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ADVANCED COMMUNICATIONS & SENSING
USER GUIDE
SX8724SEVK
Evaluation Kit for SX8724S Data Acquisition System
ACS - Revision 1.0 May 2011
© Semtech Corp.
17.5.1 Inputs Configuration
Select the AC3-AC2 analog inputs in differential mode as input chanel. The “Inputs” configuration controls
should look like the picture below
Note: Function of the layout and the used sensor, to avoid crossing sensor Vout+ and Vout- on a board the
SX8724S allows inverting the polarity of the inputs we will use the “sign inversion” feature during SX8724S
configuration.
17.5.2 Rough Gain Configuration
As the transfer function shows, the total span of the sensor is 14.5mV and the total span of the ZoomingADC
is 3.3V (V
BATT
).
The gain that needs to be applied to see the full range of the signal is then calculated as follows:
This means PGA1 gain GD1=10, PGA2 gain GD2=10 and PGA3 gain GD3=2.25 (granularity of PGA3 = 1/12).
Figure 36. SX8724S “Reference” and “Inputs” Groups of Controls
Equation 1
227
5
.
14
3300
=
=
=
mV
mV
SensorOut
ADCOut
Gain
Max
Max
