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lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 1 3021fc typical application features applications description 500ma, low voltage, very low dropout linear regulator the lt ? 3021 is a very low dropout voltage (vldo?) lin- ear regulator that operates from input supplies down to 0.9v. this device supplies 500ma of output current with a typical dropout voltage of 160mv. the lt3021 is ideal for low input voltage to low output voltage applications, providing comparable electrical ef? ciency to that of a switching regulator. the lt3021 regulator optimizes stability and transient response with low esr, ceramic output capacitors as small as 3.3f. other lt3021 features include 0.05% typical line regulation and 0.2% typical load regulation. in shutdown, quiescent current typically drops to 3a. internal protection circuitry includes reverse-battery pro- tection, current limiting, thermal limiting with hysteresis, and reverse-current protection. the lt3021 is available as an adjustable output device with an output range down to the 200mv reference. three ? xed output voltages, 1.2v, 1.5v and 1.8v, are also available. the lt3021 regulator is available in the low pro? le (0.75mm) 16-pin (5mm 5mm) dfn package with ex- posed pad and the 8-lead so package. 1.8v to 1.5v, 500ma vldo regulator n v in range: 0.9v to 10v n dropout voltage: 160mv typical n output current: 500ma n adjustable output (v ref = v out(min) = 200mv) n fixed output voltages: 1.2v, 1.5v, 1.8v n stable with low esr, ceramic output capacitors (3.3f minimum) n 0.2% load regulation from 0ma to 500ma n quiescent current: 120a (typ) n 3a typical quiescent current in shutdown n current limit protection n reverse-battery protection n no reverse current n thermal limiting with hysteresis n 16-pin dfn (5mm 5mm) and 8-lead so packages n low current regulators n battery-powered systems n cellular phones n pagers n wireless modems l , lt, ltc and ltm are registered trademarks of linear technology corporation. vldo is a trademark of linear technology corporation. all other trademarks are the property of their respective owners. minimum input voltage in shdn sense 3.3 f 3021 ta01 out v in 1.8v gnd lt3021-1.5 v out 1.5v 500ma 3.3 f temperature ( c) C50 minimum input voltage (v) 1.1 1.0 0.9 0.8 0.6 0.7 0.5 0.4 0.3 0.2 0.1 0 3021 ta02 25 0 C25 50 75 125 100 i l = 500ma
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 2 3021fc absolute maximum ratings in pin voltage ........................................................ 10v out pin voltage ......................................................10v input-to-output differential voltage ........................10v adj/sense pin voltage ....................................... 10v shdn pin voltage ................................................. 10v output short-circut duration ......................... inde? nite (note 1) 16 15 14 13 12 11 10 9 17 1 2 3 4 5 6 7 8 nc nc in nc in nc pgnd shdn nc nc out out nc nc adj agnd top view lt3021-adj dh package 16-lead ( 5mm 5mm ) plastic dfn t jmax = 125c, ja = 35c/ w*, jc = 3c/w** exposed pad is gnd (pin 17) connect to pins 8, 10 exposed pad must be soldered to the pcb *see the applications information section **measured junction to pin 17 16 15 14 13 12 11 10 9 17 1 2 3 4 5 6 7 8 nc nc in nc in nc pgnd shdn nc nc out out nc nc sense agnd top view lt3021-fixed dh package 16-lead ( 5mm 5mm ) plastic dfn t jmax = 125c, ja = 35c/ w*, jc = 3c/w** exposed pad is gnd (pin 17) connect to pins 8, 10 exposed pad must be soldered to the pcb *see the applications information section **measured junction to pin 17 1 2 3 4 8 7 6 5 top view in nc pgnd shdn nc out adj agnd lt3021-adj s8 package 8-lead plastic so t jmax = 150c, ja = 125c/ w*, jc = 40c/w** *see the applications information section **measured junction to pin 6 1 2 3 4 8 7 6 5 top view in nc pgnd shdn nc out sense agnd lt3021-fixed s8 package 8-lead plastic so t jmax = 150c, ja = 125c/ w*, jc = 40c/w** *see the applications information section **measured junction to pin 6 pin configuration operating junction temperature range (e, i grade) (notes 2, 3) ............................................C 40c to 125c storage temperature range dh .....................................................C 65c to 125c s8 ......................................................C 65c to 150c lead temperature (soldering, 10 sec, s8) ............ 300c
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 3 3021fc order informaiton lead free finish tape and reel part marking* package description temperature range lt3021edh#pbf lt3021edh#trpbf 3021 16-lead (5mm 5mm) plastic dfn ? 40c to 125c lt3021edh-1.2#pbf lt3021edh-1.2#trpbf 302112 16-lead (5mm 5mm) plastic dfn ? 40c to 125c lt3021edh-1.5#pbf lt3021edh-1.5#trpbf 302115 16-lead (5mm 5mm) plastic dfn ? 40c to 125c lt3021edh-1.8#pbf lt3021edh-1.8#trpbf 302118 16-lead (5mm 5mm) plastic dfn ? 40c to 125c lt3021es8#pbf lt3021es8#trpbf 3021 8-lead plastic so ? 40c to 125c lt3021es8-1.2#pbf lt3021es8-1.2#trpbf 302112 8-lead plastic so ? 40c to 125c lt3021es8-1.5#pbf lt3021es8-1.5#trpbf 302115 8-lead plastic so ? 40c to 125c lt3021es8-1.8#pbf lt3021es8-1.8#trpbf 302118 8-lead plastic so ? 40c to 125c lt3021is8-1.8#pbf lt3021is8-1.8#trpbf 302118 8-lead plastic so ? 40c to 125c lead based finish tape and reel part marking* package description temperature range lt3021edh lt3021edh#tr 3021 16-lead (5mm 5mm) plastic dfn ? 40c to 125c lt3021edh-1.2 lt3021edh-1.2#tr 302112 16-lead (5mm 5mm) plastic dfn ? 40c to 125c lt3021edh-1.5 lt3021edh-1.5#tr 302115 16-lead (5mm 5mm) plastic dfn ? 40c to 125c lt3021edh-1.8 lt3021edh-1.8#tr 302118 16-lead (5mm 5mm) plastic dfn ? 40c to 125c lt3021es8 lt3021es8#tr 3021 8-lead plastic so ? 40c to 125c lt3021es8-1.2 lt3021es8-1.2#tr 302112 8-lead plastic so ? 40c to 125c lt3021es8-1.5 lt3021es8-1.5#tr 302115 8-lead plastic so ? 40c to 125c lt3021es8-1.8 lt3021es8-1.8#tr 302118 8-lead plastic so ? 40c to 125c lt3021is8-1.8 lt3021is8-1.8#tr 302118 8-lead plastic so ? 40c to 125c consult ltc marketing for parts speci? ed with wider operating temperature ranges. *the temperature grade is identi? ed by a label on the shipping container. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel speci? cations, go to: http://www.linear.com/tapeandreel/
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 4 3021fc electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t j = 25c. symbol conditions min typ max units minimum input voltage (notes 5,14) i load = 500ma, t j > 0c i load = 500ma, t j < 0c 0.9 0.9 1.05 1.10 v v adj pin voltage (notes 4, 5) v in = 1.5v, i load = 1ma 1.15v < v in < 10v, 1ma < i load < 500ma l 196 193 200 200 204 206 mv mv regulated output voltage (note 4) lt3021-1.2 v in = 1.5v, i load = 1ma 1.5v < v in < 10v, 1ma < i load < 500ma l 1.176 1.157 1.200 1.200 1.224 1.236 v v lt3021-1.5 v in = 1.8v, i load = 1ma 1.8v < v in < 10v, 1ma < i load < 500ma l 1.470 1.447 1.500 1.500 1.530 1.545 v v lt3021-1.8 v in = 2.1v, i load = 1ma 2.1v < v in < 10v, 1ma < i load < 500ma l 1.764 1.737 1.800 1.800 1.836 1.854 v v line regulation (note 6) lt3021 v in = 1.15v to 10v, i load = 1ma lt3021-1.2 v in = 1.5v to 10v, i load = 1ma lt3021-1.5 v in = 1.8v to 10v, i load = 1ma lt3021-1.8 v in = 2.1v to 10v, i load = 1ma l l l l C1.75 C10.5 C13 C15.8 0 0 0 0 +1.75 10.5 13 15.8 mv mv mv mv load regulation (note 6) lt3021 v in = 1.15v, i load = 1ma to 500ma lt3021-1.2 v in = 1.5v, i load = 1ma to 500ma lt3021-1.5 v in = 1.8v, i load = 1ma to 500ma lt3021-1.8 v in = 2.1v, i load = 1ma to 500ma C2 C6 C7.5 C9 0.4 1 1.5 2 2 6 7.5 9 mv mv mv mv dropout voltage (notes 7, 12) i load = 10ma i load = 10ma l 45 75 110 mv mv i load = 500ma i load = 500ma l 155 190 285 mv mv gnd pin current v in = v out(nominal) + 0.4v (notes 8, 12) i load = 0ma i load = 10ma i load = 100ma i load = 500ma l l 110 920 2.25 6.20 250 10 a a ma ma output voltage noise c out = 4.7f, i load = 500ma, bw = 10hz to 100khz, v out = 1.2v 300 v rms adj pin bias current v adj = 0.2v, v in = 1.2v (notes 6, 9) 20 50 na shutdown threshold v out = off to on v out = on to off l l 0.25 0.61 0.61 0.9 v v shdn pin current (note 10) v shdn = 0v, v in = 10v v shdn = 10v, v in = 10v l l 3 1 9.5 a a quiescent current in shutdown v in = 6v, v shdn = 0v 3 9 a ripple rejection (note 6) lt3021 v in C v out = 1v, v rip = 0.5v p-p , f ripple = 120hz, i load = 500ma 70 db lt3021-1.2 v in C v out = 1v, v ripple = 0.5v p-p , f ripple = 120hz, i load = 500ma 60 db lt3021-1.5 v in C v out = 1v, v ripple = 0.5v p-p , f ripple = 120hz, i load = 500ma 58 db lt3021-1.8 v in C v out = 1v, v ripple = 0.5v p-p , f ripple = 120hz, i load = 500ma 56 db current limit (note 12) v in = 10v, v out = 0v v in = v out(nominal) + 0.5v, v out = C5% l 550 1.8 a ma input reverse leakage current v in = C10v, v out = 0v 1 20 a reverse output current (notes 11, 13) lt3021 v out = 1.2v, v in = 0v lt3021-1.2 v out = 1.2v, v in = 0v lt3021-1.5 v out = 1.5v, v in = 0v lt3021-1.8 v out = 1.8v, v in = 0v 0.5 10 10 10 5 15 15 15 a a a a
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 5 3021fc typical performance characteristics dropout voltage dropout voltage minimum input voltage output current (ma) 0 dropout voltage (mv) 250 225 200 150 175 125 100 75 50 25 0 3021 g01 200 100 300 400 500 t j = 125 c t j = 25 c temperature ( c) C50 dropout voltage (mv) 250 225 200 150 175 125 100 75 50 25 0 3021 g02 25 0 C25 50 75 125 100 i l = 1ma i l = 100ma i l = 250ma i l = 500ma i l = 50ma i l = 10ma v out = 1.2v temperature ( c) C50 minimum input voltage (v) 1.2 1.1 1.0 0.9 0.8 0.6 0.7 0.5 0.4 0.3 0.2 3021 g16 25 0 C25 50 75 125 100 i l = 500ma 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: the lt3021 regulators are tested and speci? ed under pulse load conditions such that t j t a . the lt3021e regulators are 100% tested at t a = 25c. performance at C40c and 125c is assured by design, characterization and correlation with statistical process controls. the lt3021i regulators are guaranteed over the full C40oc to 125oc operating junction temperature range. note 3: this ic includes overtemperature protection that is intended to protect the device during momentary overload conditions. junction temperature will exceed 125c when overtemperature protection is active. continuous operation above the speci? ed maximum operating junction temperature may impair device reliability. note 4: maximum junction temperature limits operating conditions. the regulated output voltage speci? cation does not apply for all possible combinations of input voltage and output current. limit the output current range if operating at maximum input voltage. limit the input voltage range if operating at maximum output current. note 5: typically the lt3021 supplies 500ma output current with a 1v input supply. the guranteed minimum input voltage for 500ma output current is 1.10v. note 6: the lt3021 is tested and speci? ed for these conditions with an external resistor divider (20k and 30.1k) setting v out to 0.5v. the external resistor divider adds 10a of output load current. the line regulation and load regulation speci? cations refer to the change in the 0.2v reference voltage, not the 0.5v output voltage. speci? cations for ? xed output voltage devices are referred to the output voltage. note 7: dropout voltage is the minimum input to output voltage differential needed to maintain regulation at a speci? ed output current. in dropout the output voltage equals: (v in C v dropout ). note 8: gnd pin current is tested with v in = v out(nominal) + 0.4v and a current source load. gnd pin current will increase in dropout. see gnd pin current curves in the typical performance characteristics section. note 9: adjust pin bias current ? ows out of the adj pin. note 10: shutdown pin current ? ows into the shdn pin. note 11: reverse output current is tested with in grounded and out forced to the rated output voltage. this current ? ows into the out pin and out of the gnd pin. for ? xed voltage devices this includes the current in the output resistor divider. note 12: the lt3021 is tested and speci? ed for these conditions with an external resistor divider (20k and 100k) setting v out to 1.2v. the external resistor divider adds 10a of load current. note 13: reverse current is higher for the case of (rated_output) < v out < v in, because the no-load recovery circuitry is active in this region and is trying to restore the output voltage to its nominal value. note 14: minimum input voltage is the minimum voltage required by the control circuit to regulate the output voltage and supply the full 500ma rated current. this speci? cation is tested at v out = 0.5v. at higher output voltages the minimum input voltage required for regulation will be equal to the regulated output voltage v out plus the dropout voltage. electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t j = 25c.
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 6 3021fc typical performance characteristics adj pin voltage adj pin bias current quiescent current output voltage output voltage output voltage quiescent current quiescent current quiescent current temperature ( c) C50 adj pin voltage (mv) 206 204 202 198 200 196 194 3021 g04 25 0 C25 50 75 125 100 temperature ( c) C50 adj pin bias current (na) 25 20 15 5 10 0 3021 g11 25 0 C25 50 75 125 100 temperature ( c) C50 250 225 200 150 175 125 100 75 50 25 0 25 0 C25 50 75 125 100 quiescent current ( a) 3021 g05 v in = 6v v out = 1.2v i l = 0 v shdn = v in v shdn = 0v temperature ( c) C50 output voltage (v) 1.23 1.22 1.21 1.20 1.19 1.18 1.17 25 75 3021 g28 C25 0 50 100 125 i load = 1ma temperature ( c) C50 output voltage (v) 1.53 1.52 1.51 1.50 1.49 1.48 1.47 25 75 3021 g23 C25 0 50 100 125 i load = 1ma temperature ( c) C50 output voltage (v) 1.83 1.82 1.81 1.80 1.79 1.78 1.77 25 75 3021 g22 C25 0 50 100 125 i load = 1ma input voltage (v) 0 quiescent current (ma) 3.0 2.5 2.0 1.0 1.5 0.5 0 3021 g03 3 2 158 47 6 10 9 v shdn = v in v shdn = 0v v out = 1.2v i l = 0 t j = 25 c input voltage (v) quiescent current (ma) 3.0 2.5 2.0 1.5 1.0 0.5 0 2468 3021 g26 10 1 03579 v out = 1.5v i l = 0 t j = 25 c v shdn = 0v v shdn = v in input voltage (v) quiescent current (ma) 3.0 2.5 2.0 1.5 1.0 0.5 0 2468 3021 g27 10 1 03579 v out = 1.8v i l = 0 t j = 25 c v shdn = 0v v shdn = v in
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 7 3021fc typical performance characteristics gnd pin current gnd pin current gnd pin current gnd pin current vs i load shdn pin threshold shdn pin input current shdn pin input current current limit reverse output current input voltage (v) 0 gnd pin current (ma) 8 7 6 4 5 3 2 1 0 8 3021 g06 2 13579 4 6 10 v out = 1.2v t j = 25 c r l = 12 i l = 100ma r l = 2.4 i l = 500ma r l = 4.8 i l = 250ma r l = 24 i l = 50ma r l = 120 i l = 10ma r l = 1.2k, i l = 1ma input voltage (v) gnd pin current (ma) 8 6 4 7 5 3 2 1 0 2468 3021 g24 10 1 03579 v out = 1.5v t j = 25 c r l = 3 i l = 500ma r l = 6 i l = 250ma r l = 15 i l = 100ma r l = 30 i l = 50ma r l = 1.5k, i l = 1ma r l = 150 i l = 10ma input voltage (v) gnd pin current (ma) 9 8 6 4 7 5 3 2 1 0 2468 3021 g25 10 1 03579 v out = 1.8v t j = 25 c r l = 3.6 i l = 500ma r l = 7.2 i l = 250ma r l = 18 i l = 100ma r l = 36 i l = 50ma r l = 1.8k, i l = 1ma r l = 180 i l = 10ma load current (ma) 0 gnd pin current (ma) 10 9 8 6 7 5 4 3 2 1 0 3021 g07 200 100 300 400 500 v shdn = 10v temperature ( c) C50 shdn pin threshold (v) 1.0 0.9 0.8 0.6 0.7 0.5 0.4 0.3 0.2 0.1 0 3021 g08 25 0 C25 50 75 125 100 i l = 1ma shdn pin voltage (v) 0 shdn pin input current ( a) 5.0 4.5 4.0 3.0 3.5 2.5 2.0 1.5 1.0 0.5 0 8 3021 g09 2 13579 4 6 10 temperature ( c) C50 0 3021 g10 25 0 C25 50 75 125 100 v shdn = 10v shdn pin input current ( a) 5 4 3 2 1 0 temperature ( c) C50 0 3021 g12 25 0 C25 50 75 125 100 v out = 0v v in = 1.7v v in = 10v current limit (a) 2.0 1.8 1.6 1.2 1.4 1.0 0.8 0.6 0.4 0.2 0 temperature ( c) C50 0 3021 g13 25 0 C25 50 75 125 100 v in = 0v v out = 1.2v reverse output current ( a) 500 450 400 300 350 250 200 150 100 50 0
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 8 3021fc typical performance characteristics input ripple rejection input ripple rejection load regulation i l = 1ma to 500ma no-load recovery threshold output noise spectral density rms output noise vs load current (10hz to 100khz) transient response frequency (hz) 10 input ripple rejection (db) 20 30 60 50 40 70 10 1k 10k 1m 3021 g14 0 100 100k v in = 1.5v + 50mv rms ripple v out = 0.5v i l = 500ma c out = 4.7 f c out = 22 f temperature ( c) C50 input ripple rejection (db) 100 90 80 60 70 50 40 30 20 10 0 3021 g15 25 0 C25 50 75 125 100 v in = 1.5v + 0.5v p-p ripple at 120hz v out = 0.5v i l = 500ma temperature ( c) C50 load regulation (mv) 2.5 2.0 1.5 0.5 1.0 0 C0.5 C1.0 C1.5 C2.0 C2.5 3021 g17 25 0 C25 50 75 125 100 v in = 1.15v v out = 0.5v *load regulation number refers to change in the 200mv reference voltage output overshoot (%) 0 output sink current (ma) 18 16 12 14 10 8 6 4 2 0 3021 g20 15 10 5 20 frequency (hz) 10 output noise spectral density ( v/ hz) 10 1 0.1 0.01 1k 100k 1m 100 10k 3021 g18 v out = 1.2v i l = 500ma c out = 4.7 f load current (ma) output noise ( v rms ) 300 250 200 150 100 50 0 0.01 1 10 100 3021 g19 0.1 v out = 1.2v c out = 4.7 f 50 s/div i out = 50ma to 500ma v in = 1.5v v out = 1.2v c out = 22 f 3021 g21 v out 50mv/div i out 500ma/div
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 9 3021fc pin functions out (pins 3, 4/pin 2): these pins supply power to the load. use a minimum output capacitor of 3.3f to prevent oscil- lations. applications with large load transients require larger output capacitors to limit peak voltage transients. see the applications information section for more information on output capacitance and reverse output characteristics. sense (pin 7/pin 3, fixed voltage device only): this pin is the sense point for the internal resistor divider. it should be tied directly to the out pins for best results. adj (pin 7/pin 3): this pin is the inverting terminal to the error ampli? er. its typical input bias current of 20na ? ows out of the pin (see curve of adj pin bias current vs tem- perature in the typical performance characteristics). the adj pin reference voltage is 200mv (referred to gnd). agnd (pin 8/pin 4): ground. pgnd (pins 10, 17/pin 6): ground. shdn (pin 9/pin 5): the shdn pin puts the lt3021 into a low power state. pulling the shdn pin low turns the output off. drive the shdn pin with either logic or an open collector/drain device with a pull-up resistor. the pull-up resistor supplies the pull-up current to the open collector/ drain logic, normally several microamperes, and the shdn pin current, typically 2.5a. if unused, connect the shdn pin to v in . the lt3021 does not function if the shdn pin is not connected. in (pins 12, 14/pin 8): these pins supply power to the device. the lt3021 requires a bypass capacitor at in if it is more than six inches away from the main input ? lter capacitor. the output impedance of a battery rises with frequency, so include a bypass capacitor in battery-pow- ered circuits. a bypass capacitor in the range of 3.3f to 10f suf? ces. the lt3021 withstands reverse voltages on the in pin with respect to ground and the out pin. in the case of a reversed input, which occurs if a battery is plugged in backwards, the lt3021 acts as if a diode is in series with its input. no reverse current ? ows into the lt3021 and no reverse voltage appears at the load. the device protects itself and the load. exposed pad (pin 17, dh16 package only): ground. solder pin 17 to the pcb ground. connect directly to pins 8, 10 for best performance. nc (pins 1, 2, 5, 6, 11, 13, 15, 16/pins 1, 7): no connect. no connect pins may be ? oated, tied to in or tied to gnd. (dh package/s8 package) block diagram (dh package/s8 package) shutdown C + C + current gain thermal shutdown r3 r2 r1 3021 bd d1 q1 d2 q2 error amp no-load recovery q3 in (12, 14/8) out (3,4/2) out sense (7/3) note: for lt3021 adjust pin (7/3) is connected to the adjust pin, r1 and r2 are external. for lt3021-1.x pin (7/3) is connected to the output sense pin, r1 and r2 are internal. gnd (8,10,17/4,6) adj (7/3) shdn (9/5) 200mv 212mv bias current and reference generator fixed v out 1.2v 1.5v 1.8v r1 20k 20k 20k r2 100k 130k 160k 25k
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 10 3021fc applications information the lt3021 is a very low dropout linear regulator capable of 1v input supply operation. devices supply 500ma of output current and dropout voltage is typically 155mv. quiescent current is typically 120a and drops to 3a in shutdown. the lt3021 incorporates several protection features, making it ideal for use in battery-powered sys- tems. the device protects itself against reverse-input and reverse-output voltages. in battery backup applications where the output is held up by a backup battery when the input is pulled to ground, the lt3021 acts as if a diode is in series with its output which prevents reverse current ? ow. in dual supply applications where the regulator load is returned to a negative supply, the output can be pulled below ground by as much as 10v without affecting start-up or normal operation. adjustable operation the lt3021s output voltage range is 0.2v to 9.5v. figure 1 shows that the output voltage is set by the ratio of two external resistors. the device regulates the output to main- tain the adj pin voltage at 200mv referenced to ground. the current in r1 equals 200mv/r1 and the current in r2 is the current in r1 minus the adj pin bias current. the adj pin bias current of 20na ? ows out of the pin. use the formula in figure 1 to calculate output voltage. an r1 value of 20k sets the resistor divider current to 10a. note that in shutdown the output is turned off and the divider current is zero. curves of adj pin voltage vs temperature and adj pin bias current vs temperature appear in the typical performance characteristics section. speci? cations for output voltages greater than 200mv are proportional to the ratio of desired output voltage to 200mv; (v out /200mv). for example, load regulation for an output current change of 1ma to 500ma is typically 0.4mv at v adj = 200mv. at v out = 1.5v, load regulation is: (1.5v/200mv) ? (0.4mv) = 3mv output capacitance and transient response the lt3021s design is stable with a wide range of output capacitors, but is optimized for low esr ceramic capacitors. the output capacitors esr affects stability, most notably with small value capacitors. use a minimum output ca- pacitor of 3.3f with an esr of 0.2 or less to prevent oscillations. the lt3021 is a low voltage device, and output load transient response is a function of output capacitance. larger values of output capacitance decrease the peak deviations and provide improved transient response for larger load current changes. for output capacitor values greater than 22f a small feedforward capacitor with a value of 300pf across the upper divider resistor (r2 in figure 1) is required. under extremely low output current conditions (i load < 30a) a low frequency small signal oscillation (200hz/8mv p-p at 1.2v output) can occur. a minimum load of 100a is recommended to prevent this instability. give extra consideration to the use of ceramic capacitors. manufacturers make ceramic capacitors with a variety of dielectrics, each with a different behavior across tempera- ture and applied voltage. the most common dielectrics are z5u, y5v, x5r and x7r. the z5u and y5v dielectrics provide high c-v products in a small package at low cost, but exhibit strong voltage and temperature coef? cients. the x5r and x7r dielectrics yield highly stable character- isitics and are more suitable for use as the output capacitor at fractionally increased cost. the x5r and x7r dielectrics both exhibit excellent voltage coef? cient characteristics. the x7r type works over a larger temperature range and exhibits better temperature stability whereas x5r is less expensive and is available in higher values. figures 2 and 3 show voltage coef? cient and temperature coef? cient comparisons between y5v and x5r material. voltage and temperature coefficients are not the only sources of problems. some ceramic capacitors have a piezoelectric response. a piezoelectric device generates voltage across its terminals due to mechanical stress, similar to the way a piezoelectric accelerometer or micro- phone works. for a ceramic capacitor, the stress can be induced by vibrations in the system or thermal transients. the resulting voltages produced can cause appreciable figure 1. adjustable operation in shdn r2 r1 3021 f01 out v in adj gnd lt3021 v out + r2 r1 v out = 200mv v adj = 200mv i adj = 20na at 25 c output range = 0.2v to 9.5v 1 + C i adj (r2) ()
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 11 3021fc applications information amounts of noise. a ceramic capacitor produced figure 4s trace in response to light tapping from a pencil. similar vibration induced behavior can masquerade as increased output voltage noise. no-load/light-load recovery a transient load step occurs when the output current changes from its maximum level to zero current or a very small load current. the output voltage responds by overshooting until the regulator lowers the amount of current it delivers to the new level. the regulator loop response time and the amount of output capacitance control the amount of overshoot. once the regulator has decreased its output current, the current provided by the resistor divider (which sets v out ) is the only current remaining to discharge the output capacitor from the level to which it overshot. the amount of time it takes for the output voltage to recover easily extends to milliseconds with microamperes of divider current and a few microfarads of output capacitance. to eliminate this problem, the lt3021 incorporates a no-load or light-load recovery circuit. this circuit is a voltage-controlled current sink that signi? cantly improves the light load transient response time by discharging the output capacitor quickly and then turning off. the cur- rent sink turns on when the output voltage exceeds 6% of the nominal output voltage. the current sink level is then proportional to the overdrive above the threshold up to a maximum of approximately 15ma. consult the curve in the typical performance characteristics for the no-load recovery threshold. if external circuitry forces the output above the no load recovery circuits threshold, the current sink turns on in an attempt to restore the output voltage to nominal. the current sink remains on until the external circuitry releases the output. however, if the external circuitry pulls the output voltage above the input voltage, or the input falls below the output, the lt3021 turns the current sink off and shuts down the bias current/reference generator circuitry. thermal considerations the lt3021s power handling capability is limited by its maximum rated junction temperature of 125c. the power dissipated by the device is comprised of two components: 1. output current multiplied by the input-to-output voltage differential: (i out )(v in C v out ) and 2. gnd pin current multiplied by the input voltage: (i gnd )(v in ). gnd pin current is found by examining the gnd pin current curves in the typical performance characteristics. power dissipation is equal to the sum of the two components listed above. figure 2. ceramic capacitor dc bias characteristics figure 3. ceramic capacitor temperature characteristics figure 4. noise resulting from tapping on a ceramic capacitor dc bias voltage (v) change in value (%) 3021 f02 20 0 C20 C40 C60 C80 C100 0 4 8 10 26 12 14 x5r y5v 16 both capacitors are 16v, 1210 case size, 10 f temperature ( c) C50 40 20 0 C20 C40 C60 C80 C100 25 75 3021 f03 C25 0 50 100 125 y5v change in value (%) x5r both capacitors are 16v, 1210 case size, 10 f 1ms/div v out = 1.3v c out = 10f i load = 0 3021 f04 1mv/div
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 12 3021fc applications information the lt3021 regulator has internal thermal limiting (with hysteresis) designed to protect the device during overload conditions. for normal continuous conditions, do not ex- ceed the maximum junction temperature rating of 125c. carefully consider all sources of thermal resistance from junction to ambient including other heat sources mounted in proximity to the lt3021. the underside of the lt3021 dh package has exposed metal (14mm 2 ) from the lead frame to where the die is attached. this allows heat to directly transfer from the die junction to the printed circuit board metal to control maximum operating junction temperature. the dual-in-line pin arrangement allows metal to extend beyond the ends of the package on the topside (component side) of a pcb. connect this metal to gnd on the pcb. the multiple in and out pins of the lt3021 also assist in spreading heat to the pcb. the lt3021 s8 package has pin 4 fused with the lead frame. this also allows heat to transfer from the die to the printed circuit board metal, therefore reducing the thermal resistance. copper board stiffeners and plated through- holes can also be used to spread the heat generated by power devices. the following tables list thermal resistance for several different board sizes and copper areas for two different packages. measurements were taken in still air on 3/32 fr-4 board with one ounce copper. table 1. measured thermal resistance for dh package copper area topside* backside board area thermal resistance (junction-to-ambient) 2500mm 2 2500mm 2 2500mm 2 30c/w 900mm 2 2500mm 2 2500mm 2 35c/w 225mm 2 2500mm 2 2500mm 2 50c/w 100mm 2 2500mm 2 2500mm 2 55c/w 50mm 2 2500mm 2 2500mm 2 65c/w table 2. measured thermal resistance for s8 package copper area topside* backside board area thermal resistance (junction-to-ambient) 2500mm 2 2500mm 2 2500mm 2 70c/w 1000mm 2 2500mm 2 2500mm 2 70c/w 225mm 2 2500mm 2 2500mm 2 78c/w 100mm 2 2500mm 2 2500mm 2 84c/w 50mm 2 2500mm 2 2500mm 2 96c/w *device is mounted on topside. calculating junction temperature example: given an output voltage of 1.2v, an input voltage range of 1.8v 10%, an output current range of 1ma to 500ma, and a maximum ambient temperature of 70c, what will the maximum junction temperature be for an application using the dh package? the power dissipated by the device is equal to: i out(max) (v in(max) C v out ) + i gnd (v in(max) ) where i out(max) = 500ma v in(max) = 1.98v i gnd at (i out = 500ma, v in = 1.98v) = 10ma so p = 500ma(1.98v C 1.2v) + 10ma(1.98v) = 0.41w the thermal resistance is in the range of 35c/w to 70c/w depending on the copper area. so the junction temperature rise above ambient is approximately equal to: 0.41w(52.5c/w) = 21.5c the maximum junction temperature equals the maximum junction temperature rise above ambient plus the maximum ambient temperature or: t jmax = 21.5c + 70c = 91.5c protection features the lt3021 incorporates several protection features that make it ideal for use in battery-powered circuits. in addition to the normal protection features associated with monolithic regulators, such as current limiting and thermal limiting, the device also protects against reverse- input voltages, reverse-output voltages and reverse out- put-to-input voltages. current limit protection and thermal overload protection protect the device against current overload conditions at the output of the device. for normal operation, do not exceed a junction temperature of 125c. the in pins of the device withstand reverse voltages of 10v. the lt3021 limits current ? ow to less than 1a and no negative voltage appears at out. the device protects both itself and the load against batteries that are plugged in backwards.
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 13 3021fc applications information the lt3021 incurs no damage if out is pulled below ground. if in is left open circuit or grounded, out can be pulled below ground by 10v. no current ? ows from the pass transistor connected to out. however, current ? ows in (but is limited by) the resistor divider that sets the out- put voltage. current ? ows from the bottom resistor in the divider and from the adj pins internal clamp through the top resistor in the divider to the external circuitry pulling out below ground. if in is powered by a voltage source, out sources current equal to its current limit capability and the lt3021 protects itself by thermal limiting. in this case, grounding shdn turns off the lt3021 and stops out from sourcing current. the lt3021 incurs no damage if the adj pin is pulled above or below ground by 10v. if in is left open circuit or grounded and adj is pulled above ground, adj acts like a 25k resistor in series with a 1v clamp (one schottky diode in series with one diode). adj acts like a 25k resistor in series with a schottky diode if pulled below ground. if in is powered by a voltage source and adj is pulled below its reference voltage, the lt3021 attempts to source its current limit capability at out. the output voltage increases to v in C v dropout with v dropout set by whatever load current the lt3021 supports. this condition can potentially dam- age external circuitry powered by the lt3021 if the output voltage increases to an unregulated high voltage. if in is powered by a voltage source and adj is pulled above its reference voltage, two situations can occur. if adj is pulled slightly above its reference voltage, the lt3021 turns off the pass transistor, no output current is sourced and the output voltage decreases to either the voltage at adj or less. if adj is pulled above its no load recovery threshold, the no load recovery circuitry turns on and attempts to sink current. out is actively pulled low and the output voltage clamps at a schottky diode above ground. please note that the behavior described above applies to the lt3021 only. if a resistor divider is connected under the same conditions, there will be additional v/r current. 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. in the case where the input is grounded, there is less than 1a of reverse output current. if the lt3021 in pin is forced below the out pin or the out pin is pulled above the in pin, input current drops to less than 10a typically. this occurs if the lt3021 input is connected to a discharged (low voltage) battery and either a backup battery or a second regulator circuit holds up the output. the state of the shdn pin has no effect on the reverse output current if out is pulled above in. input capacitance and stability the lt3021 is designed to be stable with a minimum capacitance of 3.3f placed at the in pin. ceramic capaci- tors with very low esr may be used. however, in cases where a long wire is used to connect a power supply to the input of the lt3021 (and also from the ground of the lt3021 back to the power supply ground), use of low value input capacitors combined with an output load current of 20ma or greater may result in an unstable application. this is due to the inductance of the wire forming an lc tank circuit with the input capacitor and not a result of the lt3021 being unstable. the self-inductance, or isolated inductance, of a wire is directly proportional to its length. however, the diameter of a wire does not have a major in? uence on its self-in- ductance. for example, the self inductance of a 2-awg isolated wire with a diameter of 0.26 in. is about half the inductance of a 30-awg wire with a diameter of 0.01 in. one foot of 30-awg wire has 465nh of self inductance. the overall self-inductance of a wire can be reduced in two ways. one is to divide the current ? owing towards the lt3021 between two parallel conductors and ? ows in the same direction in each. in this case, the farther the wires are placed apart from each other, the more inductance will be reduced, up to a 50% reduction when placed a few inches apart. splitting the wires basically connects two equal inductors in parallel. however, when placed in close proximity from each other, mutual inductance is added to the overall self inductance of the wires. the most effective way to reduce overall inductance is to place the forward and return-current conductors (the wire for the input and the wire for ground) in very close proximity. two 30-awg wires separated by 0.02 in. reduce the overall self-induc- tance to about one-? fth of a single isolated wire.
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 14 3021fc applications information if the lt3021 is powered by a battery mounted in close proximity on the same circuit board, a 3.3f input capacitor is suf? cient for stability. however, if the lt3021 is powered by a distant supply, use a larger value input capacitor fol- lowing the guideline of roughly 1f (in addition to the 3.3f minimum) per 8 inches of wire length. as power supply output impedance may vary, the minimum input capaci- tance needed to stabilize the application may also vary. extra capacitance may also be placed directly on the output of the power supply; however, this will require an order of magnitude more capacitance as opposed to placing extra capacitance in close proximity to the lt3021. furthermore, series resistance may be placed between the supply and the input of the lt3021 to stabilize the application; as little as 0.1 to 0.5 will suf? ce. package description dh package 16-lead plastic dfn (5mm 5mm) (reference ltc dwg # 05-08-1709) 5.00 0.10 5.00 0.10 note: 1. drawing proposed to be made variation of version (wjjd-1) in jedec package outline mo-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 0.40 0.05 bottom viewexposed pad 3.45 0.10 (2 sides) 0.75 0.05 r = 0.115 typ r = 0.20 typ 4.10 0.10 (2 sides) 1 8 16 9 pin 1 top mark (see note 6) 0.200 ref 0.00 C 0.05 (dh16) dfn 0204 0.25 0.05 pin 1 notch 0.50 bsc 4.10 0.05 (2 sides) recommended solder pad pitch and dimensions 3.45 0.05 (2 sides) 4.10 0.05 0.50 bsc 0.70 0.05 5.50 0.05 package outline 0.25 0.05
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 15 3021fc information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. package description s8 package 8-lead plastic small outline (narrow .150 inch) (reference ltc dwg # 05-08-1610) .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)
lt3021/lt3021-1.2/ lt3021-1.5/lt3021-1.8 16 3021fc 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 0608 rev c ? printed in usa related parts part number description comments lt1121/lt1121hv 150ma, micropower ldos v in : 4.2v to 30v/36v, v out : 3.75v to 30v, v do = 0.42v, i q = 30a, i sd = 16a, reverse-battery protection, sot-223, s8, z packages lt1129 700ma, micropower ldo v in : 4.2v to 30v, v out : 3.75v to 30v, v do = 0.4v, i q = 50a, i sd = 16a, dd, sot-223, s8, to220-5, tssop20 packages lt1761 100ma, low noise micropower ldo v in : 1.8v to 20v, v out : 1.22v to 20v, v do = 0.3v, i q = 20a, i sd < 1a, low noise: < 20v rmsp-p , stable with 1f ceramic capacitor, thinsot package lt1762 150ma, low noise micropower ldo v in : 1.8v to 20v, v out : 1.22v to 20v, v do = 0.3v, i q = 25a, i sd < 1a, low noise: <20v rmsp-p , ms8 package lt1763 500ma, low noise micropower ldo v in : 1.8v to 20v, v out : 1.22v to 20v, v do = 0.3v, i q = 30a, i sd < 1a, low noise: < 20v rmsp-p , s8 package lt1764/lt1764a 3a, low noise, fast transient response ldos v in : 2.7v to 20v, v out : 1.21v to 20v, v do = 0.34v, i q = 1ma, i sd < 1a, low noise: <40v rmsp-p , a version stable with ceramic capacitors, dd, to220-5 packages ltc1844 150ma, low noise, micropower vldo v in : 1.6v to 6.5v, v out(min) = 1.25v, v do = 0.09v, i q = 35a, i sd < 1a, low noise: < 30v rms , thinsot package lt1962 300ma, low noise micropower ldo v in : 1.8v to 20v, v out : 1.22v to 20v, v do = 0.27v, i q = 30a, i sd < 1a, low noise: < 20v rmsp-p , ms8 package lt1963/lt1963a 1.5a, low noise, fast transient response ldos v in : 2.1v to 20v, v out : 1.21v to 20v, v do = 0.34v, i q = 1ma, i sd < 1a, low noise: < 40v rmsp-p , a version stable with ceramic capacitors, dd, to220-5, sot223, s8 packages lt3010 50ma, high voltage, micropower ldo v in : 3v to 80v, v out : 1.275v to 60v, v do = 0.3v, i q = 30a, i sd < 1a, low noise: <100v rmsp-p , stable with 1f output capacitor, exposed ms8 package lt3020 100ma, low voltage ldo v in : 0.9v to 10v, v out : 0.2v to 5v (min), v do = 0.15v, i q = 120a, noise: <250v rmsp-p , stable with 2.2f ceramic capacitors, dfn-8, ms8 packages ltc3025 300ma, low voltage micropower ldo v in : 0.9v to 5.5v, v out : 0.4v to 3.6v (min), v do = 0.05v, i q = 54a, stable with 1f ceramic capacitors, dfn-6 package ltc3026 1.5a, low input voltage vldo regulator v in : 1.14v to 3.5v (boost enabled), 1.14v to 5.5v (with external 5v), v do = 0.1v, i q = 950a, stable with 10f ceramic capacitors, 10-lead msop and dfn-10 packages lt3150 low v in , fast transient response, vldo controller v in : 1.1v to 10v, v out : 1.21v to 10v, v do = set by external mosfet r ds(on) , 1.4mhz boost converter generates gate drive, ssop16 package

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