Ic902 (H Driver) And Ic904 (V Driver); Ic905 (Cds, Agc Circuit And A/D Converter) - Epson PhotoPC 3000Z Service Manual

EPSON PhotoPC 3000Z

2.2.1.3 IC902 (H Driver) and IC904 (V Driver)

An H driver (IC902) and V driver (IC904) are necessary in order to generate the
clocks (vertical transfer clock, horizontal transfer clock and electronic shutter
clock) which drives the CCD.
IC902 is an inverter IC which drives the horizontal CCDs (H1 and H2). In
addition the XV1-XV4 signals which are output from IC102 are the vertical
transfer clocks, and the XSG1 and XSG signal which is output from IC102 is
superimposed onto XV1 and XV3 at IC904 in order to generate a ternary
pulse. In addition, the XSUB signal which is output from IC102 is used as the
sweep pulse for the electronic shutter, and the RG signal which is output from
IC102 is the reset gate clock.
Figure 2-6. IC902 Block Diagram
Operating Principles
XSG3A
Figure 2-7. IC904 Block Diagram

2.2.1.4 IC905 (CDS, AGC Circuit and A/D Converter)

The video signal which is output from the CCD is input to Pins (30) of IC905.
There are S/H blocks inside IC905 generated from the XSHP and XSHD pulses,
and it is here that CDS (correlated double sampling) is carried out.
After passing through the CDS circuit, the signal passes through the AGC
amplifier. It is A/C converted internally into a 12-bit signal, and is then input to
IC102 of the CA2 circuit board. The gain of the AGC amplifier is controlled by
pin (45)-(48) serial signal which is output from IC102 of the CA2 board.
Circuit
V
DD
SHT
Input
Buffer
XSHT
V3B
XV3 V
L
XSG3B
V3A
V1B
XV1 V
H
XSG1B
V1A
XSG1A
V4
XV4
V2
XV2
GND
Revision A
41