AD7982 datasheet(21/26 Pages) AD

21 / 26 page

AD7982

Data Sheet

Rev. D | Page 20 of 25

CS MODE, 4-WIRE WITHOUT BUSY INDICATOR

CS mode, 4-wire without busy indicator is usually used when

multiple AD7982 devices are connected to an SPI-compatible

digital host.

A connection diagram example using two AD7982 devices is

shown in Figure 33, and the corresponding timing is given in

Figure 34.

With SDI high, a rising edge on CNV initiates a conversion,

selects the CS mode, and forces SDO to high impedance. In this

mode, CNV must be held high during the conversion phase and

the subsequent data readback. If SDI and CNV are low, SDO is

driven low. Prior to the minimum conversion time, SDI can

select other SPI devices, such as analog multiplexers, but SDI

must be returned high before the minimum conversion time

elapses and then held high for the maximum possible

conversion time to avoid the generation of the busy signal

indicator.

When the conversion completes, the AD7982 enters the

acquisition phase and powers down. Each ADC result can be

read by bringing its SDI input low, which consequently outputs

the MSB onto SDO. The remaining data bits are then clocked by

subsequent SCK falling edges. The data is valid on both SCK

edges. Although the rising edge can capture the data, a digital

host using the SCK falling edge allows a faster reading rate,

provided it has an acceptable hold time. After the 18th SCK

falling edge or when SDI goes high (whichever occurs first), SDO

returns to high impedance and another AD7982 can be read.

AD7982

SDI

SDO

CNV

SCK

CONVERT

DATA IN

CLK

DIGITAL HOST

CS1

CS2

AD7982

SDI

SDO

CNV

SCK

Figure 33. CS Mode, 4-Wire Without Busy Indicator Connection Diagram

SDO

D17

D16

D15

tDIS

SCK

tHSDO

tDSDO

tEN

CONVERSION

ACQUISITION

tCONV

tCYC

tACQ

ACQUISITION

SDI(CS1)

CNV

tSSDICNV

tHSDICNV

tSCK

tSCKL

tSCKH

D17

D16

SDI(CS2)

Figure 34. CS Mode, 4-Wire Without Busy Indicator Serial Interface Timing

AD7982 Datasheet(PDF) 21 Page - Analog Devices

AD7982 Datasheet(HTML) 21 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

Datasheet Download

Link URL