ADE7758ARWZ Analog Devices Inc, ADE7758ARWZ Datasheet - Page 55

• 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

Step 1: Set configuration registers for zero crossings on all
phases by writing the value 0x38 to the LCYCMODE register
(0x17). This sets all of the ZXSEL bits to Logic 1.
Step 2: Set the interrupt mask register for zero-crossing
detection on all phases by writing 0xE00 to the MASK[0:24]
register (0x18). This sets all of the ZX bits to Logic 1.
Step 3: Set up the calibration system for one of the two test
conditions: I
Step 4: Read the rms registers after the zero-crossing interrupt
and take an average of N samples. This is recommended to get
the most stable rms readings. This procedure is detailed in
Figure 84: Steps 4a through 4e.
Step 4a. Choose the number of samples, N, to be averaged.
Step 4b. Reset the interrupt status register by reading RSTATUS
(0x1A).
Step 4c. Wait for the zero-crossing interrupt. When the zero-
crossing interrupt occurs, move to Step 4d.
Step 4d. Read the xIRMS and xVRMS registers. These values
will be averaged in Step 4e.
Step 4e: Average the N samples of xIRMS and xVRMS. The
averaged values will be used in Step 5.
Step 5: Write to the xVRMSOS (0x33 to 0x35) and xIRMSOS
(0x36 to 0x38) registers according to the following equations:
where:
I
I
IRMS
without offset correction for the inputs I
respectively.
where:
V
V
MIN
TEST
MIN
NOM
is the full scale current/500.
is the test current.
is the full scale voltage/20
xIRMSOS
16384
xVRMSOS
64
is the nominal line voltage.
IMIN
1
1
×
and IRMS
V
×
NOM
TEST
(
I
TEST
=
and V
=
×
VRMS
2
ITEST
×
NOM
IRMS
V
are the current rms register values
VMIN
MIN
, and I
IMIN
I
–
–
MIN
V
V
FULLSCALE
2
NOM
MIN
2
) (
–
–
I
×
I
TEST
MIN
VRMS
/500 and V
MIN
2
2
×
and I
IRMS
VNOM
TEST
ITEST
FULLSCALE
,
2
)
/20.
(77)
(78)
Rev. D | Page 55 of 72
VRMS
without offset correction for the input V
respectively.
Example: Calibration of RMS Offsets
For this example, I
V
Twenty readings are taken synchronous to the zero crossings of
all three phases at each current and voltage to determine the
average xIRMS and xVRMS readings. At I
example ADE7758 meter gets an average AIRMS (0x0A)
reading of 148242.2 and 744570.8 in the AVRMS (0x0D)
register. Then the current is set to I
260 mA. At I
V
AVRMS of 86362.36. Using this data, −15d is written to
AIRMSOS (0x36) and −31d is written to AVRMSOS (0x33)
registers according to the Equation 77 and Equation 78.
This example shows the calculations and measurements for
Phase A only. However, all three xIRMS and xVRMS registers
can be read simultaneously to compute the values for each
xIRMSOS and xVRMSOS register.
CHECKSUM REGISTER
The ADE7758 has a checksum register CHKSUM[7:0] (0x7E)
to ensure the data bits received in the last serial read operation
are not corrupted. The 8-bit checksum register is reset before
the first bit (MSB of the register to be read) is put on the DOUT
pin. During a serial read operation, when each data bit becomes
available on the rising edge of SCLK, the bit is added to the
checksum register. In the end of the serial read operation, the
contents of the checksum register are equal to the sum of all the
1s in the register previously read. Using the checksum register, the
user can determine if an error has occurred during the last read
operation. Note that a read to the checksum register also
generates a checksum of the checksum register itself.
−
AIRMSOS
16384
AVRMSOS
64
1
FULLSCALE
MIN
14
1
CONTENT OF REGISTERS
×
8 .
= V
(
220
VMIN
=
×
FULLSCALE
−
(
(N-BYTES)
10
Figure 85. Checksum Register for Serial Interface Read
= 500 V, Power Factor = 1, and Frequency = 50 Hz.
15
×
and VRMS
=
2
86362.36
=
MIN
=
×
0xFF2
3885.68
, the average AIRMS reading is 3885.68. At
/20 or 25 V, the example meter gets an average
(
25
TEST
–
) (
VNOM
(
–
= 10 A, I
. 0
220
2
) (
260
25
–
)
are the voltage rms register values
×
. 0
–
744570.8
260
10
MAX
2
2
)
×
= 100 A, V
MIN
148242.2
)
= I
CHECKSUM
REGISTER
=
MIN
FULLSCALE
−
TEST
30
and V
2
NOM
and V
9 .
)
=
=
DOUT
/500 or
NOM
= 220 V,
−
ADE7758
ADDR: 0x7E
31
NOM
,
=
, the
0xFE1