voltage level translator for spartan 3e fpga

[bhaskarbhomia]

hi
i need to interface spartan 3e fpga(xc3s500e) with p18f452 micro controller.
the voltage levels and current ratings of both the devices are 3.3v,12mA and 5v,200mA respectively.
for converting 5v to 3.3 i have used a voltage divider circuit but i am not able to find a way to shift 3.3v to 5v. plz help!!

 

[scanman]

Hi,

I have used these comparators to do this with great results.
They will operate from single 5V supply.

http://cds.linear.com/docs/Datasheet/17201fc.pdf

Set input bias of negative inputs to +1.67V for LVTTL 3.3V
Apply incoming 3.3V signal to positive inputs.

scanman

 

[bhaskarbhomia]

hi scanman,
thanks for the help! just one more thing to ask. i studied in the data sheets which say that we should use voltage level translators like SN74LVC2G34. i want to know which one is the better approach!

 

[Electro_Nic]

definitly level translators... these chips are pretty much made for this purpose.
here is everything that you might want to know about these : https://focus.ti.com/lit/an/scea035a/scea035a.pdf

there's some other interesting ways of interacting between two levels, such as the translators for I2C or SPI interfaces... this is very specific though, but still interesting to keep in mind for the future: check this out https://www.kip.uni-heidelberg.de/lhcb/Publications/external/AN97055.pdf

hope this helps

 

[scanman]

hi scanman,
thanks for the help! just one more thing to ask. i studied in the data sheets which say that we should use voltage level translators like SN74LVC2G34. i want to know which one is the better approach!

Data sheet for SN74LVC2G34 page 3 "Vcc = 4.5 V to 5.5 V" High level input voltage = 0.7 x Vcc = 0.7 x 5.0 = 3.5V
This will not translate LVTTL to 5V TTL.

This online tool may help:
**broken link removed**

scanman