Voltage Regulator-Down (VRD) 10.0 Design Guide Addendum

VRD Design Guide Addendum

6 Output Indicators

6.1 Processor Power Good Output (Vcc_PWRGD)

(PROPOSED)

The VRD should provide a power-good signal, which remains in the low state until a maximum

of 10 milliseconds after the output voltage reaches the range specified in Section 2.2. The signal

should then remain asserted when the VRD is operating, except for fault or shutdown conditions.

Vcc_PWRGD must not be de-asserted during the Dynamic VID operation.

Table 7. Power Good Specifications

Design Parameter Specification

Signal Type

Open-collector or equivalent

Voltage Range

5.5 V (maximum) in open state

Minimum I

4 mA

Maximum V

0.4 V

6.2 VRD Thermal Monitoring (Proposed)

This section describes how to protect the voltage regulator design from heat damage while

supporting thermal design current (VR TDC) specifications. It is included for reference and is

applicable to Pentium 4 processor Extreme Edition supporting Hyper-Threading Technology in

socket 478 designs. It is not recommend integrating this feature into Vcc PWM controller designs.

Each customer is responsible for identifying maximum temperature specifications for all

components in the voltage regulator design and ensuring that these specifications are not violated

while continuously drawing specified VR TDC levels. In the event of a catastrophic thermal

failure, the thermal monitoring circuit is to assert the PROCHOT# signal immediately prior to

exceeding maximum motherboard and component thermal ratings to prevent heat damage.

Assertion of this signal will lower processor power consumption and reduce current draw through

the voltage regulator, resulting in lower component temperatures. Assertion of PROCHOT#

degrades system performance and must never occur when drawing less than specified thermal

design current.

VRD temperature violations can be detected using a thermal sensor and associated control

circuitry (see Figure 6). For this implementation, a thermistor (THMSTR) is placed in the

temperature sensitive region of the voltage regulator. The location must be chosen carefully and is

to represent the position where initial thermal violations are expected to occur. When exceeded,

the thermal monitor circuit is to initiate PROCHOT# to protect the voltage regulator from heat

damage.