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

STMicroelectronics LDS3985PU18RY

Name: LDS3985PU18RY
Brand: STMicroelectronics
SKU: LDS3985PU18RY
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LDS3985PU18RY

Manufacturer:: STMicroelectronics

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

Package:: 6-VDFN Exposed Pad

Datasheet:: LDS3985PU18RY.pdf

Description:: IC REG LINEAR 1.8V 300MA 6DFN

Quantity:: RFQ Add To RFQ list

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Product details

Overview

LDS3985PU18RY from STMicroelectronics is a fixed 1.8 V, 300 mA low-dropout linear regulator in DFN6 (3 × 3 mm) automotive-grade package. It delivers ultra-low dropout (150 mV typ. at 300 mA), 30 µV_RMS output noise (10 Hz–100 kHz), and 85 µA typical quiescent current at no load-enabling high-efficiency power management in battery-sensitive automotive infotainment and ADAS subsystems.

For engineers reviewing the LDS3985PU18RY datasheet, LDS3985PU18RY pinout, LDS3985PU18RY application, or LDS3985PU18RY equivalent, key selection criteria include its AEC-Q100 qualification, logic-controlled shutdown (VINH ≤ 0.4 V for OFF), thermal shutdown at 160 °C, and stable operation with 2.2 µF ceramic output capacitors.

Technical Context

The LDS3985PU18RY uses a BiCMOS architecture to achieve simultaneous low dropout and low noise performance. Its internal reference and error amplifier are optimized for stability with low-ESR ceramic capacitors, eliminating need for tantalum or electrolytic types.

It integrates logic-controlled inhibit (VINH), internal current limiting, and thermal shutdown with 20 °C hysteresis. The bypass pin (BYP) accepts a 33 nF capacitor to suppress high-frequency noise, while supply voltage rejection reaches 55 dB at 1 kHz and 50 dB at 10 kHz.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 1.8 V ±2% over -40 °C to +85 °C - ensures stable core voltage for 1.8 V microcontrollers and sensors.
Max Output Current	300 mA guaranteed - supports moderate-power automotive modules without external pass devices.
Dropout Voltage	150 mV typical at 300 mA - enables operation down to 1.95 V input, critical for cold-crank battery conditions.
Quiescent Current	85 µA typical at no load; 1.5 µA max in OFF mode - extends battery life in always-on vehicle systems.
Output Noise	30 µV_RMS (10 Hz–100 kHz) - meets low-noise requirements for RF receivers and precision analog front-ends.
Supply Rejection	55 dB at 1 kHz - suppresses ripple from switching DC/DC stages feeding the LDO input.
Operating Temp	-40 °C to +85 °C (automotive grade) - qualified per AEC-Q100 Grade 3 for under-hood and cabin applications.

Pinout & Package

DFN6 (3 × 3 mm) package with exposed thermal pad (EP) on underside for enhanced heat dissipation; RoHS-compliant, ECOPACK®2 certified.

Pin/Terminal	Circuit Role	Design Meaning
1 (VI)	LDO input voltage	Accepts 2.5–6 V input; withstands non-repetitive 6.5 V spikes up to 200 ms.
2 (N.C.)	No connect	Internally unconnected; must not be wired or biased.
3 (VO)	LDO output voltage	Delivers regulated 1.8 V; requires ≥2.2 µF ceramic output capacitor (5–5000 mΩ ESR).
4 (BYP)	Bypass capacitor terminal	Connects to 33 nF capacitor to reduce high-frequency output noise and improve PSRR.
5 (GND)	Common ground	Reference node for all internal circuitry; must be low-impedance connection to PCB ground plane.
6 (VINH)	Inhibit control input	Logic-high (≥1.4 V) enables output; logic-low (≤0.4 V) disables output and reduces IQ to ≤1.5 µA.

Key Features

Feature	Design Value
Automotive qualification	AEC-Q100 Grade 3 qualified and screened per AEC-Q001/Q002 - validated for automotive production use.
Low-noise regulation	30 µV_RMS output noise with integrated BYP filtering - eliminates need for external noise-reduction networks.
Fast enable response	240 µs turn-on time (95% of VO) - supports rapid wake-up in event-driven automotive subsystems.
Thermal protection	160 °C junction shutdown with 20 °C hysteresis - prevents damage during sustained overload or poor heatsinking.
Stable with ceramics	Guaranteed stability with 2.2–22 µF ceramic output capacitors (5–5000 mΩ ESR) - reduces BOM cost and board area.

Applications

Automotive Infotainment

ADAS Camera Modules

Use Scenario: Powering 1.8 V image signal processors and MIPI CSI-2 transceivers in rear-view and surround-view camera systems.

IC Role / Device Role / Timing Role: Local low-noise post-regulator delivering clean 1.8 V supply independent of noisy main DC/DC rail.

Use Value: 30 µV_RMS noise and 55 dB SVR prevent clock jitter and image artifacts in high-resolution video streams.

Use Scenario: Supplying 1.8 V I/O and core rails for radar sensor SoCs in forward collision warning systems.

IC Role / Device Role / Timing Role: Enable-controlled local regulator enabling deep-sleep mode during radar idle cycles.

Use Value: 1.5 µA OFF-mode current minimizes standby drain on 12 V vehicle battery over extended parking periods.

Telematics Control Units

Body Control Modules

Use Scenario: Regulating 1.8 V supply for LTE/GNSS baseband processors in cellular-connected telematics gateways.

IC Role / Device Role / Timing Role: Low-dropout LDO maintaining regulation during cold-crank (6.5 V transient) and brown-out (6 V → 2.5 V) events.

Use Value: 150 mV dropout at 300 mA allows uninterrupted operation down to 1.95 V input-critical for GPS lock retention.

Use Scenario: Powering 1.8 V CAN FD transceiver I/O buffers and microcontroller peripherals in door module ECUs.

IC Role / Device Role / Timing Role: AEC-Q100 qualified LDO providing fault-tolerant 1.8 V rail with integrated thermal and current limiting.

Use Value: Internal protection eliminates need for external fuses or thermal sensors-reducing component count and failure modes.

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-noise, automotive-grade LDO applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
TLD1117LV18	1.8 V, 300 mA, 250 mV dropout (typ. at 300 mA); 45 µV_RMS noise; SOT-223 package.	Higher thermal resistance (R_thJA = 60 °C/W vs. LDS3985PU18RY's 55 °C/W); lacks BYP pin for noise optimization.	Prefer LDS3985PU18RY when board space is constrained and noise <30 µV_RMS is required.
TPS79918QDRVRQ1	1.8 V, 200 mA, 170 mV dropout (typ. at 200 mA); 25 µV_RMS noise; DFN6 (2 × 2 mm) package.	Lower max current (200 mA vs. 300 mA); tighter output tolerance (±1% vs. ±2%); higher cost.	Choose LDS3985PU18RY for cost-sensitive 300 mA designs where ±2% tolerance is acceptable.

Compared with TLD1117LV18 and TPS79918QDRVRQ1, the LDS3985PU18RY uniquely combines AEC-Q100 Grade 3 qualification, 300 mA capability, 30 µV_RMS noise, and a dedicated BYP pin in a thermally efficient DFN6 (3 × 3 mm) footprint-making it optimal for space-constrained, noise-sensitive automotive modules requiring >250 mA.

Availability

LDS3985PU18RY is available at Aetrix Electronics and suitable for automotive infotainment, ADAS camera modules, and telematics control units requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for LDS3985PU18RY 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 designing and manufacturing microcontrollers, power management ICs, sensors, and automotive-grade components with focus on energy efficiency and reliability.

The LDS3985 series belongs to ST's automotive-qualified LDO portfolio, engineered specifically for noise-sensitive, low-power subsystems in vehicles-including infotainment, driver assistance, and body electronics.

FAQ

What is the minimum input voltage required for regulation at 1.8 V output?

The LDS3985PU18RY requires a minimum input voltage of 1.95 V to maintain regulation at full 300 mA load, based on its 150 mV typical dropout voltage. At lighter loads (e.g., 1 mA), dropout drops to 0.4 mV, allowing regulation down to ~1.8004 V input. Input must remain ≥2.5 V for guaranteed specification compliance per datasheet test conditions.

Can the BYP pin be left unconnected?

No-the BYP pin must be connected to a 33 nF capacitor to ground as specified. Leaving it floating degrades high-frequency PSRR and increases output noise beyond the rated 30 µV_RMS. The capacitor stabilizes the internal reference and improves transient response; omitting it violates the design conditions used to characterize SVR and noise performance.

Is the thermal pad (EP) electrically connected internally?

No-the exposed thermal pad on the DFN6 package is not electrically connected to any internal node. It must be soldered to a large PCB copper pour for thermal conduction but should remain isolated from signal or power planes to avoid unintended coupling. ST recommends connecting it only to GND for mechanical stability and thermal relief.

Does the LDS3985PU18RY support reverse polarity protection?

No-it does not integrate reverse polarity protection. The absolute maximum rating for VI is -0.3 V; applying reverse voltage risks permanent damage. External protection-such as a series Schottky diode or ideal diode controller-is required if reverse input conditions are possible in the target application.

LDS3985PU18RY 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):: 1.8V

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 Temperature

Operating Temperature:: -40°C ~ 85°C (TJ)

Grade:: Automotive

Qualification:: AEC-Q100

Mounting Type:: Surface Mount

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

LDS3985PU18RY FAQ

1.How can I place an order for LDS3985PU18RY through Aetrix?

Please submit a Request for Quotation (RFQ) for LDS3985PU18RY 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 LDS3985PU18RY reliable?

The price and inventory of LDS3985PU18RY are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LDS3985PU18RY is usually 5 days.

3.What payment methods are accepted for LDS3985PU18RY?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LDS3985PU18RY transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LDS3985PU18RY?

LDS3985PU18RY orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LDS3985PU18RY 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 LDS3985PU18RY?

For technical support, including LDS3985PU18RY datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LDS3985PU18RY requirements.

6.How does Aetrix verify that LDS3985PU18RY is sourced from the original manufacturer or authorized distributors?

All LDS3985PU18RY 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 LDS3985PU18RY meets industry standards.

7.What is the process for return or replacement of LDS3985PU18RY?

All LDS3985PU18RY units undergo pre-shipment inspection (PSI). If there is an issue with LDS3985PU18RY, 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 LDS3985PU18RY part is unused and in its original packaging.

Return procedure for LDS3985PU18RY:

1.Submit a request within 90 days.

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

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