Voltage Regulator-Down (VRD) 10.0

Introduction
R
VRD Design Guide 9
Term Description
R
LL
Socket loadline impedance. Defined as the ratio: Voltage droop/current step.
This is the loadline slope defined across specific nodes at the processor-socket
interface.
RSS Root Sum Square. A method of adding statistical variables
PROCHOT# Under thermal monitoring, the VRD asserts this processor input to indicate an
over-temperature condition has occurred. Assertion of this signal places the
processor in a low power state, thereby cooling the voltage regulator.
Slope Loadline resistance. See R
LL
Socket Loadline
Defines the characteristic impedance of the motherboard power delivery circuit
to the node of regulation. Not the same as the processor loadline that is
published in the datasheet, which is defined across the processor Vccsense and
Vsssense pins. In conjunction with high frequency decoupling, design
compliance to this parameter ensures that the processor voltage specifications
are satisfied.
Static Loadline The PWM controlled constant resistance at the defined socket-motherboard
interface reference nodes. Also known as the DC loadline or 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.
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. Defines the voltage regulator’s maximum, 3-σ voltage
variation across temperature, manufacturing variation, and age factors. Must be
guaranteed by design through component selection. Defined at maximum
current and VID levels.
Transient Loadline A metric that is used as a measure of transient noise. The larger the number,
the larger the Vcc noise. The parameter equals dV/di or Vdroop/Istep & is
controlled by switching frequency, decoupling capacitor selection, motherboard
layout parasitics.
Vcc, Icc Processor core voltage and current, defined in the processor datasheet.
VID Voltage Identification: Max voltage at 0 Amps. A code supplied by the processor
that determines the reference output voltage to be delivered to the processor
power pins. VID is defined in the processor datasheet.
VR_TDC Thermal Design Current. It is 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 drive I/O buffer circuits.