Analog Devices Inc./Maxim Integrated MAX5984DETI+

Overview

MAX5984DETI+ from Maxim Integrated is a single-port IEEE 802.3af/at Power Sourcing Equipment (PSE) controller with integrated 0.5Ω MOSFET and sense resistor, delivering up to 40W per port. It performs automatic PD discovery, classification (including Class 5 and 2-event), DC/AC load-disconnect detection, and supports legacy high-capacitance PDs in industrial PoE injectors and midspan systems.

For engineers reviewing the MAX5984DETI+ datasheet, MAX5984DETI+ pinout, MAX5984DETI+ application, or MAX5984DETI+ equivalent, this page delivers verified functional identity, confirmed 28-pin TQFN-EP package mapping, validated LSCEN-enabled load stability check, exact Class 5 current-limit thresholds (807–998mA), and real-world PoE midspan/end-point deployment context - all extracted from Maxim's official Rev 0 datasheet (12/11).

Technical Context

The MAX5984DETI+ implements fully autonomous PSE control logic without firmware, using analog sensing and state-machine-driven timing for IEEE-compliant detection (two-phase voltage probing), classification (16–20V probe, 5.5–51mA class thresholds), and foldback current limiting (VFLBK_ST = 27V, VFLBK_END = 10V). Its internal DMOS FET (RDS(ON) = 0.5–1.3Ω) and integrated sense resistor eliminate external power components.

It features dual disconnect detection: DC disconnect triggers at 5–10mA load current (IDCTH), while AC disconnect uses OSC-generated triangular wave (3.85–4.2Vpp) and DET current sensing (IACTH = 115–145µA). The LSCEN pin (active-high, internally pulled up) enables load stability checking - a distinguishing feature of the MAX5984D variant versus A/B/C versions.

Key Specifications

Pinout & Package

MAX5984DETI+ is housed in a 28-pin Thin Quad Flat No-lead Exposed Pad (TQFN-EP) package measuring 5mm × 5mm, rated for –40°C to +85°C operation. The exposed pad (EP) must be connected to VEE for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PSE controller applications.

Compared with MAX5984AETI+, the MAX5984DETI+ adds LSCEN-based load stability verification for enhanced reliability in mission-critical PoE links; compared with LT4275AIMSE#PBF, it trades external FET flexibility for lower component count and simplified thermal design in fixed 40W applications.

Availability

MAX5984DETI+ is available at Aetrix Electronics and suitable for industrial PoE midspan injectors, enterprise wireless access points, smart building security panels, and outdoor PTZ camera systems requiring stable component supply and long-term lifecycle support.

Supply support for MAX5984DETI+ 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

Maxim Integrated, now part of Analog Devices, designs precision analog, mixed-signal, and power management ICs for industrial, communications, and computing applications.

The MAX5984 product line delivers fully integrated, software-free IEEE 802.3af/at PSE controllers targeting space-constrained, thermally demanding PoE infrastructure equipment where reliability and BOM reduction are critical.

FAQ

What is the primary function of the LSCEN pin on the MAX5984DETI+?

The LSCEN (Load Stability Check Enable) pin on the MAX5984DETI+ is a digital input that activates dynamic verification of PD load consistency after classification. When left unconnected (internally pulled high), it enables the function; pulling it low disables it. This capability distinguishes the MAX5984DETI+ from earlier variants like MAX5984AETI+ and improves reliability in environments prone to intermittent loads. The MAX5984DETI+ uses this feature to monitor for unexpected load drops that may indicate cable faults or PD disconnection.

How does the MAX5984DETI+ achieve 40W power delivery while remaining compliant with IEEE 802.3at?

The MAX5984DETI+ achieves 40W by enabling Class 5 operation through specific ILIM1/ILIM2 pin configurations (e.g., ILIM1 = VEE, ILIM2 = open yields 807–893mA limit), which exceeds the 802.3at Class 4 maximum of ~30W. It maintains compliance by adhering to all detection, classification, and safety timing requirements - including two-phase voltage probing, 16–20V classification voltage, and foldback current limiting - while extending current thresholds beyond baseline specifications. The MAX5984DETI+ integrates the necessary power FET and sense resistor to sustain this output without external components.

Does the MAX5984DETI+ support both end-point and midspan PSE topologies?

Yes, the MAX5984DETI+ supports both topologies. Midspan operation is enabled by asserting the MIDSPAN pin high before power-up or reset, which configures cadence timing (2.0–2.4s retry delay after failed detection). End-point use requires pulling MIDSPAN low. The device automatically adapts detection timing, voltage slew rates, and disconnect behavior based on this latched setting. This dual-mode capability makes the MAX5984DETI+ suitable for switch-integrated PSEs and standalone PoE injectors alike.

What are the key thermal protection mechanisms built into the MAX5984DETI+?

The MAX5984DETI+ incorporates three thermal protections: junction temperature shutdown at +150°C (TSHD) with 20°C hysteresis (TSHDH), input undervoltage lockout (VEE_UVLO = 28.5V) preventing operation under insufficient supply, and overvoltage lockout (VEE_OV = 62.5V) guarding against input surges. These functions are hardware-based and require no configuration. During thermal shutdown, the device resets and resumes normal operation only after junction temperature falls below +130°C. The MAX5984DETI+'s 29°C/W junction-to-ambient thermal resistance (TQFN package) ensures effective heat dissipation in typical PCB layouts.

Can the MAX5984DETI+ detect and classify legacy 802.3af PDs?

Yes, the MAX5984DETI+ fully supports legacy 802.3af PDs. With the LEGACY pin left unconnected (default high), it enables high-capacitance detection accepting signature capacitances up to 47µF (typ), accommodating aged or long-cable PDs. It performs standard two-point resistance measurement (RDOK = 19–26.5kΩ) and validates open-circuit voltage (30V max), short-circuit current (5mA min), and slew rate (0.1V/µs) per IEEE 802.3af. Classification follows Table 33.9 of 802.3at, ensuring backward compatibility while adding Class 5 capability for newer devices. The MAX5984DETI+ maintains this dual compatibility without configuration changes.