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CR2032 Battery connection to microcontroller for Internal RTC feature

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BoopathiS

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For STM32F4 controller Internal RTC, I'm connecting CR2032 battery directly to VBAT power pin with a 0.1uF decoupling capacitor.

Is this connection is correct ?


VBAT voltage range is 1.65 to 3.6V

Battery parameter:

Battery Voltage: 3V
Battery Technology: Lithium Manganese Dioxide
Battery Capacity: 240mAh

CR2032 Battery interconnection.png
 

Hi,

Yes, afaik this is correct.
Although not mentioned, I think it is always a good idea to place a ceramics capacitor to each supply pin.

Why are you in doubt?

Klaus
 

Thanks KlausST for immediate response.

My doubt is,

I'm directly connecting battery to controller, so it requires any protection circuit or not ? (like series diode with battery)
 

Hi,

Protection:
If you insert the battery carefully in the correct direction in an ESD protected area, then no need for extra effort.

* If you expect ESD, then you need to add ESD protection.
* If you install the battery the other way round then you need to install reverse voltage protection.

Klaus
 

Hi KlasuST,

Thanks for your input. I will checkout.
 

insert the battery carefully in the correct direction in an ESD protected area

Along with these observations, I would add one more: In choosing the coin holder, pay attention to those that allow Vbat making contact before the GND during battery insertion, as this may cause problems depending on the robusteness of the internal circuit of the uC in face to ESD and/or if proper care has not been taken at assembly time; prefer those whose battery negative surface always makes contact first to the holder terminal.
 

Hi andre,
Thanks....

Sure i will check battery holder as per your suggestion.
 

Why don't you review what's written about Vbat characteristics in the ST32F4xx reference manual? It says, a diode can be required under circumstances.
 

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