UC3842 Datasheet | Philips Semiconductors

Philips Semiconductors Linear Products Product specification Current-mode PWM controller UC3842 DESCRIPTION The UC3842 is available in an 8-Pin mini-DIP the necessary Features to implement off-line, fixed-frequency current-mode control schemes with a minimal external parts count. This technique results in improved line regulation, enhanced load response characteristics, and a simpler, easier to design control loop. Topological advantages include inherent pulse-by-pulse current limiting. Protection circuitry includes built-in undervoltage lock-out and current limiting. Other Features include fully-latched operation, a 1% trimmed bandgap reference, and start-up current less than 1mA. These devices feature a totem-pole output designed to source and sink high peak current from a capacitive load, such as the gate of a power MOSFET. Consistent with N-channel power devices, the output is low in the OFF-state. PIN CONFIGURATIONS N Package P VFB ISENSE RT/CT 1 2 3 4 TOP VIEW 8 7 6 5 VREF VCC OUTPUT GROUND D Package P 1 2 3 4 5 6 7 TOP VIEW 14 VREF 13 NC 12 V CC 11 V C 10 OUTPUT 9 8 GROUND POWER GROUND Features NC VFB NC ISENSE NC RT/CT - Low start-up current (≤1mA) - Automatic feed-forward pensation - Pulse-by-pulse current limiting - Enhanced load response characteristics - Undervoltage lock-out with hysteresis - Double pulse suppression - High current totem-pole output - Internally-trimmed bandgap reference - 400kHz operation, guaranteed min BLOCK DIAGRAM APPLICATIONS - Off-line switched mode power supplies - DC-to-DC converters UC3842 7(11) (12)7 VCC 34V (9)5 GND 16V 2.5V INTERNAL BIAS 6V UVLO S/R 5V REF V 8(14) REF 5.0V 50mA (7)4 RT/CT OSC 6(10) OUTPUT ERROR AMP VFB P CURRENT SENSE NOTE: Pin numbers in parentheses refer to the D package. (3)2 (1)1...