TC65 Terminal Hardware Interface Description
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TC65 Terminal_HD_V02.000b
Page 41 of 65
2007-02-19
3.10.5 Analog-to
Digital Converter (ADC)
The two balanced analog inputs are used for measuring external DC voltages in a range of
0V to 5.0V.
Note:
Only positive differential voltage can be handled because of the input requirement of
ADC.
Table 16: ADC signal description
Signal name
Pin
Description
ADC1_IN_N 22
Negative
voltage
ADC1_IN_P
21
Positive voltage (must be more positive than ADC1_IN_N)
ADC2_IN_N 10
Negative
voltage
ADC2_IN_P
9
Positive voltage (must be more positive than ADC2_IN_N)
Figure 13: ADC balanced amplifier
Use the command AT^SRADC described in [1] to configure the analog inputs and to get the
measurement results.
Note: It is necessary to recalculate measurement results because an amplifier is used to
scale down the ADCx_IN input voltage of the TC65 Terminal (5V) to the ADCx_IN input
voltage of the in-built TC65 module (2.4V).
Two parameters (determined and stored by factory) have to be used for offset compensation
and for consideration of gain and tolerances:
Use the command AT^SAADC described in [1] to read out the required parameters:
<ofsx>: Offset
<ampx> :
Amplification factor (Gain*4096) x=1 for Input 1 or 2 for input 2
To recalculate the exact voltages [mV] measured at the ADCx_IN input use the following
equation:
Value[mV] = (<value> from AT^SRADC - <ofsx>) * <ampx> / 4096
Cellular
Engine
TC65
ADCx_IN
2,3
56
AGND
ADCx_IN_N
ADCx_IN_P
GPIO-
Connector
22,10
21,9
Gain = appr. 0.48
0V...5.0V
0V...2.4V
6V transil diods
for ESD protection
475k
475k
2x150k
G=2
