ADE7759ARSRL Analog Devices Inc, ADE7759ARSRL Datasheet - Page 22

• Manufacturer Part Number: ADE7759ARSRL
• Description: IC ENERGY METERING 1PHASE 20SSOP
• Manufacturer: Analog Devices Inc

Specifications of ADE7759ARSRL

• Rohs Status: RoHS non-compliant
• Input Impedance: 390 KOhm
• Measurement Error: 0.1%
• Voltage - I/o High: 2.4V
• Voltage - I/o Low: 0.8V
• Current - Supply: 3mA
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-SSOP (0.200", 5.30mm Width)
• Meter Type: Single Phase
• For Use With: EVAL-ADE7759EBZ - BOARD EVALUATION FOR ADE7759

ADE7759
Figure 37. Energy Register Rollover Time for Full-Scale
Power (Minimum and Maximum Power Gain)
Note that the energy register contents will roll over to full-scale
negative (80,0000,0000h) and continue increasing in value when
the power or energy flow is positive—see Figure 37. Conversely, if
the power is negative, the energy register would underflow to full-
scale positive (7F, FFFF, FFFFh) and continue decreasing in
value. By using the interrupt enable register, the ADE7759
can be configured to issue an interrupt (IRQ) when the active
energy register is half-full (positive or negative) or when an
over/underflow occurs.
Integration Time under Steady Load
As mentioned in the last section, the discrete time sample
period (T) for the accumulation register is 1.1 µs (4/CLKIN).
With full-scale sinusoidal signals on the analog inputs, digital
integrator turned off, and the active power gain register set to
000h, the average word value from LPF2 is CCCD—see
Figures 34 and 35. The maximum value that can be stored in
the active energy register before it overflows is 2
7F,FFFF,FFFFh
3F,FFFF,FFFFh
00,0000,0000h
80,0000,0000h
40,0000,0000
AENERGY [39:0]
CURRENT CHANNEL
VOLTAGE CHANNEL
5.8s
11.5s
23s
15
SIGN 2
T
TIME – sec
20
6
Figure 36. Energy Calculation
2
CLKIN
APGAIN = 7FFh
APGAIN = 000h
APGAIN = 800h
5
39
4
TIME – nT
2
LPF2
4
or
2
ACTIVE POWER
3
SIGNAL = P
2
2
WAVEFORM
–22–
REGISTER
VALUES
APOS [15:0]
2
+
1
7F,FFFF,FFFFh. Therefore, the integration time under these
conditions is calculated as follows:
POWER OFFSET CALIBRATION
The ADE7759 also incorporates an active power offset regis-
ter (APOS[15:0]). This is a signed twos complement 16-bit
register that can be used to remove offsets in the active power
calculation—see Figure 36. An offset may exist in the power
calculation due to crosstalk between channels on the PCB or in
the IC itself. The offset calibration will allow the contents of the
active power register to be maintained at zero when no power is
being consumed.
The 256 LSBs (APOS = 0100h) written to the active power
offset register are equivalent to 1 LSB in the waveform sample
register, assuming the average value output from LPF2 to
store in the waveform register is CCCDh (52,429 in decimal)
when inputs on Channels 1 and 2 are both at full scale and
the digital integrator is turned off. At –60 dB down on Chan-
nel 1 (1/1000 of the Channel 1 full-scale input), the average
word value output from LPF2 is 52.429 (52,429/1,000). One
LSB in the waveform register has a measurement error of
1/52.429 × 100% = 1.9% of the average value. The active
power offset register has a resolution equal to 1/256 LSB of
the waveform register, thus the power offset correction reso-
lution is 0.007%/LSB (1.9%/256) at –60 dB. When the digital
integrator is turned on, the resolution of the LSB varies slightly
with the line frequency.
ENERGY-TO-FREQUENCY CONVERSION
ADE7759 also provides energy-to-frequency conversion for
calibration purposes. After initial calibration at manufacturing,
the manufacturer or end customer will often verify the energy
meter calibration. One convenient way to verify the meter cali-
bration is for the manufacturer to provide an output frequency
that is proportional to the energy or active power under steady
2
0
+
2
–1
Time
23
39
2
–2
2
–3
=
7
2
–4
F FFFF FFFFh
WAVEFORM [24:0]
WAVEFORM REGISTER VALUES ARE
ACCUMULATED (INTEGRATED) IN
THE ACTIVE ENERGY REGISTER
AENERGY [39:0]
,
2
–5
CCCDh
2
–6
2
,
–7
2
–8
0
×
1 1
.
0
0
µ
s
=
11 53
+
+
.
sec
onds
REV. A