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Contributor
Contributor
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Registered: ‎04-02-2013

Spartan-7 Clamp Diode Conducted Voltage and Max Current Details

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According to table 2 in DS189 we can sink 10mA through the ESD clamp diode on each input continuously as long as the 200 mA total per bank is not exceeded. In our use case, we will be pumping 50 to 100uA (13.8V with a 175k series resistor) through the diode on multiple (6 or 7) inputs most of the time. During fault conditions, we will be pumping closer to 200uA on a single input for hours at a time (32V with a 175k resistor in series).  Is that an issue?

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Moderator
Moderator
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Registered: ‎04-18-2011

Sorry to be blunt but this is a recipe for disaster.

You can't drop 14 volts across a series resistor and apply it to the pin. 

You are going to damage the input by applying an excessive voltage to it. 

The VIn spec must be respected. The max input voltage is reccommended to be VCCO +200mV. The absolute max spec is a little higher but no where near what you are proposing. 

The diode is there to protect the input from ESD. So it is not meant to be conducting at all under normal circumstances. We probably won't characterise the diode being on constantly. 

 

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Moderator
Moderator
393 Views
Registered: ‎04-18-2011

Sorry to be blunt but this is a recipe for disaster.

You can't drop 14 volts across a series resistor and apply it to the pin. 

You are going to damage the input by applying an excessive voltage to it. 

The VIn spec must be respected. The max input voltage is reccommended to be VCCO +200mV. The absolute max spec is a little higher but no where near what you are proposing. 

The diode is there to protect the input from ESD. So it is not meant to be conducting at all under normal circumstances. We probably won't characterise the diode being on constantly. 

 

-------------------------------------------------------------------------
Don’t forget to reply, kudo, and accept as solution.
-------------------------------------------------------------------------

View solution in original post

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Contributor
Contributor
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Registered: ‎04-02-2013

Thanks for clearing this up for us.

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