ADE7566ASTZF8-RL2 AD [Analog Devices], ADE7566ASTZF8-RL2 Datasheet - Page 52

• Manufacturer Part Number: ADE7566ASTZF8-RL2
• Description: Single-Phase Energy Measurement IC with 8052 MCU, RTC, and LCD Driver
• Manufacturer: AD [Analog Devices]

ADE7566/ADE7569
ACTIVE ENERGY CALCULATION
As stated in the Active Power Calculation section, power is
defined as the rate of energy flow. This relationship can be
expressed mathematically in Equation 13.
where:
P is power.
E is energy.
Conversely, energy is given as the integral of power.
The ADE7566/ADE7569 achieve the integration of the active
power signal by continuously accumulating the active power
signal in an internal, non readable, 49-bit energy register. The
active energy register (WATTHR[23:0]) represents the upper 24
bits of this internal register. This discrete time accumulation or
summation is equivalent to integration in continuous time.
Equation 15 expresses the relationship.
where:
n is the discrete time sample number.
T is the sample period.
The discrete time sample period (T) for the accumulation
register in the ADE7566/ADE7569 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 52 shows this discrete time integration or accumulation.
P =
E
E
=
=
∫
∫
dE
dt
P
p
) (
) (
t
t
CURRENT
CHANNEL
CHANNEL
VOLTAGE
dt
dt
=
Lim
t
→
0
⎧
⎨
⎩
∑
n
∞
=
1
T
p
(
nT
)
×
ACTIVE POWER
T
LPF2
CLKIN
sgn
⎫
⎬
⎭
SIGNAL
5
TIME (nT)
WATTOS[15:0]
2
6
2
+
5
+
WAVEFORM
2
REGISTER
–6
VALUES
2
–7
Figure 52. Active Energy Calculation
2
–8
FOR WAVEFORM
SAMPLING
WGAIN[11:0]
Rev. PrA | Page 52 of 136
(13)
(14)
(15)
WDIV[7:0]
%
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 the
POAM and ABSAM bits in the ACCMODE Register (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 ADE7566/ADE7569 are set to be in
the more restrictive mode, the positive only accumulation mode.
When POAM in the ACCMODE Register (0x0F) is set, only
positive power contributes to the active energy accumulation.
When ABSAM in the ACCMODE Register (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. 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[23:0]). A read to
the RWATTHR register returns the content of the WATTHR
register, and the upper 24 bits of the internal register are cleared.
As shown in Figure 52, 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 (0x0D) and setting the WFSM bit in the Interrupt Enable
Register 3 SFR (MIRQENH, 0xDB). Like the current and
voltage channels waveform sampling modes, the waveform date is
available at sample rates of 27.9 kSPS, 14 kSPS, 7 kSPS, or 3.5
kSPS.
TO
DIGITAL-TO-FREQUENCY
CONVERTER
+
+
48
23
WATTHR[23:0]
OUTPUTS FROM THE LPF2 ARE
ACCUMULATED (INTEGRATED) IN
THE INTERNAL ACTIVE ENERGY REGISTER
Preliminary Technical Data
0
UPPER 24 BITS ARE
ACCESSIBLE THROUGH
WATTHR[23:0] REGISTER
0