UCC3880-4

The UCC3880-4/-5/-6 combines high precision reference and voltage monitoring circuitry with average current mode PWM controller circuitry to power Intel Pentium Pro and other high-end microprocessors with a minimum of external components. The UCC3880-x converts 5VDC to an adjustable output, ranging from 2.0VDC to 3.5VDC in 100mV steps with 1% DC system accuracy.

The chip UCC3880-4/-5/-6 includes a precision 5V reference which is capable of sourcing current to an external load. The output voltage of the DAC is derived from this reference, and is programmed directly by Intel's VID pins (Table 1).

The accuracy of the DAC/reference combination is 1.0%. The overvoltage and undervoltage comparators monitor the system output voltage and indicate when it rises above or falls below its programmed value by more than 7.5%. A second overvoltage protection comparator pulls the current amplifier output voltage low to force zero duty cycle when the system output voltage exceeds its designed value by more than 15%. This comparator also terminates the cycle. Undervoltage lockout circuitry assures the correct logic states at the outputs during powerup and powerdown. Grounding the ENABLE pin forces the GATE output low.