lyf Sea SGS-THOMSON UC1842/3/4/5 UC2842/3/4/5 s OPTIMIZED FOR OFF-LINE AND DC TO DC CONVERTERS mn LOW START-UP CURRENT (< 1 mA) AUTOMATIC FEED FORWARD COMPENSA- TION PULSE-BY-PULSE CURRENT LIMITING ENHANCED LOAD RESPONSE CHARACTE- RISTICS UNDER-VOLTAGE LOCKOUT WITH HYSTE- RESIS DOUBLE PULSE SUPPRESSION HIGH CURRENT TOTEM POLE OUTPUT a INTERNALLY TRIMMED BANDGAP REFE- RENCE = 500 KHz OPERATION a LOW Ro ERROR AMP DESCRIPTION The UC 1842/3/4/5 family of control ICs provides the necessary features to implement off-line or DC to DC fixed frequency current mode control schemes with a minimal external parts count. Internally imple- mented circuits include under voltage lockout featu- _CURRENT MODE PWM CONTROLLER tor which also provides current limit control, and a totem pole output stage designed to source or sink high peak current. The output stage, suitable for dri- ving N-Channel MOSFETs, is low in the off-state. Differences between members of this family are the under-voltage lockout thresholds and maximum du- ty cycle ranges. The UC 1842 and UC 1844 have UV- LO thresholds of 16 V (on) and 10 V (off), ideally sui- ted to off-line applications. The corresponding thres- holds for the UC1843 and UC1845 are 8.5 V and 7.9 V. The UC1842 and UC1843 can operate to du- ty cycles approaching 100 %. A range of the zero to < 50 % is obtained by the UC1844 and UC 1845 by the addition of an internal toggle flip flop which blanks the output off every other clock cycle. ring start-up current less than 1 mA, a precision re- Minidip Plastic SO-14 J DIP-14 Plastic ference trimmed for accuracy at the error amp input, and Ceramic logic to insure latched operation, a PWM compara- Le BLOCK DIAGRAM (toggle flip flop used only in UC1844 and UC1845) 7 (12) | A yey UYLO a 16) 8 | = <0 : a Lali |> gica YRee | oo | z. 250 L REF Qu7 Go0o Y R 47: | rT... 1 tt weer . | THO osc. | Lf (06 ---O Errar OUTPUT iP 2k 703) ea O- R W (835 | |_ wis, come O- aL} urgent GRCONG 315) COMPARATOR I oO S-770501 1 CURRENT SENSE September 1988UC1842/3/4/5-UC2842/3/4/5-UC3842/3/4/5 ABSOLUTE MAXIMUM RATINGS * Symbol Parameter Value Unit Vv, Supply Voltage (low impedance source) 30 Vv Vv, Supply Voltage (I, < 30 mA) Self Limiting lo Output Current +1 A Eo Output Energy (capacitive load) 5 pl Analog Inputs (pins 2, 3) 0.3 to 6.3 Vv Error Amplifier Output Sink Current 10 mA Prot Power Dissipation at Tamp < 50 C (minidip, DIP-14) 1 Ww Prot Power Dissipation at Tamn < 25 C (SO-14) 725 mw Tstg Storage Temperature Range - 65 to 150 Cc Th Lead Temperature (soldering 10 s) 300 Cc "All voltages are with respect to pin 5, all currents are positive into the specified terminal. BLOCK DIAGRAM (top view) DIP-14/S0-14. Minidip Plastic and Ceramic. VU comp [1 1] Yrer NC. lz | N.C VY comP ( ' 8 ] Veer Yea {]2 12 ] Vi a) f 2 ? 1 Yi nc. [Je uf} oo sense | 3 6 I ouTPUT ISENSE ( 5 to } OUTPUT RIC, [fe 5 []srouno nc. ffs 9 []enounn 5.7706 ryicy ff? 81) GROUND $-9471 ORDERING NUMBERS PLASTIC CERAMIC TYPE MINIDIP MINIDIP DIP-14 $0-14 UC1842 UC1842J UC1843 UC1843J UC1844 UC1844J UC1845 UC1845J UCG2842 UC2842N UC2842J UC2842B UC2842D UC2843 UC2843N UC2843J UC2843B UC2843D UC2844 UC2844N UC2844J UC2844B UC2844D UC2845 UC2845N UC2845J UC2845B UC2845D UC3842 UC3842N UC3842J UC3842B UC3842D UC3843 UC3843N UC3843J UC3843B UC3843D UC3844 UC3844N UC3844J UC3844B UC3844D UC3845 UC3845N UC3845J UC3845B UC3845D 28 {7 SGS-THOMSON 4 hacromsctnomcs 1106UC1842/3/4/5-UC2842/3/4/5-UC3842/3/4/5 THERMAL DATA Ceramic Plastic DIP-14 S0-14 Minidip Minidip Plastic Rh j-amb | Thermal Resistance Junction-ambient 200 C/W 100 C/W 100 C/W 165 C/W ELECTRICAL CHARACTERISTICS (unless otherwise stated, these specifications apply for 55 <Tamp < 125 CT for UC184X 5 25 < Tamp < 85 C for UC284X 5 0 < Tamp S$ 70 C for UC384X ; Vj = 15 V (Note 5) ; Ry = 10 K; C; = 3.3 nF) SGS-THOMSON S77 MICRORLECTROMICS 7 oye uca84x Symbol Parameter Test Conditions Unit Min. | Typ. | Max. Min. | Typ. | Max. REFERENCE SECTION VREF Output Voltage T, = 25C Ip = 1mA 4.95 | 5.00 | 5.05 | 4.90 | 5.00 | 5.10 Vv A VRee Line Regulation 12V<V,<25V 6 20 6 20 mV A Vaer Load Regulation Tel, 20 mA 6 25 6 25 mv A VaerST | Temperature Stabiltty (Note 2) 0.2 0.4 0.2 0.4 | mvc Total Output Variation Line, Load, Temperature (Note 2) 4.9 5.1 | 4.82 5.18 v @n Ouiput Noise Voltage 10 Hz < fs 10 KHz T, = 25C 50 50 uv (Note 2) Long Term Stability Tamo = 125 C, 1000 Hrs (Note 2) 5 25 5 25 mv Ise Output Short Circuit -30 | -100 | -180 | 90 | -100 | -180 mA OSCILLATOR SECTION fs Initial Accuracy T, = 25 C (Note 6) 47 | 52 | 57 | 47 | 52 | 57 | KHz Voitage Stability 12<V,<25V 0.2 1 0.2 1 % Temperature Stability | Tain < Tamb < Tmax (Note 2) 5 5 %o Va Amplitude Veins Peak to Peak 1.7 1.7 v ERROR AMP SECTION Vo Input Voltage Ver = 2.5V 2.45 | 2.50 | 2.55 | 2.42 | 2.50 | 2.58 Vv Ip Input Bias Current - 4.3] -1 -0.3/-2] pA Avot 26Vos4V 65 | 90 65 | 90 dB B Unity Gain Bandwidth (Note 2) 0.7 1 0.7 1 MHz SVR Supply Voltage 12<V,<25V 60 | 70 60 | 70 dB Rejection lo Output Sink Current Vez =2.7V Vent =1.1V] 2 6 2 6 mA lo Output Source Current | Vpin2 = 2.3 V Vew, =5V |-0.5/-0.8 - 0.5|/- 0.8 mA Vout High Vein2 = 23V: 5 6 5 6 v R, = 15 KQ to Ground Vour Low Venza =2.7V; 07 | 1.4 0.7 | 1.41 Vv R.=15 KQ to Pin 8 3/8 1107UC1842 13/4/5-UC2842/3/4/5-UC3842/3/4/5 ELECTRICAL CHARACTERISTICS (continued) uci184x UC384x Symbol Parameter Test Conditions UC284x Unit Min. | Typ. | Max. | Min. | Typ. [Max. CURRENT SENSE SECTION Gy Gain (Notes 3 & 4) 2.85 3 3.15] 28 3 3.2 VN Va Maximum tnput Signal Vein: = 5 V (Note 3) 0.9 1 11 0.9 1 41 v SVR Supply Voltage Rejection | 12 < Vj < 25 V (Note 3} 7 70 dB lb Input Bias Current -2 1-10 -2 /-10 HA Deiay to Output 150 | 300 150 | 300 ns OUTPUT SECTION Isinx = 20 mA 0.1 0.4 0.1 0.4 lou Output Low Level Vv Isinx = 200 MA 15 | 22 1.5 | 2.2 | =20mA 13 1/135 13 713.5 lon Output High Level SOURCE v lsounce = 200 mA 12 113.5 12 | 13.5 tr Rise Time T,=25C C,_ =1 nF 50 | 150 50 | 150] ns (Note 2) ty Fall Time T,=25C C,_ =1 nF 50 | 150 50 | 150 ns (Note 2) UNDER-VOLTAGE LOCKOUT SECTION X842/4 15 | 16 | 17 [145] 16 |17.5 Start Threshold V X843/5 7.8 | 84 | 9.0 | 7.8 | 84 | 9.0 Min. Operating Voltage | X842/4 9 10 | 11] 85 | 10 | 11.5 V After Turn-on X843/5 7.0 | 76 | 382 | 7.0 | 76 | 82 PWM SECTION Maxi Duty Cyel X842/3 93 | 97 | 100 | 93 | 97 | 100 9 aximam Bay WC?) xe44/5 44 | 48 | 50/45 | 48 | 50] Minimum Duty Cycle 0 0 % TOTAL STANDBY CURRENT ler Start-up Current 0.5 1 0.5 1 mA l, Operating Supply Vpin2 = Vein3 =0 V 11 20 11 20 mA Current Viz Zener Voltage |,=25 mA 34 34 Vv Notes: 2. These parameters, although guaranteed. are not 100% tested in production. 3. Parameter measured at trip point of latch with Vez = 0. 4. Gain detined as : A= 2%" o< Vpns<0.8V A Veins 5. Adjust V. above the start threshold before setting at 15 V. 6. Output frequency equals oscillator frequency for the UC 1842 and UC 1843. Output frequency is one half oscitlator frequency for the UC 1844 and UC 1845. ky SGS-THOMSON MICROELECTROWICSUC1842/3/4/5-UC2842/3/4/5-UC3842/3/4/5 Figure 1 : Error Amp Configuration. Error amp can source or sink up to 0.5mA 5-708 Figure 2 : Under Voltage Lockout. ON/OFF COMMAND tee 10 REST OF IC UC1842 | UCI843 <1?mA rr UC1B 44] UC1B45 vy 16 Ba ON <ImA Veco Yore Yon lov S-770712 During Under-Voltage Lockout, the output driver is {o prevent activating the power switch with extra- biased to sink minor amounts of current. Pin 6 neous leakage currents. should be shunted to ground with a bleeder resistor Figure 3: Current Sense Circuit . CURRENT SENSE COMPAR ATOR $-7708/1 PEAK CURRENT (is) IS DETERMINED BY THE FORMULA 1.0V Ig max = "Rs $s A SMALL RC FILTER MAY BE REQUIRED TO SUPPRESS SWITCH TRANSIENTS. {7 SGS-THOMSON 5/8 If icnoetectaomes 1109UC1842/3/4/5-UC2842/3/4/5-UC3842/3/4/5 Figure 4, Figure 5 : Deadtime vs. Cr (Rt > 5KQ). G- 6108 _-____# ' : | ! : a 1 (us) t i o3 f+ for Rr > 5KQ f= aes 1 2200 470 22 CyinF) Figure 6 : Timing Resistance vs. Frequency. Figure 7 : Output Saturation Characteristics. G- 6106 2 57a? Misat) ' [fr l wi a vate tne a tol, po ee Vis 15 | Tamb = 25C tit toe bye ' t m= Tamps-59C |} : 3 ame -: nh - yi! z -- +- + att 1 SOUPCE savl-VYon) | \ \ aoe pe : SINK sat( yy | | ; * re, . 10? 10? 10* 104 (Hz) 10 10 Te tal Figure 8 : Error Amplifier Open-loop Frequency Response. 6-508 Gv . (dB) | t a0 rN Tot poe o _.} 1 60 + -- -~- 45 oP | os puase | ~% | 20 | t-te a 15 ! GAIN \ o F- Po fe fe T ~~ 4-4 -180 I |i 10 100 1K 10K 100K 1M f( Hz) 68 _ __ [jj SGS-THOMSON Y/ incnomscraomes 1110UC1842/3/4/5-UC2842/3/4/5-UC3842/3/4/5 Figure 9 : Open Loop Test Circuit. O REF 47k 2N2222 100K 0 \ : comp VRer o1 Ka uF 1 ERROR AMP 2 ; AQUUST ep y, - mw 1kO 4 ska UC1B42 0 'sENSE 1 6 HE ; ADJUST SENSE OUTPUT output aka AY Ryicy crounp ' \ 1 \ -__O GROUND cr 4 High peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and bypass capacitors should be connected close Figure 10 : Shutdown Techniques. TO CURRENT SENSE RESISTOR S721 L_ $-7m | to pin 5 in a single point ground. The transistor and 5 KQ potentiometer are used to sample the oscilla- tor waveform and apply an adjustable ramp to pin 3. 1) COMP SHUTOOWN o Shutdown of the UC 1842 can be accomplished by two methods ; either raise pin 3 above 1V or pull pin 1 below a voltage two diode drops above ground. Either method cause the output of the PWM com- parator to be high (refer to block diagram). The PWM latch is reset dominant so that the output will remain low until the next clock cycle after the shut- ky SGS-THOMSON MICROELECTROWICS down condition at pins 1 and/or 3 is removed. In ane example, an externally latched shutdown may be accomplished by adding an SCR which will be reset by cycling V, below the lower UVLO threshold. At this point the reference turns off, allowing the SCR to reset. 78 1111UC1842/3/4/5-UC2842/3/4/5-UC3842/3/4/5 Figure 11 : Off-line Flyback Regulator. ucies, |, aT 220 AT | | Beso 4] c 470pF : _ Terme + _ Power Supply Specifications 1. Input Voltage : 95 VAC to 130 VAC 5. Output Voltage : (50 Hz60 Hz) A.+5V,+5%:1Ato4 A load 2 Line Isolation : 3750 V Ripple voltage : 50 mV P-P Max. ne so B.+12V,+3%:0.1Ato0.3A load 3. Switching Frequency: 40 KHz Ripple voltage : 100 mV P-P Max. 4. Efficiency @ Full Load : 70 % C.~12V,+3%:0.1 Ato 0.3 A load Ripple voltage : 100 mV P-P Max. Figure 12 : Slope Compensation. Vref UC1B42/3 Tsense Isense @) - c ALT FURL Rsense 9063 | SLOPEC: > LIB A fraction of the oscillator ramp can be resistively Note that capacitor. C. forms a filter with Re to su- summed with the current sense signal to provide press the leading edge switch spikes. slope compensation for converters requiring duty cycles over 50 %. S G7 sane _.-_____ 1112