STMicroelectronics STLQ50C25R

Overview

STLQ50C25R from STMicroelectronics is a fixed-output 2.5 V, 50 mA low-dropout linear regulator in SOT323-5L package, featuring 3 µA quiescent current, 200 mV dropout at 25 mA, and operation from 2.3 V to 12 V input. It uses a PMOS pass element for ultra-low power consumption and thermal protection, targeting microcontroller core supply and real-time clock backup in portable battery-powered systems.

For engineers reviewing the STLQ50C25R datasheet, STLQ50C25R pinout, STLQ50C25R application, or STLQ50C25R equivalent, key selection criteria include quiescent current vs. load regulation, dropout behavior across temperature, thermal shutdown threshold, and compatibility with 1 µF ceramic output capacitors in space-constrained designs.

Technical Context

The STLQ50C25R implements a BiCMOS architecture with an internal bandgap reference (1.222 V), bias generator, and PMOS pass transistor - enabling stable 2.5 V output without external feedback components. Its fixed-voltage version internally connects the ADJ pin to GND, eliminating external resistor networks.

Thermal protection operates linearly: output voltage begins decreasing at ~125 °C junction temperature and drops to zero near 163 °C. The device lacks reverse-current blocking - if VO exceeds VI, uncontrolled backfeed occurs through the intrinsic PMOS body diode, requiring external mitigation in bidirectional power paths.

Key Specifications

Pinout & Package

Supplied in the compact SOT323-5L surface-mount package (2.0 × 2.1 mm footprint, 0.9 mm height), optimized for PCB area-constrained portable applications. Pin 3 is not connected; Pin 1 is NC on fixed versions (ADJ internally tied to GND).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-quiescent-current LDO applications.

Compared with XC6206P252MR and MIC5205-2.5YM5, STLQ50C25R delivers superior thermal resilience and 5× lower quiescent current than MIC5205, enabling decade-long operation on primary cells - critical for sealed medical or industrial telemetry devices.

Availability

STLQ50C25R is available at Aetrix Electronics and suitable for portable medical monitors, battery-powered sensor nodes, microcontroller core supplies, and real-time clock backup systems requiring stable component supply across multi-year production cycles.

Supply support for STLQ50C25R 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 silicon solutions for automotive, industrial, and consumer markets since 1987.

The STLQ50 series belongs to ST's ultra-low-power linear regulator product line, engineered specifically for extended-battery-life applications where quiescent current and thermal robustness are primary constraints - not general-purpose regulation.

FAQ

What is the maximum allowable input voltage for STLQ50C25R?

The absolute maximum DC input voltage is +14 V, but functional operation is specified from 2.3 V to 12 V. Exceeding 12 V may degrade long-term reliability or trigger thermal shutdown under load. For continuous operation, keep VI ≤ 12 V with adequate derating margin based on ambient temperature and power dissipation calculations.

Can STLQ50C25R be used with ceramic output capacitors smaller than 1 µF?

No - the datasheet mandates ≥1 µF ceramic or electrolytic output capacitance for stability, verified in Figure 11. Using <1 µF risks oscillation or poor transient response, especially under load steps. Minimum ESR should be <5 Ω; X5R/X7R dielectrics are recommended for temperature stability.

Does STLQ50C25R provide reverse-voltage or reverse-current protection?

No - the internal PMOS pass transistor includes a body diode with cathode at IN and anode at OUT. If VO > VI (e.g., during hot-swap or backup battery activation), uncontrolled reverse current flows from OUT to IN. An external Schottky diode or ideal diode controller is required to block reverse conduction.

How does thermal protection behave under sustained short-circuit conditions?

Thermal protection initiates linear current foldback starting at 125 °C junction temperature, reducing output voltage gradually until it reaches 0 V near 163 °C. However, this is not instantaneous - rapid overloads can exceed safe power limits before thermal response engages. External current limiting or fusing is advised for applications prone to frequent shorts.