UC3886

The UC3886 family of PWM controller ICs is designed for DC-to-DC converters with average current mode control. It is designed for use in conjunction with the UC3910 4-bit DAC and Voltage Monitor. The UC3886 drives an external N-channel MOSFET and can be used to power the Intel Pentium® Pro and other high-end microprocessors.

The UC3886 in conjunction with the UC3910 converts 5VDC to an adjustable output ranging from 2.0V to 3.5V in 100mV steps with 35mV DC system accuracy.

The oscillator of UC3886 is programmed by the user's selection of an external resistor and capacitor, and is designed for 300kHz typical operation. The voltage and current amplifiers have 3.5MHz gain-bandwidth product to satisfy high performance system requirements.

The internal current sense amplifier UC3886 permits the use of a low value current sense resistor, minimizing power loss. It has inputs and outputs accessible to allow user-selection of gain-setting resistors, and is internally compensated for a gain of 5 and above. The command voltage input is buffered and provided for use as the reference for the current sense amplifier. the output of the voltage amplifier UC3886 (input to the current amplifier) is clamped to 1 volt above the command voltage to serve as a current limit. The gate output can be disabled by bringing the CAO/ENBL pin to below 0.8 volts.