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External reference voltage for STML4

Question asked by jeffrey zhang on Jun 11, 2018

Hi,

 

I have very weird issue with external voltage reference with STM32L4xx.

I have a board which is using external voltage reference for STM32L476. I apply 3.3V to both VDDA and VREF+. The VDD is also powered with 3.3V. when I enable the ADC of the STM32, It draws >100mA on VREF+ pin! As part of troubleshooting, when I disconnect 3.3V from VREF+, or enable the internal voltage reference, it stops to draw current. 

So what is going on with external voltage reference?

 

100mA is significant compare to micro-controller itself power consumption. I checked the datasheet and the manual. the only the limitation I've seen is, the VREF+ should be less or equal to VDDA. 

 

Has anyone used external voltage reference with STM32L4 family?

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