AD7798 datasheet(20/28 Pages) AD

20 / 28 page

AD7798/AD7799

Data Sheet

Rev. B | Page 20 of 28

Single-Conversion Mode

In single-conversion mode, the AD7798/AD7799 is placed in

power-down mode after conversions. When a single conversion

is initiated by setting MD2, MD1, and MD0 to 0, 0, and 1 in the

mode register, the AD7798/AD7799 powers up, performs a

single conversion, and then returns to power-down mode. The

on-chip oscillator requires approximately 1 ms to power up. A

conversion requires a time period of 2 × tADC. DOUT/RDY goes

low to indicate the completion of a conversion. When the data-

word has been read from the data register, DOUT/RDY goes

high. If CS is low, DOUT/RDY remains high until another

conversion is initiated and completed. The data register can be

read several times if required, even when DOUT/RDY is high.

Continuous-Conversion Mode

This is the default power-up mode. The AD7798/AD7799

continuously converts, with the RDY bit in the status register

going low each time a conversion is complete. If CS is low, the

DOUT/RDY line also goes low when a conversion is complete.

To read a conversion, the user can write to the communication

pin as soon as SCLK pulses are applied to the ADC. DOUT/RDY

returns high when the conversion is read. The user can reread

this register if required. However, the user must ensure that the

data register is not accessed at the completion of the next

conversion, or the new conversion word is lost.

DIN

0x08

0x200A

DATA

SCLK

DOUT/RDY

0x58

Figure 16. Single Conversion

DIN

SCLK

DOUT/RDY

0x58

DATA

Figure 17. Continuous Conversion

AD7798 Datasheet(PDF) 20 Page - Analog Devices