ADE7880 digital filter phase lag calculation.

Dear Sir/Madam,

We are developing a high precision electric meter with ADE7880. As I attached the zero crossing section paragraph of datasheet, I did not understand how did you calculate the error of ZX detection as 0.0703° for 50 Hz with 80 Hz pole and 356 KHz clock frequency?

I wonder if you could explain or give a reference document, how we calculate it?

Best regards.

Mehmet Ali Ipin

mehmet.ipin@pavotek.com.tr

PAVOTEK 

The digital filter has a pole at 80 Hz and is clocked at 256 kHz.
As a result, there is a phase lag between the analog input signal (one of IA, IB, IC, VA, VB, and VC) and the output of LPF1.
The error in ZX detection is 0.0703° for 50 Hz systems (0.0843°
for 60 Hz systems). The phase lag response of LPF1 results in a
time delay of approximately 31.4°