STMicroelectronics L4941BDT

Overview

L4941BDT from STMicroelectronics is a 5V fixed-output, very low-dropout (LDO) linear voltage regulator in DPAK package, delivering up to 1A output current with 450mV typical dropout at full load, 4–8mA quiescent current at 5mA load, and integrated thermal shutdown, short-circuit, and reverse-polarity protection. It is designed for battery-powered industrial and consumer equipment where efficiency and reliability under low VIN–VOUT margin are critical.

For engineers reviewing the L4941BDT datasheet, L4941BDT pinout, L4941BDT application, or L4941BDT equivalent, key selection criteria include dropout voltage at 1A, quiescent current vs. load, thermal resistance (RthJA = 100°C/W), reverse polarity tolerance (–15V), and safe-area protection behavior under transient overload.

Technical Context

The L4941BDT employs an internal antisaturation circuit to maintain regulation down to 450mV input-output differential at 1A, enabling operation from as low as 5.45V input when regulating 5V output. Its current-limiting architecture combines foldback and peak-current sensing, while thermal shutdown activates at ~150°C junction temperature with hysteresis for automatic recovery.

Reverse polarity protection operates via internal diode clamping between IN and GND, sustaining –15V input without damage. Output noise is specified at 30µV RMS (100Hz–100kHz), and supply voltage rejection reaches 68dB at 120Hz, degrading to ~40dB above 10kHz - indicating strong low-frequency ripple suppression but limited high-frequency PSRR.

Key Specifications

Pinout & Package

DPAK (TO-252) package: surface-mount, 3-pin, exposed thermal pad (connected to GND), JEDEC standard footprint, RoHS-compliant ECOPACK® with lead-free interconnect.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LD1117S50TR and TLV1117-50CDCYR, the L4941BDT provides superior dropout performance and integrated protection - making it uniquely suited for battery-constrained and field-deployed systems where reliability under electrical abuse is non-negotiable.

Availability

L4941BDT is available at Aetrix Electronics and suitable for portable medical sensors, industrial PLC I/O modules, smart home hubs, and automotive aftermarket telematics requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for L4941BDT 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, analog chips, and MEMS sensors for industrial, automotive, and consumer markets.

The L4941 belongs to ST's legacy linear regulator product line, engineered specifically for high-reliability, low-dropout operation in battery-powered and harsh-environment applications where protection robustness and thermal resilience are prioritized over ultra-low IQ.

FAQ

What is the minimum input voltage required for 5V regulation at 1A load?

The L4941BDT requires a minimum input voltage of 5.45V to sustain 5V output at 1A, based on its 450mV typical dropout voltage. At elevated temperatures or worst-case process corners, dropout may reach 700mV, so 5.7V input is recommended for guaranteed regulation across full operating conditions.

Does the L4941BDT require an output capacitor, and what type is recommended?

Yes - a minimum 22µF low-ESR capacitor is required at the output for stability and transient response. ST specifies ceramic capacitors with ≤100mΩ ESR; tantalum or polymer types are acceptable if ESR falls within 10–100mΩ. Omitting or undersizing this capacitor risks oscillation or poor load-step recovery.

Can the L4941BDT be used in parallel for higher current capability?

No - the L4941BDT is not designed for parallel operation. Its output voltage tolerance (±2%) and lack of current-sharing control make load imbalance likely, risking thermal runaway in one device. For >1A applications, select a higher-current LDO or switch-mode solution instead.

Is the exposed thermal pad on the DPAK package electrically connected, and how should it be handled?

Yes - the exposed pad is internally connected to GND and serves as the primary thermal path. It must be soldered to a dedicated PCB copper pour tied to system ground, with ≥4 thermal vias (0.3mm diameter) connecting to inner-layer ground planes to achieve the rated RthJA = 100°C/W.