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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - Linear, Low Drop Out (LDO) Regulators

STMicroelectronics LK112SM18TR

Name: LK112SM18TR
Brand: STMicroelectronics
SKU: LK112SM18TR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LK112SM18TR

Manufacturer:: STMicroelectronics

Category:: Voltage Regulators - Linear, Low Drop Out (LDO) Regulators

Package:: SC-74A, SOT-753

Datasheet:: LK112SM18TR.pdf

Description:: IC REG LINEAR 1.8V 200MA SOT23-5

Quantity:: RFQ Add To RFQ list

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Inventory:1,322

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Product details

Overview

LK112SM18TR from STMicroelectronics is a 1.8 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 ±2% output voltage accuracy at 25 °C, achieves 500 mV max dropout at full load, and features 30 µVrms output noise (10 Hz–80 kHz) with 0.1 µF bypass capacitor-ideal for powering noise-sensitive analog circuitry in portable instrumentation.

For engineers reviewing the LK112SM18TR datasheet, LK112SM18TR pinout, LK112SM18TR application, or LK112SM18TR equivalent, key selection criteria include its 0.1 µA OFF-mode quiescent current, TTL/CMOS-compatible SHDN input, internal thermal and short-circuit protection, and validated performance across –40 °C to +125 °C junction temperature range.

Technical Context

The LK112SM18TR employs an internal PNP pass transistor to achieve low dropout voltage while maintaining stable regulation under varying line and load conditions. Its shutdown function is controlled via a dedicated SHDN pin compatible with standard logic levels (ON ≥1.8 V, OFF ≤0.6 V), enabling precise system-level power sequencing.

Output noise is actively suppressed using an external 0.1 µF capacitor on the Bypass pin, reducing RMS noise to 30 µV across 10 Hz–80 kHz bandwidth. Internal current limiting and thermal shutdown protect the device during overcurrent or overheating events, with junction temperature capped below 150 °C.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 1.8 V ±2% at 25 °C - ensures stable core supply for low-voltage microcontrollers and RF ICs
Max Dropout Voltage	0.5 V at 200 mA - enables operation from 2.3 V input, supporting single-cell Li-ion or two-cell alkaline systems
Quiescent Current	250 µA max in ON mode, 0.1 µA in OFF mode - extends battery life in always-on sensor nodes and wearables
Output Noise	30 µVrms (10 Hz–80 kHz, 0.1 µF bypass) - meets stringent noise requirements for ADC references and precision op-amps
Input Voltage Range	V_OUT + 0.5 V to 14 V (for V_OUT > 2 V); 2.5 V to 14 V (for V_OUT < 2 V) - supports 1.8 V output from ≥2.5 V sources including USB-adjacent rails
Thermal Shutdown	Activates below 150 °C junction temperature - prevents permanent damage during sustained overload or poor PCB heatsinking
Line Regulation	0.7–20 mV over VI = V_OUT+1 V to V_OUT+6 V - minimizes output drift during battery discharge or upstream converter ripple

Pinout & Package

SOT23-5L surface-mount package with exposed die attach flag for enhanced thermal dissipation (R_thJA = 255 °C/W, R_thJC = 81 °C/W).

Pin/Terminal	Circuit Role	Design Meaning
1 - SHDN	Shutdown control input	Active-high TTL/CMOS-compatible enable; pulls regulator OFF when ≤0.6 V, ON when ≥1.8 V
2 - GND	Ground reference and thermal path	Internally connected to die attach flag to reduce thermal resistance and improve power handling
3 - Bypass	Noise reduction terminal	Accepts 0.1 µF capacitor to suppress broadband output noise to 30 µVrms
4 - OUT	Regulated output	Delivers stable 1.8 V to load; requires ≥2.2 µF ceramic output capacitor for stability
5 - IN	Unregulated input supply	Accepts 2.5–14 V input; requires ≥1 µF ceramic input capacitor near pin

Key Features

Feature	Design Value
Ultra-low OFF-mode IQ	0.1 µA max - enables multi-year battery operation in maintenance-free IoT endpoints
Low-noise architecture	30 µVrms output noise with 0.1 µF bypass - eliminates need for secondary filtering in signal-chain power rails
Integrated protection	Thermal shutdown + current limiting - removes requirement for external fault-handling circuitry
Logic-compatible enable	SHDN pin accepts standard 1.8 V/3.3 V/5 V logic - simplifies interface with MCU GPIO without level-shifting
Wide input range	Operates from 2.5 V to 14 V - accommodates diverse input sources including buck converters, batteries, and industrial rails

Applications

Portable Medical Sensors

Industrial Data Acquisition

Use Scenario: Powering ultra-low-power ECG front-end amplifiers and 24-bit sigma-delta ADCs in handheld diagnostic devices.

IC Role / Device Role / Timing Role: Primary 1.8 V analog supply rail regulator with sub-µA shutdown state for duty-cycled measurement cycles.

Use Value: 30 µVrms noise ensures <1 LSB error in 24-bit conversions; 0.1 µA OFF current enables >5-year shelf life on coin cell.

Use Scenario: Supplying isolated analog input channels in modular PLC I/O modules operating in harsh factory environments.

IC Role / Device Role / Timing Role: Local post-regulator for precision sensor signal conditioning circuits requiring clean, stable 1.8 V bias.

Use Value: ±2% output tolerance and <20 mV line regulation maintain ADC reference integrity despite 24 V DC bus fluctuations.

Wearable Fitness Trackers

Low-Power Wireless Transceivers

Use Scenario: Delivering regulated 1.8 V to MEMS accelerometers, optical heart-rate sensors, and BLE SoCs during active and sleep modes.

IC Role / Device Role / Timing Role: Dual-role power manager: active LDO during sensing, deep-sleep regulator with logic-controlled shutdown.

Use Value: 250 µA ON-mode IQ and 0.1 µA OFF-mode IQ jointly minimize average system current, extending charge cycle by >30%.

Use Scenario: Providing clean 1.8 V supply to RF transceiver ICs (e.g., nRF52840, CC2652R) in battery-powered mesh nodes.

IC Role / Device Role / Timing Role: Low-noise core voltage source decoupled from noisy digital switching domains via Bypass pin.

Use Value: 30 µVrms noise directly improves receiver sensitivity by reducing phase noise-induced EVM degradation.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6219B182MR-G	1.8 V fixed, 200 mA, 350 mV dropout @200 mA, 40 µVrms noise, SOT23-5	Higher dropout and noise; lacks thermal shutdown	Use where cost sensitivity outweighs thermal safety and noise margin
Micrel MIC5205-1.8YM5	1.8 V fixed, 150 mA, 350 mV dropout @150 mA, 30 µVrms noise, SOT23-5	Lower current rating; no shutdown pin; higher ON-mode IQ (45 µA typical)	Use in space-constrained designs where shutdown control is unnecessary and load <150 mA

Compared with XC6219B182MR-G and MIC5205-1.8YM5, the LK112SM18TR uniquely combines 200 mA capability, integrated thermal shutdown, and 0.1 µA OFF-mode IQ-making it optimal for thermally constrained, battery-operated systems requiring robust fault protection and multi-year runtime.

Availability

LK112SM18TR is available at Aetrix Electronics and suitable for portable medical sensors, industrial data acquisition modules, wearable fitness trackers, and low-power wireless transceivers requiring stable component supply with guaranteed long-term availability.

Supply support for LK112SM18TR 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, high PSRR, and robust protection in miniature packages.

FAQ

What is the minimum input voltage required for stable 1.8 V output?

The LK112SM18TR requires a minimum input voltage of 2.5 V due to its V_OUT < 2 V operating condition. This ensures sufficient headroom for regulation even at elevated temperatures or under transient load, avoiding dropout-induced output collapse during battery discharge.

Can the Bypass pin be left unconnected?

No. Leaving the Bypass pin floating degrades output noise performance: without the 0.1 µF capacitor, RMS noise rises significantly above 30 µV. The datasheet specifies this capacitor as mandatory for achieving the rated 30 µVrms noise; omitting it compromises precision analog supply integrity.

Does the SHDN pin require a pull-up resistor?

No external pull-up is required. The SHDN pin has internal logic-level compatibility and draws only 12–35 µA when asserted high. It can be driven directly from MCU GPIO; however, a weak pull-down (e.g., 100 kΩ to GND) is recommended in systems where the driving pin may float during reset to guarantee known OFF-state behavior.

Is the LK112SM18TR qualified for automotive use?

No. ST does not qualify the LK112S series for automotive applications. It is specified for industrial and consumer operation (–40 °C to +125 °C junction), but lacks AEC-Q100 qualification, automotive-grade screening, or extended reliability testing required for vehicle subsystems.

LK112SM18TR Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: SC-74A, SOT-753

Packaging:: Tape & Reel (TR)

Product Status:: Active

Output Configuration:: Positive

Output Type:: Fixed

Number of Regulators:: 1

Voltage - Input (Max):: 14V

Voltage - Output (Min/Fixed):: 1.8V

Voltage - Output (Max):: -

Voltage Dropout (Max):: -

Current - Output:: 200mA

Current - Quiescent (Iq):: 250 µA

Current - Supply (Max):: -

PSRR:: 55dB (400Hz)

Control Features:: Enable

Protection Features:: Over Current, Over Temperature

Operating Temperature:: -40°C ~ 125°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-5

LK112SM18TR FAQ

1.How can I place an order for LK112SM18TR through Aetrix?

Please submit a Request for Quotation (RFQ) for LK112SM18TR on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for LK112SM18TR reliable?

The price and inventory of LK112SM18TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LK112SM18TR is usually 5 days.

3.What payment methods are accepted for LK112SM18TR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LK112SM18TR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LK112SM18TR?

LK112SM18TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LK112SM18TR order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for LK112SM18TR?

For technical support, including LK112SM18TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LK112SM18TR requirements.

6.How does Aetrix verify that LK112SM18TR is sourced from the original manufacturer or authorized distributors?

All LK112SM18TR products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LK112SM18TR meets industry standards.

7.What is the process for return or replacement of LK112SM18TR?

All LK112SM18TR units undergo pre-shipment inspection (PSI). If there is an issue with LK112SM18TR, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The LK112SM18TR part is unused and in its original packaging.

Return procedure for LK112SM18TR:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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