ADC10731, ADC10732, ADC10734, ADC10738

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SNAS081D – MAY 1999 – REVISED MARCH 2013

Figure 39. Detailed Diagram of the ADC10738 DAC and Analog Multiplexer Stages

APPLICATIONS INFORMATION

Multiplexer Configuration

The design of these converters utilizes a sampled-data comparator structure, which allows a differential analog

input to be converted by the successive approximation routine.

The actual voltage converted is always the difference between an assigned “+” input terminal and a “

−” input

terminal. The polarity of each input terminal or pair of input terminals being converted indicates which line the

converter expects to be the most positive.

A unique input multiplexing scheme has been utilized to provide multiple analog channels. The input channels

can be software configured into three modes: differential, single-ended, or pseudo-differential. Analog Input

Multiplexer Options illustrates the three modes using the 4-channel MUX of the ADC10734. The eight inputs of

the ADC10738 can also be configured in any of the three modes. The single-ended mode has CH0–CH3

assigned as the positive input with COM serving as the negative input. In the differential mode, the ADC10734

channel inputs are grouped in pairs, CH0 with CH1 and CH2 with CH3. The polarity assignment of each channel

in the pair is interchangeable. Finally, in the pseudo-differential mode CH0–CH3 are positive inputs referred to

COM which is now a pseudo-ground. This pseudo-ground input can be set to any potential within the input

common-mode range of the converter. The analog signal conditioning required in transducer-based data

acquisition systems is significantly simplified with this type of input flexibility. One converter package can now

handle ground-referred inputs and true differential inputs as well as signals referred to a specific voltage.

without degrading conversion accuracy. If the voltage on an unselected channel exceeds these limits it may

corrupt the reading of the selected channel.

Reference Considerations

REF

REF

REF

systems requiring absolute accuracy. The reference pins must be connected to a voltage source capable of

driving the minimum reference input resistance of 5 k

Ω.

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Product Folder Links: ADC10731 ADC10732 ADC10734 ADC10738