features complete control for a high current, low dropout, linear regulator fixed 5v or adjustable output voltage accurate 2.5a current limiting with foldback internal current sense resistor remote sense for improved load regulation external shutdown under-voltage lockout and reverse voltage protection thermal shutdown protection 8 pin mini-dip package (surface mount also available) description the uc1835/6 families of linear controllers are optimized for the de- sign of low cost, low dropout, linear regulators. using an external pass element, dropout voltages of less than 0.5v are readily obtained. these devices contain a high gain error amplifier, a 250ma output driver, and a precision reference. in addition, current sense with fold- back provides for a 2.5a peak output current dropping to less than 0.5a at short circuit. these devices are available in fixed, 5v, (uc1835), or adjustable, (uc1836), versions. in the fixed 5 volt version, the only external parts required are an external pass element, an output capacitor, and a com- pensation capacitor. on the adjustable version the output voltage can be set anywhere from 2.5v to 35v with two external resistors. additional features of these devices include under-voltage lockout for predictable start-up, thermal shutdown and short circuit current limiting to protect the driver device. on the fixed voltage version, a reverse voltage comparator minimizes reverse load current in the event of a negative input to output differential. high efficiency regulator controller block diagram note: pin numbers refer to 8-pin dil package uc1835 uc1836 uc2835 uc2836 uc3835 uc3836 8/94
uc1835 uc1836 uc2835 uc2836 uc3835 uc3836 soic-16 (top view) dw package connection diagrams package pin function function pin n/c 1 +v in 2 +v in 3 n/c 4 compensation/ shutdown 5 n/c 6 ground 7 n/c 8 n/c 9 driver source 10 n/c 11 v out sense 12 n/c 13 n/c 14 driver sink 15 n/c 16 current limit (-) 17 n/c 18 sense resistor out 19 sense resistor out 20 dil-8, soic-8 (top view) n or j package, d package plcc-20, lcc-20 (top view) q, l packages input supply voltage (+v in ) . . . . . . . . . . . . . . . . C1.0v to + 40v driver output current (sink or source) . . . . . . . . . . . . . 600ma driver source to sink voltage . . . . . . . . . . . . . . . . . . . . . + 40v maximum current through sense resistor. . . . . . . . . . . . . . 4a v out sense input voltage . . . . . . . . . . . . . . . . . . C.3v to + 40v power dissipation at t a = 25c (note 2) . . . . . . . . . . . 1000mw power dissipation at t c = 25c (note 2) . . . . . . . . . . . 2000mw operating junction temperature . . . . . . . . . . . -55c to +150c storage temperature . . . . . . . . . . . . . . . . . . . . -65c to +150c lead temperature (soldering, 10 seconds) . . . . . . . . . . 300c note 1: voltages are referenced to ground, (pin 3). currents are positive into, negative out of, the specified terminals. consult packaging section of databook for thermal considerations and limitations of packages. electrical characteristics: unless otherwise stated, specifications hold for t a = 0c to + 70c for the uc3835/6, C25c to + 85c for the uc2835/6, and C55c to +125c for the uc1835/6, +v in = 6v, driver source= 0v, driver sink = 5v, t a = t j . parameter test conditions min. typ. max. units input supply supply current +v in = 6v 2.75 4.0 ma +v in = 40v 3.75 6.0 ma uvlo threshold +v in low to high, v out sense = 0v 3.9 4.4 4.9 v threshold hysteresis 0.1 0.35 v reverse current +v in = -1.0v, driver sink open 6.0 20 ma regulating voltage and error amplifier (uc1835 family only) regulating level at v out sense (v reg ) driver current = 10ma, t j = 25c 4.94 5.0 5.06 v over temperature 4.9 5.1 v line regulation +v in = 5.2v + 35v 15 40 mv load regulation driver current = 0 to 250ma 6.0 25 mv bias current at v out sense v out sense = 5.0v 75 125 210 m a error amp transconductance 100 m a at compensation/shutdown pin 0.8 1.3 2.0 ms maximum compensation output current sink or source, driver source open 90 200 260 m a absolute maximum ratings (note 1) 2
uc1835 uc1836 uc2835 uc2836 uc3835 uc3836 parameter test conditions min. typ. max. units regulating voltage and error amplifier (uc1836 family only) regulating level at v out sense (v reg ) driver current = 10ma, t j = 25c 2.47 2.5 2.53 v over temperature 2.45 2.55 v line regulation +v in = 5.2v to 35v 6.0 20 mv load regulation driver current = 0 to 250ma 3.0 15 mv bias current at v out sense v out sense =2.5v -1.0 -0.2 m a error amp transconductance 100 m a at compensation/shutdown pin 0.8 1.3 2.0 ms maximum compensation output current sink or source, driver source open 90 200 260 m a driver maximum current 250 500 ma saturation voltage driver current = 250ma, driver sink 2.0 2.8 v pull-up current at driver sink compensation/shutdown=0.45v 140 250 300 m a driver sink leakage in uvlo 10 m a in reverse voltage (uc1835 family only) 10 m a thermal shutdown 165 c foldback current limit current limit levels at sense resistor out v out sense = (0.99) v reg 2.2 2.5 2.8 a v out sense = (0.5) v reg 1.3 1.5 1.7 a v out sense = 0v 0.25 0.4 0.55 a current limit amp tansconductance 100 m a at compensation/shutdown, v out sense = (0.9) v reg 12 24 42 ms limiting voltage at current limit (-) (note 2) v out sense = (0.9) v reg volts below +v in , t j = 25c 80 100 140 mv sense resistor value (note 3) v out sense = (0.9) v reg, i out = i a , t j = 25c 40 m w note 2: this voltage has a positive temperature coefficient of approximately 3500ppm/c. note 3: this resistance has a positive temperature coefficient of approximately 3500ppm/c. the total resistance from pin 1 to pin 8 will include an additional 60 to 100m w of package resistance. electrical characteristics: unless otherwise stated, specifications hold for t a = 0c to + 70c for the uc3835/6, C25c to + 85c for the uc2835/6, and C55c to +125c for the uc1835/6, +v in = 6v, driver source= 0v, driver sink = 5v, t a = t j . uc 1835 - typical configurations for a 2a, low dropout 5v regulator uc1836 - typical configuration for a 2a, low dropout adjustable regulator note 4: suggested pass devices are tip 32b. (dropout voltage 0.75v) or, d45h, (dropout voltage 0.5v), or equivalents. application and operation information 3
uc1835 uc1836 uc2835 uc2836 uc3835 uc3836 equations: r 1 = 0.100 v/i out (max) r 2 = (v out - 2.5v/1ma) r 3 = ((v in - v be - v sat )*beta(min))/i out (max) uc3835/36 typical applications low current application using the uc3836 internal drive transistor typical output current vs v in and v out of the uc3836 internal drive transistor for p diss = 0.5w (approx.) high current application using drive transistor q 2 to increase q 1 base drive and reduce uc3836 power dissipation parallel pass transistors can be added for high current or high power dissipation applications unitrode integrated circuits 7 continental bl vd. merrimack, nh 03054 tel. (603) 424-2410 fax 603-424-3460 application and operation information (cont.) uc1835/6 foldback current limiting 4
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