AD7631BSTZ datasheet(18/32 Pages) AD

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AD7631

Rev. A | Page 18 of 32

TRANSFER FUNCTIONS

Using the D0/OB/2C digital input or via the configuration

offers two output codings: straight binary and twos

complement. See

and

for the ideal transfer

characteristic and digital output codes for the different analog

input ranges, VIN. Note that when using the configuration

Figure 26

Table 8

2C input is a don’t care and should be tied

to either high or low.

000...000

000...001

000...010

111...101

111...110

111...111

ANALOG INPUT

+FSR – 1.5 LSB

+FSR –1LSB

–FSR + 1 LSB

–FSR

–FSR + 0.5 LSB

Figure 26. ADC Ideal Transfer Function

TYPICAL CONNECTION DIAGRAM

Figure 27 shows a typical connection diagram for the AD7631

using the internal reference, serial data interface, and serial

configuration port. Different circuitry from that shown in

Figure 27 is optional and is discussed in the following sections.

Table 8. Output Codes and Ideal Input Voltages

VREF = 5 V

Digital Output Code

Description

VIN = 0 V to 5 V

(10 V p-p)

VIN = 0 V to 10 V

(20 V p-p)

VIN = ±5 V

(20 V p-p)

VIN = ±10 V

(40 V p-p)

Straight Binary

Twos Complement

FSR − 1 LSB

+4.999962 V

+9.999924 V

+19.999847 V

0x3FFFF1

0x1FFFF1

FSR − 2 LSB

+4.999924 V

+9.999847 V

+19.999695 V

0x3FFFE

0x1FFFE

Midscale + 1 LSB

+38.15 μV

−76.29 μV

+152.59 μV

0x20001

0x00001

Midscale

0 V

0x20000

0x00000

Midscale − 1 LSB

−38.15 μV

−76.29 μV

−152.59 μV

0x1FFFF

0x3FFFF

−FSR + 1 LSB

−4.999962 V

−9.999924 V

−19.999847 V

0x00001

0x20001

−FSR

−5 V

−10 V

−20 V

0x000002

0x200002

1 This is also the code for overrange analog input.

2 This is also the code for underrange analog input.

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