TPS2458: Pin1 impedance to ground

The problem is: if the board is powered off for a night, the tps2458 works abnormal. 

We monitored the Vint(pin1) and SUM12(pin5) by scope and find that if the chips was powered by 3.3V only, the Vint and SUM12 are fluctuated.

And the impedance from Vint to ground is very small(~100ohm), if we reheat the chip, the impedance can back to normal(200+k ohm).

if the TPS2458 are powered for 10 mins or more, the vint have a good voltage level around 2.33V ,but the Vsum12 has voltage of 500mV-1V while at that time 12V power is completed off.

Thanks for reaching out... 

I will get back to you by Monday.

It looks like very strange to me. Is this issue repeatable on the different PCBs populated with different samples of TPS2458?

No, only happens on a PCB.  We manually soldered the chip for several times. The chips could worked good after chip was soldered for some time, maybe several hours, or 2 days.

But after power-down for a period, somehow TPS2458 may behave very strange, especially the SUM12 pin may go to very high, even without 12V power.

We've placed order for new TPS2458 for replacement, it will take 2 weeks.

Will report back if any progress