ade7169f16 Analog Devices, Inc., ade7169f16 Datasheet - Page 53

• Manufacturer Part Number: ade7169f16
• Description: Single-phase Energy Measurement Ic With 8052 Mcu, Rtc And Lcd Driver
• Manufacturer: Analog Devices, Inc.

Preliminary Technical Data
The ADE7169F16 includes a no-load threshold feature on the
active energy that eliminates any creep effects in the meter. The
ADE7169F16 accomplishes this by not accumulating energy if
the multiplier output is below the no-load threshold. When the
active power is below the no-load threshold, the APNOLOAD
flag in the Interrupt Status Register 1 SFR (MIRQSTL, 0xDC) is
set. If the APNOLOAD bit is set in the Interrupt Enable
Register 1 SFR (MIRQENL, 0xD9), the 8052 core has a pending
ADE interrupt. The ADE interrupt stays active until the
APNOLOAD status bit is cleared—see Energy measurement
interrupts section.
The No-load threshold level is selectable by setting bits
Active Energy Calculation
As stated earlier, power is defined as the rate of energy flow.
This relationship can be expressed mathematically in Equation 12.
where:
P is power.
E is energy.
Conversely, energy is given as the integral of power.
The ADE7169F16 achieves 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
P
E
dE
dt
Pdt
CURRENT
CHANNEL
CHANNEL
VOLTAGE
T
ACTIVE POWER
LPF2
CLKIN
sgn
5
SIGNAL
TIME (nT)
WATTOS[15:0]
2
6
2
+
5
Figure 39. ADE7169F16 Active Energy Calculation
+
2
WAVEFORM
REGISTER
-6
VALUES
2
-7
2
-8
Rev. PrD | Page 53 of 140
FOR WAVEF0RM
SAMPLING
WGAIN[11:0]
(12)
(13)
DIGITAL TO FREQUENCY
WDIV[7:0]
CONVERTER
APNOLOAD in the NLMODE register (0x0E). Setting these
bits to 0b00 disable the no-load detection and setting them to
0b01, 0b10 or 0b11 set the no-load detection threshold to
0.015%, 0.0075% and 0.0037% of the full-scale output frequency
of the multiplier respectively. The IEC62053-21 specification,
states that the meter must start up with a load equal to or less
than 0.4% Ib. If the nominal voltage input and the maximum
current represent 50% of the full scale ADC input and Imax =
400% of Ib, the ADE7169F16 no-load threshold options
translate to 0.24% of Ib, 0.12% of Ib and 0.06% of Ib
respectively.
this internal register. This discrete time accumulation or
summation is equivalent to integration in continuous time.
Equation 14 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 ADE7169F16 is 1.22µs (5/MCLK). As well as
calculating the energy, this integration removes any sinusoidal
components that might be in the active power signal. Figure 39
shows this discrete time integration or accumulation. The active
power signal in the waveform register is continuously added to
the internal active energy register.
%
TO
+
+
E
48
23
p t dt
WATTHR[23:0]
( )
OUTPUTS FROM THE LPF2 ARE
ACCUMULATED (INTEGRATED) IN
THE INTERNAL ACTIVE ENERGY REGISTER
Lim
t
0
0
n
UPPER 24 BITS ARE
ACCESSIBLE THROUGH
WATTHR[23:0] REGISTER
1
p nT
(
)
T
0
ADE7169F16
(14)