I'm useing MKL36,but the ADC channel affects  the TSI results。

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I'm useing MKL36,but the ADC channel affects  the TSI results。

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lilongjie
Contributor II

HI ALL

       Now I'm useing MKL36Z64VLH4 to develop something。 Hardware:ADC channels 2,4,6,TSI channels:12,13,14,15. When the ADC channel 6(PIN8) turns on,all of the TSI channels‘result will be higher,especially TSI 13(PIN43),even if I let the ADC6 unconnect ,but the result was same。Others ADC channels have no effect on TSI channels。The  green line is TSI13’s result。 Any help would be appreciated, thanks!13765_13765.pngresult.png

Original Attachment has been moved to: test1.rar

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pavel_sadek
NXP Employee
NXP Employee

Hi Li,

the TSI module is sensitive - and has to be to measure small changes of capacitance seen on the electrode. The ADC creates a noise when operating and can influence the result.

If application allows that, I would suggest you to synchronize the operation of ADC and TSI not to operate at the same time, which means disabling the ADC when TSI measurement is done ( I do not expect you will need to disable TSI).

Pavel

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vicentegomez
NXP TechSupport
NXP TechSupport

Hi Li

Do you have a serial resistor on the Pin 43? Normally we recommend to add a serial resistor on the TSI pin (less than 10 K)

Please try adding this resistor and let me know the results
Have a great day,
Vicente

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lilongjie
Contributor II

Thanks for  your reply

I try to let the pin43 unconnect。But the result was same。Someone tell me is the ADC‘s metal leads are too close to the TSI in the interior of the chip,is that really?

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vicentegomez
NXP TechSupport
NXP TechSupport

Hi Li

Unfortunately I do not know how is internally the device, but I used the different TSI channels works using the ADC on the KL, yes when you use the ADC, this signal induce noise on the system, because of this I recommend you that you add resistor on that pin, also the Layout can help to improve the signals on the electrode. Please check the application note AN3863

Please add the resistor and tell me the results
Have a great day,
Vicente

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Note: If this post answers your question, please click the Correct Answer button. Thank you!
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