ADE7758ARWZ Analog Devices Inc, ADE7758ARWZ Datasheet - Page 40

• Manufacturer Part Number: ADE7758ARWZ
• Description: IC ENERGY METERING 3PHASE 24SOIC
• Manufacturer: Analog Devices Inc

Specifications of ADE7758ARWZ

• Input Impedance: 380 KOhm
• Measurement Error: 0.1%
• Voltage - I/o High: 2.4V
• Voltage - I/o Low: 0.8V
• Current - Supply: 8mA
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (0.300", 7.50mm Width)
• Meter Type: 3 Phase
• Ic Function: Poly Phase Multifunction Energy Metering IC
• Supply Voltage Range: 4.75V To 5.25V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: SOIC
• No. Of Pins: 24
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADE7758
Apparent Energy Calculation
Apparent energy is defined as the integral of apparent power.
Similar to active and reactive energy, the ADE7758 achieves the
integration of the apparent power signal by continuously
accumulating the apparent power signal in the internal 41-bit,
unsigned accumulation registers. The VA-hr registers (AVAHR,
BVAHR, and CVAHR) represent the upper 16 bits of these
internal registers. This discrete time accumulation or
summation is equivalent to integration in continuous time.
Equation 42 expresses the relationship
where:
n is the discrete time sample number.
T is the sample period.
Figure 75 shows the signal path of the apparent energy accumu-
lation. The apparent power signal is continuously added to the
internal apparent energy register. The average apparent power is
divided by the content of the VA divider register before it is
added to the corresponding VA-hr accumulation register. When
the value in the VADIV[7:0] register is 0 or 1, apparent power is
accumulated without any division. VADIV is an 8-bit unsigned
register that is useful to lengthen the time it takes before the
VA-hr accumulation registers overflow.
Apparent Energy = ∫ S ( t )dt
Apparent
Energy
VRMS
50Hz
60Hz
IRMS
0x1C82B
0x174BAC
0x17F263
CURRENT RMS SIGNAL
0x00
=
VOLTAGE RMS SIGNAL
∫
0x0
0x0
S
( )
t
dt
=
Lim
T
→
0
⎧
⎨
⎩
n
∑
MULTIPLIER
∞
=
0
S
( )
nT
Figure 75. ADE7758 Apparent Energy Accumulation
×
LPF2
T
⎫
⎬
⎭
VAG[11:0]
(41)
(42)
Rev. D | Page 40 of 72
VADIV[7:0]
%
Similar to active or reactive power accumulation, the fastest
integration time occurs when the VAGAIN registers are set to
maximum full scale, that is, 0x7FF. When overflow occurs, the
content of the VA-hr accumulation registers can roll over to 0
and continue increasing in value.
By setting the VAEHF bit (Bit 2) of the mask register, the ADE7758
can be configured to issue an interrupt ( IRQ ) when the MSB of
any one of the three VA-hr accumulation registers has changed,
indicating that the accumulation register is half full.
Setting the RSTREAD bit (Bit 6) of the LCYMODE register
enables a read-with-reset for the VA-hr accumulation registers;
that is, the registers are reset to 0 after a read operation.
Integration Time Under Steady Load
The discrete time sample period ( T ) for the accumulation register
is 0.4 μs (4/CLKIN). With full-scale, 60 Hz sinusoidal signals on
the analog inputs and the VAGAIN registers set to 0x000, the
average word value from each LPF2 is 0xB9954. The maximum
value that can be stored in the apparent energy register before it
overflows is 2
added to the internal register, which can store 2
FFFF, FFFF before it overflows, the integration time under these
conditions with VADIV = 0 is calculated as
When VADIV is set to a value different from 0, the time before
overflow is scaled accordingly, as shown in Equation 44.
+
+
Time = Time ( VADIV = 0) × VADIV
Time
40
15
=
VARHR[15:0]
0x1FF,
APPARENT POWER IS
ACCUMULATED (INTEGRATED) IN
THE VA-HR ACCUMULATION REGISTERS
16
− 1 or 0xFFFF. As the average word value is first
0xB9954
FFFF,
0
FFFF
×
0.4
μs
0
=
1.157
41
− 1 or 0x1FF,
sec
(43)
(44)