EVAL-AD7983SDZ View Datasheet(PDF) - Analog Devices

Part Name

Description

MFG CO.

EVAL-AD7983SDZ

16-Bit, 1.33 MSPS PulSAR ADC in MSOP/QFN

Analog Devices 

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Data Sheet

CHAIN MODE WITH BUSY INDICATOR

This mode can also be used to daisy-chain multiple AD7983s

on a 3-wire serial interface while providing a busy indicator.

This feature is useful for reducing component count and wiring

connections, for example, in isolated multiconverter applications

or for systems with a limited interfacing capacity. Data

readback is analogous to clocking a shift register.

A connection diagram example using three AD7983s is shown

in Figure 35, and the corresponding timing is given in Figure 36.

AD7983

When SDI and CNV are low, SDO is driven low. With SCK

high, a rising edge on CNV initiates a conversion, selects the

chain mode, and enables the busy indicator feature. In this

mode, CNV is held high during the conversion phase and the

subsequent data readback. When all ADCs in the chain have

completed their conversions, the SDO pin of the ADC closest

to the digital host (see the AD7983 ADC labeled C in Figure 35)

is driven high. This transition on SDO can be used as a busy

indicator to trigger the data readback controlled by the digital

host. The AD7983 then enters the acquisition phase and goes

into standby mode. The data bits stored in the internal shift

register are clocked out, MSB first, by subsequent SCK falling

edges. For each ADC, SDI feeds the input of the internal shift

register and is clocked by the SCK falling edge. Each ADC in the

chain outputs its data MSB first, and 16 × N + 1 clocks are required

to readback the N ADCs. Although the rising edge can be used to

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

a faster reading rate and, consequently, more AD7983s in the

chain, provided the digital host has an acceptable hold time.

CNV

SDI AD7983 SDO

A

SCK

CNV

SDI AD7983 SDO

B

SCK

CNV

SDI AD7983 SDO

C

SCK

CONVERT

DIGITAL HOST

DATA IN

IRQ

CLK

Figure 35. Chain Mode with Busy Indicator Connection Diagram

CNV = SDIA

ACQUISITION

SCK

tHSCKCNV

SDOA = SDIB

SDOB = SDIC

SDOC

tCONV

CONVERSION

tSSCKCNV

tEN

tDSDOSDI

tDSDOSDI

tCYC

tACQ

tSCKH

tSCK

ACQUISITION

1

2

3

4

15

16

17

18

19

31

32

33

34

35

tSSDISCK

tHSDISCK

tSCKL

DA15

tHSDO

DA14 DA13

tDSDO

DA1 DA0

DB15 DB14 DB13

DB1 DB0 DA15 DA14

DA1 DA0

DC15 DC14 DC13

DC1 DC0 DB15 DB14

DB1 DB0 DA15 DA14

Figure 36. Chain Mode with Busy Indicator Serial Interface Timing

47

48

49

tDSDOSDI

tDSDOSDI

tDSDODSI

DA1 DA0

Rev. C | Page 23 of 25

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