Product specifications

Design Guide - VT82C694X Apollo Pro133 with VT82C686A
Preliminary Revision 0.5, November 19, 1999 63 Motherboard Design Guidelines
Technologies, Inc.
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2.5.3 Hardware Monitoring
The hardware monitoring interface includes five positive voltage sensing inputs (four external and one internal), three temperature
sensing inputs (two external and one internal), two fan-speed monitoring inputs and one chassis intrusion detection input.
Programmable control, status, monitor and alarm are supported by the VT82C686A for flexible desktop management. The
following sections provide detailed descriptions for each hardware monitor subsystem. An application circuit for hardware
monitoring is shown in Figure 2.56. In order to achieve a stable VCC3 input to the Hardware Monitoring Subsystem, a 0.1uF
decoupling capacitor should be placed as close to the Hardware Monitoring power and ground pins as possible.
VT82C686A
(South Bridge)
VSENS
16K
ohm
53K
ohm
10K
ohm
10K
ohm
VCC2 VCCI +5V +12V
FAN1
FAN2
TSEN1
TSEN2
VREF
10K ohm
Thermister
10K ohm
Thermister
4.7K
ohm
4.7K
ohm
VCC3
+12V
CHASSIS
10K
ohm
VCC3
Mechanical Switch
VCC3
Ferrite Bead
Ferrite Bead
10uF0.1uF
VSENS
VSENS
VSENS
GNDHWM
Ferrite Bead
Ferrite Bead
VCCHWM
GNDHWM
10K ohm 1%
10K ohm 1%
FAN
FAN
Figure 2-56. Hardware Monitoring Application Circuit