STMicroelectronics STLQ50C50R

Overview

STLQ50C50R from STMicroelectronics is a fixed-output 5.0 V, 50 mA low-dropout linear regulator with 3 µA quiescent current, BiCMOS architecture, and PMOS pass element-designed for ultra-low-power battery-backed systems including real-time clocks and microcontroller standby rails. It operates from 2.3 V to 12 V input, delivers 200 mV dropout at 25 mA, and is housed in SOT323-5L.

For engineers reviewing the STLQ50C50R datasheet, STLQ50C50R pinout, STLQ50C50R application, or STLQ50C50R equivalent, key selection criteria include quiescent current vs. load, dropout behavior across temperature, thermal protection activation threshold, and compatibility with 1 µF ceramic output capacitors in space-constrained portable designs.

Technical Context

The STLQ50C50R uses a BiCMOS process with an integrated PMOS pass transistor, enabling sub-µA-level ground current while maintaining stable regulation under light loads. Its bandgap reference and bias generator are optimized for minimal current draw across -40 °C to 125 °C junction temperature.

Unlike NMOS-based LDOs, the PMOS topology eliminates reverse-current risk when VO > VI but requires external protection if backfeed is possible. Thermal foldback begins at ~125 °C and fully disables output near 163 °C, with no latch-off-requiring system-level overtemperature coordination.

Key Specifications

Pinout & Package

Housed in the compact SOT323-5L package (2.0 × 2.1 mm footprint, 0.9 mm height), the STLQ50C50R uses a 5-pin configuration with Pin 1 unconnected on fixed-voltage variants. The package supports high-density PCB layouts and meets ECOPACK® environmental compliance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6206P502MR, STLQ50C50R adds thermal foldback and SOT323-5L pin separation for better layout control; versus ADM7172, it trades 9 µA higher IQ for 70% smaller footprint and 40% lower BOM cost in sub-50 mA applications.

Availability

STLQ50C50R is available at Aetrix Electronics and suitable for portable medical sensors, industrial RTU backup power, and smart meter RTC rails requiring stable component supply with guaranteed long-term manufacturability and RoHS-compliant sourcing.

Supply support for STLQ50C50R 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 devices for industrial, automotive, and consumer markets.

The STLQ50 series belongs to ST's ultra-low-power linear regulator product line, engineered specifically for battery longevity in always-on, intermittent-load applications such as real-time clocks, wearable biosensors, and remote monitoring endpoints.

FAQ

What is the minimum input voltage required for regulation at 5.0 V output?

The STLQ50C50R maintains regulation down to 2.3 V input, but usable 5.0 V output requires VIN ≥ VO + VDROP. At 25 mA load and 25 °C, dropout is 200 mV-so minimum functional input is 5.2 V. Below that, output voltage drops linearly with input.

Can STLQ50C50R be used with ceramic output capacitors smaller than 1 µF?

No. The datasheet specifies ≥1 µF ceramic or electrolytic output capacitance for stability (Figure 11). Using <1 µF risks oscillation due to insufficient phase margin-verified via load transient response testing at 1 µs current step edges.

Does the device support reverse current blocking when output voltage exceeds input?

Yes. The integrated PMOS pass transistor inherently blocks reverse current flow from OUT to IN, eliminating need for external blocking diodes-confirmed by absence of reverse leakage in Table 5 and block diagram topology.

Is thermal protection latched or auto-recovering?

Thermal protection is not latched-it applies linear current foldback starting at ~125 °C and reduces output to zero near 163 °C. Once junction temperature falls below activation threshold, regulation resumes automatically without reset or external intervention.