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re: SN74CBTD3306PWR - cross talk between input and output.

Anjli Behl
Prodigy 715 points
Other Parts Discussed in Thread: SN74CBTD3306C

Hello,

I am posting on behalf of my customer:

"We are using the SN74CBTD3306PWR. When it is not conducting we observe some crosstalk between the input and the output. 1) I cant find the Cf specification on the datasheet. (The parasitic capacitor between the input and output when the switch is not conducting) Can you provide this information? 2) Do you have another switch to recommend that would have lower Cf capacity between input and output when the switch is off. (It would be preferable to keep the same footprint/package to avoid a rework on our PCB if possible) Thanks"

 

  • 0
    TI__Mastermind 46480 points

    The CBTD devices can only run at lower frequencies.  i dont believ the capacitance is the issue. There are a couple of options. CBT3306 with external diode on Vcc. This would function the same as the CBTD but would not have the frequency limitation. You could also use the CB3T3306. This would require you use 3.3V for Vcc instead of 5V.

    Either of these options should work.

     

  • 0 in reply to Chris Cockrill
    Prodigy 90 points

    Thanks to anjli for putting my question in this forum.

    First we prefer not changing the present design.. I need to keep the 5V Vcc.

    You are right, it may not be a cross talk issue caused by parasitic capacitor.  Some scope measure show the output change (OFF condition) when the input start to go negative.   The under-shoot is present in the DDC CLOCK and DATA wire of our DVI cable input going to the switch. It appear the switch is not OFF when the signal goes under-shoot condition.  I have asked some sample of SN74CBTD3306C 5V-V BUS switch with -2V undershoot protection.  The foot print is the same, and it operate at 5V. DO you think this will solve my problem?

     

  • 0 in reply to sylvain fortin
    TI__Mastermind 46480 points

    These parts will turn on with an undershoot greater than -.5V so if this is causing the problem then the C rev device should solve your problem.