STMicroelectronics PM8805TR

Overview

PM8805TR from STMicroelectronics is a system-in-package IEEE 802.3bt/at/af PoE-PD interface IC integrating dual active bridges, a 100 V/0.1 Ω high-side hot-swap MOSFET, and a single-signature classification engine - delivering up to 99.9 W input power handling for 4-pair PoE applications in security cameras and wireless access points.

For engineers reviewing the PM8805TR datasheet, PM8805TR pinout, PM8805TR application, or PM8805TR equivalent, key selection considerations include its dual-bridge R_DS(on) (90–150 mΩ), programmable 3.3 ms classification delay, T0/T1/T2 PSE-type identification outputs, PGD-controlled DC-DC enable timing, and thermal shutdown at 160 °C with 30 °C hysteresis.

Technical Context

The PM8805TR implements two independent active bridges (IN12/IN36/GND12/GND36 and IN45/IN78/GND45/GND78) with integrated gate drivers and charge pump (VCP output: 6.8–9.8 V), enabling full 4-pair rectification with ≤30% bridge-to-bridge resistance unbalance. Each bridge supports 1 A continuous input current and features ZCD comparators (10 mV threshold, 5–15 μs delay) for synchronous rectification control.

Its PoE-PD interface performs IEEE 802.3bt-compliant detection (26.1 kΩ signature), classification (programmable CLS1/CLS2 with 3.3 ms activation), and PSE type identification via three open-drain T0/T1/T2 signals. The device supports auxiliary power prioritization (RAUX/FAUX pins), MPS current modes (10–22 mA), and dual-level overcurrent protection (1 ms DC + 10 μs short-circuit).

Key Specifications

Pinout & Package

PM8805TR uses a VFQFPN43 (7 × 7 mm, 0.5 mm pitch) package with six exposed thermal pads (EP1–EP6) electrically tied to bridge low-side drains (EP1–EP4), VOB (EP5), and hot-swap drain (EP6) - requiring direct PCB copper plane connection for thermal management (R_THJA = 30 °C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PoE-PD interface applications.

Compared with MAX5984DETE+T and LT4295IUFD#PBF, the PM8805TR uniquely integrates dual bridges, hot-swap MOSFET, and PSE-type telemetry in one VFQFPN43 package - reducing component count by ≥12 devices while enabling deterministic 4-pair power delivery and real-time PSE classification feedback.

Availability

PM8805TR is available at Aetrix Electronics and suitable for high-power security cameras, enterprise wireless access points, public information displays, and PoE lighting systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for PM8805TR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The PM8805TR belongs to ST's PoE-PD system-in-package product line, engineered specifically to simplify high-power IEEE 802.3bt-compliant powered device designs by integrating rectification, classification, hot-swap control, and telemetry into a single thermally optimized package.

FAQ

What is the maximum continuous output current supported at the VOUT pin?

The PM8805TR supports up to 3.0 A continuous current at the VOUT pin under recommended operating conditions (TA ≤ 85 °C, proper PCB thermal design). This rating assumes use of all six exposed pads (EP1–EP6) connected to adequate copper planes, as specified in the thermal data section of DS12813 Rev 3 - where maximum power dissipation is calculated at 1.3 W.

How does the PM8805TR handle auxiliary power sources alongside PoE?

The PM8805TR uses RAUX and FAUX pins to manage auxiliary power arbitration: RAUX grants priority to an external source connected *after* the hot-swap MOSFET, enabling uninterrupted operation during PoE loss; FAUX forces hot-swap turn-on when VIN drops below UVLO, allowing pre-regulated auxiliary sources (e.g., 12 V wall adapters) to power the system before PoE stabilizes.

Can the PM8805TR be used in 2-pair PoE applications, or is it limited to 4-pair?

Yes, the PM8805TR fully supports both 2-pair and 4-pair configurations. Its dual active bridges can operate independently: IN12/IN36/GND12/GND36 form the first bridge for standard 2-pair operation, while IN45/IN78/GND45/GND78 activate only when 4-pair mode is required. All electrical specs - including R_DS(on), classification, and MPS - remain valid in either topology.

What is the function of the T0, T1, and T2 pins, and how are they decoded?

T0, T1, and T2 are open-drain outputs that encode detected PSE type per Table 2 in DS12813: combinations of asserted (low) and de-asserted (high) states indicate IEEE 802.3bt Type 3/4, Type 2, or legacy af/at PSEs. Each pin must be pulled up to VB (5 V) externally; their logic states are latched after classification and remain stable until next power cycle or reset.