Adc Issue With Trigger Mode

[praveen_ext]

In S32 Design Studio, we are using two methods for ADC peripheral configuration. The first method uses the BCTU trigger for current sensing, while the remaining channels, such as temperature and voltage sensing, are triggered using the normal ADC chain method.

When the CTU mode is configured as a trigger mode and only the three current-sensing channels are configured with the BCTU trigger, there is no noticeable current spike. However, when I include the remaining temperature and voltage channels using the normal chain method along with the current-sensing channels, the current-sensing values are affected by spikes.

praveen_ext_0-1788357008084.png

There is a timing difference between the two methods: the BCTU conversion is triggered through an interrupt, while the normal ADC chain is called from a 5 ms task.

praveen_ext_1-1788357050345.pngpraveen_ext_2-1788357069814.pngpraveen_ext_3-1788357094947.png

Could you please explain why this difference is causing the current-sensing spike and suggest how we can reduce or eliminate it?

[Senlent]

Hi@praveen_ext

It seems my colleagues and I have dealt with the same issue you're experiencing before.

We've also conducted some tests following your software configuration, but we didn't encounter such a significant difference. We're unsure if you've taken any of our suggestions.

Therefore, I need you to provide your test project. I will reproduce the problem on our hardware platform. If the problem can be reproduced, we can quickly provide you with a conclusion about the cause.

[praveen_ext]

I have attached the test code for review. We are still observing spikes when running the BCTU trigger and the normal chain mode in trigger configuration simultaneously. Could you please help us, how we can eliminate these spikes? I have already attached the test results in my previous post

[Senlent]

Hi@praveen_ext

I recorded a video of the test using the project file you provided, without making any modifications.

I connected the sampling pins to VDD externally; the results below show that I did not encounter the spikes you described.

Senlent_0-1788492709905.png

I also noticed that the project file you provided does not seem to match the  pictures shown in your test images. If you are able to reproduce the issue using this project, you should check your sampling circuit design—specifically, whether the input impedance at the sampling pins is too high.