Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

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

STMicroelectronics LD3985G27R

Name: LD3985G27R
Brand: STMicroelectronics
SKU: LD3985G27R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: LD3985G27R

Manufacturer:: STMicroelectronics

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

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

Datasheet:: LD3985G27R.pdf

Description:: IC REG LIN 2.7V 150MA TSOT23-5

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:1,242

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

LD3985G27R from STMicroelectronics is a 2.7 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 µVRMS output noise (10 Hz–100 kHz), and logic-controlled shutdown. It operates from 2.5 V to 6 V input and targets low-power, battery-sensitive applications including mobile phone baseband ICs and wireless sensor nodes.

For engineers reviewing the LD3985G27R datasheet, LD3985G27R pinout, LD3985G27R application, or LD3985G27R equivalent, key selection criteria include dropout voltage at light/heavy load, shutdown quiescent current (<1.5 µA), output noise performance, supply voltage rejection (60 dB @ 1 kHz), and compatibility with 1 µF ceramic output capacitors.

Technical Context

The LD3985G27R uses a BiCMOS architecture to achieve ultra-low quiescent current (85 µA typ. at no load) while maintaining fast transient response and high PSRR. Its internal reference and error amplifier are optimized for stability with low-ESR ceramic capacitors down to 1 µF.

Shutdown is controlled via a dedicated VINH pin requiring ≥1.2 V for ON and ≤0.4 V for OFF; the pin must not be left floating. The BYPASS pin accepts a 10 nF capacitor to reduce high-frequency output noise by filtering internal reference noise.

Key Specifications

Parameter	Value and Actual Design Meaning
Output voltage	Fixed 2.7 V ±2% over -40 °C to 125 °C junction temperature
Dropout voltage	60 mV typical at 150 mA load; enables regulation down to VI = 2.76 V
Quiescent current	85 µA typical at no load; rises to 170 µA at 150 mA - minimal battery drain in active mode
Output noise	30 µVRMS (10 Hz–100 kHz); critical for powering RF transceivers and precision ADCs
PSRR	60 dB at 1 kHz; maintains clean output despite noisy battery or shared rail ripple
Shutdown current	1.5 µA maximum in OFF mode; preserves battery charge during system standby
Operating input range	2.5 V to 6 V DC; supports single-cell Li-ion (2.7–4.2 V) and dual-cell alkaline inputs

Pinout & Package

SOT23-5L surface-mount package (2.95 mm × 1.60 mm × 1.30 mm height), RoHS-compliant and ECOPACK® certified.

Pin/Terminal	Circuit Role	Design Meaning
1 (VI)	Input voltage supply	Accepts 2.5–6 V; withstands non-repetitive 6.5 V spikes (200 ms)
2 (GND)	Power ground reference	Common return path for input, output, and internal circuitry; requires low-inductance layout
3 (VINH)	Logic enable/disable control	High-true shutdown: ≥1.2 V = ON, ≤0.4 V = OFF; must be actively driven - no internal pull-up/down
4 (BYPASS)	Noise reduction filter node	Connects external 10 nF capacitor to GND to suppress reference noise and improve PSRR above 10 kHz
5 (VO)	Regulated output	Delivers stable 2.7 V ±2%; requires ≥1 µF ceramic capacitor (X5R/X7R) on output for stability

Key Features

Feature	Design Value
Ultra-low-noise regulation	30 µVRMS output noise enables direct powering of RF front-ends and precision analog circuits without additional filtering
Sub-100 mV dropout at 150 mA	Extends usable battery life in Li-ion systems by maintaining regulation until cell voltage drops to ~2.76 V
1.5 µA max shutdown current	Reduces system standby power to nanoampere scale - essential for IoT endpoint sleep modes
Stable with 1 µF ceramic output cap	Eliminates need for bulky tantalum or aluminum electrolytic capacitors; reduces board area and cost
60 dB PSRR at 1 kHz	Rejects switching regulator ripple and digital supply noise before it reaches sensitive analog loads

Applications

Mobile Baseband Power

Wireless Sensor Node Core Supply

Use Scenario: Powers baseband processor and audio codec in GSM/UMTS smartphones operating from single-cell Li-ion battery (2.7–4.2 V).

IC Role / Device Role / Timing Role: Primary LDO supplying clean 2.7 V to low-voltage logic and analog blocks; enabled/disabled via AP GPIO.

Use Value: Ultra-low quiescent current extends talk time; 30 µVRMS noise prevents audible artifacts in headset output.

Use Scenario: Supplies microcontroller, BLE radio, and environmental sensors in battery-powered industrial sensor nodes.

IC Role / Device Role / Timing Role: Always-on LDO for real-time clock and wake-up circuitry; shutdown controlled by MCU during deep-sleep cycles.

Use Value: 1.5 µA shutdown current enables >10-year battery life in 10-second wakeup intervals.

Portable Medical Monitor Analog Rails

Low-Power Industrial Controller I/O Isolation

Use Scenario: Provides regulated 2.7 V to ECG front-end amplifier and 16-bit SAR ADC in handheld patient monitors.

IC Role / Device Role / Timing Role: Precision analog LDO with low noise and high PSRR; decouples ADC reference from noisy digital supply.

Use Value: 30 µVRMS noise ensures <1 LSB noise floor for 16-bit conversion accuracy at 100 kSPS.

Use Scenario: Powers isolated RS-485 transceiver and optocoupler bias rails in programmable logic controller (PLC) I/O modules.

IC Role / Device Role / Timing Role: Local point-of-load regulator for isolated communication interface; shutdown synchronizes with bus activity.

Use Value: 60 mV dropout allows operation across full 2.5–6 V input range, accommodating wide industrial supply tolerances.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6206P272MR	2.7 V fixed, 150 mA, 120 mV dropout @ 150 mA; 1 µA shutdown current; requires 4.7 µF min. output cap	Higher dropout limits usable input range; lower shutdown current benefits ultra-low-power sleep	Prefer when minimizing shutdown leakage is critical and board space allows larger output capacitor
Micrel MIC5205-2.7YM5	2.7 V fixed, 150 mA, 170 mV dropout @ 150 mA; 80 µVRMS noise; no BYPASS pin	Higher noise degrades RF/analog performance; no bypass option limits high-frequency PSRR optimization	Choose only if BYPASS functionality is unnecessary and higher noise is acceptable in target signal chain

Compared with XC6206P272MR and MIC5205-2.7YM5, the LD3985G27R delivers superior noise performance (30 vs. 80 µVRMS) and lower dropout (60 vs. 120/170 mV), enabling longer battery runtime and cleaner analog supply - especially where the BYPASS pin is used to enhance high-frequency rejection.

Availability

LD3985G27R is available at Aetrix Electronics and suitable for mobile communications, portable medical devices, industrial sensor networks, and battery-powered IoT endpoints requiring stable component supply with guaranteed long-term availability.

Supply support for LD3985G27R 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, power management, and embedded applications.

The LD3985 belongs to ST's ultra-low-noise, low-quiescent-current LDO family, engineered specifically for power-sensitive portable electronics where battery life, signal integrity, and small footprint are critical design constraints.

FAQ

What is the minimum output capacitor required for stable operation of LD3985G27R?

The LD3985G27R is stable with a minimum 1 µF X5R or X7R ceramic capacitor on the VO pin. The datasheet confirms stability across temperature and tolerance variations even with ±30% capacitor value deviation. Larger values (e.g., 2.2 µF) improve transient response but are not required for basic stability.

Can the BYPASS pin be left unconnected?

No - the BYPASS pin must be connected to a 10 nF ceramic capacitor to GND. Leaving it floating degrades output noise performance and reduces PSRR above 10 kHz. The capacitor provides a low-impedance path for internal reference noise, and omission increases RMS noise beyond the specified 30 µVRMS.

Does LD3985G27R require an input capacitor?

An input capacitor is recommended but not strictly required for stability. A 1 µF ceramic capacitor placed close to the VI pin improves line transient response and reduces high-frequency noise coupling from the source. ST specifies CI = 1 µF in all electrical test conditions and typical application schematics.

What is the thermal shutdown threshold and hysteresis behavior?

The LD3985G27R activates thermal shutdown at 160 °C junction temperature, with typical hysteresis of 20 °C. This means the device resumes normal operation only after junction temperature falls below ~140 °C. The protection is internal and automatic, requiring no external circuitry, and is designed to prevent permanent damage during sustained overload or poor PCB thermal design.

LD3985G27R 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):: 2.7V

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

LD3985G27R FAQ

1.How can I place an order for LD3985G27R through Aetrix?

Please submit a Request for Quotation (RFQ) for LD3985G27R 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 LD3985G27R reliable?

The price and inventory of LD3985G27R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LD3985G27R is usually 5 days.

3.What payment methods are accepted for LD3985G27R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LD3985G27R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LD3985G27R?

LD3985G27R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LD3985G27R 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 LD3985G27R?

For technical support, including LD3985G27R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LD3985G27R requirements.

6.How does Aetrix verify that LD3985G27R is sourced from the original manufacturer or authorized distributors?

All LD3985G27R 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 LD3985G27R meets industry standards.

7.What is the process for return or replacement of LD3985G27R?

All LD3985G27R units undergo pre-shipment inspection (PSI). If there is an issue with LD3985G27R, 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 LD3985G27R part is unused and in its original packaging.

Return procedure for LD3985G27R:

1.Submit a request within 90 days.

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

Tech Hub

2026-09-11 Comparator Circuit: Voltage Thresholds, Op-Amp Differences, LM393 and Practical Design

Comparator circuit design covering voltage thresholds, input limits, open-collector outputs, LM393 wiring, op-amp differences, hysteresis, timing, window detection and practical fault diagnosis.

2026-09-10 Schmitt Trigger Explained: Hysteresis, Circuits, Inverters and Applications

Schmitt triggers use separate rising and falling thresholds to stabilize slow or noisy signals. This guide covers hysteresis, 74HC14 and 74HCT14 selection, comparator calculations, RC oscillators and p…

2026-09-09 Counterfeit Electronic Components: How to Detect, Authenticate, and Test Suspect Parts

Counterfeit components can hide behind convincing markings and passing basic function tests. This engineering reference covers source traceability, external inspection, X-ray, XRF, electrical testing, …

2026-09-08 Obsolete Electronic Components: How to Source and Evaluate Replacements

A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.

2026-09-07 TTL vs CMOS Logic Levels: 74HC and 74HCT Compatibility Explained

TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.

2026-09-04 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…

2026-09-02 74HC595 Pinout, Timing, Output Current, and Applications

The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …