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

STMicroelectronics LD3985J25R

Name: LD3985J25R
Brand: STMicroelectronics
SKU: LD3985J25R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: LD3985J25R

Manufacturer:: STMicroelectronics

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

Package:: 5-WFBGA, FCBGA

Datasheet:: LD3985J25R.pdf

Description:: IC REG LIN 2.5V 150MA 5FLIPCHIP

Quantity:: RFQ Add To RFQ list

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Inventory:3,406

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Product details

Overview

LD3985J25R from STMicroelectronics is a 2.5 V fixed-output, 150 mA ultra-low-dropout linear regulator in SOT23-5L package, featuring 60 mV dropout at 150 mA, 30 µVRMS output noise (10 Hz–100 kHz), 60 dB PSRR at 1 kHz, and logic-controlled shutdown with 1.5 µA OFF-mode current. It powers core voltage rails in battery-operated wireless devices requiring stable low-noise bias.

For engineers reviewing the LD3985J25R datasheet, LD3985J25R pinout, LD3985J25R application, or LD3985J25R equivalent, key selection criteria include dropout performance under light/heavy load, bypass-capacitor-dependent noise suppression, thermal shutdown threshold (160 °C), and compatibility with 1 µF ceramic output capacitors without external compensation.

Technical Context

The LD3985J25R uses BiCMOS process technology to achieve ultra-low quiescent current (85 µA typ. at no load) while maintaining fast turn-on time (200 µs typ.) and tight output accuracy (±2% over temperature for 2.5 V version). Its internal architecture integrates a precision bandgap reference, error amplifier, and PMOS pass transistor with dedicated BYPASS pin for noise filtering.

It operates across 2.5 V–6 V input range and delivers regulated 2.5 V ±2% output up to 150 mA, with line regulation of ±0.1%/V and load regulation as low as 0.0004%/mA - enabling stable operation during battery discharge and dynamic load transients in portable systems.

Key Specifications

Parameter	Value and Actual Design Meaning
Output voltage	Fixed 2.5 V ±2% over −40 °C to +125 °C - ensures reliable core logic supply across automotive and industrial ambient conditions.
Max output current	150 mA guaranteed - sufficient for powering microcontroller cores, RF transceivers, or sensor signal chains without thermal derating in SOT23-5L.
Dropout voltage	60 mV typ. at 150 mA - enables >98% efficiency at 2.5 V output when input drops to 2.56 V, extending usable battery life in single-cell Li-ion or Li-poly systems.
Output noise	30 µVRMS (10 Hz–100 kHz) - meets low-noise analog/RF supply requirements without additional LDO post-regulation or ferrite beads.
PSRR	60 dB at 1 kHz, 50 dB at 10 kHz - suppresses switching noise from DC-DC converters feeding the LDO input, critical for ADC reference and PLL power domains.
Quiescent current	85 µA typ. at no load; 1.5 µA max in OFF mode - minimizes standby leakage in always-on subsystems such as real-time clocks or wake-on-event circuits.
Shutdown control	Logic-compatible inhibit pin (VIH ≥ 1.2 V, VIL ≤ 0.4 V) - allows direct interfacing with GPIOs for system-level power gating without external level-shifting.

Pinout & Package

SOT23-5L surface-mount package (2.95 mm × 1.60 mm × 1.30 mm height), RoHS-compliant and ECOPACK® certified, optimized for high-density PCB layouts and automated assembly.

Pin/Terminal	Circuit Role	Design Meaning
1 - VI	Input voltage supply	Accepts 2.5 V–6 V DC; withstands non-repetitive 6.5 V spikes for 200 ms - supports transient-tolerant battery or DC-DC front-end interfaces.
2 - GND	Power ground reference	Common return path for input, output, and inhibit circuits; requires low-inductance connection to minimize noise coupling into BYPASS and output paths.
3 - VINH	Logic inhibit control	Active-high enable: drives ON when ≥1.2 V, OFF when ≤0.4 V; must not float - ties directly to MCU GPIO or system power controller.
4 - BYPASS	Noise reduction filter node	Connects to 10 nF capacitor to ground - reduces internal reference noise contribution, lowering total output RMS noise to 30 µV.
5 - VO	Regulated output	Delivers stable 2.5 V ±2%; requires ≥1 µF ceramic capacitor (ESR ≤5 Ω) for stability - compatible with X5R/X7R dielectrics across full temperature range.

Key Features

Feature	Design Value
Ultra-low dropout	60 mV at 150 mA load - sustains regulation down to 2.56 V input, maximizing energy extraction from aging or discharged batteries.
Low-noise regulation	30 µVRMS output noise with 10 nF BYPASS cap - eliminates need for secondary filtering in precision analog, audio codec, or RF LNA supply rails.
High PSRR at low VIN	60 dB rejection at 1 kHz even when VI = VO(NOM) + 0.2 V - maintains clean output despite collapsing input from battery sag or upstream converter droop.
Thermal protection	160 °C junction shutdown with 20 °C hysteresis - prevents permanent damage during sustained overload or poor PCB thermal design without external sensing.
Fast enable response	200 µs turn-on time (95% VO) - supports rapid wake-up sequences in low-power microcontrollers and sensor hubs with strict latency budgets.

Applications

Wearable Sensor Node

Bluetooth LE Transceiver Power

Use Scenario: Compact wearable device with MEMS accelerometer, gyroscope, and BLE SoC operating from single 3.7 V Li-poly cell.

IC Role / Device Role / Timing Role: Primary 2.5 V LDO supplying digital I/O and analog front-end of sensor fusion MCU.

Use Value: 60 mV dropout extends runtime by >12% vs. standard LDOs when battery voltage falls below 2.8 V; 30 µVRMS noise avoids ADC quantization errors.

Use Scenario: Bluetooth 5.0 module requiring clean 2.5 V supply for RF synthesizer and baseband processor.

IC Role / Device Role / Timing Role: Local low-noise regulator decoupling noisy DC-DC converter output before RF section.

Use Value: 60 dB PSRR at 1 kHz attenuates switching ripple from 2 MHz buck converter, preventing carrier leakage and EVM degradation.

Industrial IoT Edge Controller

Medical Pulse Oximeter

Use Scenario: Battery-backed edge gateway with ARM Cortex-M7 MCU, CAN interface, and isolated RS-485 transceiver.

IC Role / Device Role / Timing Role: Secondary 2.5 V rail for CAN transceiver bias and isolated level-shifter logic.

Use Value: Logic-controlled shutdown (VINH) enables firmware-triggered isolation of CAN bus during sleep, reducing system quiescent current to <10 µA.

Use Scenario: Portable pulse oximeter using red/IR LED drivers and low-noise photodiode amplifier.

IC Role / Device Role / Timing Role: Precision analog supply for op-amp and ADC reference circuitry.

Use Value: 30 µVRMS noise ensures <12-bit ENOB at 1 kSPS; −40 °C to +125 °C rating supports clinical use in varying ambient environments.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
Torex XC6206P252MR	2.5 V fixed, 150 mA, 120 mV dropout at 150 mA, 45 µVRMS noise, no BYPASS pin	Lacks dedicated noise-filtering BYPASS terminal - requires larger output capacitance or external RC filter for equivalent noise performance	Select when board space limits component count and PSRR >45 dB above 10 kHz is not required
Diodes Inc. AP2210K-2.5TRG1	2.5 V fixed, 150 mA, 250 mV dropout at 150 mA, 55 µVRMS noise, integrated thermal shutdown	Higher dropout and noise reduce usable battery range and analog measurement fidelity in sensitive applications	Prefer for cost-sensitive designs where 2.5 V rail tolerates >100 mV regulation loss and >40 µVRMS noise

Compared with XC6206P252MR and AP2210K-2.5TRG1, LD3985J25R delivers superior low-load efficiency (85 µA IQ), lower noise (30 µVRMS), and finer dropout control (60 mV), making it optimal for battery-constrained, noise-sensitive embedded systems where every microwatt and microvolt matters.

Availability

LD3985J25R is available at Aetrix Electronics and suitable for wearable electronics, Bluetooth modules, industrial edge controllers, and portable medical devices requiring stable component supply with guaranteed long-term manufacturability.

Supply support for LD3985J25R 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 automotive, industrial, and consumer markets.

The LD3985 belongs to ST's ultra-low-noise, low-quiescent-current LDO family targeting battery-powered portable electronics - engineered specifically for extended runtime, minimal thermal footprint, and high signal integrity in space-constrained designs.

FAQ

What is the minimum output capacitor value required for stability?

The LD3985J25R is stable with a minimum 1 µF ceramic output capacitor (X5R/X7R), and remains stable across ±30% capacitance tolerance and full −40 °C to +125 °C temperature range. ESR must be between 5 mΩ and 5 Ω; typical 1 µF X7R capacitors meet this without external series resistance.

Can the BYPASS pin be left unconnected?

No - the BYPASS pin must be connected to a 10 nF capacitor to ground. Leaving it floating degrades output noise performance (increasing RMS noise beyond 30 µV) and may cause instability under certain load transients due to uncontrolled reference node impedance.

Does LD3985J25R support reverse-voltage protection?

No - the device lacks internal reverse-voltage protection. If reverse polarity is possible at the VI pin, an external series Schottky diode (with <0.3 V forward drop) must be added to prevent latch-up or permanent damage, as absolute maximum rating for VI is −0.3 V.

How does thermal shutdown behave during continuous overload?

Thermal shutdown activates at 160 °C junction temperature with ~20 °C hysteresis; the device latches off until junction cools to ~140 °C, then automatically resumes regulation. This protects against sustained short-circuit or excessive ambient temperature without requiring external reset circuitry.

LD3985J25R Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 5-WFBGA, FCBGA

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):: 2.5V

Voltage - Output (Max):: -

Voltage Dropout (Max):: 0.1V @ 150mA

Current - Output:: 150mA

Current - Quiescent (Iq):: 150 µA

Current - Supply (Max):: 250 µA

PSRR:: 60dB ~ 50dB (1kHz ~ 10kHz)

Control Features:: Enable

Protection Features:: Over Current, Over Temperature

Operating Temperature:: -40°C ~ 125°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 5-FlipChip (1.59x1.24)

LD3985J25R FAQ

1.How can I place an order for LD3985J25R through Aetrix?

Please submit a Request for Quotation (RFQ) for LD3985J25R 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 LD3985J25R reliable?

The price and inventory of LD3985J25R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LD3985J25R is usually 5 days.

3.What payment methods are accepted for LD3985J25R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LD3985J25R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for LD3985J25R?

LD3985J25R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your LD3985J25R 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 LD3985J25R?

For technical support, including LD3985J25R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LD3985J25R requirements.

6.How does Aetrix verify that LD3985J25R is sourced from the original manufacturer or authorized distributors?

All LD3985J25R 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 LD3985J25R meets industry standards.

7.What is the process for return or replacement of LD3985J25R?

All LD3985J25R units undergo pre-shipment inspection (PSI). If there is an issue with LD3985J25R, 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 LD3985J25R part is unused and in its original packaging.

Return procedure for LD3985J25R:

1.Submit a request within 90 days.

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

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