STMicroelectronics LK112SM50TR

Overview

LK112SM50TR from STMicroelectronics is a 5.0 V fixed-output, low-noise, low-dropout linear voltage regulator with shutdown control in SOT23-5L package. It delivers up to 200 mA output current, maintains ≤500 mV dropout at full load, achieves 30 µV_rms output noise (10 Hz–80 kHz), and draws only 250 µA quiescent current in active mode-ideal for battery-powered sensor nodes and portable instrumentation requiring stable, quiet 5 V supply.

For engineers reviewing the LK112SM50TR datasheet, LK112SM50TR pinout, LK112SM50TR application, or LK112SM50TR equivalent, key selection criteria include its 5.0 V fixed output, 0.1 µA shutdown current, ±2% output tolerance at 25 °C, thermal/overcurrent protection, and TTL/CMOS-compatible SHDN input-critical for ultra-low-power always-on subsystems.

Technical Context

The LK112SM50TR uses an internal PNP pass transistor to achieve low dropout while maintaining high PSRR (55 dB at 400 Hz) and tight line/load regulation (≤40 mV and ≤90 mV respectively). Its shutdown function operates with logic-level compatible thresholds: ON above 1.8 V, OFF below 0.6 V on the SHDN pin.

Thermal protection limits junction temperature to <150 °C; short-circuit current is internally limited to 200 mA. The Bypass pin accepts a 0.1 µF capacitor to reduce output noise to 30 µV_rms, confirming its role in precision analog and RF-bias applications where noise floor matters.

Key Specifications

Pinout & Package

Package: SOT23-5L - surface-mount, 5-pin, thermally enhanced plastic package with die attach flag connected to GND for improved heat dissipation (R_thJA = 255 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS7A2050PDBVR and MCP1700T-5002E/TT, the LK112SM50TR offers balanced trade-offs: best-in-class noise (30 µV_rms) with robust 500 mV dropout and integrated thermal/current protection - ideal for industrial and medical edge sensors needing reliability and signal integrity.

Availability

LK112SM50TR is available at Aetrix Electronics and suitable for portable medical sensors, industrial data loggers, wireless sensor nodes, and test & measurement probes requiring stable component supply across extended production lifecycles.

Supply support for LK112SM50TR 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, designing and manufacturing microcontrollers, power management ICs, sensors, and analog components for industrial, automotive, and consumer markets.

The LK112S series was developed specifically for ultra-low-power, low-noise linear regulation in space-constrained portable and battery-operated equipment - emphasizing shutdown efficiency, thermal resilience, and noise-sensitive analog compatibility.

FAQ

What is the minimum input voltage required for stable 5.0 V output at 200 mA?

The LK112SM50TR requires a minimum input voltage of 5.5 V to maintain regulation at 200 mA load, based on its maximum dropout voltage of 500 mV. Below this, output voltage drops linearly with input; operation below 5.5 V is not guaranteed to sustain 5.0 V output under full load.

Can the Bypass pin be left unconnected?

Yes, the Bypass pin may be left floating or unconnected, but doing so results in higher output noise - approximately 100 µV_rms instead of the specified 30 µV_rms. For noise-sensitive applications like precision ADCs or RF biasing, a 0.1 µF ceramic capacitor must be placed between BYPASS and GND.

Does the LK112SM50TR require input or output capacitance for stability?

Yes - the datasheet specifies 1 µF input capacitance (CI) and 2.2 µF output capacitance (CO) with X5R/X7R dielectric for guaranteed stability. Using smaller or inappropriate dielectrics (e.g., NP0/C0G only on output) may cause oscillation or degraded transient response, especially under load steps.

Is the SHDN pin internally pulled up or down?

No internal pull-up or pull-down exists on the SHDN pin. It must be actively driven: connect to MCU GPIO or logic rail for controlled enable/disable. Leaving it floating risks undefined state - potentially causing intermittent regulator disable or excessive leakage through the input protection network.