SN74CBTLV3257: SN74CBTLV3257PWR schematic

Hello Lawrence,

 If this is a high frequency application I suggest on U40 you should tie 3A(pin9) and 4A(pin12)  to ground through a termination resistor (normally 50 ohm resistor) but 4.7k Ohm resistor will be fine. This is due to the possibility of noise coupling to the unused inputs and introducing crosstalk into the multiplexer which can cause fluctuations on other inputs and outputs on the device itself.

Also the logic input EN (pin15) of all of these devices doesn't need a termination resistor and can be directly tie to ground.

Check out this FAQ What to do with unused pins:

e2e.ti.com/.../faq-what-to-do-with-unused-pins-exposed-thermal-pads

Thanks and Regards,

Kameron Hill