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LPC4367JET256 ADC0_0 offset

Question asked by Thomas Stegmeijer on Jul 3, 2017
Latest reply on Jul 14, 2017 by Carlos_Mendoza

Hi,

 

We are using the LPC4367JET256 in a new design, we are using the dedicated ADC pins. 

ADC0_1 to ADC0_7 work perfectly but ADC0_0 has a offset. 

The ADC are driven by a op-amp followed with a resistor divider ( 56K and 100K) and a 2.7nF capacitor on the ADC pins. The ADC sample fequency is low. 

 

When the output of the op-amp is 0V the ADC0_0 measures ~0.3V, when measuring the voltage on the ADC pin it is 0.3V. 

So there is a 0.3V voltage drop across the series resistor, but current is sourced by the LPC43. 

ADC0_0 is the only DAC pin so we thought this may be enabled, but disabling the DAC does not work either. 

 

Does anyone have an idea why the LPC4367 sources on the dedicated ADC0_0/1_0 pin?

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