STMicroelectronics L4940V12

Overview

L4940V12 from STMicroelectronics is a fixed-output, very low-dropout linear voltage regulator delivering 12 V at up to 1.5 A, featuring 450 mV typical dropout at 1 A, ±2% output voltage accuracy over load/temperature, and integrated reverse polarity protection. It serves as a primary post-regulator in battery-powered industrial controllers, portable instrumentation, and automotive body electronics where input headroom is constrained.

For engineers reviewing the L4940V12 datasheet, L4940V12 pinout, L4940V12 application, or L4940V12 equivalent, key selection criteria include dropout voltage at full load, thermal resistance (R_thJA = 50 °C/W for TO-220), short-circuit current limit (2–2.7 A), quiescent current stability across temperature, and compatibility with low-ESR ceramic output capacitors (22 µF).

Technical Context

The L4940V12 employs an internal antisaturation circuit and safe-area protection to maintain regulation during transient overloads while limiting junction temperature via thermal shutdown. Its architecture supports stable operation with only 0.1 µF input and 22 µF output capacitance, eliminating need for external compensation.

It operates across −40 °C to +150 °C junction temperature range, accepts up to 17 V input at light load, and delivers 55–61 dB supply voltage rejection at 120 Hz under 1 A load-enabling use in noisy environments such as motor control subsystems and automotive power distribution units.

Key Specifications

Pinout & Package

Supplied in TO-220 package (3-pin, vertical mounting, metal tab connected to output) with JEDEC-standard pinout: Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output. Tab is electrically tied to output for direct heatsinking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2940CT-12 and TL783CKC, L4940V12 provides superior battery-life extension via lower dropout, eliminates external protection components through integrated reverse-polarity and thermal shutdown, and delivers tighter output accuracy (±2% vs ±3%) without trimming-making it optimal for space-constrained, safety-critical embedded systems.

Availability

L4940V12 is available at Aetrix Electronics and suitable for industrial PLC I/O modules, automotive body control units, portable test equipment, and medical auxiliary power supplies requiring stable component supply and long-term lifecycle support.

Supply support for L4940V12 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 microcontrollers, power management ICs, sensors, and discrete components for industrial, automotive, and consumer markets.

The L4940 series belongs to ST's legacy linear regulator product line, engineered specifically for battery-powered and low-headroom applications where dropout voltage, quiescent current, and integrated protection are critical-not general-purpose replacement for older 78xx regulators.

FAQ

What is the minimum input voltage required for L4940V12 to maintain regulation at 1.5 A?

The minimum input voltage is 12.5 V, calculated as V_OUT + V_d(max) = 12 V + 0.9 V (per Table 7, V_d = 500–900 mV at 1.5 A). Below this, output voltage collapses linearly with input; regulation is guaranteed only above 12.5 V at full load.

Can L4940V12 operate without an output capacitor?

No. The datasheet mandates ≥22 µF low-ESR output capacitance (ceramic or tantalum) for stability. Omitting it causes oscillation and thermal runaway due to phase margin loss in the internal error amplifier loop-verified in Figure 26 (load transient response) and Section 6 (Typical Application).

Does L4940V12 require a heatsink in TO-220 package at 1.5 A continuous load?

Yes, for ambient temperatures above 50 °C. With R_thJA = 50 °C/W and P_D ≈ (12.5 V − 12 V) × 1.5 A = 0.75 W, junction temperature rise is 37.5 °C. At 70 °C ambient, T_J = 107.5 °C-within 150 °C limit-but derating is recommended above 60 °C ambient per Figure 25 (Total power dissipation).

Is L4940V12 qualified for automotive applications per AEC-Q100?

No. ST does not list L4940V12 in its AEC-Q100 qualified portfolio. It is rated for industrial temperature range (−40 to +150 °C junction) but lacks automotive-specific stress testing, failure analysis reporting, and PPAP documentation-use L4940V12Q (if available) or automotive-grade alternatives like TLE4275 for vehicle platforms.