71M6533 Datasheet, PDF (70/132 Pages) Teridian Semiconductor Corporation – Energy Meter IC

71M6533/G/H and 71M6534/H Data Sheet
FDS_6533_6534_004
Since TC1 and TC2 are given in µV/°C and µV/°C², respectively, the value of the VREF voltage
(1.195V) has to be taken into account when transitioning to PPM/°C and PPM/°C². This means
that PPMC = 26.84*TC1/1.195 and PPMC2 = 1374*TC2/1.195).
Close examination of the electrical specification (see Table 51) for the parts with regular accuracy reveals
that the achievable deviation is not strictly ±40 PPM/°C over the whole temperature range: Only for
temperatures for which T-22 > 40 (i.e. T > 62°C) or for which T-22 < -40 (i.e. T < -18°C), the data sheet
states ±40 PPM/°C. For temperatures between -18°C and +62°C, the error should be considered
constant at ±1,600 PPM, or ±0.16%.
Similar considerations apply to the high-accuracy parts (see Table 52), where the error around the
calibration temperature should be considered constant at ±600 PPM, or ±0.06%.
Parameter
VREF(T) deviation from VNOM(T)
VREF(T ) − VNOM (T )
10 ⁶
VNOM (T )
max(T − 22 ,40)
Condition
Min
-40
Table 51: VREF Definition for the Regular Accuracy Parts
Typ
+40 PPM/ºC
Parameter
4 VREF(T) deviation from
VNOM(T)
VREF(T ) − VNOM (T )
10 ⁶
VNOM (T )
max(T − 22 ,40)
Condition
Min
-15
Table 52: VREF Definition for the High-Accuracy Parts
Typ
+15 PPM/ºC
Figure 34 and Figure 35 show this concept graphically. The “box” from -18°C to +62°C reflects the fact
that it is impractical to measure the temperature coefficient of high-quality references at small temperature
excursions. For example, at +25°C, the expected error would be ±3°C * 40 PPM/°C, or just 0.012% for the
regular-accuracy parts..
The maximum deviation of ±2520 PPM (or 0.252%) for the regular-accuracy parts is reached at the
temperature extremes. If the reference voltage is used to measure both voltage and current, the identical
errors of ±0.252% add up to a maximum Wh registration error of ±0.504%.
The maximum deviation of ±945 PPM (or 0.0945%) for the high-accuracy parts is reached at the
temperature extremes. If the reference voltage is used to measure both voltage and current, the identical
errors of ±0.0945% add up to a maximum Wh registration error of ±0.189%.
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