Why would this design (Si8261BCC-IS) blow the chip?
I think the troublesome part of the circuit is this:



simulate this circuit &ndash; Schematic created using CircuitLab
When the PMOS inside the Si8261 switches on, it connects 24 V across R2 (4.7 ohm) and the 12 V zener diode. So in theory, that means there would be about 12 V across R2 so 12 V / 4.7 ohm = 2.55 A wants to flow. That's much more than that poor PMOS can handle. Check the datasheet to see what it can actually handle.
Even if the PMOS could handle the current, R2 and the zener diode would blow up eventually due to excess power dissipation (the zener and R2 each get: 12 V * 2.55 A = 30 W OUCH!!! the magic smoke will escape in a nano second)
I would give R2 a significantly higher value in the order of 1 kohm or more. Then calculate the maximum current that can flow through R2 and make sure the power dissipation ratings of R2 and D1 are not exceeded. Of course the current must be within the range that the Si8261's internal PMOS can handle.