STMicroelectronics L78L09ACD13TR

Overview

L78L09ACD13TR from STMicroelectronics is a three-terminal positive linear voltage regulator delivering a fixed 9 V output at up to 100 mA, featuring internal current limiting, thermal overload protection, and short-circuit protection. It requires no external components, supports input voltages up to 30 V (for VO = 9 V), and operates across 0–125 °C junction temperature. It is used for local on-card regulation in industrial control modules to suppress noise and distribution losses.

For engineers reviewing the L78L09ACD13TR datasheet, L78L09ACD13TR pinout, L78L09ACD13TR application, or L78L09ACD13TR equivalent, this device serves as a drop-in replacement for Zener/resistor regulators with lower quiescent current (6 mA typ.), improved line/load regulation (±150 mV max), and enhanced supply voltage rejection (37–44 dB).

Technical Context

The L78L09ACD13TR implements a monolithic series pass transistor architecture with built-in thermal shutdown and foldback current limiting. Its regulation loop maintains stable 9 V output despite input variations from 11.5 V to 23 V and load changes from 1 mA to 100 mA.

It achieves 70 µV RMS output noise (10 Hz–100 kHz) and 1.7 V dropout voltage at 40 mA, enabling use in low-noise analog subsystems and battery-powered instrumentation where headroom is constrained.

Key Specifications

Pinout & Package

Supplied in SO-8 package with pins 2, 3, 6, and 7 internally connected to the die attach flag for enhanced thermal performance (R_thJC = 20 °C/W). The package footprint matches standard SO-8 but provides lower thermal resistance when mounted on ≥6 cm² copper pour.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78L09ACZ/NOPB and MC78L09ACP, the L78L09ACD13TR offers superior thermal performance in SO-8, tighter output tolerance, and higher PSRR-making it optimal for industrial and medical applications demanding long-term stability and low noise.

Availability

L78L09ACD13TR is available at Aetrix Electronics and suitable for industrial PLCs, medical sensor modules, automotive body controllers, and smart meter designs requiring stable component supply with guaranteed long-term manufacturability.

Supply support for L78L09ACD13TR 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 analog, MCU, power, and sensing solutions for industrial, automotive, and consumer markets.

The L78L series belongs to ST's legacy linear regulator product line, engineered specifically for robust, low-cost, no-compromise fixed-voltage regulation in harsh environments where reliability and ease of use are critical.

FAQ

What is the minimum input voltage required for stable 9 V output?

The L78L09ACD13TR requires a minimum input voltage of 10.7 V to maintain regulation at full 100 mA load, based on its 1.7 V dropout voltage specification. At lighter loads (e.g., 40 mA), input can be as low as 10.7 V; for worst-case design, allow ≥11.5 V per datasheet test conditions.

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

No-L78L09ACD13TR is not designed for parallel operation. Its output voltage tolerance (±4%) and lack of current-sharing circuitry cause unequal load distribution, risking thermal runaway. For >100 mA, use an external pass transistor configured per Figure 14 in DS0424.

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

Yes. The L78L09ACD13TR uses STMicroelectronics' ECOPACK2-compliant SO-8 package, meeting RoHS Directive 2011/65/EU and REACH SVHC requirements, with lead-free matte tin terminations and halogen-free molding compound.

How does thermal performance compare between SO-8 and TO-92 versions?

In SO-8 (L78L09ACD13TR), R_thJA is 55 °C/W with 6 cm² copper; in TO-92 (e.g., L78L09ACZ), it is 200 °C/W. At 100 mA and 20 V input, SO-8 junction rise is ~110 °C vs. ~320 °C for TO-92-making SO-8 viable for continuous full-load operation with minimal heatsinking.