adc122s706eb National Semiconductor Corporation, adc122s706eb Datasheet - Page 21

• Manufacturer Part Number: adc122s706eb
• Description: Dual 12-bit, 500 Ksps To 1 Msps, Simultaneous Sampling A/d Converter
• Manufacturer: National Semiconductor Corporation

6.0 APPLICATION CIRCUITS
The following figures are examples of the ADC122S706 in
typical application circuits. These circuits are basic and will
generally require modification for specific circumstances.
6.1 Data Acquisition
Figure 12 shows a basic low cost, low power data acquisition
circuit. The analog and digital supply pins are powered by the
system +5V supply and the 2.5V reference voltage is gener-
ated by the LM4040-2.5 shunt reference.
FIGURE 12. Low cost, low power Data Acquisition
System
FIGURE 13. Interfacing the ADC122S706 to a Current Transducer
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6.2 Current Sensing Application
Figure 13 shows an example of interfacing a pair of current
transducers to the ADC122S706. The current transducers
convert an input current into a voltage that is converted by the
ADC. Since the output voltage of the current transducers are
single-ended and centered around a common-mode voltage
of 2.5V, the ADC122S706 is configured with the output of the
transducer driving the non-inverting inputs and the common-
mode output voltage of the transducer driving the inverting
input. The output of the transducer has an output range of ±2V
around the common-mode voltage of 2.5V. As a result, a se-
ries reference voltage of 2.0V is connected to the AD-
C122S706. This will allow all of the codes of the ADC122S706
to be available for the application. This configuration of the
ADC122S706 is referred to as a single-ended application of
a differential ADC. All of the elements in the application are
conveniently powered by the same +5V power supply, keep-
ing circuit complexity and cost to a minimum.
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