ADE7880 datasheet(65/104 Pages) AD

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Data Sheet

ADE7880

Rev. A | Page 65 of 104

the

mputes the instantaneous values of all phase powers:

active, reactive, or apparent powers under steady load conditions.

This output frequency can provide a simple, single-wire,

optically isolated interface to external calibration equipment.

Figure 87 illustrates the energy-to-frequency conversion in

ADE7880.

The DSP co

total active, fundamental active, fundamental reactive, and

apparent. The process in which the energy is sign accumulat

in various xWATTHR, xFVARHR, and xVAHR registers has

already been described in the energy calculation sections: Acti

Energy Calculation, Fundamental Reactive Energy Calculation,

and Apparent Energy Calculation. In the energy-to-frequency

conversion process, the instantaneous powers generate signals

at the frequency output pins (CF1, CF2, and CF3). One digital-

to-frequency converter is used for every CFx pin. Every converter

sums certain phase powers and generates a signal proportional

to the sum. Two sets of bits decide what powers are converted.

First, Bits[2:0] (TERMSEL1[2:0]), Bits[5:3] (TERMSEL2[2:0]),

and Bits[8:6] (TERMSEL3[2:0]) of the COMPMODE register

decide which phases, or which combination of phases, are added.

The TERMSEL1 bits refer to the CF1 pin, the TERMSEL2 bits

refer to the CF2 pin, and the TERMSEL3 bits refer to the CF3

pin. The TERMSELx[0] bits manage Phase A. When set to 1,

Phase A power is included in the sum of powers at the CFx

converter. When cleared to 0, Phase A power is not included.

The TERMSELx[1] bits manage Phase B, and the TERMSELx[2]

bits manage Phase C. Setting all TERMSELx bits to 1 means all

3-phase powers are added at the CFx converter. Clearing all

TERMSELx bits to 0 means no phase power is added and no

CF pulse is generated.

Second, Bits[2:0] (CF1SEL[2:0]), Bits[5:3] (CF2SEL[2:0]), and

Bits[8:6] (CF3SEL[2:0]) in the CFMODE register decide what

type of power is used at the inputs of the CF1, CF2, and CF3

converters, respectively. Table 23 shows the values that CFxSEL

can have: total active, apparent, fundamental active, or fundamental

reactive powers.

Table 23. CFxSEL Bits Description

CFxSEL

Description

Registers Latched When CFxLATCH = 1

000

CFx signal proportional to the sum of total phase active powers

AWATTHR, BWATTHR, CWATTHR

001

Reserved

010

CFx signal proportional to the sum of phase apparent powers

AVAHR, BVAHR, CVAHR

011

CFx signal proportional to the sum of fundamental phase active

powers

AFWATTHR, BFWATTHR, CFWATTHR

100

CFx signal proportional to the sum of fundamental phase reactive

powers

AFVARHR, BFVARHR, CFVARHR

101 to 111

Reserved

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