CS5467 datasheet(16/46 Pages) CIRRUS

16 / 46 page

CS5467

DS714A1

ADVANCE RELEASE

The CS5467 calculates the reactive power (QTrig,

Q2Trig) utilizing trigonometric identities, using the formu-

The average reactive power calculation (QAvg, Q2Avg) is

generated by averaging the voltage and multiplying that

value by the current measurement with a 90° phase dif-

ference between the two. The 90° phase shift is realized

by applying an IIR digital filter in the voltage channel to

obtain quadrature voltage (see Figure 3 and 4). This fil-

ter will give exactly -90° phase shift across all frequen-

cies, and utilizes epsilon (

ε) to achieve unity gain at the

line frequency.

The instantaneous quadrature voltage (VQ, V2Q) and

current (I, I2) samples are multiplied to obtain the in-

stantaneous quadrature power (Q, Q2). The product is

then averaged over N conversions, utilizing the formula

The peak current (Ipeak, I2peak) and peak voltage (Vpeak,

V2peak) are the instantaneous current and voltage, re-

spectively, with the greatest magnitude detected during

the previous computation cycle. Active, apparent, reac-

tive, and fundamental power are updated every compu-

tation cycle.

4.4 Linearity Performance

The linearity of the VRMS, IRMS, active, reactive, and

power-factor power measurements (before calibration)

will be within ±0.1% of reading over the ranges speci-

fied, with respect to the input voltage levels required to

cause full-scale readings in the IRMS and VRMS regis-

ters. Refer to Accuracy Specifications on page 7.

Until the CS5467 is calibrated, the accuracy of the

CS5467 (with respect to a reference line-voltage and

line-current level on the power mains) is not guaranteed

Trig

Active

–

Avg

∑

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CS5467 Datasheet(PDF) 16 Page - Cirrus Logic