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UC3844, UC3845, UC2844,UC2845High PerformanceCurrent Mode ControllersThe UC3844, UC3845 series are high performance fixed frequencycurrent mode controllers. They are specifically designed for Off−Lineand DC−to−DC converter applicaTIons offering the designer a costeffecTIve soluTIon with minimal external components. These integratedcircuits feature an oscillator, a temperature compensated reference, highgain error amplifier, current sensing comparator, and a high currenttotem pole output ideally suited for driving a power MOSFET.Also included are protecTIve features consisting of input andreference undervoltage lockouts each with hysteresis, cycle−by−cyclecurrent limiting, a latch for single pulse metering, and a flip−flop whichblanks the output off every other oscillator cycle, allowing output deadtimes to be programmed for 50% to 70%.These devices are available in an 8−pin dual−in−line plastic packageas well as the 14−pin plastic surface mount (SOIC−14). The SOIC−14package has separate power and ground pins for the totem pole outputstage.The UCX844 has UVLO thresholds of 16 V (on) and 10 V (off),ideally suited for off−line converters. The UCX845 is tailored forlower voltage applications having UVLO thresholds of 8.5 V (on) and7.6 V (off).
