adv7150 Analog Devices, Inc., adv7150 Datasheet - Page 24

• Manufacturer Part Number: adv7150
• Description: Cmos 220 Mhz True-color Graphics Triple 10-bit Video Ram-dac
• Manufacturer: Analog Devices, Inc.

ADV7150
DIGITAL-TO-ANALOG CONVERTERS
(DACS) AND VIDEO OUTPUTS
The ADV7150 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 = “l”) 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
Figure 29. DAC Output Termination (Doubly Terminated
75
Description
WHITE LEVEL
VIDEO
VIDEO to BLANK
BLACK LEVEL
BLACK to BLANK
BLANK LEVEL
SYNC LEVEL
Decoded on IOG; Pedestal = 0 IRE; R
Load)
TERMINATION)
DACs
(SOURCE
Z S = 75
IOR, IOG, IOB
load (doubly terminated 75 ).
Z O = 75
SET
(CABLE)
= 265 .
IOG
(mA)
26.67
Video + 9.05
Video + 1.44
9.05
1.44
7.62
0
PLL
and V
Table V. Video Output Truth Table
Z L = 75
(MONITOR)
REF
as well as
IOR, IOB
(mA)
19.05
Video + 1.44
Video + 1.44
1.44
1.44
0
0
–24–
Reference Input and R
An external 1.23 V voltage reference is required to drive the
analog outputs of the ADV7150. 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.
Figure 30. Composite Video Waveform ( SYNC Decoded
on IOG; Pedestal = 7.5 IRE; R
Variations on RS-343A
Various other video output configurations can be implemented
by the ADV7150, including RS-170. Values of R
lar output video formats/levels are calculated by using the equa-
tions for R
table shows calculated values of R
mon variants on the RS-343A standard. The associated wave-
forms are shown in the diagrams.
19.05
1.44 0.054
IOR, IOB
mA
0
0.714
V
0
SET
SET
26.67 1.000
7.62
mA
9.05
0
given in the “Pin Configuration” section. The
SYNC
1
1
0
1
0
1
0
IOG
REF
is connected between the R
0.340
0.286
V
0
input.
load. Figure 30 illustrates the resulting
92.5 IRE
SET
7.5 IRE
40 IRE
SET
BLANK
1
1
1
1
1
0
0
SET
= 280 )
for some of the most com-
SET
SET
has a value of
input of the part
SET
DAC
Input Data
3FFH
Data
Data
000H
000H
xxxH
xxxH
for particu-
WHITE
LEVEL
BLACK
LEVEL
BLANK
LEVEL
SYNC
LEVEL
REV. A