The UC1842A/3A/4A/5A family is an improved version of the UC3842/3/4/5 family, designed for controlling current mode switched mode power supplies. It features low start-up current, trimmed oscillator discharge current, automatic feed forward compensation, pulse-by-pulse current limiting, and enhanced load response characteristics.
The UC1842A/3A/4A/5A, UC2842A/3A/4A/5A and UC3842A/3A/4A/5A families are current‑mode PWM controllers designed for off‑line and DC‑to‑DC converters. They feature low start‑up current (<0.5 mA), trimmed oscillator discharge, automatic feed‑forward compensation, pulse‑by‑pulse current limiting and a 500 kHz operating frequency.
The document provides detailed electrical specifications, package options (DIL‑8, SOIC‑14, PLCC‑20, LCC‑20), mechanical dimensions, and application information such as recommended input voltage ranges, duty‑cycle limits and under‑voltage lockout behavior.
| Start‑up Current | <0.5 mA |
|---|---|
| Oscillator Frequency | 500 kHz |
| Maximum Duty Cycle (UC1842A/3A) | 94‑100 % |
| Operating Supply Voltage (max) | 30 V |
| Output Sink Current | 10 mA |
The start‑up current is guaranteed to be less than 0.5 mA.
They operate at 500 kHz.
The maximum supply voltage is 30 V.
The maximum duty cycle is between 94 % and 100 %.