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UC3842

Philips
Part Number UC3842
Manufacturer Philips
Description Current-mode PWM controller
Published May 23, 2005
Detailed Description Philips Semiconductors Linear Products Product specification Current-mode PWM controller UC3842 DESCRIPTION The UC38...
Datasheet PDF File UC3842 PDF File

UC3842
UC3842

Overview
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 ...


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