Dual-channel PoE PD with integrated DC/DC
The PM8805TR from STMicroelectronics is a dual-channel Power-over-Ethernet Powered Device controller with an integrated DC/DC converter, supporting the 802.3bt standard up to 99.9 W while remaining backward-compatible with 802.3at (PoE+) and 802.3af (PoE). The input voltage range of 9 V to 57 V covers the full PoE bus, from legacy 48 V systems to the higher-voltage 802.3bt PSE outputs, and the internal switches eliminate the need for an external hot-swap FET in most designs.
43-VFQFN exposed-pad — thermal and layout demands
Housed in a 43-VFQFN with an exposed pad (8x8 mm body, 0.50 mm pitch), the PM8805TR requires a thermal via array under the pad to sink heat from the integrated DC/DC switches — the pad is the primary thermal path, not the leads. Surface-mount assembly on a standard FR-4 board is straightforward, but the exposed pad footprint demands a solder-paste stencil aperture that covers 50-70% of the pad area to avoid voiding and ensure the thermal resistance stays within the datasheet RthJA.
Active production, ROHS3 — no LTB pressure
The 15 µA quiescent supply current means the controller itself draws negligible power in standby — relevant for always-on PD applications where every milliwatt counts against the PoE class budget.
Industrial temperature, not automotive
Rated for -40°C to 85°C ambient, the PM8805TR suits industrial PoE endpoints (IP cameras, wireless APs, IoT gateways) but lacks AEC-Q100 qualification — not intended for under-hood or chassis-mounted automotive PD designs. Two independent channels allow the controller to negotiate power on both Ethernet pairs simultaneously, drawing up to 99.9 W total — enough for pan-tilt-zoom cameras or multi-radio access points that exceed the 25.5 W limit of 802.3at single-channel.