STMicroelectronics LD2985BM30R

Overview

LD2985BM30R from STMicroelectronics is a 150 mA fixed-output low-dropout linear voltage regulator delivering 3.0 V with 280 mV dropout at 150 mA load, 30 µV_rms output noise (with 10 nF bypass capacitor), and logic-controlled inhibit shutdown reducing quiescent current to <1 µA. It serves as a local power rail regulator in portable battery-powered systems requiring ultra-low noise and standby power optimization.

For engineers reviewing the LD2985BM30R datasheet, LD2985BM30R pinout, LD2985BM30R application, or LD2985BM30R equivalent, key selection criteria include dropout performance at light/heavy loads, inhibit input logic thresholds (V_IL = 0.15 V, V_IH = 2 V), thermal resistance (R_thJA = 255 °C/W), and ceramic capacitor stability requirements for 3.0 V output.

Technical Context

The LD2985BM30R uses a PNP pass transistor architecture enabling ultra-low dropout voltage-7 mV at 1 mA and 280 mV at 150 mA-while maintaining tight output regulation (±2.4% over -40 °C to 125 °C). Its internal feedback network sets a precise 3.0 V nominal output with load regulation of ≤20 mV across 1–150 mA.

It integrates TTL-compatible inhibit control on Pin 3, allowing full shutdown with sub-µA quiescent current; the bypass pin (Pin 4) accepts a 10 nF capacitor to reduce integrated output noise to 30 µV_rms (300 Hz–50 kHz). Thermal protection and current limiting are fully internal, with no external components required for safe operation.

Key Specifications

Pinout & Package

SOT23-5L package: 5-pin surface-mount plastic package with exposed pad (no thermal pad connection specified), footprint compliant with JEDEC MO-178AB, body dimensions 2.95 × 1.60 mm, height 1.30 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6219B302MR-G and RT9193-30GB, the LD2985BM30R uniquely delivers 30 µV_rms noise via its dedicated bypass pin while maintaining industry-leading 280 mV dropout at full 150 mA load-making it optimal for noise-critical, battery-constrained applications where both ultra-low IQ and clean power are non-negotiable.

Availability

LD2985BM30R is available at Aetrix Electronics and suitable for portable medical sensors, wearable health monitors, industrial IoT edge nodes, and smart camera modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LD2985BM30R 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 silicon solutions for automotive, industrial, and consumer markets, with core expertise in analog, power, and microcontroller technologies.

The LD2985 series belongs to ST's high-performance LDO portfolio targeting ultra-low-noise, low-quiescent-current power management in space-constrained portable electronics-designed specifically for battery longevity and analog signal fidelity.

FAQ

What is the minimum input voltage required for regulation at 3.0 V output?

The LD2985BM30R 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 3.28 V. At 1 mA load, dropout drops to 7 mV, permitting regulation down to 3.007 V input-critical for maximizing battery utilization in coin-cell applications.

Can the INHIBIT pin be left unconnected?

No. The INHIBIT pin has no internal pull-up or pull-down and must never be left floating. If shutdown functionality is unused, tie Pin 3 directly to the IN pin to ensure continuous operation. Floating the pin risks unpredictable enable/disable behavior and potential output instability due to noise coupling.

Is an input capacitor mandatory, and what type is recommended?

Yes-a minimum 1 µF ceramic (X7R or better) input capacitor is mandatory for stability and transient response. It must be placed within 12.7 mm of the IN and GND pins and connected to a clean analog ground. Larger capacitance improves line transient suppression but does not degrade stability.

How does the BYPASS pin reduce output noise, and what capacitor value is required?

The BYPASS pin connects to an internal noise-reduction circuit that filters reference voltage fluctuations. A 10 nF ceramic capacitor between Pin 4 and GND lowers integrated output noise from ~100 µV_rms to 30 µV_rms (300 Hz–50 kHz). Use C0G/NP0 dielectric for best temperature stability and low parasitic inductance.