ARC termination circuits

The ADV7622/3 and ADV7511 have different ARC termination circuits. On the ADV7511, the coupling capacitors are in-line but on the ADV7622, the coupling capacitors are in parallel. Why is this?

  • The ADV7511 has a three pin ARC architecture – it has two dedicated HEAC pins and a dedicated HPD pin.

    The ADV7622/2 has a two pin ARC architecture – the hot plug and one of the arc inputs share the same pin.

    This is the reason that the termination circuits are different on both – it is not possible to use series coupling capacitors on the two pin ARC architecture as it would remove the 5V DC HPD level.

    The circuits are required to set the correct voltage levels on the ARC inputs.

  • Hi joe.triggs,

    ADV7511 has a 3-pin architecture : 2 dedicated HEAC pins and 1 dedicated HPD pin.

    However on the HDMI connector, its the same pin thats used for HEAC- and HPD as well! (Pin19 of TYPE-A connector).

    In that case, how will be the connections? Will the HEAC- on HDMI connector be connected to HEAC- and HPD as well? Please advice.

    Thanks,

    Chetan

  • Hi Chetan,

    There is a reference circuit shown in the following schematic for our ADV7511 evaluation board - http://www.analog.com/static/imported-files/eval_boards/ADV7511_ADV7343_Eval_Schematic.pdf. This board shows how the HPD must be tapped off before the AC coupling caps.

    Best regards,

    Joe

  • Thanks for the streaming response Joe!

    That helps!

    With respect to the reference schematics you shared,

    1. Pull-up or pull-down for HEAC+ and HEAC- signals? The eval board schematics suggests 49E9 pull down         whereas the hardware user guide recommends 50R pull-up? Its conflicting! What should be default       configuration? Please suggest.

    2. What is the purpose of D600 on AV0_CEC signal?

    3. Is it recommended to have ESD protection on HEAC+ and HEAC- lines?

    4. If I dont intend to use I2S, DSD port of ADV7511, and SPDIF IN, is it ok to terminate these pins to ground?       Please confirm!

    5. Whats the significance of the buffer U17 placed on the HDP line. I believe its just for an LED indication               whenever a HDMI sink is detected.

    Best Regards,

    Chetan

  • Hi Chetan,

    In-line answers below ...

    1. Pull-up or pull-down for HEAC+ and HEAC- signals? The eval board schematics suggests 49E9 pull down whereas the hardware user guide recommends 50R pull-up? Its conflicting! What should be default configuration? Please suggest.

    >> 50ohm is not a common resister size from our passive supplier. We selected 49.9ohm as it was more readily available to us. The 0.002% difference is unlikely to cause an issue for this termination.

    2. What is the purpose of D600 on AV0_CEC signal?

    >> It is a low leakage diode to ensure that the CEC network adheres to the HDMI Compliance Test Specification for CEC leakage. Please refer to the HDMI CTS.

    3. Is it recommended to have ESD protection on HEAC+ and HEAC- lines?

    >> We recommend ESD protection - it is shown in all of our reference designs.

    4. If I dont intend to use I2S, DSD port of ADV7511, and SPDIF IN, is it ok to terminate these pins to ground? Please confirm!

    >> For unused pin recommenations, please refer to the ADV7511 Hardware User Guide - http://www.analog.com/static/imported-files/eval_boards/ADV7511_Hardware_Users_Guide.pdf

    5. Whats the significance of the buffer U17 placed on the HDP line. I believe its just for an LED indication whenever a HDMI sink is detected.

    >> This is correct.

    Best regards,

    Joe