Is it possible co leave Vref+ pin unpowered in Standby ?

tomasz23 · ‎2008-01-05

Posted on January 05, 2008 at 16:58

tomasz23 · ‎2011-05-17

Posted on May 17, 2011 at 12:20

Hello

I'm going to use STM32 Standby mode (Vdd & Vdda = 3V from battery)

but ADC will be working only in Run mode, when main supply (3.3V) will be operating and then Vref+ pin will be powered through LM431C reference

at the level of 2,5V. But when main supply will be switched off then conseqently Vref+ will be left unpowered ... I cannot supply Vref+ directly from

Vdda because of 2,5V reference requirement. I do not want to do any ADC conwersions when main supply is not working.

The question is:

Is it a safe / possible solution ? Can be Vref+ left unpowered (but connected to LM431C) in Standby ?

I'm afraid of possible current leaks from Vdd/Vdda to Vref+ in this situation.

asterix · ‎2011-05-17

Posted on May 17, 2011 at 12:20

Hi,

According to AN2629 : STM32F101xx and STM32F103xx low-power modes and the Reference Manual, It seems that Vref is only available in 100 pins package . In smaller packages, this Power supply ref is bounded internally to VDDA. So, in my understanding you should left it not powered in standby ( where all blocks are Powered off except the VBAT domain)without risks of leakage current, I assume that ST has a good analog design in their rails powers and I/O ring in Low power.

You can try it at your end and inform me if you observe additional leaks.

Magigimix 😉