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LPC84X ADC Discontinuity

Question asked by Evan Buchanan on Sep 24, 2019
Latest reply on Nov 19, 2019 by 12345 67890

Has anyone else noticed a large discontinuity while using the LPC845 ADC near mid-value?  I am seeing a range of missing codes immediately below 2048 ticks. 

 

I can replicate this on my own boards along with the LPCXpresso845MAX dev board using minimally modified example code.  By changing the adc_basic example to use ADC2 and connecting a bench supply with 2K/22K resistor divider to Analog header A0, I can replicate the issue by dialing the supply voltage.  Here are the missing code ranges I observe on my three LPCXpresso845MAX boards:

   2034-2047

   2037-2047

   2041-2047

 

The problem exists independent of sample rate and is present at much lower input impedances as well.  This is rather annoying for my application since I have bidirectional current sensors which idle at half ADC value.

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