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

STMicroelectronics LDS3985M28R

Name: LDS3985M28R
Brand: STMicroelectronics
SKU: LDS3985M28R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LDS3985M28R

Manufacturer:: STMicroelectronics

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

Package:: SC-74A, SOT-753

Datasheet:: LDS3985M28R.pdf

Description:: IC REG LINEAR 2.8V 300MA SOT23-5

Quantity:: RFQ Add To RFQ list

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Product details

Overview

LDS3985M28R from STMicroelectronics is a fixed-output 2.8 V, 300 mA low-dropout (LDO) linear voltage regulator in SOT23-5L package, featuring 150 mV typical dropout at full load, 30 µV_RMS output noise (10 Hz–100 kHz), and logic-controlled shutdown. It operates from 2.5 V to 6 V input and delivers ultra-low quiescent current (85 µA typ. at no load), making it ideal for battery-powered mobile phones and portable information appliances requiring stable, low-noise local regulation.

For engineers reviewing the LDS3985M28R datasheet, LDS3985M28R pinout, LDS3985M28R application, or LDS3985M28R equivalent, key selection criteria include dropout performance at 300 mA, shutdown leakage (<1.5 µA), SVR (55 dB @ 1 kHz), thermal shutdown threshold (160 °C), and compatibility with 2.2 µF ceramic output capacitors.

Technical Context

The LDS3985M28R employs a BiCMOS architecture to achieve ultra-low dropout and quiescent current simultaneously. Its internal reference and error amplifier drive a PMOS pass transistor, enabling fast transient response and high PSRR without external compensation.

It integrates logic-level inhibit control (VINH), bypass pin for noise filtering, and robust protection: thermal shutdown with 20 °C hysteresis and internal current limiting. The device is specified across –40 °C to +125 °C junction temperature, with automotive-grade variants available in DFN6.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 2.8 V ±2% over –40 °C to +125 °C; ensures stable rail for 2.8 V logic or analog circuitry.
Max Output Current	300 mA guaranteed; supports moderate-power microcontrollers, sensors, or RF front-ends.
Dropout Voltage	150 mV typ. at 300 mA; enables operation down to 2.95 V input, extending battery runtime.
Quiescent Current	85 µA typ. at no load; critical for always-on subsystems in battery-constrained devices.
Output Noise	30 µV_RMS (10 Hz–100 kHz); suitable for noise-sensitive analog/RF supply domains.
Supply Rejection	55 dB @ 1 kHz; suppresses ripple from noisy switching supplies feeding the LDO input.
Shutdown Leakage	1.5 µA max. in OFF mode; minimizes standby power loss during system sleep states.

Pinout & Package

Supplied in SOT23-5L package (2.95 mm × 1.60 mm × 1.45 mm), surface-mount, RoHS-compliant, ECOPACK®2 rated.

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 up to 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	Active-high enable: ≥1.2 V = ON, ≤0.4 V = OFF; requires external pull-up/down-no internal bias.
4 - Bypass	Noise reduction terminal	Connects to 10 nF capacitor to shunt high-frequency noise on internal reference path.
5 - VO	Regulated output	Delivers stable 2.8 V ±2%; requires 2.2 µF ceramic output capacitor (5–5000 mΩ ESR).

Key Features

Feature	Design Value
Ultra-low dropout	150 mV typ. at 300 mA enables operation from single-cell Li-ion (2.95 V min) through full discharge.
Low-noise regulation	30 µV_RMS output noise and 55 dB SVR ensure clean power for ADCs, PLLs, and RF ICs.
Logic-controlled shutdown	VINH pin draws only ±1 nA, allowing direct interface with GPIOs without loading drivers.
Thermal & current protection	160 °C thermal shutdown with 20 °C hysteresis and internal current limit prevent damage under fault.
Capacitor flexibility	Stable with low-ESR ceramic capacitors (2.2–22 µF); eliminates need for costly tantalum or polymer types.

Applications

Mobile Handsets

Wearable Sensors

Use Scenario: Powering baseband processor I/O rails and camera sensor analog supplies in compact smartphones.

IC Role / Device Role / Timing Role: Local LDO regulator providing isolated, low-noise 2.8 V domain independent of main PMIC.

Use Value: 150 mV dropout extends usable battery range by ~120 mV; 30 µV_RMS noise prevents image sensor banding.

Use Scenario: Supplying MEMS accelerometers and BLE SoCs in fitness trackers with multi-day battery life.

IC Role / Device Role / Timing Role: Always-on LDO delivering 2.8 V with 85 µA quiescent current during deep-sleep modes.

Use Value: Sub-1 µA shutdown leakage preserves battery capacity over weeks of standby; fast 240 µs turn-on enables responsive wake-up.

Portable Medical Devices

Industrial IoT Edge Nodes

Use Scenario: Regulating power to low-power ECG front-end amplifiers and SAR ADCs in handheld diagnostics.

IC Role / Device Role / Timing Role: Precision analog LDO ensuring stable 2.8 V reference for signal chain integrity.

Use Value: 55 dB SVR at 1 kHz rejects switching noise from nearby DC-DC converters; ±2% output tolerance meets medical accuracy requirements.

Use Scenario: Providing regulated 2.8 V to LoRa transceivers and environmental sensors in remote wireless nodes.

IC Role / Device Role / Timing Role: Ruggedized local regulator operating across –40 °C to +125 °C ambient.

Use Value: Full-spec operation to +125 °C junction enables deployment in hot enclosures; thermal shutdown prevents field failures.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6206P282MR	2.8 V fixed, 300 mA, 250 mV dropout @ 300 mA, 1.5 µA IQ, no bypass pin	Lacks bypass pin and SVR spec; lower PSRR (40 dB @ 1 kHz)	Lower cost where noise immunity is secondary and board space allows larger dropout margin.
ROHM BD3985FVM-TR	2.8 V fixed, 300 mA, 200 mV dropout @ 300 mA, 100 µA IQ, integrated soft-start	Higher dropout, no VINH logic control; includes soft-start but no bypass pin	Preferred when inrush current limiting is required, but unsuitable for GPIO-controlled shutdown.

Compared with XC6206P282MR and BD3985FVM-TR, the LDS3985M28R uniquely combines ultra-low dropout (150 mV), low-noise design (30 µV_RMS), and logic-enable functionality in a 5-pin SOT23 package-enabling tighter battery utilization, cleaner analog performance, and precise system-level power sequencing.

Availability

LDS3985M28R is available at Aetrix Electronics and suitable for mobile handsets, wearable sensors, portable medical devices, and industrial IoT edge nodes requiring stable component supply, long-lifecycle support, and automotive-qualified alternatives.

Supply support for LDS3985M28R 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 products for automotive, industrial, and consumer markets.

The LDS3985 belongs to ST's high-performance analog LDO portfolio, engineered specifically for ultra-low-power, low-noise, and thermally robust local regulation in space-constrained portable electronics.

FAQ

What is the minimum input voltage required for stable 2.8 V output at 300 mA?

The LDS3985M28R requires a minimum input voltage of 2.95 V (2.8 V + 150 mV typical dropout) to maintain regulation at 300 mA load. Input below 2.5 V is not supported per absolute maximum ratings, and dropout increases significantly below 2.95 V under full load.

Can the Bypass (BP) pin be left unconnected?

No-the Bypass pin must be connected to a 10 nF capacitor to ground. Leaving it floating degrades output noise performance and may cause instability in the internal reference circuit; the datasheet explicitly warns against floating this pin.

Is the LDS3985M28R qualified for automotive applications?

The LDS3985M28R is the standard industrial-grade variant (–40 °C to +125 °C). Automotive qualification is available under part number LDS3985PU28R in DFN6 package, which meets AEC-Q100 Grade 3 and includes advanced screening per AEC-Q001/Q002.

What output capacitor ESR range ensures stability?

The LDS3985M28R is stable with ceramic output capacitors having ESR between 5 mΩ and 5000 mΩ. Unlike older LDOs, it does not require minimum ESR, enabling use of low-ESR X7R/X5R ceramics without series resistance.

LDS3985M28R 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):: 2.8V

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

LDS3985M28R FAQ

1.How can I place an order for LDS3985M28R through Aetrix?

Please submit a Request for Quotation (RFQ) for LDS3985M28R 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 LDS3985M28R reliable?

The price and inventory of LDS3985M28R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LDS3985M28R is usually 5 days.

3.What payment methods are accepted for LDS3985M28R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LDS3985M28R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LDS3985M28R?

LDS3985M28R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LDS3985M28R 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 LDS3985M28R?

For technical support, including LDS3985M28R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LDS3985M28R requirements.

6.How does Aetrix verify that LDS3985M28R is sourced from the original manufacturer or authorized distributors?

All LDS3985M28R 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 LDS3985M28R meets industry standards.

7.What is the process for return or replacement of LDS3985M28R?

All LDS3985M28R units undergo pre-shipment inspection (PSI). If there is an issue with LDS3985M28R, 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 LDS3985M28R part is unused and in its original packaging.

Return procedure for LDS3985M28R:

1.Submit a request within 90 days.

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

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