RM48L952DZWTT crystal requirements

Dmitri Chtchvyrkov

Other Parts Discussed in Thread: RM48L952

Dear team,
Are there any data on maximum CL and ESR of the crystal for RM48L952 MCU?
The spec doesn't give much details on that subject.

Thank you,

Dmitri.

over 9 years ago

0 Anthony F. Seely over 9 years ago

TI__Guru 68970 points

Hi Dmitri,

We've debated putting this information in the datasheet but our recommendation (in the datasheet) is to send samples to your crystal vendor and have them characterize for you what crystal and tank circuit you should use.

0 Dmitri Chtchvyrkov over 9 years ago in reply to Anthony F. Seely

Prodigy 130 points

Thank you, Anthony.

Dmitri.

0 Martin Beakes over 9 years ago in reply to Anthony F. Seely

Intellectual 325 points

Hi Anthony,

Unfortunately, this process will be very hard and long (if possible) considering Alternate PN.
This will delay our current project.

From my experience, usually IC manufacturer provide all information regarding the crystal selection since there are many manufacturer with different specs. From my point of view, I think that the IC manufacturer has the best knowledge of their product and requirements.

Could TI at least provide recommended CL and ESR or some guidelines in order for us to select the proper crystal ?

Thanks for helping.

0 Anthony F. Seely over 9 years ago in reply to Martin Beakes

TI__Guru 68970 points

Martin,

This crystal vendor has an automated tool http://www.abracon.com/ to analyze the MCU and recommend a crystal & circuit for you.
Look at the bottom right of the webpage for the 'PAS' tool.

As far as I know the oscillator is tested (in production) by measuring it'd current drive capability; and it's not a number that we specify so you can't really use it for design purposes anyway.

All I can provide maybe as a hint is that in the cell design spec (TI internal document) one of the requirements is to startup a 12MHz crystal with parameters ESR=75 ohms, L=16.19mH, Cshunt=4.5pF, C1/C2=24pF (so CL=12pF), in a maximum of 1.55ms.

There isn't any sort of target ESR range in the internal doc other than this.
Don't think you can use a forum post with internal information for your design so you should really go to the vendor as recommended by the datasheet. But maybe you can get started w. these #'s for prototyping. And I would be very surprised if you have a problem with crystal startup on these devices.

-Anthony