LVDS25/LVPECL driving a HMC723LP3

Hello ffrank,

LVDS25 has a common mode voltage of 1.25V with swing between 1.075V and 1.425V. If you shift voltages of HMC723 from GND/-3.3V to 1.425V/-1.875V, that would solve your issue. Please refer to the page 18 of the application note I attach.

Regards

Sinan 

Dear Sir:

       I'm facing a similar problem as ffrank, I want to drive the HMC723LP3 inputs by a LVDS(1.8V) buffer of a FPGA (Virtex+ UltraScale). 

       The signal from the FPGA is AC-coupled through two capacitors, and the supply voltage of the HMC723LP3 is -3.3V, however, there is no output signal from the HMC723LP3. 

        Could you please tell me what's your advice to adjust the input standard in order to satisfy the command? Or I just need to shift voltages of HMC723 from GND/-3.3V to 1.425V/-1.875V like above?

       Best regards!

Hi,

You dont need to shift supplies of HMC723 if you are driving it with AC-coupling. LVDS1.8V should provide 300mV swing with 50ohms source impedance. This should be enough for HMC723.

By the way do you have other inputs outputs AC coupled as well?

Dear Sir,

Thanks so much for solving my problem, but I'm not very clear of your question about the input/output AC coupled as well, as a matter of fact, there is a couple of input clock which frequency is 100MHz, and it is AC coupled, however, the output signal from pin QN/P is not AC coupled. 

Best regards!

Hi,

HMC723's inputs and outputs are referenced to ground with 50ohms. CML swings will be between 0 to -500mV. If interfacing components with these pins are not compatible with these voltage, you need a DC block. 

Hope this is clear

Thanks so much!