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unisonic technologies co., ltd U3848/a/b/c linear integrated circuit www.unisonic.com.tw 1 of 13 copyright ? 2005 unisonic technologies co., ltd qw-r103-033.b high performance current mode pwm controllers description the utc U3848/a/b/c is designed to provide several special enhancements to satisfy the needs: power-saving mode for low standby power, over current pr otection (ocp), over voltage protection (ovp), over load protec tion (olp), over temperature protection (otp) etc protection f eatures. ic will be shutdown when either protection arise and can auto-restart. its frequency may be defined by user through resistor r t to external ground. uvlo featuring typical start-up current 20a, and v cc(on) 12.6v, v cc(off) 8.1 7 . lower typical operation current icc 3.7ma at inactive output. the output stage, suitable for dr iving n-channel mosfets, can operate to duty cycles approach 70%. the U3848/a/b/c are fully pin-to-pin compatible with uc3842. but pin r t only connected a resistor to ground to decide switch frequency, and pin fb with an 4k ? pull up resistor to internal refe rence voltage. the U3848/a/b/c also have soft-start function av oiding overshoot, and controlled driver output rise edge time t r for low emi. features * low startup and operation current * user defined switching frequency(norm is 70khz) * max duty cycle 70% * power-saving mode for low power * under voltage lockout with hysteresis * over temperature protection * overload protection * over voltage protection * leading edge blanking * soft start dip-8 sop-8 *pb-free plating product number: U3848l/U3848al/U3848bl/U3848cl ordering information order number normal lead free plating package packing U3848-d08-t U3848l-d08-t dip-8 tube U3848-s08-r U3848l-s08-r sop-8 tape reel U3848-s08-t U3848l-s08-t sop-8 tube U3848a-d08-t U3848al-d08-t dip-8 tube U3848a-s08-r U3848al-s08-r sop-8 tape reel U3848a-s08-t U3848al-s08-t sop-8 tube U3848b-d08-t U3848bl-d08-t dip-8 tube U3848b-s08-r U3848bl-s08-r sop-8 tape reel U3848b-s08-t U3848bl-s08-t sop-8 tube U3848c-d08-t U3848cl-d08-t dip-8 tube U3848c-s08-r U3848cl-s08-r sop-8 tape reel U3848c-s08-t U3848cl-s08-t sop-8 tube
U3848/a/b/c linear integrated circuit unisonic technologies co., ltd 2 of 13 www.unisonic.com.tw qw-r103-033,b ordering information(cont.) U3848l-d08-t (1)packing type (2)package type (3)lead plating (1) r: tape reel, t: tube (2) d08: dip-8, s08: sop-8 (3) l: lead free plating, blank: pb/sn
U3848/a/b/c linear integrated circuit unisonic technologies co., ltd 3 of 13 www.unisonic.com.tw qw-r103-033,b pin configuration gnd out v cc v ref r t cs fb ss 1 2 3 4 8 7 6 5 pin description pin symbol function 1 ss soft-start 2 fb feedback 3 cs controller current sense input 4 r t the resistor controlling switch frequency 5 gnd ground 6 out output to the gate of external power mos 7 v cc supply voltage 8 v ref inter 6.3v reference voltage, connec ted with the filter capacitor
U3848/a/b/c linear integrated circuit unisonic technologies co., ltd 4 of 13 www.unisonic.com.tw qw-r103-033,b block diagram v cc ss fb gnd out latch oscillator s rq q driver current limiting pwm comp soft start power-saving unit ovp olp otp uvlo reference voltage cs v ref r t 8 7 1 2 5 3 6 4 leb explain:olp(over load protection) ovp(over voltage protection) otp(over temperature protection) uvlo(under voltage latch-out leb(led edge blanking) ss(soft start)
U3848/a/b/c linear integrated circuit unisonic technologies co., ltd 5 of 13 www.unisonic.com.tw qw-r103-033,b absolute maximum ratings (ta " 25c, v cc =15v, r t =75k ? , unless otherwise specified) parameter symbol ratings unit supply voltage v cc 26 v input voltage to fb pin v fb -0.3 ~ 6.2 v input voltage to cs pin v cs -0.3 ~ 2.8 v input voltage to rt pin v rt -0.3 ~ 6.2 v junction temperature t j +150 c operating temperature t opr -40 ~ +125 c storage temperature t stg -50 ~ +150 c note absolute maximum ratings are those val ues beyond which the device could be permanently damaged. absolute maximum ratings are stress ratings onl y and functional device operat ion is not implied. operating range parameter symbol ratings unit supply voltage v cc 8.2 ~ 21 v electrical characteristics (ta " 25c, v cc =15v, r t =75k ? , unless otherwise specified) parameter symbol test conditions min typ max unit supply section start up current i str v cc =12.5v 27 45 a off i off v ss = 0, i fb = 0 3.7 5.5 ma supply current with switch on i on v ss = 5v, i fb = 0 4.0 6.0 ma under-voltage lockout section start threshold voltage v thd(on) 11.8 12.6 13.4 v min. operating voltage v cc(min) 7.6 8.1 8.6 v hysteresis v cc(hy) 4.5 v internal voltage reference reference voltage v ref measured at pin v ref 6.1 6.3 6.6 v control section U3848/b(note1) 85 95 105 khz normal v fb = 4v U3848a/c(note2) 61 68 75 khz switch frequency power-saving f (sw) v fb = 1v 17 20 23 khz max d max 65 70 75 % duty cycle min d min v fb < 0.5v 0 % min v min 0.5 v v fb operating level max v max 4.4 v feedback resistor r fb 2.6 3.8 5.0 k ? external resistor for controlling current source of osc r t 75 k ? c ss =0.05uf 6 ms c ss =0.1uf 12 ms soft-start time t ss c ss =1uf 120 ms protection section ovp threshold v (ovp) v ss < 3.5v, v fb > 5v 15.2 16 16.8 v olp threshold v fb(olp) v ss > 5.4v 4.4 4.6 4.9 v otp threshold t (thr) 120 135 150 c ovp disable threshold v ss(deact) v fb > 5v, v cc > 17v 3.7 3.9 4.2 v olp enable threshold v ss(act) v fb > 5v 4.9 5.1 5.4 v spike blanking time t sb 7.2 s current limiting section leb t leb 220 ns
U3848/a/b/c linear integrated circuit unisonic technologies co., ltd 6 of 13 www.unisonic.com.tw qw-r103-033,b electrical characteristics(cont.) parameter symbol test conditions min typ max unit driver output section output voltage low state v ol i source = 200 ma 2.5 v output voltage high state v oh i sink = 200 ma 12.2 v U3848b c l = 1.0 nf 70 150 ns U3848c c l = 1.0 nf 200 300 ns output voltage rise time U3848/a t r c l = 1.0 nf 300 400 ns output voltage fall time t f c l = 1.0 nf 50 90 ns note: 1. r t =65k ? should be connected for U3848/ U3848b. 2. U3848a/c denote U3848a and U3848c.
U3848/a/b/c linear integrated circuit unisonic technologies co., ltd 7 of 13 www.unisonic.com.tw qw-r103-033,b functional description the internal reference voltages and bias circuit work at v cc >12.6v, and shutdown at v cc < 8.1v. (1) soft-start when every ic power on, driver output duty cycle will be decided by voltage v ss on soft-start capacitor and v cs on current sense resistor at beginning. after v ss reach 5.1v, the whole soft-sta rt phase end, and driver duty cycle depend on v fb and v cs . the relation among v ss , v fb and v out as followed fig.3, here soft-start phase t soft-start should more than v out start-up phase t start-up , otherwise, ic will enter false olp protection state. because after the soft-start phase end, if v out remain in lower voltage, v fb more than 4.6v, then ic enter false olp state. furthermore, soft-start phase should end before v cc reach v cc(min) during v cc power on. otherwise, if soft-start phase remain not end before v cc reach v cc(min) during v cc power on, ic will enter auto -restart phase and not set up v out . finally soft-start also set ovp active phase. ovp active phase between v ss =0 and v ss =3.8v, ovp will not be sensed after v ss reach 3.8v.the soft-start phase t ss 6 ms (c ss =0.05uf) t ss = 12 ms (c ss =0.1uf) 120 ms (c ss =1uf) t v out v fb t t driver 4.6v t strat-up v ss t 5.1v t soft -start fig.3 soft-start phase
U3848/a/b/c linear integrated circuit unisonic technologies co., ltd 8 of 13 www.unisonic.com.tw qw-r103-033,b functional description(cont.) (2) switch frequency set the maximum switch frequency decided by an external resistor r t connected between pin rt and ground. then the maximum switch frequency will depend on user requirement. the relation curve between f sw and r t as followed fig.5 under the condition of p out =8w. the equation between f sw and r t as followed (1-2) for U3848a/c, (1-3) for U3848/b: f sw = -0.61*r t +115.7--------------------------(1-2) f sw = -1.1*r t +167.5--------------------------(1-3) after r t connected, switch frequency is also modulated by output power p out during ic operating. so lower switch frequency at lower load, which more and more improve ic?s efficiency at light load. switch frequency is decreased minimum at no load, then the U3848/ b will operate at power-saving mode for lower standby power. the relation curve between f sw and p out as followed fig.4 under the condition of r t =75k ? . the frequency wave of U3848a/c is similar with U3848/b?s, and for them, maximum frequency point is 70khz. 60 10 70 80 50 40 30 20 10 0.6 1.2 1.8 2.4 3 3.6 4.8 6 0 7. 2 12 p out (w) (r t =75k ? ) fsw (khz) 220v 110v 90 fig.4 the relation curve between f sw and output power p out fsw (khz) 60 20 10 55 60 65 70 75 80 85 90 r t (k $ ) (p out =8w) 70 80 50 40 30 95 90 100 fig.5 the relation curve between f sw and r t
U3848/a/b/c linear integrated circuit unisonic technologies co., ltd 9 of 13 www.unisonic.com.tw qw-r103-033,b functional description(cont.) (3) protection section U3848/a/b/c takes on more protection functions such as olp, ovp and otp etc. in case of those failure modes for continual 7.2 s (blanking time), the driver is shut down. at the same time, ic enters auto-restart, v cc power on and driver is reset after v cc power on again. olp after soft-start phase end (v ss >5.1v), ic will shutdown driver if over load state occurs (corresponding to v fb >4.6v) for continual 7.2 s. olp function will not inactive during soft-start phase. olp case as followed fig.6 . the test circuit as followed fig.8 for U3848/a/b/c. vcc v out v fb v ss t t t t 5.1v 4.6v 8.1v 12.6v 7.2s blanking 7.2s blanking ss phase vcc driver on/off v fb v ss t t t t 5.1v 4.6v 8.1v 12.6v 7.2s blanking 7.2s blanking ss phase t restart 16v 3.9v ovp phase fig.6 olp case fig.7 ovp case ovp power supply v cc ?s ovp function are enabled only when v ss <3.9v & v fb >4.6v during soft-start phase. during above condition, driver will be shutdo wn if over voltage state occurs (v cc >16v) for continual 7.2 s. ovp function will not inactive after soft-start phase. olp case as followed fig.7 . the test circuit as followed fig.9 for U3848/a/b/c. otp otp will shut down driver when junction temperature t j of internal circuits is more than threshold 135c for continual 7.2 s.
U3848/a/b/c linear integrated circuit unisonic technologies co., ltd 10 of 13 www.unisonic.com.tw qw-r103-033,b functional description(cont.) c4 2 1 3 4 7 8 6 5 c3 c1 3 utc U3848 / a/b/ c r17 r t ic3 v cc 15 v 5.5 v driver c4 2 1 3 4 7 8 6 5 c3 c13 utc U3848 /a/b/c r17 rt ic3 vcc 3.5 v fig.8 olp test circuit fig.9 ovp test circuit v fb 7.2us 4. 6v v fb driver 7.2 us v cc 16 v v fb (4) driver output section rise edge time of driver output is about 20 0ns for avoiding low emi. when driver output v ol(max) is less than 2.5v with 200ma source current, and v oh(min) is more than 12.2v with 200ma sink current. c4 2 1 3 4 7 8 6 5 c3 c1 3 utc U3848 a/ b/c r17 rt ic3 vcc 15 v isink=200 ma v oh (min ) c4 2 1 3 4 7 8 6 5 c3 c1 3 utc U3848 /a /b/c r17 rt ic3 vcc 15 v isource =200 ma v ol (min) fig.10 driver test circuit with sink current fig.11 driver test circuit with source current v fb v fb (5) external power switch mos transistor because U3848/a/b/c driver output voltage low level threshold is about 2.5v, user may apply power mos transistors with bigger threshold. 4n60 is recommended normally.
U3848/a/b/c linear integrated circuit unisonic technologies co., ltd 11 of 13 www.unisonic.com.tw qw-r103-033,b typical application circuit 5v 3a + gnd ic2 cy1 c2 ic1 rf r2 cd1 rd1 d1 c5 + r5 r4 r3 zd1 r12 l3 tr1 d3 c8 c12 r10 d2 r8 q1 r6 r c4 r17 + c3 c15 r11 c14 ic3 r7 utc U3848 / a/b /c 4 3 2 1 5 6 7 8 th1 cx1 ac in f1 bd1 + c9 fig.12 U3848/a/b/c typical application circuit table1 components reference description for U3848/a/b/c app lication circuit c12 cc 10nf/1000v d3 diode uf1007 r r 470k ? 1/8w c14 cc 100nf/50v ic1 ic pc817 th1 sck-103 c2 cc 33nf/50v ic2 ic tl431clp bd1 r kbp-208 cx1 104/275v ic3 ic U3848/a/b/c rd1 r 10 ? 1/8w c5 ec 1000uf/15v l3 l 1.2uh r12 r 3.3k ? 1/8w c4 cc 22uf/50v q1 mos 4n60 tr1 optional c8 ec 68uf/400v r7 r 68k ? 1/8w rf r 4.7k ? 1/8w c9 ec 1000uf/16v r17 r 1.2 ? /1w 1/8w c15 cc 0.1 f/50v cd1 cc 1nf/1kv r2 r 680 ? 1/8w cy1 cc 4.7nf/250v r3 r adj 1/8w d1 diode c63-004 r4 r 5.6k ? 1/8w d2 diode 1n4148 r5 r 5.6k ? 1/8w note: c5 and c9 are lower esr capacitors.
U3848/a/b/c linear integrated circuit unisonic technologies co., ltd 12 of 13 www.unisonic.com.tw qw-r103-033,b typical characteristics(cont.) 120mv 3.86v 1.64khz 850 hz ch1 max 6.00v ch1 min 460 mv ch1 frequency 785.5hz m 400 0 sa ch1 ? 3.18v 1.00v ch1 60.0 mv 3.30 v 3.29khz 1.70khz ch1 max 5.90v ch1 min 40.0mv ch1 frequency 1.906khz m 200 0 s a ch1 ? 2.68 v 1.00 v ch1 feedback voltage during loadjump from 10% up to 100% load (v dcin =120v) feedback voltage during loadjump from 10% up to 100% load (v dcin =350v) 12.3v 12.3v ch1 max 5.04v ch1 min 1.32v ch1 frequency ----- hz m 10.0ms a ch1 ? 3.16v 2.00v ch1 startup with full load condition at v dcin =120v, vc4 and vout v c4 v out 5.00v ch2 12.3v 12.3v ch1 max 5.04v ch1 min -120 mv ch1 frequency ----- hz m 10.0ms a ch1 ? 3.16v 2.00v ch1 startup with full load condition at v dcin =350v, vc4 and vout v c4 v out 5.00v ch2 120mv 12.3v m 4 .00 ms a ch3 ? 4.96v 2.00v ch1 startup behavior at nominal load condition v dci n =120 v v c4 v ss 2.00v ch2 2.00v ch3 357hz 21.2hz v fb 240 mv 12.0v m 4.00ms a ch3 ? 4.96v 2.00 v ch1 startup behavior at nominal load condition v dcin =350 v v c4 v ss 2.00v ch2 2.00 v ch3 1.79khz 147 hz v fb
U3848/a/b/c linear integrated circuit unisonic technologies co., ltd 13 of 13 www.unisonic.com.tw qw-r103-033,b typical characteristics(cont.) frequency vs. output power 0 20 40 60 80 100 120 frequency (khz) 020 816 12 output power (w) 18 614 10 4 2 vdcin=120v no load input power vs. line voltage (normal mode) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 100 150 200 250 300 dc input voltage(v) input power (w) input power no load (po ut =0w) utc assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all utc products described or contained herein. utc products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. the information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice.

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