Review about circuits using STM32F401VE

[Inho Jeon]

Dear ST & all,

I attach a file. That is a part of MCU of audio device.

Please, Review & Comment my circuirts.

Thank you

Best Regards,

Inho Jeon

[Danish1]

What sort of comments do you want?

As I don't know what "audio device" is supposed to do or what it interfaces with, I can't give very useful comments or even spot what might be glaring errors. I'm only choosing to reply because like many volunteers on this board I try to be helpful.

There are lots of 22 ohm resistors. Is there an engineering reason for this value, or even their presence in the circuit? (For example, that might be standard practice in your company, but if the trace is only going to an adjacent chip on the same pcb, why)? Would you have another series resistor elsewhere for each LED?

You seem to have 3 separate I2C buses. Why?

What voltage range should it operate from? What total current, with reference to power dissipation in any linear regulators? Do you have heat-sinking?

I personally would leave space for a 32k crystal unless space really prohibits it.

20pF sounds wrong for the load for your 8 MHz crystal. Have you checked your crystal against the ST application note for crystals?

Hope this helps,

Danish

[Piranha]

I would definitely add NRST to SWD connector for "connect under reset" purposes. SWO can also be useful, but not necessarily, especially if there is UART already.

The need for a LSE crystal is specific to application. It the application doesn't need RTC in low power modes, then there is no use of LSE crystal.

Typically 22-33 ohm series resistors are used on high-speed (tens of MHz and higher) output (and bi-directional) lines in series with chip pin's output pin impedance to match 50 ohm board/connection target impedance. LEDs and buttons doesn't need those, but they must have their own proper resistors. Actually on STM32 side those 22-33 ohm series resistors are not really needed even on high-speed lines, because the same can be achieved by enabling I/O compensation cell.

The only another added value of series resistors is the fact that they limit the current amount in case lines are shorted to GND, VDD or other lines, which can be useful safety measure on external connections. In that case consider 150+ ohm values to keep the current under the absolute maximum 25 mA.