STMicroelectronics L4940V5

Overview

L4940V5 from STMicroelectronics is a 5 V, 1.5 A fixed-output low-dropout linear voltage regulator in TO-220 package, featuring 450 mV typical dropout at 1 A, ±2% output voltage accuracy over load/temperature, and integrated thermal shutdown, short-circuit, and reverse-polarity protection. It enables efficient battery-powered industrial sensors and portable instrumentation where input-to-output differential is constrained.

For engineers reviewing the L4940V5 datasheet, L4940V5 pinout, L4940V5 application, or L4940V5 equivalent, key selection criteria include dropout voltage at full load, quiescent current under light-load conditions, thermal resistance (R_thJA = 50 °C/W), and compatibility with standard 0.1 µF input / 22 µF output capacitor networks.

Technical Context

The L4940V5 employs a PNP pass transistor architecture with internal anti-saturation circuitry to minimize saturation voltage and sustain regulation down to 450 mV input–output differential at 1 A. Its feedback loop maintains output stability across 5 mA–1.5 A load range without external compensation.

Protection functions are fully autonomous: thermal shutdown activates at ~150 °C junction temperature; short-circuit current limits to 2.2–2.9 A depending on input voltage; reverse-polarity protection blocks conduction when input is inverted relative to ground, preventing damage during board-level assembly or field service.

Key Specifications

Pinout & Package

TO-220 package (3-pin, vertical mounting, metal tab connected to output). Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output (tab). Standard dual-gauge outline per ST DocID2141 Rev 14, Section 8.1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2940CT-5.0 and MCP1700T-5002E/MB, the L4940V5 delivers superior dropout performance, robust protection features, and higher output current-making it the preferred choice for demanding 5 V point-of-load regulation in automotive, industrial, and portable equipment.

Availability

L4940V5 is available at Aetrix Electronics and suitable for portable medical sensors, industrial PLC I/O modules, and automotive body control units requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for L4940V5 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 L4940 series belongs to ST's high-reliability linear regulator product line, engineered specifically for industrial and automotive applications demanding robust fault protection, wide input voltage tolerance, and stable operation under thermal stress.

FAQ

What is the minimum input voltage required for the L4940V5 to maintain regulation at 1.5 A?

The L4940V5 requires a minimum input voltage of 5.9 V to sustain 5 V output at 1.5 A, based on its maximum dropout voltage of 900 mV (per Table 4). At 1.5 A, dropout ranges from 500–900 mV depending on junction temperature and input conditions-designers must ensure VI ≥ VO + V_d(max) across worst-case operating conditions.

Can the L4940V5 operate without an output capacitor?

No. The L4940V5 requires a minimum 22 µF aluminum or tantalum output capacitor (or equivalent low-ESR ceramic) for stability, as specified in Section 7 Application Circuits and Figure 27 of the datasheet. Omitting it causes oscillation and potential device failure due to phase margin loss in the internal feedback loop.

Is the metal tab on the TO-220 package electrically connected, and if so, to which pin?

Yes-the metal tab on the L4940V5 TO-220 package is internally connected to Pin 3 (Output), as confirmed in ST's mechanical drawings (Figure 28) and pin configuration diagram (Figure 2). This requires electrical isolation from chassis ground unless the output rail is referenced to system ground.

How does the L4940V5 handle reverse input voltage, and what is the absolute maximum rating?

The L4940V5 incorporates reverse-polarity protection that blocks conduction when input is negative relative to ground. Absolute maximum reverse input voltage is –15 V (with VO = 5 V and RO = 100 Ω), per Table 2. Beyond this, internal junction breakdown may occur-external series diode is recommended for systems subject to >–15 V transients.