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

STMicroelectronics LDS3985M50R

Name: LDS3985M50R
Brand: STMicroelectronics
SKU: LDS3985M50R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LDS3985M50R

Manufacturer:: STMicroelectronics

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

Package:: SC-74A, SOT-753

Datasheet:: LDS3985M50R.pdf

Description:: IC REG LINEAR 5V 300MA SOT23-5

Quantity:: RFQ Add To RFQ list

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Product details

Overview

LDS3985M50R from STMicroelectronics is a fixed-output 5.0 V, 300 mA low-dropout (LDO) linear voltage regulator in SOT23-5L 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), designed for battery-powered wireless systems requiring stable local regulation with logic-controlled shutdown.

For engineers reviewing the LDS3985M50R datasheet, LDS3985M50R pinout, LDS3985M50R application, or LDS3985M50R equivalent, this page provides verified electrical specs, thermal performance, shutdown behavior, ceramic capacitor stability, and automotive-grade variant compatibility - all critical for portable power rail design and standby power optimization.

Technical Context

The LDS3985M50R uses BiCMOS process technology to achieve simultaneous low dropout and low quiescent current. Its internal architecture includes precision bandgap reference, error amplifier, PMOS pass transistor, and independent inhibit logic circuitry enabling fast turn-on (240 µs) and sub-µA OFF-mode current (1.5 µA max).

It features built-in thermal shutdown (160 °C trip), current limiting (600 mA short-circuit), and high PSRR (55 dB @ 1 kHz). Stability is guaranteed with 2.2 µF ceramic output capacitors (ESR 5–5000 mΩ), eliminating need for tantalum or electrolytic types.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 5.0 V ±2% over -40 °C to 125 °C; enables direct replacement of 5 V logic rails without external feedback.
Dropout Voltage	150 mV typical at 300 mA load; allows operation from 5.15 V input when output is 5.0 V - critical for single-cell Li-ion or 5 V bus margining.
Quiescent Current	85 µA typical at no load; reduces standby power loss in always-on subsystems like real-time clocks or sensor wake-up circuits.
Output Noise	30 µV_RMS (10 Hz–100 kHz); supports noise-sensitive analog blocks (e.g., ADC references, RF LNA bias) without additional filtering.
Supply Rejection	55 dB @ 1 kHz; suppresses ripple from noisy switching supplies feeding the LDO input - essential in mixed-signal SoC power domains.
Shutdown Current	1.5 µA maximum in OFF mode; enables deep sleep states in portable devices where total system leakage must be < 2 µA.
Thermal Shutdown	160 °C junction temperature trip with ~20 °C hysteresis; protects against sustained overload or poor PCB heatsinking in compact layouts.

Pinout & Package

SOT23-5L package: 5-pin surface-mount, 2.95 mm × 1.60 mm × 1.45 mm body, ECOPACK® compliant, rated for -40 °C to 125 °C operation.

Pin	Circuit Role	Design Meaning
1	VI	LDO input voltage (2.5–6 V DC); requires ≥1 µF ceramic bypass capacitor close to pin.
2	GND	Common ground reference for input, output, and inhibit; must connect to low-impedance ground plane.
3	VINH	Inhibit control input: ≥1.4 V = ON, ≤0.4 V = OFF; not internally biased - external pull-down required if unused.
4	BYPASS	Noise reduction node: connects to 10 nF capacitor to GND; lowers output noise by stabilizing internal reference.
5	VO	Regulated 5.0 V output; requires 2.2 µF ceramic output capacitor (5–5000 mΩ ESR) for stability.

Key Features

Feature	Design Value
Ultra-low dropout	150 mV at full 300 mA load enables use with marginal input sources (e.g., aging batteries or post-regulation buck outputs).
Logic-controlled shutdown	Dedicated VINH pin with TTL-compatible thresholds allows microcontroller-driven power gating of peripheral rails without external FETs.
Ceramic capacitor stability	Guaranteed stable with 2.2 µF ceramic CO (5–5000 mΩ ESR); eliminates cost, size, and reliability penalties of tantalum alternatives.
Low-noise regulation	30 µV_RMS broadband noise + 55 dB PSRR ensures clean supply for precision analog and RF front-end stages.
Automotive-grade option	DFN6 variant (LDS3985PU50R) qualified per AEC-Q100 Grade 3 (-40 °C to 85 °C) with advanced screening for infotainment and ADAS modules.

Applications

Mobile Phone Power Management

Wearable Sensor Node

Use Scenario: Local 5 V supply for baseband processor I/O banks and camera interface in smartphone mainboard.

IC Role / Device Role / Timing Role: Primary LDO regulator delivering stable 5 V at up to 300 mA with dynamic load step response < 10 µs.

Use Value: Enables direct integration into space-constrained layouts using only ceramic capacitors; shutdown mode cuts system standby current by >99%.

Use Scenario: Power source for BLE SoC, MEMS accelerometer, and optical heart-rate sensor in fitness tracker.

IC Role / Device Role / Timing Role: Low-noise, low-I_Q regulator supplying analog front-end and digital core during active and sleep cycles.

Use Value: 85 µA quiescent current extends battery life beyond 7 days on coin cell; 30 µV_RMS noise prevents signal corruption in biometric ADC sampling.

Industrial Handheld Terminal

Automotive Infotainment Display

Use Scenario: 5 V rail for touch controller, LCD driver, and secure element in ruggedized barcode scanner.

IC Role / Device Role / Timing Role: Local regulator with thermal protection and wide input range (2.5–6 V) accommodating varying battery voltages and USB input transients.

Use Value: 160 °C thermal shutdown prevents field failure under sealed enclosure conditions; 250 mV max dropout at 300 mA maintains regulation during peak display backlight pulses.

Use Scenario: 5 V supply for display timing controller and HDMI level-shifter in automotive head unit.

IC Role / Device Role / Timing Role: AEC-Q100 qualified LDO (via DFN6 variant) providing isolated, low-noise power in high-EMI cabin environment.

Use Value: 55 dB PSRR at 1 kHz rejects alternator ripple; automotive-grade qualification ensures reliability across temperature cycling and vibration profiles.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6206P502MR	Fixed 5.0 V, 300 mA, 250 mV dropout (typ.), 12 µA I_Q, SOT23-5; no inhibit pin or bypass pin.	Lacks logic shutdown and noise-reduction bypass capability; suited for simpler always-on rails.	Select when lowest quiescent current is primary requirement and shutdown is handled externally.
ON Semiconductor NCP1117ST50T3G	Fixed 5.0 V, 800 mA, 1.2 V dropout (min), 6 mA I_Q, SOT223; no shutdown, higher thermal resistance (R_thJA = 65 °C/W).	Higher power capability but unsuitable for battery life-critical or low-input-voltage designs.	Select only for non-portable, high-current applications where input voltage ≥ 6.2 V is guaranteed.

Compared with XC6206P502MR and NCP1117ST50T3G, LDS3985M50R uniquely balances ultra-low dropout, sub-100 µA quiescent current, integrated shutdown, and ceramic-stable 5 V regulation - making it optimal for space- and energy-constrained portable electronics where both performance and integration matter.

Availability

LDS3985M50R is available at Aetrix Electronics and suitable for mobile phone power management, wearable sensor nodes, industrial handheld terminals, and automotive infotainment displays requiring stable component supply across production volumes and extended temperature ranges.

Supply support for LDS3985M50R 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 products for industrial, automotive, and consumer markets.

The LDS3985 belongs to ST's high-performance LDO regulator family, engineered specifically for ultra-low-power, low-noise, and thermally robust local regulation in battery-powered and automotive electronics.

FAQ

What is the minimum input voltage required for stable 5.0 V output at 300 mA?

The LDS3985M50R requires a minimum input voltage of 5.15 V (5.0 V + 150 mV dropout) to maintain regulation at full 300 mA load. Below 2.5 V input, the device is not functional - its absolute minimum operating input is 2.5 V per datasheet Section 3.

Can the BYPASS pin be left unconnected?

No. The BYPASS pin must be connected to a 10 nF capacitor to ground to ensure specified output noise performance (30 µV_RMS). Leaving it floating degrades noise rejection and may cause instability in sensitive analog applications.

Is the LDS3985M50R pin-compatible with other SOT23-5L LDOs?

No. Pin assignments differ: LDS3985M50R uses Pin 3 for VINH (inhibit) and Pin 4 for BYPASS, whereas most generic SOT23-5L LDOs assign Pin 3 to GND or EN. Direct replacement requires PCB layout revision and validation of control logic timing.

Does the LDS3985M50R support ceramic output capacitors with ESR below 5 mΩ?

No. The datasheet specifies a minimum ESR of 5 mΩ for stability with 2.2 µF ceramic output capacitors. Using ultra-low-ESR MLCCs (< 5 mΩ) without series resistance risks oscillation; a 5–10 mΩ damping resistor may be required if lower-ESR caps are used.

LDS3985M50R Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

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):: 5V

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:: SOT-23-5

LDS3985M50R FAQ

1.How can I place an order for LDS3985M50R through Aetrix?

Please submit a Request for Quotation (RFQ) for LDS3985M50R 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 LDS3985M50R reliable?

The price and inventory of LDS3985M50R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LDS3985M50R is usually 5 days.

3.What payment methods are accepted for LDS3985M50R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LDS3985M50R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LDS3985M50R?

LDS3985M50R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LDS3985M50R 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 LDS3985M50R?

For technical support, including LDS3985M50R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LDS3985M50R requirements.

6.How does Aetrix verify that LDS3985M50R is sourced from the original manufacturer or authorized distributors?

All LDS3985M50R 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 LDS3985M50R meets industry standards.

7.What is the process for return or replacement of LDS3985M50R?

All LDS3985M50R units undergo pre-shipment inspection (PSI). If there is an issue with LDS3985M50R, 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 LDS3985M50R part is unused and in its original packaging.

Return procedure for LDS3985M50R:

1.Submit a request within 90 days.

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

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