Texas Instruments LM3525M-L

Overview

LM3525M-L from Texas Instruments (formerly National Semiconductor) is a single-port, active-low-enable high-side USB power switch with integrated over-current and thermal protection. It delivers ≤120 mΩ R_ON at 5V, supports 2.7V–5.5V input, provides 1 ms fault flag delay to suppress hot-plug inrush false triggers, and delivers up to 1 A short-circuit current limit - designed for notebook PC USB root hubs and self-powered hub ganged power control.

For engineers reviewing the LM3525M-L datasheet, LM3525M-L pinout, LM3525M-L application, or LM3525M-L equivalent, key selection criteria include active-low enable logic, SO-8 package compatibility, 1A current limiting threshold, thermal shutdown hysteresis (135°C trip / 125°C release), and UL recognition (REF #205202) for safety-critical USB power delivery designs.

Technical Context

The LM3525M-L implements a P-channel MOSFET high-side switch with internal current-sense amplifier, comparator-based over-current detection, and bandgap-referenced undervoltage lockout (UVLO) that activates at 1.9 V (rising) and deactivates at 1.8 V (falling). Its fault flag is open-drain, active-low, and incorporates a fixed 1 ms delay to reject transient inrush events during hot-plug.

Thermal shutdown uses a dedicated die temperature sensor with 10°C hysteresis (135°C on, 125°C off) to disable the output MOSFET without external intervention. The device operates across −40°C to +85°C ambient and supports continuous load currents ≥500 mA while maintaining <100 µA operating supply current.

Key Specifications

Pinout & Package

LM3525M-L is housed in an SO-8 package (NS Package Number M08A), with pins 6 and 8 internally tied together as the switched output terminal. Pins 4 and 5 are not internally connected and must remain unconnected in PCB layout.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar USB power switch applications.

Compared with TUSB2036IPW and TPS2051BDBVR, the LM3525M-L uniquely combines UL recognition, 1A current limit, 1 ms inrush-tolerant fault flag, and active-low enable in SO-8 - making it optimal for space-constrained, safety-compliant single-port USB power control where discrete switching and fault visibility are required.

Availability

LM3525M-L is available at Aetrix Electronics and suitable for notebook PC USB root hubs, self-powered USB monitor hubs, and high-power peripheral inrush limiting applications requiring stable component supply, long-term lifecycle support, and compliance with USB 2.0 power delivery requirements.

Supply support for LM3525M-L 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 acquired National Semiconductor in 2011 and maintains its legacy analog portfolio, including precision power management ICs with safety certifications and USB compliance.

The LM3525M-L belongs to National Semiconductor's USB power switch product line, engineered specifically for reliable, standards-compliant VBUS control in portable and embedded computing systems with stringent thermal and safety requirements.

FAQ

What is the enable logic polarity of the LM3525M-L?

The LM3525M-L features active-low enable logic: the internal P-channel MOSFET turns ON when the EN pin voltage is ≤0.8V and turns OFF when EN ≥2.4V. This allows direct interfacing with low-voltage microcontrollers or GPIOs without level-shifting. The LM3525M-L differs from the LM3525M-H variant, which uses active-high enable. Always verify EN pin voltage thresholds against your system's logic levels before design-in.

Does the LM3525M-L require external components for basic operation?

No, the LM3525M-L operates autonomously with only input and output capacitors required per USB specification - a 33 µF input tantalum capacitor and ≥120 µF output bulk capacitance. No external resistors, capacitors, or diodes are needed for enable control, fault flag pull-up, or current limiting. The 1 ms fault flag delay, UVLO, thermal shutdown, and current limit are fully internal and factory-trimmed.

How does the LM3525M-L handle thermal overload conditions?

The LM3525M-L integrates a die-temperature sensor that disables the output MOSFET when junction temperature reaches 135°C and re-enables it after cooling to 125°C. This 10°C hysteresis prevents thermal oscillation and enables self-recovery without system intervention. During shutdown, the FLG pin asserts low to signal thermal fault, allowing host controllers to log or respond to overheating events.

Is the LM3525M-L UL-recognized, and what does that mean for my design?

Yes, the LM3525M-L is UL Recognized Component (REF #205202), meaning it has been evaluated by UL to meet specific safety standards for component-level construction and performance. This recognition simplifies end-equipment safety certification for USB-powered devices, particularly in notebook PCs and self-powered hubs, by reducing the need for additional isolation or protection circuitry around the switch.

Can the LM3525M-L be used in 3.3V-only systems?

Yes - the LM3525M-L accepts input voltages from 2.7V to 5.5V and supports 3.3V logic thresholds on its EN pin (VIH ≤0.8V for ON, VIL ≥2.4V for OFF). It is commonly used to protect 3.3V USB peripherals by acting as an inrush limiter between a 3.3V supply and downstream capacitance. Its R_ON increases to ≤160 mΩ at 2.7V, still supporting ≥500 mA continuous load.