STMicroelectronics L78S12CV-DG

Overview

L78S12CV-DG from STMicroelectronics is a three-terminal fixed-output positive linear voltage regulator delivering 12 V at up to 2 A, featuring internal current limiting, thermal shutdown, and safe operating area (SOA) protection. It operates with input voltages up to 30 V (for 1 A load), maintains ±5% output voltage accuracy over line/load/temperature, and is used for local on-card regulation in industrial power supplies, motor control logic rails, and embedded system auxiliary power.

For engineers reviewing the L78S12CV-DG datasheet, L78S12CV-DG pinout, L78S12CV-DG application, or L78S12CV-DG equivalent, key selection criteria include dropout behavior under 2 A load, thermal resistance (5 °C/W junction-to-case), short-circuit peak current (3 A), and ripple rejection (47 dB at 120 Hz).

Technical Context

The L78S12CV-DG implements a monolithic series pass transistor architecture with built-in foldback current limiting and thermal foldback. Its SOA protection dynamically restricts power dissipation during overload by reducing output current as junction temperature rises beyond 125 °C.

It requires no external compensation and remains stable with or without an output capacitor-though a 0.33 µF ceramic input cap and 0.1 µF ceramic output cap are recommended for transient response. Dropout voltage is ~2.5 V at 2 A (T_J = 25 °C), increasing to ~3.2 V at T_J = 125 °C.

Key Specifications

Pinout & Package

Supplied in TO-220 (dual-gauge) package with standard 3-pin vertical mounting configuration: Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output. The metal tab is electrically connected to Pin 2 (Ground) and serves as primary thermal path to heatsink.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output linear regulator applications.

Compared with LM7812CT and LD1085V12, the L78S12CV-DG offers superior fault resilience (SOA + thermal foldback), tighter load regulation (150 mV vs. 250+ mV), and guaranteed 2 A delivery with TO-220 heatsinking-making it optimal for industrial environments where reliability under stress is non-negotiable.

Availability

L78S12CV-DG is available at Aetrix Electronics and suitable for industrial PLC power rails, motor driver logic supplies, and embedded system auxiliary power requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for L78S12CV-DG 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 silicon solutions for automotive, industrial, and power management applications.

The L78S series belongs to ST's legacy linear regulator product line, engineered specifically for ruggedized fixed-voltage local regulation in harsh industrial and motor-control environments where fault tolerance and thermal robustness are prioritized over ultra-low quiescent current.

FAQ

What is the minimum input voltage required for L78S12CV-DG to maintain regulation at full 2 A load?

The minimum input voltage is 17 V under worst-case conditions (T_J = 125 °C, V_OUT = 12.5 V). At 25 °C, dropout is ~2.5 V, so 14.5 V suffices for 12 V output at 1 A; however, derating to 17 V ensures regulation across temperature and load extremes per ST's recommended operating conditions.

Can L78S12CV-DG be used without a heatsink?

Yes, but only for ≤500 mA continuous output at ambient ≤40 °C with free-air convection. At 2 A, junction temperature exceeds 150 °C within seconds without heatsinking. ST specifies R_thJA = 50 °C/W; a 10 °C/W heatsink is required to sustain 2 A at 70 °C ambient.

Does L78S12CV-DG require an input bypass capacitor?

Yes-a minimum 0.33 µF ceramic capacitor placed within 1 cm of Pin 1 (Input) and Pin 2 (Ground) is mandatory per ST's layout guidelines. This prevents oscillation during fast line transients and reduces high-frequency noise coupling into the regulator's control loop.

Is L78S12CV-DG RoHS-compliant and halogen-free?

Yes. Per ST's ECOPACK® documentation, L78S12CV-DG carries ECOPACK2 certification: lead-free, RoHS-compliant, and halogen-free (per IEC 61249-2-21), with full material declaration available in ST's Quality & Reliability database.