Cirrus Logic AN366 - Manual (Page 14)

AN366
14 AN366REV2
5.2 Full Calibration and Compensation Procedure (Performed Once at Factory)
The following procedure shows the steps required to perform calibration and compensation. A flow chart show-
ing the full calibration procedure is shown in Figure 5.
1. Power up the CS5480/84/90 device.
2. Reset the CS5480/84/90 device.
3. Verify the register checksum to confirm the reset is successful.
4. Restore configuration and control registers.
5. Connect the reference line voltage and load current to the meter with a phase angle of 60º current lagging.
6. If the reference load current is not the full load, set the Scale register to a ratio of 0.6  2 23 reference load
current ÷ full scale current. See Non-full-scale Gain Calibration on page 9 if the reference line voltage is
lower than the maximum line voltage.
7. Perform continuous conversion (0xD5 command) for 2 seconds.
8. Stop the continuous conversion (0xD8 instruction).
9. Read I
RMS
, V
RMS
, P
AVG
, and PF, and confirm the reference voltage and current signals are correctly
attached by verifying if the I
RMS
, V
RMS
, P
AVG
, and PF are in a reasonable range.
10. Clear DRDY status bit.
11. Send AC gain calibration command (0xFE) to the CS5480/84/90.
12. Wait for DRDY to be set.
13. If needed, perform phase compensation, AC offset calibration, and power offset correction.
14. Send continuous conversion (0xD8 command).
15. Verify measurement accuracy. Check the setup or fail the meter if the accuracy is not within specifications.
16. Read V
GAIN
, I
GAIN
, I
ACOFF
, P
OFF
, Q
OFF
, PC, and register checksum and save them into flash/eeprom.
17. Calibration completed.