topic Re: iMX287 running on external oscillator? in i.MX Processors

iMX287 running on external oscillator?

albertguardiola — Thu, 18 Jun 2015 07:57:34 GMT

Hi all,

Is it possible to make the iMX work with external oscillator (not crystal)? We are discussing this alternative because integrated oscillators offer much better MTBF values than crystals. (20 times better!)

If not, can we run the iMX (including the RTC subcircuit) only with the internal oscillator?

Bets regards

Re: iMX287 running on external oscillator?

Yuri — Thu, 18 Jun 2015 09:14:49 GMT

I am afraid, we have no any specifications for using external clock sources,

except crystals, with i.MX28. The only recommendations are to use 24MHz, 30ppm

Crystal, and 32kHz, 20ppm Crystal.

More details for 24Mhz :

+/- 30ppm ;

max ESR: ~50ohm ;

Load capacitor : 10pf-15pf ;

Shunt capacitor : 5pf-7pf.

Sorry, an external oscillator option has never been tested with i.MX28.

Theoretically, it seems to be possible to apply an external 24MHz clock signal

to XTALI and leave XTALO open, however, the amplitude of an external clock

signal must not exceed VDDXTAL, that is typically around 1.0V.

The internal oscillator may be used in low power mode. By default it is disabled.

Have a great day,
Yuri

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Re: iMX287 running on external oscillator?

albertguardiola — Thu, 18 Jun 2015 09:22:13 GMT

Thanks indeed, Yuri,

How about running the whole IMX on internal oscillator? Is there any limitation in functionality?

I cannot find literature on the internal oscillator in the datasheets: could you provide quality specs on it?

Best regards

Re: iMX287 running on external oscillator?

Yuri — Thu, 18 Jun 2015 09:31:55 GMT

The internal oscillator may be used in low power mode. By default it is disabled.

Regards,

Yuri.

Re: iMX287 running on external oscillator?

albertguardiola — Thu, 18 Jun 2015 12:49:02 GMT

Thanks for the info, Yuri. Best regards.