STMicroelectronics L4957AD2.5

Overview

L4957AD2.5 from STMicroelectronics is a 2.5V fixed-output ultra-low-dropout linear regulator with internal N-channel MOSFET, delivering up to 5A output current, 200mΩ typical R_DS(on) at 125°C, and 0.6V max dropout at 2A - designed for post-regulation of 3.3V SMPS rails in processor I/O and low-voltage memory supplies.

For engineers reviewing the L4957AD2.5 datasheet, L4957AD2.5 pinout, L4957AD2.5 application, or L4957AD2.5 equivalent, key selection criteria include dropout voltage at full load, thermal shutdown threshold (150°C), ±2% output tolerance over line/load/temperature, quiescent current (0.6–2mA), and D2PAK package thermal resistance (R_thJC = 3°C/W).

Technical Context

The L4957AD2.5 integrates an internal N-channel DMOS pass transistor with 200mΩ typical on-resistance, enabling ultra-low dropout operation down to 0.6V at 2A. Its error amplifier uses an internal trimmed voltage reference (±2% total tolerance) and supports fast transient response via minimal 22µF output capacitance.

Protection architecture includes foldback current limiting (5.1–7.5A trip range), thermal shutdown with 29°C hysteresis, and short-circuit robustness across input range (3–14V). It operates without external compensation and requires only input (≥10µF) and output (≥22µF) ceramic or tantalum capacitors.

Key Specifications

Pinout & Package

Supplied in D2PAK (TO-263) surface-mount package with exposed drain pad for thermal conduction. Package meets ECOPACK® environmental requirements and supports JEDEC-standard lead-free soldering.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ultra-low-dropout linear regulator applications.

Compared with LM2940CT-2.5 and TPS75225KPWPR, the L4957AD2.5 uniquely balances 5A output, 0.6V dropout, and ±2% accuracy in D2PAK - making it optimal for high-current motherboard and graphics card I/O rails where thermal performance and headroom efficiency are critical.

Availability

L4957AD2.5 is available at Aetrix Electronics and suitable for motherboard core I/O supplies, processor post-regulation, and low-voltage memory interface applications requiring stable component supply and long-term industrial availability.

Supply support for L4957AD2.5 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The L4957A series targets high-current, low-dropout point-of-load regulation in computing infrastructure - specifically engineered to replace discrete MOSFET-based regulators in cost-sensitive, thermally constrained motherboard and add-in card designs.

FAQ

What is the minimum input voltage required for stable 2.5V output at 5A?

The L4957AD2.5 requires VIN ≥ 3.1V to maintain regulation at 5A, based on its 0.6V max dropout at 2A and confirmed 0.8V dropout at 5A per Figure 8's DC operating area. Below 3.1V, output collapses; operation within 3–14V input range is guaranteed per datasheet Section 3.1.

Can the L4957AD2.5 be used without an output capacitor?

No. A minimum 22µF output capacitor is mandatory for stability across all load conditions, as specified in Section 1 and Figure 2. Omitting it causes oscillation and potential device failure. Ceramic or tantalum types are acceptable; ESR must be within 10–100mΩ per application note AN2179.

Does the L4957AD2.5 support adjustable output voltage?

No. The L4957AD2.5 is a fixed 2.5V output device. ST offers no adjustable variant in the L4957A family; output voltage is set by internal trimming and cannot be modified externally. For adjustable LDOs, consider ST's LD1085 or LD1117 families.

How does thermal shutdown behave during sustained overload?

At junction temperature ≥150°C, thermal shutdown activates and holds output off until temperature drops to ~121°C (150°C – 29°C hysteresis). During this period, IN-to-OUT conduction ceases, preventing damage. Recovery is automatic and does not require power cycle or reset signal.