VRM 9.0 DC-DC Converter Design Guidelines

1 Electrical Specifications

1.1 Output Requirements

1.1.1 Voltage and Current REQUIRED

The VRM 9.0 Voltage Regulator Module is a DC-DC converter that supplies the required voltage

and current to a single processor as shown in Table 1. The maximum voltage is determined by

the five-bit VID code provided to the VRM, as described in Section 1.3.2. The specifications in

Table 1 are for the VRM only. The computer system board must supply additional decoupling

capacitance and sufficient plane area to carry the high DC currents. It is desirable that a single

model of the VRM be able to support all processor types, if this does not significantly affect

VRM cost and availability, so that field upgrades of processors will not require a new VRM.

1.1.2 Output Voltage Tolerance REQUIRED

The voltage measured at the VRM connector pins on the system board must be within the range

shown in Table 1, except during input voltage turn-on and turn-off. See Section 1.1.5 for

turn-on and turn-off tolerance.

Voltage tolerance includes:

− Initial DC output voltage set-point error

− Component aging effects

− Output ripple and noise

− Full ambient temperature range and warm up specified in Section 3.1.

− Both static operation and dynamic output load changes from minimum-to-maximum or

maximum-to-minimum loads specified in the tables above.

Output voltage tolerances increase with output current levels to compensate for the increasing

voltage drops in the power distribution path. Table 1 shows the relationship of V

CC_CORE

(measured at the processor pins) and I

for different processors.

1.1.3 No Load Operation EXPECTED

The VRM should operate in a no-load condition: i.e., with no processor installed. The VRM

does not need to meet the output regulation specifications described in Table 1, but its output

must not exceed 110% of the value of the maximum DC output voltage, and it must not trigger

over-voltage fault detection circuitry. When the VRM is subsequently loaded with the minimum

values listed in Table 1, it must begin to regulate and source current without triggering failures or

causing control signal malfunction.

1.1.4 Turn-on Response Time PROPOSED

The output voltage should reach its specified range within 50 msec of the input power reaching

its minimum voltage.

1.1.5 Overshoot at Turn-On or Turn-Off REQUIRED

Overshoot upon the application or removal of the input voltage must be less than 2% above the

nominal output voltage set by the Voltage Identification (VID) code. No negative voltage may

be present on any output during turn-on or turn-off.