st32F I/O protection circuit

[td]

Posted on August 25, 2016 at 07:42

Hello everyone, i have a st32F407 and i was thinking if it is working on 3.3V and almost all its pins are 5V tolarant what kind of protection circuit it has for

overvoltage

and

ESD

. I saw on the reference manual in 8.3/figure 25 the structure of a five-volt tolerant I/O port bit, it has EXTERNAL clipping diodes at 5V.So my question is do you have to put external protection circuit ? Is it already protected inside the pin?

[John F.]

Posted on August 25, 2016 at 09:01

You misunderstood the diagram (In RM0090 Version 12). The protection is internal as are the supplies VDD and VDD_FT. The dotted lines are around the ''Input Driver'' and ''Output Driver''

So the ''FT'' port pin needs no additional components to operate with 5V drive signals to its input. Note, you still only get 3.3V outputs and you may need to add ESD protection if the pin is exposed to the ''outside world''.

[td]

Posted on August 25, 2016 at 12:39

so i guess the microntroller has an internal converter to generate V_FT(5V) from the 3.3 V that is provided

[Tesla DeLorean]

Posted on August 25, 2016 at 16:41

so i guess the microcontroller has an internal converter to generate V_FT(5V) from the 3.3 V that is provided

No, I think it means that the current back-feeds onto a different IO power ring, and doesn't elevate the 3V3 ring. It is definitely not generating 5V anywhere.If you need industrial level protection the silicon here isn't going to provide that, you'll need to put it externally.