Automotive Grade Power Supply Design for RPI5

[mbt28]

Dear Hackers, Makers,

I am using lin-transceiver to connect Infotainment-Bus of my old car. Lin IC wakes up whenever bus line has a falling edge and provides 3.3V 50ma from VCC pin then this pin connected power supply enable pin. When lin transceiver disabled it cuts all power. Currently I am using a stepdown module that I purchased from Aliexpress which has an EN pin but this board only provides maximum 3A.

What kind of power supply IC are you using in your setup? Would you suggest an automotive grade design which can handle 5V 6A?

Thanks

[kiler129]

Check https://mikrotik.com/product/apa_1

These are very reliable, cost $30 from an official distributor, and have a good design.

[f-io]

Do you have an image showing the ICs used for the buck/boost converter(s)?
It is also limited to 3A @ 5V, which may be a bit too close to the edge for our needs, at least during transient spikes, or if you plan to use wired mode where you still need to add at least 800mA for charging.

[mbt28]

I cant see any information about voltage regulator used. I dont have enough information about how to design proper automotive power supply but I found this https://www.diodes.com/part/view/AP64502 buck converter. It is not expensive, and available as SO-8EP package. All new buck converters from TI comes with fancy packaging.

There is another person in BMW forums, he built a CM5 based LIVI board with LMR14030S 3A power supply. He reported it works fine and he doesn't have voltage drop. But when charging included I think it will have trouble keeping voltage level.

Also all the buck converter boards that I tried from Aliexpress which suppose to make 8A or 5A fails at some point and RPI5 shutdowns.

[f-io]

The Pi 5 actually needs 5.1V, not just 5V. The current ratings you see in most Aliexpress buck converter ads are absolute max values under ideal conditions, not what you can run continuously. You always have to read the controller datasheet and check the SOA (Safe Operating Area), because in passthrough mode there's almost no power loss, but once the buck has to actually switch under load you hit different limits, plus thermal degradation over time.