ADE7753ARS datasheet(29/60 Pages) AD

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ADE7753

Rev. C | Page 29 of 60

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

02875-0-063

Figure 63. ADE7753 Active Energy Calculation

Figure 63 shows the signal processing chain for the active power

calculation in the ADE7753. As explained, 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 64 shows the maximum code (in hex) 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 register. This can be used to

calibrate the active power (or energy) calculation in the ADE7753.

0x133333

0xCCCCD

0x66666

0xF9999A

0xF33333

0xECCCCD

0x00000

POSITIVE

POWER

NEGATIVE

POWER

0x000

0x7FF

0x800

{WGAIN[11:0]}

ACTIVE POWER

CALIBRATION RANGE

02875-0-062

Figure 64. Active Power Calculation Output Range

ENERGY CALCULATION

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

This relationship can be 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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