Negative voltage from LM2596 DC-DC Ebay module
The ripple is about 120mV, it can be reduced with a filter on the output, I used an inductor series of 1uH and a 220uF capacitor to GND:
The ripple is now reduced by 5 times, around 25mV also with a drain of 500mA.
NOTE: In the inverting regulator mode, the LM2596 needs at least 2A input for a correct bootstrap, see the datasheet for a delayed-startup trick, if you doesn’t have that current.
NOTE2: of course, if wired in inverting mode, the module should be installed isolated from the GND
Hope this helps someone looking an easy and cheap source of negative voltage with good current.