Forum Discussion

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

Urgent! hardware interface between FPGA DE2 board(3.3V) and ADC(5V)

HI, may i ask your guys a favor. I am using DE2 board for my project and i need to interchange signals(SPI) to an ADC. The ADC is 5V for logic high but the max output signal for DE2 board is only ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

Yre you sure, that the ADC actually needs 5V input level? Many devices have TTL-compatible inputs, that can be controlled by 3.3V LVTTL as well.

If you actually need a level conversion, any 74HCT or AHCT logic with 5V supply can do. DE2 GPIO pins have RD networks and can work with 5V logic level. The current load to the driving logic may be too high. Adding a 470 ohm to 1k series resistor near the DE2 board should give good waveforms without overloading the driver. A 5V tolerant 3.3V logic gate, e.g. from 74LVC family would be the optimal solution for 5V to 3.3V level translation.