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KL03 with external MHz clock

Question asked by Martin Krause on Mar 2, 2016
Latest reply on Mar 3, 2016 by Stanislav Arendarik

Hi, we are running a custom board with KL03Z32 mcu. The mcu is running at 8 MHz from LIRC. We use the LPUART to communicate to another board. The LPUART is clocked from LIRC. Unfortunately the LIRC only has an accuracy of +/- 3%. This is not enough to meet the baud rate requirements. Using the more precise 48 MHz HIRC (with +/- 1% accuracy) is not an option, because the power consumption then will be too high (according to the data sheet). So our idea was to use an external crystal oscillator with a high accuracy (+/- 20 ppm). But if I understand the data sheet/user manual, then the allowed range for the external clock is 32 kHz ... 40 kHz and the mcu has no internall PLL to increase this freqency internally. So it seems not to be possible tu run the CPU with 8 MHz with an external (high accuracy) clock. Is this correct? Is there any chance to achieve a baud rate accuracy better than +/- 3% when running from LIRC?

 

Best regards,

Martin

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