ADE7763ARS datasheet(27/56 Pages) AD

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ADE7763

Rev. A | Page 27 of 56

FOR WAVEFORM

ACCUMULATION

LPF2

0x1 9999

0x19 999A

0x00 0000

INSTANTANEOUS

POWER SIGNAL – p(t)

FOR WAVEF0RM

SAMPLING

0xC CCCD

CURRENT SIGNAL – i(t)

HPF

VOLTAGE SIGNAL– v(t)

MULTIPLIER

APOS[15:0]

sgn

2-6 2-7 2-8

WGAIN[11:0]

Figure 57. Active Power Signal Processing

The ADE7763 achieves the integration of the active power

signal by continuously accumulating the active power signal in

an internal unreadable 49-bit energy register. The active energy

internal register. This discrete time accumulation or summation

is equivalent to integration in continuous time. Equation 14

expresses this relationship.

()

(

)

p t dt

Lim

p nT

∞

→

⎧⎫

⎨

⎩

⎭

∑

∫

⎬

(14)

where:

n is the discrete time sample number.

T is the sample period.

The discrete time sample period (

T) for the accumulation

energy, this integration removes any sinusoidal components

that might be in the active power signal.

Figure 57 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 which 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 57,

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 MODE[14:13] = 0, 0 and setting

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

Channel 1 and Channel 2 waveform sampling modes, the

waveform data is available at sample rates of 27.9 kSPS, 14 kSPS,

7 kSPS, or 3.5 kSPS—see Figure 44.

Figure 58 shows this energy accumulation for full-scale signals

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

minimum time for 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. As

shown, the fastest integration time occurs when the watt gain

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

Figure 58. Energy Register Rollover Time for Full-Scale Power

(Minimum and Maximum Power Gain)

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

negative (0x80 0000) and continue increasing in value when the

power or energy flow is positive—see Figure 58. Conversely, if

the power was negative, the energy register would underflow to

full-scale positive (0x7F FFFF) and continue decreasing in

value.

By using the interrupt enable register, the ADE7763 can be

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

overflow or underflow occurs.

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