Analog Features (Rcm4200 Only); A/D Converter Inputs - Rabbit RabbitCore RCM4200 User Manual

B.4.3 Analog Features (RCM4200 only)
The Prototyping Board has typical support circuitry installed to complement the ADS7870
A/D converter on the RCM4200 model (the A/D converter is not available on the
RCM4210 model).
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. 11:1
attenuator, and the capacitor filters noise pulses from the A/D converter input. The 470 Ω
inline jumpers allow other configurations (see Table B-6) and provide digital isolation when
you are not using an A/D converter (Parallel Port D is available). These jumpers optimize
using RabbitCore modules with or without A/D converters—if you are designing your own
circuit, the best performance for the A/D converter would be realized with 0 Ω resistors.
LN0_IN
LN1_IN
AGND
The A/D converter chip can make either single-ended or differential measurements
depending on the value of the
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
(with prescaler)
(V)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
110
Inline jumpers are
470 W resistors
100 kW
100 kW
2.2 nF 2.2 nF
Figure B-6. A/D Converter Inputs
parameter in the software function call. Adjacent
opmode
Max. Voltage
Multiplier
(V)
+22.528
+11.264
+5.632
+4.506
+2.816
+2.253
+1.408
+1.126
ADC
(RCM4200)
ADC
JP23/JP24
3
1
Gain A/D Converter
Actual Gain
×1 1
×2 1.8
×4 3.6
×5 4.5
×8 7.2
×10 9.0
×16 14.4
×20 18
BVREF =
2.048 V
Resolution
(mV)
11
5.5
2.75
2.20
1.375
1.100
0.688
0.550
RabbitCore RCM4200