adv7322 Analog Devices, Inc., adv7322 Datasheet - Page 62

• Manufacturer Part Number: adv7322
• Description: Multiformat 11-bit Hdtv Video Encoder
• Manufacturer: Analog Devices, Inc.

ADV7322
BOARD DESIGN AND LAYOUT
DAC TERMINATION AND LAYOUT
CONSIDERATIONS
The ADV7322 contains an on-board voltage reference. The
ADV7322 can be used with an external V
The R
AGND and are used to control the full-scale output current and,
therefore, the DAC voltage output levels. For full-scale output,
R
be changed. R
VIDEO OUTPUT BUFFER AND OPTIONAL
OUTPUT FILTER
Output buffering on all six DACs is necessary 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 ADV7322 is connected
to a device that requires this filtering.
The filter specifications vary with the application.
Table 36. External Filter Requirements
Application
SD
SD
PS
PS
HDTV
HDTV
OUTPUT
SET
DAC
must have a value of 3040 Ω. The RSET values should not
SET
Figure 84. Example of Output Filter for SD, 16× Oversampling
600:
resistors are connected between the R
LOAD
10PH
Oversampling
2×
16×
1×
8×
1×
2×
22pF
has a value of 300 Ω for full-scale output.
600:
560:
3
4
Cutoff
Frequency
(MHz)
>6.5
>6.5
>12.5
>12.5
>30
>30
560:
REF
1
(AD1580).
SET
75:
Attenuation
–50 dB @
(MHz)
20.5
209.5
14.5
203.5
44.25
118.5
pins and
BNC
OUTPUT
Rev. PrA | Page 62 of 88
Table 37. Possible Output Rates from the ADV7322
Input Mode Address
0x01, Bits 6 to 4
SD Only
PS Only
HDTV Only
OUTPUT
OUTPUT
DAC
300:
DAC
–10
–20
–30
–40
–50
–60
–70
–80
0
Figure 85. Filter Plot for Output Filter for SD, 16× Oversampling
Figure 87. Example of Output Filter for HDTV, 2× Oversampling
1M
3
4
Figure 86. Example of Output Filter for PS, 8× Oversampling
600 :
GROUP DELAY (sec)
1
6.8pF
CIRCUIT FREQUENCY RESPONSE
4.7 P H
6.8pF
75:
10M
Preliminary Technical Data
FREQUENCY (Hz)
470nH
33pF
600 :
PLL Address
0x00, Bit 1
Off
On
Off
On
Off On
560 :
PHASE (Deg)
3
4
220nH
82pF
100M
560 :
MAGNITUDE (dB)
75:
500:
1
3
4
75 :
Output Rate
(MHz)
27 (2×)
216 (16×)
27 (1×)
216 (8×)
74.25 (1×)
148.5 (2×)
500:
1
1G
0
–30
–60
–90
–120
–150
–180
–210
–240
OUTPUT
BNC
OUTPUT
BNC
24n
21n
18n
15n
12n
9n
6n
3n
0