ADE7166 datasheet(60/144 Pages) AD

60 / 144 page

ADE7566/ADE7569/ADE7166/ADE7169

Rev. A | Page 60 of 144

ACTIVE ENERGY CALCULATION

As stated in the Active Power Calculation section, power is

defined as the rate of energy flow. This relationship can be

expressed mathematically in Equation 13.

(13)

where:

is power.

is energy.

Conversely, energy is given as the integral of power.

∫

)

(

(14)

The ADE7566/ADE7569/ADE7166/ADE7169 achieve the

integration of the active power signal by continuously accumu-

lating the active power signal in an internal, nonreadable, 49-bit

energy register. The register (WATTHR[23:0]) represents the

upper 24 bits of this internal register. This discrete time

accumulation or summation is equivalent to integration in

continuous time. Equation 15 expresses the relationship.

⎭

⎬

⎫

⎩

⎨

⎧

∑

∫

∞

→

)

(

lim

)

(

(15)

where:

is the discrete time sample number.

is the sample period.

The discrete time sample period (T) for the accumulation

(5/MCLK). In addition to calculating the energy, this

integration removes any sinusoidal components that may be in

the active power signal.

shows this discrete time

integration or accumulation. The active power signal in the

waveform register is continuously added to the internal active

energy register.

The active energy accumulation depends on the setting of the

POAM and ABSAM bits in the ACCMODE register (0x0F).

When both bits are cleared, the addition is signed and, therefore,

negative energy is subtracted from the active energy contents.

When both bits are set, the ADE7566/ADE7569/ADE7166/

ADE7169 are set to be in the more restrictive mode, the positive-

only accumulation mode.

When POAM in the ACCMODE register (0x0F) is set, only

positive power contributes to the active energy accumulation.

When ABSAM in the ACCMODE register (0x0F) is set, the

absolute active power is used for the active energy accumulation

(see the Watt Absolute Accumulation Mode section).

The output of the multiplier is divided by the value in the

WDIV register. If the value in the WDIV register is equal to 0,

the internal active energy register is divided by 1. WDIV is an

8-bit unsigned register. After dividing by WDIV, the active

energy is accumulated in a 49-bit internal energy accumulation

a read to the active energy register (WATTHR[23:0]). A read to

the RWATTHR register returns the content of the WATTHR

As shown in Figure 65, the active power signal is accumulated

in an internal 49-bit signed register. The active power signal can

be read from the waveform register by setting the WAVMODE

SFR (MIRQENH, 0xDB). Like the current and voltage channels

waveform sampling modes, the waveform data is available at

sample rates of 25.6 kSPS, 12.8 kSPS, 6.4 kSPS, or 3.2 kSPS.

Figure 65

WGAIN[11:0]

WDIV[7:0]

LPF2

CURRENT

CHANNEL

VOLTAGE

CHANNEL

TIME (nT)

CLKIN

ACTIVE POWER

SIGNAL

WATTHR[23:0]

OUTPUTS FROM THE LPF2 ARE

ACCUMULATED (INTEGRATED) IN

THE INTERNAL ACTIVE ENERGY REGISTER

UPPER 24 BITS ARE

ACCESSIBLE THROUGH

WATTHR[23:0] REGISTER

WATTOS[15:0]

sgn

2–6 2–7 2–8

FOR WAVEFORM

SAMPLING

DIGITAL-TO-FREQUENCY

CONVERTER

WAVEFORM

VALUES

Figure 65. Active Energy Calculation

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