STMicroelectronics LK112SM17TR

Overview

LK112SM17TR from STMicroelectronics is a low-noise, low-dropout linear voltage regulator with shutdown control, delivering up to 200 mA output current at a fixed 1.7 V output. It features a maximum dropout voltage of 500 mV at full load, quiescent current as low as 0.1 µA in OFF mode, and output noise of 30 µV_rms (10 Hz–80 kHz) when using the bypass capacitor. It operates from input voltages as low as V_OUT + 0.5 V (≥2 V versions) and integrates thermal and short-circuit protection - ideal for battery-powered sensor nodes and portable medical monitors.

For engineers reviewing the LK112SM17TR datasheet, LK112SM17TR pinout, LK112SM17TR application, or LK112SM17TR equivalent, key selection criteria include its 1.7 V fixed output, SOT23-5L package footprint, TTL/CMOS-compatible SHDN logic interface, ultra-low OFF-mode current, and verified noise performance with 0.1 µF Bypass capacitor placement.

Technical Context

The LK112SM17TR uses an internal PNP pass transistor to achieve low dropout and stable regulation across input voltages from 2.2 V to 14 V. Its shutdown function accepts logic-level inputs (ON ≥1.8 V, OFF ≤0.6 V), enabling precise system power sequencing in multi-rail embedded designs.

Output noise is actively reduced via an external 0.1 µF capacitor on the dedicated Bypass pin, lowering RMS noise to 30 µV in the 10 Hz–80 kHz band. Internal protection includes thermal shutdown (T_J < 150 °C) and current limiting that disables the output during overcurrent or short-circuit events.

Key Specifications

Pinout & Package

Supplied in the compact, surface-mount SOT23-5L package (2.95 mm × 1.60 mm × 1.30 mm), optimized for space-constrained PCB layouts and automated assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6219B172MR-G and RT9193-17GB, the LK112SM17TR uniquely combines 200 mA drive, 30 µV_rms noise via integrated Bypass pin, and 0.1 µA shutdown current - making it optimal for ultra-low-power, high-fidelity analog systems where every nanoamp and microvolt matters.

Availability

LK112SM17TR is available at Aetrix Electronics and suitable for wearable health monitors, industrial sensor nodes, portable diagnostic devices, and low-power IoT edge controllers requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for LK112SM17TR 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 LK112S series was developed specifically for ultra-low-power, noise-sensitive applications in portable and battery-operated equipment - emphasizing minimal quiescent current, low dropout, and integrated noise suppression without external complexity.

FAQ

What is the minimum input voltage required for regulation at 1.7 V output?

The LK112SM17TR requires a minimum input voltage of 2.2 V - defined as V_OUT + 0.5 V per datasheet Section 4, since its output is >2 V. Operation below this voltage results in dropout, where output tracks input minus dropout voltage (as low as 170 mV at light load).

Can the Bypass pin be left unconnected?

No - leaving the Bypass pin floating degrades noise performance. The datasheet specifies a 0.1 µF ceramic capacitor must be placed between Bypass and GND to achieve the rated 30 µV_rms output noise. Omitting it increases noise to typical values above 100 µV_rms.

Does the LK112SM17TR require an input capacitor?

Yes - a minimum 1 µF ceramic capacitor is required at the IN pin, as specified in Section 4 of the datasheet. This stabilizes the input impedance, prevents oscillation during transient load changes, and mitigates noise coupling from upstream power sources.

Is the SHDN pin internally pulled up or down?

The SHDN pin has no internal pull-up or pull-down resistor. It must be actively driven to ≥1.8 V for ON operation or ≤0.6 V for OFF mode. Leaving it floating may result in undefined regulator state and unpredictable current draw due to input leakage paths.