AD7989-5BCPZ-R2 datasheet(14/24 Pages) ETC2

14 / 24 page

AD7989-1/AD7989-5

Data Sheet

Rev. 0 | Page 14 of 24

Transfer Functions

The ideal transfer characteristic for the AD7989-1/AD7989-5 is

shown in Figure 25 and Table 7.

Figure 25. ADC Ideal Transfer Function

Table 7. Output Codes and Ideal Input Voltages

Description

Analog Input

VREF = 5 V

Digital Output

Code (Hex)

+FSR – 1 LSB

+4.999962 V

0x1FFFF1

Midscale + 1 LSB

+38.15 µV

0x00001

Midscale

0 V

0x00000

Midscale – 1 LSB

−38.15 µV

0x3FFFF

–FSR + 1 LSB

−4.999962 V

0x20001

–FSR

−5 V

0x200002

This is also the code for an overranged analog input (VIN+ − VIN− above VREF − VGND).

This is also the code for an underranged analog input (VIN+ − VIN− below VGND).

TYPICAL CONNECTION DIAGRAM

Figure 26 shows an example of the recommended connection

diagram for the AD7989-1/AD7989-5 when multiple supplies

are available.

Figure 26. Typical Application Diagram with Multiple Supplies

100...000

100...001

100...010

011...101

011...110

011...111

ANALOG INPUT

+FSR – 1.5 LSB

+FSR – 1 LSB

–FSR + 1 LSB

–FSR

–FSR + 0.5 LSB

2.7nF

20Ω

V–

0V TO VREF

V+

2.7nF

20Ω

V–

VREF TO 0V

V+

10µF2

REF1

REF

VDD

VIO

GND

IN+

IN–

SCK

SDO

CNV

AD7989-1/

AD7989-5

100nF

3-WIRE INTERFACE

2.5V

1.8V TO 5.5V

V+

ADA4841-x2, 3

1SEE THE VOLTAGE REFERENCE INPUT SECTION FOR REFERENCE SELECTION.

2CREF IS USUALLY A 10µF CERAMIC CAPACITOR (X5R).

SEE THE RECOMMENDED LAYOUT IN FIGURE 39 AND FIGURE 40.

3SEE THE DRIVER AMPLIFIER CHOICE SECTION.

4OPTIONAL FILTER. SEE THE ANALOG INPUTS SECTION.

SDI/CS

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