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I have a 5V TTL which is basically a trigger output that I want to give to an FPGA I/O pin which takes 1.5V, 10mA. What's the best way to do it and what's a quick way to do it ? I was able to look up techniques on converting from 5V to 3.3V but not many on 5V to 1.5V.

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You could use a dual-supply logic level translator if you have a 1.5V supply available and speed is important to you. For example, a 74LVC1T45.

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Just use a resistor potential divider.

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Vout = Vin x \$\dfrac{R_2}{R_1+R_2}\$

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  • \$\begingroup\$ This is the quickest way I could possibly get running. What are the drawbacks of using a potential divider in this case ? \$\endgroup\$ – GamingX Jan 3 '15 at 8:33
  • \$\begingroup\$ Don't use high value resistors if digital speed is high because track capacitance will slow the signal down. Values around 1k are worth a try first and if you have an o-scope then look at the signals to see if lower values are needed. Unlikely to need less than 100 ohms though. \$\endgroup\$ – Andy aka Jan 3 '15 at 10:00

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