bidirectional level shifter

Thread Starter

mayank rob

Joined Sep 18, 2012
17


hello there
I am trying to implement this bidirectional level shifter.
I am using it on communication line of controller.
the problem i am facing is that instead of 5v signal I am getting only 3.4V signal.
I have checked all the other voltage levels and they are perfectly fine.
Even 5V is proper.
I am using BSN20 n channel mosfet,10k resistors,

Thanks you anyway.
 

Thread Starter

mayank rob

Joined Sep 18, 2012
17
Thank you for reply
Even my initial thought was that....but i checked for it and it isnt the case.
I checked it thoroughly....connection polarity and even voltage supplies.
 

AnalogKid

Joined Aug 1, 2013
10,987
Not really. The 74ACT125 has unidirectional drivers with tri-state enables. That means that with two of them connected back-to-back, you need an external direction signal. The OP wants a circuit that works both ways automatically with no steering logic or direction signal.

ak
 

ronv

Joined Nov 12, 2008
3,770
What is the state of your signals. In other words are they driven high and low or only driven when their output are low and then tri-stated?
 

ronv

Joined Nov 12, 2008
3,770
Try this:
The diodes in series with the signals are just to simulate the tri-state of your signals. D4 is there because the 7002 may still be on a little with 1.5v gate to source. If it isn't the low level on the 3.3 volt side may not go all the way to ground, but be a diode drop (internal diode) from ground.
 

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