Topology 9: Processor Voltage Regulator Sequencing Requirements; Vccvid Regulator Recommendations - Intel Pentium 4 Design Manual

System Bus Routing
5.4.1.12

Topology 9: Processor Voltage Regulator Sequencing Requirements

The Pentium 4 processor with 512KB L2 cache on .13 micron process requires a 1.2 V supply to
the VCCVID pin to support the on-die VID generation circuitry. The current requirements for this
voltage is 30 mA. A linear regulator is recommended to generate this voltage. The on-die VID
generation circuitry also has some power sequencing requirements. Figure 45 shows a block
diagram of a power sequencing implementation. Figure 46 and Figure 47 illustrate timing
diagrams of the power sequencing requirements.
5.4.1.13

VCCVID Regulator Recommendations

• The output of the voltage regulator used to generate VCCVID should be no more than
1.5 inches away from pin AF4 of the processor.
• The trace connecting the voltage regulator output to pin AF4 should be as wide as practical,
but not less than 0.025 inches.
• The trace connecting the voltage regulator output to pin AF4 should have both a 0.1 µF and
1.0 µF capacitor for decoupling. The 1.0 µF capacitor should be located as close as possible
to the output of the voltage regulator. The 0.1 µF capacitor should be located as close as
possible to pin AF4 on the processor.
• If an integrated voltage regulator such as the MIC5248 is used, the voltage input (pin 1)
should be connected to the system board's VCC or 3.3 V rails through a zero ohm resistor.
The input of the voltage regulator should also be decoupled with a 0.1µF capacitor at the pin.
The trace connecting the voltage regular input to the zero resistor should be equal to or greater
than the voltage regulator output trace connected to the processor (i.e., if the connection to the
processor is 0.025 inches than the trace width to the input of the voltage regulator should be
0.025 inches or greater). The voltage regulator power good signal (pin 4) should be connected
to the voltage regulator output (pin 5) through a 10 kΩ resistor.
• During power-on the rising edge of the VCCVID power supply needs to be monotonic.
Examples of an acceptable monotonic and an unacceptable non-monotonic rising edge are
show below for reference.
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Intel Pentium 4 Processor / Intel
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850 Chipset Family Platform Design Guide
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