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Voltage issues with Logic Level Shifter, 4-Channel

We are trying to use this product:

I’ve bought about 10 of these for testing, but several shifters show strange problems. Basically, there is non-infinite resistance across pins of converters that we’ve connected, and when connecting LV to 3.3v and HV to 5V the following is seen:

  • LV pins have high voltage (up to 3.8-4.5v)
  • HV pins show <5V (4-4.5V)

If we solder pins to a brand new converter it firstly works fine, but later starts behaving incorrectly. Have we burned them? Is it related to soldering, shorting or something else?

(right two have been resoldered multiple time)



HV to H4 shorted:



Normal behaviour:

HV to LV shorted


Normal behaviour:

We have already burned several Teensy 4.1 boards with these level shifters, so any help is appreciated.

I have only 6 converters left, so any additional testing should be cautious.

Hi.

Some of the solder joints do look like they could use more solder, but if the boards were working and then stopped, I think it is unlikely the soldering is the issue. Could you post pictures that show how the level shifters are connected in your setup? What are you using to supply power to the LV and HV pins? What was connected to L1-4 and H1-4?

-Claire

As the board’s schematic shows, there is a 10k resistor between each Lx pin and LV and between each Hx pin and HV:

So you should measure 10k of resistance between each pin and its respective supply. In cases where you see an open circuit, that could actually indicate that a solder connection is bad or your multimeter probes aren’t making proper contact. (I am not sure why you are seeing 2.9k and 5.7k, though; that might indicate the boards are damaged somehow.)

Kevin

Hi kevin, thanks for reply.

It has nothing to do with soldering as even after unsoldering all pins it shows the same values.

Yeah, it looks like EVERY board is somehow damaged, we literally don’t believe these convertors are useable. There is no single board that shows 10k on all contact, at least some contacts on each board show some random values (and it’s not multimeter probes issue - “broken” contacts always show the same resistance).

Is there any kind of support I can get from Pololu? Either all convertors that I’ve got are somehow broken (and I would really love to see replacement) or I am doing something wrongly (which is not really possible as I don’t even apply any current to them, don’t overheat them and so on).

Since the level shifters worked in your system at first, I am concerned that something in the setup is damaging them. To help you troubleshoot, we need a few questions answered. Could you post pictures that show how the level shifters are connected in your setup? What are you using to supply power to the LV and HV pins? What was connected to L1-4 and H1-4?

-Claire