Cirrus Logic AN366 - Manual (Page 11)

AN366
AN366REV2 11
Figure 6. Phase Compensation and Phase Offset Error
4.2.2 No Load Power Compensation
There are two power compensations in the CS5480/84/90: active and reactive power offset. When no load
is applied, the average active power register, P
AVG
, and average reactive power register, Q
AVG
, may have
offsets. To remove any remaining active or reactive power, it is necessary to perform the following compen-
sation:
- Apply full scale voltage source
- Apply no load to the current channel(s)
- Start continuous conversion
- Read P
AVG
and Q
AVG
register
- Write -P
AVG
and -Q
AVG
to P
OFF
and Q
OFF
, respectively
0º
Before Calibration V is delayed from I
Delay added to I
8.99º @ 50Hz
10.79º @ 60Hz
4.5º @ 50Hz
5.4º @ 60Hz
-4.5º @ 50Hz
-5.4º @ 60Hz
-8.99º @ 50Hz
-10.79º @ 60Hz
Before Calibration I is delayed from V
Delay added to V
Set CPCC = 11 of 2OWR on V
+ FPCC provides adjustment
Set CPCC = 10 of 1OWR on V
+ FPCC provides adjustment
Clear CPCC = 00
+ FPCC provides adjustment
Set CPCC = 01 of 1OWR on I
+ FPCC provides adjustment