深圳市尚想信息技术有限公司

The UC3844B,  series are high performance fixed frequency

current mode controllers. They are specifically designed for Off−Line

and dc−dc converter applications offering the designer a cost−effective

solution with minimal external components. These integrated circuits

feature an oscillator, a temperature compensated reference, high gain

error amplifier, current sensing comparator, and a high current totem pole

output ideally suited for driving a power MOSFET.

Also included are protective features consisting of input and

reference undervoltage lockouts each with hysteresis, cycle−by−cycle

current limiting, a latch for single pulse metering, and a flip−flop

which blanks the output off every other oscillator cycle, allowing

output deadtimes to be programmed from 50% to 70%.

These devices are available in an 8−pin dual−in−line and surface

mount (SOIC−8) plastic package as well as the 14−pin plastic surface

mount (SOIC−14). The SOIC−14 package has separate power and

ground pins for the totem pole output stage.

The UCX844B has UVLO thresholds of 16V (on) and 10V (off), ideally

suited for off−line converters. The UCX845B is tailored for lower voltage

applications having UVLO thresholds of 8.5V (on) and 7.6V (off)