ADE7753ARSZ datasheet(30/60 Pages) AD

30 / 60 page

ADE7753

Rev. C | Page 30 of 60

FOR WAVEFORM

ACCUMULATIOIN

LPF2

0x19999

0x19999A

0x000000

INSTANTANEOUS

POWER SIGNAL – p(t)

FOR WAVEF0RM

SAMPLING

0xCCCCD

CURRENT SIGNAL – i(t)

HPF

VOLTAGE SIGNAL– v(t)

MULTIPLIER

APOS [15:0]

sgn

2-6 2-7 2-8

02875-0-064

WGAIN[11:0]

Figure 65. Active Power Signal Processing

The ADE7753 achieves the integration of the active power signal by

continuously accumulating the active power signal in an internal

nonreadable 49-bit energy register. The active energy register

(AENERGY[23:0]) represents the upper 24 bits of this internal

equivalent to integration in continuous time. Equation 14

expresses the relationship.

⎭

⎬

⎫

⎩

⎨

⎧

∑

∫

∞

→

)

(

)

(

Lim

(14)

where:

is the discrete time sample number.

is the sample period.

The discrete time sample period (T) for the accumulation

calculating the energy, this integration removes any sinusoidal

components that might be in the active power signal. Figure 65

shows this discrete time integration or accumulation. The active

power signal in the waveform register is continuously added to

the internal active energy register. This addition is a signed

addition; therefore negative energy is subtracted from the active

energy contents. The exception to this is when POAM is

selected in the MODE[15:0] register. In this case, only positive

energy contributes to the active energy accumulation—see the

Positive-Only Accumulation Mode section.

The output of the multiplier is divided by WDIV. If the value in

the WDIV register is equal to 0, then the internal active energy

After dividing by WDIV, the active energy is accumulated in a

49-bit internal energy accumulation register. The upper 24 bits

of this register are accessible through a read to the active energy

returns the content of the AENERGY register and the upper 24

bits of the internal register are cleared. As shown in Figure 65, the

active power signal is accumulated in an internal 49-bit signed

bit (Bit 3) in the interrupt enable register to 1. Like the Channel 1

and Channel 2 waveform sampling modes, the waveform date is

available at sample rates of 27.9 kSPS, 14 kSPS, 7 kSPS, or

3.5 kSPS—see Figure 52.

Figure 66 shows this energy accumulation for full-scale signals

(sinusoidal) on the analog inputs. The three curves displayed

illustrate the minimum period of time it takes the energy register

to roll over when the active power gain register contents are

0x7FF, 0x000, and 0x800. The watt gain register is used to carry

out power calibration in the ADE7753. As shown, the fastest

integration time occurs when the watt gain register is set to

maximum full scale, i.e., 0x7FF.

0x00,0000

0x7F,FFFF

0x3F,FFFF

0x40,0000

0x80,0000

AENERGY [23:0]

6.2

12.5

TIME (minutes)

WGAIN = 0x7FF

WGAIN = 0x000

WGAIN = 0x800

02875-0-065

Figure 66. Energy Register Rollover Time for Full-Scale Power

(Minimum and Maximum Power Gain)

Note that the energy register contents rolls over to full-scale

negative (0x800000) and continues to increase in value when

the power or energy flow is positive—see Figure 66. Conversely,

if the power is negative, the energy register underflows to full-

scale positive (0x7FFFFF) and continues to decrease in value.

By using the interrupt enable register, the ADE7753 can be

configured to issue an interrupt (IRQ) when the active energy

an overflow or 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 and the

WGAIN register set to 0x000, the average word value from each

LPF2 is 0xCCCCD—see Figure 61. The maximum positive

value that can be stored in the internal 49-bit register is 248 or

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