Texas Instruments LM3525M-H

Overview

LM3525M-H from Texas Instruments (formerly National Semiconductor) is a single-port, active-high-enable high-side USB power switch with integrated over-current and thermal protection. It delivers ≤120 mΩ R_ON at 5V, supports 2.7–5.5V 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 per-port power control.

For engineers reviewing the LM3525M-H datasheet, LM3525M-H pinout, LM3525M-H application, or LM3525M-H equivalent, this page details its USB 1.1/2.0-compliant power switching behavior, SO-8 package layout, thermal shutdown hysteresis (135°C trip / 125°C reset), UVLO thresholds (1.9 V rising / 1.8 V falling), and design implications of its open-drain FLG output and dual OUT pin configuration.

Technical Context

The LM3525M-H implements a P-channel MOSFET high-side switch with active-high enable logic, internal current-limit sensing, and fault flag assertion on undervoltage, over-current, or thermal shutdown. Its 1 ms transient delay circuitry is hardwired to ignore brief inrush events without external RC components.

It features built-in undervoltage lockout (UVLO) that disables switching below 1.8 V and prevents turn-on until VIN exceeds 1.9 V; thermal shutdown activates at 135°C with 10°C hysteresis; and its dual OUT pins (6 & 8) must be tied together to handle ≥500 mA continuous load current while maintaining ≤120 mΩ on-resistance at 5V.

Key Specifications

Pinout & Package

LM3525M-H is housed in an SO-8 package (NS Package Number M08A), with exposed pad not electrically connected. Pin 4 and Pin 5 are NC (not internally connected); Pins 6 and 8 are bonded together as the single switch output terminal.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TUSB2036VFR and TPS2051BDBVR, the LM3525M-H uniquely combines 1 A short-circuit rating, 1 ms inrush-tolerant fault reporting, and thermal shutdown in a minimal SO-8 footprint - making it optimal for space-constrained, high-reliability single-port USB power control where discrete protection is impractical.

Availability

LM3525M-H is available at Aetrix Electronics and suitable for notebook PC root hubs, self-powered USB monitor hubs, and high-power peripheral docks requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for LM3525M-H 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 full technical and supply chain responsibility for legacy National products including the LM3525M-H.

The LM3525M-H belongs to National Semiconductor's USB power management portfolio, engineered specifically for per-port VBUS control in host and self-powered USB hubs - emphasizing reliability, inrush immunity, and minimal external component count.

FAQ

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

The LM3525M-H features active-high enable logic: the switch turns ON when the EN pin voltage is ≥2.4 V and turns OFF when EN ≤0.8 V. This is distinct from the LM3525M-L variant, which uses active-low enable. The LM3525M-H is compatible with both 3.3 V and 5 V logic families without level translation, and its EN pin leakage remains below ±0.5 µA across temperature.

How does the LM3525M-H handle inrush current during USB hot-plug events?

The LM3525M-H internally limits inrush current to ≤1 A during turn-on and incorporates a fixed 1 ms delay before asserting the FLG pin during over-current conditions. This delay prevents false fault reporting caused by bulk capacitor charging transients. The LM3525M-H does not require external soft-start circuitry, and its smooth turn-on characteristic avoids upstream VBUS droop exceeding USB specification limits.

What protection features are integrated into the LM3525M-H?

The LM3525M-H integrates three independent protection mechanisms: undervoltage lockout (UVLO) that disables switching below 1.8 V and prevents turn-on until VIN exceeds 1.9 V; current limiting with a typical 1.0 A short-circuit threshold; and thermal shutdown triggered at 135°C with 10°C hysteresis. All three conditions assert the open-drain FLG pin low, providing unified fault signaling without external supervision.

Can the LM3525M-H be used outside of USB applications?

Yes - the LM3525M-H functions as a general-purpose 2.7–5.5 V high-side P-channel switch with current limiting and thermal protection. Its 500 mA continuous rating, ≤120 mΩ R_ON, and FLG fault reporting make it suitable for industrial sensors, auxiliary power rails, or any 5 V system requiring robust, self-protecting power gating - though USB-specific timing (e.g., 1 ms flag delay) may not be required in non-USB use cases.

What is the recommended PCB layout practice for the LM3525M-H OUT pins?

Pins 6 and 8 of the LM3525M-H must be externally tied together as a single output node. To maintain low impedance and minimize voltage drop, both pins should connect directly to a wide, low-resistance copper pour leading to the USB connector VBUS line. Avoid vias in the OUT path; if unavoidable, use multiple large vias in parallel. Keep the IN-to-OUT current loop area small to reduce EMI, and place the 33 µF input capacitor within 5 mm of the IN and GND pins.