Average Current Mode PWM Controller IC
UC1886
UC2886
UC3886
FEATURES
• 10.3V - 20V Operating Range
• Low Offset Voltage Amplifier
• High Bandwidth Current and Voltage
Amplifiers
• Low Offset Current Sense Amplifier
• Undervoltage Lockout
• Trimmed 5 Volt Reference
• Externally Programmable Oscillator
Charge Current
• 1.5A Peak Totem Pole Output
• Available in 16-pin DIL or SOIC
Packages
BLOCK DIAGRAM
DESCRIPTION
The UC3886 family of PWM controller ICs is designed for DC-to-DC con-
verters with average current mode control. It is designed for use in con-
junction with the UC3910 4-bit DAC and Voltage Monitor. The UC3886
drives an external N-channel MOSFET and can be used to power the In-
tel Pentium® Pro and other high-end microprocessors.
The UC3886 in conjunction with the UC3910 converts 5VDC to an adjust-
able output ranging from 2.0V to 3.5V in 100mV steps with 35mV DC sys-
tem accuracy.
The oscillator is programmed by the user’s selection of an external resis-
tor 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 permits the use of a low value current
sense resistor, minimizing power loss. It has inputs and outputs accessi-
ble to allow user-selection of gain-setting resistors, and is internally com-
pensated for a gain of 5 and above. The command voltage input is
buffered and provided for use as the reference for the current sense am-
plifier.
The output of the voltage amplifier (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.
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UDG-95098-2
