Texas Instruments LM5071MT-80/NOPB

Overview

LM5071MT-80/NOPB from Texas Instruments is a Power over Ethernet (PoE) Powered Device (PD) controller with integrated 80 V, 1 Ω, 400 mA MOSFET, current-mode PWM control, IEEE 802.3af compliance, auxiliary power enable, and programmable UVLO with hysteresis - used in PoE-powered IP phones, wireless access points, and network cameras.

For engineers reviewing the LM5071MT-80/NOPB datasheet, LM5071MT-80/NOPB pinout, LM5071MT-80/NOPB application, or LM5071MT-80/NOPB equivalent, key selection considerations include PoE interface sequencing, auxiliary adapter coexistence, cycle-by-cycle current limiting at 0.5 V CS threshold, 80% max duty cycle with slope compensation, and TSSOP-16 package thermal performance up to 125°C junction temperature.

Technical Context

The LM5071MT-80/NOPB integrates dual-domain control: a PoE interface engine handling signature detection (1.8–10 V), classification (12.5–25 V), and inrush current limiting (100 mA), plus a current-mode PWM controller with 200 kHz oscillator (RT = 30.3 kΩ), soft-start (10 µA current source), and error amplifier (1.25 V reference, 75 dB DC gain).

Its architecture supports both isolated and non-isolated topologies (e.g., flyback, forward), features automatic power sequencing between PoE interface and SMPS, and includes dedicated circuitry for AUX pin forced startup below UVLO (2.5 V threshold), RTN-based soft-start release (1.45 V), and thermal shutdown at 165°C with 25°C hysteresis.

Key Specifications

Pinout & Package

TSSOP-16 package with 0.65 mm pitch, thermally enhanced pad, and 125°C/W junction-to-ambient thermal resistance - optimized for PoE PD board space constraints and thermal management in sealed enclosures.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM5072MT-80/NOPB, LM5071MT-80/NOPB offers greater flexibility in classification resistor selection and simpler biasing for Class 0; versus TPS23753APWPR, it trades PoE+ capability for integrated AUX control and lower system-level component count in 802.3af deployments.

Availability

LM5071MT-80/NOPB is available at Aetrix Electronics and suitable for IP telephony endpoints, wireless access points, network video cameras, and IoT edge gateways requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for LM5071MT-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 - designed specifically for cost-optimized, space-constrained powered devices needing seamless dual-source operation and full 802.3af compliance.

FAQ

What is the maximum input voltage rating for LM5071MT-80/NOPB?

The LM5071MT-80/NOPB has an absolute maximum VIN-to-VEE rating of 80 V, with operational input voltage specified from 1.8 V to 60 V. This allows safe handling of PoE transients and compatibility with 48 V nominal systems while supporting auxiliary inputs down to 9.5 V via the AUX pin. The internal 80 V MOSFET and UVLO circuitry ensure reliable operation across this full range without external clamping.

How does the LM5071MT-80/NOPB handle power source handover between PoE and auxiliary input?

The LM5071MT-80/NOPB uses its dedicated AUX pin to force UVLO release independently of VIN voltage - enabling immediate activation of the PWM controller when a 12 V wall adapter is connected, even if PoE voltage is absent or below 25 V. This eliminates sequencing delays and ensures uninterrupted operation during source transitions, with no external logic required.

What is the purpose of the ARTN pin on LM5071MT-80/NOPB, and why is it separate from RTN?

The ARTN pin serves as the dedicated analog ground return for sensitive circuits including FB, COMP, CS, and RT - isolating them from high-current SMPS return noise on RTN. This separation prevents coupling of switching transients into the error amplifier and current sense paths, ensuring stable regulation and reliable overcurrent protection. Layout best practice requires star grounding of ARTN near the IC, with single-point tie to RTN.

Can LM5071MT-80/NOPB be used in isolated flyback designs, and how is feedback implemented?

Yes, LM5071MT-80/NOPB supports isolated flyback topologies. In such designs, the internal error amplifier is typically disabled (FB tied to ARTN), and feedback is provided via an optocoupler connected between COMP and ARTN. The internal 5 kΩ pull-up on COMP supplies bias current to the optocoupler transistor, enabling secondary-side regulation without external components - maintaining tight output voltage accuracy across line and load variations.

What distinguishes the LM5071MT-80/NOPB from the -50 variant, and when should each be selected?

The LM5071MT-80/NOPB implements 80% maximum duty cycle with integrated slope compensation for stable current-mode control above 50% duty; the -50 variant caps duty cycle at 50% and omits slope compensation. Select LM5071MT-80/NOPB for flyback converters requiring high step-down ratios (e.g., 48 V to 5 V), and LM5071MT-50/NOPB for forward or push-pull topologies where duty cycle is inherently limited and slope compensation is unnecessary.