Datasheet

REV. 0
AD7738
–19–
MD2 MD1 MD0 Operating Mode
000Idle Mode
The default mode after Power-On or Reset.
The AD7738 returns to this mode automatically after any calibration or after a single conversion.
001Continuous 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.
010Single 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.
011Power-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.
100ADC 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.
101For Future Use
110Channel 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.
111Channel 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.