04ohm resistors added at HDMI_TX[2:0] and HDMI_CLK on i.MX8MQ EVK board

[question2click6]

Hi NXP Support team,

For i.MX8MQ EVK board:

Would you help to explain why 604ohm resistors added at HDMI_TX[2:0] and HDMI_CLK? It that using for offset after AC couple?

Why not 680ohm or 49.9ohm? 

Tough 608ohm is recommended in hardware user guide, would you please share more information from HDMI IP Spec?

Thanks in advance,

Wenwen

[question2click6]

Hi Igor，

Thanks a lot for your answer!

Wenwen

[igorpadykov]

Hi Wenwen

according to HDMI specification there is termination resistance at the Sink connected to AVcc.
So the nominal high-level voltage of the signal is AVcc and the nominal low-level voltage of
the signal is (AVcc - Vswing). Since i.MX8MQ HDMI is AC coupled, output signal needs to
be level shifted to comply with specification characteristics (like Single-Ended High
Level Voltage Range should not exceed AVcc + 10 mV e.t.c.) and pull down resistors were
added for shifting voltage levels below AVcc.

Best regards
igor
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