Data Sheet

AD7989-1/AD7989-5

CS MODE, 3-WIRE

This mode is usually used when a single AD7989-1/AD7989-5

is connected to an SPI-compatible digital host. The connection

diagram is shown in Figure 31, and the corresponding timing is

given in Figure 32.

With SDI/CS tied to VIO, a rising edge on CNV initiates a

conversion, selects the CS mode, and forces SDO to high

impedance. When the conversion is complete, the AD7989-1/

AD7989-5 enter the acquisition phase and power down. When

CNV goes low, the MSB is output onto SDO. The remaining data

bits are clocked by subsequent SCK falling edges. The data is valid

on both SCK edges. Although the rising edge can be used to

capture the data, a digital host using the SCK falling edge allows

a faster reading rate, provided that it has an acceptable hold

(whichever occurs first), SDO returns to high impedance.

Figure 31. CS Mode, 3-Wire Connection Diagram (SDI High)

Figure 32. CS Mode, 3-Wire Serial Interface Timing (SDI High)

AD7989-1/

AD7989-5

SDO

CNV

SCK

CONVERT

DATA IN

CLK

DIGITAL HOST

VIO

SDI/CS

SDO

D17

D16

D15

D1

D0

SCK

1

2

3

16

17

18

CNV

CONVERSION

ACQUISITION

ACQUISITION

SDI/CS = 1

Rev. A | Page 17 of 24