Specifications for IO protection diodes

[rwa]

Posted on March 09, 2017 at 09:25

Hello

Does anybody know any specifications for the protection diodes included for each IO pin? What is the maximum current that can flow through? what is the maximum power dissipation? I am trying to decide whether I need to add external Schottkeys or not.

Thanks in advance.

#ios #stm32f0 #protection

[Nesrine M_O]

Posted on March 09, 2017 at 09:48

Hi

Vanoverschelde.B.003

Please refer toI/O port characteristics section in your related datasheet

-Nesrine-

[AvaTar]

Posted on March 09, 2017 at 09:54

IMHO you will have to conclude this from the spec. of the GPIOs, i.e. from the datasheet.

I sincerely doubt that ST will release specifications of individual elements on their silicon, like this diodes.

Additionally, all GPIOs, including this protection diodes, are on the same silicon, and will affect each other. As an example, you can 'supply' the MCU by injecting a voltage on an unpowered GPIO alone. (Just to be clear, you can do this with most/all competitor devices on the market ...)

I would prefer external protection circuitry - my 2cents.

[S.Ma]

Posted on March 09, 2017 at 09:59

No an expert on this. From my general understanding the structure of the input question relates more to the guaranteed lifespan of a product. This relates to the Electrical Characteristics Info of any chonse semiconductor IC, which guarantees a lifespan. (quality/reliability)

For example, some people may say that using a device in absolute maximum rating condition may shrink its 'guaranteed' lifespan to ~1000+ hours...

[waclawek.jan]

Posted on March 09, 2017 at 10:19

Please refer to I/O port characteristics section in your related datasheet

+1

The STM32 datasheets provide quite a bit of related information; the keyword to search for is 'inject' (as in 'injected' or 'injection').

JW

[T J]

Posted on March 09, 2017 at 12:39

its not worth worrying, just add the parts.

For the younger engineers;

The SOT23 common anode schottky diode pair will do the job,

https://www.digikey.com.au/product-detail/en/nexperia-usa-inc/BAT721A,215/1727-3572-2-ND/1127171

 

these diodes are a little expensive, but have a very low turn on voltage.. 0.3V

one on each pin that is exposed externally, is a safer way to be sure of a usable lifetime.

The alternative is the necessary ESD protection diodes usually used on the USB ports like:

https://www.digikey.com.au/product-detail/en/nexperia-usa-inc/PUSB2X4YH/1727-1987-2-ND/4843356

 

these are a similar price but you can protect two pins.

These are purpose built for your question.  good for a 4.5Amp pulse

be sure to check the graphs to see the 'forward turn on voltage',

if its too high then you are wasting your time and money.

[AvaTar]

Posted on March 09, 2017 at 12:53

Depends on the 'dangers' the boards needs to be protected against, i.e. impedances, energies and frequencies.

[David E]

Posted on September 20, 2017 at 00:01

Could ST please comment on this and at least share the number of diodes in the structure for both high side and low side ESD protection. I'm guessing that for most digital IO pins there is the equivalent of 6 series diodes between +3.3v and the GPIO pin.