Part Number:TIDA-01629
HI!
In this case, I think there are two problems.Maybe my understanding is incorrect, so I look forward to your help.
The first one is about the relationship between the bandwidth of control loop, sampling frequency and the bandwidth of analog circuit in front of SAR ADC.
The motor current control loop is generally equal to the switching frequency. Sometimes it can be twice the switching frequency.The switching frequency of Mosfet is generally less than 100KHz.According to Nyquist's law, in order to prevent frequency aliasing, the bandwidth of the anterior analog circuit of SAR ADC is required to be less than half of the sampling bandwidth of SAR ADC.Despite the high sampling rate of SAR ADC, for the control loop, each control cycle is sampled only once. The control period is equal to the sampling period. In this circuit board, the bandwidth of current sampling circuit is 500 KHz, which is much larger than that of the current control loop sampling frequency . Is this design unreasonable? Or is my previous statement incorrect?
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The second problem is about the front-stage operational amplifier circuit of SAR ADC.The SAR ADC input circuit requires High bandwidth and Low Slew Rate for operational amplifiers.Operational amplifier INA240 does not seem to meet the requirements.In real applications, do you need to add OPA320 in the back?
Thank you. I look forward to your reply.
