ade7854 Analog Devices, Inc., ade7854 Datasheet - Page 41

• Manufacturer Part Number: ade7854
• Description: Poly Phase Multifunction Energy Metering Ic With Neutral Current Measurement
• Manufacturer: Analog Devices, Inc.

Preliminary Technical Data
Register
ICWV
VAWV
VBWV
VCWV
The bit 17 (DREADY) in STATUS0[31:0] register can be used
to signal when the registers mentioned in Table 15 may be read
using I
may be enabled by setting bit 17 (DREADY) in MASK0[31:0]
register. See Digital Signal Processor chapter for more details on
bit DREADY.
The ADE7854 contains a High Speed Data Capture (HSDC)
port that is specially designed to provide fast access to the
waveform sample registers. See HSDC Interface section for
more details.
The DSP computes the instantaneous values of all phase
powers: total active, fundamental active, total reactive,
fundamental reactive and apparent. The process in which the
energy is sign accumulated in various hr registers (watt-hr, var-
hr and VA-hr) has already been described in Energy
Calculation chapters. In the energy to frequency conversion
process, the instantaneous powers are used to generate signals
at frequency output pins CF1, CF2 and CF3.
One digital to frequency converter is used for every CF pin.
Every converter sums certain phase powers and generates a
signal proportional to the sum. Two sets of bits decide what
powers are converted.
First, bits 2, 1, 0 (TERMSEL1[2:0]), 5, 4, 3 (TERMSEL2[2:0])
and 8, 7, 6 (TERMSEL3[2:0]) of COMPMODE[15:0] register
Digital Signal Processor
phase A active
phase B active
phase C active
Instantaneous
Instantaneous
Instantaneous
2
C or SPI serial ports. An interrupt attached to the flag
power
power
power
Description
Phase C current
Phase A voltage
Phase B voltage
Phase C voltage
Register
CWATT
AVA
BVA
CVA
Σ
TERMSELx bits in
COMPMODE
Description
power
Phase C active
power
Phase A apparent
power
Phase B apparent
power
Phase C apparent
power
Figure 51. ADE7854 Energy to Frequency Conversion
VAR
WATT
CFxSEL bits in
VA
CFMODE
Rev. PrC| Page 41 of 71
2
x
7
As previously stated, the serial ports of the ADE7854 work on
32, 16 or 8-bit words. All registers listed in Table 15 are
transmitted signed extended from 24 to 32 bits (see Figure 18).
ENERGY TO FREQUENCY CONVERSION
The ADE7854 provides 3 frequency output pins: CF1, CF2 and
CF3.
CF3 pin is multiplexed with HSCLK pin of HSDC interface.
When HSDC is enabled, the CF3 functionality is disabled at the
pin. CF1 and CF2 pins are always available. After initial
calibration at manufacturing, the manufacturer or end
customer verifies the energy meter calibration. One convenient
way to verify the meter calibration is to provide an output
frequency proportional to the active, reactive or apparent
powers under steady load conditions. This output frequency
can provide a simple, single-wire, optically isolated interface to
external calibration equipment. Figure 51 illustrates the energy-
to-frequency conversion in the ADE7854.
decide which phases or which combination of phases are added.
TERMSEL1 bits refer to CF1 pin, TERMSEL2 bits refer to CF2
pin and TERMSEL3 bits refer to CF3 pin. TERMSELx[0] bits,
x=1, 2, 3 manage phase A. When set to 1, phase A power is
included in the sum of powers at CFx converter. When cleared
to 0, phase A power is not included. TERMSELx[1] bits manage
phase B, TERMSELx[2] bits manage phase C. Setting all
TERMSELx bits to 1 means all 3 phase powers are added at CFx
converter. Clearing all TERMSELx bits to 0 means no phase
power is added and no CF pulse is generated.
Second, bits 2, 1, 0 (CF1SEL[2:0]), 5, 4, 3 (CF2SEL[2:0]) and 8,
7, 6 (CF3SEL[2:0]) in CFMODE[15:0] register decide what type
power is used at the inputs of CF1, CF2 and respective CF3
converters. Table 16 shows the values that CFxSEL may have:
total active or apparent powers.
WTHR[47:0]
Σ
55 bits
2
x
7
REVPSUMx bit of
STATUS0[31:0]
Freq Divider
CFxDEN
ADE7854
CFx pulse
output