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MK20FX512VLQ12 ADC1_SE11 problem

Question asked by Tejas Gawade Employee on Apr 12, 2017
Latest reply on Apr 20, 2017 by xiangjun.rong

I am facing ADC accuracy issue with MK20FX512VLQ12 device. This problem is specific to ADC1 SE11 and SE10 channels. Other channels on same adc are working fine. Tested and confirmed on multiple boards.

Output of opamp is connected to adc so  matching should not be issue.

- Processor expert generated code is used with 1.8uS conversion time, 12bit mode, high speed conversion enabled and normal mode. Expected ADC count is 345 where as i am getting 195-200 count.

- I don't expect issue with pcb as same opamp output gives expected count when connected to other adc channels.

- I have tried different sample time setting but same error.

- But when conversion time changed to 7uS or higher, adc works fine. also observed that connecting oscilloscope probe corrects adc count.


Will different port structure on mcu cause this issue?