ADE7569 datasheet(53/136 Pages) AD

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Preliminary Technical Data

ADE7566/ADE7569

Rev. PrA | Page 53 of 136

Figure 53 shows this energy accumulation for full-scale signals

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

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 ADE7566/ADE7569. As shown, the

fastest integration time occurs when the watt gain register is set

to maximum full scale, that is, 0x7FF.

0x00,0000

0x7F,FFFF

0x3F,FFFF

0x40,0000

0x80,0000

WATTHR[23:0]

6.82

3.41

10.2

13.7

TIME (Minutes)

WGAIN = 0x7FF

WGAIN = 0x000

WGAIN = 0x800

Figure 53. 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 (0x800000) and continue to increase in value when the

power or energy flow is positive (see Figure 53). 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 ADE7566/ADE7569

can be configured to issue an ADE interrupt to the 8052 core

when the active energy register is half-full (positive or negative)

or when an overflow or underflow occurs.

Integration Time under Steady Load

As mentioned in the Active Energy Calculation section, the

discrete time sample period (T) for the accumulation register is

1.22 μs (5/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 50). The

maximum positive value that can be stored in the internal

49-bit register is 248 (or 0xFFFF,FFFF,FFFF) before it overflows.

The integration time under these conditions when WDIV = 0 is

calculated in the following equation:

Time =

min

sec

409

xCCCCD

FFFF

FFFF,

xFFFF,

(16)

When WDIV is set to a value different than 0, the integration

time varies, as shown in Equation 17.

Time = TimeWDIV = 0 × WDIV

(17)

Active Energy Accumulation Modes

Watt Signed Accumulation Mode

The ADE7566/ADE7569 active energy default accumulation

mode is a watt-signed accumulation based on the active power

information.

Watt Positive-Only Accumulation Mode

The ADE7566/ADE7569 are placed in watt positive-only

accumulation mode by setting the POAM bit in the ACCMODE

done for positive power, ignoring any occurrence of negative

power above or below the no-load threshold (see Figure 54).

The CF pulse also reflects this accumulation method when in

this mode. The default setting for this mode is off. Detection of

the transitions in the direction of power flow and detection of

no-load threshold are active in this mode.

POS

INTERRUPT STATUS REGISTERS

NEG

APSIGN FLAG

NO-LOAD

THRESHOLD

ACTIVE POWER

NO-LOAD

THRESHOLD

ACTIVE ENERGY

Figure 54. Energy Accumulation in Positive-Only Accumulation Mode

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