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

STMicroelectronics LD3985M47R

Name: LD3985M47R
Brand: STMicroelectronics
SKU: LD3985M47R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LD3985M47R

Manufacturer:: STMicroelectronics

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

Package:: SC-74A, SOT-753

Datasheet:: LD3985M47R.pdf

Description:: IC REG LINEAR 4.7V 150MA SOT23-5

Quantity:: RFQ Add To RFQ list

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Inventory:1,546

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Product details

Overview

LD3985M47R from STMicroelectronics is a 4.7 V fixed-output, ultra-low-dropout linear voltage regulator 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 is optimized for noise-sensitive battery-powered applications such as RF power amplifiers and precision analog sensor supplies.

For engineers reviewing the LD3985M47R datasheet, LD3985M47R pinout, LD3985M47R application, or LD3985M47R equivalent, key selection criteria include guaranteed 150 mA output current, sub-100 µA quiescent current in active mode, thermal shutdown at 160 °C, stable operation with 1 µF ceramic output capacitor, and compatibility with low-ESR capacitors down to 5 mΩ.

Technical Context

The LD3985M47R employs BiCMOS process technology to achieve ultra-low dropout and low-noise regulation without requiring external compensation. Its internal architecture integrates a precision bandgap reference, error amplifier, pass transistor, and independent inhibit control logic that enables fast turn-on (200 µs typ.) and deep OFF-mode current (≤1.5 µA).

It maintains high PSRR (>50 dB up to 10 kHz) across wide input voltage range (2.5–6 V) and load conditions (1–150 mA), with line/load regulation specified at ±0.1 %/V and ≤0.005 %/mA respectively for 4.7 V output - critical for maintaining signal integrity in mixed-signal SoC power domains.

Key Specifications

Parameter	Value and Actual Design Meaning
Output voltage	Fixed 4.7 V ±2% over -40 °C to 125 °C; ensures stable bias for 5 V-tolerant analog circuitry.
Dropout voltage	60 mV typ. at 150 mA; enables regulation down to 4.76 V input - extends usable battery life in single-cell Li-ion systems.
Output noise	30 µV_RMS (10 Hz–100 kHz); minimizes jitter and SNR degradation in ADC reference and RF LNA supply rails.
PSRR	60 dB at 1 kHz, 50 dB at 10 kHz; suppresses switching noise from adjacent DC-DC converters in compact PCB layouts.
Quiescent current	85 µA typ. at no load; reduces standby power loss in always-on subsystems like real-time clocks or wake-up sensors.
Shutdown current	1.5 µA max. at -40 °C to 125 °C; supports ultra-low-power system-level sleep modes compliant with IoT energy budgets.
Thermal shutdown	160 °C with 20 °C hysteresis; provides self-protection during sustained overload or poor PCB thermal design.

Pinout & Package

LD3985M47R is housed in a RoHS-compliant SOT23-5L package (2.95 mm × 1.60 mm × 1.30 mm), optimized for space-constrained portable designs and compatible with standard reflow soldering profiles.

Pin/Terminal	Circuit Role	Design Meaning
1 - VI	Input voltage supply	Accepts 2.5–6 V DC; withstands non-repetitive 6.5 V spikes up to 200 ms - tolerates transient battery surges.
2 - GND	Power ground reference	Common return path for input, output, and bypass networks; must be low-impedance to preserve PSRR and noise performance.
3 - VINH	Logic-enable control input	Active-high enable: ≥1.2 V turns regulator ON; ≤0.4 V forces shutdown; requires external pull-down if unused.
4 - BYPASS	Noise reduction terminal	Connects to 10 nF ceramic capacitor to shunt high-frequency reference noise - essential for achieving 30 µV_RMS spec.
5 - VO	Regulated output	Delivers stable 4.7 V ±2%; supports 1–22 µF ceramic output capacitors with ESR 5–5000 mΩ for stability.

Key Features

Feature	Design Value
Ultra-low dropout	60 mV at 150 mA enables operation with minimal headroom - ideal for single-cell Li-ion (3.0–4.2 V) powering 4.7 V analog rails.
Low-noise regulation	30 µV_RMS output noise over 10 Hz–100 kHz meets stringent requirements of RF front-ends and high-resolution SAR ADCs.
Fast enable response	200 µs typical turn-on time allows dynamic power gating in microcontroller-based sensor nodes with tight timing budgets.
Stable with ceramic caps	Guaranteed stability with 1 µF X7R/X5R ceramic output capacitor eliminates need for costly tantalum or electrolytic alternatives.
Wide temperature range	-40 °C to +125 °C junction operation supports automotive cabin modules and industrial edge controllers without derating.

Applications

Wireless Transceiver Power

Portable Medical Sensor

Use Scenario: Powering RF power amplifier stages in Bluetooth Low Energy (BLE) modules where supply ripple directly impacts EVM and ACLR.

IC Role / Device Role / Timing Role: Local LDO providing clean 4.7 V bias to PA driver stage, decoupled from noisy system DC-DC converter.

Use Value: 60 dB PSRR at 1 kHz suppresses switching artifacts from 1 MHz buck converter, preserving RF spectral purity.

Use Scenario: Supplying ultra-low-noise analog front-end (AFE) of wearable ECG monitor operating from coin-cell battery.

IC Role / Device Role / Timing Role: Precision voltage source for instrumentation amplifier and 16-bit delta-sigma ADC reference.

Use Value: 30 µV_RMS noise contributes <0.001% error to 1.2 V reference - enabling <1 µV resolution in biopotential measurement.

Automotive Body Control Module

Industrial PLC I/O Channel

Use Scenario: Regulating 4.7 V supply for LIN transceiver and microcontroller I/O in door module exposed to -40 °C cold cranking.

IC Role / Device Role / Timing Role: High-reliability local regulator with thermal shutdown and wide-input tolerance for harsh automotive environments.

Use Value: Operates continuously at 125 °C junction temperature and survives 6.5 V load-dump transients - eliminates need for external TVS.

Use Scenario: Providing isolated 4.7 V rail for analog input conditioning circuitry in modular PLC base unit with 24 V backplane.

IC Role / Device Role / Timing Role: Low-quiescent-current LDO enabling always-on diagnostics while minimizing heat buildup in sealed enclosures.

Use Value: 85 µA no-load IQ reduces standby power by >90% vs. legacy regulators - extends mean time between failures in fanless designs.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6206P472MR	4.7 V fixed output, 100 mA rating, 120 mV dropout at 100 mA, 45 µV_RMS noise, no shutdown pin	Lacks logic-controlled enable; requires external MOSFET for power gating - increases BOM count and board area	Select when cost sensitivity outweighs need for dynamic power control and higher output current capability
Diodes Inc. AP7361-C-47SA	4.7 V fixed output, 300 mA rating, 250 mV dropout at 300 mA, 40 µV_RMS noise, 1.5 µA shutdown current	Higher dropout limits use below 5.0 V input; larger SOT89-3 package increases thermal resistance (R_thJA = 120 °C/W)	Prefer when higher output current is required and PCB layout allows larger footprint and thermal relief

Compared with XC6206P472MR and AP7361-C-47SA, LD3985M47R uniquely balances ultra-low dropout (60 mV), industry-leading noise (30 µV_RMS), integrated enable, and SOT23-5L compactness - making it optimal for space- and noise-constrained battery-powered systems demanding 150 mA.

Availability

LD3985M47R is available at Aetrix Electronics and suitable for wireless transceivers, portable medical sensors, automotive body control modules, and industrial PLC I/O channels requiring stable component supply under extended temperature and low-noise constraints.

Supply support for LD3985M47R 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 microcontrollers, power management ICs, sensors, and analog devices for industrial, automotive, and consumer markets.

The LD3985 series belongs to ST's ultra-low-noise, low-I_Q LDO portfolio, engineered specifically for battery-powered and noise-critical applications where regulation accuracy, thermal robustness, and minimal standby consumption are mandatory.

FAQ

What is the minimum output capacitor value required for stability?

The LD3985M47R is stable with a minimum 1 µF ceramic output capacitor (X7R or X5R dielectric), and remains stable across ±30% capacitance tolerance and full temperature range (-40 °C to 125 °C). ESR must be between 5 mΩ and 5000 mΩ; typical designs use 2.2 µF or 4.7 µF for improved transient response.

Can the BYPASS pin be left unconnected?

No - the BYPASS pin must be connected to a 10 nF ceramic capacitor to ground to achieve the specified 30 µV_RMS output noise. Leaving it floating degrades noise performance significantly and may cause instability due to uncontrolled reference node impedance.

What happens if VINH is left floating?

VINH has no internal pull-up or pull-down; floating causes undefined enable state and potential oscillation or partial conduction. ST specifies mandatory external connection - either tie to VI via 100 kΩ resistor for default ON, or to GND for default OFF, depending on system power sequencing requirements.

Is the LD3985M47R qualified for automotive applications?

While not AEC-Q100 qualified, the LD3985M47R operates across -40 °C to +125 °C junction temperature, includes thermal shutdown at 160 °C, and withstands 6.5 V input transients - enabling use in non-safety-critical automotive cabin modules (e.g., infotainment USB ports, ambient light sensors) with proper system-level qualification.

LD3985M47R Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tape & Reel (TR)

Product Status:: Active

Output Configuration:: Positive

Output Type:: Fixed

Number of Regulators:: 1

Voltage - Input (Max):: 6V

Voltage - Output (Min/Fixed):: 4.7V

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:: SOT-23-5

LD3985M47R FAQ

1.How can I place an order for LD3985M47R through Aetrix?

Please submit a Request for Quotation (RFQ) for LD3985M47R 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 LD3985M47R reliable?

The price and inventory of LD3985M47R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LD3985M47R is usually 5 days.

3.What payment methods are accepted for LD3985M47R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LD3985M47R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LD3985M47R?

LD3985M47R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LD3985M47R 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 LD3985M47R?

For technical support, including LD3985M47R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LD3985M47R requirements.

6.How does Aetrix verify that LD3985M47R is sourced from the original manufacturer or authorized distributors?

All LD3985M47R 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 LD3985M47R meets industry standards.

7.What is the process for return or replacement of LD3985M47R?

All LD3985M47R units undergo pre-shipment inspection (PSI). If there is an issue with LD3985M47R, 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 LD3985M47R part is unused and in its original packaging.

Return procedure for LD3985M47R:

1.Submit a request within 90 days.

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

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