STA326 Thermal Pad is GND?

[bmclaughlin10]

Posted on June 06, 2013 at 03:39

Is the STA326 thermal pad connected to GND/SUBGND or floating?

Something happened when I installed a heatsink on the STA326 that caused 30V VCC to appear on the 3.3V VDD side, destroying all other components on my board. It seemed to happen right when I connected the STA326 heatsink to my PCB ground plane with screws.

[bosco.stefano]

Posted on June 10, 2013 at 10:32

The thermal pad is connected to pin GND SUB (pin 1) and can be either left floating or connected to GND.

The only hyoptesis about the problem you are facing is a mechanical short between metallic heatsink and Vcc/Vdd.

Verify the assembly of heatsink and components near it (e.g. decoupling capacitor).