Switch between two TCXOs to feeding ADF4350

Hi Lotus,

I assume that the switch shares the supply voltage with the ADF4350(3.3V +/-10%) and the TCXO signals are single ended. If that is the case, you can use any of the following switches: ADG619/719/749/779.

For diferential TCXO signals the ADG636/736/787/772 can be used.

Regards,

FEB

Hi, FEB:

Thank you for your help.  My switch shares the supply voltage with the ADF4350(3.3V +/-10%) and the TCXO signals are single ended.

Since ADG619/719/749/779 are analog switch, they should not add jitter for the TCXO reference signal, right?

Thank you in advance.

Lotus

Hi, lotus!

ADG619/719/749/779  analog switch not add jitter for the TCXO reference signal.

PSB will be carefully created only.

Regards!

Hi Lotus,

The analog switch is not jitter free, but if you choose a device with the lowest ON resistance, it will minimize the random jitter due to the noise introduced by the switch resistance. On the other hand, the bandwidth of the switch has to be sufficiently high to pass the signal with minimum distortion to reduce the amount of deterministic jitter introduced by the switch.

Regards,

FEB

Hi!

PSB is printed circuit board only .

Jitter is very-very low, as at passive component (as resistor with equal value ) Don't worry!

Hi, FEB:

Do you have any recommendation which switch to use (with lowest ON resistance) and least jitter.  I have looked at ADG839 with 0.6ohm ON resistance.  But most of parts do not provide jitter information.

Do you have specs for jitter performance of those switches?

Thank you in advance.

Regards

Lotus

Hi, Georgy:

Thank you for your reply.  What do you mean PSB?  FSB suggested ADG619/719/749/779  analog switch does introduce jitter, I am confused a little bit.  Maybe the jitter is due to the ON resistance uncertainty.

Regards,

Lotus

Hi Lotus,

I'm not familiar with TCXOs, but I assume the signal they provide is either a sine or square wave. Would it be possible to share with us some more details about the TCXO signals  such as frequency and rise/fall time(square wave only)?

Regards,

FEB

Dear FEB:

The TCXO we use is 26M Hz TCXO with chipper sine wave output.  The part is from NDK.  Please see the attached PDF file.  The chipped sine wave is perfered since it will feed to the ADF4350 synthesize as reference clock.  Squrewave has a lot of harmonics.

The reason to switch between two TCXOs is that sometimes we need to use external 10M sinewave input instead of this TCXO for synchronization purpose.

So in this case, we need to switch between this TCXO and external 10M refrence input (typicall Sinewave, from Test equipment).

Thank you very much.

Regards,

Tim

Hi Tim,

Since you want to select between a 10MHz size and the 26MHz TCXO, I would suggest to start by estimating the bandwidth of the 26MHz clipped sine wave from the TXCO and choose a switch with the lowest On resistance that meets the bandwidth criteria.

The ADG839 has a bandwidth of 25MHz which is less than the fundamental frequency of the TCXO. I would recommend instead the ADG849 which has 38MHz bandwidth with a similar ON resistance or the ADG852 for 100MHz with higher ON resistance of about 1.5 Ohms.

Regards,

FEB