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Altera_Forum's avatar
Altera_Forum
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19 years ago

Cyclone3 external clamp diodes

I am getting the following warning and I have no idea why. Do I really need external clamp diodeas? Warning: Following 17 pins must use external clamping diodes. Info: Pin data[0] uses ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
19 years ago

Clamp diodes can be used to make a pin tolerant to higher input voltages than what they are specified to operate. For example, if you have a 3.3V LVTTL input buffer. And you want to make it 5V tolerant you can use an external clamp diode to clamp the voltage and limit the current to prevent damage and allow operation (Driven by 5V). Same notion applies for lower voltages.