User`s manual

80 RabbitCore RCM3400
B.4.3 Analog Features
The Prototyping Board has typical support circuitry installed to complement the ADS7870
A/D converter on the RCM3400 module.
B.4.3.1 A/D Converter Inputs
Figure B-6 shows a pair of A/D converter input circuits. The resistors form an approx.
10:1 attenuator, and the capacitor filters noise pulses from the A/D converter input.
Figure B-6. A/D Converter Inputs
The A/D converter chip can make either single-ended or differential measurements
depending on the value of the opmode parameter in the software function call. Adjacent
A/D converter inputs are paired to make differential measurements. The default setup on
the Prototyping Board is to measure only positive voltages for the ranges listed in Table B-3.
Table B-3. Positive A/D Converter Input Voltage Ranges
Min. Voltage
(V)
Max. Voltage
(V)
Amplifier
Gain
mV per Tick
0.0 +20.0 1 10
0.0 +10.0 2 5
0.0 +5.0 4 2.5
0.0 +4.0 5 2.0
0.0 +2.5 8 1.25
0.0 +2.0 10 1.0
0.0 +1.25 16 0.625
0.0 +1.0 20 0.500
178 kW
ADC_IN0
AGND
+ V
ADC_IN1
ADC
Factory
Default
BVREF =
2.048 V
0 W
178 kW
1 nF
20 kW
20 kW
1 nF
ADC
JP1