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

STMicroelectronics LD3985G30R

Name: LD3985G30R
Brand: STMicroelectronics
SKU: LD3985G30R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LD3985G30R

Manufacturer:: STMicroelectronics

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

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

Datasheet:: LD3985G30R.pdf

Description:: IC REG LINEAR 3V 150MA TSOT23-5

Quantity:: RFQ Add To RFQ list

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Inventory:1,031

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Product details

Overview

LD3985G30R from STMicroelectronics is a 3.0 V fixed-output, ultra-low-dropout linear regulator (LDO) in SOT23-5L package, delivering 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. It features logic-controlled shutdown, operates from 2.5 V to 6 V input, and targets power-sensitive battery-operated systems such as mobile phone baseband ICs and RF front-end modules.

For engineers reviewing the LD3985G30R datasheet, LD3985G30R pinout, LD3985G30R application, or LD3985G30R equivalent, key selection criteria include its low-noise regulation for analog/RF rails, sub-100 µA quiescent current in active mode, thermal shutdown at 160 °C, and guaranteed stability with 1 µF ceramic output capacitors - all validated across –40 °C to 125 °C junction temperature.

Technical Context

The LD3985G30R uses a BiCMOS architecture to achieve ultra-low dropout (0.4 mV typ. at 1 mA) while maintaining high PSRR (60 dB @ 1 kHz) and low noise (30 µV_RMS). Its internal current and thermal limiting protect against overload and fault conditions without external components.

Logic-controlled inhibit (VINH) enables precise system-level power sequencing: device enters <1.5 µA OFF mode when VINH ≤ 0.4 V, and resumes regulation within 250 µs when VINH ≥ 1.2 V. The dedicated BYPASS pin accepts a 10 nF capacitor to suppress high-frequency noise on the reference path.

Key Specifications

Parameter	Value and Actual Design Meaning
Output voltage	Fixed 3.0 V ±2% over –40 °C to 125 °C; ensures stable core voltage for 3.0 V logic and analog subsystems
Dropout voltage	60 mV typ. at 150 mA; allows operation down to 3.06 V input, extending battery runtime in single-cell Li-ion systems
Quiescent current	85 µA typ. at no load; minimizes standby power loss in always-on sensor nodes and wearable devices
Output noise	30 µV_RMS (10 Hz–100 kHz); meets low-noise requirements for ADC references and RF synthesizer supplies
PSRR	60 dB at 1 kHz; suppresses ripple from switching DC-DC stages feeding the LDO input
Shutdown current	1.5 µA max. at –40 °C to 125 °C; enables deep-sleep modes in portable IoT endpoints
Thermal shutdown	160 °C with 20 °C hysteresis; provides self-protection during sustained overload or poor PCB thermal design

Pinout & Package

LD3985G30R is housed in a RoHS-compliant SOT23-5L package (1.45 mm × 1.30 mm × 0.95 mm height), optimized for space-constrained portable designs and compatible with standard reflow profiles.

Pin/Terminal	Circuit Role	Design Meaning
1 (VI)	Input voltage supply	Accepts 2.5 V–6 V DC; withstands non-repetitive 6.5 V spikes for 200 ms
2 (GND)	Power ground reference	Common return path for input, output, and internal circuitry; must be low-impedance
3 (VINH)	Inhibit control input	Active-high logic enable: ≥1.2 V = ON, ≤0.4 V = OFF; requires external pull-up/down; not internally biased
4 (BYPASS)	Noise reduction node	Connects to 10 nF capacitor to stabilize internal reference and reduce high-frequency output noise
5 (VO)	Regulated output	Delivers 3.0 V ±2% at up to 150 mA; stable with 1 µF–22 µF ceramic capacitors (ESR 5–5000 mΩ)

Key Features

Feature	Design Value
Ultra-low dropout	60 mV at 150 mA enables >98% efficiency in 3.3 V → 3.0 V conversion, critical for Li-ion discharge curves
Low-noise regulation	30 µV_RMS noise supports precision analog circuits (e.g., audio codecs, RF VCOs) without additional filtering
Fast turn-on time	200 µs typ. (95% of 3.0 V) allows rapid wake-up from sleep states in real-time microcontrollers
Stable with ceramic caps	Guaranteed stability with 1 µF X7R/X5R ceramics eliminates need for costly tantalum or electrolytic capacitors
Logic-controlled shutdown	VINH interface simplifies integration into PMIC-controlled power trees without external MOSFETs or level shifters

Applications

Mobile Baseband Power

Wireless Sensor Node Core Rail

Use Scenario: Powering ARM Cortex-M4 core and embedded SRAM in Bluetooth LE modules.

IC Role / Device Role / Timing Role: Primary 3.0 V LDO supplying digital logic and memory, sequenced via MCU GPIO.

Use Value: 85 µA quiescent current extends battery life to >2 years in coin-cell-powered sensors; 60 dB PSRR rejects noise from BLE radio switching.

Use Scenario: Regulating supply for ultra-low-power environmental sensor ICs (e.g., BME280, OPT3001).

IC Role / Device Role / Timing Role: Local LDO providing clean 3.0 V to analog signal chain and I²C interface.

Use Value: 30 µV_RMS noise prevents measurement drift; 1.5 µA shutdown current enables multi-year operation on CR2032 cells.

RF Front-End Bias Supply

Wearable Heart Rate Monitor Analog Rail

Use Scenario: Delivering low-noise 3.0 V to RF power amplifier bias networks in 2.4 GHz ISM-band transceivers.

IC Role / Device Role / Timing Role: Noise-suppressed auxiliary LDO decoupling PA supply from noisy main DC-DC converter.

Use Value: BYPASS pin + 10 nF cap reduces phase noise contribution; 60 mV dropout maintains PA linearity down to 3.06 V battery voltage.

Use Scenario: Powering photodiode amplifier and ADC in optical PPG heart rate sensors.

IC Role / Device Role / Timing Role: Precision analog LDO isolating sensitive analog front-end from digital switching noise.

Use Value: 30 µV_RMS noise ensures <1 LSB error in 12-bit medical-grade ADC conversions; –40 °C to 125 °C rating covers skin-contact thermal extremes.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6206P302MR	3.0 V fixed, 150 mA, 120 mV dropout @ 150 mA, 50 µV_RMS noise, no BYPASS pin	Lacks dedicated noise-reduction pin; higher dropout reduces usable battery range	Choose if board layout lacks space for 10 nF BYPASS cap and PSRR >50 dB is sufficient
Diodes Inc. AP2210K-3.0TRG1	3.0 V fixed, 150 mA, 250 mV dropout @ 150 mA, 120 µA IQ, no thermal shutdown	No internal thermal protection; higher quiescent current increases standby drain	Choose only for cost-sensitive, non-thermal-critical applications with ample heatsinking

Compared with XC6206P302MR and AP2210K-3.0TRG1, LD3985G30R delivers superior noise performance (30 vs. ≥50 µV_RMS), lower dropout (60 vs. ≥120 mV), and integrated thermal shutdown - making it optimal for compact, battery-limited, and noise-sensitive analog/RF systems where reliability and efficiency are prioritized over minimal BOM count.

Availability

LD3985G30R is available at Aetrix Electronics and suitable for mobile communications, wireless sensor networks, and wearable health monitoring systems requiring stable component supply, long-term lifecycle support, and automotive-grade temperature resilience.

Supply support for LD3985G30R 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 LD3985 belongs to ST's ultra-low-noise, low-quiescent-current LDO family, engineered specifically for powering noise-sensitive analog and RF circuitry in battery-constrained portable electronics.

FAQ

What is the minimum output capacitor required for stable operation?

The LD3985G30R is stable with a minimum 1 µF ceramic output capacitor (X5R/X7R), and remains stable across ±30% capacitance tolerance and full temperature range. Using 2.2 µF or higher improves transient response and further lowers output impedance at high frequencies.

Can the BYPASS pin be left unconnected?

No - the BYPASS pin must be connected to a 10 nF ceramic capacitor to ground. Leaving it floating degrades output noise performance and may cause instability; the capacitor directly filters the internal reference voltage and is essential for achieving the specified 30 µV_RMS noise.

Does LD3985G30R require an input capacitor?

Yes - a minimum 1 µF ceramic input capacitor (CI) is recommended close to the VI and GND pins to limit input voltage spikes and improve transient response. While not strictly required for stability, omitting it risks violating absolute maximum ratings during fast load transients or hot-plug events.

Is the shutdown function compatible with 1.8 V logic levels?

Yes - the VINH threshold is defined as logic high ≥1.2 V and logic low ≤0.4 V, making it fully compatible with 1.8 V, 2.5 V, and 3.3 V GPIO outputs. No level-shifting circuitry is needed, simplifying interface with modern low-voltage MCUs and PMICs.

LD3985G30R 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):: 3V

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

LD3985G30R FAQ

1.How can I place an order for LD3985G30R through Aetrix?

Please submit a Request for Quotation (RFQ) for LD3985G30R 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 LD3985G30R reliable?

The price and inventory of LD3985G30R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LD3985G30R is usually 5 days.

3.What payment methods are accepted for LD3985G30R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LD3985G30R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LD3985G30R?

LD3985G30R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LD3985G30R 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 LD3985G30R?

For technical support, including LD3985G30R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LD3985G30R requirements.

6.How does Aetrix verify that LD3985G30R is sourced from the original manufacturer or authorized distributors?

All LD3985G30R 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 LD3985G30R meets industry standards.

7.What is the process for return or replacement of LD3985G30R?

All LD3985G30R units undergo pre-shipment inspection (PSI). If there is an issue with LD3985G30R, 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 LD3985G30R part is unused and in its original packaging.

Return procedure for LD3985G30R:

1.Submit a request within 90 days.

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

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