Voltage Regulator-Down (VRD) 10.0

Output Indicators
R
VRD Design Guide
45
PROCHOT# is an open-drain, active-low i/o buffer terminated to the system Vtt (FSB termination
voltage). To maintain reliable signaling between thermal monitor circuit, processor, and chipset,
the bipolar transistor must be selected to operate with a collector bias established using a single,
130 Ω pull-up resistor. Use of additional termination or pull-up resistors may lead to signal
integrity or logic threshold failures. The values for R1, R2 and R3 in Figure 15 are included as an
example and must be calculated using specific design parameters. The value of R2 is adjusted to
calibrate the comparator’s trigger reference voltage (and assertion of PROCHOT#) against the
sensor voltage representing a thermal violation.
6.3 Load Indicator Output (PROPOSED)
To assist VRD circuit debug and validation, the PWM controller supplier may choose to include
an output voltage that is a defined function of the VRD output current.