STMicroelectronics L4957AD1.5

Overview

L4957AD1.5 from STMicroelectronics is a 1.5V fixed-output ultra-low-dropout linear regulator with an internal N-channel MOSFET (R_DS(on) = 200 mΩ typ. @ T_J = 125°C), delivering up to 5A output current across a 3V–14V input range and maintaining ≤0.6V dropout at 2A. It features ±2% output voltage tolerance (including line/load variation), 0.6 mA quiescent current, thermal shutdown, and short-circuit protection-designed for high-current, low-voltage processor I/O and chipset supplies on motherboards.

For engineers reviewing the L4957AD1.5 datasheet, L4957AD1.5 pinout, L4957AD1.5 application, or L4957AD1.5 equivalent, key selection criteria include dropout voltage at full load, thermal resistance (R_thJC = 3°C/W), stability with ≥22 µF output capacitance, and compatibility with 3.3V rail-to-1.5V conversion at 2.5A in space-constrained embedded power domains.

Technical Context

The L4957AD1.5 integrates a charge-pump-driven N-channel DMOS pass transistor enabling ultra-low dropout operation without requiring a PNP/Pch pass device. Its internal error amplifier, trimmed voltage reference, and current-limiting circuitry deliver tight regulation (±2% over line/load/temperature) and fast transient response to minimize required output capacitance.

Thermal protection includes a 150°C shutdown threshold with 29°C hysteresis, and absolute maximum junction temperature is rated to +150°C. The device operates within a DC operating area bounded by (V_IN – V_OUT) > 2V and output current up to 5A at T_C = 25°C, derating to ~6.3A at T_J = 125°C under pulsed conditions.

Key Specifications

Pinout & Package

Supplied in D2PAK (TO-263) package: surface-mount, 3-pin, thermally enhanced plastic case with exposed drain pad for low R_thJC (3°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS75715 and NCP59150, the L4957AD1.5 offers superior thermal hysteresis (29°C), tighter output tolerance (±2% vs. ±3%), and lower quiescent current (0.6 mA), making it optimal for cost-sensitive, thermally demanding motherboard and graphics card designs where simplicity and reliability outweigh sequencing or monitoring needs.

Availability

L4957AD1.5 is available at Aetrix Electronics and suitable for motherboard power delivery, processor I/O supplies, and low-voltage memory subsystems requiring stable component supply across extended industrial temperature ranges and multi-year production cycles.

Supply support for L4957AD1.5 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, Switzerland, designing and manufacturing analog, microcontroller, power, and sensor solutions for automotive, industrial, and consumer markets.

The L4957A series belongs to ST's high-current linear regulator product line, engineered specifically for low-voltage, high-efficiency point-of-load regulation in computing and graphics platforms where minimal dropout, thermal resilience, and ±2% accuracy are essential.

FAQ

What is the minimum output capacitance required for stability with the L4957AD1.5?

A minimum of 22 µF low-ESR output capacitor is required to ensure stability across all load conditions (0–5A) and temperature ranges. This value is validated per ST's application note AN2421 and reflects worst-case phase margin requirements with the internal compensation network.

Can the L4957AD1.5 operate with a 2.8V input when regulating 1.5V output?

No. The datasheet specifies a minimum input voltage of 3V for reliable operation. At VIN = 2.8V, the device enters dropout region prematurely and cannot guarantee regulation, as confirmed by Figure 10's DC operating area boundary where (VIN – VOUT) must exceed 2V for full 5A capability.

Does the L4957AD1.5 require an external resistor divider for output voltage setting?

No. The L4957AD1.5 is a fixed-output device with factory-trimmed 1.5V reference. It has no feedback pins or external resistor connections - the output voltage is internally set and unadjustable, simplifying layout and reducing component count.

How does thermal shutdown behave during sustained overload?

When junction temperature reaches 150°C, thermal shutdown activates, disabling the output. After shutdown, the device remains off until temperature drops by 29°C (hysteresis), then automatically recovers. This behavior is fully characterized in Table 3 and prevents latch-up or permanent damage during prolonged overcurrent events.