AD7694 datasheet(19/24 Pages) AD

19 / 24 page

Data Sheet

AD7988-1/AD7988-5

Rev. B | Page 19 of 24

CS MODE 4-WIRE

This mode is typically used when multiple AD7988-x devices

are connected to an SPI-compatible digital host.

A connection diagram example using two AD7988-x devices is

shown in Figure 36, and the corresponding timing is given in

Figure 37.

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 be

used to 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 conversion time.

When the conversion is complete, the AD7988-x 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 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 time. After

the 16th SCK falling edge or when SDI goes high, whichever is

earlier, SDO returns to high impedance and another AD7988-x

can be read.

DIGITAL HOST

CONVERT

CLK

DATA IN

AD7988-1/

AD7988-5

SDO

CNV

SCK

AD7988-1/

AD7988-5

SDO

CNV

SCK

CS1

CS2

SDI

Figure 36. 4-Wire CS Mode Connection Diagram

tCONV

tCYC

ACQUISITION

tACQ

tSCK

tSCKH

tSCKL

CONVERSION

SCK

CNV

tSSDICNV

tHSDICNV

SDO

D15

D13

D14

D15

D14

tHSDO

tEN

tDSDO

tDIS

SDI (CS1)

SDI (CS2)

Figure 37. 4-Wire CS Mode Serial Interface Timing

AD7694 датащи(PDF) 19 Page - Analog Devices

AD7694 датащи(HTML) 19 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

датащи скачать

ссылки URL