adv7390 Analog Devices, Inc., adv7390 Datasheet - Page 62

• Manufacturer Part Number: adv7390
• Description: Low Power, Chip Scale 10-bit Sd/hd Video Encoder
• Manufacturer: Analog Devices, Inc.

ADV7390/ADV7391/ADV7392/ADV7393
PRINTED CIRCUIT BOARD LAYOUT AND DESIGN
DAC CONFIGURATIONS
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, R
Full-drive is the recommended mode of operation for the DACs.
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, R
The ADV739x contains a R
the R
current and, therefore, the output voltage levels of DAC 1, DAC 2,
and DAC 3. For full-drive operation, R
of 510 Ω and RL must have a value of 37.5 Ω. For low drive
operation, R
a value of 300 Ω.
The resistor connected to the R
tolerance.
The ADV739x contains a compensation pin, COMP. A 2.2 nF
compensation capacitor should be connected from the COMP
pin to V
VIDEO OUTPUT BUFFER AND OPTIONAL
OUTPUT FILTER
An output buffer is necessary on any DAC that operates in low
drive mode (R
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.
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.
For applications requiring an output buffer and reconstruction
filter, the
buffers should be considered.
SET
pin and AGND is used to control the full-scale output
AA
ADA4430-1
.
SET
SET
must have a value of 4.12 kΩ, and R
= 4.12 kΩ, R
and
ADA4411-3
SET
L
.
pin. A resistor connected between
L
SET
= 300 Ω). Analog Devices Inc.
pin should have a 1%
SET
integrated video filter
must have a value
L
must have
L
.
Rev. 0 | Page 62 of 96
Table 52. ADV739x Output Rates
Input Mode
(0x01, Bits[6:4])
SD
ED
HD
Table 53. Output Filter Requirements
Application
SD
ED
HD
OUTPUT
OUTPUT
OUTPUT
DAC
DAC
DAC
300Ω
Figure 86. Example of Output Filter for SD, 16× Oversampling
Figure 88. Example of Output Filter for HD, 4× Oversampling
Figure 87. Example of Output Filter for ED, 8× Oversampling
600Ω
3
600Ω
4
10µH
22pF
Oversampling
2×
8×
16×
1×
4×
8×
1×
2×
4×
6.8pF
4.7µH
6.8pF
1
75Ω
Oversampling
Off
On
On
Off
On
On
Off
On
On
600Ω
390nH
33pF
600Ω
560Ω
560Ω
3
4
3
4
33pF
Cutoff
Frequency
(MHz)
> 6.5
> 6.5
> 6.5
> 12.5
> 12.5
> 12.5
> 30
> 30
> 30
560Ω
560Ω
75Ω
1
1
Output Rate (MHz)
27
108
216
27
108
216
74.25
148.5
297
500Ω
3
4
75Ω
75Ω
500Ω
Attenuation
–50 dB @
(MHz)
20.5
101.5
209.5
14.5
95.5
203.5
44.25
118.5
267
1
(2×)
(8×)
(16×)
(1×)
(4×)
(8×)
(1×)
(2×)
(4×)
OUTPUT
BNC
OUTPUT
BNC
OUTPUT
BNC