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

STMicroelectronics LDS3985M15R

Name: LDS3985M15R
Brand: STMicroelectronics
SKU: LDS3985M15R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LDS3985M15R

Manufacturer:: STMicroelectronics

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

Package:: SC-74A, SOT-753

Datasheet:: LDS3985M15R.pdf

Description:: IC REG LINEAR 1.5V 300MA SOT23-5

Quantity:: RFQ Add To RFQ list

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Product details

Overview

LDS3985M15R from STMicroelectronics is a fixed-output 1.5 V, 300 mA low-dropout (LDO) linear voltage regulator in SOT23-5L package. It delivers ultra-low dropout (150 mV typ. at 300 mA), low quiescent current (85 µA typ. at no load), and low output noise (30 µV_RMS), designed for battery-powered wireless systems requiring stable local regulation with logic-controlled shutdown.

For engineers reviewing the LDS3985M15R datasheet, LDS3985M15R pinout, LDS3985M15R application, or LDS3985M15R equivalent, key selection criteria include dropout performance at 300 mA load, shutdown leakage (<1.5 µA), thermal shutdown threshold (160 °C), and compatibility with 2.2 µF ceramic output capacitors.

Technical Context

The LDS3985M15R employs BiCMOS process technology to achieve simultaneous low dropout and low quiescent current. Its internal architecture integrates a precision bandgap reference, error amplifier, power transistor, and thermal/current protection circuitry - all optimized for operation across -40 °C to 125 °C junction temperature.

It features a dedicated bypass pin (CBYP) for noise filtering and a logic-controlled inhibit input (VINH) with defined thresholds (≤0.4 V for OFF, ≥1.2 V for ON), enabling precise system-level power sequencing without external pull resistors.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 1.5 V ±50 mV (at 1 mA, 25 °C); ±75 mV over full -40 °C to 125 °C range
Max Output Current	300 mA guaranteed; peak capability up to 550 mA before current limiting engages
Dropout Voltage	150 mV typical at 300 mA load; enables regulation from 1.65 V input minimum
Quiescent Current	85 µA typical at no load; rises to 200 µA at 300 mA; drops to ≤1.5 µA in OFF mode
Output Noise	30 µV_RMS (10 Hz–100 kHz bandwidth), critical for powering RF and analog sensor circuits
Supply Rejection	55 dB at 1 kHz; maintains clean output under noisy input conditions (e.g., switching supply rails)
Turn-on Time	240 µs typical (with 33 nF bypass cap), supporting fast wake-up in low-power microcontroller systems

Pinout & Package

SOT23-5L package: 5-pin surface-mount, 2.95 mm × 1.60 mm footprint, 1.45 mm height, ECOPACK® compliant.

Pin/Terminal	Circuit Role	Design Meaning
1 (VI)	LDO input voltage	Accepts 2.5–6 V DC input; withstands non-repetitive 6.5 V spikes (200 ms)
2 (GND)	Common ground	Reference node for all internal circuitry; must be low-impedance connection to PCB ground plane
3 (VINH)	Inhibit control input	Logic high (≥1.2 V) enables output; logic low (≤0.4 V) disables output; not internally biased
4 (BYPASS)	Noise reduction terminal	Connects external 10–33 nF capacitor to suppress high-frequency output noise and improve PSRR
5 (VO)	Regulated output	Delivers stable 1.5 V to load; requires 2.2–22 µF ceramic output capacitor (ESR 5–5000 mΩ)

Key Features

Feature	Design Value
Ultra-low dropout	150 mV at full 300 mA load enables use in single-cell Li-ion (3.0–4.2 V) or dual-cell alkaline systems
Low-noise regulation	30 µV_RMS noise floor supports sensitive analog/RF loads without additional filtering stages
Logic-controlled shutdown	Sub-µA OFF-state current (≤1.5 µA) reduces system standby power in portable devices
Stable with ceramic caps	Compatible with low-ESR 2.2 µF ceramic output capacitors - eliminates need for bulkier tantalum alternatives
Integrated protection	Thermal shutdown (160 °C) and current limiting prevent damage during overload or ambient overheating

Applications

Mobile Handsets

Wearable Health Sensors

Use Scenario: Powering baseband processor core voltage and RF transceiver bias in compact smartphones.

IC Role / Device Role / Timing Role: Local LDO regulator providing clean, low-noise 1.5 V supply independent of main PMIC rail.

Use Value: Enables reliable operation under dynamic load transients while minimizing battery drain via 85 µA quiescent current.

Use Scenario: Supplying ultra-low-power ECG/PPG analog front-end ICs in wrist-worn monitors.

IC Role / Device Role / Timing Role: Precision voltage source delivering stable 1.5 V to high-gain instrumentation amplifiers.

Use Value: 30 µV_RMS noise ensures minimal interference in sub-microvolt biomedical signal acquisition.

Industrial IoT Edge Nodes

Automotive Body Control Modules

Use Scenario: Regulating power for LoRaWAN/Wi-Fi MCU subsystems operating on coin-cell or energy-harvested sources.

IC Role / Device Role / Timing Role: Low-quiescent LDO enabling multi-year battery life with periodic wake-up cycles.

Use Value: 1.5 µA OFF-mode current extends shelf life and operational runtime in intermittent-sensing applications.

Use Scenario: Providing 1.5 V bias to LIN transceiver interface ICs in door module ECUs.

IC Role / Device Role / Timing Role: Automotive-grade LDO (AEC-Q100 qualified variant available) with extended temperature support.

Use Value: Guaranteed operation from -40 °C to 85 °C and 55 dB SVR suppresses alternator ripple in vehicle electrical systems.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6206P152MR	1.5 V fixed, 300 mA, SOT23-5; higher dropout (250 mV @ 300 mA), higher IQ (1.2 µA OFF)	Lacks bypass pin; lower PSRR (45 dB @ 1 kHz); suitable only where noise immunity is secondary	Select when cost sensitivity outweighs noise/dropout requirements and automotive qualification is unnecessary
ON Semiconductor NCP1117ST15T3G	1.5 V fixed, 800 mA, SOT223; much higher dropout (1.1 V @ 800 mA), higher IQ (6 mA typical)	Requires larger output capacitor (10 µF min); unsuitable for battery life-critical or space-constrained designs	Choose only if higher current headroom is needed and board area/thermal budget permits SOT223 footprint

Compared with XC6206P152MR and NCP1117ST15T3G, LDS3985M15R uniquely balances ultra-low dropout, sub-µA shutdown, and integrated bypass filtering - making it optimal for compact, battery-sensitive applications demanding clean 1.5 V rails.

Availability

LDS3985M15R is available at Aetrix Electronics and suitable for mobile handsets, wearable health sensors, industrial IoT edge nodes, and automotive body control modules requiring stable component supply across production lifecycles.

Supply support for LDS3985M15R 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 analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The LDS3985 series belongs to ST's high-performance LDO portfolio, engineered specifically for ultra-low-power, noise-sensitive applications in portable and automotive electronics where efficiency, stability, and reliability are critical.

FAQ

What is the minimum input voltage required for stable 1.5 V output at 300 mA?

The LDS3985M15R requires a minimum input voltage of 1.65 V (1.5 V + 150 mV typical dropout) to maintain regulation at full 300 mA load. Input below 2.5 V is not recommended per absolute maximum ratings, and operation below 2.5 V is unsupported per datasheet specifications.

Can the bypass (BYPASS) pin be left unconnected?

No - the BYPASS pin must be connected to a 10–33 nF capacitor to ground. Leaving it floating degrades noise performance and PSRR; omitting the capacitor increases output noise beyond the specified 30 µV_RMS and reduces high-frequency supply rejection.

Is an external pull-up or pull-down resistor required on the VINH pin?

Yes - VINH has no internal bias. A pull-down resistor (e.g., 100 kΩ to GND) is required if active-high enable is used, or a pull-up (e.g., 100 kΩ to VI) if active-low logic is implemented. Floating VINH causes undefined output state and potential malfunction.

Does LDS3985M15R support ceramic output capacitors with ESR below 5 mΩ?

No - the datasheet specifies a minimum ESR of 5 mΩ for stable operation. Using ultra-low-ESR ceramics (<5 mΩ) without series resistance risks oscillation. A 5–5000 mΩ ESR range is mandatory; adding a small series resistor (e.g., 10–50 mΩ) restores stability if ultra-low-ESR caps are used.

LDS3985M15R Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Output Configuration:: Positive

Output Type:: Fixed

Number of Regulators:: 1

Voltage - Input (Max):: 6V

Voltage - Output (Min/Fixed):: 1.5V

Voltage - Output (Max):: -

Voltage Dropout (Max):: 0.25V @ 300mA

Current - Output:: 300mA

Current - Quiescent (Iq):: 150 µA

Current - Supply (Max):: 300 µA

PSRR:: 55dB ~ 50dB (1kHz ~ 10kHz)

Control Features:: Shutdown

Protection Features:: Over Current, Over Temperature

Operating Temperature:: -40°C ~ 125°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-5

LDS3985M15R FAQ

1.How can I place an order for LDS3985M15R through Aetrix?

Please submit a Request for Quotation (RFQ) for LDS3985M15R 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 LDS3985M15R reliable?

The price and inventory of LDS3985M15R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LDS3985M15R is usually 5 days.

3.What payment methods are accepted for LDS3985M15R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LDS3985M15R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LDS3985M15R?

LDS3985M15R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LDS3985M15R 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 LDS3985M15R?

For technical support, including LDS3985M15R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LDS3985M15R requirements.

6.How does Aetrix verify that LDS3985M15R is sourced from the original manufacturer or authorized distributors?

All LDS3985M15R 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 LDS3985M15R meets industry standards.

7.What is the process for return or replacement of LDS3985M15R?

All LDS3985M15R units undergo pre-shipment inspection (PSI). If there is an issue with LDS3985M15R, 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 LDS3985M15R part is unused and in its original packaging.

Return procedure for LDS3985M15R:

1.Submit a request within 90 days.

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

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