Voltage Regulator-Down (VRD) 10.1 Design Guide

Introduction

Design Guide 11

Term Description

Socket Load Line

Defines the characteristic impedance of the motherboard power delivery circuit

to the node of regulation. Not the same as the processor load line that is

published in the processor datasheet, which is defined across the processor

Vccsense and Vsssense lands. In conjunction with high frequency decoupling,

bulk decoupling, and robust power plane routing, design compliance to this

parameter ensures that the processor voltage specifications are satisfied.

Static Load Line DC resistance at the defined regulation node. Defined as the quotient of voltage

and current (V/I) under steady state conditions. This value is configured by

proper tuning of the PWM controller voltage positioning circuit. In this document,

the static load line is referenced at the socket unless otherwise stated.

Thermal Monitor A feature of the voltage regulator that places the processor in a low power state

when critical VRD temperatures are reached, thereby reducing power and VRD

temperature.

TOB Vcc regulation tolerance band. Defines the voltage regulator’s 3-σ voltage

variation across temperature, manufacturing variation, and age factors. Must be

guaranteed by design through component selection. Defined at processor

maximum current and maximum VID levels.

Transient Load Line Equal to dV/di or Vdroop/Istep and is controlled by switching frequency,

decoupling capacitor selection, motherboard layout parasitics. In this document,

the transient load line is referenced at the socket unless otherwise stated.

Vcc Processor core voltage defined in the processor datasheet.

VID Voltage Identification: A code supplied by the processor that determines the

reference output voltage to be delivered to the processor Vcc lands. At zero

amperes and the tolerance band at + 3-σ, VID is the voltage at the processor.

VR_TDC Voltage Regulator Thermal Design Current. The sustained DC current which the

voltage regulator must support under the system defined cooling solution.

VRD Voltage regulator down. A VR circuit resident on the motherboard.

VRM Voltage regulator module that is socketed to a motherboard.

Vtt Voltage provided to the processor to initiate power up and drive I/O buffer

circuits.