BH7236AF Просмотр технического описания (PDF) - ROHM Semiconductor

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производитель

BH7236AF

Color TV Signal Encoder

ROHM Semiconductor 

Multimedia ICs

•Measurement circuit

BH7236AF

1

Analog R signal

2

0.1µ

Analog G signal

3

0.1µ

Analog B signal

4

0.1µ

5

CLAMP

SYNC

CLAMP

SYNC

CLAMP

SYNC

Color subcarrier

6

VCC

7

NT / PAL selector

MATRIX

BGPOUT 8

N.C. 9

Composite SYNCH

10

BFP

BFP GEN.

SYNCOUT measurement

point

11

VCC

12

SYNC

24

+ 75

75Ω

23

220µ

75

+ 75

75Ω

22

220µ

75

+ 75

75Ω

21

220µ

75

+ 75

75Ω

20

220µ

75

VCC

19

18 N.C.

17

+ 75

75Ω

16

220µ

75

75

75Ω

15

0.47µ

75

14 N.C.

13 N.C.

ROUT measurement

point

GOUT measurement

point

BOUT measurement

point

VOUT measurement

point

YOUT measurement

point

COUT measurement

point

•Circuit operation

(1) SYNCIN is for composite synch input. During low

input, the synchronization signal is output to YOUT,

VOUT and SYNCOUT. This signal also controls the timing

of the pedestal clamps of RIN, GIN and BIN. (The

pedestal levels of RIN, GIN and BIN are kept constant by

charging an attached capacitor.)

(2) SCIN is for color subcarrier input. Set input to a

pulse wave or sine wave (3.579545MHz for NTSC and

4.433619MHz for PAL).

(3) NT / PAL is the NTSC / PAL selector pin, and con-

nects to Vcc when set to NTSC and to GND when set

to PAL. Chroma phase is switched for each line when

the IC is set to PAL.

(4) Using the composite synch and subcarrier inputs,

the IC generates a burst flag signal, according to which

a burst signal is output to COUT and VOUT. The half-H

killer presents the burst signal from being output at the

wrong points.

(5) PAL chroma phases are also switched at a regular

cycle (1H) during vertical synchronization.

(6) COUT and YOUT are for output of chroma signals and

luminosity signals, respectively. Because the chroma

signal and luminosity signals can be output separately,

the IC can be adapted for S pins. Each has a 75Ω dri-

ver.

(7) VOUT is for color TV signal output, and has an inter-

nal 75Ω driver.

(8) ROUT, GOUT and BOUT are for analog RGB signal out-

put, and have an internal 75Ω driver.

5

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