ROHM BH7236AF Datasheet

1

Multimedia ICs

Color TV Signal Encoder

BH7236AF

The BH7236AF converts analog RGB signals into color TV signals in the NTSC and PAL formats. From inputs of
analog RGB signals, a composite synch signal, burst pulses and a color carrier, this IC generates a color TV signal,
and can be adapted for either NTSC or PAL standards, which are selected externally. When set to PAL, chroma
phase is switched for each line.
The chroma signals and luminosity signals can be combined into a color TV signal or output separately, making this
IC suitable for S pins. There are also pins for analog RGB signal output, and each output pin has its own internal
75Ω driver.

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Applications

TV peripherals

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Features

1) Can be adapted for NTSC and PAL formats.

2) Internal burst timing signal generator with half-H
killer.

3) Internal flip-flop for PAL phase switching.

4) Separate Y / C output pins.

5) Analog RGB signal output pins.

6) Internal 75Ω driver. (outputs color TV signals, lumi­nosity signals, chroma signals and analog RGB sig­nals)

7) Adaptable for color subcarrier pulse input.

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Block diagram

1

2

3

4

5

6

7

8

9

10

11

12

24

23

22

21

20

19

18

17

16

15

14

13

CLAMP

75Ω

75Ω

75Ω

75Ω

75Ω

75Ω

CLAMP

CLAMP

FILTER

PHASE

SIFTER

MATRIX

B-Y MOD.

R-Y MOD.

F · F

Y / C

MIX

BPF

DELAY

SYNC

MIX

BFP GEN.

BFP

BFP

GND2

R

OUT

GOUT

BOUT

VOUT

VCC2

YOUT

COUT

GND1

RIN

GIN

BIN

SCIN

NT / PAL

BFPOUT

SYNCIN

SYNCOUT

V

CC1

N. C.

N. C.

N. C.

N. C.

N. C

YTRAP

SYNC

SYNC

SYNC

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Multimedia ICs BH7236AF

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Pin descriptions

Pin name

1 GND1 Ground for all drivers other than the 75

Ω

driver.
2 RIN Analog R signal input. Drive at low impedance.
3 GIN Analog G signal input. Drive at low impedance.
4 BIN Analog B signal input. Drive at low impedance.
5 N. C. This pin is not connected inside the IC.

6 SCIN

7 NT / PAL

8 BFPOUT
9 N. C. This pin is not connected inside the IC.

10 SYNCIN
11 SYNCOUT Composite synchronization signal output.

12
13 N. C. This pin is not connected inside the IC.
14 N. C. This pin is not connected inside the IC.
15 C

OUT

Chroma signal output. Internal 75Ω driver.

16 Y

OUT

Luminance signal output. Internal 75Ω driver.
17 YTRAP
18 N. C. This pin is not connected inside the IC.

19
20 V

OUT

Color TV signal output. Internal 75Ωdriver.
21 B

OUT

Analog B signal output. Internal 75Ω driver.
22 G

OUT

Analog G signal output. Internal 75Ω driver.
23 R

OUT

Analog R signal output. Internal 75Ω driver.
24 GND2 Ground for the 75

Ω

driver.

Power supply pin for all except the 75

Ω

driver.

Power supply pin for the 75

Ω

driver.

Color subcarrier input. Input a 3.579545MHz

(

NTSC) or 4.433619MHz (PAL) sign wave or pulse wave

(50% duty). Do not exceed the range of GND-Vcc.

Burst timing output. Burst timing is generated inside the IC when the subcarrier and composite

synchronization signal.

Selecting the type of color TV signal output. The high level selects NTSC, the low level PAL. Internally

pulled up to 50k

Ω

.

Attached luminance trap filter. Attaching a trap filter reduces chroma signal cross-color caused

by the luminance signal. Output impedance is approximately 2k

Ω

.

Pin No. Function

V

CC1

V

CC2

Composite synchronization signal input. When the low level is input, the synchronization signal is output to

both YOUT and VOUT, and inputs to RIN, GIN and BIN are clamped. This pin is internally pulled up to 100k

Ω

.