STMicroelectronics LK112M40TR

Overview

LK112M40TR from STMicroelectronics is a low-noise, low-dropout linear voltage regulator with integrated shutdown control and internal PNP pass transistor. It delivers up to 150 mA output current with 350 mV dropout at full load, 30 µVrms output noise (10 Hz–80 kHz), and supports 4.0 V fixed output voltage. It operates from input voltages as low as VOUT + 0.5 V (≥2 V versions) and features TTL/CMOS-compatible shutdown logic - used in battery-powered sensor nodes and portable instrumentation requiring stable, ultra-low-noise bias.

For engineers reviewing the LK112M40TR datasheet, LK112M40TR pinout, LK112M40TR application, or LK112M40TR equivalent, key selection criteria include its 0.1 µA shutdown quiescent current, 0.35 V max dropout at 150 mA, 30 µVrms noise performance with 0.1 µF bypass capacitor, thermal shutdown at <150 °C, and SOT23-5L package compatibility for space-constrained designs.

Technical Context

The LK112M40TR implements a PNP-based LDO architecture enabling low dropout and high PSRR (55 dB at 400 Hz). Its shutdown pin accepts TTL/CMOS logic levels (ON ≥1.8 V, OFF ≤0.6 V), directly disabling regulation and reducing quiescent current to ≤0.1 µA. Internal current limiting and thermal protection activate under overcurrent or junction temperature >150 °C.

Output voltage stability is maintained across load (±30 mV from 1–60 mA) and line (±20 mV over VIN = VOUT+1 V to VOUT+6 V). The Bypass pin accepts a 0.1 µF capacitor to reduce broadband output noise to 30 µVrms, while the GND pin is internally connected to the die attach flag to minimize thermal resistance (RthJA = 255 °C/W).

Key Specifications

Pinout & Package

SOT23-5L surface-mount package (2.95 × 1.60 mm, 0.95 mm pitch), thermally enhanced with GND connected to die attach flag (RthJA = 255 °C/W, RthJC = 81 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with AP2204K-4.0TRG1 and MCP1703T-4002E/MB, the LK112M40TR uniquely combines sub-0.35 V dropout, 30 µVrms noise with bypass support, and integrated thermal/current protection - making it optimal for space- and noise-constrained applications where reliability under overload is critical.

Availability

LK112M40TR is available at Aetrix Electronics and suitable for portable medical sensors, industrial process transmitters, and wireless sensor nodes requiring stable component supply with guaranteed long-term manufacturability and consistent parametric performance.

Supply support for LK112M40TR 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 LK112 series belongs to ST's precision linear regulator product line, engineered specifically for ultra-low-noise, low-quiescent-current applications in battery-operated and signal-integrity-sensitive systems.

FAQ

What is the minimum input voltage required for regulation at 4.0 V output?

The LK112M40TR requires a minimum input voltage of VOUT + 0.5 V = 4.5 V for stable regulation at full 150 mA load. At lighter loads (e.g., 10 mA), regulation is maintained down to ~4.2 V, but datasheet guarantees apply only above 4.5 V. Below this, dropout behavior increases and output voltage may sag.

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 µVrms output noise. Omitting it results in typical noise rising to ~120 µVrms, compromising analog signal fidelity.

Does the LK112M40TR support reverse polarity protection?

No - the device lacks internal reverse-voltage protection. Applying reverse polarity (e.g., negative VIN relative to GND) can damage the internal PNP pass transistor and ESD structures. External protection, such as a series Schottky diode or ideal diode controller, is required in systems prone to reverse connection.

How does thermal shutdown behave during sustained overload?

When junction temperature exceeds 150 °C, the internal thermal shutdown circuit disables the pass transistor, dropping output voltage to near zero. After cooling below ~135 °C (typical hysteresis), the device automatically recovers regulation without external intervention - providing self-protecting operation during intermittent overloads.