ADV7152LS85 datasheet(22/32 Pages) AD

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ADV7152

–22–

REV. B

DIGITAL-TO-ANALOG CONVERTERS

(DACS) AND VIDEO OUTPUTS

The ADV7152 contains three high speed video DACs. The

DAC outputs are represented as the three primary analog color

signals IOR (red video), IOG (green video) and IOB (blue video).

Other analog signals on the part include IPLL and VREF as well as

complementary video outputs IOR, IOG, IOB. These comple-

mentary outputs can be used to drive differentially terminated

video loads, they will have equal but opposite output levels to

IOR, IOG and IOB when loaded with a resistive load similar to

IOR, IOG and IOB.

DACs and Analog Outputs

The part contains three matched 10-bit digital-to-analog con-

verters. The DACs are designed using an advanced, high speed,

segmented architecture. The bit currents corresponding to each

digital input are routed to either IOR, IOG, IOB (bit = “1”) or

IOR

, IOG, IOB (bit = “0”). (Normally IOR, IOG, IOB = GND.)

The analog video outputs are high impedance current sources.

Each of the these three RGB current outputs are specified to

directly drive a 37.5

Ω load (doubly terminated 75 Ω).

S =75Ω

(SOURCE

TERMINATION)

DACs

IOR, IOG, IOB

O = 75Ω

L = 75Ω

(MONITOR)

(CABLE)

Figure 27. DAC Output Termination (Doubly Terminated

Ω Load)

Reference Input and RSET

An external 1.23 V voltage reference is required to drive the

analog outputs of the ADV7152. The reference voltage is con-

nected to the VREF input.

A resistor RSET is connected between the RSET input of the part

and ground. For specified performance, RSET has a value of

280

Ω. This corresponds to the generation of RS-343A video

levels (with SYNC on IOG and Pedestal = 7.5 IRE) into a dou-

bly terminated 75

Ω load. Figure 28 illustrates the resulting

video waveform, and the Video Output Truth Table shows the

corresponding control input stimuli.

WHITE LEVEL

BLACK LEVEL

92.5 IRE

7.5 IRE

40 IRE

IOR, IOB

IOG

26.67

1.000

0.714

19.05

1.44

0.054

9.05

0.340

7.62

0.286

BLANK LEVEL

SYNC LEVEL

Figure 28. Composite Video Waveform (SYNC Decoded on IOG; Pedestal = 7.5 IRE; RSET = 280 Ω)

Table V. Video Output Truth Table

IOG

IOR, IOB

DAC

Description

(mA)

SYNC

BLANK

Input Data

WHITE LEVEL

26.67

19.05

3FFH

VIDEO

Video + 9.05

Video + 1.44

Data

VIDEO to BLANK

Video + 1.44

Data

BLACK LEVEL

9.05

1.44

000H

BLACK to BLANK

1.44

000H

BLANK

LEVEL

7.62

xxxH

SYNC

LEVEL

xxxH

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