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ADE7769

Energy Metering IC with Integrated Oscillator and No-Load Indication

Analog Devices 

( ) ∞

i(t) = IO + 2 × ∑ Ih × sin hωt + βh

(3)

h≠o

where:

i(t) is the instantaneous current.

I0 is the dc component.

Ih is the rms value of current harmonic h.

βh is the phase angle of the current harmonic.

Using Equations 2 and 3, the real power (P) can be expressed in

terms of its fundamental real power (P1) and harmonic real

power (PH) as P = P1 + PH

where:

P1 = V1 × I1 cos φ 1

(4)

φ1 = α1 − β1

and

∞

PH = ∑Vh × Ih cos φh

(5)

h≠1

φh = αh − βh

In Equation 5, a harmonic real power component is generated

for every harmonic, provided that harmonic is present in both

the voltage and current waveforms. The power factor calcu-

lation has previously been shown to be accurate in the case of a

pure sinusoid. Therefore, the harmonic real power must also

correctly account for the power factor because it is made up of

a series of pure sinusoids.

Note that the input bandwidth of the analog inputs is 7 kHz at

the nominal internal oscillator frequency of 450 kHz.

ANALOG INPUTS

Channel V1 (Current Channel)

The voltage output from the current sensor is connected to the

ADE7769 here. Channel V1 is a fully differential voltage input.

V1P is the positive input with respect to V1N.

The maximum peak differential signal on Channel V1 should

be less than ±30 mV (21 mV rms for a pure sinusoidal signal)

for specified operation.

V1

+30mV

VCM

DIFFERENTIAL INPUT

±30mV MAX PEAK

COMMON-MODE

±6.25mV MAX

V1P

V1 V1N

VCM

–30mV

AGND

Figure 17. Maximum Signal Levels, Channel V1

ADE7769

Figure 17 shows the maximum signal levels on V1P and V1N.

The maximum differential voltage is ±30 mV. The differential

voltage signal on the inputs must be referenced to a common

mode, for example, AGND. The maximum common-mode

signal is ±6.25 mV, as shown in Figure 17.

Channel V2 (Voltage Channel)

The output of the line voltage sensor is connected to the

ADE7769 at this analog input. Channel V2 is a fully differential

voltage input with a maximum peak differential signal of

±165 mV. Figure 18 shows the maximum signal levels that can

be connected to the ADE7769 Channel V2.

V2

+165mV

VCM

DIFFERENTIAL INPUT

±165mV MAX PEAK

COMMON-MODE

±25mV MAX

V2P

V2 V2N

VCM

–165mV

AGND

Figure 18. Maximum Signal Levels, Channel V2

Channel V2 is usually driven from a common-mode voltage,

that is, the differential voltage signal on the input is referenced

to a common mode (usually AGND). The analog inputs of the

ADE7769 can be driven with common-mode voltages of up to

25 mV with respect to AGND. However, best results are

achieved using a common mode equal to AGND.

Typical Connection Diagrams

Figure 19 shows a typical connection diagram for Channel V1.

A shunt is the current sensor selected for this example because

of its low cost compared to other current sensors, such as the

current transformer (CT). This IC is ideal for low current meters.

SHUNT

RF

±30mV

V1P

CF

V1N

RF

CF

AGND

PHASE NEUTRAL

Figure 19. Typical Connection for Channel V1

Figure 20 shows a typical connection for Channel V2. Typically,

the ADE7769 is biased around the phase wire, and a resistor

divider is used to provide a voltage signal that is proportional to

the line voltage. Adjusting the ratio of RA, RB,B and RF is also a

convenient way of carrying out a gain calibration on a meter.

Rev. A | Page 11 of 20

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