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VREF+ in STM32L1xx

Question asked by Ali Movahedi on May 18, 2018
Latest reply on May 19, 2018 by T J

Dear all,


I have question regarding the VREF+ please.  My understanding is that in STM32L we only have one VREFINT which is about 1.2xx Volts and this is not a reference Voltage to the ADC.  It is directly connected to the ADC_IN17 input. . It enables accurate monitoring of the VDD value (when no external voltage, VREF+, is available for ADC).


I am not sure what does this statement "when no external voltage, VREF+, is available for ADC" mean?  Does this mean the VREF+ pin should be floating?


If for other channels I need a reference Voltage let's say some where between 1.8 and 2.4V we have to supply it externally?  Basically is there any reference Voltage  (Not VREFINT) available internally?


My understanding is VREF+ should always be less than or equal VDDA.  I believe we can select internally VREF+ to VDDA but I am not sure how.Can we select the ADC_IN17  channel reference Voltage VDDA internally and other channel other VREF?