Voltage Regulator-Down (VRD) 10.1 Design Guide

VRD Current Support (EXPECTED)
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Design Guide
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5 VRD Current Support (EXPECTED)
System boards supporting LGA775 socket processors must have voltage regulator designs
compliant to electrical and thermal standards defined in Table 2-2. This includes full electrical
support of Iccmax specifications and robust cooling solutions to support defined thermal design
current (VR TDC) indefinitely within the envelope of system operating conditions. This includes
regulator layout, processor fan selection, ambient temperature, chassis configuration, etc. Consult
Table 2-2 and Table 3-1 for processor Vcc and Vtt current limits.
Intel processor VR TDC is the sustained (DC equivalent) current that is to be used for voltage
regulator thermal design with supporting Thermal Monitor circuitry (see Section 9.4). At VR
TDC, components such as switching FETs and inductors reach maximum temperature, heating the
motherboard layers and neighboring components to the pass/fail boundary of thermal limits.
Thermal analysis must include current contributions of both the Vcc and Vtt regulators. In some
instances the PROCESSOR VRD will also power other motherboard components. Under this
condition the VRD will supply current above the VR TDC limits; system designers must budget
this additional current support in final VRD designs while remaining compliant to electrical and
thermal specifications.
To avoid heat related failures, desktop computer systems should be validated for thermal
compliance under the envelope of system operating for desktop systems.
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