Texas Instruments LM5071MTX-80/NOPB

Overview

LM5071MTX-80/NOPB from Texas Instruments is a Power over Ethernet (PoE) Powered Device (PD) controller with integrated 80 V, 1 Ω, 400 mA internal MOSFET and current-mode PWM controller. It supports IEEE 802.3af compliance, auxiliary AC adapter interface, programmable classification (Class 0–4), and 200 kHz oscillator frequency (RT = 30.3 kΩ). It enables PoE-powered IP phones, wireless access points, and network cameras requiring dual-input power management.

For engineers reviewing the LM5071MTX-80/NOPB datasheet, LM5071MTX-80/NOPB pinout, LM5071MTX-80/NOPB application, or LM5071MTX-80/NOPB equivalent, key selection criteria include PoE signature/classification timing, AUX-enabled UVLO override, 80% max duty cycle with slope compensation, thermal shutdown at 165°C, and TSSOP-16 package compatibility with isolated/non-isolated flyback topologies.

Technical Context

The LM5071MTX-80/NOPB integrates two functional domains: an IEEE 802.3af-compliant PD interface (signature detection, classification, inrush limiting, UVLO with hysteresis) and a current-mode PWM controller (error amplifier, soft-start, cycle-by-cycle current limit at 0.5 V on CS, 80% duty cycle limit with slope compensation). Its internal 80 V MOSFET handles PoE input switching while the auxiliary power enable (AUX) pin allows seamless transition to 12 V AC adapter supply.

Operation follows strict voltage-triggered sequencing: detection begins at VIN ≥ 1.8 V (RSIG active), classification activates at 11.5–25 V (RCLASS current sourced), UVLO release occurs at 25 V (programmable via resistor divider), and full SMPS operation starts after RTN falls below 1.45 V. The -80 suffix denotes inclusion of slope compensation and 80% max duty cycle-critical for stable current-mode control above 50% duty.

Key Specifications

Pinout & Package

TSSOP-16 package (4.4 mm × 5.0 mm, 0.65 mm pitch) with exposed thermal pad; RoHS-compliant, lead-free, and rated for –40°C to +125°C operating junction temperature.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM5072MTX-80/NOPB, LM5071MTX-80/NOPB omits the 5 V LDO but retains identical PoE interface timing, classification accuracy, and PWM control fidelity. Against TPS23753APWR, it adds critical AUX-driven dual-input support and built-in slope compensation - enabling robust operation across PoE voltage sags and auxiliary fallback scenarios without design compromises.

Availability

LM5071MTX-80/NOPB is available at Aetrix Electronics and suitable for IP telephony endpoints, wireless access points, network video cameras, and industrial IoT gateways requiring stable component supply with guaranteed long-term sourcing.

Supply support for LM5071MTX-80/NOPB 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 leader delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and communications markets.

The LM5071 product line delivers integrated PoE PD controllers with auxiliary power interface and current-mode PWM - designed specifically for dual-input, IEEE 802.3af-compliant powered devices in space-constrained networking equipment.

FAQ

What is the primary function of the LM5071MTX-80/NOPB in a PoE-powered device?

The LM5071MTX-80/NOPB serves as a complete IEEE 802.3af-compliant Powered Device (PD) controller with integrated 80 V MOSFET and current-mode PWM controller. It handles signature detection, classification, inrush limiting, UVLO, and SMPS gate drive - enabling single-chip PoE power management for devices like IP phones and wireless access points. Its AUX pin further allows seamless transition to auxiliary 12 V AC adapter supply when PoE is unavailable, making LM5071MTX-80/NOPB ideal for mission-critical dual-input applications.

How does the LM5071MTX-80/NOPB support IEEE 802.3af compliance?

The LM5071MTX-80/NOPB supports IEEE 802.3af compliance through hardware-enforced signature detection (24.5 kΩ target impedance), programmable classification current (Class 0–4 via RCLASS resistor), inrush current limiting (≤100 mA), and thermal shutdown (165°C). Its internal 80 V MOSFET and precise UVLO thresholds (2.00 V ±50 mV with 10 µA hysteresis) ensure PSE handshake timing and power delivery meet specification requirements. All LM5071MTX-80/NOPB timing parameters - including detection window, classification duration (<75 ms), and power-good assertion - are fully integrated and verified per SNVS409E.

What is the role of the AUX pin on the LM5071MTX-80/NOPB?

The AUX pin on the LM5071MTX-80/NOPB provides a 2.5 V threshold input (±0.1 V) that forces UVLO release and enables full SMPS operation regardless of PoE input voltage - as long as VIN ≥ 9.5 V. This allows immediate activation from a 12 V AC adapter, enabling true dual-input redundancy. An external resistor divider sets the AUX voltage; internal 350 kΩ impedance and 0.5 V hysteresis ensure noise immunity. In designs using LM5071MTX-80/NOPB, the AUX pin eliminates need for external OR-ing controllers or power-path switches during PoE outages.

Does the LM5071MTX-80/NOPB include slope compensation, and why is it important?

Yes, the LM5071MTX-80/NOPB includes integrated slope compensation - a feature exclusive to the -80 suffix variant. Slope compensation adds a controlled ramp to the current-sense signal at the PWM comparator input, preventing subharmonic oscillation in current-mode flyback or forward converters operating above 50% duty cycle. This eliminates need for external compensation networks and ensures stable regulation across wide input/output ranges. Because LM5071MTX-80/NOPB supports up to 80% duty cycle, slope compensation is essential for maintaining loop stability - a key differentiator versus -50 variants or competing controllers lacking this feature.

What package type and thermal specifications apply to the LM5071MTX-80/NOPB?

The LM5071MTX-80/NOPB uses a 16-pin TSSOP package (4.4 mm × 5.0 mm, 0.65 mm pitch) with exposed thermal pad for enhanced heat dissipation. It operates across –40°C to +125°C junction temperature, with thermal shutdown at 165°C (25°C hysteresis). Its θ_JA is 125°C/W in standard PCB layout. The package is RoHS-compliant and lead-free, qualified per JEDEC J-STD-020 moisture sensitivity level 3. These specifications make LM5071MTX-80/NOPB suitable for enclosed, fanless networking equipment where thermal margin is constrained.