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SN74CBT16209A: VOH and VOL values

Berlauber
Intellectual 260 points
Part Number: SN74CBT16209A

Hello,

I would like to use the SN74CBT16209AD as a two 9-bit bus multiplexer, only using the functions A1=B1 or A1=B2. I will supply the chip with 5VDC and I do not want to perform any level translation. I would like to clarify the following points:

-What are the VOH and VOL levels for inputs that can be TTL 3.3 or 5V (VCC=5VDC)?

- Unused A2 pins, can be left floating?

- Is available any reference design?

Thank you so much.

Best Regards

  • 0
    TI__Genius 9132 points

    Hi,

    The SN74CBT16209A is a passive FET switch and doesn't have any driving capability. Since this part can't source or sink current those specifications are not applicable to the device.

    I found this posting when typing in Voh and Vol into the switches and multiplexers search bar:

    You can leave unused signal pins floating but it is recommended to connect them to ground to keep them at a known voltage state.

    Since you are only using  the functions A1=B1 or A1=B2 in this cross-point switch, you can also looks at using two 2:1 switches (device search tool) back-to-back (because switches are bidirectional) to achieve crosspoint/exchange functionality. This may be an option that improves performance, size, or price, depending on system requirements.

    Regards

    Saminah

  • 0 in reply to Saminah C
    Intellectual 260 points

    Hi Saminah,

    Thank you so much for your replay. Ok, since the switch is passive, I understand that the output level of the switch is the same as the input but with some losses due to the Ron resistance, is it ok?

    I looked for other switches but with two 9-bit buses there are not too many options.

    Thank you!

    Best Regards,

    Laura

  • 0 in reply to Berlauber
    TI__Genius 9132 points

    Hi Laura,

    Yes, that is correct. These devices are passive FET switch that can be thought of as a wire with some resistance (RON)  - if there is any signal shift, it will be impacted by your loading conditions and not the switch.

    The SN74CBT16209A is best option we have for 18 channels. Let us know if you have any questions about this switch.

    Regards

    Saminah

  • 0 in reply to Saminah C
    Intellectual 260 points

    Hi Saminah,

    I have another question regarding the output voltage of the switch. In the "Digital Bus Switch Selection Guide" I found the picture below. With Vcc=5V the output signal drops down to 4V (more than the losses due to the ron resisntace) (I was considering supplying the switch with Vcc=4V but after seeing the picture it seems to be a bad idea.)

    I would like to know if the 5V input TTL signals will be attenuated if the VCC is 5V or 4V.

    Thank you so much.

    Best regards

  • 0 in reply to Berlauber
    Intellectual 260 points

    Hello,

    The previous question is already solved.

    Thanks