71M6531D Datasheet, PDF (91/115 Pages) Teridian Semiconductor Corporation – Energy Meter IC

FDS 6531/6532 005
Data Sheet 71M6531D/F-71M6532D/F
The RMS values can be computed by the MPU from the squared current and voltage samples as follows:
Ix_RMS =
IxSQSUM ⋅ LSB_I ⋅ 3600 ⋅ F_S
N _ACC
Vx_RMS =
VxSQSUM ⋅ LSB_V ⋅ 3600 ⋅ F_S
N _ACC
Other Measurement Parameters
Table 57 describes the CE measurement parameters listed below:
• MAINEDGE_X: 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 the chip temperature or to implement temperature
compensation.
• GAIN_ADJ: A scaling factor for measurements based on the temperature. GAIN_ADJ can be con-
trolled by the MPU for temperature compensation.
• VBAT_SUM_X: This result can be used to calculate the measured battery voltage (VBAT).
CE Ad-
dress
0x83
0x81
0x9D
0x40
0x84
Table 57: Useful CE Measurement Parameters
Name
MAINEDGE_X
TEMP_RAW_X
TEMP_X
GAIN_ADJ
VBAT_SUM_X
Default
Description
N/A
N/A
N/A
16384
N/A
The number of zero crossings of the voltage selected with
FREQSELn in the previous accumulation interval. Zero
crossings are either direction and are debounced.
The filtered, un-scaled reading from the temperature sensor.
This register contains the difference between the die temper-
ature and the reference/calibration temperature as estab-
lished in the TEMP_NOM register, measured in 0.1°C.
Scales all voltage and current inputs. A value of 16384 pro-
vides unity gain. This register is used by the CE or by the
MPU to implement temperature compensation.
The result of the battery voltage measurement.
4.3.8 Pulse Generation
Table 58 describes the CE pulse generation parameters WRATE, APULSEW, APULSER, APULSE2 and
APULSE3.
WRATE controls the number of pulses that are generated per measured Wh and VARh quantities. The
lower WRATE is the slower the pulse rate for measured energy quantity. The metering constant Kh is de-
rived from WRATE as the amount of energy measured for each pulse. That is, if Kh = 1 Wh/pulse, a pow-
er applied to the meter of 120 V and 30 A (3,600 W) results in one pulse per second. If the load is 240 V
at 150 A (36,000 W), ten pulses per second will be generated.
The maximum pulse rate is 7.5 kHz for APULSEW and APULSER and 1.2 kHz for APULSE2 and APULSE3.
The maximum time jitter is 67 µs and is independent of the number of pulses measured. Thus, if the pulse
generator is monitored for one second, the peak jitter is 67 ppm. After 10 seconds, the peak jitter is 6.7 ppm.
The average jitter is always zero. If it is attempted to drive either pulse generator faster than its maximum
rate, it will simply output at its maximum rate without exhibiting any rollover characteristics. The actual
pulse rate, using WSUM as an example, is:
RATE
=
WRATE ⋅WSUM
2 ⁴⁶
⋅ F_S
⋅
X
Hz ^,
where F_S = sampling frequency (2520.6 Hz) and X = Pulse speed factor (as defined in the CECONFIG
register with the PULSE_FAST and PULSE_SLOW bits).
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