OMAP-L138 internal RTC accuracy.

sheshadri TN

Prodigy 40 points

Other Parts Discussed in Thread: OMAP-L138, OMAPL138

Hi Team,

Our requirement is on RTC accuracy of 3ppm.

With OMAP-L138 internal RTC, can we achieve the accuracy by using 3ppm crystal or oscillator?.

Or else we need to go for the external RTC for better accuracy?.

Thanks in Advance.

over 11 years ago

0 Shankari G over 11 years ago

TI__Mastermind 43955 points

Hi Sheshadri,

We will check and get back to you.

Regards,

Shankari

0 Shankari G over 11 years ago

TI__Mastermind 43955 points

Hi Sheshadri,

With OMAPl138 internal RTC, in the schematics of OMAPl138 LCDK, the 32.768 kHz crystal is used which has +/- 20 PPM. That is the reference we have.

OMAPL138 Schematic companion - http://processors.wiki.ti.com/index.php/OMAP-L138_LCDK_Schematic_Companion

32.768 kHz crystal used in LCDK - http://www.foxonline.com/pdfs/FX135.pdf

It is not mentioned either in the TRM or in the data sheet up to which PPM the crystal can be used for RTC. Only the frequency is maintained. And also no information about the External RTC

If needed, I will consult with the hardware team and get back.

Regards,

Shankari

-------------------------------------------------------------------------------------------------------

Please click the Verify Answer button on this post if it answers your question.
--------------------------------------------------------------------------------------------------------

0 Senthilkumar Srinivasan over 11 years ago

TI__Mastermind 43660 points

Hello Sheshadri,

There is no information available for RTC crystal PPM.

Our EVMs are having 20ppm crystal part for RTC.

In my opinion, you can use 3ppm crystal to improve the accuracy. But it is solely on designer's risk.

Regards,

Senthil

0 Titusrathinaraj Stalin over 11 years ago

TI__Guru** 116100 points

Hi,

In addition to Senthil & Shankari points,

The cost is not constraint on your project and accuracy is important then you can choose external RTC with low PPM crystal if reference design is available.

In my opinion, If low PPM crystal device will be more cost than high PPM crystal oscillator.

Processors

Processors forum

OMAP-L138 internal RTC accuracy.