ade7166 Analog Devices, Inc., ade7166 Datasheet - Page 56

• Manufacturer Part Number: ade7166
• Description: Single-phase Energy Measurement Ic With 8052 Mcu, Rtc, And Lcd Driver
• Manufacturer: Analog Devices, Inc.

ADE7566/ADE7569/ADE7166/ADE7169
Current Channel RMS Calculation
Each ADE7566/ADE7569/ADE7166/ADE7169 simultaneously
calculates the rms values for the current and voltage channels in
different registers. Figure 61 shows the detail of the signal
processing chain for the rms calculation on the current channel.
The current channel rms value is processed from the samples
used in the current channel waveform sampling mode and is
stored in an unsigned 24-bit register (I
current channel rms register is equivalent to one LSB of a
current channel waveform sample.
The update rate of the current channel rms measurement is
4.096 MHz/5. To minimize noise in the reading of the register,
the I
zero crossing of the voltage input. This configuration is done by
setting the ZXRMS bit in the MODE2 register (0x0C).
With the specified full-scale analog input signal different PGA1
values, the ADC produces an output code that is approximately
±0d2,147,483 (PGA1 = 1) or ±0d2,684,354 (PGA1 = 2, 4, 8, or 16).
See the Current Channel ADC section. Similarly, the equivalent
rms value of a full-scale ac signal is 0d1,518,499 (0x172BA3)
when PGA = 1 and 0d1,898,124 (0x1CF68C) when PGA1 = 2,
rms
register can also be configured to update only with the
I
I
PA
PB
HPF
HPF
Figure 60. ADE7566/ ADE7569 Current Channel RMS Signal Processing with PGA1 = 1, 2, 4, 8, or 16
rms
INTEGRATOR*
MODE 1[5]
). One LSB of the
DIGITAL
dt
HPF1
0xD70A3E
0xD487B0
0x2B7850
0x28F5C2
0x000000
0x000000
Rev. A | Page 56 of 144
60Hz
24
CURRENT CHANNEL
WAVEFORM
DATA RANGE WITH
INTEGRATOR ON (60Hz)
CURRENT CHANNEL
WAVEFORM
DATA RANGE WITH
INTEGRATOR OFF
4, 8, or 16. The current rms measurement provided in the
ADE7566/ADE7569/ADE7166/ADE7169 is accurate to within
0.5% for signal inputs between full scale and full scale/500. The
conversion from the register value to amps must be done
externally in the microprocessor using an amps/LSB constant.
Current Channel RMS Offset Compensation
The ADE7566/ADE7569/ADE7166/ADE7169 incorporate a
current channel rms offset compensation register (IRMSOS).
This is a 12-bit signed register that can be used to remove offset
in the current channel rms calculation. An offset can exist in
the rms calculation due to input noises that are integrated into
the dc component of V
One LSB of the current channel rms offset is equivalent to
16,384 LSBs of the square of the current channel rms register.
Assuming that the maximum value from the current channel
rms calculation is 0d1,898,124 with full-scale ac inputs, then
1 LSB of the current channel rms offset represents 0.23% of
measurement error at −60 dB down of full scale.
where I
I
rms
LPF3
rms0
sgn
=
is the rms measurement without offset correction.
2
25
I
2
rms
26
IRMSOS[11:0]
2
0
27
2
+
+
IRMSOS
2
18
2
(t).
2
17
2
16
24
×
32768
0x00
I
rms
I
rms
(t)
[23:0]
(6)