
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 output levels equal but opposite 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 these three RGB current outputs is specified to
directly drive a 37.5
load (doubly terminated 75 ).
Z
S =75
(SOURCE
TERMINATION)
DACs
IOR, IOG, IOB
Z
O = 75
Z
L = 75
(MONITOR)
(CABLE)
Figure 27. DAC Output Termination (Doubly Terminated
75
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
. 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
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
mA
V
26.67
1.000
0.714
19.05
1.44
0.054
9.05
0.340
00
0
7.62
0.286
BLANK LEVEL
SYNC LEVEL
GREY
SCALE
Figure 28. Composite Video Waveform (SYNC Decoded on IOG; Pedestal = 7.5 IRE; RSET = 280 )
Table V. Video Output Truth Table
IOG
IOR, IOB
DAC
Description
(mA)
SYNC
BLANK
Input Data
WHITE LEVEL
26.67
19.05
1
3FFH
VIDEO
Video + 9.05
Video + 1.44
1
Data
VIDEO to
BLANK
Video + 1.44
0
1
Data
BLACK LEVEL
9.05
1.44
1
000H
BLACK to
BLANK
1.44
0
1
000H
BLANK LEVEL
7.62
0
1
0
xxxH
SYNC LEVEL
0
xxxH