0 200 400 600 800 1000 1200 1400 1600 1800 2000
-120
-80
-40
0
GAIN (dB)
FREQUENCY (Hz)
107.325 SPS
214.65 SPS
30139587
FIGURE 9. Digital Filter Response 107.325 SPS and 214.65 SPS
If the internal CLK is not being used and the external CLK is not 3.5717 MHz, then the filter response would be the same as the
response shown above, but the frequency will change according to the equation:
f
NEW
= [(CLK
EXT
) / 256 ] x (f
OLD
/ 13.952k)
Using the equation above, an example of the filter response for a 3.5717 MHz XTAL versus a 3.6864 MHz XTAL can be seen in
Figure 10.
40 45 50 55 60 65 70
-140
-120
-100
-80
-60
-40
-20
0
GAIN (dB)
FREQUENCY (Hz)
Crystal = 3.5717 MHz
Crystal = 3.6864 MHz
30139556
FIGURE 10. Digital Filter Response for a 3.5717MHz
versus 3.6864 MHz XTAL
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