UTCUC3843A

UTC UC3842A / 3843A LINEAR INTEGRATED CIRCUIT CURRENT MODE PWM CONTROL CIRCUITS DESCRIPTION The UTC 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 SOP-8 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 Vcc Vref 8 Internal Bias 1/2Vref 5V REF S/R 5 GND Vref Good Logic 1/3Vref U.V.L.O CURRENT SENSE COMPARATOR R PWM LATCH S 7 Vcc VFB COMP 2 1 ERROR AMPLIFIER 1V 6 OUTPUT CURRENT SENSE 3 RT/CT 4 OSCILLATOR 5 GND ABSOLUTE MAXIMUM RATINGS(Ta=25°C) PARAMETER Supply Voltage(Low Impedance Source) Supply Voltage(Icc