STMicroelectronics L4978D013TR

Overview

L4978D013TR from STMicroelectronics is a monolithic step-down switching regulator IC with integrated 0.25Ω D-MOS power transistor, delivering up to 2A output current across an adjustable output voltage range of 3.3V to 50V. It operates from 8V to 55V input, features ±1% 3.3V internal reference, adjustable 90–300kHz switching frequency, and supports zero-load operation in inhibit mode. Used in industrial DC-DC conversion where wide VIN and precise VOUT stability are required.

For engineers reviewing the L4978D013TR datasheet, L4978D013TR pinout, L4978D013TR application, or L4978D013TR equivalent, key selection criteria include its 2A continuous output capability, SO16W package thermal performance (R_th(j-amb) = 110°C/W), pulse-by-pulse current limiting, and feedback disconnection protection-critical for reliable high-voltage buck designs.

Technical Context

The L4978D013TR implements voltage-mode PWM control with feedforward regulation, using an internal 3.3V reference and error amplifier with 57dB open-loop gain and 2.5mS transconductance. Its oscillator allows frequency setting via external R_OSC/C_OSC, enabling stable operation up to 300kHz while maintaining <±6% variation over input voltage and <±4% over temperature.

Thermal shutdown, hiccup-mode short-circuit protection, soft-start (via SS_INH pin capacitor), and inhibit functionality (active-low logic input) are fully integrated. The BOOT pin drives the high-side MOSFET gate using a charge pump, supporting duty cycles up to 97% and enabling high-V_IN/low-V_OUT conversion without external bootstrap components.

Key Specifications

Pinout & Package

Package: SO16W (wide-body SOIC-16), surface-mount, RoHS-compliant, with exposed thermal pad (not electrically connected). Pin 1 marked by notch; pins 1, 7, 8, 9, 10, 15, and 16 are NC (no internal connection).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM5116PWPR and MP2482DJ-LF-Z, the L4978D013TR uniquely combines integrated 0.25Ω FET, 8–55V operation, adjustable 3.3–50V output, and feedforward regulation-making it optimal for mid-power industrial buck converters needing flexibility and fault resilience without external power devices.

Availability

L4978D013TR is available at Aetrix Electronics and suitable for industrial PLC power supplies, automotive body control modules, telecom remote radio units, and factory automation sensor hubs requiring stable component supply across extended temperature and voltage ranges.

Supply support for L4978D013TR 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, MCU, and sensor solutions for industrial, automotive, and consumer markets.

The L4978 belongs to ST's legacy high-voltage monolithic DC-DC regulator product line, engineered specifically for rugged industrial and transportation applications demanding wide input range, integrated protection, and reliable operation from -40°C to +125°C.

FAQ

What is the maximum recommended output current for continuous operation?

The L4978D013TR delivers 2A continuously under specified thermal conditions: ambient ≤60°C, SO16W package mounted on standard FR4 with adequate copper area, and V_IN ≤48V. At 55V input or elevated ambient, derating applies-see Table 4 for R_th(j-amb) = 110°C/W and Figure 21 for power dissipation vs. V_IN.

How does the voltage feedforward function improve regulation?

Voltage feedforward dynamically adjusts the PWM ramp slope in proportion to input voltage, making the duty cycle inherently less sensitive to V_IN changes. This yields faster line transient response and reduces output voltage deviation during input steps-measured at 5mV line regulation over 8–55V input range.

Can the L4978D013TR operate with no load?

Yes-when INH is high, the device maintains regulation down to zero load current with 6mA quiescent draw. When INH is pulled low, it enters standby mode drawing only 200µA, enabling true zero-power state for battery backup or safety-critical shutdown.

What is the purpose of the NC pins (1, 7, 8, 9, 10, 15, 16) in the SO16W package?

These pins are not internally connected to the silicon die. They serve mechanical and packaging roles-improving mold integrity and thermal mass-but carry no electrical function. ST recommends leaving them unconnected or tying to GND for mechanical stability; no current flows through them under any condition.