adv7188 Analog Devices, Inc., adv7188 Datasheet - Page 110

• Manufacturer Part Number: adv7188
• Description: Multiformat Sdtv Video Decoder With Fast Switch Overlay Support
• Manufacturer: Analog Devices, Inc.

ADV7188
DIGITAL INPUTS
The digital inputs on the ADV7188 are designed to work with
3.3 V signals and are not tolerant of 5 V signals. Extra compo-
nents are needed if 5 V logic signals are required to be applied
to the decoder.
XTAL AND LOAD CAPACITOR VALUES SELECTION
Figure 51 shows an example reference clock circuit for the
ADV7188. Special care must be taken when using a crystal
circuit to generate the reference clock for the ADV7188. Small
variations in reference clock frequency may cause autodetection
issues and impair the ADV7188 performance.
C1 = 47pF
Figure 51. Crystal Circuit
28.63636MHz
R = 1MΩ
XTAL
C2 = 47pF
Rev. A | Page 110 of 112
Use the following guidelines to ensure correct operation:
•
•
•
To find C1 and C2, use the following formula:
where C
and C
For example, if C
calculated to be 50 pF each, and the nearest standard capacitor
value is 47 pF.
Use a crystal of the correct frequency, 28.63636 MHz.
Tolerance should be 50 ppm or better.
User a parallel-resonant crystal.
Know the C
C1 and C2 capacitors must be calculated using this C
C = 2(C
pg
(pin-to-ground capacitance) is 4 pF for the ADV7188.
stray
is usually 2 pF to 3 pF, depending on board traces,
load
− C
load
load
for the crystal part selected. The values of the
stray
is 30 pF, the values of C1 and C2 are
) − C
pg
load
value.