REV. 0

AD7738

–19–

MD2

MD1

MD0

Operating Mode

000

Idle Mode

The default mode after Power-On or Reset.

The AD7738 returns to this mode automatically after any calibration or after a single conversion.

001

Continuous Conversion Mode

The AD7738 performs a conversion on the specified channel. After the conversion is complete, the

relevant Channel Data register and Channel Status register are updated, the relevant RDY bit in the

ADC status register is set, and the AD7738 continues converting on the next enabled channel. The AD7738

will cycle through all enabled channels until put into another mode or reset. The cycle period will be the

sum of all enabled channels’ conversion times, set by corresponding Channel Conversion Time registers.

010

Single Conversion Mode

The AD7738 performs a conversion on the specified channel. After the conversion is complete, the

relevant Channel Data register and Channel Status register are updated, the relevant RDY bit in the

ADC status register is set, the

RDY pin goes low, the MD2, MD1, and MD0 bits are reset, and AD7738

returns to the Idle mode. Requesting a single conversion ignores the Channel Setup registers’ Enable bits

and a conversion will be performed even if that channel is disabled.

011

Power-Down (Standby) Mode

The ADC and the analog front end (internal buffer) go into the power-down mode. The AD7738 digital

interface can still be accessed. The CLKDIS bit works separately, the MCLKOUT mode is not affected

by Power-Down (Standby) mode.

100

ADC Zero-Scale Self-Calibration Mode

A zero-scale self-calibration is performed on internally shorted ADC inputs. After the calibration is

complete, the contents of the ADC Zero-Scale Calibration register are updated, all RDY bits in the ADC

status register are set, the

RDY pin goes low, the MD2, MD1, and MD0 bits are reset, and the AD7738

returns to the Idle mode.

101

For Future Use

110

Channel Zero-Scale System Calibration Mode

A zero-scale system calibration is performed on the selected channel. An external system zero-scale

voltage should be provided at the AD7738 analog input and this voltage should remain stable for the

duration of the calibration. After the calibration is complete, the contents of the corresponding Channel

Zero Scale Calibration register are updated, all RDY bits in the ADC status register are set, the

RDY pin

goes low, the MD2, MD1, and MD0 bits are reset, and AD7738 returns to the Idle mode.

111

Channel Full-Scale System Calibration Mode

A full-scale system calibration is performed on the selected channel. An external system full-scale voltage

should be provided at the AD7738 analog input and this voltage should remain stable for the duration of

the calibration. After the calibration is complete, the contents of the corresponding Channel Full-Scale

Calibration register are updated, all RDY bits in the ADC status register are set, the

RDY pin goes low,

the MD2, MD1, and MD0 bits are reset, and AD7738 returns to the Idle mode.