Help me selecting the best microcontroller for my app

[XR.1]

Hi!

I'm looking for a uC that:

• It is Cortex-M0 or M0+,
• It isn't a Low Power device (L series) (no need to include Shottky diodes, and my app will be power hungry)
• It has internal EEPROM,
• 32 <= LQFP <= 64,
• It has 20+ free pins,
• and the most important thing: it must have a VBat pin. A CR2032 coin cell will keep the time and calendar.

 

You might wonder why I didn't use the STM32 mcu product selector chip selector. Of course I did; however, as far as I saw, a column that indicates whether the part has exposed the VBat pin or not doesn't exist.

 

There are myriad of parts to choose from, but it's imposible to review each one. Even worst (or better?), parts with less than 36 pins doesn't exposed the VBat pin.

 

For example, STM32G070 has the VBat pin exposed (LQFP >= 48), but it doesn't have eeprom.

 

In case such a thing doesn't exist, then I'm open to emulate the EEPROM with the mcu Flash, and the most dynamic data will be saved in the battery backedup RTC RAM. 

 

Did I overlook something in the product selector, or there exist another way to verify, in a systematic way, whether a number part has (and it's exposed) the VBat pin?

 

Thank you in advanced!

 

[mƎALLEm]

Hello,

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@XR.1 wrote:

Did I overlook something in the product selector, or there exist another way to verify, in a systematic way, whether a number part has (and it's exposed) the VBat pin?

 

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There is no systematic way to catch if VBAT is available or not.

You need to do a first filter using ST MCU FINDER tool then check if VBAT pin is available in the list of the package you get.

 

[Andrew Neil]

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@mƎALLEm wrote:

You need to do a first filter using ST MCU FINDER tool then check if VBAT pin is available in the list of the package you get.

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would it be identified in the .svd and/or .ibis files?

They're text files, so a (simple?) text search (eg, grep) should find it if it's there?

[mƎALLEm]

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@Andrew Neil wrote:

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would it be identified in the .svd and/or .ibis files?

They're text files, so a (simple?) text search (eg, grep) should find it if it's there?

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In that case why going to grep in these files? he can find the information in the pinout table in the datasheet or in CubeMx.

[Tesla DeLorean]

The other thing is that parts without a VBAT are often expected to be battery powered, inherently use less power and turn themselves off

[XR.1]

My device will be constantly powered by external 12VDC, and it will be unplugged from time to time, and the time/calendar must be kept when that happens.

Sharing the VCC pins with the 3V3 regulator and the coin cell must be carefully designed, not only in hardware, but in hardaware as well. And that's why I want to avoid such scenario and look for a part with the VBat pin exposed.

I've seen some Shottky diodes arrangements, including the AN's from ST, but I'd prefer emulate EEPROM before messing around with diodes.

[EvO]

I think you can stop searching: EE & 32 <= LQFP <= 64 returns only L devices.

I did a similar search a while ago and ended up using external EE, which simplified the search a lot!

[Andrew Neil]

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@XR.1 wrote:

• It isn't a Low Power device (L series) (no need to include Shottky diodes, and my app will be power hungry)

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That's not a reason to exclude all those parts, surely?

If they meet all your other criteria ...

[XR.1]

Yes, it is because I'd need to use some weird mix of hardware/software Shottky diodes, channel P FETs, and also sensing the principal VCC pin and generate interrupts on the Brown-out chip feature. A complete mess!

AN4718 explains better what I'm want to avoid.