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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 COMP VFB ISENSE RT/CT 1 2 3 4 TOP VIEW 8 7 6 5 VREF VCC OUTPUT GROUND D Package COMP 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 compensation · 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 COMP CURRENT SENSE NOTE: Pin numbers in parentheses refer to the D package. (3)2 (1)1 (5)3 + ­ S 2R R R 1V CURRENT SENSE COMPARATOR PWM LATCH 5(8) August 31, 1994 1100 853-0614 13721 Philips Semiconductors Linear Products Product specification Current-mode PWM controller UC3842 ORDERING INFORMATION DESCRIPTION 8-Pin Plastic Dual In-Line Package (DIP) 14-Pin Plastic Small Outline (SO) Package TEMPERATURE RANGE 0 to +70°C 0 to +70°C ORDER CODE UC3842N UC3842D DWG # 0404B 0405B ABSOLUTE MAXIMUM RATINGS1 SYMBOL VCC VCC IOUT PARAMETER Supply voltage (ICC<30mA) Supply voltage (low impedance source) Output current 2, 3 Output energy (capacitive load) Analog inputs (Pin 2, Pin 3) Error amp output sink current PD TSTG TSOLD Power dissipation at TA70°C (derate 12.5mW/°C for TA Lead temperature (soldering, 10sec max) >70°C)2 -65 to +150 300 °C °C Storage temperature range 30 ±1 5 -0.3 to 6.3 10 1 RATING UNIT Self-Limiting V A µJ V mA W NOTES: 1. All voltages are with respect to Pin 5; all currents are positive into the specified terminal. 2. See section in application note on "Power Dissipation Calculation". 3. This parameter is guaranteed, but not 100% tested in production. August 31, 1994 1101 Philips Semiconductors Linear Products Product specification Current