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Hi,
I have a MCU board that have ATMEGA368PB and is powered through Si-3402-B PoE controller over PoE. It is driving 2 single-color LED strips (usually white) and 2 individually addressable RGB LED strips. These LED strips are all powered by separate auxiliary power supplies, not by PoE.
The RGB strips’ power supply is connected via B/GND, which is connected directly to the strip’s power pins. The data pin is connected through a differential signal IC.
The white strips’ power supply is connected to A/AGND. A is connected directly to the strips’ V+ rail. AGND is connected to the strips’ V- rails via 2 power MOSFETs (1 per strip) (U$2, U$4). The MOSFETs’ gate pins are connected directly to the ATMEGA328PB via the shield headers.
The issue is after my house experiences a power loss, when power is restored to the house, sometimes U$2 and U$4 on the circuit are switched on, overheat, and eventually melt/fail. It cannot reproduce this by switching panel breakers on/off. It only occurs when the main power to the house is lost and then restored.
The PoE switch does not provide power right away, so the only power is the 24v power supply connected to A/AGND. Following are the two MOSFETs:
I think here the MOSFET AGND and PD1 will be in the floating state as the PoE switch does not power up immediately but the A1GND and A2GND source is active as it is supplied through separate auxillary supply. Any help or better approach will be appreciated.
