I am attaching the datasheet of the MCU used in the Teensy 4.1, I am not sure about 4.3.2.1 General purpose I/O AC parameters in the datasheet. (Page 39 & 40) - the file is too big so here is link to digikey https://www.nxp.com/docs/en/nxp/data-sheets/IMXRT1060CEC.pdf