Monolithic Power Systems Inc. MP3924GU-P

Overview

MP3924GU-P from Monolithic Power Systems is a quad-port IEEE 802.3af/at Power over Ethernet (PoE) power sourcing equipment (PSE) controller IC. It performs full PoE detection, classification (Classes 0–5), current limiting, disconnected load detection, and thermal protection across four independent ports. Integrated 9-bit ADC monitors port current/voltage, and dual interrupt pins (INT1/INT2) support priority-based fault handling in enterprise switches and midspan injectors.

For engineers reviewing the MP3924GU-P datasheet, MP3924GU-P pinout, MP3924GU-P application, or MP3924GU-P equivalent, this device supports automatic and I²C-programmable operation modes, features isolated three-wire I²C interface, adjustable total power limit via PMAX pin, and QFN-32 (5mm×5mm) packaging for high-density PoE system design.

Technical Context

The MP3924GU-P implements full IEEE 802.3af/at PSE functionality per port-including two-event classification, single/multi-event detection, and foldback current limiting-with independent control of GATE1–GATE4 drivers and SENSE1–SENSE4 inputs using a 0.25Ω sense resistor. Its internal 3.3V VCC regulator powers analog/digital circuitry, eliminating external LDO requirements.

It supports both midspan and endpoint configurations via the MID pin, latches configuration states (AUTO, CLS5, A0–A3) at startup, and provides real-time ADC readouts for voltage (up to 76.65V), current (up to 1.216A), temperature (−40°C to +164.4°C), and PMAX setting (up to 204.8W) with 9-bit resolution.

Key Specifications

Pinout & Package

MP3924GU-P is housed in a thermally enhanced QFN-32 (5mm × 5mm) package with wettable flanks and an exposed thermal pad (Pin 32 is DGND). The package supports reflow soldering per JEDEC J-STD-020 and requires controlled PCB layout for Kelvin sensing and thermal management.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LAN9303-ABZ and LT4275A, MP3924GU-P uniquely combines quad-port 802.3at compliance, integrated 3.3V regulator, PMAX-based system power capping, and isolated three-wire I²C-reducing component count by ≥5 parts versus LT4275A and avoiding fixed 30W/port limits of LAN9303-ABZ.

Availability

MP3924GU-P is available at Aetrix Electronics and suitable for enterprise network switches, midspan PoE injectors, surveillance NVR/DVR systems, and industrial IoT gateways requiring stable component supply, long-lifecycle support, and RoHS-compliant manufacturing.

Supply support for MP3924GU-P 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

Monolithic Power Systems (MPS) is a fabless semiconductor company specializing in high-performance power management ICs, with over 20 years of expertise in DC/DC converters, LED drivers, motor drivers, and PoE solutions.

The MP3924GU-P belongs to MPS's PoE PSE controller product line, designed specifically for high-density, multi-port IEEE 802.3af/at infrastructure equipment where integration, thermal efficiency, and programmable power management are critical.

FAQ

What is the maximum total power limit supported by the MP3924GU-P?

The MP3924GU-P supports a maximum aggregate power limit of 204.8W across all four ports when the PMAX pin is left floating. With a resistor to DGND, it can be set to discrete values such as 49.9W (49.9kΩ) or 120W (120kΩ), enabling precise system-level power budgeting for chassis-based PSE deployments.

Does the MP3924GU-P support IEEE 802.3bt (PoE++)?

No, the MP3924GU-P is certified for IEEE 802.3af (PoE) and 802.3at (PoE+) only, supporting Classes 0–5 up to 30W per port. It does not implement the four-pair power delivery, autoclass, or higher-power signature requirements of 802.3bt, and cannot negotiate with 802.3bt-powered devices.

How does the MP3924GU-P handle disconnected powered devices?

The MP3924GU-P continuously monitors port current decay. When sensed current falls below the programmable DC hold threshold (1.25–2.5mV), it initiates a 300–400ms timer before turning off the associated GATE driver, ensuring clean disconnection without false triggers from transient load dips.

Can the MP3924GU-P operate in both midspan and endpoint modes?

Yes-the MID pin configures operation mode: floating enables midspan mode (2.8s re-detection delay), while connection to DGND disables midspan timing and configures endpoint behavior. This latched setting is sampled at power-on or reset, allowing hardware-selectable deployment topology.

What is the purpose of the CLS5 pin?

The CLS5 pin enables or disables IEEE 802.3at Class 5 detection. When tied to VCC, the MP3924GU-P extends classification current thresholds to support Class 5 (up to 50.5mA), allowing negotiation with higher-power 802.3at Type 2 PDs. Leaving CLS5 unconnected disables Class 5 and restricts operation to Classes 0–4.

Is an external microcontroller required to use the MP3924GU-P?

No-an external microcontroller is optional. The MP3924GU-P operates fully autonomously in automatic mode (AUTO pin floating), executing detection, classification, and power delivery without software. I²C is used only for advanced telemetry, configuration override, or coordinated multi-device sequencing.

What thermal management considerations apply to the QFN-32 package?

The QFN-32 package requires a minimum 120mm² copper pour connected to the exposed thermal pad (Pin 32 = DGND) and ≥4 thermal vias (0.3mm diameter) to inner ground planes. On the EV3924-U-00A board, θJA is 32°C/W; insufficient copper area increases junction temperature and may trigger thermal shutdown above 125°C ambient.