Texas Instruments LM5070SD-80/NOPB

Overview

LM5070SD-80/NOPB from Texas Instruments is an IEEE 802.3af-compliant Power over Ethernet (PoE) Powered Device (PD) interface and current-mode PWM controller with integrated 80V/400mA MOSFET, 80% maximum duty cycle limit, programmable inrush current (75–390 mA), and 200 kHz oscillator frequency. It enables single-chip PoE PD implementation in VoIP phones, IP cameras, and wireless access points.

For engineers reviewing the LM5070SD-80/NOPB datasheet, LM5070SD-80/NOPB pinout, LM5070SD-80/NOPB application, or LM5070SD-80/NOPB equivalent, key selection criteria include IEEE 802.3af signature/classification compliance, internal MOSFET R_DS(ON) of 2.2 Ω, UVLO programmability with 2.00 V threshold, thermal shutdown at 165 °C, and support for both isolated and non-isolated dc-dc topologies.

Technical Context

The LM5070SD-80/NOPB integrates a full PoE PD interface-including detection (1.8–10 V), classification (12.5–20.5 V), and programmable inrush limiting-with a current-mode PWM controller featuring slope compensation, soft-start, and error amplifier. Its dual-domain architecture separates line-side interface control from SMPS regulation sequencing.

It implements automatic power sequencing: after signature detection and classification, the internal MOSFET charges the input capacitor until RTN drops below 1.5 V relative to VEE, enabling the VCC regulator and initiating SMPS operation. The -80 suffix denotes built-in slope compensation and 80% max duty cycle-critical for stable flyback/forward converter operation above 50% duty.

Key Specifications

Pinout & Package

LM5070SD-80/NOPB is housed in a thermally enhanced 16-pin TSSOP package (Package Code PW) with exposed pad bonded to VEE for low θ_JA = 125 °C/W. Pin functions are validated per TI SNVS308G datasheet Rev. April 2013.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM5070SD-80/NOPB, the -50 variant lacks slope compensation and limits duty cycle to 50%, restricting topology flexibility, while the LT4275 targets PoE+ with higher power and split-architecture complexity - making LM5070SD-80/NOPB optimal for cost-sensitive, single-chip IEEE 802.3af Class 3 designs.

Availability

LM5070SD-80/NOPB is available at Aetrix Electronics and suitable for VoIP phones, IP cameras, wireless access points, and thin clients requiring stable component supply, full IEEE 802.3af compliance, and integrated PoE PD functionality.

Supply support for LM5070SD-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 with emphasis on reliability, efficiency, and system-level integration.

The LM5070 product line delivers integrated Power over Ethernet Powered Device interfaces with embedded PWM controllers, designed specifically for compact, standards-compliant PoE endpoints in communications and security equipment.

FAQ

What is the maximum input voltage supported by the LM5070SD-80/NOPB?

The LM5070SD-80/NOPB supports an absolute maximum VIN to VEE voltage of 80 V and an operating range of 1.8 V to 75 V. This allows robust operation across IEEE 802.3af PoE systems, including worst-case open-circuit conditions and legacy PSEs with elevated voltage tolerance. Operation above 75 V risks permanent damage per Absolute Maximum Ratings.

Does the LM5070SD-80/NOPB require external components for IEEE 802.3af signature detection?

Yes - the LM5070SD-80/NOPB requires an external 25 kΩ resistor connected between VIN and RSIG pins to establish the 23.75–26.25 kΩ signature impedance mandated by IEEE 802.3af. The device internally enables this resistor only during detection mode (VIN = 1.8–10 V) and disables it above 11 V to reduce standby power.

How does the LM5070SD-80/NOPB implement power sequencing between the PD interface and SMPS controller?

The LM5070SD-80/NOPB performs fully autonomous sequencing: after classification, the internal MOSFET charges the SMPS input capacitor until RTN falls below 1.5 V relative to VEE. This event triggers VCC regulator enablement, followed by soft-start initiation and PWM output activation - all without external timing components or microcontroller intervention.

Can the LM5070SD-80/NOPB be used in isolated dc-dc converter designs?

Yes - the LM5070SD-80/NOPB supports isolated topologies via its COMP and FB pins. In isolated designs, COMP drives an optocoupler transistor (using the internal 5 kΩ pull-up), while FB is tied to ARTN to disable the internal error amplifier. This configuration enables secondary-side regulation with minimal primary-side components.

What is the purpose of the ARTN pin on the LM5070SD-80/NOPB?

The ARTN pin serves as the dedicated analog ground return for noise-sensitive circuits including CS, COMP, FB, and RT. Separating ARTN from the high-current RTN path prevents switching noise from corrupting current sensing and feedback signals - critical for stable current-mode control and accurate regulation in the LM5070SD-80/NOPB.