71m6543h-igtr/f Maxim Integrated Products, Inc., 71m6543h-igtr/f Datasheet - Page 90

• Manufacturer Part Number: 71m6543h-igtr/f
• Description: Energy Meter Ic
• Manufacturer: Maxim Integrated Products, Inc.

directly connected to the 71M6543F/H. Thus, the precision of the voltage sensors is primarily affected by
VREF in the 71M6543F/H. The temperature coefficient of the resistors used to implement the voltage
dividers for the voltage sensors (see
respect to temperature. It is recommended to use resistors with low temperature coefficients, while forming
the entire voltage divider using resistors belonging to the same technology family, in order to minimize the
temperature dependency of the voltage division ratio. The resistors must also have suitable voltage ratings.
The 71M6543F/H also may have one local current shunt sensor that is connected directly to it via the
IADC0-IADC1 input pins, and therefore this local current sensor is also affected by the VREF in the
71M6543F/H. The shunt current sensor resistance has a temperature dependency, which also may
require compensation, depending on the required accuracy class.
The IADC2-IADC3, IADC4-IADC5 and IADC6-IADC7 current sensors are isolated by the 71M6xx3 and
71M6543F/H Data Sheet
Referring to
depend on the VREF of the 71M6xx3, plus the variation of the corresponding remote shunt current sensor
with temperature.
The MPU has the responsibility of computing the necessary sample gain compensation values required for
each sensor channel based on the sensed temperature. Teridian provides demonstration code that
implements the GAIN_ADJx compensation equation shown below. The resulting GAIN_ADJx values are
stored by the MPU in five CE RAM locations GAIN_ADJ0-GAIN_ADJ5 (CE RAM 0x40-0x44). The
demonstration code thus provides a suitable implementation of temperature compensation, but other
methods are possible in MPU firmware by utilizing the on-chip temperature sensors while storing the
sample gain adjustment results in the CE RAM GAIN_ADJx storage locations for use by the CE. The
demonstration code maintains five separate sets of PPMC and PPMC2 coefficients and computes five
separate GAIN_ADJx values based on the sensed temperature using the equation below:
The GAIN_ADJx values stored by the MPU in CE RAM are used by the CE to gain adjust (i.e., multiply)
the sample in each corresponding sensor channel. A GAIN_ADJx value of 16,384 (i.e., 2
unity gain, while values less than 16,384 attenuate the samples and values greater than 16,384 amplify
the samples.
In the above equation, TEMP_X is the deviation from nominal or calibration temperature expressed in
multiples of 0.1 °C. The 10x and 100x factors seen in the above equation are due to 0.1
TEMP_X. For example, if the calibration (reference) temperature is 22
is 27
In the demonstration code, TEMP_X is calculated in the MPU from the STEMP[10:0] temperature sensor
reading using the equation provided below and is scaled in 0.1°C units. See
Temperature Sensor
STEMP[10:0] value.
Table 67
channels for which they compensate for the 1 Local / 3 Remote configuration shown in
90
Gain Adjustment Output
o
C, then 10*TEMP_X = (27-22) x 10 = 50 (decimal), which represents a +5
shows the five GAIN_ADJx equation output storage locations and the voltage or current sensor
GAIN_ADJ0
GAIN_ADJ1
GAIN_ADJ2
GAIN_ADJ3
GAIN_ADJ4
Table 67: GAIN_ADJn Compensation Channels
Figure
GAIN
31, the VADC8 (VA), VADC9 (VB) and VADC10 (VC) voltage sensors are always
_
on page
ADJx
© 2008–2011 Teridian Semiconductor Corporation
=
54
16385
CE RAM Address
for the equation to calculate temperature in degrees °C from the
Figure
+
0x41
0x42
0x43
0x44
0x40
10
⋅
TEMP
27) determine the behavior of the voltage division ratio with
2
_
14
Sensor Channel(s)
X
VADC10 (VC)
IADC0-IADC1
IADC2-IADC3
IADC4-IADC5
IADC6-IADC7
(pin names)
VADC8 (VA)
VADC9 (VB)
⋅
PPMC
+
(Figure
100
⋅
TEMP
VREF in 71M6543F/H and Voltage Divider
o
2,
C and the measured temperature
VREF in 71M6543F/H and Shunt
Figure 31, Table
VREF in 71M6xx3 and Shunt
VREF in 71M6xx3 and Shunt
VREF in 71M6xx3 and Shunt
2.5.5 71M6543F/H
_
2
23
Compensation For:
X
(Neutral Current)
o
2
C deviation from 22
⋅
(Phase A)
(Phase B)
(Phase C)
Resistors
PPMC
Figure
14
o
C scaling of
)corresponds to
2
1)
31.
o
v1.0
C.