Q
We want to have an error due to Phase shift of less then 1 lsb with these parameters: RotationRate=6000rpm ReferenceFrequency=10Khz. What is the maximun phase shift that can be tolerated between the reference excitation and the sin/cos signals.
A
The Error you are referring to is caused by the rotation of the resolver. Basically at high rotation rates the resolver starts to act like an electric motor and produces speed voltages. This are in quadrature to the main signal and result in an additional error through the RDC. The formula to calculate this error is on page 17 of the datasheet: Error = Phase shift x [rotation rate / reference frequency] The main factor in the formula is the Phase shift, which is the phase shift between the reference signal and the Sin/Cos inputs. This phase shift is primarily caused by the resolver itself i.e. resistance of the rotor coil causes a phase shift from what is applied to the rotor to what is then generated across the stators. The AD2S1200 internally generates a synthetic reference to compensate for this phase shift. It can reduce a phase shift of +/-45 degrees down to 10 degrees. However for you this is not quite enough as he would then have the following with the speed and freq conditions he outlined : Error = 10 degrees x [100rps / 10kHz] = 0.1 degrees = 6 arc min One lsb = 5.3 arc min. The reduce this error still further you need to further reduce the phase shift between the reference and the Sin/Cos signals. So after all that explanation the answer to your questions is: Error = Phase shift x [rotation rate / reference frequency] => Phase shift = Error x [reference freq / rotation rate] = [0.088 degrees] x [10,000/100] = 8.83 degrees. i.e. You need to keep the phase shift below 8.8 degrees to be able to keep the additional error below 1 lsb [5.3 arc min.]