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Altera_Forum's avatar
Altera_Forum
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17 years ago

5 V in and out

Now my little project is almost finished. The last problem is how to get 5 V out from the board (Terasic micro kit). The board is connected to USB port and it outputs 3.3 V. But I want to read signal...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
17 years ago

What is that PCI clamp diode? I read the following about multi-voltage systems:

"To make MAX II device outputs compatible with 5.0-V CMOS devices, configure the output pins as open-drain pins with the PCI clamp diode enabled, and use an external pull-up resistor."

"MAX II devices can interface with 5.0-V devices by slightly modifying the external hardware interface and enabling PCI clamping diodes via the Quartus II software."

And what is open-drain pin? How to enable PCI clamping diode? Sorry my newbie questions...

This is from Quartus Help:

"MAX II devices have a device-wide output enable (DEV_OE) to control the output enable for every output pin in the design and an internal PCI clamp diode, which can make the device 5.0-V tolerant with the use of an external resistor."