Design Guide
165
Platform Power Delivery Guidelines
The voltage regulator should be capable of accepting a 5-bit VID code, which is used to indicate
the maximum voltage allowed by the individual processor unit. The VID values are documented in
the
Intel
®
Xeon™ Processor with 512 KB L2 Cache at 1.80 GHz, 2 GHz, and 2.20 GHz Datasheet
.
12.2.4.1
Input Voltages and Currents
To minimize power distribution losses, the recommended main power source for the VR is 12 V
+5%,
–
8%. This voltage is supplied by a conventional server power supply such as the SSI
EPS-12V. The system designer should ensure that the input circuit of the VR incorporates the
necessary local bulk bypassing on the 12 V rail.
12.2.4.2
Power Good Output (PWRGD)
The VR should provide an open collector or equivalent Power Good signal consistent with TTL
DC levels. This signal should transition to the open (>100 k
Ω
) state within 10 ms of the output
voltage stabilizing within the specified processor operating voltage range. The signal should be in
the low impedance (to ground) state whenever VCC_CPU is outside of the required range, and
should be in the open state whenever VCC_CPU is within its specified range. At power up, the
PWRGD signal must remain in the low-impedance state until the output voltage has stabilized
within the required tolerance.
The minimum voltage at which PWRGD is asserted should be the minimum VCC_CPU specified
in the
Intel
®
Xeon™ Processor with 512 KB L2 Cache at 1.80 GHz, 2 GHz, and 2.20 GHz
Datasheet
, minus margin to prevent false de-assertion, but at least 95% of (VID minus 125 mV).
The maximum voltage at which PWRGD is asserted should be the VID set-point voltage, plus
margin to prevent false de-assertion, but must be no greater than (VID plus 250 mV).
This PWRGD should be capable of sinking up to 4 mA while maintaining a voltage of 0.4 V or
lower. When the output is in the open state, it should be capable of withstanding up to 5.5 V. Latch-
up or damage cannot occur if the pull-up voltage on the system board is present with no +12 V
input present. VR Power Good should remain low if the VR is disabled by the Output Enable
(OUTEN) pin.
Figure 12-2. Power Distribution Block Diagrams for Two-Way System Motherboard
Power
Supply
Voltage Regulator M odule 1
Voltage Regulator M odule 2
Processor 0
Processor 1
Power
Supply
Voltage Regulator
Down
Processor 0
Processor 1
Summary of Contents for Xeon
Page 24: ...Introduction 24 Design Guide This page is intentionally left blank ...
Page 30: ...Component Quadrant Layout 30 Design Guide This page is intentionally left blank ...
Page 52: ...Platform Clock Routing Guidelines 52 Design Guide This page is intentionally left blank ...
Page 66: ...System Bus Routing Guidelines 66 Design Guide This page is intentionally left blank ...
Page 118: ...Intel 82870P2 P64H2 118 Design Guide This page is intentionally left blank ...
Page 146: ...I O Controller Hub 146 Design Guide This page is intentionally left blank ...
Page 148: ...Debug Port 148 Design Guide This page is intentionally left blank ...
Page 210: ...Schematic Checklist 210 Design Guide This page is intentionally left blank ...
Page 220: ...Layout Checklist 220 Design Guide This page is intentionally left blank ...
Page 222: ...Schematics 222 Design Guide This page is intentionally left blank ...