STMicroelectronics L4972A

Overview

L4972A from STMicroelectronics is a monolithic stepdown switching regulator IC delivering 2A continuous output current with adjustable output voltage from 5.1V to 40V, operating in continuous conduction mode using BCD mixed-technology DMOS power transistors. It integrates precise 5.1V ±2% on-chip reference, feed-forward line regulation, PWM latch, thermal shutdown, and reset/power-fail monitoring-designed for stable microprocessor power supply in industrial control systems.

For engineers reviewing the L4972A datasheet, L4972A pinout, L4972A application, or L4972A equivalent, key selection criteria include its 200kHz max switching frequency, internal current limiting (2.5–3.5A), under-voltage lockout (11V turn-on with 1V hysteresis), soft-start timing control, and synchronous operation capability across multiple regulators.

Technical Context

The L4972A implements a fixed-frequency PWM control loop with sawtooth oscillator, error amplifier, comparator, and latch-ensuring single-pulse-per-period operation even under noise. Its feed-forward control modulates oscillator ramp amplitude with input voltage, achieving superior line regulation (12mV over 15–50V input).

Internal functions include bootstrap gate drive (capacitor-coupled, 12V referenced), open-drain reset output with programmable delay via external capacitor, and power-fail detection via pin 4 threshold (5.1V) with hysteresis. The device operates with 0–90% duty cycle range and supports external synchronization at pin 10.

Key Specifications

Pinout & Package

Available in PowerDIP20 (16+2+2) and SO20 packages. Both feature identical pin functions and thermal characteristics (R_{th j-pins}: 12°C/W DIP, 16°C/W SO20).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar stepdown switching regulator applications.

Compared with LM2596-5.0 and TPS54202, the L4972A uniquely combines adjustable output, built-in reset/power-fail signaling, and feed-forward line regulation-making it optimal for microprocessor-based industrial systems requiring autonomous fault response and wide-input stability without added supervisory ICs.

Availability

L4972A is available at Aetrix Electronics and suitable for industrial PLC power supplies, microprocessor core voltage regulation, synchronized multi-rail converters, and high-efficiency 24V-to-12V adapters requiring stable component supply across extended product lifecycles.

Supply support for L4972A 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, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The L4972A belongs to ST's legacy power management IC portfolio, specifically engineered for robust, high-current DC-DC conversion in microprocessor-centric industrial systems where integrated supervision and thermal resilience are critical.

FAQ

What is the minimum input voltage required for reliable startup of the L4972A?

The L4972A features an under-voltage lockout with a nominal turn-on threshold of 11V and 1V hysteresis, meaning it begins switching only when input voltage rises above 11V and remains active down to ~10V. This ensures sufficient gate drive voltage for the internal DMOS transistor and avoids unstable operation during brownout conditions.

Can the L4972A be used to generate output voltages below 5.1V?

No-the L4972A's internal reference is fixed at 5.1V ±2%, and its feedback architecture is designed to regulate *at or above* this voltage using external resistor dividers. Output voltages below 5.1V are not supported; alternative regulators such as the L4970A (adjustable down to 5.1V) or modern buck controllers with lower reference voltages would be required.

How does the bootstrap capacitor value scale with switching frequency?

Bootstrap capacitance must increase as switching frequency decreases to maintain sufficient gate charge: ≥680nF at 20kHz, ≥470nF at 50kHz, ≥330nF at 100kHz, and ≥220nF at 200kHz. This ensures the bootstrap capacitor retains enough charge between cycles to fully enhance the DMOS gate, preventing shoot-through or reduced efficiency.

Is the RESET OUT pin compatible with 3.3V microcontrollers?

Yes-the RESET OUT pin is an open-drain output rated for 50V maximum and capable of sinking up to 15mA. When pulled up to 3.3V via an external resistor, it delivers a clean active-low reset signal compatible with 3.3V logic inputs, provided the pull-up resistor value limits current to within the sink capability.