STMicroelectronics LK112SM32TR

Overview

LK112SM32TR from STMicroelectronics is a low-noise, low-dropout linear voltage regulator with shutdown control, delivering 3.3 V at up to 200 mA output current. It features 500 mV max dropout at full load, 30 µVrms output noise (10 Hz–80 kHz), ±2% output voltage tolerance at 25 °C, and operates from input voltages as low as VOUT + 0.5 V (≥3.8 V) or 2.5 V (for VOUT < 2 V). It is used in battery-powered sensor nodes and portable instrumentation requiring stable, ultra-low-quiescent-power regulation.

For engineers reviewing the LK112SM32TR datasheet, LK112SM32TR pinout, LK112SM32TR application, or LK112SM32TR equivalent, key selection criteria include shutdown logic compatibility (TTL/CMOS), thermal performance in SOT23-5L, bypass-capacitor-dependent noise reduction, and internal current/thermal protection behavior under fault conditions.

Technical Context

The LK112SM32TR integrates an internal PNP pass transistor enabling low-dropout operation and uses a dedicated Bypass pin for external 0.1 µF capacitor connection to suppress thermal noise. Its shutdown input (SHDN) accepts TTL/CMOS logic levels: high ≥1.8 V enables regulation; low ≤0.6 V disables output and reduces quiescent current to ≤0.1 µA.

It includes internal short-circuit and thermal foldback protection-junction temperature is limited below 150 °C, and output current is actively monitored. Electrical characteristics are specified across –40 °C to +125 °C operating junction temperature, with line regulation of ≤20 mV and load regulation of ≤90 mV over full output current range.

Key Specifications

Pinout & Package

LK112SM32TR is housed in a compact, surface-mount SOT23-5L package with exposed die attach flag for improved thermal conduction. Pin 2 (GND) is internally connected to this flag to reduce thermal resistance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS7A2033PDBVR and MCP1700T-3302E/MB, the LK112SM32TR uniquely balances ultra-low OFF-mode current, dedicated noise-reduction pin, and integrated thermal/current protection-making it optimal for battery-powered analog-digital hybrid systems needing both longevity and signal integrity.

Availability

LK112SM32TR is available at Aetrix Electronics and suitable for portable medical sensors, industrial data loggers, automotive body control modules, and smart home motion detectors requiring stable component supply with consistent parametric performance and long-term manufacturability.

Supply support for LK112SM32TR 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, sensors, and analog products 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 robustness, and analog signal integrity.

FAQ

What is the minimum input voltage required for stable 3.3 V output?

The LK112SM32TR requires a minimum input voltage of VOUT + 0.5 V = 3.8 V for stable regulation at full load. For light loads or elevated temperatures, headroom may increase slightly due to dropout voltage drift; datasheet specifies 0.5 V max at 200 mA and 25 °C. Below 3.8 V, output voltage drops linearly with input.

Can the BYPASS pin be left floating or tied directly to GND?

No-leaving the BYPASS pin floating degrades noise performance to >100 µVrms, and tying it to GND disables the internal reference bypass path entirely. The pin must be connected to a 0.1 µF ceramic capacitor between BYPASS and GND to achieve the specified 30 µVrms noise; X7R or C0G dielectrics are recommended.

Does the LK112SM32TR support reverse polarity or reverse current protection?

No-the device has no built-in reverse polarity or reverse current protection. If input voltage can fall below output (e.g., during shutdown), an external Schottky diode from IN to OUT is required to prevent reverse current flow through the pass transistor, which could damage the IC or discharge backup capacitors.

How does thermal shutdown behave during sustained overload?

Under sustained overload, the LK112SM32TR enters thermal shutdown when junction temperature reaches ~150 °C, disabling output and reducing quiescent current. It remains latched off until junction temperature falls by ~15–20 °C, then automatically recovers. This hysteresis prevents rapid cycling and provides safe cooldown time before re-enabling regulation.