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ADV7613 output white noise image when electrostatics injecting

Category: Hardware

System structure: HDMI connects to the ADV7613 to drive the LCD directly.

HDMI Source ----> ADV7613 ---->  LCD

When injecting electrostatics into the system, LCD images become white noise(As shown in the following figure)

But if disconnect the DDC(I2C) between HDMI source and ADV7613, LCD images are normal when electrostatics injecting.

My question:

1, How to make the ADV7613 output a white noise image

2, Why disconnecting the DDC affects the image output of the ADV7613

Thank you so much

  • Hi,

    1) The device has inbuilt internal ESD protection, however when design boards the designers always add extra external ESD protection just to enhance the protection.

    In our ADV761x evaluation board, We have used additional ESD protection devices HDMI connector and ADV761x. Please refer our schematic for the specification of this ESD protection circuit So we strongly recommend ESD protection circuits on the inputs as shown in many of our evaluation boards

    Kindly note, a 100 Ohm series resistor in combination with internal ESD will protect the input against any ESD hits on the connector.

    Note:

    ESD damage can be caused by over voltage burning through the input gate oxide layers. ESD protection is meant to stop these over voltage conditions without impacting the impedance path under normal operating modes.

    2) ESD protection can be burned out when it has to shunt excessive energy from the source. Normal ESD hits can't do this, repetitive hits can cause problems. Strictly a thermal issue. With the decoupling caps this would be also impossible to do.

    So, the damage to an input pin can be caused by over voltage blowing through the gate oxide or excessive repetitive energy hits.

    2) Why disconnecting the DDC affects the image output of the ADV7613 ?

          It will not affect the output image but it is not possible for you to support EDID and HDCP protocol.

    Kindly note, If DDC signals are not connected to the HDMI receive connector, it means that the source device will not be able to read your board's EDID. Furthermore, in case you are planning to support HDCP, the source device will not be able to do HDCP since HDCP requires DDC communication. 

    Thanks,

    Poornima

  • This looks like the source continues to transmit video when the HDCP keys are not authenticated.  We call this snow.  HDCP keys are authenticated over the DDC link.  No DDC, you get snow.  Normally sources will stop the video stream or transmit black screens.  

  • It sounds like your ESD test corrupted the HDCP key transactions.