AD7739 datasheet(21/32 Pages) AD

21 / 32 page

Data Sheet

AD7739

Rev. A | Page 21 of 32

DIGITAL INTERFACE DESCRIPTION

HARDWARE

The AD7739 serial interface can be connected to the host

device via the serial interface in several different ways.

The CS pin can be used to select the AD7739 as one of several

circuits connected to the host serial interface. When CS is high,

the AD7739 ignores the SCLK and DIN signals and the DOUT

pin goes to the high impedance state. When the CS signal is not

used, connect the CS pin to DGND.

The RDY pin can be polled for high-to-low transition or can

drive the host device interrupt input to indicate that the

AD7739 has finished the selected operation and/or new data

from the AD7739 is available. The host system can also wait a

designated time after a given command is written to the device

before reading. Alternatively, the AD7739 status can be polled.

When the RDY pin is not used in the system, leave it as an open

circuit. (Note that the RDY pin is always an active digital

output, that is, it never goes into a high impedance state.)

The RESET pin can be used to reset the AD7739. When not

used, connect this pin to DVDD.

The AD7739 interface can be reduced to just two wires connecting

the DIN and DOUT pins to a single bidirectional data line. The

second signal in this 2-wire configuration is the SCLK signal.

The host system must change the data line direction with

reference to the AD7739 timing specification (see the Bus

Relinquish Time in Table 2). The AD7739 cannot operate in the

continuous read mode in 2-wire serial interface configuration.

All the digital interface inputs are Schmitt triggered; therefore,

the AD7739 interface features higher noise immunity and can

be easily isolated from the host system via optocouplers. Figure 12,

Figure 13, and Figure 14 outline some of the possible host device

interfaces: SPI without using the CS signal (Figure 12), a DSP

interface (Figure 13), and a 2-wire configuration (Figure 14).

Figure 12. AD7739 to Host Device Interface, SPI

Figure 13. AD7739 to Host Device Interface, DSP

Figure 14. AD7739 to Host Device Interface, 2-Wire Configuration

Figure 15. Serial Interface Signals—Registers Access

SCLK

DIN

DOUT

RDY

RESET

DGND

DVDD DVDD

AD7739

SCK

MOSI

MISO

INT

68HC11

03742-0-013

SCLK

DIN

DOUT

RDY

RESET

DVDD

AD7739

SCLK

INT

TFS

RFS

ADSP-2105

03742-0-001

SCLK

DIN

DOUT

RESET

DGND

DVDD

AD7739

P3.1/TxD

P3.0/RxD

8xC51

03742-0-015

DIN

SCLK

DOUT

WRITE

COMMUNICATIONS

READ

ADC STATUS

03742-0-016

AD7739 Datasheet(PDF) 21 Page - Analog Devices

AD7739 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 27 28 29 30 31 32

Datasheet Download

Link URL