71M6521DE Datasheet, PDF (86/107 Pages) Teridian Semiconductor Corporation – Energy Meter IC

71M6521DE/DH/FE Data Sheet
Fundamental Energy Measurement Variables
The table below describes each transfer variable for fundamental energy 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
0x76
0x72
0x75
0x71
Name
W0SUM_X
W1SUM_X
VAR0SUM_X
VAR1SUM_X
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.
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.
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.
Instantaneous Energy Measurement Variables
The Frequency measurement is computed using the Frequency locked loop for the selected phase.
IxSQSUM_X and VxSQSUM are the squared current and voltage samples acquired during the last accumulation
interval. INSQSUM_X can be used for computing the neutral current.
CE
Address
0x79
0x77
0x73
0x78
0x74
0x7D
0x7E
Name
FREQ_X
I0SQSUM_X
I1SQSUM_X
V0SQSUM_X
V1SQSUM_X
WSUM_ACCUM
VSUM_ACCUM
Description
Fundamental frequency. LSB ≡ ^FS ≈ 0.587 ⋅10 ^−6 Hz
2 ³²
The sum of squared current samples from each element.
LSB = 6.6952*10^-13 IMAX² / In_8² A²h
The sum of squared voltage samples from each element.
LSB= 6.6952*10^-13 VMAX² V²h
These are roll-over accumulators for WPULSE and VPULSE
respectively.
The RMS values can be computed by the MPU from the squared current and voltage samples as follows:
Ix_RMS =
IxSQSUM ⋅ LSB ⋅ 3600 ⋅ F_S
N _ACC
Vx_RMS =
VxSQSUM ⋅ LSB ⋅3600 ⋅ F_S
N _ACC
Other Measurement Parameters
MAINEDGE_X is useful for implementing a real-time clock based on the input AC signal. MAINEDGE_X is the number
of half-cycles accounted for in the last accumulated interval for the AC signal.
TEMP_RAW may be used by the MPU to monitor chip temperature or to implement temperature compensation.
Page: 86 of 107
Rev 2