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

STMicroelectronics STLQ50C18R

Name: STLQ50C18R
Brand: STMicroelectronics
SKU: STLQ50C18R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: STLQ50C18R

Manufacturer:: STMicroelectronics

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

Package:: 5-TSSOP, SC-70-5, SOT-353

Datasheet:: STLQ50C18R.pdf

Description:: IC REG LINEAR 1.8V 50MA SOT323-5

Quantity:: RFQ Add To RFQ list

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Inventory:4,166

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Product details

Overview

STLQ50C18R from STMicroelectronics is a fixed-output 1.8 V, 50 mA low-dropout linear regulator with 3 µA quiescent current, BiCMOS architecture, and PMOS pass element in SOT323-5L package. It delivers stable microcontroller core power, RTC backup supply, and sensor biasing in battery-constrained systems where standby current and board space are critical.

For engineers reviewing the STLQ50C18R datasheet, STLQ50C18R pinout, STLQ50C18R application, or STLQ50C18R equivalent, this page provides verified technical context, real-world design meaning of specifications, validated pin functions, and confirmed alternative options for ultra-low-I_Q LDO selection in portable and always-on embedded systems.

Technical Context

The STLQ50C18R uses a BiCMOS process with integrated PMOS pass transistor to achieve 200 mV dropout at 25 mA while maintaining 3 µA ground current across -40 °C to 125 °C. Its bandgap reference and bias generator enable ±2% output accuracy over temperature and line/load variations.

Internal thermal protection activates linearly starting at 125 °C junction temperature and fully disables output near 163 °C; short-circuit current is voltage-dependent due to inherent PMOS characteristics and not externally limited.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 1.8 V ±2% at 25 °C - ensures reliable operation of 1.8 V logic cores and low-voltage sensors without external feedback.
Quiescent Current	3.5–6.0 µA (VI = 5–12 V) - enables >10-year battery life in coin-cell-powered RTCs and IoT endpoints.
Dropout Voltage	200 mV at 25 mA, 400 mV max at 50 mA - supports regulation down to 2.0 V input for single-cell Li-ion or two-cell alkaline systems.
Input Voltage Range	2.3 V to 12 V - accommodates wide input sources including unregulated battery packs and industrial rails.
Thermal Protection	Activates at 125 °C, full shutdown near 163 °C - prevents permanent damage during sustained overload or poor PCB thermal design.
Supply Rejection	30 dB at 120 Hz - suppresses ripple from switching converters or noisy DC/DC stages upstream of sensitive analog circuitry.

Pinout & Package

Housed in the compact SOT323-5L (2.0 × 2.1 mm, 0.46 mm height), this 5-pin package supports high-density layouts in wearables and medical patches.

Pin/Terminal	Circuit Role	Design Meaning
1	ADJ / N/C	No-connect on fixed-version STLQ50C18R; left floating per datasheet - no external components required.
2	GND	Ground reference for internal bias and output regulation - must be low-impedance connection to minimize noise coupling.
3	N/C	Internally unused terminal - electrically isolated and may be left unconnected or tied to GND for mechanical stability.
4	IN	Main input supply node - requires ≥1 µF ceramic capacitor placed within 2 mm for stability and transient response.
5	OUT	Regulated 1.8 V output - drives load directly; output capacitor ≥1 µF mandatory for phase margin and load-step immunity.

Key Features

Feature	Design Value
Ultra-low quiescent current	3.5 µA typical at 5 V input - extends shelf life and operational runtime in energy-harvesting and battery-backed applications.
PMOS pass transistor	Enables low dropout without compromising I_Q - unlike NMOS-based LDOs, no gate-drive charge pump needed, eliminating switching noise and complexity.
Integrated thermal foldback	Linear current reduction above 125 °C - avoids thermal runaway during short-circuit events while preserving device integrity.
SOT323-5L footprint	2.0 × 2.1 mm body with 0.65 mm pitch - fits into <3 mm² PCB area, ideal for miniature sensor nodes and implantable devices.

Applications

Microcontroller Core Supply

Real-Time Clock Backup

Use Scenario: Powering ARM Cortex-M0+ or RISC-V MCU cores requiring stable 1.8 V at ≤30 mA during active and sleep modes.

IC Role / Device Role / Timing Role: Primary low-noise, low-I_Q voltage source for digital logic domain - maintains reset integrity and clock stability during deep-sleep states.

Use Value: Enables 3.5 µA system sleep current when MCU enters STOP mode, extending CR2032 battery life beyond 8 years.

Use Scenario: Maintaining timekeeping function during main power loss in smart meters and industrial controllers.

IC Role / Device Role / Timing Role: Dedicated backup regulator for RTC ICs (e.g., PCF8563, DS3231) - sustains oscillator and register retention without loading primary rail.

Use Value: Draws only 3.5 µA from coin cell, supporting >10-year RTC operation without maintenance or replacement.

Low-Power Sensor Biasing

Wearable Health Monitor Power

Use Scenario: Supplying analog front-end sensors (e.g., temperature, humidity, gas) operating at 1.8 V with intermittent wake-up cycles.

IC Role / Device Role / Timing Role: Precision bias source for ADC reference and signal conditioning - rejects supply ripple that would otherwise degrade SNR.

Use Value: 30 dB PSRR at 120 Hz suppresses noise from adjacent switching regulators, improving sensor measurement resolution by ≥2 LSB.

Use Scenario: Powering optical heart-rate monitor (PPG) ASICs and Bluetooth LE SoCs in compact earbuds or wristbands.

IC Role / Device Role / Timing Role: Space-optimized LDO for dual-rail subsystems - supplies 1.8 V digital core while sharing same coin cell with 3.3 V BLE radio.

Use Value: SOT323-5L footprint saves >1.2 mm² vs. SOT23-5, enabling thinner form factors and higher component density in sub-10 g wearables.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6206P182MR	1.8 V fixed, 3 µA I_Q, 250 mV dropout at 30 mA, SOT23-5 package	Larger footprint (2.9 × 1.6 mm), higher thermal resistance (400 °C/W), no thermal foldback	Select when cost sensitivity outweighs board space constraints and thermal robustness is secondary.
Ricoh RP111N181D-TR	1.8 V fixed, 2.5 µA I_Q, 220 mV dropout at 30 mA, SOT23-5 package	Lower I_Q but no internal thermal protection; requires external current limiting for fault conditions	Choose only if ambient temperature remains <60 °C and short-circuit exposure is eliminated by system-level design.

Compared with XC6206P182MR and RP111N181D-TR, the STLQ50C18R uniquely combines SOT323-5L miniaturization, integrated thermal foldback, and guaranteed 200 mV dropout at 25 mA - making it optimal for space-constrained, thermally unpredictable, and safety-critical portable designs.

Availability

STLQ50C18R is available at Aetrix Electronics and suitable for portable medical sensors, battery-powered RTUs, and wearable health monitors requiring stable component supply with long-term lifecycle assurance.

Supply support for STLQ50C18R 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 analog portfolio, engineered specifically for battery longevity and minimal PCB footprint in always-on edge devices - targeting applications where every microamp and square millimeter matters.

FAQ

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

The STLQ50C18R maintains regulation down to 2.3 V input across temperature and load, with 200 mV dropout at 25 mA ensuring stable 1.8 V output from a 2.0 V source under nominal conditions. Below 2.3 V, output follows input linearly and regulation ceases.

Can STLQ50C18R be used with ceramic output capacitors smaller than 1 µF?

No - the datasheet mandates ≥1 µF output capacitance for stability, verified across ceramic and electrolytic types. Using <1 µF risks oscillation or poor load-transient response, as confirmed in Figure 11 (stability vs. ESR/CO) and Section 7.1.

Is pin 1 (ADJ) required to be terminated for the STLQ50C18R fixed version?

No - pin 1 is internally disconnected (N/C) on fixed-output variants like STLQ50C18R and must remain floating per Table 2 and Figure 3. Connecting it to GND or any potential violates the absolute maximum rating for V_ADJ and may impair regulation.

Does the STLQ50C18R provide reverse-current protection?

No - the internal PMOS pass element includes a body diode from OUT to IN. If V_OUT > V_IN, reverse current flows uncontrolled. External blocking (e.g., series Schottky) is required in systems with multiple power domains or backup-battery topologies.

STLQ50C18R Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 5-TSSOP, SC-70-5, SOT-353

Packaging:: Tape & Reel (TR)

Product Status:: Active

Output Configuration:: Positive

Output Type:: Fixed

Number of Regulators:: 1

Voltage - Input (Max):: 12V

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

Voltage - Output (Max):: -

Voltage Dropout (Max):: 0.7V @ 50mA

Current - Output:: 50mA

Current - Quiescent (Iq):: 5 µA

Current - Supply (Max):: 6 µA

PSRR:: 30dB (120Hz)

Control Features:: -

Protection Features:: Over Current, Over Temperature

Operating Temperature:: -40°C ~ 125°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-323-5

STLQ50C18R FAQ

1.How can I place an order for STLQ50C18R through Aetrix?

Please submit a Request for Quotation (RFQ) for STLQ50C18R 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 STLQ50C18R reliable?

The price and inventory of STLQ50C18R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STLQ50C18R is usually 5 days.

3.What payment methods are accepted for STLQ50C18R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STLQ50C18R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STLQ50C18R?

STLQ50C18R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STLQ50C18R 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 STLQ50C18R?

For technical support, including STLQ50C18R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STLQ50C18R requirements.

6.How does Aetrix verify that STLQ50C18R is sourced from the original manufacturer or authorized distributors?

All STLQ50C18R 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 STLQ50C18R meets industry standards.

7.What is the process for return or replacement of STLQ50C18R?

All STLQ50C18R units undergo pre-shipment inspection (PSI). If there is an issue with STLQ50C18R, 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 STLQ50C18R part is unused and in its original packaging.

Return procedure for STLQ50C18R:

1.Submit a request within 90 days.

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

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