FS7755

Rev. 1.1

13/22

and:

∑

∞

≠1

h

(4)

As can be seen from Equation (4) above, 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

calculation 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 since it is made up of a series of

pure sinusoids.

Note:

The input bandwidth of the analog inputs is 14 kHz with a master clock frequency of 3.579545MHz.

4

Analog Inputs

4.1 Channel V1 (Current Channel)

The voltage output from the current transducer is connected to the FS7755 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 1 should be less than ±470mV (330mV rms for a pure

sinusoidal signal) for specified operation. Note that Channel 1 has a programmable gain amplifier (PGA)

with user selectable gain of 1, 2, 8, or 16 (see Table I). These gains facilitate easy transducer interfacing.

Fig7 illustrates the maximum signal levels on V1P and V1N. The maximum differential voltage is ±470mV

divided by the gain selection. The differential voltage signal on the inputs must be referenced to a common

mode, e.g., AGND. The maximum common mode signal is ±100 mV as shown in Fig7.

V1P

V1N

AGND

VCM

V1

Differential Input

470mV Max

Common Mode

100mV Max

±

±

V1

VCM

-470mV

+470mV

Fig7 Maximum Signal Levels (Channel 1, Gain = 1)

G1

G0

Gain

Maximum

Differential Signal (mV)

0

0

1

±470

0

1

32

±15

1

0

8

±60

1

1

16

±30

Table I

Gain Selection for Channel 1