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

STMicroelectronics LD3985G28R

Name: LD3985G28R
Brand: STMicroelectronics
SKU: LD3985G28R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LD3985G28R

Manufacturer:: STMicroelectronics

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

Package:: SOT-23-5 Thin, TSOT-23-5

Datasheet:: LD3985G28R.pdf

Description:: IC REG LIN 2.8V 150MA TSOT23-5

Quantity:: RFQ Add To RFQ list

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Inventory:1,432

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Product details

Overview

LD3985G28R from STMicroelectronics is a 2.8 V fixed-output, ultra-low-dropout linear regulator (LDO) designed for local voltage regulation in battery-powered systems. It delivers up to 150 mA with 60 mV typical dropout at full load, 30 µV_RMS output noise (10 Hz–100 kHz), and 60 dB supply voltage rejection at 1 kHz - enabling clean power for RF ICs and precision analog circuits in mobile handsets.

For engineers reviewing the LD3985G28R datasheet, LD3985G28R pinout, LD3985G28R application, or LD3985G28R equivalent, key selection criteria include its low quiescent current (85 µA typ. at no load), logic-controlled shutdown (VINH threshold: 1.2 V ON / 0.4 V OFF), SOT23-5L package compatibility, and stability with 1 µF ceramic output capacitors.

Technical Context

The LD3985G28R uses BiCMOS process technology to achieve ultra-low dropout and low-noise regulation across –40 °C to +125 °C junction temperature. Its internal architecture integrates a precision bandgap reference, error amplifier, and PMOS pass transistor - eliminating body diode conduction and enabling true reverse-current blocking.

It features a dedicated BYPASS pin for external 10 nF capacitor connection to suppress high-frequency noise, and VINH provides TTL/CMOS-compatible enable control with <1 nA input leakage. Thermal shutdown (160 °C) and internal current limiting ensure robust operation under fault conditions.

Key Specifications

Parameter	Value and Actual Design Meaning
Output voltage	Fixed 2.8 V ±2% over –40 °C to +125 °C; ensures stable core voltage for 2.8 V I/O rails
Dropout voltage	60 mV typ. at 150 mA; allows regulation down to 2.86 V input - critical for single-cell Li-ion (3.0 V min) longevity
Quiescent current	85 µA typ. at no load; extends battery runtime in always-on sensor nodes and standby modes
Output noise	30 µV_RMS (10 Hz–100 kHz); meets low-noise requirements for ADC references and RF front-end biasing
PSRR	60 dB at 1 kHz; suppresses switching noise from DC-DC converters feeding the LDO input
Shutdown current	1.5 µA max. in OFF mode; enables deep-sleep power gating for system-level energy optimization
Enable threshold	VINH = 1.2 V (ON), 0.4 V (OFF); compatible with 1.8 V and 3.3 V GPIO without level-shifting

Pinout & Package

SOT23-5L package: 5-pin surface-mount, 1.3 mm × 2.9 mm footprint, 0.95 mm pitch, thermal pad optional (not electrically connected).

Pin/Terminal	Circuit Role	Design Meaning
1 (VI)	Input voltage supply	Accepts 2.5–6 V DC; withstands 6.5 V non-repetitive spikes - suitable for noisy DC-DC outputs
2 (GND)	Power ground reference	Common return path for input/output currents; must be low-inductance connection to minimize noise coupling
3 (VINH)	Logic enable input	Active-high control: ≥1.2 V enables regulation; ≤0.4 V disables output and reduces IQ to <1.5 µA
4 (BYPASS)	Noise reduction node	Connects to 10 nF capacitor to shunt high-frequency error amplifier noise - improves PSRR above 100 kHz
5 (VO)	Regulated output	Delivers 2.8 V ±2% at up to 150 mA; requires ≥1 µF ceramic capacitor (ESR ≤5 Ω) for stability

Key Features

Feature	Design Value
Ultra-low dropout	60 mV at 150 mA enables use with depleted batteries or low-headroom DC-DC stages
Low-noise regulation	30 µV_RMS output noise supports sensitive RF transceivers and high-resolution ADCs without external filtering
Logic-controlled shutdown	VINH interface draws <1 nA, allowing direct connection to microcontroller GPIOs without pull-up loading
Ceramic capacitor stability	Stable with 1 µF X5R/X7R ceramics (ESR 5–5000 mΩ) - eliminates need for costly tantalum or electrolytic caps
Wide temperature range	Specified from –40 °C to +125 °C junction temperature - qualified for automotive infotainment and industrial edge sensors

Applications

Mobile Phone Power Management

Wearable Sensor Node

Use Scenario: Regulating 2.8 V supply for camera module I/O and touch controller in compact smartphone PCBs.

IC Role / Device Role / Timing Role: Local LDO providing clean, low-noise 2.8 V rail independent of main PMIC switching noise.

Use Value: 60 dB PSRR at 1 kHz prevents switching artifacts from degrading image sensor SNR and touch sensitivity.

Use Scenario: Powering ultra-low-power BLE SoC peripherals (accelerometer, ambient light sensor) in fitness trackers.

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

Use Value: Extends coin-cell battery life beyond 12 months by minimizing no-load current and enabling fast wake-up via VINH.

Industrial IoT Gateway

Automotive Cabin Camera

Use Scenario: Supplying 2.8 V to RS-485 transceiver logic interface in harsh factory environments.

IC Role / Device Role / Timing Role: Fault-tolerant local regulator with thermal shutdown and current limiting for field-deployed gateways.

Use Value: –40 °C to +125 °C operation and 160 °C thermal cutoff ensure reliability in uncontrolled ambient enclosures.

Use Scenario: Biasing 2.8 V image signal processor (ISP) in AEC-Q200-compliant rear-view camera modules.

IC Role / Device Role / Timing Role: Automotive-grade LDO meeting stringent EMI and transient immunity requirements.

Use Value: 30 µV_RMS noise and 60 mV dropout preserve ISP dynamic range and enable operation down to cold-crank battery voltages.

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, 150 mA, 120 mV dropout at 100 mA; 50 µV_RMS noise; SOT23-5 package	Higher dropout and noise reduce suitability for low-V_IN battery operation and RF-sensitive loads	Select when cost sensitivity outweighs ultra-low-noise or lowest-dropout requirements
ROHM BD3985GUL	2.8 V fixed, 150 mA, 70 mV dropout at 150 mA; 25 µV_RMS noise; same SOT23-5L footprint	Lower noise but tighter input voltage range (2.7–5.5 V); no VINH shutdown pin	Choose when minimal noise is critical and system lacks enable control signals

Compared with XC6206P282MR and BD3985GUL, the LD3985G28R uniquely balances ultra-low dropout (60 mV), industry-leading PSRR (60 dB @ 1 kHz), and integrated logic-enable - making it optimal for space-constrained, battery-operated systems requiring both efficiency and signal integrity.

Availability

LD3985G28R is available at Aetrix Electronics and suitable for mobile phone power management, wearable sensor nodes, industrial IoT gateways, and automotive cabin cameras requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LD3985G28R 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 LD3985 belongs to ST's ultra-low-noise LDO portfolio targeting portable and battery-powered applications where power integrity, size, and thermal performance are critical constraints.

FAQ

What is the minimum output capacitor required for stability?

The LD3985G28R is stable with a minimum 1 µF ceramic capacitor (X5R/X7R) on the VO pin, with ESR between 5 mΩ and 5 Ω. The datasheet confirms stability across ±30% capacitance tolerance and full temperature range, eliminating need for external compensation networks.

Does the BYPASS pin require a specific capacitor type or value?

Yes - a 10 nF ceramic capacitor (typically C0G/NP0) must be connected between BYPASS and GND. This capacitor filters high-frequency noise in the error amplifier's reference path, directly improving PSRR above 100 kHz and reducing output noise spectral density.

Can LD3985G28R operate with input voltage below 2.5 V?

No - the absolute minimum operating input voltage is 2.5 V per datasheet Section 4 (Maximum Ratings) and Section 5 (Electrical Characteristics). Operation below this risks functional failure or undefined regulation behavior, even if the dropout condition appears met.

Is thermal shutdown automatically reset after cooling?

Yes - thermal shutdown activates at 160 °C junction temperature and includes ~20 °C hysteresis. Once junction temperature falls below ~140 °C, regulation resumes automatically without requiring VINH cycling or power cycle, supporting self-recovering operation in thermally constrained enclosures.

LD3985G28R Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: SOT-23-5 Thin, TSOT-23-5

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):: 0.1V @ 150mA

Current - Output:: 150mA

Current - Quiescent (Iq):: 150 µA

Current - Supply (Max):: 250 µA

PSRR:: 60dB ~ 50dB (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:: TSOT-23-5

LD3985G28R FAQ

1.How can I place an order for LD3985G28R through Aetrix?

Please submit a Request for Quotation (RFQ) for LD3985G28R 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 LD3985G28R reliable?

The price and inventory of LD3985G28R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LD3985G28R is usually 5 days.

3.What payment methods are accepted for LD3985G28R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LD3985G28R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LD3985G28R?

LD3985G28R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LD3985G28R 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 LD3985G28R?

For technical support, including LD3985G28R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LD3985G28R requirements.

6.How does Aetrix verify that LD3985G28R is sourced from the original manufacturer or authorized distributors?

All LD3985G28R 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 LD3985G28R meets industry standards.

7.What is the process for return or replacement of LD3985G28R?

All LD3985G28R units undergo pre-shipment inspection (PSI). If there is an issue with LD3985G28R, 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 LD3985G28R part is unused and in its original packaging.

Return procedure for LD3985G28R:

1.Submit a request within 90 days.

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

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