STMicroelectronics L78L18CD13TR

Overview

L78L18CD13TR from STMicroelectronics is a fixed-output +18 V, 100 mA positive voltage regulator in SO-8 package with ±8% output tolerance, thermal overload protection, short-circuit protection, and no external components required. It delivers stable local regulation for microcontroller power rails, sensor interfaces, and industrial I/O modules where low quiescent current (6.5 mA typ.) and 120 µV RMS output noise are critical.

For engineers reviewing the L78L18CD13TR datasheet, L78L18CD13TR pinout, L78L18CD13TR application, or L78L18CD13TR equivalent, this device serves as a drop-in replacement for legacy 78L18 variants in space-constrained PCBs requiring robust DC/DC conversion without external pass transistors or compensation networks.

Technical Context

The L78L18CD13TR implements a monolithic three-terminal linear regulator architecture with internal current limiting, thermal shutdown, and output short-circuit protection. Its SO-8 package features pins 2, 3, 6, and 7 internally connected to the die attach flag for enhanced thermal performance (R_thJA = 55 °C/W with 6 cm² copper pour).

It operates across an input voltage range of 22–33 V to maintain regulated +18 V output under load currents up to 100 mA, with dropout voltage fixed at 1.7 V and supply voltage rejection of 33–38 dB at 120 Hz. The device supports junction temperatures from 0 to 125 °C and requires only 0.33 µF input and 0.1 µF output ceramic capacitors.

Key Specifications

Pinout & Package

SO-8 package with exposed die attach flag (pins 2, 3, 6, 7 internally tied); footprint compatible with standard SO-8 but optimized for thermal dissipation via PCB copper area.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78L18ACZ/NOPB and MC78L18CP, the L78L18CD13TR offers superior thermal management in compact designs, higher maximum junction temperature (125 °C vs. 105–125 °C), and lower output noise-making it optimal for high-reliability industrial and medical applications where PCB real estate and thermal headroom are constrained.

Availability

L78L18CD13TR is available at Aetrix Electronics and suitable for industrial sensor nodes, PLC I/O modules, medical diagnostic interfaces, and test & measurement front-ends requiring stable component supply with full traceability and lifecycle continuity.

Supply support for L78L18CD13TR 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 L78L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-sensitive, space-constrained applications demanding ruggedness, simplicity, and guaranteed performance without external compensation.

FAQ

What is the minimum input voltage required for stable 18 V output?

The L78L18CD13TR requires a minimum input voltage of 19.7 V to maintain regulation at full 100 mA load, based on its 1.7 V dropout specification. At light loads (<10 mA), operation down to 18.5 V is possible, but design margin should include worst-case tolerance and ripple-ST recommends ≥22 V for reliable performance across temperature and line variations.

Can this regulator be used in parallel to increase output current?

No-L78L18CD13TR is not designed for parallel operation. Its internal current limiting and thermal shutdown mechanisms are not matched between units, risking current hogging and premature shutdown. For >100 mA, ST recommends using a single higher-current regulator (e.g., L7818CD2T) or adding an external pass transistor per Figure 14 in DS0424.

Is the SO-8 package lead-free and RoHS-compliant?

Yes-L78L18CD13TR carries ST's ECOPACK2 certification, confirming compliance with RoHS Directive 2011/65/EU and halogen-free material content. The SO-8 body uses matte tin plating over copper leadframe, with peak reflow temperature rated to 260 °C per JEDEC J-STD-020.

Does this part require input/output capacitors, and what values are mandatory?

Yes-ST mandates a 0.33 µF ceramic capacitor at the input (within 10 mm of Pin 1) and a 0.1 µF ceramic capacitor at the output (within 5 mm of Pin 3) for stability and transient response. Larger bulk capacitance may be added externally, but these two ceramics are non-optional per DS0424 Section 4.1 and Figure 3 test circuits.