ADV7390/ADV7391/ADV7392/ADV7393
PRINTED CIRCUIT BOARD LAYOUT AND DESIGN
DAC CONFIGURATIONS
Table 52. ADV739x Output Rates
Input Mode
(0x01, Bits[6:4])
The ADV739x contains three DACs. All three DACs can be
configured to operate in full-drive mode. Full-drive mode is
defined as 34.7 mA full-scale current into a 37.5 Ω load, RL.
Full-drive is the recommended mode of operation for the DACs.
Oversampling
Output Rate (MHz)
SD
Off
On
On
Off
On
On
Off
On
On
27
(2×)
(8×)
(16×)
(1×)
(4×)
(8×)
(1×)
(2×)
(4×)
108
216
27
108
216
74.25
148.5
297
Alternatively, all three DACs can be configured to operate in low
drive mode. Low drive mode is defined as 4.33 mA full-scale
current into a 300 Ω load, RL.
ED
The ADV739x contains a RSET pin. A resistor connected between
the RSET pin and AGND is used to control the full-scale output
current and, therefore, the output voltage levels of DAC 1, DAC 2,
and DAC 3. For full-drive operation, RSET must have a value
of 510 Ω and RL must have a value of 37.5 Ω. For low drive
operation, RSET must have a value of 4.12 kΩ, and RL must have
a value of 300 Ω.
HD
Table 53. Output Filter Requirements
Cutoff
Attenuation
–50 dB @
(MHz)
Frequency
Application Oversampling (MHz)
The resistor connected to the RSET pin should have a 1%
tolerance.
SD
ED
HD
2×
8×
16×
1×
4×
8×
1×
2×
4×
> 6.5
> 6.5
> 6.5
> 12.5
> 12.5
> 12.5
> 30
20.5
101.5
209.5
14.5
The ADV739x contains a compensation pin, COMP. A 2.2 nF
compensation capacitor should be connected from the COMP
pin to VAA
.
95.5
VIDEO OUTPUT BUFFER AND OPTIONAL
OUTPUT FILTER
203.5
44.25
118.5
267
> 30
> 30
An output buffer is necessary on any DAC that operates in low
drive mode (RSET = 4.12 kΩ, RL = 300 Ω). Analog Devices Inc.
produces a range of op amps suitable for this application, for
example, the AD8061. For more information about line driver
buffering circuits, see the relevant op amp data sheet.
10µH
DAC
OUTPUT
3
4
75Ω
BNC
OUTPUT
600Ω
22pF
600Ω
1
An optional reconstruction (anti-imaging) low-pass filter (LPF)
may be required on the ADV739x DAC outputs. The filter
specifications vary with the application. The use of 16× (SD),
8× (ED), or 4× (HD) oversampling can remove the requirement
for a reconstruction filter altogether.
560Ω
560Ω
Figure 86. Example of Output Filter for SD, 16× Oversampling
For applications requiring an output buffer and reconstruction
filter, the ADA4430-1 and ADA4411-3 integrated video filter
buffers should be considered.
4.7µH
DAC
OUTPUT
3
75Ω
BNC
OUTPUT
6.8pF
6.8pF
600Ω
1
600Ω
4
560Ω
560Ω
Figure 87. Example of Output Filter for ED, 8× Oversampling
DAC
OUTPUT
3
390nH
75Ω
BNC
OUTPUT
300Ω
3
1
33pF
33pF
75Ω
1
4
4
500Ω
500Ω
Figure 88. Example of Output Filter for HD, 4× Oversampling
Rev. 0 | Page 62 of 96
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