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

STMicroelectronics LDS3985PU28R

Name: LDS3985PU28R
Brand: STMicroelectronics
SKU: LDS3985PU28R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LDS3985PU28R

Manufacturer:: STMicroelectronics

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

Package:: 6-VDFN Exposed Pad

Datasheet:: LDS3985PU28R.pdf

Description:: IC REG LINEAR 2.8V 300MA 6DFN

Quantity:: RFQ Add To RFQ list

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Inventory:2,726

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Product details

Overview

LDS3985PU28R from STMicroelectronics is a fixed 2.8 V, 300 mA low-dropout linear regulator in DFN6 (3 × 3 mm) package. 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), enabling use as a local power rail in battery-powered wireless systems.

For engineers reviewing the LDS3985PU28R datasheet, LDS3985PU28R pinout, LDS3985PU28R application, or LDS3985PU28R equivalent, key selection criteria include dropout voltage under 300 mA load, shutdown logic compatibility with 1.2 V threshold, thermal performance in automotive-grade ambient (−40 °C to 85 °C), and ceramic capacitor stability with CO ≥ 2.2 µF.

Technical Context

The LDS3985PU28R employs BiCMOS process technology to achieve simultaneous low dropout and low quiescent current. Its internal architecture integrates a precision bandgap reference, error amplifier, PMOS pass transistor, and logic-controlled inhibit circuitry with hysteresis-free enable threshold (VINH high = 1.4 V, low = 0.4 V).

It features internal thermal shutdown (160 °C trip, 20 °C hysteresis) and current limiting (600 mA short-circuit peak). Supply voltage rejection is 55 dB at 1 kHz and 50 dB at 10 kHz, with output stability guaranteed using low-ESR ceramic capacitors (2.2–22 µF, ESR 5–5000 mΩ).

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 2.8 V ±2% over −40 °C to 85 °C; ensures stable core voltage for 2.8 V I/O rails.
Max Output Current	300 mA continuous; supports moderate-power microcontrollers and RF front-ends.
Dropout Voltage	150 mV typical at 300 mA; enables operation down to 2.95 V input, critical for single-cell Li-ion systems.
Quiescent Current	85 µA typical at no load; minimizes standby power loss in always-on sensor nodes.
Output Noise	30 µV_RMS (10 Hz–100 kHz); preserves signal integrity in analog/RF subsystems.
SVR	55 dB at 1 kHz; suppresses switching noise from upstream DC-DC converters.
Shutdown Current	1.5 µA max at −40 °C to 85 °C; enables deep-sleep mode in portable devices.

Pinout & Package

DFN6 (3 × 3 mm) package with exposed thermal pad (pin 2 is NC, not connected). Thermal resistance R_thJA = 55 °C/W enables reliable operation at full load without external heatsinking in standard PCB layouts.

Pin/Terminal	Circuit Role	Design Meaning
1 (VI)	LDO input voltage	Accepts 2.5–6 V supply; withstands non-repetitive 6.5 V spikes (200 ms).
2 (NC)	No connection	Internally unconnected; must be left floating or tied to GND per layout guidelines.
3 (VO)	LDO output voltage	Delivers regulated 2.8 V; requires ≥2.2 µF ceramic output capacitor (5–5000 mΩ ESR).
4 (BYPASS)	Noise reduction bypass	Connects 10 nF capacitor to reduce high-frequency output noise and improve PSRR.
5 (GND)	Common ground	Reference node for regulation loop; must be low-impedance path to minimize noise coupling.
6 (VINH)	Inhibit control input	Logic-enable: ≥1.2 V = ON, ≤0.4 V = OFF; 1 nA leakage ensures minimal control-line loading.

Key Features

Feature	Design Value
Ultra-low dropout	150 mV at 300 mA enables >95% efficiency in 3.3 V → 2.8 V conversion for brownout resilience.
Low-noise regulation	30 µV_RMS noise floor supports clean power for ADCs, PLLs, and RF transceivers.
Logic-controlled shutdown	VINH threshold (1.4 V/0.4 V) interfaces directly with 1.8 V or 3.3 V GPIO without level-shifting.
Automotive-grade qualification	AEC-Q100 qualified (Grade 3) with −40 °C to 85 °C operation and advanced screening per AEC-Q001/Q002.
Ceramic capacitor stability	Stable with 2.2–22 µF X7R/X5R ceramics (ESR 5–5000 mΩ); eliminates need for costly tantalum alternatives.

Applications

Wearable Health Sensors

Automotive Infotainment SoC Rails

Use Scenario: Continuous ECG/PPG monitoring in compact wrist-worn devices powered by coin-cell or Li-ion.

IC Role / Device Role / Timing Role: Local 2.8 V LDO supplying analog front-end and BLE radio, enabled/disabled via MCU GPIO.

Use Value: 85 µA quiescent current extends battery life beyond 7 days; 30 µV_RMS noise prevents signal distortion in sub-mV bio-potential acquisition.

Use Scenario: Powering 2.8 V I/O banks of infotainment application processors in head units.

IC Role / Device Role / Timing Role: Post-regulator after main buck converter, providing low-noise, thermally robust supply with fast turn-on (240 µs).

Use Value: 55 °C/W thermal resistance sustains 300 mA at 85 °C ambient; AEC-Q100 qualification ensures reliability in vehicle cabin environments.

Industrial Wireless Sensor Nodes

Portable Medical Diagnostic Devices

Use Scenario: Battery-operated LoRaWAN temperature/humidity sensors deployed in remote locations.

IC Role / Device Role / Timing Role: Primary 2.8 V rail for MCU, LoRa transceiver, and precision sensor interface.

Use Value: 150 mV dropout allows operation down to 2.95 V input-maximizing usable capacity from 3.0 V nominal Li-SOCl₂ cells.

Use Scenario: Handheld ultrasound or glucose meter requiring stable, low-noise analog supply.

IC Role / Device Role / Timing Role: Dedicated LDO for op-amp signal chains and 12-bit ADC reference buffers.

Use Value: 30 µV_RMS noise and 0.004 %/mA load regulation ensure <0.5 LSB measurement error across full operating range.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6219B282MR-G	2.8 V fixed, SOT-25, 300 mA, 250 mV dropout @ 300 mA, 15 µA IQ, no shutdown pin	Lacks logic-controlled shutdown and automotive qualification; limited thermal performance (R_thJA ≈ 250 °C/W)	Preferred only for cost-sensitive consumer designs where shutdown and thermal margin are non-critical.
ROHM BD3985FP-C	2.8 V fixed, HTSOP-8, 500 mA, 200 mV dropout @ 300 mA, 60 µA IQ, integrated thermal foldback	Higher current capability but larger footprint; no AEC-Q100 grade; SVR = 45 dB @ 1 kHz	Suitable when higher output current is required and board space permits larger package; lower PSRR limits RF-sensitive use.

Compared with XC6219B282MR-G and BD3985FP-C, LDS3985PU28R uniquely balances automotive qualification, ultra-low dropout, and low-noise operation in a thermally efficient DFN6 package-making it optimal for space-constrained, safety-aware, and noise-sensitive embedded systems.

Availability

LDS3985PU28R is available at Aetrix Electronics and suitable for wearable health sensors, automotive infotainment SoC rails, and industrial wireless sensor nodes requiring stable component supply, long-term lifecycle support, and AEC-Q100-compliant sourcing.

Supply support for LDS3985PU28R 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 components for industrial, automotive, and consumer markets.

The LDS3985 belongs to ST's high-performance LDO family targeting ultra-low-power, low-noise, and automotive-qualified applications-designed specifically for battery-powered and mission-critical embedded systems demanding reliability and precision regulation.

FAQ

What is the minimum input voltage required for stable 2.8 V output at 300 mA?

The LDS3985PU28R requires VI ≥ VO + V_DROP = 2.8 V + 0.15 V = 2.95 V minimum at 300 mA (typical). Absolute minimum specified input is 2.5 V, but regulation fails below dropout threshold. For guaranteed 300 mA output, maintain VI ≥ 2.95 V across temperature and tolerance.

Can the BYPASS pin be left unconnected?

No. The BYPASS pin must be connected to a 10 nF ceramic capacitor to ground. Leaving it open degrades high-frequency PSRR and increases output noise beyond the rated 30 µV_RMS. This capacitor stabilizes the internal error amplifier and reduces sensitivity to supply ripple.

Is the DFN6 package of LDS3985PU28R lead-free and RoHS compliant?

Yes. The LDS3985PU28R uses ST's ECOPACK®2-compliant DFN6 package, fully lead-free and RoHS compliant per EU Directive 2011/65/EU. It meets JEDEC J-STD-020 moisture sensitivity level MSL3 and qualifies for standard reflow profiles including peak temperatures up to 260 °C.

Does the device require an input capacitor, and if so, what value?

Yes-an input capacitor (CI) of 1 µF ceramic is recommended per datasheet test conditions. While not strictly mandatory for stability, CI improves transient response and reduces input ripple propagation. X7R dielectric with 10% tolerance and 6.3 V rating is preferred for reliability across temperature.

LDS3985PU28R 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):: 2.8V

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)

LDS3985PU28R FAQ

1.How can I place an order for LDS3985PU28R through Aetrix?

Please submit a Request for Quotation (RFQ) for LDS3985PU28R 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 LDS3985PU28R reliable?

The price and inventory of LDS3985PU28R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LDS3985PU28R is usually 5 days.

3.What payment methods are accepted for LDS3985PU28R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LDS3985PU28R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LDS3985PU28R?

LDS3985PU28R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LDS3985PU28R 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 LDS3985PU28R?

For technical support, including LDS3985PU28R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LDS3985PU28R requirements.

6.How does Aetrix verify that LDS3985PU28R is sourced from the original manufacturer or authorized distributors?

All LDS3985PU28R 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 LDS3985PU28R meets industry standards.

7.What is the process for return or replacement of LDS3985PU28R?

All LDS3985PU28R units undergo pre-shipment inspection (PSI). If there is an issue with LDS3985PU28R, 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 LDS3985PU28R part is unused and in its original packaging.

Return procedure for LDS3985PU28R:

1.Submit a request within 90 days.

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

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