ML4903

July 1999 ML4903 High Current Synchronous Buck Controller GENERAL DESCRIPTION The ML4903 high current synchronous buck controller provides high efficiency DC/DC conversion to generate VCCP for processors such as the Pentium® Pro and Pentium II from Intel®. The ML4903 controller, when combined with two external MOSFETs, generates output voltages between 1.8V and 3.5V from a 12V supply. The output voltage is selected via an internal 2 chord 4-bit DAC. In the upper range, the output can be set between 2.1V and 3.5V in 100mV steps. In the lower range, the output can be set between 1.8V and 2.05V in 50mV steps. Output currents in excess of 20A can be attained at efficiencies greater than 80%. The ML4903 can be enabled/disabled via the SHDN pin. While disabled, the output of the regulator is completely isolated from the circuit’s input supply. The ML4903 employs fixed-frequency PWM control combined with a sophisticated control loop enhancement circuit to provide excellent load transient response. FEATURES s Designed to meet Pentium Pro and Pentium II VRM power supply requirements DC regulation to +1% maximum Proprietary circuitry provides transient response of ±5% maximum over a 0A to 14A load range Programmable output voltage (1.8V to 3.5V) is set by an onboard 2 chord 4-bit DAC Synchronous buck topology for maximum power conversion efficiency Fixed frequency operation for easier system integration Integrated anti-shootthrough logic, short circuit protection, shutdown, and UV l...