STMicroelectronics L78M09CV-DG

Overview

L78M09CV-DG from STMicroelectronics is a three-terminal positive fixed-voltage linear regulator delivering 9 V at up to 500 mA output current, housed in a TO-220FP package with thermal overload, short-circuit, and safe operating area (SOA) protection. It features ±2 % output voltage tolerance (AB/AC grade), 2 V dropout voltage, and operates across –40 °C to +125 °C junction temperature range - ideal for local on-card regulation in industrial power supplies and embedded control modules.

For engineers reviewing the L78M09CV-DG datasheet, L78M09CV-DG pinout, L78M09CV-DG application, or L78M09CV-DG equivalent, key selection criteria include guaranteed 500 mA load capability with internal current limiting, 56 dB supply voltage rejection at 120 Hz, 58 µV RMS output noise (10 Hz–100 kHz), and compatibility with standard input/output bypass capacitors (0.33 µF CI / 0.1 µF CO).

Technical Context

This device implements a monolithic NPN pass transistor architecture with integrated bandgap reference, error amplifier, and protection circuitry. Its fixed 9 V output is stabilized via internal feedback without external components, and it maintains regulation under line variations (VI = 11.5–25 V) and load changes (IO = 5–500 mA) at TJ = 25 °C.

Thermal shutdown activates when junction temperature exceeds ~165 °C, and SOA protection dynamically limits collector-emitter power dissipation during high-VCE conditions. The TO-220FP package provides 5 °C/W junction-to-case thermal resistance, enabling >500 mA operation with adequate heatsinking.

Key Specifications

Pinout & Package

The L78M09CV-DG uses a TO-220FP (Full Pack) package - a variant of TO-220 with insulated tab and shorter leads - offering 5 °C/W junction-to-case thermal resistance and compatibility with standard clip-on heatsinks.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78M09CDT-TR and MC78M09BDTG, the L78M09CV-DG offers tighter ±2 % output accuracy, guaranteed –40 °C startup, and superior thermal performance (5 °C/W RthJC), making it the preferred choice for industrial and automotive applications demanding long-term stability and fault resilience.

Availability

L78M09CV-DG is available at Aetrix Electronics and suitable for industrial PLC I/O modules, automotive body control units, medical patient monitor front-ends, and test & measurement signal conditioning boards requiring stable component supply and long-lifecycle support.

Supply support for L78M09CV-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 microcontrollers, power management ICs, sensors, and discrete components for industrial, automotive, and consumer markets.

The L78M series belongs to ST's precision 500 mA linear regulator product line, engineered specifically for robust local regulation in space-constrained, thermally demanding applications where reliability and extended temperature operation are critical.

FAQ

What is the minimum input voltage required for stable 9 V output?

The L78M09CV-DG requires a minimum input voltage of 11.5 V to maintain regulation across its full 500 mA load range and temperature specification (–40 °C to +125 °C). At 25 °C and 350 mA load, the dropout voltage is 2 V, so 11 V input may suffice - but 11.5 V ensures margin for line drop, temperature drift, and worst-case tolerance.

Can this regulator be used without input or output capacitors?

While the L78M09CV-DG is internally compensated and does not require output capacitance for stability, an input bypass capacitor (≥0.33 µF) is mandatory when the regulator is located more than a few centimeters from the main filter capacitor to prevent oscillation due to lead inductance. Output capacitance (≥0.1 µF) is recommended to improve transient response but not required for basic regulation.

How does thermal protection behave under sustained overload?

Under sustained overload, the L78M09CV-DG's thermal shutdown circuit disables the pass transistor when junction temperature reaches approximately 165 °C. After shutdown, the device cools passively; once junction temperature falls by ~20 °C, regulation automatically resumes. This hiccup-mode behavior prevents permanent damage while allowing recovery without manual reset.

Is the TO-220FP package electrically insulated?

Yes - the TO-220FP (Full Pack) variant used in L78M09CV-DG features an electrically insulated metal tab, eliminating the need for insulating washers when mounted to a grounded heatsink. This simplifies mechanical assembly and improves thermal reliability compared to standard TO-220, which requires isolation hardware to avoid shorting the output pin (pin 3) to ground.