Other Parts Discussed in Thread: MAX3232
Hi there!
I'm just trying to find the reason for a strange malfunction of MAX3232E on our actual pre-production PCB samples for a new product. The circuit is nothing special - all 5 caps are 100nF MLCC and VCC is 3,2V. It seems to work fine with common USB-to-RS232 adaptors and some computer's RS232 card, but does not work with some other devices. During investigation, I found that the problem occures if a RIN-Pin is driven to a voltage above ~7V. In this case, the DOUT-Pins suddenly change polarity! I did some more tests and measurements with oscilloscope on other devices (same circuitry around the MAX3232) for comparison, whose MAX2323 have another date marking and they did not show that weird behaviour. I also found, that the voltages on the charge pump capacitors of the malfunctioning ICs look very different from the other ICs: even without any load on DOUT pins, there is a continuous square wave signal (300-400 kHz) at both C1 and C2. V+ and V- are looking good (+/- 6V). I don't know where our circuit board assembler got the parts from, but I suspect that the bad ICs are counterfeit parts. Here is a picture of the parts - can someone probably confirm if these are genuine devices or not? 
Thank you!
Thomas
