
REV. A
ADV7310/ADV7311
–55–
BOARD DESIGN AND LAYOUT CONSIDERATIONS
DAC Termination and Layout Considerations
The ADV7310/ADV7311 contain an on-board voltage reference.
The ADV7310/ADV7311 can be used with an external V
REF
(AD1580).
The R
SET
resistors are connected between the R
SET
pins and
AGND and are used to control the full-scale output current and
therefore the DAC voltage output levels. For full-scale output,
R
SET
must have a value of 3040
. The R
SET
values should not
be changed. R
LOAD
has a value of 300
for full-scale output.
Video Output Buffer and Optional Output Filter
Output buffering on all six DACs is necessary in order to drive
output devices, such as SD or HD monitors. Analog Devices
produces a range of suitable op amps for this application, for
example the AD8061. More information on line driver buffering
circuits is given in the relevant op amps’ data sheets.
An optional analog reconstruction low-pass filter (LPF) may be
required as an anti-imaging filter if the ADV7310/ADV7311 is
connected to a device that requires this filtering.
The filter specifications vary with the application.
Table XVI. External Filter Requirements
Cutoff
Frequency Attenuation
(MHz)
Application
Oversampling
2
×
16
×
1
×
8
×
1
×
2
×
–50 dB @ (MHz)
SD
SD
PS
PS
HDTV
HDTV
>6.5
>6.5
>12.5
>12.5
>30
>30
20.5
209.5
14.5
203.5
44.25
118.5
560
600
3
4
1
22pF
600
DAC
OUTPUT
75
BNC
OUTPUT
10 H
560
Figure 55. Example of Output Filter for SD,
16
×
Oversampling
0
–80
–70
–60
–50
–40
–30
–20
–10
0
–30
–60
–90
–120
–150
–180
–210
–240
1G
1M
10M
100M
FREQUENCY (Hz)
CIRCUIT FREQUENCY RESPONSE
GROUP DELAY (sec)
PHASE (Deg)
MAGNITUDE (dB)
21n
18n
15n
12n
9n
6n
3n
0
24n
G
Figure 56. Filter Plot for Output Filter for SD,
16
×
Oversampling