A1 Main Pca Block Description; Power Supply; Digital Kernel - Fluke 2640A Service Manual

A1 Main PCA Block Description

The A1 Main pca description is divided into sections for each primary pca function as
described below.

Power Supply

The Power Supply functional block (Figure 2-3) provides voltages required by the
outguard digital circuitry: +4.9V dc (Vcc); the vacuum-fluorescent display: -30V dc and
filament voltage of 5.4V ac; the inguard circuitry: +5.2V dc (Vdd), +5.6V dc (Vddr), and
-5.2V dc; and RS-232 interface voltage: -5.0V dc (Vee).
Within the power supply, the raw dc supply converts 107 to 264V ac line voltage into a
dc level and applies it to the power switch, and/or the 9 to 16V dc input is applied to the
power switch. The 5V Switcher (A1U9, A1U28) converts the dc from the power switch
into 4.9V +/-0.05V dc, which is used by the Inverter (A1U22, A1U23) in generating the
above-mentioned outputs. A Power Fail Detector provides a power supply status signal
to the Microprocessor in the Digital Kernel.
Within the Ethernet interface (A1U16, A1U32) there is an inverter module that provides
an isolated -9V dc supply for the 10BASE2 transceiver. The inverter module is powered
from the 4.9V dc (Vcc) supply. There is also a small power supply that provides a
programming voltage (Vpp) for the FLASH EPROM device on the outguard digital
kernel.
107 to 264
V ac In
9 to 16
V dc In

Digital Kernel

The Digital Kernel functional block is responsible for the coordination of all activities
within the instrument. This block requires voltages from the Power Supply and signals
from the Power-on Reset circuit.
Specifically, the Digital Kernel microprocessor (A1U1) performs the following
functions:
•
Executes the instructions stored in FLASH EPROM (A1U21).
•
Stores instrument calibration data in FLASH EPROM.
Power
Switch
5V Switcher
Inverter
Regulator
Figure 2-3. Power Supply Block Diagram
Theory of Operation
Functional Block Description
2-3.
2-4.
+4.9V dc (Vcc)
5.4V ac (display)
-30V dc (display)
Regulator +5.2V dc (Vdd)
Regulator +5.6V dc (Vddr)
Regulator -5.2V dc (Vss)
Regulator -5.0V dc (Vee)
2-5.
2
2-7