Level shifters for tinyfpga A2


#1

What level shifters are needed to convert from 5.v to 3.3v ?

for example on a propeller a simple 1k resistor is needed (the diode is inside the propeller)

is it sufficient for a tinyfpga A2 ?

or do I need some specific chips… ?

among the idea:

  • drive an apple Disk II drive by a tinyfpga A2
  • convert V/HS 20 Khz into a VGA signal

#2

Driving the TTL logic with 3.3 volts should be fine.

However I don’t believe using a series resistor on the input will protect the FPGA from 5v input. Instead I recommend using a voltage divider. It requires 2 resistors and will bring the voltage down to 3.3 volts.

Here’s a related stack exchange post that has some good details on what can happen if you use a single resistor: https://electronics.stackexchange.com/questions/106849/using-single-resistor-to-receive-5v-signal-on-the-3-3v-rated-pin

Sparkfun has a decent tutorial on the basics of voltage dividers: https://learn.sparkfun.com/tutorials/voltage-dividers. It will tell you the basic idea of a voltage divider and how it works, but it won’t help you size the resistors. For that, take a look at the following stack exchange post: https://electronics.stackexchange.com/questions/231616/can-i-use-a-voltage-divider-for-shifing-logic-levels