STMicroelectronics L78M09CDT-TR

Overview

L78M09CDT-TR 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 protection. It features ±4 % output voltage tolerance (C version), 2 V dropout voltage, and operates across 0 to 150 °C junction temperature range - used for local on-card regulation in industrial power supplies and embedded control modules.

For engineers reviewing the L78M09CDT-TR datasheet, L78M09CDT-TR pinout, L78M09CDT-TR application, or L78M09CDT-TR equivalent, key selection criteria include guaranteed 500 mA output under thermal constraints, input voltage support up to 40 V, 56 dB supply ripple rejection at 120 Hz, and compatibility with standard TO-220FP heatsinking solutions.

Technical Context

This device implements a monolithic series pass transistor architecture with internal current limiting, thermal shutdown, and SOA compensation - enabling robust operation without external protection circuitry. Its fixed 9 V output is stabilized via on-chip bandgap reference and error amplifier, with load regulation of ≤90 mV over 5–200 mA and line regulation of ≤50 mV across 12–25 V input range.

The TO-220FP package provides 5 °C/W junction-to-case thermal resistance, allowing ≥0.5 A continuous output when mounted on ≥10 cm² copper area or standard heatsink. Input bypassing with ≥0.33 µF low-ESR capacitor is required for stability with long trace lengths, while output capacitance improves transient response but is not mandatory for stability.

Key Specifications

Pinout & Package

TO-220FP (3-lead, full-pack, insulated tab) package with vertical mounting orientation and integrated heatsink pad. Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output - compatible with standard TO-220 footprint but with plastic insulation between tab and collector (Pin 2).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM7809CDT and MC78M09BDTG, L78M09CDT-TR offers superior thermal performance (5 °C/W J-C), extended temperature capability (0–150 °C), and insulated-tab safety - making it optimal for high-reliability industrial and automotive applications requiring robust thermal management and regulatory compliance.

Availability

L78M09CDT-TR is available at Aetrix Electronics and suitable for industrial PLCs, automotive body controllers, medical infusion pumps, and point-of-sale terminals requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for L78M09CDT-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.

L78M09CDT-TR belongs to the L78M precision 500 mA regulator product line, engineered for cost-effective, robust local regulation in harsh environments where reliability, thermal resilience, and regulatory compliance are critical.

FAQ

What is the maximum input voltage for L78M09CDT-TR?

The absolute maximum DC input voltage is 40 V for VO = 20 V or 24 V configurations, and 35 V for VO = 5–18 V. For L78M09CDT-TR (9 V output), the rated maximum input is 35 V - exceeding this risks permanent damage even with thermal protection active.

Does L78M09CDT-TR require an input capacitor?

Yes - a minimum 0.33 µF low-ESR capacitor (tantalum, ceramic, or film) is required between Pin 1 and Pin 2 if the regulator is located more than 10 cm from the main filter capacitor. This prevents oscillation and ensures stability under dynamic load conditions.

Can L78M09CDT-TR be used in adjustable configurations?

Yes - by adding external resistors and diodes per Figure 19 and Figure 20 in DS0425, it can generate adjustable outputs from 7 V to 30 V or function as a constant-current source. However, accuracy and regulation degrade compared to fixed-voltage operation due to added component tolerances and temperature drift.

How does the TO-220FP package differ from standard TO-220?

TO-220FP features a fully insulated metal tab (electrically isolated from Pin 2), enabling direct mounting to grounded heatsinks without insulating hardware. Standard TO-220 has a conductive tab tied to Pin 2 (Ground), requiring mica washers or thermal pads for isolation - increasing thermal resistance by 1–3 °C/W.