Texas Instruments LM5070MTC-80

Overview

LM5070MTC-80 from Texas Instruments is an IEEE 802.3af-compliant Power over Ethernet (PoE) Powered Device (PD) interface and current-mode PWM controller with integrated 80 V, 1 Ω, 400 mA MOSFET. It delivers inrush current limiting, signature detection, classification, programmable UVLO, and supports isolated/non-isolated DC-DC topologies including Flyback and Forward for VoIP phones and IP cameras.

For engineers reviewing the LM5070MTC-80 datasheet, LM5070MTC-80 pinout, LM5070MTC-80 application, or LM5070MTC-80 equivalent, key selection criteria include its -80 suffix 80% max duty cycle with slope compensation, TSSOP-16 package, 200 kHz default oscillator frequency, 390 mA default inrush current limit, and integrated high-voltage startup regulator enabling direct 75 V input operation.

Technical Context

The LM5070MTC-80 implements a fully autonomous PoE PD interface with three-phase sequencing: detection (1.8–10 V), classification (12.5–20.5 V), and powered operation (>23 V). Its internal 80 V MOSFET handles line connection switching, while the current-mode PWM controller features cycle-by-cycle current limiting at 0.5 V CS threshold and 55 ns leading-edge blanking.

It integrates dual regulation paths: a high-voltage startup regulator (7.8 V VCC output, 15 mA current limit) and SMPS control with error amplifier (1.25 V reference), soft-start (10 µA current source), and RT-programmable oscillator (175–225 kHz for -80 variant). Slope compensation is active only on the -80 suffix device to stabilize >50% duty cycles.

Key Specifications

Pinout & Package

TSSOP-16 package (Package Number PW), thermally enhanced with exposed pad bonded to VEE for low θJA (125 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM5071MTC-80 and LT4275AIMSE#TRPBF, the LM5070MTC-80 uniquely integrates both IEEE 802.3af PD interface and current-mode PWM controller in one TSSOP-16 package - reducing system complexity for ≤13 W PoE devices without synchronous rectification needs.

Availability

LM5070MTC-80 is available at Aetrix Electronics and suitable for VoIP phones, IP security cameras, wireless access points, and networked sensors requiring stable component supply and full IEEE 802.3af compliance.

Supply support for LM5070MTC-80 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 LM5070 product line was designed specifically for single-chip IEEE 802.3af Powered Device implementations - integrating PoE interface logic, power switch, and current-mode PWM controller to minimize external components and accelerate time-to-market.

FAQ

What is the maximum input voltage supported by the LM5070MTC-80?

The LM5070MTC-80 supports an absolute maximum VIN-to-VEE voltage of 80 V and an operating range of 1.8 V to 75 V. This allows direct connection to PoE lines with margin for transients and compatibility with legacy PSEs. The internal 80 V MOSFET and high-voltage startup regulator are rated for this full range, with derating applied below –40 °C per datasheet specifications.

Does the LM5070MTC-80 require an external MOSFET for PoE operation?

No, the LM5070MTC-80 integrates an 80 V, 1 Ω, 400 mA MOSFET, enabling self-contained PoE interface operation for PDs up to approximately 13 W. An external MOSFET is only required for higher-power applications or when lower RDS(ON) is needed. The OUT pin provides 800 mA peak gate drive for controlling external switches in more demanding designs.

How does the LM5070MTC-80 implement IEEE 802.3af signature detection?

The LM5070MTC-80 implements signature detection by enabling a 25 kΩ resistor between VIN and RSIG when VIN exceeds 1.5 V - producing a 23.75–26.25 kΩ impedance detectable by the PSE. The device draws less than 10 µA during detection mode and disables the signature resistor above 11 V to reduce power loss. This behavior is fully compliant with IEEE 802.3af Section 15.3.1.

What is the purpose of the RCLP pin on the LM5070MTC-80?

The RCLP pin on the LM5070MTC-80 programs the inrush current limit during capacitor charging - critical for meeting IEEE 802.3af's 75 ms charge time requirement. With RCLP open, the device defaults to 390 mA. A resistor from RCLP to VEE sets values from 75 mA to 390 mA, allowing adaptation to legacy PSEs with limited current capacity. This function is active only during initial startup, not steady-state operation.

Can the LM5070MTC-80 be used in non-isolated DC-DC converter designs?

Yes, the LM5070MTC-80 supports both isolated and non-isolated topologies. Its internal error amplifier has a 1.25 V reference and FB/COMP pins configured for direct feedback in non-isolated Buck or Buck-derived designs. The COMP pin includes a 5 kΩ internal pull-up, simplifying connections to voltage dividers without external biasing - making it suitable for cost-sensitive, space-constrained applications like PoE-powered IoT nodes.