Rainbow-electronics ADC1038 Bedienungsanleitung PDF herunterladen (Seite 12)

3.0 Analog Considerations (Continued)

External Reference 2.5V Full Scale

TL/H/10556– 20

Power Supply as Reference

TL/H/10556– 21

Input Not Referred to GND

TL/H/10556– 22

*Current path must still exist from V

(

)

ground

FIGURE 3. Analog Input Options

3.3 REFERENCE AND INPUT

The two V

REF

inputs of the ADC1031/4/8 are fully differen-

tial and define the zero to full-scale input range of the A to D

converter. This allows the designer to easily vary the span

of the analog input since this range will be equivalent to the

voltage difference between V

REF

and V

REF

. By reduc-

ing V

REF

) to less than 5V, the

sensitivity of the converter can be increased (i.e., if V

REF

2V then 1 LSB

1.95 mV). The input/reference arrange-

ment also facilitates ratiometric operation and in many

cases the chip power supply can be used for transducer

power as well as the V

REF

source.

This reference flexibility lets the input span not only be var-

ied but also offset from zero. The voltage at V

REF

sets the

input level which produces a digital output of all zeros.

Though V

is not itself differential, the reference design

allows nearly differential-input capability for many measure-

ment applications.

Figure 3

shows some of the configura-

tions that are possible.

The ADC1031 has no V

REF

pin. V

REF

is internally tied to

GND.

Power Supply Bypassing

TL/H/10556– 23 TL/H/10556– 24

1 2 ... 7 8 9 10 11 12 13 14 15 16 17 18

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