The MAX5980 from Maxim Integrated (now part of Analog Devices) is a complete four-port engine for the source side of Power-over-Ethernet. For each of its four ports it runs the full IEEE sequence - detect a valid powered device (PD), classify its power class, then turn the port on through an external MOSFET while limiting inrush - and it monitors current and voltage continuously, removing power when a load disconnects. The MAX5980 is IEEE 802.3at (PoE+) and 802.3af (PoE) compliant. MAX5980GTJ+T is the RoHS ("+"), tape-and-reel ("T") option in the 32-pin TQFN (5 mm x 5 mm).

Operation is flexible. The part can run fully automatically - powered up in auto mode it detects, classifies and powers PDs with no host - or it can be driven entirely from software over the I²C-compatible bus (SCL, SDAIN, SDAOUT) with four address pins (A0-A3) letting up to sixteen devices share one bus and an open-drain INT interrupt flagging events. Pin straps (AUTO, MIDSPAN, EN_CL5) set the default behavior at power-up, which software can then override.

The sensing is built for accuracy and high power. Each port measures current as the drop across an external 0.25 Ω resistor (SENSE_/SVEE_ as a Kelvin pair), and a 9-bit ADC reports per-port current and voltage back over I²C for power management and diagnostics. 2-event classification and Class 5 support (via EN_CL5) enable high-power PDs up to roughly 70 W per port, with high-capacitance detection for legacy devices and DC load-removal detection. The controller drives external MOSFETs through GATE1-GATE4 and operates over -40 °C to +105 °C.

Note: Values are taken from the Maxim MAX5980 datasheet. Confirm every parameter against the latest official documentation before committing a design.

MAX5980GTJ+T ships in the 32-pin TQFN (5 mm x 5 mm, with exposed pad; package outline 21-0140) - a leadless package that puts a full four-port PSE controller in a small area on a switch or injector board. The exposed pad connects to V_EE and must be soldered to the V_EE plane. The device handles gate-drive, sense and monitoring; the port power flows in the external MOSFETs and sense resistors, so layout is the design: Kelvin-connect each SENSE_/SVEE_ pair, keep GATE traces short, route the high-voltage VEE/OUT nodes with clearance, and bypass VEE and VDD as the datasheet specifies. The package image is shown below.

The 32-pin TQFN groups four port channels with the shared supply, interface and control pins (per the MAX5980 datasheet):

• Pins 26, 23, 20, 17 - OUT1...OUT4: Per-port output-voltage sense; connect to each port output.
• Pins 25, 22, 19, 16 - GATE1...GATE4: Per-port external-MOSFET gate drivers.
• Pins 24, 21, 18, 15 - SENSE1...SENSE4: Per-port current-sense positive input; 0.25 Ω to SVEE_, Kelvin.
• Pins 28, 10 - SVEE1, SVEE2: Sense-negative for ports 1/2 and 3/4 respectively.
• Pin 1 - SCL, Pin 3 - SDAIN, Pin 2 - SDAOUT: I²C-compatible serial clock and data in/out. Pin 32 - INT̅: open-drain interrupt.
• Pins 5-8 - A0...A3: I²C slave-address bits (up to 16 devices on one bus).
• Pin 4 - EN: Enable. Pin 29 - EN_CL5: Class 5 enable. Pin 30 - AUTO: auto/shutdown default. Pin 31 - MIDSPAN: midspan collision-avoidance.
• Pin 11 - V_EE: Analog low-side supply (most-negative). Pin 12 - V_DD: Digital high-side (internal). Pin 14 - AGND, Pin 9 - DGND: Analog / digital grounds.
• Pins 13, 27 - N.C.  |  EP - Exposed Pad: connect to V_EE.

The closest options are Maxim's other PoE PSE and power-management controllers. Match port count, IEEE class and interface to your system before substituting.

Selection Tips: Stay with the MAX5980 for a four-port 802.3at/af PSE with I²C monitoring in a compact TQFN; the MAX5945 is a related quad PSE in SSOP. Step to the MAX5970 for I²C hot-swap monitoring, or look at the MAX5971/MAX5974 on the PD/conversion side of the PoE link.

Maxim Integrated, now part of Analog Devices, Inc. (ADI), built the MAX5980 for the source side of Power-over-Ethernet, where a switch or injector must detect, classify and safely power four ports to the IEEE 802.3at/af rules while reporting back over a managed bus.

ADI maintains the datasheet, the full I²C register map, and the sense-resistor and MOSFET selection guidance for the part - the documentation that turns four external MOSFETs and sense resistors into a compliant, monitored quad-port PSE.