AD2S1210 In 360 Degree Phase Lock Mode

I have a customer who is using the AD2S1210 Resolver-to-Digital Converter in extended phase lock mode. This is accomplished by setting bit D5=0 in the Control Register (see Table 22 on page 23 of datasheet). He is measuring 100 degrees of phase difference between the excitation frequency and the input. However in the Fault Register bit D1=1 (fault condition: out of phase lock range). So my questions are: 1. Is this normal every time phase is greater than 44 degrees (normal phase lock mode)? 2. Has anyone else encountered this and have an idea what may be the cause?

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    •  Analog Employees 
    on Sep 5, 2013 4:31 PM

    Hi Peter,

    We are attending your query. We'll get back to you with a reply.

    Regards,

    Johnny

  • 0
    •  Analog Employees 
    on Sep 6, 2013 11:53 AM

    Hi Peter,

    If you set it to 360 degrees, the D1 bit in the fault register can still be set. The reason behind this is - should the phase lock range is set to 360 degrees, the accuracy of the AD2S1210 is not affected if the phase between the excitation and the sine cosine signals does not exceed +/-44 degree. If you pass this range, the synthetic reference does not correct for the difference in phase beyond +/-44 degrees. The remaining phase difference will cause additional inaccuracy dependent on the phase, excitation frequency and rotation speed. You can find the its relationship to the equation found on Page 18 of the datasheet.

     

    The part will compensate up to +/-44 degrees to less than 10 degrees of phase shift. Anything above this causes additional error.

     

    Also to be aware if the phase lock range is set to 360 degrees and a LOS occurs, a reset must be issued to the AD2S1210 or else there is the risk that the position output will be 180 Degrees out of phase when the signals are reconnected.

    Regards,

    Johnny

  • Thanks for responding. The datasheet is somewhat misleading which is why I had to submit this question. Instead of the Fault Register bit D1 being labeled 'phase error exceeds phase lock range' maybe it should be called 'phase error exceeds +/-44 degrees'.

  • Hi Johnny.

    I have the same issue in my application.

    I am also using the AD2s1210 for the Tamagawa resolver.

    And a phase shift from the excitation to cos/sin input is 46 deg and even if I reset the fault, D1 was not cleared.

    Based on your answer, even though setting the phase lock range to 360 deg, the phase lock error will not be cleared, isn't it?

    You said that "The remaining phase difference will cause additional inaccuracy."

    For example, the rotation rate is 100 Hz and the reference (excitation) frequency is 10 kHz, then an error will be 46 deg * 100/10000 = 0.46 deg, isn't it?

    Is it a constant angle offset when speed is fixed?

    If this is the case, I would think it could be compensated easily in the DSP.

    Please advise.