STMicroelectronics LD2985AM25R

Overview

LD2985AM25R from STMicroelectronics is a 150 mA fixed-output low-dropout linear voltage regulator with 2.5 V output, 280 mV dropout at 150 mA, 80 µA quiescent current at no load, and logic-controlled inhibit function. It operates from −40 °C to 125 °C in SOT23-5L package and targets low-noise, battery-powered portable electronics requiring precise local regulation.

For engineers reviewing the LD2985AM25R datasheet, LD2985AM25R pinout, LD2985AM25R application, or LD2985AM25R equivalent, key selection factors include ultra-low dropout under load, sub-1 µA shutdown current, 30 µV_rms output noise with 10 nF bypass capacitor, TTL-compatible inhibit control, and thermal stability across automotive-grade temperature range.

Technical Context

The LD2985AM25R uses a PNP pass transistor architecture enabling ultra-low dropout (7 mV at 1 mA, 280 mV at 150 mA) and minimal quiescent current variation across load. Its internal feedback network sets a precise 2.5 V output with ±2.4% tolerance over −40 °C to 125 °C.

Inhibit functionality is implemented via a dedicated TTL-compatible input (Pin 3) that disables regulation when pulled below 0.15 V, reducing total supply current to <1 µA. The Bypass pin (Pin 4) accepts a 10 nF capacitor to ground, lowering integrated output noise to 30 µV_rms (300 Hz–50 kHz).

Key Specifications

Pinout & Package

SOT23-5L surface-mount package (2.95 mm × 1.60 mm × 1.30 mm), RoHS-compliant, ECOPACK2 qualified, with exposed pad not connected internally.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-noise, low-quiescent-current LDO regulator applications.

Compared with XC6206P252MR and BD33IC0WEFJ-C, the LD2985AM25R uniquely combines sub-1 µA inhibit mode, 30 µV_rms noise with bypass, and 280 mV dropout at full 150 mA - making it optimal for noise-critical, battery-constrained systems requiring dynamic power gating.

Availability

LD2985AM25R is available at Aetrix Electronics and suitable for portable medical sensors, industrial IoT edge nodes, automotive cabin controllers, and audio DSP power management requiring stable component supply across extended temperature and long product lifecycles.

Supply support for LD2985AM25R 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 analog components for industrial, automotive, and consumer markets.

The LD2985 series belongs to ST's high-performance LDO portfolio targeting ultra-low-noise, ultra-low-power applications in battery-operated and thermally constrained environments.

FAQ

What is the minimum input voltage required for regulation at 2.5 V output?

The LD2985AM25R maintains regulation as long as input voltage exceeds output voltage by the dropout voltage. At 150 mA load, dropout is 280 mV, so minimum input is 2.78 V. At 1 mA load, dropout drops to 7 mV, allowing regulation from 2.507 V - enabling use with nearly depleted single-cell batteries.

How does the Bypass pin reduce output noise?

The Bypass pin connects an external 10 nF ceramic capacitor to ground, which shunts high-frequency noise from the internal reference and error amplifier. This configuration lowers integrated output noise from ~120 µV_rms to 30 µV_rms (300 Hz–50 kHz), meeting stringent requirements for precision analog and RF circuits.

Can the INHIBIT pin be left floating?

No. The INHIBIT pin has no internal pull-up or pull-down and must never be left floating. If unused, it must be tied directly to the IN pin to ensure continuous regulation. Floating causes undefined behavior and potential oscillation or excessive current draw due to indeterminate logic state.

What output capacitor value is required for stability with 2.5 V output?

For 2.5 V output, ST specifies a minimum 2.2 µF ceramic capacitor with low ESR. A 2.2 µF X7R or X5R MLCC placed within 12.7 mm of the OUT and GND pins ensures phase margin >45° and prevents oscillation across temperature and load conditions.