Power And Signal Distribution; Introduction; Power Distribution; Usdt Power Distribution - HP Compaq dc7900 USDT Technical Reference Manual

7.1

Introduction

This chapter describes the power supplies and discusses the methods of general power and signal
distribution. Topics covered in this chapter include:
■

Power distribution (7.2)

■
Power Control (7.3)
■
Signal distribution (7.4)
7.2 Power Distribution
Each form factor uses a unique power supply assembly and implements different methods of
power generation and distribution. The USDT form factor uses an external ("brick") supply
while the SFF and CMT form factors use a power supply unit contained within the system
chassis. The subassemblies are not interchangeable between the three form factors.

7.2.1 USDT Power Distribution

The USDT form factor uses an external ("brick") supply that connects to the chassis through a
three-conductor cable (Figure 7-1). All voltages required by the processing circuits, peripherals,
and storage devices are produced on the system board from the 19.5 VDC produced by the
external power supply assembly. The external power supply always produces 19.5 VDC as long
as it is connected to an active AC outlet.
Front Bezel
Power Button
90 - 264 VAC
Figure 7-1. USDT Power Generation, Block Diagram
Technical Reference Guide

Power and Signal Distribution

Power On
USDT Chassis
System Board
Power Logic,
Voltage Regulators
+19.5
Rtn
Pwr rating
VDC & ID
External
Power Supply
Unit
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7-1