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I want to connect level translators like 74LVC1T45 to a microcontroller to translate high speed signals from 3.3v to 5v. I want to make sure it works for frequencies up to 40 MHz. The traces on the PCB can end up to be as long as 15cm.

Do I need to worry about impedance matching between the microcontroller and 74LVC1T45 to reduce reflections? The worry is I don't want to generate noise in the power rails or cross talk with other traces and hope this can be be reduced or eliminated with correct termination resistors.

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    \$\begingroup\$ It's on the cusp of being problematic without some form of termination. \$\endgroup\$
    – Andy aka
    Jul 27, 2021 at 12:10
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    \$\begingroup\$ You are on Lambda/50 .....Hmm I think you can get away with it. \$\endgroup\$
    – Mitu Raj
    Jul 28, 2021 at 7:57

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Do I need to worry about impedance matching between the microcontroller and 74LVC1T45 to reduce reflections?

No, because the source driver has no characteristic impedance. In addition, transmission line effects usually don't have an affect until ~50MHz.

What will affect the signals is capacitance which will affect the rise times, so try and keep that low.

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