245.76 MHz Filter "FLT1" on the ADS62P49EVM

Stefan von der Mark

Other Parts Discussed in Thread: CDCE72010

Hi,

I want to use the ADS62P49EVM with the onboard-clocking using the onboard CDCE72010 ("Clock Option 2" as described in section 2.2.4.2 of the User Guide).

For this configuration, I need a chrystal filter of 245.76 MHz, which unfortunately is not populated by default. The desing is obviously meant for a certain filter, as there is onboard matching and a certain footprint, however there is no hint in the documentation for specs of this filter other than the center frequency.

Can anyone give me a hint which filter I can use here?

Alternatively, I could use "Clock Option 3" using the LVPECL connection which does not need this filter. However, section 2.2.4.3 sais this option is "not recommended for SNR critical applications". Why is that so? What is the issue with this configuration? I have seen LVPECL connections between clock cleaners and ADC/DAC devices in many Appnotes, so this seems a quite common way to go.

Thanks for your help,

Stefan

over 15 years ago

0 Thomas Neu over 15 years ago

TI__Expert 3865 points

Hello Stefan,

I just checked the BOM for the EVM and see the crystal filter is from Toyocom:

Mfr_Name

Mfr_Part_Number

Toyocom

TF2-Q5EC1

I found the spec and am attaching it.

Option 3 without a filter will result in lower SNR results due to increased jitter. If there is no bandlimit of the phase noise on the clock input, the phase noise of the other Nyquist zones will fold into the Nyquist zone and increase the noise floor degrading the SNR.

We started a write up of clock jitter and here is a link to the first part:

http://focus.ti.com/lit/an/slyt379/slyt379.pdf

In this case the CDCE72010 output phase noise would have to be integrated to an offset of ~250MHz while the BPF limits it ~10MHz offset.

Best regards,

Tommy

TF2-Q5EC1 245.76MHz(ISDD-2C-0251_TI).pdf

0 Stefan von der Mark over 15 years ago in reply to Thomas Neu

Prodigy 20 points

Hi,

I did some research on this "TF2-Q5EC1", and it seems that it is (no longer?) available, at least Toyocom doesnt list it anymore, and the distributors cannot provide it.

Is there any replacement part or other workaround you can recommend, such that I can still use this clocking option on the EVM?

Thanks,

Stefan

0 Richard Prentice over 15 years ago in reply to Stefan von der Mark

TI__Mastermind 29220 points

Hi,

I think this part number might be a ‘TI only’ part number from Toyocom, although we were not trying to hide any details on this item. But this filter is in a common Toyocom footprint and there are standard part numbers for this footprint as well.

Looking at the Epson Toyocom site, I believe

http://www.epsontoyocom.co.jp/english/product/Filter/set01/hf362a/index.html

http://www.epsontoyocom.co.jp/english/product/Filter/set01/hf363a/index.html

fit the footprint.

Regards,

Richard P.

0 Volodymyr Sydoruk over 12 years ago in reply to Richard Prentice

Prodigy 20 points

Hi,

This TF2-Q5EC1 filters are not available anymore, could you please suggested an alternative that can be populated on EVM board.

Thank you and kind regards,

Volodymyr

0 Kang Hsia over 12 years ago in reply to Volodymyr Sydoruk

TI__Guru* 79024 points

Hi,

We are checking with Toyocom on a suitable replacement. Will keep you updated.

-KH

0 Ghorbel Mourad over 11 years ago in reply to Richard Prentice

Intellectual 610 points

Hi,

In ADS62P49EVM the crystal filter of 245.76 MHz is preceded and followed by a network composed by 1pF capacitor in parallel with 180nH inductor and a capacitor of 22pF was in series. I know that the terminating impedance of the filter is 150ohn||5.5pF, but when I try matching this impedance with 50ohm, I have never find a network like the network of ADS62P49EVM.

My question is, what is the role of this network of 22pF,(180nH||1pF)?

And, I have an other question, for witch clock option, do I install the R103 (121ohm) and R90 (121ohm), and why their value is equal to 121ohm?

Thanks for your help,

Mourad.

0 Ronnie Wong over 8 years ago in reply to Kang Hsia

Prodigy 80 points

Hi Kang,

Was there an update to this posting? We're currently using this board and would need the VCX01 and FLT1 (ie TF2-Q5EC1) but its 2017 now and not sure what the replacement would be. Thank you.

Regards,
Ron.

0 jim s over 8 years ago in reply to Ronnie Wong

TI__Guru* 91947 points

Ronnie,

A 5mmx7mm part with 2.54mm pitch will fit for the VCXO. This part below might be a possible replacement. You will need to double check the data sheet.

https://www.digikey.com/product-detail/en/abracon-llc/ASG-P-V-A-491.520MHZ/535-11806-ND/3315218

I have not found a replacement for the filter. I would suggest shorting the path with a 0 Ohm resistor for this.

Regards,

Jim

0 Ronnie Wong over 8 years ago in reply to jim s

Prodigy 80 points

Thank you Jim. 'much appreciated.
Regards,
Ron.

Data converters

Data converters forum

245.76 MHz Filter "FLT1" on the ADS62P49EVM