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

STMicroelectronics LD39015M125R

Name: LD39015M125R
Brand: STMicroelectronics
SKU: LD39015M125R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LD39015M125R

Manufacturer:: STMicroelectronics

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

Package:: SC-74A, SOT-753

Datasheet:: LD39015M125R.pdf

Description:: IC REG LIN 1.25V 150MA SOT23-5

Quantity:: RFQ Add To RFQ list

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Product details

Overview

LD39015M125R from STMicroelectronics is a 150 mA ultra-low-noise, low-quiescent-current LDO voltage regulator delivering a fixed 1.25 V output with ±2.0% accuracy at 25 °C, 80 mV typical dropout at 100 mA, and 29 µVRMS output noise (1.1–100 kHz) without bypass capacitor - designed for power-sensitive RF and analog circuitry in portable devices.

For engineers reviewing the LD39015M125R datasheet, LD39015M125R pinout, LD39015M125R application, or LD39015M125R equivalent, key selection criteria include guaranteed 150 mA load capability, logic-controlled shutdown (<1 µA OFF current), ceramic-capacitor stability (C_OUT = 1 µF), thermal/short-circuit protection, and operation across –40 °C to 125 °C junction temperature.

Technical Context

The LD39015M125R employs a bandgap reference trimmed to 1.22 V with internal resistor divider (R1/R2) to set its precise 1.25 V output. Its enable-controlled NMOS pass transistor architecture enables fast 30 µs turn-on time and sub-1 µA shutdown current.

It achieves 65 dB PSRR at 1 kHz but rolls off above 10 kHz; noise performance is optimized via internal compensation - no external bypass capacitor required for 29 µVRMS noise at 1.25 V output - and remains stable with 1 µF ceramic output capacitance across full load and temperature range.

Key Specifications

Parameter	Value and Actual Design Meaning
Output voltage	Fixed 1.25 V ±2.0% @ 25 °C - ensures accurate biasing for low-voltage analog/RF ICs without external feedback.
Dropout voltage	80 mV typ. @ 100 mA - enables regulation from 1.35 V input, critical for single-cell Li-ion or coin-cell systems.
Quiescent current	18 µA typ. @ no load; 38 µA typ. @ 150 mA - minimizes standby drain in always-on sensor nodes.
Output noise	29 µVRMS (1.1–100 kHz), no bypass cap - eliminates need for noise-filtering capacitors in PLL/VCO supply rails.
PSRR	65 dB @ 1 kHz - suppresses ripple from noisy switching supplies feeding sensitive analog stages.
Enable logic threshold	V_IL ≤ 0.4 V, V_IH ≥ 0.9 V - compatible with 1.2 V/1.8 V GPIO without level shifters.
Thermal shutdown	160 °C with 20 °C hysteresis - protects against sustained overload in compact PCB layouts.

Pinout & Package

SOT23-5L package: 5-pin surface-mount, 1.45 mm × 1.60 mm footprint, 0.95 mm pitch, thermally enhanced plastic body with exposed pad not present (standard SOT23-5L).

Pin/Terminal	Circuit Role	Design Meaning
1 IN	LDO input supply	Accepts 1.5–5.5 V DC; must be decoupled with ≥1 µF ceramic capacitor close to pin.
2 GND	Analog/digital ground reference	Single ground connection shared by input/output paths; requires low-inductance PCB return path.
3 EN	Active-high enable control	Drives device ON when ≥0.9 V; pulls output to high-impedance state when ≤0.4 V (I_EN < 100 nA).
4 NC	No connect	Internally unconnected; must remain floating - no PCB trace or solder mask opening required.
5 OUT	Regulated 1.25 V output	Supplies load up to 150 mA; stable with 1 µF ceramic capacitor; ESR-independent design.

Key Features

Feature	Design Value
Ultra-low-noise regulation	29 µVRMS output noise without bypass capacitor - directly powers RF transceivers and precision ADC references.
Sub-1 µA shutdown mode	0.001–1 µA total current consumption in OFF state - extends battery life in wake-on-event architectures.
Ceramic-capacitor stability	Stable with 1 µF C_OUT (ESR < 2.4 Ω) - eliminates tantalum or electrolytic capacitors, reducing size and cost.
Wide input voltage range	1.5–5.5 V operation - supports direct connection to single Li-ion, 3×AA, or post-buck converter rails.
Integrated protection	Current limiting (350 mA short-circuit) and thermal shutdown (160 °C) - prevents damage during fault conditions without external components.

Applications

Wireless Sensor Node Power

Low-Voltage Microcontroller Core Supply

Use Scenario: Powering BLE SoC (e.g., nRF52832) RF section and 32-bit ARM core from a single 3.0 V Li-ion cell.

IC Role / Device Role / Timing Role: Primary LDO providing clean 1.25 V rail for RF synthesizer VCO and digital core logic.

Use Value: 29 µVRMS noise avoids phase jitter degradation; 80 mV dropout allows >95% battery utilization down to 1.35 V.

Use Scenario: Supplying 1.25 V to FPGA I/O banks or ASIC auxiliary domains requiring tight voltage tolerance.

IC Role / Device Role / Timing Role: Secondary regulated rail derived from main 3.3 V system supply, enabling voltage domain isolation.

Use Value: ±2.0% output accuracy ensures reliable I/O signaling margins; enable control synchronizes power-up with system reset sequence.

Portable Medical Pulse Oximeter

Industrial IoT Edge Node Analog Front-End

Use Scenario: Biasing photodiode transimpedance amplifier and ADC driver in battery-powered pulse oximetry module.

IC Role / Device Role / Timing Role: Low-noise analog supply rail decoupled from digital switching noise sources.

Use Value: 65 dB PSRR at 1 kHz rejects switching ripple from nearby DC-DC converters; –40 °C to 125 °C rating supports clinical-grade thermal validation.

Use Scenario: Powering precision instrumentation amplifier (e.g., AD8421) and 24-bit sigma-delta ADC in condition-monitoring sensor node.

IC Role / Device Role / Timing Role: Reference-grade analog supply ensuring <1 LSB error contribution from power rail noise.

Use Value: 29 µVRMS noise translates to <0.001% of 1.25 V full-scale - negligible impact on 110 dB SNR ADC performance.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6219B122MR-G	1.2 V output (not 1.25 V); 120 mV dropout @ 100 mA; 45 µVRMS noise; requires 2.2 µF ceramic C_OUT.	Not drop-in for 1.25 V–critical circuits; higher noise limits use in RF/VCO applications.	Select only if 1.2 V tolerance acceptable and board space allows larger output capacitor.
Richtek RT9013-12PU5	1.2 V output; 200 mV dropout @ 150 mA; 40 µVRMS noise; 50 µA quiescent current @ no load.	Higher dropout and quiescent current reduce battery runtime and low-input headroom vs. LD39015M125R.	Prefer for cost-sensitive designs where 1.2 V suffices and 125 °C operation is not required.

Compared with XC6219B122MR-G and RT9013-12PU5, the LD39015M125R uniquely delivers exact 1.25 V output, lowest noise (29 µVRMS), lowest dropout (80 mV), and widest temperature range (–40 °C to 125 °C), making it optimal for precision analog and extended-temperature embedded systems.

Availability

LD39015M125R is available at Aetrix Electronics and suitable for wireless sensor nodes, portable medical monitors, industrial IoT edge nodes, and low-power microcontroller subsystems requiring stable component supply with guaranteed long-term manufacturability.

Supply support for LD39015M125R 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 chips for automotive, industrial, and consumer markets.

The LD39015 series belongs to ST's high-performance LDO portfolio, engineered specifically for ultra-low-noise, low-quiescent-current regulation in battery-constrained and signal-integrity-critical applications such as wearables, medical sensors, and RF modules.

FAQ

What is the minimum input voltage required for regulation at 1.25 V output?

The LD39015M125R requires VIN ≥ VOUT + VDROP to maintain regulation. With 80 mV typical dropout at 100 mA, the minimum functional input is 1.33 V. Absolute minimum operating input is 1.5 V per datasheet specifications, below which UVLO (1.45 V turn-on threshold) prevents activation.

Can the LD39015M125R be used with aluminum polymer or tantalum output capacitors?

Yes - though optimized for 1 µF ceramic capacitors, the LD39015M125R remains stable with aluminum polymer (ESR ~10–50 mΩ) and tantalum (ESR ~100–500 mΩ) capacitors per Figure 7 stability region. However, ceramic is preferred for lowest noise and smallest footprint.

Does the NC pin (Pin 4) require any PCB layout treatment?

No - Pin 4 is internally unconnected. It must be left floating: no trace, no solder mask opening, no thermal pad connection. Routing copper under or adjacent to this pin is acceptable, but avoid stitching to ground or other nets.

How does thermal shutdown behave during continuous overload?

When junction temperature reaches 160 °C, the LD39015M125R disables the pass transistor and holds output in high-impedance state until temperature drops by ≥20 °C (hysteresis). This cycle repeats autonomously - no external reset or intervention needed - protecting both IC and load.

LD39015M125R Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: SC-74A, SOT-753

Packaging:: Tape & Reel (TR)

Product Status:: Active

Output Configuration:: Positive

Output Type:: Fixed

Number of Regulators:: 1

Voltage - Input (Max):: 5.5V

Voltage - Output (Min/Fixed):: 1.25V

Voltage - Output (Max):: -

Voltage Dropout (Max):: 0.1V @ 100mA

Current - Output:: 150mA

Current - Quiescent (Iq):: 50 µA

Current - Supply (Max):: 70 µA

PSRR:: 65dB ~ 62dB (1kHz ~ 10kHz)

Control Features:: Enable

Protection Features:: Over Current, Over Temperature

Operating Temperature:: -40°C ~ 125°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-5

LD39015M125R FAQ

1.How can I place an order for LD39015M125R through Aetrix?

Please submit a Request for Quotation (RFQ) for LD39015M125R 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 LD39015M125R reliable?

The price and inventory of LD39015M125R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LD39015M125R is usually 5 days.

3.What payment methods are accepted for LD39015M125R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LD39015M125R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LD39015M125R?

LD39015M125R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LD39015M125R 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 LD39015M125R?

For technical support, including LD39015M125R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LD39015M125R requirements.

6.How does Aetrix verify that LD39015M125R is sourced from the original manufacturer or authorized distributors?

All LD39015M125R 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 LD39015M125R meets industry standards.

7.What is the process for return or replacement of LD39015M125R?

All LD39015M125R units undergo pre-shipment inspection (PSI). If there is an issue with LD39015M125R, 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 LD39015M125R part is unused and in its original packaging.

Return procedure for LD39015M125R:

1.Submit a request within 90 days.

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

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