Jitter and Duty spec for RTC_XTALI in i.MX7D

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Jitter and Duty spec for RTC_XTALI in i.MX7D

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ko-hey
Senior Contributor II

Hi all

I have a question about RTC_XTALI spec.

I checked following section to confirm spec for RTC_XTALI but there are no definition about jitter and duty.

Is there any spec for jitter and duty for RTC_XTAL ?

If there are no spec, could you tell me how to select the 32KHz clock ?

Section 4.1.4 External clock sources of datasheet

http://www.nxp.com/assets/documents/data/en/data-sheets/IMX7DCEC.pdf 

Section 4.3. Checking for clock pitfalls of hardware development guide

http://www.nxp.com/assets/documents/data/en/user-guides/IMX7DSHDG.pdf 

Table 9. Oscillator and clock recommendations

http://www.nxp.com/assets/documents/data/en/user-guides/IMX7DSHDG.pdf 

Section 5.3 Crystal Oscillator (XTALOSC)

http://www.nxp.com/assets/documents/data/en/reference-manuals/IMX7DRM.pdf 

Ko-hey

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art
NXP Employee
NXP Employee

The duty cycle of the RTC_XTALI input signal should be no worse than 50% +/- 10%.

There are no strong requirements to the jitter specifications of the RTC_XTALI signal since it does not drive any PLL, and, basically, its instability only affects the precision of RTC.

The typical data of a 32kHz crystal, used with the i.MX7 processors, are as attached.


Have a great day,
Artur

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art
NXP Employee
NXP Employee

The duty cycle of the RTC_XTALI input signal should be no worse than 50% +/- 10%.

There are no strong requirements to the jitter specifications of the RTC_XTALI signal since it does not drive any PLL, and, basically, its instability only affects the precision of RTC.

The typical data of a 32kHz crystal, used with the i.MX7 processors, are as attached.


Have a great day,
Artur

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

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rfet
Contributor I

We would use an external RTC-Clock on RTC_XTALI with duty cycle 60% +/- 10%, so how strict are these specifications? 

What are the reasons für such an exactly duty cycle?

Regards,

Raphael

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ko-hey
Senior Contributor II

Is there no spec for it ?

Could someone follow the question ?

Ko-hey

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