ADV7121/ADV7122

–8–

REV. B

If we, therefore, have a graphics system with a 1024

× 1024

resolution, a noninterlaced 60 Hz refresh rate and a retrace fac-

tor of 0.8, then:

Dot Rate =

1024

× 1024 × 60/0.8

=

78.6 MHz

The required CLOCK frequency is thus 78.6 MHz.

All video data and control inputs are latched into the ADV7121/

ADV7122 on the rising edge of CLOCK, as previously de-

scribed in the “Digital Inputs” section. It is recommended that

the CLOCK input to the ADV7121/ADV7122 be driven by a

TTL buffer (e.g., 74F244).

92.5 IRE

7.5 IRE

40 IRE

WHITE LEVEL

BLACK LEVEL

BLANK LEVEL

SYNC LEVEL

19.05

0.714

26.67 1.000

1.44

0.054

9.05

0.340

0

0

7.62

0.286

0

0

mA

V

mA

V

RED, BLUE

GREEN

NOTES

1. OUTPUTS CONNECTED TO A DOUBLY TERMINATED 75

Ω

LOAD.

3. RS–343A LEVELS AND TOLERANCES ASSUMED ON ALL

LEVELS.

Figure 3. RGB Video Output Waveform

Table Ia. Video Output Truth Table for the ADV7122

IOG

IOR, IOB

DAC

Description

(mA)*

(mA)

SYNC

BLANK

Input Data

WHITE LEVEL

26.67

19.05

1

1

3FFH

VIDEO

video + 9.05

video + 1.44

1

1

data

VIDEO to BLANK

video + 1.44

video + 1.44

0

1

data

BLACK LEVEL

9.05

1.44

1

1

00H

BLACK to BLANK

1.44

1.44

0

1

00H

BLANK LEVEL

7.62

0

1

0

xxH

SYNC LEVEL

0

0

0

0

xxH

Table Ib. Video Output Truth Table for the ADV7121

IOR, IOG, IOB

DAC

Description

(mA)*

Input Data

WHITE LEVEL

17.62

3FF

VIDEO

video

data

VIDEO to BLACK

video

data

BLACK LEVEL

0

00H