Pololu Robotics & Electronics
My account Comments or questions? About Pololu Contact Ordering information Distributors

Pololu Forum

Logic Level Shifter, 4-Channel, Bidirectional Polulu 2595


I want to use this to convert 5V Digital Signal from a DAQ to 3.3V to an Microcontroller. My question is can I make it unidirectional? If yes, how?
I have pretty much an idea but I want to confirm.

Thank you



Is there a specific reason the bidirectionality is an issue for you? If you really only want signals to propagate in one direction, you could add a diode.



Hi Tony,

Yes it should be unidirectional only. The DAQ is an Digital output port and it will be triggered only when its required. And we do not want only backdriving on the DAQ.

So even if I want to propagate in just one direction I need to power up both 3.3V and 5V? Where exactly do I need to add an diode?

Thank you


Yes, you will need to supply power to both the HV and LV pins on the level shifter. There is not really a concern of the level shifter backdriving your DAQ pin. If one side of the level shifter is driven low, it will drive the other side low as well, but otherwise both sides are just pulled up to their respective supply voltages through resistors. So the level shifter does not backdrive any more than a direct connection would (less actually), and if the 3.3V side is never driven, backdriving should not be an issue. If you still want to add a diode to be extra sure, it should go between the level shifter and the output of your DAQ.