STMicroelectronics L78L09ACZ-TR

Overview

L78L09ACZ-TR 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 shutdown, and short-circuit protection. It requires no external components, supports input voltages up to 30 V (for 9 V output), and exhibits ±4% output tolerance (A-grade) with 70 µV RMS output noise over 10 Hz–100 kHz - ideal for local regulation in microcontroller power domains and sensor signal conditioning circuits.

For engineers reviewing the L78L09ACZ-TR datasheet, L78L09ACZ-TR pinout, L78L09ACZ-TR application, or L78L09ACZ-TR equivalent, this device serves as a robust, drop-in replacement for legacy Zener-resistor regulators in low-noise, space-constrained 9 V rail designs where quiescent current (6 mA typ. at 25 °C), dropout voltage (1.7 V), and supply voltage rejection (37–44 dB at 120 Hz) are critical selection criteria.

Technical Context

The L78L09ACZ-TR implements a monolithic series-pass regulator architecture with built-in foldback current limiting and thermal overload protection, enabling self-recovery after fault conditions without external circuitry. Its internal bandgap reference and error amplifier maintain stable 9 V output across load currents from 1 mA to 100 mA and junction temperatures from 0 °C to 125 °C.

It operates with a minimum input-to-output differential of 1.7 V (dropout), supports input voltages from 11.5 V to 23 V for nominal 9 V regulation, and achieves line regulation of ≤150 mV and load regulation of ≤40 mV under specified test conditions - confirming suitability for noisy or variable-input industrial and automotive subsystems.

Key Specifications

Pinout & Package

Supplied in TO-92 package (3-pin, through-hole), with standardized pinout: Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output. The package uses epoxy-molded plastic construction, rated for operating junction temperature up to 125 °C and storage range of –65 °C to +150 °C.

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 L78L09ACZ-TR offers superior output accuracy (±4% vs. ±5%), lower noise (70 µV vs. ≥90 µV), and guaranteed 100 mA delivery across its full temperature range - making it the preferred choice for precision, high-reliability 9 V regulation.

Availability

L78L09ACZ-TR is available at Aetrix Electronics and suitable for industrial sensor nodes, automotive body control modules, medical diagnostic devices, and POS terminal peripheral interfaces requiring stable component supply with consistent parametric performance across production batches.

Supply support for L78L09ACZ-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 analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The L78L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-effective, robust local regulation in space-constrained PCBs where simplicity, reliability, and minimal external components are prioritized over ultra-low quiescent current or adjustable output.

FAQ

What is the maximum input voltage for L78L09ACZ-TR?

The absolute maximum DC input voltage is 30 V when regulating 9 V output, as specified in Table 1 of DS0424 Rev 30. Operation above 23 V is permitted only for transient conditions; continuous operation should remain within 11.5–23 V to ensure specified line regulation (≤150 mV) and thermal safety.

Does L78L09ACZ-TR require input and output capacitors?

Yes - ST recommends a minimum 0.33 µF ceramic capacitor at the input and 0.1 µF ceramic capacitor at the output, placed as close as possible to the device pins. These capacitors ensure stability, improve transient response, and reduce high-frequency noise, as validated in the test circuits on page 3 of DS0424.

Can L78L09ACZ-TR be used in automotive applications?

Yes - the L78L09ACZ-TR (AC grade) is qualified for 0 °C to 125 °C junction temperature operation and features thermal shutdown and short-circuit protection. It is commonly deployed in non-safety-critical automotive body electronics, though it does not carry AEC-Q100 qualification and is not rated for engine bay use.

How does the TO-92 package affect thermal performance?

In TO-92, the L78L09ACZ-TR has R_thJA = 200 °C/W (no heatsink) and R_thJC = 15 °C/W. With 6 cm² of 2-oz copper on the PCB connected to Pin 2 (GND), effective R_thJA drops to ~55 °C/W, allowing ~0.5 W continuous dissipation - sufficient for 100 mA at 1.7 V dropout (0.17 W) with margin.