WARNINGS on VOLTAGES and BOARD DESIGN

jlchoobs · ‎2012-07-22

Posted on July 22, 2012 at 12:21

I have been building my own Boards.

And have experience with an assortment of Micros.

WARNING #1 :

I have found that these STM Chips are Very SENSITIVE to Voltages.

I accidentally tied the USB 5V source to the VDD Bus thinking that it could also Power the Chip - accidentally for a few Seconds. Now the STM32 Chip and Board are USELESS.

Do NOT use ANY Voltage HIGHER than 3.5V on ANY Pin to the STM32 Micros -or the Chip becomes ABSOLUTELY USELESS. Flash Programs will Not Execute -and the Programmer will Not recognize the STM Chip anymore.

The other chips, atm for example, are not so Sensitive. And, I never encountered issues with brief stray Voltage Levels.

All I can say is Be Careful as can be.

And if you think that the STM is Not responding to the Programmer - then it is probably so - and a waste of time to try to resurrect the Chip.

What threw me off is that the Stm32 Micros can Not be Directly powered off of the USB Bus (as I would at first assume). You need to place a VReg (like 3.3V) between them.

Andrew Neil · ‎2012-07-24

Posted on July 24, 2012 at 21:21

''I don't know too many logic chips that the IO pin input voltages can be greatter than the chip's Vdd''

That's what they mean by, ''5V-tolerant''

''Which breaks your same rule from Spec''

The spec gives specific ratings for the 5V-tolerant pins

Andrew Neil · ‎2012-07-24

Posted on July 24, 2012 at 23:53

Would be interesting to see the corresponding specs for the Atmel part(s).