CC2541: CC2541F256 Crystal Selection

Mehmet Eyup Arslan

Part Number: CC2541
Other Parts Discussed in Thread: CC2500

Hi,

I made a design for the cc2541 by following the EM reference design.

I had some questions about crystals.

I've calculated the drive level of the crystal. I saw that the crystal was way above what it offered. (recommended max 200 uW)

32 MHz FA-128 32.0000MF20X-K3 Datasheet: https://support.epson.biz/td/ps/productinfo.php?pn=Q22FA12800092

I also share my calculation.

I found 646 uW according to my calculations. May I ask if this is a problem? or is the formula I used for calculation correct?

Because this is a suggested crystal and this much difference worried me. The same problem applies to the 32.768kHz crystal.

I'm looking forward to your answers.

Regards,

Mehmet

over 5 years ago

0 Alexis Crandall20 over 5 years ago

TI__Genius 15590 points

Hi Mehmet,

The equation for drive level (in terms of W) is:

DL = 2 x ESR (πf(CL + CM) VPP) ^2

Here is a good resource:

https://www.ti.com/lit/an/swra495h/swra495h.pdf

Thanks,

Alexis

0 Mehmet Eyup Arslan over 5 years ago in reply to Alexis Crandall20

Intellectual 745 points

Hi Alexis,

I examined the document you shared. The document says I can get 1.6Vmax for Vpp.

When I do my calculation according to this, it is again a high value. (310 uW)

I think the Vpp value changes according to which Ic we useso I looked for the vpp value for cc2541 and couldn't find it.

I saw 0.4V for the cc2500 should I use it?

Is there a specific vpp value for cc2541?

Regards,

Mehmet

0 Alexis Crandall20 over 5 years ago in reply to Mehmet Eyup Arslan

TI__Genius 15590 points

Mehmet,

Yes the same Vpp should apply. Perhaps this would be a more relevant document to reference: AN100 - Crystal Selection Guide

Thanks,

Alexis

0 Mehmet Eyup Arslan over 5 years ago in reply to Alexis Crandall20

Intellectual 745 points

Hi Alexis,

Which vpp suits 0.4V or 1.6V. because when I do it for 1.6V, the crystals in the documents you shared are not suitable. (and this doesn't make sense because you are directly recommending it.)

I've been searching for a while and haven't found a specific value for Vpp. It is ok when I do it according to 0.4V, but can you give a clear answer about what value I should take for CC2541? I did a lot of research, I couldn't find a clear result.

I reviewed 2 of the documents you shared, but it did not bring me to a conclusion.

Do I really need to search for vpp that much here? or if I use crystals similar to the recommended crystal properties, will I have problems?

Regards,

Mehmet

0 PM over 5 years ago in reply to Mehmet Eyup Arslan

TI__Mastermind 27145 points

Hi,

It is 0.4PP.

We recommend to use the Crystals in our Reference design or equivalent to it.

This is a well proven design and we didn't see ant failures with the Crystals.

Thanks,

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CC2541: CC2541F256 Crystal Selection