Nikon COOLPIX 4500 Maintenance Manual
VAA11901-R.3579.A
- E3 ･ E4500 -
1-2. CA2 CIRCUIT DESCRIPTION
1. IC995 (H driver, CDS, AGC Circuit and A/D
Converter)
IC995 contains the functions of H driver, CDS, AGC
and A/D converter. H
and A/D converter. H
φ
1, H
φ
2, and RG are
generated inside as holizontal clock driver for CCD
image sensor, and they output to CCD. The video
signal which is output from the CCD is input to Pins
(29) of IC995. There are sampling hold blocks inside
IC905 generated from the SHP and SHD pulses, and it
is here that CDS (correlated double sampling) is carried
out.
After passing through the CDS circuit, the signal passes
through the VGA (Variable Gain Amplifier). It is A/D
converted internally into a 12-bit signal, and is then
input to ASIC (IC102).
The gain of the VGA is controlled by pin (36)-(38)
serial signal which is output from ASIC (IC102).
image sensor, and they output to CCD. The video
signal which is output from the CCD is input to Pins
(29) of IC995. There are sampling hold blocks inside
IC905 generated from the SHP and SHD pulses, and it
is here that CDS (correlated double sampling) is carried
out.
After passing through the CDS circuit, the signal passes
through the VGA (Variable Gain Amplifier). It is A/D
converted internally into a 12-bit signal, and is then
input to ASIC (IC102).
The gain of the VGA is controlled by pin (36)-(38)
serial signal which is output from ASIC (IC102).
Fig. 2-1. IC995 Block Diagram
CCDIN
RG
H1-H4
VD
HD
SDATA
SCK
SL
CLI
CLPOB
CLPDM
DOUT
VRB
VRT
PRECISION
TIMING
CORE
SYNC
GENERATOR
PxGA
VGA
ADC
10
2~36 dB
PBLK
VREF
CLAMP
INTERNAL
REGISTERS
INTERNAL
CLOCKS
CDS
CLAMP
HORIZONTAL
DRIVERS
4