STMicroelectronics L78M12ACDT-TR

Overview

L78M12ACDT-TR from STMicroelectronics is a three-terminal positive linear voltage regulator delivering a precise 12 V output at up to 500 mA, featuring ±2 % output voltage tolerance, thermal overload protection, and short-circuit protection. It operates across an extended 0 °C to 125 °C junction temperature range and uses a DPAK (TO-252) package for compact board-level power regulation in industrial control modules.

For engineers reviewing the L78M12ACDT-TR datasheet, L78M12ACDT-TR pinout, L78M12ACDT-TR application, or L78M12ACDT-TR equivalent, key selection criteria include guaranteed output accuracy over temperature, dropout voltage of 2 V at 25 °C, ripple rejection of 55 dB at 120 Hz, quiescent current of 6 mA, and safe-area protection enabling robust local regulation without external current limiting.

Technical Context

This device implements a monolithic series-pass transistor architecture with internal current limiting, thermal shutdown, and output safe-area compensation-preventing destruction under sustained overload or short-circuit conditions. Its fixed-output design eliminates external feedback components while supporting adjustable configurations via external resistors.

The L78M12ACDT-TR is optimized for low-noise, medium-current applications requiring stable DC biasing: output noise is 75 µV RMS (10 Hz–100 kHz), load regulation is 120 mV over 5–200 mA, and line regulation is 30 mV across 16–30 V input variation at 200 mA load.

Key Specifications

Pinout & Package

The L78M12ACDT-TR is housed in a surface-mount DPAK (TO-252) package with exposed thermal pad for enhanced heat dissipation. Thermal resistance is 8 °C/W junction-to-case and 100 °C/W junction-to-ambient (no heatsink).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78M12CDT-TR, the L78M12ACDT-TR delivers tighter voltage accuracy and lower noise for analog-sensitive designs; compared with MC78M12BDTG, it trades wide-temperature capability for improved output stability and lower quiescent current in industrial ambient ranges.

Availability

L78M12ACDT-TR is available at Aetrix Electronics and suitable for industrial PLC I/O modules, automotive body control units, medical patient monitor front-ends, and point-of-sale terminal power management requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for L78M12ACDT-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, Switzerland, designing and manufacturing silicon solutions for automotive, industrial, and consumer markets since 1987.

The L78MxxAC series belongs to ST's precision linear regulator product line, engineered specifically for industrial applications demanding guaranteed accuracy, extended temperature operation, and intrinsic fault protection without external components.

FAQ

What is the minimum input voltage required for stable 12 V output at 500 mA?

The L78M12ACDT-TR requires a minimum input voltage of 14.5 V under full-load conditions (5–350 mA) per Table 9 in the datasheet. At 25 °C and 500 mA, the dropout voltage is 2 V, so 14 V is theoretically sufficient-but ST specifies 14.5 V to guarantee regulation across temperature and process variation. Input below this causes output collapse.

Can this regulator be used in adjustable-output configurations?

Yes-the L78M12ACDT-TR can be configured as an adjustable regulator using external resistors, as shown in Figure 18 of the datasheet. The output voltage becomes VO = V_REF × (1 + R2/R1), where V_REF is the internal bandgap reference (~12 V for this part). However, accuracy degrades due to resistor tolerance and temperature drift; fixed-output mode is recommended for precision applications.

Does the DPAK package require a heatsink for 500 mA continuous operation?

At 500 mA with 12 V output and 24 V input (12 V drop), power dissipation is 6 W. With R_thJA = 100 °C/W, junction temperature rise would exceed 600 °C-impossible without heatsinking. In practice, the internal thermal shutdown activates well before that. For continuous 500 mA, a copper pour ≥4 cm² with thermal vias to inner layers is mandatory; forced air or external heatsink is strongly advised.

How does the L78M12ACDT-TR handle reverse input voltage or output backfeed?

The device has no reverse-voltage or reverse-current protection. Applying negative voltage to the input pin or forcing voltage onto the output pin (e.g., from a backup battery) may cause latch-up or permanent damage. External protection-such as a series Schottky diode on the input or a blocking diode on the output-is required in systems where these conditions can occur.