MCXN947 LDO_Core Overvoltage

[Vasilis_Skr]

Hello NXP Community,

We are developing an IOT Module that is using the MCXN947VKLT (100 pin HQFP) μCU.

We made a production run of 100 PCBs and 5 out of them show a strange behavior: Their core voltage (VDD_CORE) ranges between 2V and 2.1V instead of having a maximum of 1.2V that is specified in the datasheet.

I removed the inductor LX and checked the core voltage and it is still 2V, which points me to the direction of the internal CORE_LDO circuit.

Is my assumption correct? 

How should we proceed?

Thank you in advance and I am looking forward to hearing back from you!

[carlos_o]

Hi @Vasilis_Skr 

Thank you for your post.

Thank you for sharing the information. Based on the details provided so far, I am unable to reach a conclusive assessment. Additional data or clarification is required to properly analyze the issue.

Please review the solder of the defective PCBs to ensure there is not a connection failure. 

Could you please share your schematic to review the LDO connection? 

If you want a private channel, please open a support ticket.

You could review how to use the ticket system in the following video Tutorial for NXP Support Case Portal | NXP Semiconductors

[Vasilis_Skr]

Hey Carlos,

Thank you for your quick reply.

Here you can find our connections to the μCU regarding power.

I do not expect something to be wrong as this is a rare occurrence we got in 3 out of 125 PCB's that we have produced, but it is still worrying me.

Regarding the soldering of the pins, I have checked the PCB's under a microscope and everything seems fine. I have also asked our PCBA partner to check the GND pad of the μCU with X-Rays to verify the soldering of that pin as well.

Let me know if you have any other insights.

Thanks in advance!

[Vasilis_Skr]

Hey Carlos,

Our PCBA partner removed the μCU and took these pictures:

The Pad on the PCB and the component was properly wetted and soldered. However, there are some weird orange markings on the pad of the component when you take a close look.

Would you have an idea on what they could be? Can it be solder and flux that was not properly heated up? 

After resoldering the μCU manually, the issue was fixed. 

Would it be possible for you to provide me with the soldering profile of the μCU, because if it is a soldering problem, our PCBA partner may have to adjust the reflow procedure. I tried to find more information in the datasheets, but I could not find anything. Could you provide me with such a document?

Thank you in advance!

Best Regards,

Vasilis