1 features externally set delay for reset 60v load dump protection internal thermal overload protection 3% output accuracy active reset noise immunity on chip emc hardening protection incorporated externally set current limit externally set overvoltage shutdown package options 8 lead so narrow cs8128 5v linear controller/driver 1 v in 2 3 4 sense delay v out pwr gnd shutdown ref gnd 8 7 6 5 reset cs8128 description block diagram december, 2001 - rev. 7 on semiconductor 2000 south county trail, east greenwich, ri 02818 tel: (401)885?600 fax: (401)885?786 n. american technical support: 800-282-9855 web site: www.cherry?emi.com archive device not recommended for new design the cs8128 contains all the necessary control circuitry to implement a 5v lin- ear regulator. an external pass device is used to produce superior performance compared to conventional monolithic regulators. the cs8128 with a tip42 pnp transistor typically provides a 100mv dropout voltage at 500ma, increasing to 350mv at 3a. quiescent current at 500ma is only 5ma. monolithic regulators cannot approach these figures because their power tran- sistors do not provide the high beta and excellent saturation characteristics at high currents. the cs8128 is compatible with a wide variety of external transis- tors, allowing flexibility for thermal, space, and cost management. the cs8128 includes thermal shutdown and externally programmable current limit and over-voltage shutdown, mak- ing it suitable for use in automotive and switching regulator post regulator appli- cations. an optional external rc filter added to the cs8128 supply lead pro- vides emc hardening in addition to the on-chip emc hardening. the sense lead allows remote sensing of the output voltage for improved regulation. an active microprocessor reset func- tion is included on-chip with externally programmable delay time. during power-up, or after detection of any error in the regulated output, the reset lead will remain in the low state for the dura- tion of the delay. types of errors include short circuit, low input voltage, over- voltage shutdown, thermal shutdown, or others that cause the output to become unregulated. this function is independent of the input voltage and will function correctly with an output voltage as low as 1v. hysteresis is included in both the reset and delay comparators for noise immunity and to prevent oscillations. a latching dis- charge circuit is used to discharge the delay capacitor, even when triggered by a relatively short fault condition. this circuit improves upon the commonly used scr structure by providing improved noise immunity and full capacitor discharge (0.2v typ). + - - + + ic reference gnd pre- regulator ic power gnd regulated supply for circuit bias 10 a delay current delay ref gnd pwr gnd thermal shutdown bandgap reference reset comparator latching discharge q s r v dis delay comparator 1.25v error amp shutdown v out v in sense - over voltage shutdown - + reset
2 note 1: dependent on characteristics of external transistor. electrical characteristics: t a = -40? to +125?, t j = -40? to +150?, v in = 6 to 26v, i out = 5 to 500ma, per test circuit (unless otherwise noted) parameter test conditions min typ max unit absolute maximum ratings power dissipation.............................................................................................................. ...............................internally limited input voltage .................................................................................................................. ................................................?.3v, 26v transient input voltage ........................................................................................................ ....................................................60v output current ................................................................................................................. ..............................externally limited esd susceptibility (human body model)........................................................................................... ...................................2kv junction temperature ........................................................................................................... .................................?5? to 150? storage temperature............................................................................................................ ..................................?5? to 150? lead temperature soldering wave solder (through hole styles only) .....................................................................................10 s ec. max, 260? peak reflow (smd styles only) ......................................................................................60 sec. max above 183?, 230? peak cs8128 c delay x v dtc i charge note 2: delay time = = c delay x 3.5 x 10 5 (typical) output stage (v out ) output voltage 4.85 5.00 5.15 v dropout voltage i out = 500ma, note 1 0.1 0.6 v supply current i q i out 10ma 4 8 ma i out 500ma 5 15 i out 3a, note 1 30 line regulation 6v v in 26v, i out = 5ma 12 50 mv load regulation 5v i out 500ma, v in = 14v 2 50 mv ripple rejection f = 120hz, 7v v in 17v, 60 70 db i out = 350ma v in overvoltage shutdown 32 40 v drive current v sense = 0v 25 250 ma and delay functions delay charge current, i charge v delay = 2v 5 10 15 a threshold v rth v out increasing 4.65 4.90 v out - 0.10 v v rtl v out decreasing 4.50 4.70 v out - 0.15 v hysteresis v rh 150 200 250 mv delay threshold v dtc charge 3.25 3.50 3.75 v v dtd discharge 2.80 3.00 3.40 v delay hysteresis, v dh v dtc - v dtd 200 400 800 mv output voltage low 1v < v out < v rtl , 3k ? to v out 0.4 v output v d > v dtc , v out >v rth 10 a leakage current delay capacitor (v dis ) discharge latched ?n? 0.2 0.5 v discharge voltage v out > v rth delay time c delay = 0.1 f, note 2 16 32 48 ms reset reset reset reset reset
3 typical performance characteristics (per test circuit) 5.02 5.01 5 4.99 4.98 4.97 4.96 4.95 -40 -20 0 20 40 60 80 100120 140150 junction temperature ( c) v out (v) 5.00v @ 25 c i out =500ma 0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 reset output current (ma) reset output voltage (mv) v in = 5v 0 5 10 15 20 25 30 35 40 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 012345678910 v in (v) i q (ma) i out = 3a r out = 47 ? i out = 0.5a r out = 330 ? i q vs. v in reset voltage vs. output current temperature performance of v out 012345678910 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 v in (v) v out (v) i out =0.5a i out = 3a 0 0.5 1.0 1.5 2.0 2.5 3.0 0 50 100 150 200 250 300 350 400 i out (amps) dropout voltage (mv) r out = 47 ? 25 c 20 18 16 14 12 10 8 6 4 2 0 0 0.5 1.0 1.5 2.0 2.5 3.0 i out (amps) load regulation (mv) v in =14v 25 c load regulation vs. i out dropout voltage vs. i out v out vs. v in 6v v in - 26v i out (amps) line regulation (mv) 20 0 15 10 5 0 0.5 1.0 1.5 2.0 2.5 3.0 25 c 40 35 30 25 20 15 10 5 0 0 0.5 1.0 1.5 2.0 2.5 3.0 v in =14v i out (amps) i q (ma) 25 c 10 100 1k 10k 100k frequency (hz) 1m 10m 100m 0 10 20 30 40 50 60 70 80 v in / v out (db) i out =250ma 25 c ripple rejection i q vs. i out line regulation vs. i out package lead description package lead # lead symbol function cs8128 8 lead so narrow 1v in unregulated supply voltage to the ic. 2 sense kelvin connection which allows remote sensing of output volt- age for improved regulation. 3 delay timing cap for function 4 cmos/ttl compatible open collector output. goes low whenever v out drops below 6% of it's typical value. 5 ref gnd ground connection 6 shutdown overvoltage shutdown control input. 7 pwr gnd ground connection 8v out supplies base current to pnp pass transistor or threshold volt- age to fet pass transistor. reset reset reset
the cs8128 function is very precise, has hysteresis on both the and delay comparators, a latching delay capacitor discharge circuit, and operation down to 1v. the reset circuit output is an open collector type with on and off parameters as specified. the reset output npn transistor is controlled by the low voltage inhibit and reset delay circuits (see block diagram). this circuit monitors output voltage, and when output voltage is below v rtl , causes the reset output transistor to be in the on (saturation) state. when the output voltage is above v rth , this circuit permits the reset output transistor to go into the off state if allowed by the reset delay cir- cuit. this circuit provides a programmable (by external capaci- tor) delay on the output lead. the delay lead pro- vides source current to the external delay capacitor only when the low voltage inhibit circuit indicates that output voltage is above v rth . otherwise, the delay lead sinks current to ground (used to discharge the delay capacitor). the discharge current is latched on when the output volt- age falls below v rtl . the delay capacitor is fully dis- charged anytime the output voltage falls out of regulation, even for a short period of time. this feature ensures a con- trolled pulse is generated following the detection of an error condition. the circuit allows the out- put transistor to go to the off (open) state only when the voltage on the delay lead is higher than v dtc . reset reset reset reset delay circuit low voltage inhibit circuit reset reset 4 cs8128 reset v rh v out v rth v rt l v rl delay v dtc v dtd v dh t d v dis (3) (1) (2) (2) reset circuit waveform reset circuit functional description (1) = no delay capacitor (2) = with delay capacitor (3) = max: reset voltage (1.0v)
5 v in sense delay ref gnd shutdown pwr gnd v out r rst 4.7 k ? c delay 0.022 f c o 10 f v out (5v) v in r in 220 ? c in 0.022 f tip42b r out 220 ? gnd cs8128 reset r bias 560 ? reset test circuit cs8128 application information the cs8128 includes an over voltage shutdown circuit which is activated by connecting the shutdown lead to the input. shutdown typically occurs at 36v. grounding the shutdown lead disables this function. with the overvoltage shutdown disabled, the cs8128 will continue to regulate during an overvoltage condition. the cs8128 includes a thermal shutdown circuit that dis- ables the output when junction temperature exceeds approximately 180?. this is a self-protection feature designed to protect the cs8128. the thermal shutdown cir- cuit does not monitor the temperature of the pass transis- tor, which will probably be much hotter. to optimize ther- mal shutdown, board design should minimize the differ- ence in temperature of the cs8128 and the pass device. external pass device - select a pass device that will deliv- er the desired output current, withstand the maximum expected input voltage, and dissipate the resulting power. the cs8128 is compatible with a wide variety of bipolar and fet pass transistors. output capacitor - an output capacitor is required for sta- bility in most applications. though a 10 f capacitor should be sufficient, regulator stability is dependent on the characteristics of the pass transistor. capacitor effective series resistance (esr) also factors in system stability. some bench work may be required to determine the capacitor characteristics required for use in a particular application. bias resistor - this resistor provides bias current for the cs8128 output stage, and prevents the pass device from ?eaking? it also speeds the turn-off of the pass device during an overvoltage transient. for proper operation over temperature, the recommended value is 560 ? , although it may be increased or decreased for a particular application. r out resistor - this resistor controls the drive current available to the pass transistor. it also determines regula- tor start-up current and short circuit current limit. for bipolar pass transistors, it can be selected by use of the fol- lowing formulae: r out = x q1 *** *** q1 = pass transistor minimum @ maximum output current. typical start-up current and current limit can be calculat- ed as follows: i start + 5ma i limit x q1 @ current limit for example, if the minimum input voltage is 6v, maxi- mum output current is 1amp, and minimum transistor @ 1amp is 60, then r out can be calculated as follows: r out x 60 = 300 ? i start + 5ma = 18.3ma with v in = 14v, and a pass transistor of 40 @ current limit: i limit x 40 = 1.7amps 14v ?1v 300 ? 4v 300 ? 6v ?1v 1amp v in ?1v r out 4v r out v in(min) ?1v i out(max) external component selection thermal shutdown overvoltage shutdown
part number description cs8128yd8 8 lead so narrow cs8128ydr8 8 lead so narrow (tape & reel) d lead count metric english max min max min 8 lead so narrow 5.00 4.80 .197 .189 6 thermal data 8 lead so narrow r jc typ 45 c/w r ja typ 165 ?/w package specification package dimensions in mm (inches) ordering information package thermal data cs8128 on semiconductor and the on logo are trademarks of semiconductor components industries, llc (scillc). on semiconductor reserves the right to make changes without further notice to any products herein. for additional infor- mation and the latest available information, please contact your local on semiconductor representative. ?semiconductor components industries, llc, 2000 archive device not recommended for new design surface mount narrow body (d); 150 mil wide 1.27 (.050) bsc 0.51 (.020) 0.33 (.013) 6.20 (.244) 5.80 (.228) 4.00 (.157) 3.80 (.150) 1.57 (.062) 1.37 (.054) d 0.25 (0.10) 0.10 (.004) 1.75 (.069) max 1.27 (.050) 0.40 (.016) ref: jedec ms-012 0.25 (.010) 0.19 (.008)
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