Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

DC Characteristics

In the cyclone II handbook,page 5-4,pin pull-up resistance values will be lower if an external source drivers the pin higher than Vccio. i don't understand it . Please explain it . Thanks
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

If you drive the pin at a higher voltage than Vccio, the clamping diode will start drawing current, thus lowering the impedance seen from outside.