Texas Instruments LM78M05CH

Overview

LM78M05CH from Texas Instruments is a fixed-output, 3-terminal positive voltage regulator delivering 5 V ±2% at up to 500 mA output current with input voltage range of 7.2 V to 35 V. It integrates thermal shutdown, short-circuit current limiting, and safe-area protection, and is commonly used as a local on-board power supply in motor drives and building automation systems.

For engineers reviewing the LM78M05CH datasheet, LM78M05CH pinout, LM78M05CH application, or LM78M05CH equivalent, key selection considerations include dropout headroom (≥2.2 V), junction-to-ambient thermal resistance (22.6°C/W in TO-220), quiescent current (4–10 mA), and ripple rejection (78 dB at 120 Hz).

Technical Context

The LM78M05CH uses a monolithic silicon Darlington pass transistor with internal feedback control to maintain stable 5-V output across load (5 mA–500 mA) and line (7.2 V–25 V) variations. Its protection circuitry operates autonomously without external components: thermal shutdown activates at ~125°C junction temperature, and current limiting engages before safe-area violation.

It functions in three modes: normal regulation (VO = 5 V), dropout (VO ≈ VIN – VDO, where VDO ≤2.2 V at 500 mA), and self-protection (cyclic current reduction or shutdown during sustained overload). No external capacitors are required for stability, though 0.33 µF input and 0.1 µF output capacitors improve noise filtering and transient response.

Key Specifications

Pinout & Package

LM78M05CH is supplied in TO-220 (NDE) package with 3-pin configuration and metal tab electrically connected to Ground. The tab must be thermally and electrically tied to system ground plane for optimal thermal performance and safety.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78M05CDT/NOPB and UA78M05CKTTR, the LM78M05CH offers superior thermal performance in through-hole systems, direct mechanical heatsink mounting via its TO-220 tab, and proven reliability in legacy industrial designs-making it optimal for cost-sensitive, thermally demanding, or serviceable equipment.

Availability

LM78M05CH is available at Aetrix Electronics and suitable for motor drives, building automation systems, and white goods requiring stable component supply with long lifecycle support and consistent parametric performance.

Supply support for LM78M05CH 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

Texas Instruments is a global semiconductor company headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management technologies since 1930.

The LM78M05CH belongs to TI's legacy linear regulator product line, designed specifically for robust, low-cost, maintenance-free DC power conversion in industrial and consumer equipment where simplicity, reliability, and thermal resilience are prioritized over ultra-low quiescent current or switching efficiency.

FAQ

What is the minimum input voltage required for stable regulation with the LM78M05CH?

The LM78M05CH requires a minimum input voltage of 7.2 V to maintain 5-V regulation at full 500-mA load, per TI's recommended operating conditions. This 2.2-V headroom accounts for worst-case dropout voltage, line regulation error, and temperature drift. Below 7.2 V, output voltage drops linearly with input, entering dropout mode.

Does the LM78M05CH require external capacitors to operate stably?

No, the LM78M05CH is internally compensated and stable without external capacitors. However, TI recommends a 0.33-µF ceramic or tantalum capacitor on the input and a 0.1-µF capacitor on the output to suppress high-frequency noise and improve transient response-especially when the LM78M05CH is located more than 4 inches from the main supply filter.

How does the thermal shutdown feature work in the LM78M05CH?

The LM78M05CH incorporates a monolithic thermal sensor that disables the pass transistor when junction temperature reaches approximately 125°C. Once the die cools below the hysteresis threshold (~110°C), regulation resumes automatically-no external reset or power cycle is needed. This protects against permanent damage during sustained overload or inadequate heatsinking.

Can the LM78M05CH be used in automotive applications?

The LM78M05CH is rated for operation from –40°C to +125°C and supports input transients up to 35 V, meeting basic environmental requirements for under-hood or cabin modules. However, it lacks AEC-Q100 qualification and has no built-in reverse-polarity or load-dump protection-so it must be paired with external TVS diodes and reverse-blocking FETs for full automotive compliance.

What is the purpose of the metal tab on the LM78M05CH package?

The metal tab on the LM78M05CH TO-220 package is electrically connected to Pin 2 (Ground) and serves dual roles: (1) primary thermal conduction path to an external heatsink or copper pour, and (2) low-inductance ground return for high-current paths. It must be insulated from chassis if chassis ground differs from circuit ground, using mica washers or thermal pads with dielectric rating ≥500 V.