Texas Instruments LM5071EVAL

Overview

LM5071EVAL from Texas Instruments is an evaluation board for the LM5071 Power over Ethernet (PoE) Powered Device controller, integrating IEEE 802.3af interface logic, 80V/400mA internal MOSFET, current-mode PWM control, auxiliary power enable, and programmable UVLO/classification. It supports flyback and forward DC-DC topologies in VoIP phones, IP cameras, and wireless access points.

For engineers reviewing the LM5071EVAL datasheet, LM5071EVAL pinout, LM5071EVAL application, or LM5071EVAL equivalent, this page delivers verified functional context, TSSOP-16-compatible layout reference, PoE PD interface timing behavior, auxiliary startup sequencing, and real-world SMPS controller interoperability details - all grounded in TI's SNVS409E design documentation.

Technical Context

The LM5071EVAL implements full IEEE 802.3af detection (1.8–10V), classification (12.5–25V), and powered operation (>25V), with signature resistor disconnect above 11V and programmable classification current via RCLASS pin. Its integrated 80V/1Ω MOSFET enables inrush-limited charging of the SMPS input capacitor before VCC regulation initiates soft-start.

Operation relies on dual power paths: PoE-derived VIN powers the interface and high-voltage regulator (7.8V VCC), while auxiliary AC adapter input (via AUX pin) forces UVLO release below 25V using a 2.5V threshold with 0.5V hysteresis. The current-mode PWM controller features 200 kHz oscillator (RT = 30.3kΩ), 80% max duty cycle (-80 variant), 0.5V CS overcurrent threshold, and slope compensation for >50% duty cycles.

Key Specifications

Availability

LM5071EVAL is available at Aetrix Electronics and suitable for PoE-powered IP cameras, VoIP desk phones, industrial IoT gateways, and networked audio endpoints requiring stable component supply and rapid prototyping validation.

Supply support for LM5071EVAL 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

Texas Instruments is a global semiconductor company specializing in analog, embedded processing, and power management technologies, with leadership in industrial, automotive, and communications infrastructure markets.

The LM5071 product line delivers integrated PoE PD interface + PWM controller functionality for single-chip, cost-optimized, auxiliary-capable powered devices targeting IEEE 802.3af-compliant networking equipment.

FAQ

What is the primary function of the LM5071EVAL evaluation board?

The LM5071EVAL evaluation board demonstrates the complete operation of the LM5071 PoE PD controller IC, including IEEE 802.3af detection, classification, auxiliary power enable, inrush limiting, and current-mode PWM control for flyback/forward DC-DC converters. It provides test points, jumpers, and layout references to validate system-level behavior of the LM5071 in real PoE applications such as IP cameras and VoIP phones.

Does LM5071EVAL support both LM5071-50 and LM5071-80 device variants?

Yes, LM5071EVAL supports both LM5071-50 and LM5071-80 variants. The board accommodates the different maximum duty cycle limits (50% vs. 80%) and slope compensation requirements: the -80 variant includes internal slope compensation for stable current-mode control above 50% duty, while the -50 variant omits it. Oscillator frequency selection (via RT resistor) and soft-start configuration are identical across both variants on LM5071EVAL.

How does the LM5071EVAL handle auxiliary power source handover when PoE is unavailable?

The LM5071EVAL leverages the LM5071's AUX pin to force UVLO release below 25V, enabling immediate activation of the PWM controller when a 9.5–57V AC adapter is connected. A resistor divider sets the AUX threshold to 2.5V with 0.5V hysteresis; once asserted, the LM5071 bypasses PoE detection/classification and directly enables the internal MOSFET and SMPS controller, ensuring uninterrupted operation during PoE loss or absence.

What protection features are implemented and validated on the LM5071EVAL board?

The LM5071EVAL validates multiple integrated protections from the LM5071 IC: cycle-by-cycle current limiting (0.5V CS threshold), thermal shutdown (165°C), UVLO with programmable hysteresis (2.0V reference + 10µA switched current), inrush current limiting (100mA during capacitor charge), and classification current fault detection. These are observable via test points and confirmed through load-step and fault-injection testing per TI's SNVS409E characterization.

Can the LM5071EVAL be used to evaluate non-isolated DC-DC topologies?

Yes, LM5071EVAL supports non-isolated topologies via the LM5071's internal error amplifier and 1.25V FB reference. The board includes FB and COMP test points, allowing direct connection of voltage-divider feedback and loop compensation networks for buck or buck-boost converters. The LM5071's open-drain COMP output with internal 5kΩ pull-up also permits optocoupler-based isolation if needed, but non-isolated configurations are fully validated on LM5071EVAL using the onboard FB scaling resistors.