why HDMI use ac coupling in i.MX8M

[457487600]

According to i.MX 8MDQLQ Hardware Developer’s Guide the HDMI signals should be connected to the HDMI connector through RC groups (100nF, 604R).

I‘m wondering in which condition should i use the AC coupling?What effect will it have on the HDMI monitor?

[Rita_Wang]

Hi yunqing,

RC groups is necessary for our solution.The HDMI PHY output needs to be level shifted to AVcc after on board AC coupling cap followed by pull down resistor of 600Ohms. This is to meet maximum single-ended high level output voltage, VH (Table 4-23 of HDMI Specification 1.4b).

Hope this can do help for you

Have a nice day

Rita

[457487600]

Hi Rita,

Does the maximum single-ended high-level output voltage VH (Table 4-23 of HDMI specification 1.4b) represent the following table,where AVcc=3.3V

I cannot find the maximum single-ended high-level output voltage in i.MX8M datasheet or RM, can you help?

[Rita_Wang]

Update from our expert team,   The attached table is correct one. There is no clarification in  i.MX8M datasheet or RM, so let customer to refer t.o HDMI specification 1.4b.

[Rita_Wang]

I have sent this to our expert, I will give you the update as soon as I get the reply.

[457487600]

Hi Rita,

Does the maximum single-ended high-level output voltage VH (Table 4-23 of HDMI specification 1.4b) represent the following table:

[Rita_Wang]

I will confirm it for you~~