From the iMX8 hardware development pdf, there's a paragraph about the HDMI signals
"For the HDMI output, 604 Ω resistors on the positive and negative sides of each high-speed output pair are grounded through a FET. The gate to this FET should be tied to the 1.8 V power for the HDMI transmit circuitry (HDMI_AVDDIO, ball P2). This will disconnect the resistors automatically when the HDMI transmit circuitry is powered down. Although a single FET is adequate to achieve the functionality, a dedicated FET for each signal can provide better isolation between signals and minimize crosstalk."
Is the FET is necessary? Do we need it for some sort of start up condition or is it just for circuit protection? In my design, the HDMI signals are being sent directly to another chip on the board and the HDMI will basically always be on whenever the iMX8 is on.
Yes, it is needed, refer you to refer to our reference design, and following the hardware guide: