Datasheet

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
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
LMP90077, LMP90078, LMP90079, LMP90080
SNAS521F –JULY 2011–REVISED MARCH 2013 www.ti.com
Figure 37. 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) (11)
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 38.
Figure 38. Digital Filter Response for a 3.5717MHz versus 3.6864 MHz XTAL
GPIO (D0–D6)
Pins D0-D6 are general purpose input/output (GPIO) pins that can be used to control external LEDs or switches.
Only a high or low value can be sourced to or read from each pin.
Figure 39 shows a flowchart how these GPIOs can be programmed.
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