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MPC5643L IRC Accuracy

Question asked by martinp on Jul 25, 2017
Latest reply on Jul 27, 2017 by martinp

Hello,

 

During some recent testing of the CMU I discovered that the high/low limits that I had set for the system clock were not working as expected. Some further experiments have concluded that the problem was that the IRC (measured on several devices using several methods - CLKOUT pin, CMU frequency measurement and reverse calculating IRC from CMU using the tightest high/low limits that didn't cause a reset) was somewhere between 13-14Mhz instead of the expected 16MHz.

 

I'm aware that the internal oscillators are not necessarily known for their accuracy, but various datasheets refer to the worst case accuracy range for this device to be +/-6%, whereas I'm seeing between 12-18% on a number of relatively new devices at room temperature.

 

Is there an explanation for this behaviour?

 

Best Regards,

Martin

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