Monolithic Power Systems Inc. EV3908+8001-00A

Overview

EV3908+8001-00A from Monolithic Power Systems is an IEEE 802.3af-compliant Power over Ethernet (PoE) Powered Device (PD) evaluation board integrating MP3908DK (synchronous PWM controller) and MP8001DS (PD interface controller). It supports 40–57V PoE input, delivers 5V/2.6A output via external 13W flyback converter, and implements detection, classification, programmable inrush current limit, thermal protection, and power-good signaling. It is used to validate PoE-powered VoIP phones and security cameras.

For engineers reviewing the EV3908+8001-00A datasheet, EV3908+8001-00A pinout, EV3908+8001-00A application, or EV3908+8001-00A equivalent, this board enables rapid functional verification of IEEE 802.3af PD compliance, inrush control behavior, classification signature accuracy, and synchronous rectification performance under real PSE negotiation conditions.

Technical Context

The board implements full IEEE 802.3af Type 1 PD functionality using MP8001DS for signature detection (25kΩ resistor + 120nF capacitor), 3-event classification (Class 3, 15.4W), and integrated 100V/0.8Ω DMOS switch with 450mA temperature-compensated current limit. It uses open-drain PG signal to indicate stable 5V output.

MP3908DK provides constant-frequency (250kHz) current-mode control with soft-start, slope compensation, and peak current limiting to drive the external flyback transformer (Coilcraft POE13P-33L). Synchronous rectification is implemented via Si7386DP-T1-E3 MOSFET controlled by MP3908DK's gate driver outputs.

Key Specifications

Availability

EV3908+8001-00A is available at Aetrix Electronics and suitable for PoE-powered VoIP telephones, network-attached security camera systems, and remote industrial sensor nodes requiring stable component supply and fast design validation cycles.

Supply support for EV3908+8001-00A 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 analog and power ICs, with core expertise in DC/DC conversion, LED drivers, motor drivers, and PoE solutions.

This evaluation board belongs to MPS's PoE PD reference design portfolio, developed to accelerate customer adoption of IEEE 802.3af-compliant powered devices through fully validated hardware, schematics, and test reports.

FAQ

What is the purpose of the two RJ-45 connectors (J1 and J2) on EV3908+8001-00A?

J1 is the primary Ethernet interface for PoE input from a PSE; it routes power and data to the PD front-end circuitry. J2 is a secondary RJ-45 jack wired as a pass-through for Ethernet data only-enabling daisy-chaining or data loop-through without interrupting upstream connectivity while validating PD functionality.

Can EV3908+8001-00A operate without an external flyback transformer?

No. The board requires the external Coilcraft POE13P-33L transformer (listed in BOM) to complete the isolated 5V/2.6A flyback power stage. MP3908DK drives the primary side, and Si7386DP-T1-E3 handles synchronous rectification on the secondary side-neither function operates without the transformer.

How is IEEE 802.3af classification implemented on this board?

Classification is performed by MP8001DS, which sources a precise 10–20 mA current pulse across the classification resistor network (R12, R13, R14, R15, R16) during the PSE's classification phase. This generates a Class 3 signature (15.4W) compliant with Clause 14.2.2.1, verified by the board's schematic and BOM resistor values.

Does EV3908+8001-00A support IEEE 802.3at (PoE+) or 802.3bt?

No. The board implements only IEEE 802.3af (Type 1) functionality. MP8001DS is an 802.3af-specific controller and lacks the higher-power classification modes, dual-event detection, or 4-pair negotiation required for 802.3at or 802.3bt compliance.

What is the role of the TLV431A (U9) on the board?

TLV431A serves as a precision 1.24V reference and error amplifier in the feedback loop of the external flyback converter. It compares the scaled 5V output against its internal reference and drives the optocoupler (PC817B) to regulate MP3908DK's duty cycle-ensuring tight ±3% output voltage regulation under varying load and line conditions.

Is thermal protection active during both PoE and external DC operation?

Yes. MP8001DS integrates thermal shutdown that disables the PD interface when die temperature exceeds 150°C, regardless of power source. This protection remains active during both PoE input (via J1) and external 40–57V DC supply (applied to VDD/VSS pins), ensuring safe operation across all input configurations.