the thermal resistance will be in the range of 23 c/w to 33 c/w depending on copper area. so the junction temperature rise above ambient will be approximately equal to: 1.12w ?28 c/w = 31.4 c the maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: t jmax = 50 c + 31.4 c = 81.4 c output capacitance and transient performance the lt1529 is designed to be stable with a wide range of output capacitors. the minimum recommended value is 22 f with an esr of 0.2 ? or less. the lt1529 is a t package, 5-lead to-220 thermal resistance (junction-to-case) = 2.5 c/w
10 lt1529 lt1529-3.3/lt1529-5 152935fb u s a o pp l ic at i wu u i for atio micropower device and output transient response will be a function of output capacitance. see the transient re- sponse curves in the typical performance characteristics. larger values of output capacitance will decrease the peak deviations and provide improved output transient re- sponse for larger load current deltas. bypass capacitors, used to decouple individual components powered by the lt1529, will increase the effective value of the output capacitor. protection features the lt1529 incorporates several protection features which make it ideal for use in battery-powered circuits. in addi- tion to the normal protection features associated with monolithic regulators, such as current limiting and ther- mal limiting, the device is protected against reverse input voltages, and reverse voltages from output to input. current limit protection and thermal overload protection are intended to protect the device against current overload conditions at the output of the device. for normal opera- tion, the junction temperature should not exceed 125 c. the input of the device will withstand reverse voltages of 15v. current flow into the device will be limited to less than 1ma (typically less than 100 a) and no negative voltage will appear at the output. the device will protect both itself and the load. this provides protection against batteries that can be plugged in backwards. for fixed voltage versions of the device, the sense pin is internally clamped to one diode drop below ground. for the adjustable version of the device, the output pin is internally clamped at one diode drop below ground. if the output pin of an adjustable device, or the sense pin of a fixed voltage device, is pulled below ground, with the input open or grounded, current must be limited to less than 5ma. in circuits where a backup battery is required, several different input/output conditions can occur. the output voltage may be held up while the input is either pulled to ground, pulled to some intermediate voltage, or is left open circuit. current flow back into the output will vary depending on the conditions. many battery-powered cir- cuits incorporate some form of power management. the following information will help optimize battery life. table 2 summarizes the following information. the reverse output current will follow the curve in figure 3 when the input is pulled to ground. this current flows through the device to ground. the state of the shdn pin will have no effect on output current when the v in pin is pulled to ground. table 2. fault conditions v in pin shdn pin output/sense pins 1v reverse output current 15 a peak (see figure 3) open grounded > 1v reverse output current 15 a (see figure 3) 0.8v open (high) 0v output current = 0 0.8v grounded 0v output current = 0 >1.5v open (high) 0v output current = short-circuit current 15v < v in < 15v grounded 0v output current = 0 output voltage (v) 0 output current ( a) 60 80 100 8 lt1529 ?f03 40 20 50 70 90 30 10 0 2 4 6 19 3 5 7 10 lt1529 lt1529-5 lt1529-3.3 t j = 25 c, v in = 0v v out = v sense (lt1529-3.3/lt1529-5) v out = v adj (lt1529) current flows into device figure 3. reverse output current
11 lt1529 lt1529-3.3/lt1529-5 152935fb u s a o pp l ic at i wu u i for atio in some applications it may be necessary to leave the input to the lt1529 unconnected when the output is held high. this can happen when the lt1529 is powered from a rectified ac source. if the ac source is removed, then the input of the lt1529 is effectively left floating. the reverse output current also follows the curve in figure 3 if the v in pin is left open. the state of the shdn pin will have no effect on the reverse output current when the v in pin is floating. when the input of the lt1529 is forced to a voltage below its nominal output voltage and its output is held high, the output current will follow the curve shown in figure 3 . this can happen if the input of the lt1529 is connected to a discharged (low voltage) battery and the output is held up by either a backup battery or by a second regulator circuit. when the v in pin is forced below the output pin or the output pin is pulled above the v in pin, the input current will typically drop to less than 2 a (see figure 4). the state of the shdn pin will have no effect on the reverse output current when the output is pulled above the input. input voltage (v) 0 input current ( a) 3 4 5 4 lt1529 ?f04 2 1 0 1 2 3 5 lt1529-5 lt1529-3.3 v out = 3.3v (lt1529-3.3) v out = 5v (lt1529-5) figure 4. input current package descriptio u 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 circuits as described herein will not infringe on existing patent rights. q package 5-lead plastic dd pak (ltc dwg # 05-08-1461) q(dd5) 0502 .028 ?.038 (0.711 ?0.965) typ .143 +.012 ?020 () 3.632 +0.305 0.508 .067 (1.702) bsc .013 ?.023 (0.330 ?0.584) .095 ?.115 (2.413 ?2.921) .004 +.008 ?004 () 0.102 +0.203 0.102 .050 .012 (1.270 0.305) .059 (1.499) typ .045 ?.055 (1.143 ?1.397) .165 ?.180 (4.191 ?4.572) .330 ?.370 (8.382 ?9.398) .060 (1.524) typ .390 ?.415 (9.906 ?10.541) 15 typ .325 .205 .080 .565 .090 recommended solder pad layout for thicker solder paste applications .042 .067 .420 .276 .320 .420 .350 .565 .090 .042 .067 recommended solder pad layout note: 1. dimensions in inch/(millimeter) 2. drawing not to scale .300 (7.620) .075 (1.905) .183 (4.648) .060 (1.524) .060 (1.524) .256 (6.502) bottom view of dd pak hatched area is solder plated copper heat sink
12 lt1529 lt1529-3.3/lt1529-5 152935fb ? linear technology corporation 1995 lt/lt 0305 rev b ?printed in usa package descriptio u related parts part number description comments lt1120a 125ma low dropout regulator with 20 a i q includes 2.5v reference and comparator ltc 1174 high efficiency 425ma step-down dc/dc converter over 90% efficiency, includes comparator lt1303 micropower step-up dc/dc converter includes comparator, good for el displays lt1376 500khz 1.25a step-down dc/dc converter uses extremely small external components lt1521 300 a low dropout regulator with 15 a i q lowest i q low dropout regulator t package 5-lead plastic to-220 (standard) (ltc dwg # 05-08-1421) linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com t5 (to-220) 0801 .028 ?.038 (0.711 ?0.965) .067 (1.70) .135 ?.165 (3.429 ?4.191) .700 ?.728 (17.78 ?18.491) .045 ?.055 (1.143 ?1.397) .095 ?.115 (2.413 ?2.921) .013 ?.023 (0.330 ?0.584) .620 (15.75) typ .155 ?.195* (3.937 ?4.953) .152 ?.202 (3.861 ?5.131) .260 ?.320 (6.60 ?8.13) .165 ?.180 (4.191 ?4.572) .147 ?.155 (3.734 ?3.937) dia .390 ?.415 (9.906 ?10.541) .330 ?.370 (8.382 ?9.398) .460 ?.500 (11.684 ?12.700) .570 ?.620 (14.478 ?15.748) .230 ?.270 (5.842 ?6.858) bsc seating plane * measured at the seating plane

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