identify chip marking 8KB RX (RX Vertical)

[zoolf]

Hi,
so I try to fix my laptop, when charger is plugged an IC TPS51285a heat up a lot, so I changed it but still same problem, so when I inject 19v 1amps, in the  19v main rail that chip heat up, but when I inject less than 1amps (500mA) the chip is pulsing, i observe it with IR cam it, but I have a 6 pin chip with marking 8KB RX (RX is vertical) heat a little.
can you help me identify this chip?
Attached the Pic