adv7344 Analog Devices, Inc., adv7344 Datasheet - Page 65

• Manufacturer Part Number: adv7344
• Description: Multiformat Video Encoder Six 14-bit Noise Shaped Video Dacs
• Manufacturer: Analog Devices, Inc.

PRINTED CIRCUIT BOARD LAYOUT AND DESIGN
DAC CONFIGURATIONS
The ADV7344 contains six DACs. All six 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
DAC 1, DAC 2, and DAC 3 can also 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
mode of operation for DAC 1, DAC 2, and DAC 3.
The ADV7344 contains two R
between the R
scale output current and, therefore, the DAC output voltage
levels of DAC 1, DAC 2, and DAC 3. For low drive operation,
R
300 Ω. For full-drive operation, R
and R
A resistor connected between the R
to control the full-scale output current and, therefore, the DAC
output voltage levels of DAC 4, DAC 5, and DAC 6. R
have a value of 4.12 kΩ, and R
is, low drive operation only).
The resistors connected to the R
1% tolerance.
The ADV7344 contains two compensation pins, COMP1 and
COMP2. A 2.2 nF compensation capacitor should be connected
from each of these pins to V
VOLTAGE REFERENCE
The ADV7344 contains an on-chip voltage reference that can be
used as a board-level voltage reference via the V
Alternatively, the ADV7344 can be used with an external
voltage reference by connecting the reference source to the V
pin. For optimal performance, an external voltage reference
such as the AD1580 should be used with the ADV7344. If an
external voltage reference is not used, a 0.1 μF capacitor should
be connected from the 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 ADV7344 DAC outputs if the ADV7344
is connected to a device that requires this filtering. 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.
SET1
must have a value of 4.12 kΩ, and R
L
must have a value of 37.5 Ω.
SET1
SET
= 4.12 kΩ, R
pin and AGND is used to control the full-
REF
pin to V
AA
L
L
SET
.
must have a value of 300 Ω (that
= 300 Ω). Analog Devices, Inc.
L
SET1
. Full-drive is the recommended
pins. A resistor connected
SET1
SET2
and R
AA
must have a value of 510 Ω,
.
pin and AGND is used
L
must have a value of
SET2
pins should have a
REF
pin.
SET2
must
L
.
Rev. 0 | Page 65 of 88
REF
For applications requiring an output buffer and reconstruction
filter, the ADA4430-1, ADA4411-3, and ADA4410-6 integrated
video filter buffers should be considered.
Table 53. ADV7344 Output Rates
Input Mode
(0x01, Bits[6:4])
SD Only
ED Only
HD Only
Table 54. Output Filter Requirements
Application
SD
SD
ED
ED
HD
HD
OUTPUT
OUTPUT
OUTPUT
DAC
DAC
DAC
300Ω
Figure 84. Example of Output Filter for SD, 16× Oversampling
Figure 86. Example of Output Filter for HD, 4× Oversampling
Figure 85. Example of Output Filter for ED, 8× Oversampling
600Ω
3
4
600Ω
10µH
22pF
Oversampling
2×
16×
1×
8×
1×
4×
6.8pF
4.7µH
6.8pF
1
75Ω
600Ω
PLL Control
(0x00, Bit 1)
Off
On
Off
On
Off
On
390nH
33pF
600Ω
560Ω
560Ω
3
4
3
4
33pF
Cutoff
Frequency
(MHz)
>6.5
>6.5
>12.5
>12.5
>30
>30
560Ω
560Ω
75Ω
1
1
500Ω
3
4
75Ω
75Ω
Output Rate
(MHz)
27
216
27
216
74.25
297
Attenuation
–50 dB @ (MHz)
20.5
209.5
14.5
203.5
44.25
267
500Ω
ADV7344
1
OUTPUT
BNC
OUTPUT
BNC
OUTPUT
BNC
(2x)
(16x)
(1x)
(8x)
(1x)
(4x)