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LMK00105: single-end input

ttd
Mastermind 8760 points
Part Number: LMK00105


Dear Technical  Support Team

My configuration is single-end input(CMOS) with 2.5V cmos Crystal oscillator(CX604AB-100.000000MHz).

The datasheet of  Crystal oscillator(CX604AB-100.000000MHz) doesn't have a output impedance spec(Ro).

So it is not installed Rs or Rs=0Ω to adjust for now.

VCC of LMK is 2.5V. Could you check the red inserted comment such as resister value and voltage on figure7?

Is it correct?

By the way, what is Vbb? Is it internal bias voltage(1.4V)? 

Best Regards,

ttd

  • 0
    TI__Genius 12885 points

    Hello ttd,

    Please note mentioned in datasheet "The output impedance of the LVCMOS driver plus Rs should be close to 50 Ω to match the characteristic impedance of the transmission line and load termination." This should clear up any questions of Rs settings.

    Vbb is pointing to the voltage divided setting of Vcc = 0.625V. This is the external bias voltage, datasheet section 8.1.1: Clock Inputs explains "the external bias voltage should be within the specified input common voltage (Vcm) range."

    The relationship of Vo,PP = 2.5V is appropriate as Vo,PP/2 = 1.25V and Vbb approx = (Vo,PP/2) x 0.5 = 0.625V.