Cirrus Logic AN366 - Manual (Page 37)

AN366
AN366REV2 37
PERFORM AC OFFSET AND READ IRMS
Note: AC offset is only required when IRMS measurements are needed with high dynamic range
(only helpful at very low input levels).AC Offset Calibration Flow Diagram on page 44
SET SAMPLE COUNT
(See Figure 32.)
SDI = 0x90 0x73 0x000FA0 Write SampleCount (page 16, register 51)
SDO = 0xFF 0xFF 0xFFFFFF (4000)
SDI = 0x90 0x33 0xFFFFFF Read SampleCount (page 16, register 51)
SDO = 0xFF 0xFF 0x000FA0 (4000)
Figure 32. Setup Window
READ POWER REGISTERS
(See Figure 33.)
Gain Calibration, Channels 1 and 2, Voltage
SDI =
0x90 0x23 0xFFFFFF Read V1GAIN (page 16, register 35)
SDO = 0xFF 0xFF 0x3C1078 (0.9385054)
SDI = 0x90 0x2A 0xFFFFFF Read V2GAIN (page 16, register 42)
SDO = 0xFF 0xFF 0x3C1751 (0.9389233)
Gain Calibration, Channels 1 and 2, Current
SDI = 0x90
0x21 0xFFFFFF Read I1GAIN (page 16, register 33)
SDO = 0xFF 0xFF 0x1A77A0 (0.4135514)
SDI = 0x90 0x28 0xFFFFFF Read I2GAIN (page 16, register 40)
SDO = 0xFF 0xFF 0x1A78C4 (0.413621)
Offset Calibration, Channels 1 and 2, Current
SDI = 0x90
0x25 0xFFFFFF Read I1ACOFF (page 16, register 37)
SDO = 0xFF 0xFF 0x000000 (0)
SDI = 0x90 0x2C 0xFFFFFF Read I2ACOFF (page 16, register 44)
SDO = 0xFF 0xFF 0x000000 (0)
Offset Calibration, Channels 1 and 2, Active Power Offset
SDI = 0x90
0x24 0xFFFFFF Read P1OFF (page 16, register 36)
SDO = 0xFF 0xFF 0x000000 (0)
SDI = 0x90 0x2B 0xFFFFFF Read P2OFF (page 16, register 43)
SDO = 0xFF 0xFF 0x000000 (0)
Offset Calibration, Channels 1 and 2, Reactive Power Offset
SDI = 0x90
0x26 0xFFFFFF Read Q1OFF (page 16, register 38)
SDO = 0xFF 0xFF 0x000000 (0)
SDI = 0x90 0x2D 0xFFFFFF Read Q2OFF (page 16, register 45)
SDO = 0xFF 0xFF 0x000000 (0)
READ VGAIN,
IGAIN, IACOFF,
POFF, QOFF
PERFORM
AC OFFSET
& READ IRMS
SampleCount =
4,000
12
13