TXMC638 User Manual Issue 1.0.2
Page 60 of 86
9 Installation
I/O Interface
9.1
9.1.1 Front I/O - ADC Analog Input Level
All analog inputs are connected via an impedance converter and a second operation amplifier for level
adjustment and filtering to the differential ADC inputs. This also serves as a protection of the ADC from
excessive analog input levels.
Diff. Source with Ground Reference
Diff. Source without Ground Reference
Vin
LTC2323
COM
+3.3V
ADC_INx-
VIN
+
-
-
+
+3.3V
COM
LTC2323
Vin
ADC_INx-
VIN
Maximum VIN = ±5.0V
Maximum VIN = ±5.0V
The TXMC638 has differential analog inputs. When talking about the input voltage range of a differential
input, one has to differentiate between the differential input voltage between the two pins, and the input
voltage relative to ground for each pin.
With an input voltage range of ±2.5V (ground related) for each pin of the differential input, we get the ±5.0V
differential input voltages:
Voltage
Description
TXMC638
V
diff_max
Maximum differential input voltage (range)
±5.0 V
V
cm_max
Maximum common mode input voltage (range)
±7.5 V
V
in_max
Operating voltage range of the input pins
±10.0 V
V
in_abs
Absolute maximum voltage range of the input
Power Off: ±5.0 V
Power On: ±18.5 V
Table 9-1 : Differential Input Voltage Ranges
The range of this differential input is -5V to +5V, which results to a full scale range of 10V for the ±2.5V (per
pin, relative to ground) Input voltage range.
