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?