ADV7183AKST Analog Devices Inc, ADV7183AKST Datasheet - Page 100

• Manufacturer Part Number: ADV7183AKST
• Description: IC VIDEO DECODER NTSC 80-LQFP
• Manufacturer: Analog Devices Inc
• Type: Video Decoderr

Specifications of ADV7183AKST

• Applications: Projectors, Recorders, Security
• Voltage - Supply, Analog: 3.15 V ~ 3.45 V
• Voltage - Supply, Digital: 1.65 V ~ 2 V
• Mounting Type: Surface Mount
• Package / Case: 80-LQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

ADV7183A
Digital Inputs
The digital inputs on the ADV7183A were designed to work
with 3.3 V signals, and are not tolerant of 5 V signals. Extra
components are needed if 5 V logic signals are required to be
applied to the decoder.
Antialiasing Filters
For inputs from some video sources that are not bandwidth
limited, signals outside the video band can alias back into the
video band during A/D conversion and appear as noise on the
output video. The ADV7183A oversamples the analog inputs by
a factor of 4. This 54 MHz sampling frequency reduces the
requirement for an input filter; for optimal performance it is
recommended that an antialiasing filter be employed. The
recommended low cost circuit for implementing this buffer and
filter circuit for all analog input signals is shown in Figure 42.
The buffer is a simple emitter-follower using a single npn
transistor. The antialiasing filter is implemented using passive
components. The passive filter is a third-order Butterworth
filter with a −3 dB point of 9 MHz. The frequency response of
the passive filter is shown in Figure 40. The flat pass band up to
6 MHz is essential. The attenuation of the signal at the output of
the filter due to the voltage divider of R24 and R63 is compen-
sated for in the ADV7183A part using the automatic gain
control. The ac coupling capacitor at the input to the buffer
creates a high-pass filter with the biasing resistors for the
transistor. This filter has a cut-off of
It is essential that the cutoff of this filter be less than 1 Hz to
ensure correct operation of the internal clamps within the part.
These clamps ensure that the video stays within the 5 V range of
the op amp used.
{2 × π × ( R39 || R89 ) × C93 }
–100
–120
–20
–40
–60
–80
100kHz
0
Figure 40. Third-Order Butterworth Filter Response
300kHz
1MHz
3MHz
FREQUENCY
10MHz
–1
= 0.62 Hz
30MHz
100MHz
300MHz
1GHz
Rev. B | Page 100 of 104
XTAL AND LOAD CAPACITOR VALUE SELECTION
Figure 41 shows an example reference clock circuit for the
ADV7183A. Special care must be taken when using a crystal
circuit to generate the reference clock for the ADV7183A. Small
variations in reference clock frequency may cause autodetection
issues and impair the ADV7183A performance.
Use the following guidelines to ensure correct operation:
•
•
•
value of Capacitors C1 and C2 must match C
specific crystal part number in the user’s system.
To find C
C1 = C2 = 2C
where C
Example:
C
C1 = 33 pF
C2 = 33 pF
Use the correct frequency crystal, which is 27 MHz.
Tolerance should be 50 ppm or better.
Use a parallel-resonant crystal.
Know the C
load
= 20 pF
stray
load
is 3pF to 8 pF, depending on board traces.
load
, use the following formula:
load
for the crystal part number selected. The
33pF
Figure 41. Crystal Circuit
– C
stray
27 MHz
XTAL
33pF
load
for the