Other Parts Discussed in Thread: INA301
Hello everyone, I am currently using the INA240 (A2 so gain is 50V/V) to measure the current for a buck converter and I am struggling to get rid of the noise on the output of the INA240, which is about 10mVpp. It is not much but still having an effect on the performance of the converter (for output voltage ripple purposes). I have checked my setup for noise in the reference and supply of the INA240 but everything is fine (less than 3mVpp of noise).
My first question is: given that my switching frequency (hence sensed current frequency) is 250kHz, is the INA240 a good choice of current amplifier for my application ? I understand that the bandwidth of the INA240 is 400kHz so I am not getting a nice triangular waveform on the output of the amplifier, but in my case I am doing an average current control for the inner current loop of my control scheme. So by using the INA240 I am hoping to use it as my current amplifier as well as filtering my switching frequency, but I didn't really find any information in the datasheet as to what could be the impacts of applying a signal which frequency is close to the bandwith of the current amplifier. Is there a risk that the current amplifier is no longer stable hence the noise on the output ?
My second question is : is this amount of noise expected on the output of the INA240 ? I have read on this topic that similar noise had been experienced on the output of the INA240 and the answer could come from figure 7-18 in the datasheet. But why use 400kHz (bandwidth) in the 40nV/sqrt(Hz) formula ?
I have also tried to filter the input of the INA240, which works until some point because it reduces too much my stability margins so I tuned the filter on the input to get my final result of 10mVpp and necessary margins.
For this type of application (current measure in switching converters), do you recommend to use a different current amplifier, preferably one with less noise on its output ?
Thank you in advance and best regards.
