Dac Configurations; Voltage Reference; Video Output Buffer And Optional Output Filter; Figure 128: Example Of Output Filter For Sd, 16× Oversampling - Analog Devices ADV8003 Hardware Manual

8.6. DAC CONFIGURATIONS

The ADV8003 encoder features six DACs which all operate in low-drive mode. Low-drive mode is defined as 4.33 mA full-scale current
into a 300 Ω load, R .
L
The ADV8003 encoder has two R
voltage levels; this is achieved through a resistor connected between the R
must have a value of 4.12 kΩ, and R
tolerance.
The ADV8003 encoder uses two pins for compensating the DAC reference buffer, COMP1 and COMP2. A 2.2 nF capacitor should be
connected from each of these pins to AVDD2.
8.6.1.

Voltage Reference

The ADV8003 contains an on-chip voltage reference that can be used as a board level voltage reference via the V
ADV8003 can be used with an external voltage reference by connecting the reference source to the V
external voltage reference such as the
used, a 0.1 µF capacitor should be connected from the V
8.6.2.

Video Output Buffer and Optional Output Filter

A video buffer is necessary on the DAC outputs to match the 300Ω output impedance of the ADV8003 encoder output to the 75Ω input
impedance of the sink device. ADI produces a range of op amps suitable for this application, for example, the AD8061. For more
information about line driver buffering circuits, refer to the relevant op amp datasheet.
An optional reconstruction (anti-imaging) low-pass filter (LPF) may be required on the ADV8003 encoder processor DAC outputs if the part 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. Refer to Section 8.4.1 for more details on output oversampling.
For applications requiring an output buffer and reconstruction filter, the ADA4430-1, ADA4411-3, and
buffers should be considered.
Rev. B, August 2013
pins which are used to control the full-scale DAC output current and, therefore, the DAC output
SET
must have a value of 300 Ω. The resistors connected to the R
L
AD1580 is used with the ADV8003 encoder reference voltage. If an external voltage reference is not

Table 89: Output Filter Requirements

Application Oversampling
SD 2×
SD 16×
ED 1×
ED 8×
HD 1×
HD 4×
10µH
DAC
OUTPUT
600Ω 22pF
Figure 128: Example of Output Filter for SD, 16× Oversampling
pin and GND. For low-drive operation, both R
SET
pin to AVDD2.
REF
Cutoff Frequency (MHz)
>6.5
>6.5
>12.5
>12.5
>30
>30
3
75Ω
600Ω
1
4
560Ω
560Ω
346
ADV8003 Hardware Manual
and R pins should have a 1%
SET1 SET2
pin. Alternatively, the
REF
pin. For optimal performance, an
REF
ADA4410-6 integrated video filter
Attenuation
–50 dB at
(MHz)
20.5
209.5
14.5
203.5
44.25
267
BNC
OUTPUT
and R
SET1 SET2