Voltage Regulator-Down (VRD) 10.0

Output Indicators

VRD Design Guide

6 Output Indicators

6.1 Processor Power Good Output (Vcc_PWRGD)

(PROPOSED)

The VRD must provide a power-good signal, which remains in the low state for 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 due to the low voltage functionality of Dynamic Voltage

Identification.

Table 19. 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 a circuit to protect the voltage regulator design from heat damage while

supporting thermal design current (VR TDC) specifications.

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 processor signal PROCHOT# 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 15). 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 known to occur. When the critical

temperature is exceeded, the thermal monitor circuit is to initiate PROCHOT# to protect the

voltage regulator from heat damage.