STMicroelectronics LK112M18TR

Overview

LK112M18TR from STMicroelectronics is a 1.8 V fixed-output, low-noise, low-dropout linear 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 µV_rms output noise (10 Hz–80 kHz), and ultra-low quiescent current (0.1 µA in OFF mode, ≤250 µA in ON mode). It is used in battery-powered microcontroller core supplies where stable low-voltage bias and minimal standby power are critical.

For engineers reviewing the LK112M18TR datasheet, LK112M18TR pinout, LK112M18TR application, or LK112M18TR equivalent, key selection criteria include dropout voltage at 150 mA, shutdown leakage (<0.1 µA), output noise performance with 0.1 µF bypass capacitor, thermal shutdown threshold (150 °C), and SOT23-5L package compatibility with space-constrained PCB layouts.

Technical Context

The LK112M18TR implements a TTL/CMOS-compatible shutdown interface (SHDN pin active-high ≥1.8 V) that disables regulation and reduces I_Q to <0.1 µA. Its internal PNP pass element enables operation down to V_IN = V_OUT + 0.5 V for V_OUT > 2 V - here, minimum input is 2.3 V for reliable 1.8 V output.

Output stability is ensured with external 2.2 µF ceramic output capacitor and optional 0.1 µF noise-bypass capacitor on the BYPASS pin. Protection includes internal current limiting, thermal shutdown (T_J < 150 °C), and short-circuit foldback - no external components required for safe operation across –40 °C to +125 °C junction temperature range.

Key Specifications

Pinout & Package

SOT23-5L surface-mount package: 2.95 mm × 1.60 mm footprint, 0.95 mm pitch, 1.45 mm height, with exposed die attach flag connected internally to GND for enhanced thermal dissipation (R_thJA = 255 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6206P182MR and RT9193-18GB, the LK112M18TR uniquely combines sub-0.1 µA shutdown, 30 µV_rms noise with bypass cap, and 350 mV dropout - making it optimal for multi-year battery-powered precision systems where every nanoamp and microvolt matters.

Availability

LK112M18TR is available at Aetrix Electronics and suitable for wearable sensor nodes, IoT edge devices, industrial PLC I/O modules, and medical handheld diagnostics requiring stable component supply with guaranteed long-term manufacturability.

Supply support for LK112M18TR 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 LK112 series belongs to ST's precision low-noise LDO portfolio, engineered specifically for ultra-low-power, noise-sensitive applications such as portable medical devices, battery-operated instrumentation, and always-on sensor hubs.

FAQ

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

The LK112M18TR requires V_IN ≥ V_OUT + 0.5 V = 2.3 V for stable regulation at full load. Below this, dropout occurs and output voltage drops linearly with input. At light loads (<1 mA), regulation may hold down to ~2.15 V, but design margin mandates 2.3 V minimum per datasheet absolute ratings.

Can the BYPASS pin be left unconnected?

Yes, the BYPASS pin may be left floating or unconnected, but doing so increases output noise to ~70 µV_rms (vs. 30 µV_rms with 0.1 µF capacitor). No damage occurs, but noise-sensitive applications like ADC references or RF VCOs will suffer degraded performance without the bypass cap.

Does the LK112M18TR require an input capacitor?

An input capacitor is not mandatory for stability but strongly recommended: 1 µF ceramic placed close to the IN pin reduces high-frequency noise coupling and improves line transient response. Without it, the regulator remains functional but exhibits larger output voltage spikes during input rail disturbances.

How does thermal shutdown behave during continuous overload?

Under sustained overload, the LK112M18TR's thermal shutdown activates at ~150 °C junction temperature, disabling output until T_J falls below ~135 °C (typical hysteresis). This cycle repeats autonomously - no latch-up or manual reset required - protecting both the IC and downstream circuitry from thermal damage.