71M6521DE Datasheet, PDF (62/107 Pages) Teridian Semiconductor Corporation – Energy Meter IC

71M6521DE/DH/FE Data Sheet
Parameter
VREF(T) deviation from VNOM(T)
VREF(T ) − VNOM (T )
10 ⁶
VNOM (T )
max(T − 22 ,40)
Condition
Min
-20
Table 62: VREF Definition for the High-Accuracy Parts
Typ
+20 PPM/ºC
Figure 30 and Figure 31 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 ±1260 PPM (or 0.126%) 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 ±0.126% add
up to a maximum Wh registration error of ±0.252%.
Error Band (PPM) over Temperature (°C)
2800
2400
2000
1600
1200
800
400
0
-400
-800
-1200
-1600
-2000
-2400
-2800
±40 PPM/°C
±40 PPM/°C
-40
-20
0
20
40
60
80
Figure 30: Error Band for VREF over Temperature (Regular-Accuracy Parts)
Page: 62 of 107
Rev 2