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

STMicroelectronics LDS3985PM33R

Name: LDS3985PM33R
Brand: STMicroelectronics
SKU: LDS3985PM33R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LDS3985PM33R

Manufacturer:: STMicroelectronics

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

Package:: 6-VDFN Exposed Pad

Datasheet:: LDS3985PM33R.pdf

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

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Product details

Overview

LDS3985PM33R from STMicroelectronics is a fixed 3.3 V, 300 mA low-dropout (LDO) linear voltage regulator in DFN6 (3 × 3 mm) package, featuring 150 mV typical dropout at full load, 30 µV_RMS output noise (10 Hz–100 kHz), and logic-controlled shutdown. It operates from 2.5 V to 6 V input, supports ceramic output capacitors down to 2.2 µF, and targets power-sensitive battery-operated systems requiring stable, ultra-low-noise rail generation.

For engineers reviewing the LDS3985PM33R datasheet, LDS3985PM33R pinout, LDS3985PM33R application, or LDS3985PM33R equivalent, key selection criteria include dropout behavior under 300 mA load, quiescent current in ON/OFF modes (85 µA typ. / 1.5 µA max), thermal shutdown threshold (160 °C), SVR performance (55 dB @ 1 kHz), and compatibility with low-ESR ceramic capacitors.

Technical Context

The LDS3985PM33R uses a BiCMOS architecture to achieve ultra-low dropout (0.4 mV typ. at 1 mA; 150 mV typ. at 300 mA) and sub-100 µA quiescent current across temperature. Its internal reference and error amplifier are optimized for stability with 2.2–22 µF ceramic output capacitors and 33 nF bypass capacitor on the BYP pin.

It integrates logic-controlled inhibit (VINH), with defined thresholds (≤0.4 V for OFF, ≥1.2 V for ON), internal current limiting, and thermal shutdown at 160 °C with ~20 °C hysteresis. The device delivers 3.3 V ±2% over –40 °C to +125 °C junction temperature with <0.004 %/mA load regulation for VO ≥ 2.5 V.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 3.3 V ±2% over –40 °C to +125 °C; enables direct replacement of standard 3.3 V rails without external feedback.
Max Output Current	300 mA guaranteed; supports microcontroller cores, RF transceivers, and sensor interfaces in compact portable designs.
Dropout Voltage	150 mV typical at 300 mA; allows operation from 3.45 V input while maintaining regulation - critical for single-cell Li-ion or Li-poly systems.
Quiescent Current	85 µA typical at no load; rises to 200 µA at 300 mA; ensures >1-year battery life in always-on IoT endpoints.
Output Noise	30 µV_RMS (10 Hz–100 kHz); minimizes jitter in ADC references and analog signal chains without additional filtering.
SVR	55 dB @ 1 kHz; suppresses switching noise from upstream DC-DC converters feeding the LDO input.
Shutdown Current	1.5 µA maximum in OFF mode; enables deep-sleep power gating for system-level energy optimization.

Pinout & Package

DFN6 (3 × 3 mm) package with exposed thermal pad (EP) for enhanced thermal 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 supply; 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 100 kHz.
5 (VINH)	Inhibit control input	Active-high enable: ≥1.2 V = ON, ≤0.4 V = OFF; must not be left floating; draws ±1 nA.
6 (NC)	No connect	Internally unconnected; electrically isolated; 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 and tight input-output margins.
Low-noise regulation	30 µV_RMS noise and 55 dB SVR support precision analog circuits without post-LDO filtering.
Logic-controlled shutdown	VINH interface with nanoscale input current allows direct MCU GPIO control without level-shifting or pull resistors.
Thermal & current protection	Integrated 160 °C thermal shutdown with 20 °C hysteresis and current limiting prevent damage during overload or ambient extremes.
Ceramic capacitor compatible	Stable with 2.2–22 µF ceramic output caps (5–5000 mΩ ESR); eliminates need for costly tantalum or electrolytic alternatives.

Applications

Wearable Health Monitor

Industrial Sensor Node

Use Scenario: Continuous ECG/PPG sensing powered by coin-cell or thin-film battery.

IC Role / Device Role / Timing Role: Primary 3.3 V supply for analog front-end, ADC, and BLE SoC during active and sleep cycles.

Use Value: 85 µA quiescent current extends battery life beyond 12 months; 30 µV_RMS noise prevents baseline drift in biopotential measurements.

Use Scenario: Wireless vibration/temperature node deployed in factory machinery with 10+ year field life.

IC Role / Device Role / Timing Role: Local regulation for MEMS accelerometer and LoRaWAN transceiver under wide temperature (-40 °C to +85 °C).

Use Value: Guaranteed 300 mA output and -40 °C to +125 °C operation ensure reliability in uncontrolled environments; 150 mV dropout maintains regulation as input decays.

Automotive Infotainment Display

Portable Medical Ultrasound Probe

Use Scenario: Powering LCD bias and touch controller in automotive-grade head unit display module.

IC Role / Device Role / Timing Role: Secondary LDO delivering clean 3.3 V from 5 V domain; enabled only during display activity.

Use Value: VINH-controlled shutdown reduces system standby power; AEC-Q100 qualified variant (LDS3985PU33RY) available for automotive qualification.

Use Scenario: Battery-powered handheld ultrasound probe requiring low-noise analog supply for beamforming ICs.

IC Role / Device Role / Timing Role: Low-noise 3.3 V rail for time-critical analog signal chain preceding digitization.

Use Value: 55 dB SVR at 1 kHz rejects noise from nearby switching regulators; 30 µV_RMS noise preserves SNR in high-resolution echo imaging.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6206P332MR	300 mA max, 250 mV dropout at 300 mA, 12 µA IQ, no shutdown pin	Lacks logic-controlled inhibit; unsuitable for dynamic power-gating architectures	Select when minimal quiescent current dominates over shutdown flexibility and noise performance
Diodes AP7361-33SG-7	300 mA max, 200 mV dropout at 300 mA, 60 µA IQ, 45 dB SVR @ 1 kHz	Lower SVR and higher dropout limit system headroom; no BYP pin for noise reduction	Prefer where cost sensitivity outweighs need for ultra-low noise and optimal dropout in battery-constrained designs

Compared with XC6206P332MR and AP7361-33SG-7, LDS3985PM33R uniquely combines sub-200 mV dropout, 30 µV_RMS noise, integrated BYP pin, and nanoscale shutdown control - making it optimal for high-fidelity, battery-limited, and thermally constrained applications where rail integrity directly impacts signal fidelity.

Availability

LDS3985PM33R is available at Aetrix Electronics and suitable for wearable health monitors, industrial sensor nodes, automotive infotainment displays, and portable medical ultrasound probes requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LDS3985PM33R 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 with emphasis on power efficiency, reliability, and functional safety.

LDS3985 belongs to ST's high-performance LDO regulator product line, engineered specifically for ultra-low-noise, low-quiescent-current, and wide-input-voltage applications in battery-powered and thermally demanding environments.

FAQ

What is the minimum output capacitor value required for stability?

The LDS3985PM33R is stable with ceramic output capacitors ranging from 2.2 µF to 22 µF and ESR between 5 mΩ and 5000 mΩ. A 2.2 µF X7R ceramic capacitor with ≤100 mΩ ESR is sufficient for most applications; larger values improve transient response but are not required for loop stability.

Can the BYP pin be left unconnected?

No - the BYP pin must be connected to a 33 nF capacitor (typically C0G/NP0) to ground. Leaving it open degrades high-frequency PSRR and increases output noise above 100 kHz; omitting this capacitor violates the recommended operating conditions specified in the datasheet.

Is thermal derating required for continuous 300 mA operation?

Yes - at ambient temperatures above 65 °C, output current must be reduced per the thermal resistance data: R_thJA = 55 °C/W. For example, at T_A = 85 °C and T_J(max) = 125 °C, maximum sustainable current is ~73 mA without forced airflow or heatsinking.

Does LDS3985PM33R support automotive qualification?

The LDS3985PM33R itself is not automotive-qualified; however, the functionally identical LDS3985PU33RY variant is AEC-Q100 qualified and characterized across –40 °C to +85 °C, with advanced screening per AEC-Q001/Q002. Use PU33RY for automotive applications requiring formal qualification.

LDS3985PM33R 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 ~ 125°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

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

LDS3985PM33R FAQ

1.How can I place an order for LDS3985PM33R through Aetrix?

Please submit a Request for Quotation (RFQ) for LDS3985PM33R 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 LDS3985PM33R reliable?

The price and inventory of LDS3985PM33R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LDS3985PM33R is usually 5 days.

3.What payment methods are accepted for LDS3985PM33R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LDS3985PM33R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LDS3985PM33R?

LDS3985PM33R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LDS3985PM33R 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 LDS3985PM33R?

For technical support, including LDS3985PM33R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LDS3985PM33R requirements.

6.How does Aetrix verify that LDS3985PM33R is sourced from the original manufacturer or authorized distributors?

All LDS3985PM33R 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 LDS3985PM33R meets industry standards.

7.What is the process for return or replacement of LDS3985PM33R?

All LDS3985PM33R units undergo pre-shipment inspection (PSI). If there is an issue with LDS3985PM33R, 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 LDS3985PM33R part is unused and in its original packaging.

Return procedure for LDS3985PM33R:

1.Submit a request within 90 days.

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

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