We have a new board using PTD08D210WAC power modules (five per board).
We are finding that a very high percentage of these are failing and showing 1-2 ohm shorts when assembled (and continue to do so when removed). This on boards that have never been powered up or programmed, and thus should not have encountered a loop instability or other high current condition due to programming.
On one board, some of the modules do show a high resistance (10K+ ) in line with the output impedance of the data sheet, and these have been configured to work just fine.
On that same board however, one module shows a 2 ohm short and starts up for ~1ms then signals a FLT flag and is shutdown by the controller.
Having read of others with problems with similar modules, and seeing they updated datasheets for other bricks to say 'one reflow pass' only. I need to ask - is there a similar known vulnerability in the PTD08D210WAC ?
If not a reflow issue, is there any other known reason why a module would be reporting 1-2 ohms between VOUT and GND ? On some modules this affects both rails, but on others it affects just one half of the module, the other rail runs ok.
For reference, the loads are in the 1-5 Amp range typically, one as low as 0.25A. We're starting from a VC709 Xilinx reference design and power design xml file, with some modifications for our target voltages.
I'd appreciate any help / insights - this is becoming a concern to have such a high part failure rate.
