UC3842A /3843A LINEARINTEGRATED CIRCUIT CURRENT MODE PWM CONTROL CIRCUITS DESCRIPTION SOP-8 The Contek UC3842A/3843A provide the necessary functions to implement off-line or DC to DC fixed frequency current mode , controlled switching circuits with a minimal external part count FEATURES *Low external part count. *Low start up current ( Typical 0.12mA ) *Automatic feed forward compensation *Pulse-by-Pulse current limiting *Under-voltage lockout with hysteresis *Double pulse Suppression *High current totem pole output to drive MOSFET directly *Internally trimmed band gap reference *500kHz operation DIP-8 BLOCK DIAGRAM 7 Vref 8 5V REF 1/2Vref 2 COMP 1 S/R 5 GND Internal Bias VFB Vcc U.V.L.O Vref Good Logic 1/3Vref CURRENT SENSE COMPARATOR 1V ERROR AMPLIFIER 7 R PWM LATCH S 6 Vcc OUTPUT CURRENT SENSE 3 RT/CT 4 5 GND OSCILLATOR Contek ABSOLUTE MAXIMUM RATINGS (Ta=25 PARAMETER Supply Voltage(Low Impedance Source) Supply Voltage(Icc<30mA) Output Current ( Peak ) Output Energy(capacity Load) Analog Inputs(pin 2,3) Error Amplifier Output Sink Current Power Dissipation Lead Temperature( Soldering 10 Sec ) C) SYMBOL VCC Vcc Io VI(ANA) ISINK(EA) PD DIP-8 SOP-8 Tlead VALUE 30 Self Limiting +-1 5 -0.3 ~ +6.3 10 at Tamb<=25 C 1.0 at Tamb<=25 C 0.5 300 Contek Microelectronics Co.,Ltd. CONTEK http://www.contek-ic.com E-mail:sales@contek-ic.com UNIT V V A mJ V mA W W C 1 UC3842A /3843A LINEARINTEGRATED CIRCUIT (continued) PARAMETRER Storage Temperature Note 1: Ta>25 C, PD derated with 8mW/ C. SYMBOL VALUE UNIT Tstg -65 ~ +150 C ELECTRICAL CHARACTERISTICS(0 C <=Ta<=70 specified) PARAMETER Reference Section C,VCC=15V,R T=10kW,CT=3.3nF,unless otherwise SYMBOL TEST CONDITIONS MIN TYP MAX UNIT Output Voltage Line Regulation Load Regulation Temperature Stability Total Output Variation Output Noise Voltage Long Term Stability Output Short Circuit VREF DVREF DVREF Tj=25 C,Io=1mA 12<=VIN<=25V 1<=Io=20mA (Note 2) Line, Load, Temp(note 2) 10Hz<=f<=10kHz,Tj=25 C (note 2) Ta=25 C,1000Hrs(note 2) 4.9 5 6 6 0.2 5.1 20 25 0.4 5.18 V mV mV mV/ C V uV mV mA Initial Accuracy Voltage Stability Temperature Stability Amplitude f Df/DVcc Input Voltage Input Bias Current AVOL Unity Gain Bandwidth PSRR Output Sink Current Output Source Current Vout High Vout Low VI(EA) IBIAS Vosc ISC Oscillator Section Error Amplifier Section Current Sense section Gain Maximum Input signal PSRR Input Bias Current Delay to Output Vosc Isink Isource VOH VOL GV VI(MAX) IBIAS Output Section Output Low Level VOL Output High Level VOH Rise Time Fall Time tR tF Under-Voltage Lockout Output Section Start Threshold VTH(ST) Min. Operating Voltage PWM Section Maximum Duty Cycle VOPR(min) D(MAX) 4.82 -30 50 5 -100 Tj=25 C 12<=Vcc<=25V Tmin<=TA<=Tmax(note 2) Vpin 4 peak to peak 47 52 0.2 5 1.7 57 1 kHz % % V Vpin 1=2.5V 2.42 2.58 -2 2 <=Vo<=4V Tj=25 C (note 2) I2<=Vcc<=25V Vpin 2=2.7V,Vpin 1=1.1V Vpin 2=2.3V,Vpin 1=5V Vpin 2=2.3V, RL=15kW to GND Vpin 2=2.7V,Vpin 1=1.1V 60 0.7 60 2 -0.5 5 2.50 -0.3 90 1 70 6 -0.8 6 0.7 V mA dB MHz dB mA mA V V (note 3,4) Vpin 1=5V( note 3) 12<=Vcc<=25V 2.85 0.9 3.15 1.1 Vpin 3=0 to 2V 3 1 70 -2 150 Isink=20mA Isink=200mA Isource=20mA Isource=200mA Tj=25 C,CL=1nF(note 2) Tj=25 C,CL=1nF(note 2) 13 12 0.1 1.5 13.5 13.5 50 50 0.4 2.2 150 150 14.5 7.8 8.5 16 8.4 10 17.5 9 11.5 V V 7 7.6 8.2 V 95 97 100 % Contek 3842A Contek 3843A After Turn On Contek 3842A Contek 3843A Contek Microelectronics Co.,Ltd. CONTEK 25 -180 http://www.contek-ic.com E-mail:sales@contek-ic.com 1.1 -10 300 V/V V dB mA ns V V V V ns ns 2 UC3842A /3843A PARAMETER LINEARINTEGRATED CIRCUIT SYMBOL Minimum Duty Cycle TEST CONDITIONS D(MIN) Total Standby Current MIN Start-up Current IST Operating Supply Current ICC(opr) Vpin 2=Vpin 3=0V Vcc Zener Voltage Vz Icc=25mA note 2:These parameters, although guaranteed ,are not 100% tested in production. note 3:Parameters measured at trip point of latch with Vpin 2=0. note 4:Gain defined as: A= DVpin 1 DVpin 3 TYP MAX UNIT 0.12 11 34 0.3 17 mA mA V 0 % ; 0<=Vpin3<=0.8V note 5:Adjust Vcc above the start threshold before setting at 15V. OPEN-LOOP LABORATORY TEST FIXTURE 2 3 8 7 Contek A 0.1 mF 100kW Isense Adjust 4.7kW Error Amp Adjust 1 0.1 mF 4.7kW Vref RT 6 Vcc 1kW / 1W OUTPUT 5kW 4 5 CT High peak current associated with capacity loads necessitate careful grounding techniques. Timing and bypass capacitors should be connected close to pin 5 in single point GND. The transistor and 5kW potentio-meter are used to sample the oscillator waveform and apply an adjustable Ramp to Pin 3. UNDER-VOLTAGE LOCKOUT Icc Vcc 7 ON/OFF Command to rest of IC Von=16V Voff=10V >15mA <1mA Von Voff Vcc During Under-Voltage Lockout, the output driver is biased to a high impedance state. Pin 6 should be shunt to GND with a bleeder resistor to prevent activating the power switch with output leakage currents. Contek Microelectronics Co.,Ltd. CONTEK http://www.contek-ic.com E-mail:sales@contek-ic.com 3 UC3842A /3843A LINEARINTEGRATED CIRCUIT ERROR AMPLIFIER CONFIGURATION 2.5V 0.5mA 2 Zi 1 Zf Error amplifier can source or sink up to 0.5mA CURRENT SENSE CIRCUIT Error Amplifier 2R Is R 1 R Current Sense Comparator 3 Rs 1V C 5 Contek Peak current (Is) determined by the formula: Ismax=10V/Rs. A small RC filter be required to suppress switch transients. 8 4 3 0.1 mF SLOPE COMPENSATION CT RT R1 R2 C Isense Rsense A fraction of the oscillator ramp can be resistively summed with the current sense signal to provide slope compensation for converts requiring duty cycles over 50%.Note that capacitor C, forms a filter with R2 to suppress the leading edge switch spikes. Contek Microelectronics Co.,Ltd. CONTEK http://www.contek-ic.com E-mail:sales@contek-ic.com 4 UC3842A /3843A LINEARINTEGRATED CIRCUIT OSCILLATOR SECTION V4 Large RT Small CT 8 INTERNAL CLOCK RT 4 V4 CT 5 Dead time VS C Small RT Large CT T(R T>5kW) 100 INTERNAL CLOCK Timing Resistance Vs Frequency 100 td (ms) CT=1nF RT (k W) CT=2.2nF 10 CT=4.7nF 10 CT=10nF CT=22nF 1 CT=47nF CT=100nF 0.1 1 1 10 CT (nF) 100 SHUTDOWN TECHNIQUES 1kW Shutdown 330W 3 500W Shutdown 1 8 To current Sense resistor 10 2 10 3 10 4 5 10 6 Shutdown Contek UC3842A 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 caused the output of PWM comparator 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 shutdown condition at pins 1 and/or 3 is removed . In one example, an externally latched shut down may be accomplished by adding an SCR which be reset by cycling Vcc below the lower UVLO threshold. At this point the reference turns off allowing the SCR to reset. Contek Microelectronics Co.,Ltd. CONTEK 10 Frequency (Hz) http://www.contek-ic.com E-mail:sales@contek-ic.com 5 UC3842A /3843A LINEARINTEGRATED CIRCUIT TYPICAL PERFORMANCE CHARACTERISTICS 4 100 2 80 0 60 -45 40 -90 20 -135 0 -180 PHASE (Degree) Saturation Voltage (V) Voltage Gain (dB) Vcc=15V Ta=+25 C Ta=-55 C 3 1 0 0.01 0.1 1 10 2 10 10 Output Current (Sourse or Sink Current) (A) Output Saturation 3 10 4 10 5 10 6 10 7 Frequency (Hz) Characteristics Error Amplifier Open-Loop Frequency Response Vref TemperatureDrift IstartTemperatureDrift 550 5.02 Vref (V) 5.01 500 Vcc=15V Io=1mA Vcc=9V 450 Istart (mA) 5.00 4.99 400 4.98 350 4.97 300 4.96 -50 -25 0 25 50 Temperature ( 75 100 125 150 C) 250 -50 -25 0 25 50 Temperature ( 75 100 125 150 C) Icc TemperatureDrift 15 Icc (mA) 14 Vcc=15V Io=1mA 13 12 11 10 9 -50 -25 0 25 50 Temperature ( 75 100 125 150 C) Contek Microelectronics Co.,Ltd. CONTEK http://www.contek-ic.com E-mail:sales@contek-ic.com 6