Counterfeit 3045 low noise LDOs from eBay

   

    Sometimes lazyness gets the better of me and I tend to look for an easy way out or an easy fix to stuff. Buying ready-made boards from eBay is one such way, but in this case, it ended biting me in the ass.

   I have a project where I want to have some voltage references and other sensitive experiments into an enclosure and also have a really low noise  LDO to power them, in the same enclosure as the rest. I thought that some LT3042/3045 would be ideal. Instead of making my own boards, I thought why not buy some ready-made ones from eBay

                                                    My future-to-be experiment

   So I bought two different boards. One is a really crappy looking one with what can only be desribed as the world's crustyest capacitor. Fun fact.... the blue cathode markers on the rectifier diodes is actually done with a marker or sharpie. How do I know? The marks disappearead after I put a bit of alcohol to wipe away some rosin on the board  :|  

LT3042 board

       Crappy looking input capacitor. It's light as a feather and came already swollen. 

   Crappy looks aside, the LT3042 on this board looks genuine. It has the right markings on the case "LTGSH", which according to the Datasheet , is the right one for the MSOP package. 

OK, so far so good...

   But I needed another LDO. And I wanted another design, just so I can, at some point, try to measure their noise against a real LT3042 board  (which would be designed by me, but somewhere in the future,  or so I thought) and see which one (mine, of course) would come out on top as having the lowest noise.

   I give you specimen no.2, which, after making its way from Saudi Arabia, of all places, it ended up under my attentive (not really) gaze.

 At first glance, looks legit and much cleaner layout that the previous dog's breakfast. But unfortunately the devil is in the details....

                                                        LT3045 board AKA specimen no.2

    On attentively looking at the LT3045 Datasheet  we see that there are two variants of the chip....one with 10 pins in a DFN package and another with 12 pins in an MSOP package. But someone in China was thinking, and, as you can see from the above picture, they decided to do away with LT's wasteful marketing B.S. and just have a  DSN package with all 12 pins on it. Brilliant! 

  Only thing is, I actaully wanted an LDO that really is low noise and something tells me this one is not it.

   I am working on an LNA set-up to measure voltage reference noise and will also try to measure the noise of these boards and compare them to one I will design myself, because there's really no other way to ensure I really have the expected performance.

 

   Bottom line is, when it comes to these low-noise LDOs, 75 percent of the performance is actually in the board design and I am highly doubtful that the ones on sale on eBay are actually designed by someone that gave a sh$%^t about "low-noise". The other 25 percent is actually getting a chip that is the real deal. So just be careful what you buy and hopefully I made you wary enough so that you don't waste your money on useless junk.

Hope you found this info useful. 

Have fun with your projects