STMicroelectronics L4940D2T10

Overview

L4940D2T10 from STMicroelectronics is a fixed +10 V, 1.5 A low-dropout linear voltage regulator in D2PAK package, featuring 500 mV typical dropout at 1.5 A, ±2% output voltage accuracy over load/temperature, and integrated thermal shutdown, short-circuit, and reverse-polarity protection. It serves as a primary post-regulator in battery-powered industrial controllers and embedded power rails where stable 10 V supply with minimal input headroom is required.

For engineers reviewing the L4940D2T10 datasheet, L4940D2T10 pinout, L4940D2T10 application, or L4940D2T10 equivalent, key selection criteria include dropout voltage at full load, quiescent current under light/no load, thermal resistance (R_thj-case = 3 °C/W), reverse polarity tolerance (–15 V), and guaranteed short-circuit current (2.0–2.7 A).

Technical Context

The L4940D2T10 employs an internal antisaturation circuit and safe-area protection to sustain 1.5 A output while limiting junction temperature rise during overload. Its architecture delivers stable regulation across input voltages from 11.7 V to 17 V with line regulation ≤8 mV and load regulation ≤35 mV over 5 mA–1.5 A.

Thermal performance is defined by R_thj-case = 3 °C/W and R_thj-amb = 62.5 °C/W in D2PAK, enabling ≥1.2 W continuous dissipation on a 2-layer PCB without heatsink. Output impedance is 40 mΩ at 120 Hz, supporting fast transient response in distributed supply architectures with upstream switching preregulators.

Key Specifications

Pinout & Package

D2PAK (TO-263) package: surface-mount, single-row 3-terminal outline with exposed thermal pad (pin 2) for enhanced heat transfer. Dimensions per STMicroelectronics mechanical drawing P011P6G: 9.15 mm × 10.2 mm × 4.5 mm, 15 mm lead length.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV1117-10CP and LD1086DT10R, the L4940D2T10 uniquely combines 1.5 A output, 500 mV dropout, D2PAK thermal performance, and –15 V reverse tolerance - making it the only option for high-current, battery-critical, or fault-resilient 10 V regulation.

Availability

L4940D2T10 is available at Aetrix Electronics and suitable for industrial motor control, portable test equipment, automotive body electronics, and programmable logic controller I/O requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for L4940D2T10 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 post-regulation in battery-powered and thermally constrained systems where protection integration and thermal efficiency are prioritized over ultra-low quiescent current.

FAQ

What is the minimum input voltage required for stable 10 V output at 1.5 A?

The L4940D2T10 requires a minimum input voltage of 11.7 V to maintain 10 V output at 1.5 A load, based on its 500 mV typical dropout voltage. At 25°C junction temperature and with adequate PCB copper area, operation down to 11.5 V is possible but not guaranteed across temperature and process variation.

Does the D2PAK thermal pad require solder connection to PCB ground plane?

Yes - the exposed thermal pad (pin 2) is electrically connected to V_OUT and must be soldered to a dedicated copper pour tied to the 10 V output net. This provides both electrical continuity and primary thermal conduction; omitting this connection degrades R_thj-amb by >20 °C/W and risks thermal shutdown under load.

Can L4940D2T10 replace L4940V10 in existing TO-220 designs?

No - although both deliver 10 V, the L4940D2T10 uses D2PAK packaging with different pinout (input–output–ground vs. TO-220's input–ground–output) and thermal interface requirements. Direct replacement requires PCB layout revision, thermal pad routing, and verification of input capacitance placement near the new footprint.

Is external capacitor compensation required for stability?

No - the L4940D2T10 is internally compensated and stable with standard 0.1 µF input and 22 µF output ceramic or tantalum capacitors, as specified in ST's test circuits. ESR of the output capacitor must remain between 0.1 Ω and 10 Ω; values outside this range may cause oscillation or poor transient response.