深圳市尚想信息技术有限公司

UC3844B, UC3845B, UC2844B, UC2845B High Performance Current Mode Controllers The UC3844B, UC3845B 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). Features • Trimmed Oscillator for Precise Frequency Control • Oscillator Frequency Guaranteed at 250 kHz • Current Mode Operation to 500 kHz Output Switching Frequency • Output Deadtime Adjustable from 50% to 70% • Automatic Feed Forward Compensation • Latching PWM for Cycle−By−Cycle Current Limiting • Internally Trimmed Reference with Undervoltage Lockout • High Current Totem Pole Output • Undervoltage Lockout with Hysteresis • Low Startup and Operating Current • These Devices are Pb−Free and are RoHS Compliant • NCV Prefix for Automotive and Other Applications Requiring Unique Site and Control Change Requirements; AEC−Q100 Qualified and PPAP Capable