ade7566 Analog Devices, Inc., ade7566 Datasheet - Page 57

• Manufacturer Part Number: ade7566
• Description: Single-phase Energy Measurement Ic With 8052 Mcu, Rtc, And Lcd Driver
• Manufacturer: Analog Devices, Inc.

When SAVARM in the ACCMODE register (0x0F) is set, the
reactive power is accumulated depending on the sign of the
active power. When active power is positive, the reactive power
is added as it is to the reactive energy register. When active
power is negative, the reactive power is subtracted from the
reactive energy accumulator (see the VAR Antitamper
Accumulation Mode section).
When ABSVARM in the ACCMODE register (0x0F) is set, the
absolute reactive power is used for the reactive energy accumu-
lation (see the VAR Absolute Accumulation Mode section).
The output of the multiplier is divided by VARDIV. If the value
in the VARDIV register is equal to 0, the internal reactive
energy register is divided by 1. VARDIV is an 8-bit, unsigned
register. After dividing by VARDIV, the reactive energy is
accumulated in a 49-bit internal energy accumulation register.
The upper 24 bits of this register are accessible through a read
to the reactive energy register (VARHR[23:0]). A read to the
RVARHR register returns the content of the VARHR register,
and the upper 24 bits of the internal register are cleared.
CURRENT
CHANNEL
VOLTAGE
CHANNEL
HPF
PHCAL[7:0]
SHIFTING FILTER
90° PHASE
Π
2
T
REACTIVE POWER
LPF2
CLKIN
sgn
SIGNAL
5
TIME (nT)
VAROS[15:0]
2
6
Figure 66. Reactive Energy Calculation
2
+
5
+
2
WAVEFORM
REGISTER
–6
Rev. 0 | Page 57 of 136
VALUES
2
–7
FOR WAVEFORM
2
–8
SAMPLING
VARGAIN[11:0]
As shown in Figure 66, the reactive power signal is accumulated
in an internal 49-bit signed register. The reactive power signal
can be read from the waveform register by setting the WAVMODE
register (0x0D) and setting the WFSM bit in the Interrupt Enable 3
SFR (MIRQENH, 0xDB). Like the current and voltage channel
waveform sampling modes, the waveform data is available at
sample rates of 25.6 kSPS, 12.8 kSPS, 6.4 kSPS, or 3.2 kSPS.
Figure 61 shows this energy accumulation for full-scale signals
(sinusoidal) on the analog inputs. These curves also apply for
the reactive energy accumulation.
Note that the energy register contents roll over to full-scale
negative (0x800000) and continue to increase in value when the
power or energy flow is positive. Conversely, if the power is
negative, the energy register underflows to full-scale positive
(0x7FFFFF) and continues to decrease in value.
By using the interrupt enable register, the ADE7569 can be
configured to issue an ADE interrupt to the 8052 core when the
reactive energy register is half-full (positive or negative) or
when an overflow or underflow occurs.
DIGITAL-TO-FREQUENCY
VARDIV[7:0]
CONVERTER
%
TO
+
+
48
23
VARHR[23:0]
OUTPUTS FROM THE LPF2 ARE
ACCUMULATED (INTEGRATED) IN
THE INTERNAL REACTIVE ENERGY
REGISTER
ADE7566/ADE7569
0
UPPER 24 BITS ARE
ACCESSIBLE THROUGH
VARHR[23:0] REGISTER
0