Inquiry Regarding MCU with Specific Features

[pumarada]

Dear STMicroelectronics Support Team,

I hope this message finds you well. I am interested in identifying a microcontroller that meets certain specifications for my project. I would appreciate your assistance in identifying the most suitable MCU.

MCU Requirements:

1. Low-pin package type: SO (Small Outline), SOIC (Small Outline Integrated Circuit), or TSSOP (Thin Shrink Small Outline Package).
2. Should be I2C (Inter-Integrated Circuit) compatible.
3. Must have a built-in Real-Time Clock (RTC) module.
4. Should include a VBAT pin for battery backup.

If you could provide information about any MCU that meets these requirements or suggest where I can find such information on your website, I would be very grateful.

Thank you very much for your time and assistance.

Sincerely,

[Tesla DeLorean]

Most of the STM32 parts have these features. Some of the L Series lack the VBAT as they are expected to be battery powered, and just go into STANDBY using minimal power and running their RTC

What does you code foot-print and RAM usage look like? What MCU do you need? Clocking at what speeds?

The physically smaller parts have smaller die, and less FLASH and RAM. The QFN-28 and QFN-20 packages can be pretty small and still manageable

Perhaps find a local sales rep or distributor. An FAE might be able to help unpack you actual requirements and use case.

[pumarada]

I am creating a light-based alarm clock that simply turns on an RGB LED according to the wake-up time.

The code is very simple:

• A wakeup interrupt is configured, and the system is put to sleep.
• When the set time arrives, one of the three RGB colors is activated based on the minute range of the hour: 0-15, 15-40, and 40-59. If the set time is exceeded, a color blinks according to the delay in hours to the wake-up time. Blue, green, red represent 1, 2, 3 hours, respectively, following the same pattern for minutes. This way, we can know the time without looking at the clock, simply by the blinking of an LED. This doesn't disturb anyone who may be sharing the bed. In short, very little code. Only an I2C is programmed to control the LED, and the microcontroller goes to sleep until the next color change and blink event.

I'm not brave enough to solder the QFN yet.

[TDK · Accepted solution]

STM32CubeMX has a part selection that can be helpful here.

You're probably out of luck here with the VBAT pin requirement. All chips have RTC/I2C.

No SO-8 chips have a VBAT pin. The STM32G0 series has that pin, but only in the LQFP48 packet. My guess is other series are similar.

[pumarada]

Thank you,

It's a pity that the VBAT is not implemented in all chips that integrate RTC.

Very kind, thank you very much.

[TDK]

Probably more people want a GPIO pin than VBAT. That would have taken the IO count from 6 down to 5.

Soldering an LQFP is doable. Not as easy as SO-8 but it can be done with hobby-quality tools if you have some patience, flux, and a solder wick.

[pumarada]

Hello and thank you, I found this:

https://www.lcsc.com/product-detail/Microcontroller-Units-MCUs-MPUs-SOCs_STMicroelectronics-STM32G030C8T6_C529329.html

You have many pins that will be unused, but it's the smallest one I found with VBAT.

Thanks again and greetings.

[TDK]

The STM32G030K6T6 (LQFP32) does not have a separate VBAT pin. Only LQFP48 chips from that series have one.

[pumarada]

Yes, I realized after posting, it's already corrected.

Thank you very much anyway, you are very kind.

[pumarada]

Currently, I am using this one, but it costs 5€, and the STM32, besides saving me the external RTC, doesn't even reach 1€, and that is magnificent!!