Out in Front: December 7, 1995

Powering Intel’s next-generation Pentium Pro (P6) µ proves to be a nontrivial task due to both the greater-than-30W load and the need to finely adjust input voltage level on a chip-by-chip basis. The AA32A family of switching regulators from Astec America meets Intel’s specs for input power and form factor and offers designers a choice of power-supply rail and mounting configuration.

The Pentium Pro requires approximately 32W at 2.9V for operation and requires a regulator that can make the step from 0.5 to 10A in 350 nsec. The new µ also requires that you set the input voltage with 0.1V accuracy to some voltage between 2.1 and 3.5V. Each Pentium Pro shipped may require a different level in that range, however, for optimal operation. To simplify the voltage-control process, Intel configures four pins on the P6 package after final test to indicate optimal voltage for each µ. (Also see “IC pair provides auto-level-set Pentium Pro power,” EDN, Nov 9, 1995, pg 22.)

The AA32A family can read the four-pin voltage specifier and output the required voltage and power. The family includes four members—two that can operate from a 12V supply rail and two that can operate from a 5V supply. A 12V rail offers more efficient power conversion, but most PC power supplies available today offer the needed power capacity only on the 5V rail.

Intel specifies two mounting configurations for Pentium Pro power regulators. One option uses a pin-and-socket header and connector between motherboard and regulator. The second defines a pinout for a module that you can solder to the motherboard. Astec’s modules, which measure 3.1 X 1.5 X 1 in., cost $30.50 (500) for the solderable modules and $33 (500) with the connector. -- by Maury Wright

Astec America Inc, Carlsbad, CA. (619) 757-1880.