REV. A

AD7707

–18–

CALIBRATION SEQUENCES

The AD7707 contains a number of calibration options as previously outlined. Table XV summarizes the calibration types, the opera-

tions involved and the duration of the operations. There are two methods of determining the end of calibration. The first is to moni-

tor when DRDY returns low at the end of the sequence. DRDY not only indicates when the sequence is complete, but also that the

part has a valid new sample in its data register. This valid new sample is the result of a normal conversion which follows the calibra-

tion sequence. The second method of determining when calibration is complete is to monitor the MD1 and MD0 bits of the Setup

Register. When these bits return to 0 (0 following a calibration command), it indicates that the calibration sequence is complete.

This method does not give any indication of there being a valid new result in the data register. However, it gives an earlier indication

than DRDY that calibration is complete. The duration to when the Mode Bits (MD1 and MD0) return to 0 00 represents the dura-

tion of the calibration carried out). The sequence to when DRDY goes low also includes a normal conversion and a pipeline delay,

table.

Table XV. Calibration Sequences

Calibration Type

MD1, MD0

Calibration Sequence

Duration to Mode Bits

Duration to

DRDY

DRDY

DRDY

DRDY

DRDY

Self-Calibration

0, 1

Internal ZS Cal @ Selected Gain +

6

× 1/Output Rate

9

× 1/Output Rate + t

P

Internal FS Cal @ Selected Gain

ZS System Calibration

1, 0

ZS Cal on AIN @ Selected Gain

3

× 1/Output Rate

4

× 1/Output Rate + t

P

FS System Calibration

1, 1

FS Cal on AIN @ Selected Gain

3

× 1/Output Rate

4

× 1/Output Rate + t

P