adv7152 Analog Devices, Inc., adv7152 Datasheet - Page 22

• Manufacturer Part Number: adv7152
• Description: Cmos 220 Mhz True-color Graphics Triple 10-bit Video Ram-dac
• Manufacturer: Analog Devices, Inc.

ADV7152
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 I
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
Description
WHITE LEVEL
VIDEO
VIDEO to BLANK
BLACK LEVEL
BLACK to BLANK
BLANK LEVEL
SYNC LEVEL
Figure 28. Composite Video Waveform ( SYNC Decoded on IOG; Pedestal = 7.5 IRE; R
load (doubly terminated 75 ).
19.05
1.44
mA
0
IOR, IOB
0.714
0.054
V
0
IOG
(mA)
26.67
Video + 9.05
Video + 1.44
9.05
1.44
7.62
0
26.67
9.05
7.62
mA
0
IOG
PLL
0.340
0.286
1.000
V
0
and V
Table V. Video Output Truth Table
REF
92.5 IRE
as well as
7.5 IRE
40 IRE
IOR, IOB
(mA)
19.05
Video + 1.44
Video + 1.44
1.44
1.44
0
0
–22–
Figure 27. DAC Output Termination (Doubly Terminated
75
Reference Input and R
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 V
A resistor R
and ground. For specified performance, R
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
video waveform, and the Video Output Truth Table shows the
corresponding control input stimuli.
Load)
DACs
TERMINATION)
SET
IOR, IOG, IOB
Z
SYNC
1
1
0
1
0
1
0
(SOURCE
REF
S
is connected between the R
=75
input.
load. Figure 28 illustrates the resulting
SET
BLACK LEVEL
SYNC LEVEL
WHITE LEVEL
BLANK LEVEL
BLANK
1
1
1
1
1
0
0
Z
(CABLE)
O
= 75
SET
SET
= 280 )
SET
has a value of
input of the part
DAC
Input Data
3FFH
Data
Data
000H
000H
xxxH
xxxH
Z
(MONITOR)
L
= 75
REV. B