Sunday, August 23, 2015
DC converter modules using fake LM2596 parts
Kerry Wong recently tested some cheap LM2596 DC buck converter modules, very similar to the ones I purchased off Aliexpress a over a year ago for around 80c ea. One of the comments indicated these actually use clones of the LM2576 re-labeled as 2596. The switching frequency of the LM2576 is around 50KHz, vs 150KHz for the LM2596, making it easy to see the difference on a scope.
I pulled out my DS1054Z, one of the DC buck converter modules that I had previously adjusted for 3.3V output, and connected the input to 5V. Here's the output on pin 2:
Measuring of the 5us scale, two cycles takes about 36us, or 18us per cycle, or 55.5kHz. So the ones I received are fakes. I did test the modules after I received them, and found they are good for about 2A @5V with 12V in, so they weren't a total waste of money.
The latest "LM2596" modules I've seen online clearly do not use a real or even fake 2496. The SOIC-8 part appears to be a MPS MP1584. With a switching frequency of up to 1.5Mhz and a smaller form factor, the modules look like a reasonable value at 42c ea, even though they're falsely advertised as LM2596. Strangely, some sellers correctly advertise the same modules as MP1584 converters, but at several times the price.