Datasheet

71M6513/71M6513H
3-Phase Energy Meter IC
DATA SHEET
SEPTEMBER 2011
© 2005-2011 Teridian Semiconductor Corporation Page: 15 of 104
A Maxim Integrated Products Brand
o
delay
o
delay
ft
T
t
360360 ⋅⋅=⋅=
φ
Where f is the frequency of the input signal and t
delay
is the sampling delay between voltage and current.
In traditional meter ICs, sampling is accomplished by using two A/D converters per phase (one for voltage and the other one
for current) controlled to sample simultaneously. Our Single-Converter Technology, however, exploits the 32-bit signal
processing capability of its CE to implement “constant delay” all-pass filters. These all-pass filters correct for the conversion
time difference between the voltage and the corresponding current samples that are obtained with a single multiplexed A/D
converter.
The “constant delay” all-pass filters provide a broad-band delay β that is precisely matched to the difference in sample time
between the voltage and the current of a given phase. This digital filter does not affect the amplitude of the signal, but
provides a precisely controlled phase response. The delay compensation implemented in the CE aligns the voltage samples
with their corresponding current samples by routing the voltage samples through the all-pass filter, thus delaying the voltage
samples by β, resulting in the residual phase error β – Ф. The residual phase error is negligible, and is typically less than ±1.5
milli-degrees at 100Hz, thus it does not contribute to errors in the energy measurements.