STMicroelectronics L79L08ACD13TR

Overview

L79L08ACD13TR from STMicroelectronics is a fixed-output, three-terminal negative linear voltage regulator delivering -8 V at up to 100 mA, featuring internal current limiting, thermal shutdown, and short-circuit protection. It requires no external components and is optimized for local on-card regulation in noise-sensitive analog and mixed-signal circuits, such as industrial sensor signal conditioning and legacy RS-232 power rails.

For engineers reviewing the L79L08ACD13TR datasheet, L79L08ACD13TR pinout, L79L08ACD13TR application, or L79L08ACD13TR equivalent, key selection criteria include guaranteed -8 V output tolerance (±5%), dropout voltage of 1.7 V, low 6 mA quiescent current at 25 °C, and TO-92 package thermal performance with R_thJA = 200 °C/W (unmounted).

Technical Context

The L79L08ACD13TR implements a monolithic PNP pass transistor architecture with built-in thermal overload and short-circuit foldback protection. Its regulation loop maintains output stability across input voltages from -10.5 V to -23 V and load currents from 1 mA to 100 mA, with line regulation of 125 mV and load regulation of 40 mV over specified conditions.

It operates over an ambient temperature range of 0 to 125 °C (L79LxxAC grade), supports capacitor-stabilized operation with only 0.33 µF input and 0.1 µF output ceramic capacitors, and achieves 37–45 dB supply voltage rejection at 120 Hz - critical for rejecting ripple in dual-rail analog supplies.

Key Specifications

Pinout & Package

Supplied in TO-92 package (ECOPACK® compliant), with 3.3 mm body width, 4.95 mm height, and 2.67 mm lead pitch. The package uses standard through-hole mounting and provides adequate thermal performance for ≤350 mW dissipation without heatsinking.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar negative linear regulator applications.

Compared with LM7908CDT/NOPB and MC79L08ACDR2G, the L79L08ACD13TR offers superior noise performance (60 µV vs. ≥75 µV) and tighter SVR consistency (37–45 dB), making it preferred for precision analog signal chains where negative rail purity directly impacts measurement fidelity.

Availability

L79L08ACD13TR is available at Aetrix Electronics and suitable for industrial sensor interfaces, legacy serial communication modules, analog audio preamplifiers, and embedded microcontroller analog peripherals requiring stable component supply and long-term obsolescence management.

Supply support for L79L08ACD13TR 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 sensor solutions for industrial, automotive, and consumer markets.

The L79L series belongs to ST's legacy linear regulator product line, engineered specifically for cost-sensitive, space-constrained applications requiring robust, no-frills negative voltage regulation with intrinsic protection and minimal external components.

FAQ

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

The L79L08ACD13TR requires a minimum input voltage of -9.7 V to maintain regulation under full 100 mA load, based on its 1.7 V dropout specification. At lighter loads (<10 mA), input as low as -9.0 V may suffice, but design margins should assume -9.7 V to ensure compliance across temperature and process variation.

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

No - the L79L08ACD13TR lacks current-sharing capability and has no provision for master-slave synchronization. Attempting parallel operation risks thermal runaway due to mismatched output voltages and unbalanced current distribution. For >100 mA, use a single higher-current regulator like the LM7912 or add an external pass transistor.

Is a heat sink required for continuous 100 mA operation?

A heat sink is not required for continuous 100 mA operation at ambient temperatures ≤50 °C, given the TO-92 package's 200 °C/W R_thJA and 1.7 V dropout (max dissipation ≈ 170 mW). However, above 50 °C ambient or in enclosed enclosures, a small copper pour (≥6 cm²) is recommended to limit junction temperature below 125 °C.

Does this part support ceramic output capacitors?

Yes - the L79L08ACD13TR is stable with ceramic output capacitors as low as 0.1 µF, per ST's test circuit in the datasheet. Unlike older regulators, it does not require ESR-based damping, enabling compact, low-ESR, high-reliability filtering without tantalum or aluminum electrolytic components.