Texas Instruments LM3544M-L

Overview

LM3544M-L from Texas Instruments is a quad-channel high-side power switch IC designed for USB 1.1/2.0 hub power management, featuring 90 mΩ typical on-resistance, 500 mA continuous per port, 7 ms fault flag delay, and integrated short-circuit/thermal/UVLO protection in a 16-pin SOIC package. It enables controlled power delivery to downstream USB devices in root, self-powered, and bus-powered hubs.

For engineers reviewing the LM3544M-L datasheet, LM3544M-L pinout, LM3544M-L application, or LM3544M-L equivalent, key selection criteria include per-port current capability, fault flag timing, enable logic polarity (active-low), thermal shutdown behavior, and compliance with USB voltage-drop requirements under 500 mA load.

Technical Context

The LM3544M-L implements four independent N-channel MOSFET high-side switches with internal charge-pump gate drivers, enabling operation from 2.7V–5.5V input while maintaining low R_ON. Each channel features dedicated active-low EN inputs and open-drain FLAG outputs with 7 ms internal filtering to suppress hot-plug transients.

Its protection architecture includes dual-stage thermal shutdown (145°C first stage, 160°C second stage), current foldback limiting (2.0 A threshold, 1.0 A hold level), and undervoltage lockout at 1.8 V. Fault reporting is synchronized across paired ports (1/2 and 3/4) during UVLO events.

Key Specifications

Pinout & Package

LM3544M-L is housed in a 16-pin SOIC (D) package with exposed pad not present; thermal resistance θ_JA = 130°C/W. Pin assignments are validated per TI SNVS062C datasheet Figure 2 (LM3544-L).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS2044B and TPS22965, LM3544M-L provides unique value in USB-compliant quad-channel operation with integrated foldback, dual-stage thermal shutdown, and 7 ms hardware-filtered fault flags-reducing firmware complexity and improving system-level reliability in hub architectures.

Availability

LM3544M-L is available at Aetrix Electronics and suitable for USB hub design, peripheral power sequencing, and Wake-on-USB implementations requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LM3544M-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 is a global semiconductor leader specializing in analog, embedded processing, and connectivity technologies with over 90 years of innovation in power management ICs.

The LM3544 product line delivers integrated USB-compliant high-side power switches optimized for fault-tolerant, low-dropout power distribution in root, self-powered, and bus-powered hub applications.

FAQ

What is the enable logic polarity of LM3544M-L?

The LM3544M-L uses active-low enable inputs (EN1–EN4). A logic-low signal on any EN pin activates the corresponding high-side switch. This matches the LM3544-L variant specified in TI SNVS062C, distinguishing it from the active-high LM3544-H. The LM3544M-L datasheet confirms ENX pin function as active-low with V_IL ≤ 0.4 V at 2.7–4.5 V supply, ensuring reliable TTL/CMOS interfacing. All functional timing and protection features of LM3544M-L remain identical to the base LM3544-L specification.

Does LM3544M-L support USB 2.0 compliance?

Yes, LM3544M-L is explicitly designed and qualified for USB 1.1 and USB 2.0 applications. Its 90 mΩ typical on-resistance ensures ≤250 mV voltage drop at 500 mA, satisfying USB 2.0 V_BUS droop requirements. The 7 ms fault flag delay filters hot-plug transients, and its current foldback + dual-stage thermal shutdown meet USB power delivery safety expectations. TI's datasheet states "excellent choice for use in Root, Self-Powered and Bus-Powered USB Hubs" - confirming full protocol-layer agnosticism and physical-layer compliance for both standards.

What is the maximum junction temperature rating for LM3544M-L?

The LM3544M-L has a maximum junction temperature (T_JMAX) of 150°C, with thermal shutdown activating in two stages: first at ~145°C to disable only current-limited ports, and second at 160°C to shut down all four channels and assert all FLAG outputs. The SOIC package exhibits θ_JA = 130°C/W, so at 500 mA per port and 90 mΩ R_ON, power dissipation per switch is ~22.5 mW - keeping junction rise well below limits in standard layouts. TI's Absolute Maximum Ratings table confirms 150°C as the absolute ceiling before potential damage.

Can LM3544M-L drive loads beyond 500 mA continuously?

No, LM3544M-L is rated for 500 mA continuous output current per port under recommended operating conditions (2.7–5.5 V, −40°C to 125°C junction). While its short-circuit current reaches 1.25 A max, sustained operation above 500 mA violates the DC Electrical Characteristics table and risks thermal shutdown due to power dissipation exceeding safe limits in the SOIC package. The 500 mA rating accounts for worst-case R_ON (130 mΩ), ambient temperature, and PCB thermal performance - exceeding it compromises reliability and voids USB voltage-drop compliance.

How does the fault flag delay work in LM3544M-L?

The LM3544M-L incorporates a fixed 7 ms internal delay on all FLAGx outputs, beginning when an overcurrent, UVLO, or thermal event is detected. This delay prevents false flag assertions during benign hot-plug inrush or transient dips, allowing output capacitors to charge fully before fault evaluation. If the condition persists past 7 ms, the corresponding FLAG pin pulls low (open-drain, ≤0.3 V at 10 mA). No external RC network is required unless longer delays are needed - TI's datasheet confirms this internal timing eliminates typical external filtering in USB hub designs.