ADA4412-3ARQZ-RL Analog Devices Inc, ADA4412-3ARQZ-RL Datasheet - Page 11

• Manufacturer Part Number: ADA4412-3ARQZ-RL
• Description: IC,TV/VIDEO CIRCUIT,TV/Video Filter,SSOP,20PIN,PLASTIC
• Manufacturer: Analog Devices Inc
• Type: Video Filterr

Specifications of ADA4412-3ARQZ-RL

• Applications: Set-Top Boxes, Video Players
• Mounting Type: Surface Mount
• Package / Case: 20-QSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

INPUT AND OUTPUT COUPLING
Inputs to the ADA4412-3 are normally dc-coupled. Ac coupling
the inputs is not recommended; however, if ac coupling is
necessary, suitable circuitry must be provided following the ac
coupling element to provide proper dc level and bias currents at
the ADA4412-3 input stages. The ADA4412-3 outputs can be
either ac- or dc-coupled.
When driving single ac-coupled loads in standard 75 Ω video
distribution systems, 220 μF coupling capacitors are
recommended for use on all but the chrominance signal output.
Since the chrominance signal is a narrow-band modulated
carrier, it has no low frequency content and can therefore be
coupled with a 0.1 μF capacitor.
There are two ac coupling options when driving two loads from
one output. One simply uses the same value capacitor on the
second load, while the other is to use a common coupling
capacitor that is at least twice the value used for the single load
(see Figure 18 and Figure 19).
When driving two parallel 150 Ω loads (75 Ω effective load),
the 3 dB bandwidth of the filters typically varies from that of
the filters with a single 150 Ω load. For the 9 MHz and 18 MHz
filters, the typical variation is within ±1.0%; for the 36 MHz
filters, the typical variation is within ±2.5%.
Figure 17. Flexible Circuits to Set the LEVEL1 and LEVEL2 Inputs to
9.53kΩ
9.53kΩ
9.09kΩ
10kΩ
634Ω
1kΩ
1kΩ
Figure 16. Generating Fully Adjustable Output Offsets
+5V
+5V
–5V
+5V
Obtain a 600 mV Output Offset on a Single Supply
SINGLE SUPPLY
0.1μF
0.1μF
DUAL SUPPLY
0.1μF
LEVEL1
LEVEL1
LEVEL1
9.53kΩ
9.53kΩ
9.09kΩ
DNP
1kΩ
1kΩ
0Ω
+5V
+5V
–5V
+5V
0.1μF
0.1μF
DNP
LEVEL2
LEVEL2
LEVEL2
Rev. 0 | Page 11 of 16
PRINTED CIRCUIT BOARD LAYOUT
As with all high speed applications, attention to printed
circuit board layout is of paramount importance. Standard high
speed layout practices should be adhered to when designing
with the ADA4412-3. A solid ground plane is recommended,
and surface-mount, ceramic power supply decoupling
capacitors should be placed as close as possible to the supply
pins. All of the ADA4412-3 GND pins should be connected to
the ground plane with traces that are as short as possible.
Controlled impedance traces of the shortest length possible
should be used to connect to the signal I/O pins and should not
pass over any voids in the ground plane. A 75 Ω impedance
level is typically used in video applications. All signal outputs of
the ADA4412-3 should include series termination resistors
when driving transmission lines.
When the ADA4412-3 receives its inputs from a device
with current outputs, the required load resistor value for
the output current is often different from the characteristic
impedance of the signal traces. In this case, if the interconnec-
tions are sufficiently short (<< 0.1 wavelength), the trace does
not have to be terminated in its characteristic impedance.
Traces of 75 Ω can be used in this instance, provided their
lengths are an inch or two at the most. This is easily achieved
because the ADA4412-3 and the device feeding it are usually
adjacent to each other, and connections can be made that are
less than one inch in length.
VIDEO ENCODER RECONSTRUCTION FILTER
The ADA4412-3 is easily applied as a reconstruction filter at the
DAC outputs of a video encoder. Figure 20 illustrates how to use
the ADA4412-3 in this type of application with an ADV7322 video
encoder in a single-supply application with ac-coupled outputs.
Figure 19. Driving Two AC-Coupled Loads with One Common Coupling Capacitor
Figure 18. Driving Two AC-Coupled Loads with Two Coupling Capacitors
ADA4412-3
ADA4412-3
470μF
75Ω
75Ω
75Ω
75Ω
220μF
220μF
CABLE
CABLE
75Ω
75Ω
CABLE
CABLE
75Ω
75Ω
ADA4412-3
75Ω
75Ω
75Ω
75Ω