AnsweredAssumed Answered

Overshoot on 5V tolerant pins on ADV7604 and ADV7611

Question asked by GJones on Mar 11, 2013
Latest reply on Apr 15, 2013 by GJones

Dear EngineerZone,

 

I have designed and built HDMI input interfaces using both the ADV7604 and the ADV7611 and I have a concern about the voltage tolerance on the DDC SCL and SDA pins of these devices.

 

For both devices, the data sheet states that these pins are 5V tolerant with an absolute maximum rating of 5.3V. Although the DC level on these pins is always less than 5.3V, there is some overshoot when the cable is first plugged in. This overshoot appears when one end of the HDMI cable is already plugged into the video source (such that the conductors in the cable are already charged to 5V) and the other end is then plugged into my interface. My design includes the recommended ESD protection on these pins.

 

With a 5 metre long cable, the overshoot peaks at 5.5V and is above 5.0V for 30ns. It is above 5.3V for 15ns.

 

Is this likely to be a problem?

 

How are these pins protected inside the device and where does the absolute maximum rating of 5.3V come from? For example, if the pins are protected by an internal 5V zenner diode clamp and the 5.3V rating is to avoid overheating the zenner, then I guess all is well, as the overshoot is too brief to cause overheating. If, however, there is no internal protection and exceeding 5.3V may cause the device to latch up, then I have a problem. Please provide some clarification on this.

 

Thanks for your help.

 

Best regards,

Gavin.

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