71M6511 Datasheet, PDF (67/95 Pages) Teridian Semiconductor Corporation – Single-Phase Energy Meter IC

71M6511/71M6511H
Single-Phase Energy Meter IC
DATA SHEET
AUGUST 2007
For generating proper status information, the CE is initialized by the MPU using SAG_THR (default of 80V RMS at the meter
input if VMAX=600V) and SAG_CNT (default 80 samples). Using the default value for SAG_CNT, the peak-to-peak signal has
to be below SAG_THR value for 32 milliseconds to activate the SAG_X status bits.
CE
Address
Name
Default
0x31
SAG_THR
+56,722,300
(0x361837C)
0x32
SAG_CNT
80
Description
Meter voltage inputs must be above this threshold to prevent sag alarms.
LSB = VMAX * 3.3243*10^-9 V peak.
For example, if a sag threshold of 80V RMS is desired,
SAG
_ THR
=
80 2
VMAX ⋅3.3243⋅10^−9
Number of consecutive voltage samples below SAG_THR before a sag alarm
is declared. 80*397µs = 31.8ms (for MUX_DIV = 1).
CE Transfer Variables
When the MPU receives the XFER_BUSY interrupt, it knows that fresh data is available in the transfer variables. CE transfer
variables are modified during the CE code pass that ends with an XFER_BUSY interrupt. They remain constant throughout
each accumulation interval. In this data sheet, the names of CE transfer variables always end with _X.
Fundamental Power Measurement Variables
The table below describes each transfer variable for fundamental power measurement. All variables are signed 32 bit integers.
Accumulated variables such as WSUM are internally scaled so they have at least 2x margin before overflow when the
integration time is 1 second. Additionally, the hardware will not permit output values to ‘fold back’ upon overflow.
CE
Address
42
43
44
45
46
47
48
49
Name
RESERVED
W0SUM_X
W1SUM_X
RESERVED
RESERVED
VAR0SUM_X
VAR1SUM_X
RESERVED
Description
The sum of Watt samples from each wattmeter element (In_8 is the gain
configured by IA_SHUNT or IB_SHUNT).
LSB = 6.6952*10^-13 VMAX IMAX / In_8 Wh (for MUX_DIV = 1)
LSB = 5.1501*10^-13 VMAX IMAX / In_8 Wh (for MUX_DIV = 2)
The sum of VAR samples from each wattmeter element (In_8 is the gain
configured by IA_SHUNT or IB_SHUNT).
LSB = 6.6952*10^-13 VMAX IMAX / In_8 Wh (for MUX_DIV = 1)
LSB = 5.1501*10^-13 VMAX IMAX / In_8 Wh (for MUX_DIV = 2)
WxSUM_X is the Wh value accumulated for element ‘X’ in the last accumulation interval and can be computed based on the
specified LSB value.
For example with VMAX = 600V and IMAX = 208A, LSB (for WxSUM_X ) is 0.08356 µWh (MUX_DIV = 1).
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