Texas Instruments LM5070SDX-50/NOPB

Overview

LM5070SDX-50/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, 50% maximum duty cycle limit (no slope compensation), −40°C to +125°C operating junction temperature, and TSSOP-16 package. It enables single-output flyback or forward DC-DC converters in PoE-powered IP phones, wireless access points, and network cameras.

For engineers reviewing the LM5070SDX-50/NOPB datasheet, LM5070SDX-50/NOPB pinout, LM5070SDX-50/NOPB application, or LM5070SDX-50/NOPB equivalent, key selection criteria include IEEE 802.3af signature/classification compliance, programmable inrush current limit (75–390 mA), UVLO hysteresis control, internal high-voltage startup regulator (7.8 V), and thermal shutdown at 165°C.

Technical Context

The LM5070SDX-50/NOPB integrates a PoE PD interface with detection (1.8–10 V), classification (12.5–20.5 V), and inrush current limiting, plus a current-mode PWM controller featuring cycle-by-cycle current sensing (0.5 V threshold), soft-start (10 µA current source), and oscillator frequency set by RT resistor (175–225 kHz typical). Its 50% max duty cycle architecture eliminates slope compensation, simplifying design for non-isolated topologies.

It operates across 1.8–75 V input, uses internal 80V MOSFET for power sequencing, and delivers 800 mA peak gate drive on OUT. The device implements automatic power-good sequencing: RTN voltage drop below 1.5 V relative to VEE enables VCC regulation, which then triggers soft-start and SMPS enable-ensuring strict IEEE 802.3af timing compliance during capacitor charging.

Key Specifications

Pinout & Package

TSSOP-16 package (Package Number PW), thermally enhanced with exposed pad bonded to VEE; 0.65 mm pitch, 5.0 mm × 4.4 mm body size.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM5070SDX-80/NOPB, the LM5070SDX-50/NOPB eliminates slope compensation complexity for flyback use; versus LT4275, it integrates PWM control but lacks PoE+ classification-making it ideal for compact, single-chip 802.3af endpoints where cost and board space are critical.

Availability

LM5070SDX-50/NOPB is available at Aetrix Electronics and suitable for IP phones, wireless access points, network cameras, and VoIP door stations requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for LM5070SDX-50/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 specializing in analog, embedded processing, and connectivity technologies with over 50 years of innovation in power management ICs.

The LM5070 product line delivers integrated PoE PD interface and DC-DC controller solutions targeting space-constrained, cost-sensitive Ethernet-powered endpoints such as VoIP phones and surveillance cameras.

FAQ

What is the maximum input voltage rating for the LM5070SDX-50/NOPB?

The LM5070SDX-50/NOPB supports a VIN voltage range of 1.8 V to 75 V, with absolute maximum rating of 80 V for VIN to VEE. This 75 V operational limit ensures reliable operation across the full IEEE 802.3af PoE voltage envelope (up to 57 V nominal, with transient tolerance), and the device includes built-in protection against overvoltage stress on internal circuitry.

Does the LM5070SDX-50/NOPB require an external MOSFET for PoE interface operation?

No, the LM5070SDX-50/NOPB integrates an 80 V, 400 mA internal MOSFET with 1 Ω R_DS(on), eliminating the need for an external switch in the PoE interface path. This MOSFET handles signature resistor enable/disable, classification current sinking, and controlled inrush current limiting - enabling fully integrated PD interface functionality without discrete high-voltage components.

How does the LM5070SDX-50/NOPB implement IEEE 802.3af classification?

The LM5070SDX-50/NOPB implements IEEE 802.3af classification by sinking a programmable current (0–44 mA) from the RCLASS pin to VEE, using an internal 1.5 V reference. External resistor values (e.g., open for Class 0, 82.5 Ω for Class 2) set the classification current per Table 2 in the datasheet. Classification activates between 12.5 V and 20.5 V input and times out within 75 ms as required by the standard.

Can the LM5070SDX-50/NOPB be used in isolated DC-DC converter topologies?

Yes, the LM5070SDX-50/NOPB supports both isolated and non-isolated applications. For isolated topologies (e.g., flyback), the COMP pin provides an open-drain error amplifier output compatible with optocoupler feedback, while FB serves as the inverting input referenced to a 1.25 V internal bandgap. The internal error amplifier can be disabled by connecting FB to ARTN when secondary-side regulation is preferred.

What is the purpose of the ARTN pin on the LM5070SDX-50/NOPB?

The ARTN pin on the LM5070SDX-50/NOPB serves as the dedicated analog ground return for precision circuitry including the error amplifier, current sense amplifier, and oscillator. Separating ARTN from the high-current RTN path minimizes noise coupling into sensitive analog nodes - improving regulation accuracy, current-sense stability, and PWM timing integrity in noisy PoE environments.