STMicroelectronics L78M08CDT-TR

Overview

L78M08CDT-TR from STMicroelectronics is a three-terminal positive fixed-voltage linear regulator delivering 8 V at up to 500 mA output current in TO-220FP (IPAK) package. It features thermal overload protection, short-circuit current limiting, safe operating area (SOA) compensation, and ±4 % output voltage tolerance over 0–150 °C junction temperature range. Used for local on-card regulation in industrial power supplies and embedded control modules where stable low-noise DC bias is required.

For engineers reviewing the L78M08CDT-TR datasheet, L78M08CDT-TR pinout, L78M08CDT-TR application, or L78M08CDT-TR equivalent, key selection criteria include dropout voltage (2 V), load regulation (80 mV max at 5–200 mA), supply voltage rejection (56 dB at 120 Hz), quiescent current (6 mA), and thermal resistance (R_thJC = 5 °C/W).

Technical Context

The L78M08CDT-TR implements a monolithic PNP pass transistor with internal current limiting, thermal shutdown, and SOA protection-enabling robust operation without external protection circuitry. Its architecture supports fixed 8 V output without feedback components, while maintaining stability with minimal external capacitance (0.33 µF input, 0.1 µF output).

It operates across an input voltage range of 10.5–25 V for nominal 8 V output, with guaranteed functionality up to 150 °C junction temperature (C-grade). Dropout voltage remains constant at 2 V across temperature and load, and output voltage drift is –0.5 mV/°C under 5 mA load.

Key Specifications

Pinout & Package

Package: TO-220FP (IPAK), 3-pin vertical mount with isolated tab. Designed for surface-mount assembly with through-hole compatibility and integrated heatsinking via metal tab.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78M08CDT and MC78M08CDTG, the L78M08CDT-TR offers superior supply rejection (56 dB) and lower junction-to-case thermal resistance (5 °C/W), making it optimal for industrial applications demanding tighter regulation under varying line/load conditions and elevated ambient temperatures.

Availability

L78M08CDT-TR is available at Aetrix Electronics and suitable for industrial PLC I/O modules, automotive body control units, medical diagnostic instrumentation, and point-of-sale terminal power management requiring stable component supply with extended temperature capability and proven field reliability.

Supply support for L78M08CDT-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 automotive ICs with strong industrial and automotive qualification programs.

The L78M series belongs to ST's precision 500 mA linear regulator product line, engineered for ruggedized local regulation in harsh environments-emphasizing thermal resilience, fault robustness, and long-term parametric stability over cost-optimized consumer-grade alternatives.

FAQ

What is the maximum input voltage for reliable operation of L78M08CDT-TR?

The absolute maximum DC input voltage is 40 V for VO = 20–24 V configurations, but for the L78M08CDT-TR (8 V output), the rated maximum is 35 V. Operation at 35 V is permitted only with adequate heatsinking and within the 0–150 °C junction temperature limit. Continuous use above 25 V input increases power dissipation and thermal stress-designers should verify junction temperature using R_thJC = 5 °C/W and ambient conditions.

Does L78M08CDT-TR require an output capacitor for stability?

No, the L78M08CDT-TR is internally compensated and stable without an output capacitor. However, adding a 0.1 µF ceramic capacitor at the output significantly improves transient response to load steps (e.g., microcontroller wake-up bursts). The input capacitor (0.33 µF minimum) is mandatory for stability-especially when input traces exceed 5 cm or when sourced from high-impedance supplies like unregulated wall adapters.

How does the L78M08CDT-TR behave during short-circuit events?

Under short-circuit, the device limits output current to approximately 250 mA (typical at 25 °C) and activates thermal shutdown if junction temperature exceeds ~160 °C. Once the fault clears and temperature drops below the hysteresis threshold (~140 °C), regulation resumes automatically. Peak short-circuit current reaches 700 mA briefly before limiting engages-this supports safe handling of capacitive inrush without false triggering.

Can L78M08CDT-TR be used in adjustable-voltage configurations?

Yes-though designed as a fixed 8 V regulator, the L78M08CDT-TR can be adapted for adjustable output using external resistors (e.g., Figure 19 in DS0425). By connecting a resistor divider between output and ground, and feeding the junction to the input of an op-amp referenced to the 8 V rail, outputs from 7 V to 30 V are achievable. This requires careful attention to stability, noise, and load regulation degradation versus the fixed configuration.