
ADE7854/ADE7858/ADE7868/ADE7878
Rev. E | Page 31 of 96
Voltage Waveform Gain Registers
There is a multiplier in the signal path of each phase voltage.
The voltage waveform can be changed by ±100% by writing
a corresponding twos complement number to the 24-bit signed
current waveform gain registers (AVGAIN, BVGAIN, and
CVGAIN). For example, if 0x400000 is written to those registers,
the ADC output is scaled up by 50%. To scale the input by 50%,
write 0xC00000 to the registers. Equation 4 describes mathe-
matically the function of the current waveform gain registers.
Voltage Waveform =
+
×
23
2
1
Register
Gain
Voltage
of
Content
Output
ADC
(4)
Changing the content of the AVGAIN, BVGAIN, and CVGAIN
registers affects all calculations based on its voltage; that is, it
affects the corresponding phase active/reactive/apparent energy
and voltage rms calculation. In addition, waveform samples are
scaled accordingly.
serial ports of the ADE78xx work on 32-, 16-, or 8-bit words,
and the DSP works on 28 bits. As presented in
Figure 33, the
AVGAIN, BVGAIN, and CVGAIN registers are accessed as
32-bit registers with four MSBs padded with 0s and sign
extended to 28 bits.
Voltage Channel HPF
outputs can contain a dc offset that can create errors in power
and rms calculations. HPFs are placed in the signal path of the
phase voltages, similar to the ones in the current channels. The
HPFDIS register can enable or disable the filters. See the
Voltage Channel Sampling
The waveform samples of the voltage channel are taken at the
output of HPF and stored into VAWV, VBWV, and VCWV
24-bit signed registers at a rate of 8 kSPS. All power and rms
calculations remain uninterrupted during this process. Bit 17
(DREADY) in the STATUS0 register is set when the VAWV,
VBWV, and VCWV registers are available to be read using the
I2C or SPI serial port. Setting Bit 17 (DREADY) in the MASK0
register enables an interrupt to be set when the DREADY flag is
Bit DREADY.
serial ports of the ADE78xx work on 32-, 16-, or 8-bit words.
Similar to registers presented in
Figure 35, the VAWV, VBWV,
and VCWV 24-bit signed registers are transmitted sign
extended to 32 bits.
The ADE7854/ADE7858/ADE7868/ADE7878 each contain an
HSDC port especially designed to provide fast access to the
more details.
CHANGING PHASE VOLTAGE DATAPATH
The ADE7854/ADE7858/ADE7868/ADE7878 can direct one
phase voltage input to the computational datapath of another
phase. For example, Phase A voltage can be introduced in the
Phase B computational datapath, which means all powers
computed by the ADE78xx in Phase B are based on Phase A
voltage and Phase B current.
Bits[9:8] (VTOIA[1:0]) of the CONFIG register manage the
Phase A voltage measured at the VA pin. If VTOIA[1:0] = 00
(default value), the voltage is directed to the Phase A computa-
tional datapath. If VTOIA[1:0] = 01, the voltage is directed to
the Phase B path. If VTOIA[1:0] = 10, the voltage is directed to the
Phase C path. If VTOIA[1:0] = 11, the ADE7878 behaves as if
VTOIA[1:0] = 00.
Bits[11:10] (VTOIB[1:0]) of the CONFIG register manage the
Phase B voltage measured at the VB pin. If VTOIB[1:0] = 00
(default value), the voltage is directed to the Phase B computa-
tional datapath. If VTOIB[1:0] = 01, the voltage is directed to
the Phase C path. If VTOIB[1:0] = 10, the voltage is directed to
the Phase A path. If VTOIB[1:0] = 11, the ADE78xx behaves
as if VTOIB[1:0] = 00.
Bits[13:12] (VTOIC[1:0]) of the CONFIG register manage the
Phase C voltage measured at the VC pin. If VTOIC[1:0] = 00
(default value), the voltage is directed to Phase C computational
datapath, if VTOIC[1:0] = 01, the voltage is directed to the
Phase A path. If VTOIC[1:0] = 10, the voltage is directed to the
Phase B path. If VTOIC[1:0] = 11, the ADE78xx behaves as if
VTOIC[1:0] = 00.
IA
VA
IB
VB
IC
VC
PHASE A
COMPUTATIONAL
DATAPATH
PHASE B
COMPUTATIONAL
DATAPATH
PHASE C
COMPUTATIONAL
DATAPATH
VTOIA[1:0] = 01,
PHASE A VOLTAGE
DIRECTED
TO PHASE B
VTOIB[1:0] = 01,
PHASE B VOLTAGE
DIRECTED
TO PHASE C
VTOIC[1:0] = 01,
PHASE C VOLTAGE
DIRECTED
TO PHASE A
CPHCAL
BPHCAL
APHCAL
08
51
0-
02
6
Figure 40. Phase Voltages Used in Different Datapaths
Figure 40 presents the case in which Phase A voltage is used in
the Phase B datapath, Phase B voltage is used in the Phase C
datapath, and Phase C voltage is used in the Phase A datapath.