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LMK04828: LVPECL DC coupling termination for low voltage power supply

Sota Shirai
Prodigy 10 points
Part Number: LMK04828
Other Parts Discussed in Thread: ADC09DJ1300, LMK04832

Hello,

Currently I try to connect SYSREF+/- differenctial pair of LMK04828 to that of  ADC09DJ1300. 
I am thinking of using DC coupling of LVPECL interface because of JESD204B interface. But I am not sure how to do that with the condition which power supply of both LMK04828 and ADC09DJ1300 are 1.8 V. 
I could find out some reference for DC coupling of LVPECL but their power supply are always either 3.3 V or 2.5 V and their Vtt (termination voltage) are Vdd - 2 V. So If I applied this to my design it would be minus voltage. 

Is it possible to apply LVPECL interface with the condition which power supply is 1.8 V and DC coupling.  

Thank you. 

  • 0
    TI__Expert 6130 points

    Hi Sota, 

    You can use an emitter resistor of 120-240 Ohms to GND on the LVPECL outputs of the LMK04828, see section 10.4 of the datasheet:

    AC coupling is recommended but not required on the outputs of the LMK04832, and the ADC09DJ1300 datasheet also recommends AC coupling SYSREF. I believe it would only be necessary to DC couple if you are using the SYSREF pulser. In that case, you would just need to verify that your system meets the common mode requirements of the ADC09DJ1300. 

    Regards, 

    Connor