71M6545 Datasheet, PDF (75/134 Pages) Maxim Integrated Products – Four-Quadrant Metering, Phase Metrology Processors Flash/RAM Size

PDS_6545_009
Data Sheet 71M6545/H
The preceding discussion in this section also applies to the71M6603 (0.5%), 71M6113 (0.5%) and
71M6203 (0.1%) remote sensors.
4.5.2 Temperature Coefficients for the 71M6545
The equations provided below for calculating TC1 and TC2 apply to the 71M6545 (0.5% energy accuracy). In
order to obtain TC1 and TC2, the MPU reads TRIMT[7:0] (I/O RAM 0x2309) and uses the TC1 and TC2
equations provided. PPMC and PPMC2 are then calculated from TC1 and TC2, as shown. The resulting
tracking of the reference voltage (VREF) is within ±40 ppm/°C, corresponding to a ±0.5% energy
measurement accuracy. See 4.5.1 Distinction Between Standard and High-Precision Parts.
TC1(µV / °C) = 275 − 4.95 ⋅TRIMT
TC2(µV / °C²) = −0.557 + 0.00028 ⋅TRIMT
PPMC = 22.4632 ⋅TC1
PPMC2 = 1150.116 ⋅TC2
See 4.5.5 and 4.5.6 below for further temperature compensation details.
4.5.3 Temperature Coefficients for the 71M6545H
For the 71M6545H, undergoes a two-pass factory trimming process which stores additional trim fuse
values. The additional trim fuse values characterize the device’s VREF behavior at various temperatures.
The values for TC1 and TC2 are calculated from the values read from the TRIMT[7:0] (I/O RAM 0x2309),
TRIMBGB[15:0] (Info Page 0x92 and 0x93) and TRIMBGD[7:0] (Info Page 0x94) non-volatile on-chip
fuses using the equations provided. The resulting tracking of the reference voltage is within ±10 ppm/°C,
corresponding to a ±0.126% energy measurement accuracy. The equations for deriving PPCM and PPMC2
from TC1 and TC2 are also provided. See 4.5.1 Distinction Between Standard and High-Precision Parts.
TC1(µV/℃)=35.091+0.01764∙TRIMT+1.587∙(𝑇𝑅𝐼𝑀𝐵𝐺𝐵 − 𝑇𝑅𝐼𝑀𝐵𝐺𝐷)
TC2(µV / °C²) = −0.557 − 0.00028 ⋅TRIMT
PPMC = 22.4632 ⋅TC1
PPMC2 = 1150.116 ⋅TC2
TRIMT[7:0] trims the VREF voltage for minimum variation with temperature. The TRIMT[7:0] fuses are
read by the MPU directly at I/O RAM address 0x2309[7:0].
During the second pass trim for the 71M6545H, VREF is further characterized at 85°C and 22°C, and the
resulting fuse trim values are stored in TRIMBGB[15:0] and TRIMBGD[7:0], respectively. TRIMBGB[15:0]
and TRIMBGD[7:0] cannot be read directly by the MPU. See 5.3 Reading the Info Page (71M6545H only)
on page 98 for information on how to read the Info Page trim fuses.
See 4.5.5 and 4.5.6 below for further temperature compensation details.
4.5.4 Temperature Coefficients for the 71M6603 and 71M6103 (1% Energy Accuracy)
Refer to the 71M6xxx Data sheet for the equations that are applicable to each 71M6xx3 part number and
the corresponding temperature coefficients.
4.5.5 Temperature Compensation for VREF and Shunt Sensors
This section discusses metrology temperature compensation for the meter designs where current shunt
sensors are used in conjunction with Teridian’s 71M6xx3 remote isolated sensors, as shown in Figure 27.
Sensors that are directly connected to the 71M6545/H are affected by the voltage variation in the
71M6545/H VREF due to temperature. On the other hand, shunt sensors that are connected to 71M6xx3
remote sensor are affected by the VREF in the 71M6xx3. The VREF in both the 71M6545/H and
71M6xx3 can be compensated digitally using a second-order polynomial function of temperature. The
71M6545/H and 71M6xx3 feature temperature sensors for the purposes of temperature compensating
their corresponding VREF. The compensation computations must be implemented in MPU firmware.
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