STMicroelectronics L4976

Overview

L4976 from STMicroelectronics is a monolithic step-down switching regulator IC featuring an integrated 0.25 Ω internal D-MOS power transistor, adjustable output voltage from 0.5 V to 50 V, 8–55 V input range, and up to 300 kHz switching frequency. It delivers 1 A continuous output current with precise 5.1 V reference, voltage feed-forward regulation, and zero-load operation-used in industrial power supplies and distributed DC-DC conversion.

For engineers reviewing the L4976 datasheet, L4976 pinout, L4976 application, or L4976 equivalent, key selection criteria include its SO16W package thermal resistance (110 °C/W), pulse-by-pulse current limiting (typ. 2 A), hiccup-mode short-circuit protection, and feedback disconnection safeguard-critical for rugged 24 V/48 V bus-derived point-of-load designs.

Technical Context

The L4976 implements a voltage-mode PWM controller with internal oscillator, error amplifier, and bootstrap gate driver for high-side N-channel MOSFET operation. Its voltage feed-forward architecture dynamically adjusts duty cycle based on input voltage changes, improving transient response and line regulation across the 8–55 V input range.

It integrates thermal shutdown, overcurrent protection in both pulse-by-pulse and hiccup modes, and dedicated FB pin monitoring to detect open-loop failure. The COMP pin provides direct access to the error amplifier output for external compensation network design, supporting stable operation with wide output voltage and load ranges.

Key Specifications

Pinout & Package

The L4976 is housed in a 16-pin SO16W (Wide) surface-mount plastic package, optimized for thermal performance in high-current DC-DC applications. Pin 1, 7, 8, 9, 10, 15, and 16 are NC (no internal connection). Thermal pad is not present; PCB copper area under the package body is recommended for heat spreading.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2596-ADJ and TPS54302DDA, the L4976 uniquely combines ultra-wide 8–55 V input, integrated 0.25 Ω MOSFET, and 5.1 V reference in SO16W-making it optimal for industrial and telecom systems where input rail variability and reference-grade accuracy are mandatory.

Availability

L4976 is available at Aetrix Electronics and suitable for industrial PLCs, telecom line cards, automotive body control modules, and test equipment requiring stable component supply across extended temperature and input voltage ranges.

Supply support for L4976 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, digital, and mixed-signal ICs for industrial, automotive, and power applications.

The L4976 belongs to ST's legacy high-voltage DC-DC regulator product line, engineered specifically for robust, wide-input industrial power conversion where reliability under voltage transients and thermal stress is paramount.

FAQ

What is the minimum input voltage required for stable regulation?

The L4976 requires a minimum input voltage of 8 V to maintain regulation across its full output range. Below this threshold, the internal oscillator and gate driver may not function reliably, and dropout voltage increases sharply-verified in Table 5 where V_d = 0.367 V at V_CC = 10 V/1 A, implying functional margin begins at ≥8 V.

Can the L4976 operate without an external bootstrap capacitor?

No. The BOOT pin must be connected to a capacitor (typically 100 nF ceramic) between BOOT and OUT to generate the gate drive voltage above VCC needed to fully enhance the internal N-MOSFET. Omitting this capacitor results in insufficient gate voltage, high R_DS(ON), thermal runaway, and immediate shutdown.

How does the feedback disconnection protection work?

When the FB pin voltage rises above 3.8 V (e.g., due to open feedback resistor or broken trace), the internal comparator detects loss of regulation and forces the PWM controller into shutdown mode. This prevents uncontrolled output voltage rise-confirmed in Section 2.2 and Figure 2 block diagram where "FB" feeds directly into protection logic.

Is the 5.1 V reference usable as a system-level precision voltage source?

Yes-the VREF pin delivers a buffered 5.1 V ±1% (4.95–5.25 V) with 20 mA sink/source capability, tested across V_CC = 8–55 V and T_J = –40 to 150 °C. Its 0.4 mV/°C tempco and <10 mV load/line regulation make it suitable for ADC references or sensor excitation where ±0.5% absolute accuracy is acceptable.