STMicroelectronics L78M12CDT-TR

Overview

L78M12CDT-TR from STMicroelectronics is a three-terminal positive fixed-voltage linear regulator delivering 12 V ±4 % output at up to 0.5 A, housed in a TO-220FP (IPAK) package with thermal overload, short-circuit, and safe operating area protection. It operates across 0–125 °C junction temperature and supports local on-card regulation in industrial power supplies, embedded controllers, and sensor interface circuits.

For engineers reviewing the L78M12CDT-TR datasheet, L78M12CDT-TR pinout, L78M12CDT-TR application, or L78M12CDT-TR equivalent, key selection criteria include output voltage tolerance (±4 %), dropout voltage (2 V), supply voltage rejection (55 dB at 120 Hz), thermal resistance (5 °C/W junction-to-case), and quiescent current (6 mA).

Technical Context

This device implements a monolithic series pass transistor with internal current limiting, thermal shutdown, and SOA compensation-ensuring robustness under overload, overtemperature, and output short conditions. Its architecture requires no external compensation for stability but benefits from 0.33 µF input and 0.1 µF output capacitors for transient response and high-frequency noise suppression.

Designed for fixed-output operation, it supports extended functionality via external components: adjustable output voltage (via resistive divider), constant-current sourcing, high-current boosting (with external pass transistor), and tracking configurations. Input voltage range is 14.5–30 V DC for reliable 12 V regulation at full load.

Key Specifications

Pinout & Package

TO-220FP (IPAK) package: 3-pin vertical mounting variant with insulated tab, optimized for PCB surface-mount assembly and moderate-power thermal management. Tab is electrically connected to Pin 2 (Ground).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78M12CDT and MC78M12CDTG, the L78M12CDT-TR offers the lowest junction-to-case thermal resistance (5 °C/W), enabling higher sustained output current in thermally constrained layouts-while its C-grade tolerance (±4 %) balances cost and performance for non-critical 12 V rails.

Availability

L78M12CDT-TR is available at Aetrix Electronics and suitable for industrial PLCs, automotive body electronics, medical sensor modules, and point-of-sale terminals requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for L78M12CDT-TR 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, specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

The L78M series belongs to ST's precision 500 mA linear regulator product line, engineered for cost-sensitive, space-constrained applications demanding ruggedness, wide temperature operation, and minimal external components.

FAQ

What is the maximum input voltage for reliable operation?

The L78M12CDT-TR supports a maximum DC input voltage of 35 V for output voltages between 5 V and 18 V. For the 12 V version specifically, this limit applies across its full operating temperature range. Exceeding 35 V risks permanent damage due to internal breakdown, even with thermal protection active.

Does this regulator require input and output capacitors?

While stable operation is possible without external capacitors under ideal conditions, STMicroelectronics specifies a 0.33 µF input capacitor (tantalum or ceramic) and recommends a 0.1 µF output capacitor for optimal transient response and high-frequency noise suppression. Omitting the input capacitor may cause oscillation when connected via long traces to bulk capacitance.

Can L78M12CDT-TR be used in adjustable-voltage configurations?

Yes-though designed as a fixed 12 V regulator, it can serve as the core element in adjustable topologies. By adding external resistors and a feedback network (e.g., using the "circuit for increasing output voltage" in DS0425), output voltages from 7 V to 30 V are achievable. Quiescent current (6 mA) must be included in output current calculations for accuracy.

How does thermal protection behave during overload?

Thermal protection activates when junction temperature exceeds ~165 °C, shutting down the output until the die cools by ~20 °C. This cycle repeats autonomously-preventing catastrophic failure-but causes output voltage interruption. To avoid repeated cycling, ensure adequate heatsinking: with R_thJA = 60 °C/W (TO-220FP), 0.5 A load at 25 °C ambient yields ~105 °C junction rise-well within safe continuous operation if heatsink lowers R_thJA.