Apply external +3.3V to Vref+ pin while Selected Vrefbuf as 2.5V on Code Configurator

[krn]

Hi, I am using STM32L4R9ZIJ6 with power pin connections as following image.

On the same design where VREF+ pin is connected to P3V3, if I configure Vrefbuffer for ADC measurements & use Vrefbuf as 2.5V, I observe that current draw from P3V3 goes from 10mA to 20mA.

I understand that it is not correct to apply external voltage at Vref+ pin when it is configured as Vrefbuffer = 2.5V. I will avoid it on final production boards. Please can you explain why this increased current draw is observed.

[TDK]

The voltage reference buffer is trying to sink current from that line to get the pin to the 2.5 V target level.

 

If VREF+ is provided externally, you cannot use VREFBUF.