I am presently trouble shooting the cause of LTC3330 faults in my design. I am trying to verify if my circuit design or PCB layout is damaging the LTC3330 or causing excess current leakage. Maybe my handling of the LTC3330 ICs is the cause. Multiple LTC3330s were showing a few mA of current leakage when voltage was applied to the AC 1 and 2 inputs but not the VIN input. The current leakage would increase as voltage was increased. Interestingly, other symptoms in these designs show Vin2 and Vin3 rising well above the expected 4.8V and 4.8V minus a Schottky drop per the datasheet. Vin2 and Vin3 seem to track VIN as it increases. Please note that this is with no load on Vout. This did not happen with every PCB. One showed the failure immediately, another slowly developed into this fault, and another seems okay. Given these symptoms, what are the likely modes of failure? Why would the diodes leak and but not when reverse-biased via the Vin input? I am assuming this may be damage to diode-connected MOSFETs, substrate, parasitic devices, etc. depending on the process of course.
In the past I have damaged the LTC3330 by exceeding the absolute maximum voltage at Vin, but I am curious if there are any other precautions I should take beyond normal ESD and soldering methods. Perhaps I am unintentionally floating pins that could cause damage. Because I only have a few more spare LTC3330s, and given the supply issues, I am trying to be very careful with these ICs.