STM32: Finding the right cheap chip

[hitech95]

Hi,
I have to find the right chip for my needs,
is there an online tool that have a good comparison of the chips.

My needs are:
- QFN48 or QFP48
- MCO with LSE clock source
- VBAT
- 2xI2C interfaces
- Cheap and in stock

The chip will simply manage the power state of a CM4 board and will emulate the RTC. The MCO is used to clock external CHIPs that require a 32.762Khz. (Unfortunatly the RPI4 does not have a built in RTC.
Ive started to look datasheet by datasheet but this is taking ages, for now I've only found the stm32f072c8 or the stm32f071c8 but they seems to be out of stock everywere.

STM32F030CC and STM32F070CBT6 would have been perfect but they lack the VBAT power input.

Also a chip with less ram and rom would be OK. At the end my IC is a simple I2C slave for the RTC and a state machine for power state (ON or OFF)

Any idea is welcome!
Regards,
Nicolò

[lucazader]

Most ST chips are out of stock everywhere right now. But its not an ST specific issue, it more an industry wide issue right now.

So i wouldn't worry tooo much about stock levels, especially if you are more at the beginning of your projects development.

I would take a look at some of the newer G0 Parts, they only require single power and ground supplies (and most have vbat).
They are also the newer chips using the newer production process so are a bit lower power. And quite often can be had for the same or cheaper prices than their F0 predecessors.
Something like the STM32G030C8 looks like it can do all that you need, but as with everything else they are out of stock.

[FlyingDutch]

Hello,

just download "STM32CubeMX" software and install it (it is free). Then there is search engine and you will be able to find MCU by using many criteria.

For such needs as you has given the STM32G0 series will fit (and MCUs from this series are in stock at some vendors).

Best Regards

[agehall]

I think the critical question is "in stock". All smaller MCUs are pretty much gone now IME.

[fchk]

I'd use a real rtc (MCP79410 for example, Linux support already there, VBAT pin there) and a separate push btn controller chip like LTC295x. No software development at all, just works.

See:
https://www.digikey.de/de/ptm/l/linear-technology/power-ltc2950---push-button-onoff-controller/tutorial

fchk

[NorthGuy]

Impossible. After re-stocking, what was cheap before shortages may not be cheap any more, or may disappear permanently.

[hitech95]

Most ST chips are out of stock everywhere right now. But its not an ST specific issue, it more an industry wide issue right now.

Something like the STM32G030C8 looks like it can do all that you need, but as with everything else they are out of stock.

That chip might be the perfect one! I'll have to see if Platformio is compatible with it.
The STM32G030C6 also seems to be another cheaper solution...  I will not need a lot of flash (i hope)
My device is mostly an I2C slave with memory mapping of some internal registers and a state machine

Yea I know it is a big issue. all my boards are on hold due to this. I'm designing my own AV-Receiver. DSPs, Amplifier chips, MCUs, all gone!
I've also had to redesign twice the DC DC section due to lack of ICs.

I'd use a real rtc (MCP79410 for example, Linux support already there, VBAT pin there) and a separate push btn controller chip like LTC295x. No software development at all, just works.

See:
https://www.digikey.de/de/ptm/l/linear-technology/power-ltc2950---push-button-onoff-controller/tutorial

fchk

the power management is not that simple. I have a whole power sequence and power states. the RPI CM4 is only part of the system.

Impossible. After re-stocking, what was cheap before shortages may not be cheap any more, or may disappear permanently.

I think the critical question is "in stock". All smaller MCUs are pretty much gone now IME.

I know, this is a big question mark for me. All my boards were designed to be assebled by JLCPCB but now all parts are going out of stock.
At least right now i have a STM32F4 Nucleo dev kit that was taking dust and I'me starting to develop the FW...

Also my CM4 is still in a backorder... so I cannot even start the development over there...

At this point I think that the hardware design is mostly on hold. We will see what will happend!
This wafer shortage is starting to be a huge issue even for DIYers that are bored during lockdown.