ade7166 Analog Devices, Inc., ade7166 Datasheet - Page 60

• Manufacturer Part Number: ade7166
• Description: Single-phase Energy Measurement Ic With 8052 Mcu, Rtc, And Lcd Driver
• Manufacturer: Analog Devices, Inc.

ADE7566/ADE7569/ADE7166/ADE7169
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/ADE7166/ADE7169 achieve the
integration of the active power signal by continuously accumu-
lating the active power signal in an internal, nonreadable, 49-bit
energy register. The 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/ADE7166/ADE7169 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.
P =
E
E
=
=
∫
dE
∫
dt
P
p
) (
t
) (
t
CURRENT
CHANNEL
CHANNEL
VOLTAGE
dt
dt
=
lim
t
→
0
Figure 65
⎧
⎨
⎩
∑
n
∞
=
T
1
p
(
nT
shows this discrete time
ACTIVE POWER
)
LPF2
CLKIN
sgn
×
SIGNAL
5
TIME (nT)
T
WATTOS[15:0]
⎫
⎬
⎭
2
6
2
+
5
+
WAVEFORM
2
REGISTER
–6
VALUES
2
–7
Figure 65. Active Energy Calculation
2
–8
FOR WAVEFORM
SAMPLING
WGAIN[11:0]
Rev. A | Page 60 of 144
(13)
(14)
(15)
WDIV[7:0]
%
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 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/ADE7166/
ADE7169 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 65, 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 3
SFR (MIRQENH, 0xDB). Like the current and voltage channels
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.
TO
DIGITAL-TO-FREQUENCY
CONVERTER
+
+
48
23
WATTHR[23:0]
OUTPUTS FROM THE LPF2 ARE
ACCUMULATED (INTEGRATED) IN
THE INTERNAL ACTIVE ENERGY REGISTER
0
UPPER 24 BITS ARE
ACCESSIBLE THROUGH
WATTHR[23:0] REGISTER
0