LMX2572: LMX2572 VTune

Part Number: LMX2572

Dear Texas Instruments Specialists,

I hope this message finds you well.

I am currently working with the LMX2572 PLL synthesizer for a project and have a query regarding its functionality.

Specifically, I would like to inquire about the feasibility of driving the Vtune input of the LMX2572 from an external voltage source. Could you please confirm whether this is supported by the device's design and specifications?

Any insights or guidance you could provide on this matter would be greatly appreciated.

Thank you for your attention to this inquiry. I look forward to hearing from you at your earliest convenience.

over 1 year ago

+1 vicente flores prado over 1 year ago

TI__Mastermind 29542 points

Hello BZ,
I believe this is possible but be sure you have picked the correct VCO core (VCO_SEL) as well as VCO band (VCO_CAPCTRL) before trying to lock the VCO.

Regards,

Vicente

0 BZ over 1 year ago in reply to vicente flores prado

Prodigy 40 points

Hello,
Thanks for your responce.
I tryed ,its work but for exactly frequency i think that needs store calibrations table.

0 vicente flores prado over 1 year ago in reply to BZ

TI__Mastermind 29542 points

Hello BZ,

Do you mean you’re attempting to use full assist while using an external PLL?

Regards,

Vicente

0 BZ over 1 year ago in reply to vicente flores prado

Prodigy 40 points

Hello,

No external PLL,

disconnect loop filter and drive v_tune from external DAC.

+1 Noel Fung over 1 year ago in reply to BZ

TI__Guru** 111590 points

Hi BZ,

You need to do a VCO calibration and a register read back to find out the exact VCO parameters (VCO_SEL; VCO_CAPCTRL and VCO_DACISET) for the frequency you want. When you apply the data, you have to put the device in full assist mode. Looks like you have successfully done so.

If the configuration is correct, DAC output voltage should be around 1.3V.

Limit the DAC output voltage to 2.5V max. or otherwise there is a risk that the Vtune pin of the device will be over driven.

Clock & timing

Clock & timing forum

LMX2572: LMX2572 VTune