STMicroelectronics L78L08ABUTR

Overview

L78L08ABUTR from STMicroelectronics is a fixed +8 V, 100 mA positive voltage regulator in SOT-89 package, featuring thermal overload protection, short-circuit current limiting, and ±4% output voltage tolerance (A-grade) over –40°C to +125°C operating junction temperature. It requires no external components and delivers low-noise regulation for local power conditioning in microcontroller peripherals, sensor interfaces, and industrial I/O modules.

For engineers reviewing the L78L08ABUTR datasheet, L78L08ABUTR pinout, L78L08ABUTR application, or L78L08ABUTR equivalent, this device serves as a drop-in replacement for legacy Zener/resistor regulators-offering lower quiescent current (6 mA typ.), improved line/load regulation (125 mV/40 mV), and higher PSRR (37–45 dB at 120 Hz) in space-constrained designs.

Technical Context

The L78L08ABUTR employs monolithic bipolar technology with internal current limiting and thermal shutdown circuitry, enabling robust operation without external protection components. Its architecture integrates a precision bandgap reference, error amplifier, and series pass transistor in a single die.

Designed for fixed-output local regulation, it operates with input voltages from 10.5 V to 23 V (min dropout 1.7 V), supports capacitive bypassing with standard 0.33 µF input and 0.1 µF output ceramic capacitors, and maintains stable regulation across load currents from 1 mA to 100 mA and ambient temperatures from –40°C to +125°C.

Key Specifications

Pinout & Package

SOT-89 package: 3-pin surface-mount plastic package with exposed die attach pad for enhanced thermal dissipation (R_thJA = 55°C/W with 6 cm² copper pour). Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM78L08ACZ/NOPB and TL78L08ACDR, the L78L08ABUTR offers superior thermal resilience (–40°C to +125°C), tighter tolerance (±4%), lower noise (60 µV vs. ≥80 µV), and fully integrated protection-making it the preferred choice for mission-critical embedded power rails.

Availability

L78L08ABUTR is available at Aetrix Electronics and suitable for industrial sensor interfaces, automotive body control modules, microcontroller power rails, and IoT edge node power management requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for L78L08ABUTR 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-effective, robust local DC-DC conversion in space- and reliability-constrained embedded systems-emphasizing simplicity, protection integration, and wide-temperature operability.

FAQ

What is the minimum input voltage required for stable 8 V output from the L78L08ABUTR?

The L78L08ABUTR requires a minimum input voltage of 9.7 V to maintain regulation at full 100 mA load, based on its 1.7 V maximum dropout voltage specification. At lighter loads (e.g., 40 mA), input can be as low as 9.7 V; for guaranteed operation across temperature and process variation, ST recommends ≥10.5 V input per datasheet test conditions.

Can the L78L08ABUTR be used in parallel to increase output current?

No-parallel operation is not recommended due to mismatch in output voltage tolerances (±4%) and lack of current-sharing circuitry. Uneven current distribution may cause thermal runaway in one device. For >100 mA, use a higher-current regulator (e.g., L7808CD2T) or add an external pass transistor per Figure 14 in the datasheet.

Does the SOT-89 package require a thermal pad connection to PCB ground?

Yes-the SOT-89 package features an exposed die attach flag (Pin 2 internally connected to GND) that must be soldered to a minimum 6 cm² copper pour tied to the system ground plane. This reduces R_thJA from 200°C/W to 55°C/W and is essential to sustain 100 mA output at elevated ambient temperatures.

How does the L78L08ABUTR's PSRR compare to switching regulators at 120 Hz?

At 120 Hz, the L78L08ABUTR provides 37–45 dB PSRR-significantly higher than typical buck converters (20–30 dB at same frequency)-making it ideal for rejecting rectified AC ripple before sensitive analog stages. However, its PSRR rolls off above 1 kHz, so it should be used downstream of, not instead of, a switching pre-regulator in mixed-signal systems.