STMicroelectronics L4975A

Overview

L4975A from STMicroelectronics is a 5A monolithic step-down switching regulator IC with adjustable output voltage (5.1V–40V), internal DMOS power transistor, and integrated reset/power-fail monitoring for microprocessor systems. It delivers up to 92% efficiency at 5A/12V, supports switching frequencies up to 500kHz, and features feed-forward line regulation, soft-start, thermal shutdown, and undervoltage lockout with 1V hysteresis.

For engineers reviewing the L4975A datasheet, L4975A pinout, L4975A application, or L4975A equivalent, key selection considerations include its 15-lead Multiwatt package, bootstrap gate drive requirement, open-collector reset output, and precise 5.1V ±2% on-chip reference-critical for stable DC-DC conversion in industrial power supplies and embedded computing rails.

Technical Context

The L4975A operates in continuous conduction mode using BCD mixed-technology integration of vertical DMOS power transistors and CMOS/bipolar control circuitry. Its PWM control loop includes a sawtooth oscillator with voltage feed-forward, error amplifier with external RC compensation (Pin 10), and latch-based single-pulse-per-period modulation to suppress noise-induced multiple triggering.

Internal functions include pulse-by-pulse current limiting (5.5–7.5A threshold), thermal shutdown at ~150°C with hysteresis, and a dedicated reset/power-fail circuit with programmable delay (via Pin 5 capacitor) and dual-threshold detection (Pin 3 input, Pin 4 open-drain output). The device requires an external bootstrap capacitor (Pin 6) and supports synchronization across multiple units via Pin 13.

Key Specifications

Pinout & Package

Package: 15-lead Multiwatt plastic power package (vertical mounting, heatsink-compatible); thermal resistance R_{th j-case} = 1°C/W, R_{th j-amb} = 35°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down switching regulator applications.

Compared with LM2596-5.0 and TPS54560, the L4975A uniquely integrates reset/power-fail signaling, feed-forward line regulation, and bootstrap gate drive in a single 15-pin package-enabling compact, self-monitoring 5A buck designs without external supervisors or level shifters.

Availability

L4975A is available at Aetrix Electronics and suitable for industrial PLC power rails, embedded microprocessor core supplies, test equipment DC power modules, and motor drive auxiliary supplies requiring stable component supply and long-term production continuity.

Supply support for L4975A 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, specializing in power management, analog, and microcontroller technologies for industrial, automotive, and embedded markets.

The L4975A belongs to ST's legacy MultiPower BCD technology product line, designed specifically for high-current, high-efficiency DC-DC conversion in space-constrained industrial power systems requiring integrated protection and supervision.

FAQ

What is the minimum input voltage required for the L4975A to start switching?

The L4975A has a turn-on threshold of 10–12V (typical 11V) with 1V hysteresis. Below 10V, the internal start-up circuit (Pin 15) remains inactive and the DMOS transistor stays off. Once enabled, it sustains operation down to ~5.1V input if output voltage is regulated, but stable regulation requires sufficient headroom-typically ≥1.5V above output voltage for continuous mode.

Can the L4975A operate without an external bootstrap capacitor?

No. The L4975A requires an external bootstrap capacitor (Pin 6 to OUTPUT) to generate the gate drive voltage (>12V) needed for the internal DMOS transistor. Omitting it results in insufficient gate-source voltage, causing weak conduction, excessive conduction losses, thermal shutdown, or failure to regulate. Capacitor value depends on switching frequency (e.g., 220nF at 200kHz).

How does the reset function respond to output voltage drop versus input voltage drop?

The reset output (Pin 4) goes low immediately if either the output voltage falls below 5V (monitored internally) OR the input voltage drops below the threshold set at Pin 3 (e.g., 5.1V via divider). The power-fail circuit uses separate comparators for each condition, ensuring fast fault response regardless of failure origin-critical for microprocessor safe shutdown.

Is the L4975A RoHS-compliant and halogen-free?

Yes. As a STMicroelectronics device manufactured after 2006 and conforming to EC Directive 2011/65/EU, the L4975A is RoHS-compliant and halogen-free. The Multiwatt15 package uses lead-free terminations and compliant molding compounds; full compliance documentation is available in ST's official product change notices and material declarations.