STMicroelectronics LD3985G25R

Overview

LD3985G25R from STMicroelectronics is a 2.5 V fixed-output, 150 mA ultra-low-dropout linear regulator in SOT23-5L package, featuring 60 mV typical dropout at 150 mA, 30 µV_RMS output noise (10 Hz–100 kHz), and logic-controlled shutdown. It operates from 2.5 V to 6 V input and is optimized for battery-powered mobile phones and wireless sensor nodes requiring stable low-noise bias under light-to-moderate load.

For engineers reviewing the LD3985G25R datasheet, LD3985G25R pinout, LD3985G25R application, or LD3985G25R equivalent, key selection criteria include dropout voltage at 150 mA, quiescent current in OFF mode (≤1.5 µA), SVR at 10 kHz (50 dB), thermal shutdown threshold (160 °C), and compatibility with 1 µF ceramic output capacitors.

Technical Context

The LD3985G25R uses a BiCMOS architecture to achieve ultra-low quiescent current (85 µA typ. at no load) while maintaining fast transient response and high PSRR-60 dB at 1 kHz and 50 dB at 10 kHz. Its internal current and thermal limiting ensure robustness during overload or ambient temperature extremes up to 125 °C junction.

Logic-controlled inhibit (VINH) enables precise system-level power sequencing: device enters OFF mode when VINH ≤ 0.4 V (leakage <1.5 µA), and resumes regulation within 250 µs when VINH ≥ 1.2 V. The BYPASS pin accepts a 10 nF capacitor to reduce high-frequency output noise by stabilizing internal reference circuitry.

Key Specifications

Pinout & Package

LD3985G25R is housed in a RoHS-compliant SOT23-5L package (2.95 mm × 1.60 mm × 1.45 mm), optimized for space-constrained portable designs and compatible with standard reflow profiles.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6206P252MR and MIC5205-2.5YM5, LD3985G25R delivers superior low-load efficiency (85 µA IQ), lower noise (30 µV_RMS vs. ≥50 µV_RMS), and integrated thermal shutdown-making it optimal for battery longevity and reliability-critical portable systems.

Availability

LD3985G25R is available at Aetrix Electronics and suitable for mobile phone power management, wireless sensor node bias, and industrial IoT edge controllers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LD3985G25R 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 devices for industrial, automotive, and consumer markets.

The LD3985 belongs to ST's ultra-low-noise, low-quiescent-current LDO family-engineered specifically for battery-powered portable electronics where runtime, thermal safety, and signal integrity are design-critical.

FAQ

What is the minimum input voltage required for LD3985G25R to maintain 2.5 V output at 150 mA?

The minimum input voltage is 2.56 V, calculated as nominal output (2.5 V) plus typical dropout (60 mV). At 150 mA load and 25 °C, the regulator sustains regulation down to this level; worst-case dropout is 100 mV over temperature, requiring ≥2.6 V for guaranteed performance across -40 °C to 125 °C.

Can LD3985G25R operate without the BYPASS capacitor?

Yes, but output noise increases significantly: the 10 nF BYPASS capacitor reduces RMS noise from ~100 µV to 30 µV (10 Hz–100 kHz). Omitting it degrades noise performance but does not affect stability or basic regulation-use only if noise sensitivity is low and board area is severely constrained.

Is LD3985G25R compatible with 1 µF X5R ceramic output capacitors?

Yes-ST specifies stability with 1–22 µF ceramic capacitors having ESR between 5 mΩ and 5000 mΩ. X5R dielectrics meet this requirement and are recommended; avoid Z5U or Y5V due to excessive capacitance drift with voltage and temperature.

How does the VINH pin behave during power-up sequencing?

VINH must exceed 1.2 V (typ.) to enable regulation; below 0.4 V, the device shuts down with ≤1.5 µA leakage. During ramp-up, output reaches 95% of 2.5 V within 250 µs after VINH crosses threshold-enabling tight synchronization with system reset controllers or PMIC sequencers.