Question
The resolver that I have to drive is specified for 2500Hz. Looking at table 7(recommended excitation frequency vs. resolution) is shown that I've to selectthe 16bits configuration if I need to have an excitation frequency of 2.5KHz.What's happen If I select 12/14bits resolution (Res0/Res1) and I write FCWregister to generate a 2.5KHz waveform? In particular I need to use 2.5KHz asexcitation with an input bandwidth greater than 250Hz.
Answer
The AD2S1210 will be functional when the resolution and the excitationfrequency do not match up with the recommendations in Table 7.You may see a change in performance. I don’t have data to quantify this.
If you want greater than 250Hz bandwidth and a 2500Hz excitation, and if youwant to stay within the recommendations…Set the resolution to 14-bits. With an 8.192MHz CLKIN you get typically 900Hzbandwidth and a 3KHz lower recommendation on the excitation frequency.The 3kHz lower recommendation would scale with CLKIN frequency. You can scalethe CLKIN frequency by +/-25% so table 7 for 14-bits resolution would be with a6.144MHz CLKIN· Bandwidth = 675Hz· Min Frequency = 2250Hz· Max Frequency = 9kHz
Tracking rate would scale linearly also.And the excitation frequency. If you wanted to set exactly 2.5KHz excitationthen with a 6.144MHz you couldn’t250 * 0.75 * 13 = 2437.5Hz.But maybe that’s close enough or you can adjust the CLKIN frequency up a bit.