Help identify chip, probably power supply

[Sebastian]

Hi everyone,

I am working on a controller board for an oven, and I need to find a datasheet for a chip that I suspect to be bad, or at least I want to find out more about it. It should be part of a power supply, I am pretty sure it is a switched mode power supply chip, but so far I couldn't find anything with the code on the chip. The one with 5FN6 998.


Please help me if you know this chip

[fzabkar]

I suspect that the manufacturer is Monolithic Power.

Edit:

https://www.aliexpress.com/item/32978128032.html  (photo of MP2452)

MP2452, Monolithic Power, Step-Down Converter, 1A, 36V, 1MHz, 3.3V - 36V in, marking 5F, QFN8:
https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/MP2452/document_id/255/

[Sebastian]

Wow that was quick, thank you. I'll check if that makes sense with the other components.

[Sebastian]

Little update, your identification was right, thanks again for that. But it turned out to be the MCU that was bad. Fortunately I know someone with exactly the same model oven and I was able to get the firmware from it. What's interesting though, is that the power supply is set to around 5.5V, which is the maximum operating voltage of the MCU for 5V. The absolute maximum rating is 5.8V. I couldn't find any reason to do that instead of just setting it to the nominal 5V. Maybe for planned obsolescence?! When I replace the MCU I am going to replace the resistors to set the power supply to 5V.

For anyone facing the same problem with their Siemens HB676GBS1/99 oven, I hope you find this post. I'll put a couple of keywords in so hopefully the search engine spits it out if you are searching for: Siemens oven HB676GBS1/99 firmware repair control board 11052160 11038199 MCU microcontroller software NXP MKE14Z256VLH7 programming

If you need the firmware you can contact me at sebastian.salmhofer@custom-tek.com, I will send it to you and also give you the pinout of the connector on the board. I just used a FRDM-KL46Z development board that I had lying around as a programmer with USBDM. https://usbdm.sourceforge.io/USBDM_V4.12/Freedom/html/freedom_setup.html#FreedomFirmwareInstallation. You can get programmers for around 15 USD if you don't have one. Absolutely makes sense to fix it if you can, Siemens wants over 200 Euros for that damn board.

I'll give you another little update if it actually worked, I have to wait for the Chip now which will take like 2 weeks to get it to Paraguay.

[Sebastian]

It actually worked!
I got the chip, soldered it in and flashed the firmware and the oven works again.
But my planned obsolescence theory turned out to be wrong. I changed the resistors so the power supply produces 5V instead of 5.5V, but then the oven gave me an error code that the temperature sensor is bad. So something apparently needs the higher voltage. So I changed it back and it works again. Probably still not the best for the MCU in case of voltage spikes, but there's nothing simple I can do about it. At least I have a spare MCU now because I ordered two and the firmware in case it happens again.

[fzabkar]

Perhaps you could upload the firmware here?

[Sebastian]

I thought you couldn't upload files, but I found it. Just didn't see it before. So there you go, if anyone needs it.