Datasheet

ADE5166/ADE5169/ADE5566/ADE5569 Data Sheet
Rev. D | Page 62 of 156
ACTIVE ENERGY CALCULATION
As stated in the Active Power Calculation section, active power
is defined as the rate of energy flow. This relationship can be
expressed mathematically, as shown in Equation 11.
dt
dE
P =
(11)
where:
P is power.
E is energy.
Conversely, energy is given as the integral of power.
∫
= dttPE )(
(12)
The ADE5166/ADE5169/ADE5566/ADE5569 achieve the inte-
gration of the active power signal by continuously accumulating
the active power signal in an internal, nonreadable, 49-bit energy
register. The WAT T H R register (Address 0x01) represents the
upper 24 bits of this internal register. This discrete time
accumulation or summation is equivalent to integration in
continuous time. Equation 13 expresses the relationship.






×==
∑
∫
∞
=
→
1
0
)(lim)
(
n
t
TnTPdttPE
(13)
where:
n is the discrete time sample number.
T is the discrete time sample period.
The discrete time sample period (T) for the accumulation
register in the ADE5166/ADE5169/ADE5566/ADE5569 is 1.22 µs
(5/MCLK). In addition to calculating the energy, this integration
removes any sinusoidal components that may be in the active
power signal. Figure 66 shows this discrete time integration or
accumulation. The active power signal in the waveform register
is continuously added to the internal active energy register.
The active energy accumulation depends on the setting of
POAM (Bit 1) and ABSAM (Bit 0) in the ACCMODE register
(Address 0x0F). When both bits are cleared, the addition is signed
and, therefore, negative energy is subtracted from the active
energy contents. When both bits are set, the ADE5166/ADE5169/
ADE5566/ADE5569 are set to the more restrictive mode, the
positive-only accumulation mode.
When POAM (Bit 1) in the ACCMODE register (Address 0x0F)
is set, only positive power contributes to the active energy accumu-
lation. When ABSAM (Bit 0) in the ACCMODE register
(Address 0x0F) is set, the absolute active power is used for the
active energy accumulation (see the Watt Absolute Accumulation
Mode section).
The output of the multiplier is divided by the value in the WDIV
register (Address 0x24). If the value in the WDIV register is equal
to 0, the internal active energy register is divided by 1. WDIV is an
8-bit, unsigned register. After dividing by WDIV, the active 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 active energy register (WATTHR, Address 0x01[23:0]).
A read to the RWATTHR register (Address 0x02) returns the
contents of the WATTHR register, and the upper 24 bits of the
internal register are cleared. As shown in Figure 66, the active
power signal is accumulated in an internal 49-bit, signed register.
The active power signal can be read from the waveform register
by setting the WAVMODE register (Address 0x0D) and setting
the WFSM bit (Bit 5) in the Interrupt Enable 3 SFR (MIRQENH,
Address 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, and 3.2 kSPS.
WGAIN[11:0]
WDIV[7:0]
LPF2
CURRENT
CHANNEL
VOLTAGE
CHANNEL
OUTPUT LPF2
TIME (nT)
5
MCLK
T
ACTIVE POWER
SIGNAL
+
+
WATTHR[23:0]
OUTPUTS FROM THE LPF2 ARE
ACCUMULATED (INTEGRATED) IN
THE INTERNAL ACTIVE ENERGY REGISTER
UPPER 24 BITS ARE
ACCESSIBLE THROUGH
WATTHR[23:0] REGISTER
23 0
48 0
%
WATTOS[15:0]
2
6
sgn
2
5
2
–6
2
–7
2
–8
+
+
FOR WAVEFORM
SAMPLING
TO
DIGITAL-TO-FREQUENCY
CONVERTER
WAVEFORM
REGISTER
VALUES
07411-041
Figure 66. Active Energy Calculation