ucc1800/1/2/3/4/5 ucc2800/1/2/3/4/5 ucc3800/1/2/3/4/5 03/99 features 100 m a typical starting supply current 500 m a typical operating supply current operation to 1mhz internal soft start internal fault soft start internal leading-edge blanking of the current sense signal 1 amp totem-pole output 70ns typical response from current-sense to gate drive output 1.5% tolerance voltage reference same pinout as uc3842 and uc3842a description the ucc1800/1/2/3/4/5 family of high-speed, low-power integrated cir- cuits contain all of the control and drive components required for off-line and dc-to-dc fixed frequency current-mode switching power supplies with minimal parts count. these devices have the same pin configuration as the uc1842/3/4/5 family, and also offer the added features of internal full-cycle soft start and internal leading-edge blanking of the current-sense input. the ucc1800/1/2/3/4/5 family offers a variety of package options, tem- perature range options, choice of maximum duty cycle, and choice of crit- ical voltage levels. lower reference parts such as the ucc1803 and ucc1805 fit best into battery operated systems, while the higher refer- ence and the higher uvlo hysteresis of the ucc1802 and ucc1804 make these ideal choices for use in off-line power supplies. the ucc180x series is specified for operation from C55 o c to +125 o c, the ucc280x series is specified for operation from C40 o cto+85 o c, and the ucc380x series is specified for operation from 0 o c to +70 o c. low-power bicmos current-mode pwm part number maximum duty cycle reference voltage turn-on threshold turn-off threshold uccx800 100% 5v 7.2v 6.9v uccx801 50% 5v 9.4v 7.4v uccx802 100% 5v 12.5v 8.3v uccx803 100% 4v 4.1v 3.6v uccx804 50% 5v 12.5v 8.3v uccx805 50% 4v 4.1v 3.6v block diagram udg92009-3
2 ucc1800/1/2/3/4/5 ucc2800/1/2/3/4/5 ucc3800/1/2/3/4/5 dil-8, soic-8 (top view) j or n, d package electrical characteristics unless otherwise stated, these specifications apply for C55 c t a +125c for ucc180x; C40c t a +85c for ucc280x; 0c t a +70c for ucc380x; v cc =10v (note 3); rt=100k from ref to rc; ct=330pf from rc to gnd; 0.1 m f capacitor from v cc to gnd; 0.1 m f capacitor from v ref to gnd. t a =t j . parameter test conditions ucc180x ucc280x ucc380x units min typ max min typ max reference section output voltage t j =+25c, i=0.2ma, uccx800/1/2/4 4.925 5.00 5.075 4.925 5.00 5.075 v t j =+25c, i=0.2ma, uccx803/5 3.94 4.00 4.06 3.94 4.00 4.06 load regulation 0.2m a 3 ucc1800/1/2/3/4/5 ucc2800/1/2/3/4/5 ucc3800/1/2/3/4/5 electrical characteristics unless otherwise stated, these specifications apply for C55 c t a +125c for ucc180x; C40c t a +85c for ucc280x; 0c t a +70c for ucc380x; v cc =10v (note 3); rt=100k from ref to rc; ct=330pf from rc to gnd; 0.1 m f capacitor from v cc to gnd; 0.1 m f capacitor from v ref to gnd. t a =t j . parameter test conditions ucc180x ucc280x ucc380x units error amplifier section input voltage comp=2.5v; uccx800/1/2/4 2.44 2.50 2.56 2.44 2.50 2.56 v comp=2.0v; uccx803/5 1.95 2.0 2.05 1.95 2.0 2.05 input bias current C 11 C 11 m a open loop voltage gain 60 80 60 80 db comp sink current fb=2.7v, comp=1.1v 0.3 3.5 0.4 2.5 ma comp source current fb=1.8v, comp=refC1.2v C0.2 C0.5 C0.8 C0.2 C0.5 C0.8 ma gain bandwidth product (note 9) 2 2 mhz pwm section maximum duty cycle uccx800/2/3 97 99 100 97 99 100 % uccx801/4/5 48 49 50 48 49 50 minimum duty cycle comp=0v 0 0 % current sense section gain (note 5) 1.10 1.65 1.80 1.10 1.65 1.80 v/v maximum input signal comp=5v (note 6) 0.9 1.0 1.1 0.9 1.0 1.1 v input bias current C 200 200 C 200 200 na cs blank time 50 100 150 50 100 150 ns over-current threshold 1.42 1.55 1.68 1.42 1.55 1.68 v comp to cs offset cs=0v 0.45 0.90 1.35 0.45 0.90 1.35 v output section out low level i=20ma, all parts 0.1 0.4 0.1 0.4 v i=200ma, all parts 0.35 0.90 0.35 0.90 v i=50ma, vcc=5v, uccx803/5 0.15 0.40 0.15 0.40 v i=20ma, vcc=0v, all parts 0.7 1.2 0.7 1.2 v out high v sat (v cc -out) i=C20ma, all parts 0.15 0.40 0.15 0.40 v i=C200ma, all parts 1.0 1.9 1.0 1.9 v i=C50ma,vcc=5v, uccx803/5 0.4 0.9 0.4 0.9 v rise time c l =1nf 41 70 41 70 ns fall time c l =1nf 44 75 44 75 ns undervoltage lockout section start threshold (note 8) uccx800 6.6 7.2 7.8 6.6 7.2 7.8 v uccx801 8.6 9.4 10.2 8.6 9.4 10.2 v uccx802/4 11.5 12.5 13.5 11.5 12.5 13.5 v uccx803/5 3.7 4.1 4.5 3.7 4.1 4.5 v stop threshold (note 8) uccx1800 6.3 6.9 7.5 6.3 6.9 7.5 v uccx1801 6.8 7.4 8.0 6.8 7.4 8.0 v uccx802/4 7.6 8.3 9.0 7.6 8.3 9.0 v uccx803/5 3.2 3.6 4.0 3.2 3.6 4.0 v start to stop hysteresis uccx800 0.12 0.3 0.48 0.12 0.3 0.48 v uccx801 1.6 2 2.4 1.6 2 2.4 v uccx802/4 3.5 4.2 5.1 3.5 4.2 5.1 v uccx803/5 0.2 0.5 0.8 0.2 0.5 0.8 v
4 ucc1800/1/2/3/4/5 ucc2800/1/2/3/4/5 ucc3800/1/2/3/4/5 electrical characteristics unless otherwise stated, these specifications apply for C55 c t a +125c for ucc180x; C40c t a +85c for ucc280x; 0c t a +70c for ucc380x; v cc =10v (note 3); rt=100k from ref to rc; ct=330pf from rc to gnd; 0.1 m f capacitor from v cc to gnd; 0.1 m f capacitor from v ref to gnd. t a =t j . parameter test conditions ucc180x ucc280x ucc380x units soft start section comp rise time fb=1.8v, rise from 0.5v to refC1v 4 10 4 10 ms overall section start-up current v cc < start threshold 0.1 0.2 0.1 0.2 ma operating supply current fb=0v, cs=0v 0.5 1.0 0.5 1.0 ma vcc internal zener voltage i cc =10ma (note 8) 12 13.5 15 12 13.5 15 v vcc internal zener voltage minus start threshold voltage uccx802/4 0.5 1.0 0.5 1.0 v note 3: adjust vcc above the start threshold before setting at 10v. note 4: oscillator frequency for the uccx800, uccx802 and uccx803 is the output frequency. oscillator frequency for the uccx801, uccx804 and uccx805 is twice the output frequency. note 5: gain is defined by: a v v vv comp cs cs = d d 008 . . note 6: parameter measured at trip point of latch with pin 2 at 0v. note 7: total variation includes temperature stability and load regulation. note 8: start threshold, stop threshold and zener shunt thresholds track one another. note 9: guaranteed by design. not 100% tested in production. pin descriptions comp: comp is the output of the error amplifier and the input of the pwm comparator. unlike other devices, the error amplifier in the ucc3800 family is a true, low output-impedance, 2mhz operational amplifier. as such, the comp terminal can both source and sink current. however, the error amplifier is internally current limited, so that you can command zero duty cycle by externally forcing comp to gnd. the ucc3800 family features built-in full cycle soft start. soft start is implemented as a clamp on the maximum comp voltage. cs: cs is the input to the current sense comparators. the ucc3800 family has two different current sense comparators: the pwm comparator and an over-current comparator. the ucc3800 family contains digital current sense filter- ing, which disconnects the cs terminal from the current sense comparator during the 100ns interval immediately following the rising edge of the out pin. this digital filter- ing, also called leading-edge blanking, means that in most applications, no analog filtering (rc filter) is re- quired on cs. compared to an external rc filter tech- nique, the leading-edge blanking provides a smaller effective cs to out propagation delay. note, however, that the minimum non-zero on-time of the out signal is directly affected by the leading-edge-blanking and the cs to out propagation delay. the over-current comparator is only intended for fault sensing, and exceeding the over-current threshold will cause a soft start cycle. fb: fb is the inverting input of the error amplifier. for best stability, keep fb lead length as short as possible and fb stray capacitance as small as possible. gnd: gnd is reference ground and power ground for all functions on this part. out: out is the output of a high-current power driver capable of driving the gate of a power mosfet with peak currents exceeding 750ma. out is actively held low when v cc is below the uvlo threshold. the high-current power driver consists of fet output de- vices, which can switch all of the way to gnd and all of thewaytov cc . the output stage also provides a very low impedance to overshoot and undershoot. this means that in many cases, external schottky clamp diodes are not required.
5 ucc1800/1/2/3/4/5 ucc2800/1/2/3/4/5 ucc3800/1/2/3/4/5 rc: rc is the oscillator timing pin. for fixed frequency operation, set timing capacitor charging current by con- necting a resistor from ref to rc. set frequency by con- necting a timing capacitor from rc to gnd. for best performance, keep the timing capacitor lead to gnd as short and direct as possible. if possible, use separate ground traces for the timing capacitor and all other func- tions. the frequency of oscillation can be estimated with the following equations: uccx800/1/2/4: f rc = 15 . uccx803, uccx805: f rc = 10 . where frequency is in hz, resistance is in ohms, and ca- pacitance is in farads. the recommended range of timing resistors is between 10k and 200k and timing capacitor is 100pf to 1000pf. never use a timing resistor less than 10k. to prevent noise problems, bypass vcc to gnd with a ceramic capacitor as close to the vcc pin as possible. an electrolytic capacitor may also be used in addition to the ceramic capacitor. ref: ref is the voltage reference for the error amplifier and also for many other functions on the ic. ref is also used as the logic power supply for high speed switching logic on the ic. when v cc is greater than 1v and less than the uvlo threshold, ref is pulled to ground through a 5k ohm re- sistor. this means that ref can be used as a logic out- put indicating power system status. it is important for reference stability that ref is bypassed to gnd with a ceramic capacitor as close to the pin as possible. an electrolytic capacitor may also be used in addition to the ceramic capacitor. a minimum of 0.1 m f ceramic is re- quired. additional ref bypassing is required for external loads greater than 2.5ma on the reference. to prevent noise problems with high speed switching transients, bypass ref to ground with a ceramic capaci- tor very close to the ic package. vcc: v cc is the power input connection for this device. in normal operation v cc is powered through a current limiting resistor. although quiescent v cc current is very low, total supply current will be higher, depending on out current. total v cc current is the sum of quiescent v cc current and the average out current. knowing the operating frequency and the mosfet gate charge (qg), average out current can be calculated from: iqf out g = . pin descriptions (cont.) figure 1. oscillator. figure 2. error amplifier gain/phase response. the ucc3800/1/2/3/4/5 oscillator generates a sawtooth waveform on rc. the rise time is set by the time constant of r t and c t . the fall time is set by ct and an internal transis- tor on-resistance of approximately 125 w . during the fall time, the output is off and the maximum duty cycle is re- duced below 50% or 100% depending on the part number. larger timing capacitors increase the discharge time and re- duce the maximum duty cycle and frequency.
6 ucc1800/1/2/3/4/5 ucc2800/1/2/3/4/5 ucc3800/1/2/3/4/5 1000 100 10 10 100 1000 oscillator freq. (khz) r(k) t 100pf 200pf 330pf 1nf figure 5. ucc1803/5 oscillator frequency vs. r t and c t. 95 95.5 96 96.5 97 97.5 98 98.5 99 99.5 100 10 100 1000 oscillator frequency (khz) maximum duty cycle (%) c = 100pf t c = 200pf t c = 330pf t figure 6. ucc1800/2/3 maximum duty cycle vs. oscillator frequency. 1000 100 10 10 100 1000 oscillator freq. (khz) r(k) t 100pf 200pf 330pf 1nf figure 4. ucc1800/1/2/4 oscillator frequency vs. r t and c t . 4.00 3.98 3.96 3.94 3.92 3.90 3.88 3.86 3.84 3.82 4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6 v (v) cc v (v) ref figure 3. ucc1803/5 v ref vs. v cc ;i load = 0.5ma. 46.5 47 47.5 48 48.5 49 49.5 50 10 100 1000 oscillator frequency (khz) maximum duty cycle (%) c = 100pf t c = 200pf t c = 330pf t figure 7. ucc1801/4/5 maximum duty cycle vs. oscillator frequency. 0 2 4 6 8 10 12 14 16 0 100 200 300 400 500 600 700 800 900 1000 oscillator frequency (khz) i (ma) cc v = 10v, 1nf cc v = 8v, 1nf cc v = 10v, no load cc v = 8v, no load cc figure 8. ucc1800 i cc vs. oscillator frequency.
7 ucc1800/1/2/3/4/5 ucc2800/1/2/3/4/5 ucc3800/1/2/3/4/5 0 50 100 150 200 250 300 350 400 450 500 100 200 300 400 500 600 700 800 900 1000 c (pf) t dead time (ns) ucc1803/5 ucc1800/1/2/4 figure 9. dead time vs. c t ,r t = 100k. 0 0.6 0.7 0.8 0.9 1.0 1.1 -55-50 -25 0 25 50 75 100 125 temperature (c) comp to cs offset (volts) slope = 1.8mv/ c figure 10. comp to cs offset vs. temperature, cs = 0v. 0 1 2 3 4 5 6 7 8 0 100 200 300 400 500 600 700 800 900 1000 oscillator frequency (khz) i (ma) cc v = 10v, 1nf cc v = 8v, 1nf cc v = 10v, no load cc v = 8v, no load cc figure 8. ucc1805 i cc vs. oscillator frequency.
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