Dual Intel Xeon Processor Voltage Regulator Down (VRD) Design Guidelines

Dual Intel
®
Xeon™ Processor Voltage Regulator Down (VRD) Guidelines
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2.6 Efficiency PROPOSED
The efficiency of the VRD should be greater than 80% at maximum output current and across
input voltage range. It should not dissipate more power under any load condition than it does at
maximum output current and maximum input voltage.
2.7 Fault Protection PROPOSED
These are features built into the VRD to prevent damage to itself or the circuits it powers.
2.7.1 Over Voltage Protection
The VRD should provide over-voltage protection (OVP) by including a circuit, separate from the
voltage sense path, capable of shutting off the output drive when the output voltage rises beyond
Vtrip. If practical, the protection circuit should also enable a low-resistance path to ground such
that if the output transistor shorts to input power the output voltage will not rise above Vtrip. A
non-resetable or resetable fuse may be included in the input of the VR for this function. The
response time should be such that the output voltage will not exceed (VID plus 250 mV).
Minimum Vtrip should be the Maximum Vcc specified in Section 2.1 to compensate for remote
sense plus margin to prevent false trips. No combination of input voltage sequences should
falsely trigger an OVP event.
2.7.2 Fuse Protection for Power Input
The power input (12V) should be protected with a fuse rated not greater than 30A, which
sustains all operating and inrush conditions and which “blows” only on catastrophic failure of
the converter.
2.7.3 Overload Protection
The VRD should be capable of withstanding a continuous, abnormally low resistance on the
output without damage or over-stress to the unit. Output current under this condition will be
limited to no more than 150% of the maximum rated output of the VRD. Latching off or hiccup
mode is acceptable during over-current conditions. The VRD should be capable of starting into
a constant current load of 50% of maximum rated load current with maximum load capacitance,
as defined in Section 2.1, without tripping the OCP circuitry.
2.7.4 Reset After Shutdown
If the VRD goes into a shutdown state due to a fault condition on its output (not an internal
failure) it should return to normal operation after the fault has been removed, or after the fault
has been removed and power has been cycled off and on.
3 Design Considerations
Several voltage-regulation component manufacturers have developed reference dual Intel Xeon
processor and Low Voltage Intel Xeon processor VRD designs. System designers are