TI,
I have a TPS65400 EVM, and I was trying to share SW3 and SW4. In the EVM, I tied VOUT3 to VOUT4, and pulled COMP4 to VDDA. The input voltage was 10V.
I modified the feedback resistors of the EVM so that I have a total of three outputs of 3.3V each driving a load of 1 ohm each, from SW1, SW2, and SW34 combined. It was working fine for about 5 minutes and then the shared output of SW3 and SW4 failed.
When I went back to no share mode and removed all the loads, VOUT4 was putting out a sine wave of -5V to +5V, and the SW4 output is ringing from 0 to 10V every 200us. But the SW3 was also working in a funny mode. It put out a correct 3.3V for a few second just after power up, and then it went to 1.6V and was trying to go back to 3.3V every half a second or so.
But then if I went back to sharing SW3 and SW4, the output behaved similar to VOUT3 above, but I can still see SW3 and SW4 putting out a square wave between 0 to 10V, but of course the duty cycle of the square wave is not correct.
VOUT1 and VOUT2 were all working fine all the time.
Obviously the SW3 and SW4 was destroyed in some manner. But I do not understand how they can be destroyed just by going to current sharing mode, and the funny thing is that it can function correctly for a few seconds after I cool it down, so it imight somehow be related to temperature or charged capacitor stored somewhere. I already used the software to set the registers back to the default states.