CN0276 EXC filter design

Hi I have a doubt in CN0276.

In Fig. 12, the phase shift between EXC and SIN is about 40 degree, however, the filter design for EXC amplifier has about 180 degree phase shift, is there something that I miss? thanks.

Regards,

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  • 0
    •  Analog Employees 
    on Jan 24, 2020 1:35 AM

    Hi firman,

    Figure 12 is the phase shift between the AD2S1210 EXC and SIN pins which shows how the noise from EXC pins of AD2S1210 was improved.  This is because of the amplifiers which acts as an active filter found at the resolver excitation(which uses AD8692) and at the resolver sin/cos receiver(which uses AD8694). 

    Both amplifiers acts as an active filters configured as a multiple feedback (MFB) third order Butterworth lowpass filter.  The active filter has a gain of -1 which results to a 180° phase shift.  Since the resolver excitation and the resolver sin/cos receiver both have these active filter, the phase of the signal that pass-through ends up shifting back to 0°.

    Let me know if that answered your question.

    Cheers,

    Erbe       

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  • 0
    •  Analog Employees 
    on Jan 24, 2020 1:35 AM

    Hi firman,

    Figure 12 is the phase shift between the AD2S1210 EXC and SIN pins which shows how the noise from EXC pins of AD2S1210 was improved.  This is because of the amplifiers which acts as an active filter found at the resolver excitation(which uses AD8692) and at the resolver sin/cos receiver(which uses AD8694). 

    Both amplifiers acts as an active filters configured as a multiple feedback (MFB) third order Butterworth lowpass filter.  The active filter has a gain of -1 which results to a 180° phase shift.  Since the resolver excitation and the resolver sin/cos receiver both have these active filter, the phase of the signal that pass-through ends up shifting back to 0°.

    Let me know if that answered your question.

    Cheers,

    Erbe       

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