71M6511 Datasheet, PDF (69/95 Pages) Teridian Semiconductor Corporation – Single-Phase Energy Meter IC

71M6511/71M6511H
Single-Phase Energy Meter IC
DATA SHEET
AUGUST 2007
Temperature Measurement and Temperature Compensation
Input variables: TEMP_NOM is the reference value for temperature measurement, i.e. when this value is set with
TEMP_RAW_X at known temperature. The 71M6511/6511H measures temperature with reference to this value.
DEGSCALE is the slope or rate of temperature increase or decrease from the TEMP_NOM for TEMP_X measurement.
PPMC and PPMC2 are temperature compensation coefficients. Their values should reflect the characteristics of the band gap
voltage reference of the chip. PPMC and PPMC2 follow the square law characteristics to compensate for nonlinear
temperature behaviors, when the 71M6511/6511H is in internal temperature compensation mode.
CE
Address
0x11
Name
TEMP_NOM
0x30
DEGSCALE
0x38
EXT_TEMP
0x39
PPMC
0x3A
PPMC2
Default
0
9585
0
0
0
Description
During calibration, the value of TEMP_RAW_X should be placed in
TEMP_NOM.
Scale factor for TEMP_X.
TEMP_X = -DEGSCALE*2^-22*(TEMP_RAW_X-TEMP_NOM).
Should be 15 or 0. When 15, causes the CE to ignore internal temperature
compensation and permits the MPU to control GAIN_ADJ. When internal
temperature compensation is selected, GAIN_ADJ will be:
GAIN
_
ADJ
= 16384+
floor_{}1+
TEMP _ X
2¹⁴
⋅
PPMC
+
TEMP _
X²â‹…
2 ²³
PPMC2 _{}
Default is 0 (internal compensation).
Linear temperature compensation factor. Equals the linear temperature co-
efficient (PPM/°C) of VREF multiplied by 26.84, or TC1 (expressed in µV/°C,
see Electrical Specifications) multiplied by 22.46. A positive value will cause
the meter to run faster when hot. The compensation factor affects both V and
I and will therefore have a double effect on products.
Square-law temperature compensation factor. Equals the square-law tem-
perature coefficient (PPM/°C²) of VREF multiplied by 1374, or TC2 (ex-
pressed in µV/°C², see Electrical Specifications) multiplied by 1150.1. A po-
sitive value will cause the meter to run faster when hot. The compensation
factor affects both V and I and will therefore have a double effect on prod-
ucts.
EXT_TEMP allows the MPU to select between direct control of GAIN_ADJ or management of GAIN_ADJ by the CE, based on
TEMP_X and the temperature correction coefficients PPMC and PPMC2.
Output variables: TEMP_X is the temperature measurement from reference temperature of TEMP_NOM. TEMP_X is
computed using TEMP_RAW_X and DEGSCALE. This quantity is positive when the temperature is above the reference and is
negative for cold temperatures.
TEMP_RAW_X is the raw processed value from ADC output and is the fundamental quantity for temperature measurement.
TEMP_RAW_X is less than TEMP_NOM at higher temperatures. TEMP_RAW_X is more than TEMP_NOM for cooler
temperatures than reference temperature.
GAIN_ADJ is a scaling factor for power measurements based on temperature (when in internal temperature compensation
mode). In general, for higher temperatures it is lower than 16384 and higher than 16384 for lower temperatures. GAIN_ADJ is
mainly dependent on the PPMC, PPMC2 and TEMP_X register values. This parameter is automatically computed by the CE
and is used by the CE for temperature compensation.
Page: 69 of 95
© 2005-2007 TERIDIAN Semiconductor Corporation
V2.6