The UC3844BDG is a high performance fixed frequency Current Mode Controller designed for off-line and DC-to-DC converter applications offering the designer a cost-effective solution with minimal external components. This 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 under-voltage 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%. 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).
Feature
- Trimmed oscillator for precise frequency control
- Oscillator frequency guaranteed at 250kHz
- Current mode operation to 500kHz output switching frequency
- Output dead time adjustable from 50 to 70%
- Automatic feed forward compensation
- Latching PWM for cycle-by-cycle current limiting
- Internally trimmed reference with under-voltage lockout
- High current totem pole output
- Under-voltage lockout with hysteresis
- Low startup and operating current
- 36V Bias and driver voltage
- 30mA Total power supply and Zener current
- +150°C Maximum junction temperature
