AD7663AST datasheet(13/25 Pages) AD

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REV. B

AD7663

–12–

SWA

COMP

SWB

IND

REF

REFGND

LSB

MSB

32,768C

INGND

16,384C

CONTROL

LOGIC

SWITCHES

CONTROL

BUSY

OUTPUT

CODE

INC

INA

INB

CNVST

65,536C

Figure 3. ADC Simplified Schematic

Table III. Output Codes and Ideal Input Voltages

Digital Output

Code (Hexa)

Straight Twos

Description

Analog Input

Binary

Complement

Full-Scale Range

±10 V

±5 V

±2.5 V

0 V to 10 V

0 V to 5 V

0 V to 2.5 V

Least Significant Bit 305.2 µV

152.6 µV

76.3 µV

152.6 µV

76.3 µV

38.15 µV

FSR – 1 LSB

9.999695 V

4.999847 V

2.499924 V

9.999847 V

4.999924 V 2.499962 V

FFFF

7FFF

Midscale + 1 LSB

305.2 µV

152.6 µV

76.3 µV

5.000153 V

2.570076 V 1.257038 V

8001

0001

Midscale

0 V

5 V

2.5 V

1.25 V

8000

0000

Midscale – 1 LSB

–305.2 µV

–152.6 µV

–76.3 µV

4.999847 V

2.499924 V 1.249962 V

7FFF

FFFF

–FSR + 1 LSB

–9.999695 V –4.999847 V –2.499924 V 152.6 µV

76.3 µV

38.15 µV

0001

8001

–FSR

–10 V

–5 V

–2.5 V

0 V

0000

8000

NOTES

1Values with REF = 2.5 V, with REF = 3 V, all values will scale linearly.

2This is also the code for an overrange analog input.

3This is also the code for an underrange analog input.

000...000

000...001

000...010

111...101

111...110

111...111

ANALOG INPUT

+FS – 1.5 LSB

+FS – 1 LSB

–FS + 1 LSB

–FS

–FS + 0.5 LSB

Figure 4. ADC Ideal Transfer Function

Transfer Functions

Using the OB/

2C digital input, the AD7663 offers two output

codings: straight binary and twos complement. The ideal transfer

characteristic for the AD7663 is shown in Figure 4 and Table III.

TYPICAL CONNECTION DIAGRAM

Figure 5 shows a typical connection diagram for the AD7663.

Different circuitry shown on this diagram is optional and is

discussed in the figure’s notes.

Analog Inputs

The AD7663 is specified to operate with six full-scale analog

input ranges. Connections required for each of the four analog

inputs, IND, INC, INB, and INA, and the resulting full-scale

ranges are shown in Table I. The typical input impedance for

each analog input range is also shown.

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