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SN74CB3Q3257: SI Impact of Part

Alejandro Fernandez74
Prodigy 10 points
Part Number: SN74CB3Q3257

The application is to mux an SD Card interface between two different processors using SN74CB3Q3257RGYR. The max clock speed will run at 33MHz. Wondering what is the impact of running the high-speed clock/data through the mux, I was thinking specifically in terms of SI. From what I understand the mux will be just a small resistance on the line (Rds ON) but was wondering if just by having to go through the device you could get impedance discontinuities and potential to impact the signals integrity.

The device lists USB as a possible applications but I just wanted to make sure it can handle high speed data rate without impacting SI and if there is any special considerations I need to take to make sure.

Thanks,

Alejandro

  • 0
    TI__Mastermind 45340 points

    Alejandro,

    As you mentioned above the SN74CB3Q3257 device is advertised for high bandwidth signals because it has low input capacitance which helps support higher bandwidth signals.  In addition to the slight Rdson or insertion loss you will also have some signal attenuation due to the on state capacitance parasitic as well.  

    You can see more of the high frequency performance of the SN74CB3QXXXX family of devices which shows how the low input capacitance will support high frequency signals.  The difference between the input and output of the wave form below is a slight attenuation due to the insertion loss and slight slowing down of the edge rate due to the capacitance.

    The above except is taken from application note CBT-C, CB3T, and CB3Q Signal-Switch Families.

    Thank you,

    Adam