Power for Pentium? Processors; Meeting VRE Requirements

　　Introduction

　　Providing power for the Pentium? microprocessor family is not a trivial task by any means. In an effort to simplify this task we have developed a new switching regulator control circuit and a new linear regulator to address the needs of these processors. Considerable time has been spent developing an optimized decoupling network. Here are several circuits using the new LTC? 1266 synchronous buck regulator control chip and the LT? 1584 linear regulator to provide power for Pentium processors and Pentium VRE processors. The Pentium processor has a supply requirement of 3.3V ±5%. The Pentium VRE processor requires 3.500V ±100mV.

　　The circuits shown here are designed to supply worstcase specification voltages to the Pentium VRE processor over line， load， transient and temperature. At first glance it may seem that simpler circuits， such as 3-terminal regulators， can provide this function. Worst-case analysis shows the margin to be too small （or negative） to ensure adequate operation over a wide production range. The combination of tight tolerance， tight transient response and large production volumes requires designs with adequate margin to ensure proper operation over the product’s life. Failure of this circuit to provide proper power supply voltages can result in intermittent machine lock-up， freezes or erratic operation. There are no self-test software routines which can exercise the power supply over the entire expected combination of load， line and temperature conditions.