EVAL-ADE7763EB datasheet(26/56 Pages) AD

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ADE7763

Rev. A | Page 26 of 56

APOS[15:0]

WGAIN[11:0]

WDIV[7:0]

LPF2

CURRENT

CHANNEL

VOLTAGE

CHANNEL

TIME (nT)

CLKIN

ACTIVE POWER

SIGNAL

AENERGY[23:0]

OUTPUTS FROM THE LPF2 ARE

ACCUMULATED (INTEGRATED) IN

THE INTERNAL ACTIVE ENERGY REGISTER

UPPER 24 BITS ARE

ACCESSIBLE THROUGH

AENERGY[23:0] REGISTER

WAVEFORM

VALUES

Figure 55. Active Energy Calculation

Figure 55 shows the signal processing chain for the active power

calculation. The active power is calculated by low-pass filtering

the instantaneous power signal. Note that when reading the

waveform samples from the output of LPF2, the gain of the

active energy can be adjusted by using the multiplier and watt

gain register (WGAIN[11:0]). The gain is adjusted by writing a

twos complement 12-bit word to the watt gain register.

Equation 11 shows how the gain adjustment is related to the

contents of the watt gain register:

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

⎭

⎬

⎫

⎩

⎨

⎧ +

WGAIN

Power

Active

WGAIN

Output

(11)

For example, when 0x7FF is written to the watt gain register, the

power output is scaled up by 50%. 0x7FF = 2047d, 2047/212 = 0.5.

Similarly, 0x800 = –2048d (signed twos complement) and

power output is scaled by –50%. Each LSB scales the power

output by 0.0244%. Figure 56 shows the maximum code

(hexadecimal) output range for the active power signal (LPF2).

Note that the output range changes depending on the contents

of the watt gain register. The minimum output range is given

when the watt gain register contents are equal to 0x800, and the

maximum range is given by writing 0x7FF to the watt gain

energy) calculation.

0x1 3333

0xCCCD

0x6666

0xF 999A

0xF 3333

0xE CCCD

0x0 0000

POSITIVE

POWER

NEGATIVE

POWER

0x000

0x7FF

0x800

{WGAIN[11:0]}

ACTIVE POWER

CALIBRATION RANGE

Figure 56. Active Power Calculation Output Range

ENERGY CALCULATION

As stated earlier, power is defined as the rate of energy flow.

This relationship is expressed mathematically in Equation 12.

(12)

where:

P is power.

E is energy.

Conversely, energy is given as the integral of power.

∫

= Pdt

(13)

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