How to change AD7176-2 sinc3 filter notch frequency?

Hi,

I used the register 0x28000060 and 0x28008060, and both of them change the sample rate and output data rate to 250kHz. But the sinc3 filter notch frequency of them at 50kHz. How can I change sinc3 filter notch frequency to 250kHz?

Thanks,

Alexyv