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Data Sheet

AD4684/AD4685

MODES OF OPERATION

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RESOLUTION BOOST

The default conversion result output data size for the AD4684/

AD4685 is 16 bits. When the on-chip oversampling function is

enabled, the performance of the ADC can exceed the 16-bit level.

To accommodate the performance boost, it is possible to enable an

additional two bits of resolution. If the RES bit in the CONFIGURA-

TION1 register is set to Logic 1, and the AD4684/AD4685 are in a

valid oversampling mode, the conversion result size is 18 bits for

the AD4684/AD4685. In this mode, 18 SCLK cycles are required to

propagate the data for the AD4684/AD4685. Figure 38 shows the

resolution boost diagram.

Figure 38. Resolution Boost

ALERT

The alert functionality is an out of range indicator and can

be used as an early indicator of an out of bounds con-

version result. An alert event triggers when the conversion

result value register exceeds the alert high limit value in

the ALERT_HIGH_THRESHOLD register, or falls below the

alert low limit value in the ALERT_LOW_THRESHOLD regis-

ter. The ALERT_HIGH_THRESHOLD register and the ALERT_

LOW_THRESHOLD register are common to all ADCs. Detailed

alert information is accessible in the Alert Register section. The

the high limit and the other to the low limit. A logical OR of alert

signals for all ADCs creates a common alert value. This value

can be configured to drive out on the ALERT function of the SDOB/

ALERT pin. The SDOB/ALERT pin is configured as ALERT by

configuring the following bits in the CONFIGURATION1 register and

the CONFIGURATION2 register:

►

Set the SDO bit to 1.

►

Set the ALERT_EN bit to 1.

In addition, set a valid value to the ALERT_HIGH_THRESHOLD

The alert indication function is available in oversampling and in

nonoversampling modes.

The ALERT function of the SDOB/ALERT pin is updated at the end

of conversion. The alert indication status bits in the alert register

update as well and must be read before the end of the next

conversion. The ALERT function of the SDOB/ALERT pin is cleared

with a falling edge of CS. Issuing a software reset also clears the

alert status in the alert register.

Figure 39 shows the alert operation.

Figure 39. Alert Operation

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