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Altera_Forum's avatar
Altera_Forum
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16 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
16 years ago

74LVC is a "3.3V node" logic, so it's not suited for 3.3V to 5V translation, but it's good for the 5V to 3.3V direction, as I previously stated. It surely works for the 8 MHz speed required with ADS7861 (and a lot more).

I verified, that ADS7861 has a 5V CMOS level specification (VIH > 3.5V) so it can't be reliably driven by DE2 3.3V logic outputs. A 5V logic IC with TTL level specification (VIH > 2.0 V) can perform the conversion. 74HCT244 would be suitable 3.3 to 5V translator (or 74HCT04 for inverted signals).