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

STMicroelectronics LDS3985PU33RY

Name: LDS3985PU33RY
Brand: STMicroelectronics
SKU: LDS3985PU33RY
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LDS3985PU33RY

Manufacturer:: STMicroelectronics

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

Package:: 6-VDFN Exposed Pad

Datasheet:: LDS3985PU33RY.pdf

Description:: IC REG LINEAR 3.3V 300MA 6DFN

Quantity:: RFQ Add To RFQ list

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Product details

Overview

LDS3985PU33RY from STMicroelectronics is a fixed 3.3 V, 300 mA low-dropout (LDO) linear voltage regulator in DFN6 (3 × 3 mm) package, designed for battery-powered and noise-sensitive applications. It delivers ultra-low dropout (150 mV typ. at 300 mA), low quiescent current (85 µA typ. at no load), and low output noise (30 µV_RMS, 10 Hz–100 kHz), with logic-controlled shutdown and thermal/overcurrent protection.

For engineers reviewing the LDS3985PU33RY datasheet, LDS3985PU33RY pinout, LDS3985PU33RY application, or LDS3985PU33RY equivalent, key selection criteria include dropout behavior under 300 mA load, shutdown threshold compatibility with 1.4 V logic high, ceramic capacitor stability (2.2 µF output + 33 nF bypass), and automotive-grade thermal range suitability.

Technical Context

The LDS3985PU33RY uses a BiCMOS architecture to achieve sub-200 mV dropout at full 300 mA load while maintaining 85 µA quiescent current. Its internal reference and error amplifier enable ±2% output voltage accuracy over –40 °C to 125 °C, with line regulation of ±0.1 %/V and load regulation as low as 0.0008 %/mA for VO ≥ 2.5 V.

It integrates a dedicated bypass pin (CBYP) for external 33 nF capacitor to suppress high-frequency noise, achieving 55 dB SVR at 1 kHz and 30 µV_RMS integrated noise. The inhibit input (VINH) accepts TTL-compatible logic levels (≥1.4 V ON, ≤0.4 V OFF) with <1 nA leakage, enabling precise system-level power gating.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 3.3 V ±2% over –40 °C to 125 °C; ensures stable MCU core or RF IC supply without external feedback.
Dropout Voltage	150 mV typical at 300 mA; enables operation down to 3.45 V input, critical for single-cell Li-ion or Li-poly systems.
Quiescent Current	85 µA typical at no load; minimizes standby power loss in always-on sensor nodes or IoT edge devices.
Output Noise	30 µV_RMS (10 Hz–100 kHz); supports low-noise analog signal chains (e.g., ADC reference, RF LNA bias).
SVR	55 dB at 1 kHz; rejects ripple from switching DC/DC stages upstream, reducing need for additional filtering.
Shutdown Current	1.5 µA maximum in OFF mode; enables deep-sleep states with sub-µA system leakage budgets.
Thermal Shutdown	160 °C trigger with 20 °C hysteresis; protects against sustained overload in compact PCB layouts.

Pinout & Package

DFN6 (3 × 3 mm) package with exposed thermal pad (EP) for enhanced heat dissipation; RoHS-compliant, ECOPACK®2 qualified; R_thJA = 55 °C/W, R_thJC = 10 °C/W.

Pin/Terminal	Circuit Role	Design Meaning
1 (VI)	LDO input voltage	Accepts 2.5–6 V DC; 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 (VO)	LDO output voltage	Regulated 3.3 V output; requires ≥2.2 µF ceramic capacitor (5–5000 mΩ ESR) for stability.
4 (BYP)	Bypass capacitor terminal	Connects to 33 nF capacitor to reduce high-frequency noise and improve PSRR above 10 kHz.
5 (VINH)	Inhibit control input	TTL-compatible enable: ≥1.4 V = ON, ≤0.4 V = OFF; must not float; <1 nA input current.
6 (NC)	No connect	Internally unconnected; left floating per design-no PCB trace or solder required.

Key Features

Feature	Design Value
Ultra-low dropout	150 mV at 300 mA enables use with weak or aging batteries in portable medical devices.
Low-noise regulation	30 µV_RMS noise and 55 dB SVR support clean power for RF transceivers and precision ADCs.
Logic-controlled shutdown	VINH interface with 1.4 V logic-high threshold allows direct connection to GPIOs of ARM Cortex-M MCUs.
Ceramic capacitor stability	Stable with 2.2 µF CO (5–5000 mΩ ESR) and 33 nF CBYP-eliminates need for costly tantalum or polymer caps.
Automotive-grade option	LDS3985PU33RY qualified per AEC-Q100 Grade 3 (–40 °C to 85 °C) with advanced screening per AEC-Q001/Q002.

Applications

Wearable Health Monitor

Industrial Sensor Node

Use Scenario: Continuous ECG/PPG sensing powered by coin-cell or small Li-poly battery.

IC Role / Device Role / Timing Role: Primary 3.3 V supply for ultra-low-power MCU, analog front-end, and BLE radio.

Use Value: 85 µA quiescent current extends battery life beyond 1 year; 150 mV dropout sustains operation until battery reaches 3.45 V.

Use Scenario: Wireless temperature/humidity node deployed in factory automation cabinets.

IC Role / Device Role / Timing Role: Local regulator for microcontroller and digital sensor interface, activated only during measurement cycles.

Use Value: VINH shutdown reduces average system current to <1 µA in sleep; thermal shutdown prevents failure in enclosed enclosures.

Automotive Infotainment Display

Portable Test Equipment

Use Scenario: Powering LCD controller and touch interface in rear-seat entertainment unit.

IC Role / Device Role / Timing Role: Secondary LDO supplying noise-sensitive display timing ICs and level shifters.

Use Value: 30 µV_RMS noise prevents visible flicker or ghosting; AEC-Q100 qualification ensures reliability across vehicle lifetime.

Use Scenario: Handheld oscilloscope or multimeter with dual-domain (analog + digital) signal path.

IC Role / Device Role / Timing Role: Clean 3.3 V rail for high-resolution ADC reference and FPGA configuration memory.

Use Value: 55 dB SVR isolates analog section from digital switching noise; fast 240 µs turn-on enables responsive power sequencing.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6219B332MR-G	300 mA, 3.3 V fixed, SOT-25; dropout 200 mV @ 300 mA; IQ = 1 µA (typ.) in shutdown but 25 µA (typ.) active.	Lacks bypass pin and SVR >50 dB spec; lower noise not characterized; not AEC-Q100 qualified.	Prefer for cost-sensitive consumer wearables where automotive qualification and ultra-low noise are not required.
ON Semiconductor NCP114AMX33TBG	300 mA, 3.3 V fixed, SOT-23-5; dropout 170 mV @ 300 mA; IQ = 45 µA (typ.) active; 1 µA (typ.) shutdown.	No dedicated BYP pin; 45 µV_RMS noise (higher); SVR = 45 dB @ 1 kHz; industrial temp only (–40 °C to 105 °C).	Prefer when footprint compatibility with legacy SOT-23-5 designs is mandatory and DFN6 thermal performance is not critical.

Compared with XC6219B332MR-G and NCP114AMX33TBG, the LDS3985PU33RY offers superior noise performance (30 µV_RMS vs ≥45 µV), higher SVR (55 dB), and automotive qualification-making it optimal for safety-critical or high-fidelity analog systems where DFN6 thermal handling is acceptable.

Availability

LDS3985PU33RY is available at Aetrix Electronics and suitable for wearable health monitors, industrial wireless sensors, automotive infotainment displays, and portable test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LDS3985PU33RY 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, delivering intelligent power, analog, MEMS, and microcontroller solutions for industrial, automotive, and consumer markets.

The LDS3985 belongs to ST's high-performance LDO regulator product line, engineered specifically for ultra-low-noise, low-quiescent-current power management in battery-constrained and EMI-sensitive applications.

FAQ

What is the minimum input voltage required for stable 3.3 V output at 300 mA?

The LDS3985PU33RY requires VI ≥ VO + VDROP = 3.3 V + 0.15 V = 3.45 V (typical) to maintain regulation at 300 mA. Absolute minimum VI is 2.5 V, but output drops below 3.3 V if input falls below 3.45 V under full load. Input must remain ≥2.5 V to avoid shutdown or undefined behavior.

Can the BYP pin be left unconnected?

No. The BYP pin must be connected to a 33 nF ceramic capacitor (±20%) referenced to GND. Leaving it open degrades high-frequency PSRR and increases output noise beyond the specified 30 µV_RMS; ST's characterization and stability guarantee assume this capacitor is present.

Is the LDS3985PU33RY pin-compatible with other DFN6 LDOs?

No. Pin assignment (VI–GND–VO–BYP–VINH–NC) is unique to the LDS3985 family. Substituting with other DFN6 LDOs-such as TPS7A05 or AP2204-requires PCB redesign due to differing pin functions (e.g., missing BYP, swapped EN/GND, or different NC locations).

Does the device require an input capacitor?

Yes. A minimum 1 µF ceramic capacitor (X5R/X7R) must be placed between VI and GND, within 5 mm of the input pins. This stabilizes the input rail during transient load steps and prevents oscillation caused by source impedance; ST specifies CI = 1 µF in all electrical characteristics test conditions.

LDS3985PU33RY Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 6-VDFN Exposed Pad

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):: 3.3V

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 ~ 85°C

Grade:: Automotive

Qualification:: AEC-Q100

Mounting Type:: Surface Mount

Supplier Device Package:: 6-DFN (3x3)

LDS3985PU33RY FAQ

1.How can I place an order for LDS3985PU33RY through Aetrix?

Please submit a Request for Quotation (RFQ) for LDS3985PU33RY 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 LDS3985PU33RY reliable?

The price and inventory of LDS3985PU33RY are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LDS3985PU33RY is usually 5 days.

3.What payment methods are accepted for LDS3985PU33RY?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LDS3985PU33RY transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LDS3985PU33RY?

LDS3985PU33RY orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LDS3985PU33RY 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 LDS3985PU33RY?

For technical support, including LDS3985PU33RY datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LDS3985PU33RY requirements.

6.How does Aetrix verify that LDS3985PU33RY is sourced from the original manufacturer or authorized distributors?

All LDS3985PU33RY 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 LDS3985PU33RY meets industry standards.

7.What is the process for return or replacement of LDS3985PU33RY?

All LDS3985PU33RY units undergo pre-shipment inspection (PSI). If there is an issue with LDS3985PU33RY, 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 LDS3985PU33RY part is unused and in its original packaging.

Return procedure for LDS3985PU33RY:

1.Submit a request within 90 days.

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

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