The component is supposed to be TCA9517DGKR, a level-shifting I2C bus repeater from Texas Instruments. I got these soldered from a turn-key Chinese fab. The top markings are TI43 (Or T143?) first line, and AYK second line:
The AYK is the correct chip mark for TCA9517. However the chip doesn't function as it should, whatsoever. When powered up as TCA9517, it clamps SDA and SCL lines. As a stand-alone, DMM shows no connectivity between any pins.
[The original (good) chip has a clear first-line mark as TI 6B]. More, the chip has some bottom thermal slug:
I suspect the chip is some medium-power transistor, but wasn't able to find a match. I have 250 of these suckers, and if someone can identify the chip, maybe I can re-use them in some other projects.