STMicroelectronics L4940V10

Overview

L4940V10 from STMicroelectronics is a fixed-output, very low-dropout linear voltage regulator delivering 10 V at up to 1.5 A, featuring 450 mV typical dropout at 1 A, ±2% output voltage accuracy (9.6–10.4 V over load/line), and integrated thermal shutdown, short-circuit, and reverse-polarity protection. It is designed for battery-powered industrial and consumer systems where input-to-output headroom is constrained.

For engineers reviewing the L4940V10 datasheet, L4940V10 pinout, L4940V10 application, or L4940V10 equivalent, key selection criteria include dropout voltage under full load, quiescent current at light load (5–8 mA), output voltage drift (1 mV/°C), supply voltage rejection (56–62 dB at 120 Hz), and TO-220 package thermal resistance (R_thJA = 50 °C/W).

Technical Context

The L4940V10 employs an internal antisaturation circuit and safe-area protection to sustain 1.5 A output while limiting junction temperature via thermal shutdown. Its architecture uses a PNP pass transistor with on-chip current limiting, enabling stable regulation even with marginal input margins.

It operates across –40 °C to +150 °C junction temperature, supports input voltages up to 17 V (for 5 mA load) and requires only 0.1 µF input and 22 µF output capacitance for stability. Reverse polarity protection activates below –15 V input, preventing damage during incorrect battery connection.

Key Specifications

Pinout & Package

Supplied in TO-220 package (3-lead, vertical mounting, metal tab connected to output), with pin 1 = Input, pin 2 = Ground, pin 3 = Output. The metal tab is electrically tied to the output terminal and serves as primary heat path.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2940CT-10 and MCP1703T-1002E/MB, the L4940V10 uniquely combines 1.5 A capability, 450 mV dropout, reverse polarity protection, and TO-220 thermal performance-making it irreplaceable in ruggedized 10 V battery or industrial supply designs requiring robustness at full load.

Availability

L4940V10 is available at Aetrix Electronics and suitable for portable medical monitors, industrial PLC I/O modules, automotive telematics, and smart energy meters requiring stable component supply, long-lifecycle availability, and consistent parametric performance across production batches.

Supply support for L4940V10 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 sensing solutions for industrial, automotive, and consumer markets.

The L4940 series belongs to ST's legacy linear regulator product line, engineered specifically for high-reliability, low-dropout DC-DC conversion in battery-constrained and thermally demanding environments.

FAQ

What is the minimum input voltage required for L4940V10 to maintain regulation at 1.5 A?

The L4940V10 requires a minimum input voltage of 11.5 V to sustain 10 V output at 1.5 A, based on its 500 mV typical dropout voltage. At 1.5 A, dropout may reach 900 mV under worst-case conditions, so 11.9 V input ensures margin. Operation below 11.7 V risks dropout and output collapse.

Can L4940V10 be used without a heatsink in a 50 °C ambient environment?

Yes - with TO-220 package and R_thJA = 50 °C/W, the L4940V10 dissipates up to 1.5 W at full load (10 V × 1.5 A = 15 W output, but power loss = (V_IN−10 V) × 1.5 A). At 12 V input, loss is 3 W; junction rise = 3 W × 50 °C/W = 150 °C → exceeds 150 °C max. So heatsink required above ~11.5 V input at full load.

Does L4940V10 require specific output capacitor ESR for stability?

No - the L4940V10 is internally compensated and stable with standard aluminum or tantalum capacitors ≥22 µF. Unlike some LDOs, it does not specify minimum ESR; low-ESR ceramics may cause instability unless combined with a small series resistor (~0.1 Ω) or used with ≥10 µF bulk + ceramic parallel.

Is L4940V10 qualified for automotive applications per AEC-Q100?

No - the L4940V10 is not AEC-Q100 qualified. ST classifies it for industrial and consumer use. For automotive applications, ST recommends the AEC-Q100 qualified L4940CD10 (D2PAK) variant, which shares electrical specs but undergoes extended reliability testing and has tighter parametric screening.