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Altera_Forum
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15 years ago

Help about the connection between IC of voltage 5V and cyclone II

Now I've got a cyclone II(3.3v in doc) device.But I've only got a 5V D-A IC.Can I connect them directly?especially output from 5V IC input foot of cyclone II(3.3V in document).I know the signal outpu...
Altera_Forum's avatar
Altera_Forum
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15 years ago

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ALTERA themselves provide this solution

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Right, but in my opinion it's a kind of misleading without mentioning the problem of unconfigured device behaviour. Of course, it works for those circuits, where can prevent the 5V device from driving out a high level in unconfigured FPGA state. For others (which are actually most circuits according to my experience), an external clamp diode or a different level conversion solution should be used. Anyway, I prefer the Altera way to those competitor devices that have permanent clamp diodes.