9 Replies Latest reply on Mar 5, 2016 11:37 AM by lasse_1601576

Finding an appropriate crystal for CY7C68013A (FX2LP)

omkar.vedpathak Jun 29, 2012 4:07 AM

Hi,

I am using the CY7C68013A chip on our PCB, and was looking for an appropriate crystal to meet the required specifications as described in you application notes (point 4 on AN15456).

I am unable to find either crystal recommended in your app note or other crystals that meet the required specs of:

■ Parallel resonant
■ Fundamental mode
■ Frequency Stability: ±100 ppm
■ 500-uW drive level
■ 12pF (5% tolerance) load capacitors

Furthermore, the crystals used on the devboard CY3684 dev kit and the UPEK FISK USB reference design that incorporates the NX2LP chip (CY7C68033-56LFXC) do not meet the above specifications.

Could you please inform me whether it is necessary to use at least 500-uW drive level crystal, and whether I can use crystals with other load capacitances in my design.

Many Thanks,

Sach

1. Re: Finding an appropriate crystal for CY7C68013A (FX2LP)

ramav_01 Jun 27, 2012 8:43 AM (in response to omkar.vedpathak)

Yes. It is recommended to use a crystal with that specifications.

The part that is there on the FX2LP DVK is: ECS-240-20-4. I think this part is available. Please check.

Regards,

sai krishna.
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2. Re: Finding an appropriate crystal for CY7C68013A (FX2LP)

omkar.vedpathak Jun 27, 2012 9:50 AM (in response to omkar.vedpathak)

Can you please recommend a smaller package crystal that still meets the specs - the crystal you have sent me is very large!

Thanks
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3. Re: Finding an appropriate crystal for CY7C68013A (FX2LP)

omkar.vedpathak Jun 28, 2012 7:23 AM (in response to omkar.vedpathak)

Hi,



Another thing : the part you have recommended (as used on the dev board) has a 20pF load capacitance (where 12pF is recommended in the applciation note) - so am I right in thinking it doesn't matter what load capacitance crystal we use with the chip?



Thanks
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4. Re: Finding an appropriate crystal for CY7C68013A (FX2LP)

ananda_26 Jun 28, 2012 8:37 PM (in response to omkar.vedpathak)

It has to do with the crystal startup. FX2LP has been extensively tested with 12pF load. So please use a 12 pF load.

Regards,

Anand
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5. Re: Finding an appropriate crystal for CY7C68013A (FX2LP)

omkar.vedpathak Jun 29, 2012 3:05 AM (in response to omkar.vedpathak)

Hi Anand,

I really don't get it though, why have you used a 20pF crystal on the dev board for FX2LP? I would really appreciate it if you could even give me an example of a (small) part that has a load capacitance of 12pF and drive level of 500uW as none of our suppliers (RS components, digikey, farnell, mouser) seem to have such a product (in mass supply greater than quantities of 250) on a glance through their product catalogs.



The following crystals appear to meet the specs, but they may be close to end of line as their stocks are low...

http://uk.farnell.com/aker/c7s-24-000-12-3030-x/crystal-smd-ceramic-24-000mhz/dp/1538819

http://uk.farnell.com/aker/c6s-24-000-12-3030-x/crystal-smd-cer-24-000mhz/dp/1538833

Many Thanks
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6. Re: Finding an appropriate crystal for CY7C68013A (FX2LP)

user_1377889 Jun 29, 2012 3:13 AM (in response to omkar.vedpathak)

Isn't there a capacitance of ~7pF at the Pin itself which gives about 20pF together with the 12pF capacitor? As such, you'll need a 20pF x-tal.

Bob
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7. Re: Finding an appropriate crystal for CY7C68013A (FX2LP)

omkar.vedpathak Jun 29, 2012 3:58 AM (in response to omkar.vedpathak)

Oh of course!!!!!! Excuse my ignorance. Many thanks for the clarification
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8. Re: Finding an appropriate crystal for CY7C68013A (FX2LP)

user_1377889 Jun 29, 2012 4:07 AM (in response to omkar.vedpathak)

Glad to have helped you!

Bob
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9. Re: Finding an appropriate crystal for CY7C68013A (FX2LP)

lasse_1601576 Mar 5, 2016 11:37 AM (in response to omkar.vedpathak)

Hi,

we have a similarly problem. We implemented a CY7C68013A-56 in our design and now we are looking for a crystal in 3.2x2.5 case.


I'm a bit confused because the FX2LP DMB-T/H TV Dongle Reference Design also use a 3.2x2.5 crystal (Hosonic E3SB 24.000 18pF) that is able to handle 100uW(200uW max) without any damping resistor in the circuit. What is the "normal" drive level of FX2LP?

Is this a proper solution? I think the Hosonic crystal will be very similarly to ABM8, which is a good available part, just the shunt capacitance deviates.



Best regards
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