LPC1837 Clock Source Drift Error

[Anonymous]

Hello,

This is my first project with the LPC1837 board, and I'm working on a clock synchronization program. I was looking the datasheet and found out the IRC is used as the main clock source for the processor and the peripherals. My question is, why the IRC is used as the main clock source and not the crystal oscillator? The crystal oscillator has a smaller clock error than the IRC, would it not be better? I know that I can change the clock source for the core and peripherals, but I'm wondering why the IRC is the default and not the crystal oscillator.

Thanks for the help.

[Anonymous]

Thanks for both reply, I will probably set the crystal oscillator as my "main clock source". Is there any disadvantage in using the crystal oscillator instead of the IRC? Like Bernhard said, the crystall has higher accuracy, so I only see advantage of using it for clock synchronization purposes.

Thanks for your help

[jeremyzhou]

Hi Luiz Gonzaga Nunes Maia Neto,

It will increase the cost, sometime, it may increase the PCB size if you use the crystal oscillator.

Have a great day,
TIC

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[jeremyzhou]

Hi Luiz Gonzaga Nunes Maia Neto,

Thank you for your interest in NXP Semiconductor products and for the opportunity to serve you.
After a power-up, reset, or when waking up from deep-power down mode. In these situations, the boot code executes when the fault core clock BASE_M3_CLK is running at 96 MHz which is clocked from the 12 MHz IRC.
As Bernhard Fink mentioned, it's free for you to reconfigure the MCU's clock, of course, the crystal oscillator is also available to be the clock source of the 'main clock'.
Have a great day,
TIC

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[bernhardfink]

The IRC and the crystal oscillator are both valid sources for the "main clock" as well as for all other peripherals, sometimes (e.g. for USB 2.0 operation) the crystal is required because of the higher acuracy.

At any point in time you can select between the both sources (at least if you have a crystal connected), so it's fully up to you to design a crystal in or not.

Regards,

Bernhard.