Voltage shifter wrong output voltage

Hello everyone,

I am doing a project that needs to downshift the output voltage of an arduino (I’m using a DUE) from 3.3V to 1.8V (for now but it can change, the final range is between 1.4V and 1.8V).

So I would like to use a voltage shifter, I have a CD4504BE (E4) but when I measure the voltage at the resistors (see attachment) I get something like 1.6/1.7V and that’s not precise enough for my project.

I also tried with VCC = 5V and VDD = 3.3V and same thing, the output voltage is around 3V. The more I lessen the resistor (I tried 2k ohm) the more the voltage difference so it seems to me like a problem of output current.

Is it out of specs or something ? here is the datasheet.

Am I doing something wrong ? Or do can you recommend me a better component for thoses tensions ?

Thank you

The data sheet shows an output voltage within 50 millivolts of the power supply voltage, but the part is not specified for voltages below 5 volts.

There are better parts for this application but you have not specified what you really want to accomplish. I have forgotten the other part numbers but perhaps others reading this article can help.

Thank you for the answer,

Yes I've seen the 50mV but it's more than that even with the 5V/3.3V shift.

I prefered not to enter into details because it's part of a bigger project and it would take some time to explain but the purpose is to use the arduino to send addresses (of like 16 bytes and each pin is a byte) to a matrix but the matrix can only be polarized at 1.8V (I can't change the matrix) think of the matrix as a multiplexer. I'm not sure if I'm clear haha.

Anyway if someone has better parts for this that would be great !

Typical microSD card modules use the 74LVC125A to shift from 5V to 3.3V. But the datasheet suggests it would also do 1.8V. The chip is basically a buffer whose input pins are high-voltage tolerant. The ouput voltage is whatever you power the chip with. Of course this chip only shifts in one direction, not both ways. Also, it looks like the outputs don't really get very close to the rails if there's any current involved. So if you really need 1.8V outputs, you might have to power the chip with 2V or more. But an output low still wouldn't get to ground. That said, the 125A seems to handle SPI traffic pretty well, at high speed. You might find that your CD4504 would work fine even if it doesn't give you output at the rails.

Have you googled?
3.3v to 1.8v level shifter

Have you looked at SN74LV1T34?

Tom... :slight_smile:

Thank you for your answers, I'll look for those !

Anyway I just tried with resistors that mimics the minimum resistance i'll get (I think) but that's only a test.