Is it normal for CMOS mcu’s to run slightly warm?

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Is it normal for CMOS mcu’s to run slightly warm?

Contributor IV

I have several products in production using HCS08 and HCS12 devices.
The HCS chips are all running slightly warm.

I am worried I might have misconfigured I/O lines causing unwanted power consumption.
Perhaps unused I/O that is not available externally due to my use of smaller packages.

As far as I can tell this is not the case,
but I am uncomfortable with lukewarm CMOS devices.

Am I overthinking this?
Is this perhaps normal when running these devices at full speed?


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NXP TechSupport
NXP TechSupport

Hello Anders,

You didn't mention the MCUs, but anyway, the reference manuals should specify

  • Power Dissipation and Thermal Characteristics
  • Thermal Package Characteristics

Regarding un-bonded pins, they should be driven either to VDD or VSS as output, they should not be floating.




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