topic KW45 MCU heating up in Wireless MCU

KW45 MCU heating up

Sadeed — Wed, 11 Jun 2025 06:22:17 GMT

We have assembled Two KW45 boards, During Board bringup we are facing few issues, Which are as follows:

As per the attached schematics:

-> The KW45 ic started heating up when board was powered On and the board was drawing 0.45 Amps at 12Volts. After some Debugging activity, I have found that when R15 is removed then its drawing only 10 mA. The heating issue happens when I mount that resistor.
When R15 is removed, I have measured 1.8V at pin 21 on KW45 ic.

-> The voltage on MCU Reset pin is 2.299V; 3.3V rail has less than 100mV ripple. I have observed some kind of oscillation on that pin.

-> We have referred to page 749 found in KW45 Reference manual.

-> we are using KW45B41Z53AFTBR

-> On 5V section, I am getting 5.4V, as we have adjusted it for other requirements and in 3.3V section, it is 3.3V.

Could you please Verify the Schematics for any kind of improvement?

______
Thanks & Regards

Sadeed

Re: KW45 MCU heating up

luis_maravilla — Thu, 12 Jun 2025 20:39:47 GMT

Hello

I would recommend checking this community post as it describes Hardware design recommendations for the connections referring to DCDC configuration in KW45.

The best way to build a PCB first time right with KW45 (Automotive) or K32W1/MCXW71 (IoT/Industrial) - NXP Community

Also, Could you help us confirm what DCDC mode are you trying to build?

Please refer to page 44 for Reset configuration and Page 8 for DCDC Modes in this File "KW45 Hardware Design Recommendations Public" located in the same Community Post.

Best Regards

Luis

Re: KW45 MCU heating up

Sadeed — Mon, 16 Jun 2025 07:56:23 GMT

We have found that C41 and C35 were mistakenly added. After removing these two capacitors, the issue has been resolved.

Please find the relevant schematic section attached below for your reference.