Circuit Description; Clamp Circuit; A/D Converter - Toshiba TLP411E Technical Training Manual

2. CIRCUIT DESCRIPTION

2-1. Clamp Circuit

A/D converter converts the video signal demodulated to
RGB signals in the digital signals to perform digital-pro-
cess.
RX15 RX17
18k 2.2k
CX06
16V1
G
QX06
CX05 2SA1586Y
signal
DX03
16V10
1SS187
RX16
100
QX48
2SA1586Y
RX13 RX14
10k 2.7k
CY02
25V0.1

2-2. A/D Converter

Either CXD1175AM manufactured by SONY or
TLC5510INS manufactured by TI is used for A/D converter
(QX16, QX17 and QX18).
Both of CSD1175AM and TLC5510NS are equivalent and
are 8-bits C-MOS A/D converter with maximum conver-
sion rate of 20M sample/s.
Fig. 6-5 shows pin configuration of CXD1175AM and table
6-6 shows the terminal functions, and Fig. 6-6 shows the
internal block diagram.
The signal input voltage range of the IC varies from 0.5 to
2.5V and the IC is used for each RGB channel. Totally
three ICs are used.
QX10 CX07
2SC4116Y 16V10
RX20
2.2k
RY39
1.8k
QX09
2SA1586Y
QX08
2SC42138
RX22
100 1%
RX21
1k
QX07
2SC4116Y
RX18 RX19
560 10k
Clamp pulse
Fig. 6-4 Clamp circuit diagram
The video signal is clamped to fit the reference level of the
A/D converter. The clamp is of a pedestal clamp type and
uses the reference level voltage of A/D converter. The ac-
tual clamp voltage potential is approx. 1.2V.
Fig. 6-4 shows the clamp circuit for G signal section.
+5V
CX08
16V0.33
ZX03 TEM1043
RZ04
TEM2026D
24 23 22 21 20 19 18 17 16 15 14 13
RX23
220
RX24
1k
1
OE 1
DGND 2
D1(LSB) 3
D2 4
D3 5
D4 6
D5 7
D6 8
D7 9
D8(MSB) 10
VDDD 11
CLK 12
Fig. 6-5 Pin configuration of µPD6453GT
6-5
CX16
16V10
CY15 CY16
16V0.33 16V0.33
CX17
16V0.33
CXD1175AM
2 3 4 5 6 7 8 9 10 11 12
CX18
16V1
Clock
24 DGND
23 VRB
22 VRBS
21 AGND
20 AGND
19 VIN
18 VDDA
17 VRT
16 VRTS
15 VDDA
14 VDDA
13 VDDD
+5V
QX17
Data
output