Cirrus Logic CRD5490 - Manual (Page 34)

CRD5490-Z
34 DS988RD1
Current Scale Register
To perform calibration with less than full scale load without using the above procedure, it is possible to set the current
channel's Scale register. The current channel calibration data path contains a Scale register (page 18, address 63)
that can be adjusted before calibration to accommodate the non-full-scale load.
where:
I
SCALE
Value stored in the SCALE register before calibration
I
MAX
Maximum current of the meter defined by the customer
I
REF
Load current before calibration, as measured with a reference meter, assuming stable
input
Follow the steps below to set the current channel’s Scale register.
1. Set the load current, I
REF
(assuming V
REF
is set to full scale).
2. Confirm that the reference meter shows V
REF
and I
REF
of the input.
3. Set I
SCALE
per Equation 3.
4. Send the calibration command.
5. After calibration, the meter will be adjusted for a full-scale voltage of V
MAX
and I
MAX
and will currently be mea-
suring the V
REF
and I
REF
measurements.
6. The Scale register is not in the normal data path but instead in the calibration path.
I
SCALE
I
REF
I
MAX
------------ 0.6  2
23
 = [Eq: 3]