AS8228 Ver la hoja de datos (PDF) - austriamicrosystems AG

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AS8228

Highly Integrated Single Phase 2-Current Energy Metering Integrated Circuits with Microcontroller, RTC, Programmable Multi-Purpose I/Os and LCD Driver

austriamicrosystems AG 

Data Sheet AS8218 / AS8228

Phase Correction

The DSP provides phase correction of the two current channels (i1 and i2) by means of the Sinc3 decimation

filters in the phase correction block. Only one of the phase correction settings (pcorr_i1 or pcorr_i2) is valid at

a time, depending on which current (i1 or i2) has been selected for the power calculation (sel_i).

The phase correction step size is dependent upon the main oscillator frequency selected (fosc) and the mains

frequency (fmains). Assuming a 3.579545MHz crystal oscillator frequency and 50Hz mains frequency, the phase

can be corrected in steps of 2.41’ or 0.04 degrees, which is equal to one oversampling sample, or one ‘unit’ in

the table below:

pcorr

Bit 8

0

0

Bit 7

1

1

Bit 6

1

1

Bit 5

1

1

Bit 4

1

1

Bit 3

1

1

Bit 2

1

1

Bit 1

1

1

Bit 0

1

0

0

0

1

1

1

1

1

1

1

0

0

1

1

1

1

1

1

0

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

0

1

1

0

0

0

0

0

0

1

1

1

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

1

1

0

0

0

0

0

0

0

0

One ‘unit’ equals a certain phase shift related to the mains frequency:

Phase Correction

[unit(s)]

255

254

…

127

126

…

2

1

0

-1

-2

…

-127

-128

…

-255

-256

1 unit = 360° × tovs = 360° × fmains = 360° × fmains

t mains

fovs

fosc / 8

Phase =#unit × 360° × fmains

fosc / 8

where fmains is the mains frequency and fOSC is

the oscillator frequency.

Example:

1unit = 360° × fmains

fosc / 8

255 units = 255 x 2.41’ = 10.26°

Revision 3.0, 31-May-06

Page 21 of 123

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