STMicroelectronics LK112SM27TR

Overview

LK112SM27TR from STMicroelectronics is a low-noise, low-dropout linear voltage regulator with shutdown control, delivering 2.7 V at up to 200 mA output current. It features a maximum dropout voltage of 500 mV at full load, 30 µV_rms output noise (10 Hz–80 kHz), ±2% output voltage tolerance at 25 °C, and operates from input voltages as low as V_OUT + 0.5 V (for V_OUT > 2 V). It is used in battery-powered sensor nodes requiring stable, ultra-low-quiescent-power regulation.

For engineers reviewing the LK112SM27TR datasheet, LK112SM27TR pinout, LK112SM27TR application, or LK112SM27TR equivalent, key selection criteria include shutdown logic compatibility (TTL/CMOS), thermal performance in SOT23-5L, bypass capacitor dependency for noise reduction, and internal current/thermal protection behavior under fault conditions.

Technical Context

The LK112SM27TR employs an internal PNP pass transistor to achieve low dropout and high PSRR (55 dB at 400 Hz). Its shutdown input (SHDN) accepts logic-high ≥1.8 V to enable regulation and logic-low ≤0.6 V to disable, reducing quiescent current to ≤0.1 µA.

It integrates overcurrent and thermal shutdown protection, limiting junction temperature to <150 °C and disabling output during short-circuit events. Output stability requires external capacitors: 1 µF on IN, 2.2 µF on OUT, and 0.1 µF on BYPASS to achieve specified 30 µV_rms noise performance.

Key Specifications

Pinout & Package

The LK112SM27TR is housed in a RoHS-compliant SOT23-5L package with exposed die attach flag for enhanced thermal dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6219B272MR-G and MIC5205-2.7YM5, the LK112SM27TR uniquely combines 200 mA capability, 0.1 µA shutdown current, and integrated shutdown logic in SOT23-5L-making it optimal for energy-constrained systems requiring autonomous power sequencing.

Availability

LK112SM27TR is available at Aetrix Electronics and suitable for wearable health monitors, industrial wireless transmitters, automotive cabin sensors, and smart meter analog domains requiring stable component supply with guaranteed long-term availability.

Supply support for LK112SM27TR 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 silicon solutions for automotive, industrial, and consumer markets.

The LK112S series targets ultra-low-power, noise-sensitive portable and embedded applications where extended battery life and precision analog performance are essential.

FAQ

What is the minimum input voltage required for LK112SM27TR to regulate 2.7 V output?

The LK112SM27TR requires a minimum input voltage of V_OUT + 0.5 V = 3.2 V when V_OUT > 2 V. This is specified in the datasheet's "Operative input voltage" section and confirmed by dropout voltage testing: at 200 mA load, dropout is ≤500 mV, so 3.2 V input sustains regulation at full rated current.

Can the Bypass pin be left unconnected?

No. Leaving the Bypass pin floating degrades output noise performance to >100 µV_rms. The datasheet specifies a 0.1 µF ceramic capacitor must be placed between Bypass and GND to achieve the rated 30 µV_rms noise. No internal bypass capacitance exists - the external capacitor is mandatory for low-noise operation.

Does LK112SM27TR require input and output capacitors for stability?

Yes. The datasheet mandates a 1 µF ceramic capacitor on IN and a 2.2 µF ceramic capacitor on OUT, placed as close as possible to their respective pins. These are required for loop stability, transient response, and PSRR performance - omission risks oscillation or excessive overshoot during load steps.

How does the thermal shutdown behave during sustained overload?

When junction temperature exceeds 150 °C, the internal thermal shutdown circuit disables the output until the die cools below ~135 °C hysteresis threshold. During shutdown, quiescent current remains ≤0.1 µA. This cycle repeats autonomously - no latch-up occurs, and normal operation resumes once thermal limits are restored.