BH7240A データシートの表示（PDF） - ROHM Semiconductor

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BH7240A

Color TV signal encoder

ROHM Semiconductor 

Multimedia ICs

•Circuit operation

(1) The DAC system clock is input to the VCLK pin.

RGB data is taken into the IC at the rising edge of this

clock.

BH7240AKV

RGBDATA

0

1

2

3

4

5

VCLK

Internal RGB

0

1

2

3

4

5

(2) The subcarrier is input to the SCIN pin. There is an

internal input capacitor in the IC, so no external DC

cutoff is necessary. Also, the input level supports a

range of 0.5 to 5Vp-p. To avoid offset in the chromi-

nance phase, distortion-free sine waves or pulses with

a duty of 50% should be input in a range which does

not exceed the VCC and GND.

(3) Composite SYNC signals are input to SYNCIN.

When the input level is low, SYNC signals are output to

the composite output (VOUT) and luminance output

(YOUT), and DC clamping of the RGB signals from the

DAC is carried out at this timing. To prevent erroneous

clamping, RGB data should be set to 00 input during

the SYNC interval.

(4) Burst timing and the chrominance phase reversal

timing when PAL is used are generated by SYNC sig-

nals and subcarriers. For this reason, signals input as

SYNC signals and subcarriers should be in confor-

mance with standards.

•External dimensions (Units: mm)

(5) The NT / PAL pin is used to select the video output

system. When the input level is high, NTSC is selected,

and when the input level is low, PAL is selected. When

PAL is selected, the chrominance phase is reversed

once every hour.

(6) A trap filter is connected to the YTRAP pin. This

eliminates the chrominance band component that

includes the luminance signal, and reduces cross-

color. This filter is effective only for composite output

(VOUT), and does not affect luminance output (YOUT).

(7) Composite signals are output from the VOUT pin. An

internal 75Ω driver enables direct drive of the 75Ω

load. (However, DC cutoff is required.)

(8) Luminance signals and chrominance signals are

output from the YOUT and COUT pins, respectively. An

internal 75Ω driver enables direct drive of the 75Ω

load. (However, DC cutoff is required.)

(9) Analog RGB signals are output from ROUT, GOUT,

and BOUT. An internal 75Ω driver enables direct drive of

the 75Ω load. (However, DC cutoff is required.)

9.0 ± 0.3

7.0 ± 0.2

36 25

37

24

48

1

13

12

0.5 0.2 ± 0.1

0.125 ± 0.1

0.10

VQFP48

9

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