Datasheet

90E32AS ENHANCED POLY-PHASE HIGH-PERFORMANCE WIDE-SPAN ENERGY METERING IC
Function Description 29 April 2, 2013
3.9 EXTERNAL COMPONENT COMPENSATION
The calibrated channel gain and phase-delay offset could be tuned
with respect to some reference parameter. This feature is useful when
external component is not ideal and allow low cost sensors used in the
system.
There are three reference parameters:
• Measured Current RMS (per phase)
• Measured line frequency (all phase in common)
• Measured temperature
There are two tuning parameters to compensate:
• Channel gain compensation
• Channel phase delay compensation
Following are the compensation correspondences:
• Measured current RMS is per phase. It goes to Igain and Phi for
each phase.
• This is to compensate the non-linearity of current sensors, like a
Current-Transformer. Non-linearity can be gain-nonlinearity or
phase nonlinearity. The gain nonlinearity is compensated by
Igain compensation and phase nonlinearity is compensated by
phase compensation.
• Frequency compensation only goes to Phi/Delay (all phases are
the same).
• Temperature compensation only goes to UGain (per phase).
3.9.1 GAIN BASED COMPENSATION
The channel gain can be tuned automatically according to measured
temperature and current RMS.
Here
Log(x) = Log
2
(x)*16, e.g.: Log(2) = 16, Log(16) = 64
• Gain0 is the calibrated Gain at nominal condition,
• GainIrms is the gain adjustment per Irms change (8 bit)
• Irms_ref is the reference current RMS
• GainIrms_offset is the offset for segment calibration
• UGain0 is the calibrated Gain at nominal temperature
• UGainT is the gain adjustment per temperature degree change,
• T0 is the nominal temperature,
If (Irms > Irms0)
GainIrms = GainIrms0,
Irms_ref = Irms0,
GainIrms_offset = 0,
If (Irms1<Irms < Irms0)
GainIrms = GainIrms1,
Irms_ref = Irms0,
GainIrms_offset = 0,
If (Irms < Irms1)
GainIrms = GainIrms2,
Irms_ref = Irms1
Table-4 Compensation Related Registers
Parameter Describtion Registers
LogIrms Measured Current RMS LOGIrms0, LOGIrms1
F0 Nominal line frequency F0
T0 Nominal temperature T0
GainIrms Gain compensation for Irms
GainAIrms01, GainAIrms2,
GainBIrms01, GainBIrms2,
GainCIrms01, GainCIrms2
PhiIrms Phase compensation for Irms
PhiAIrms01, PhiAIrms2,
PhiBIrms01, PhiBIrms2,
PhiCIrms01, PhiCIrms2
UGainT
Temperature compensation only
goes to UGain
UGainTAB, UGainTC
PhiF
Frequency compensation only goes
to Phi/Delay
PhiFreqComp












+ ffsetGainIrms_o +
))
Irms_ref
Irms
(Log(*GainIrms
1 *Gain0 =
inChannel_Ga
2
19












+
2
20
T0)-(T*UGainT
1 *UGain0 = in_VoltageChannel_Ga
2
19
))
Irms0
Irms1
(Log(*GainIrms1
= ffsetGainIrms_o