STMicroelectronics LD2985BM25R

Overview

LD2985BM25R from STMicroelectronics is a 2.5 V fixed-output, 150 mA low-dropout linear voltage regulator in SOT23-5L package, featuring 280 mV dropout at 150 mA, 30 µV_rms output noise with 10 nF bypass capacitor, and logic-controlled inhibit shutdown drawing <1 µA quiescent current. It serves as a local power rail regulator in portable battery-powered systems requiring ultra-low noise and standby power efficiency.

For engineers reviewing the LD2985BM25R datasheet, LD2985BM25R pinout, LD2985BM25R application, or LD2985BM25R equivalent, this page delivers verified electrical parameters, validated SOT23-5L terminal mapping, real-world use cases in handheld electronics, and confirmed alternative regulators with documented functional trade-offs.

Technical Context

The LD2985BM25R employs a PNP pass transistor architecture enabling ultra-low dropout (7 mV at 1 mA, 280 mV at 150 mA) and stable operation with ceramic output capacitors ≥2.2 µF. Its inhibit input (Pin 3) accepts TTL-compatible logic levels (V_IL ≤ 0.15 V, V_IH ≥ 2 V) to disable regulation and reduce quiescent current to sub-µA levels.

Thermal performance is defined by R_thJA = 255 °C/W and R_thJC = 81 °C/W, supporting operation from –40 °C to +125 °C junction temperature. Output noise is actively suppressed via external 10 nF capacitor on the dedicated Bypass pin (Pin 4), reducing broadband noise to 30 µV_rms (300 Hz–50 kHz).

Key Specifications

Pinout & Package

SOT23-5L surface-mount package (3.0 × 1.6 mm footprint, 1.45 mm height), RoHS-compliant and ECOPACK® certified, optimized for high-density PCB layouts in space-constrained portable designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6219B25MR-G and BD3572EFJ-ME2, the LD2985BM25R uniquely combines ultra-low dropout (280 mV), sub-µA inhibit shutdown, and a dedicated BYPASS pin enabling 30 µV_rms noise-making it optimal for battery-powered RF and precision analog applications where all three traits are simultaneously required.

Availability

LD2985BM25R is available at Aetrix Electronics and suitable for mobile baseband power, wearable sensor hubs, industrial IoT edge nodes, and automotive cabin camera systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LD2985BM25R 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, analog chips, and MEMS sensors for industrial, automotive, and consumer markets.

The LD2985 series belongs to ST's precision low-dropout regulator product line, engineered specifically for ultra-low-noise, low-quiescent-current power delivery in portable and battery-constrained systems.

FAQ

What is the minimum input voltage required for stable 2.5 V output at 150 mA?

The LD2985BM25R requires a minimum input voltage of 2.78 V to maintain regulation at 150 mA load, based on its 280 mV dropout specification. Below this, output voltage collapses linearly with input; operation below 2.5 V input is not functional. Input must also remain within absolute maximum rating of 16 V.

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 regulation. Floating INHIBIT may cause erratic enable/disable behavior due to noise coupling, risking unintended power loss.

Is an external capacitor required on the BYPASS pin to achieve 30 µV_rms noise?

Yes-a 10 nF ceramic capacitor between BYPASS (Pin 4) and GND is mandatory to achieve the specified 30 µV_rms output noise. Without it, typical noise rises to 120 µV_rms. The capacitor must be placed adjacent to the pin with short, low-inductance traces to ground for effective high-frequency noise shunting.

What output capacitor value and type are recommended for stability?

For the 2.5 V version, ST specifies a minimum 2.2 µF X7R ceramic capacitor on the OUT pin, with ESR ≤ 100 mΩ. Tantalum capacitors may be used but are discouraged due to size, cost, and aging effects. The capacitor must be placed within 12.7 mm of Pin 5 and connected to a clean analog ground plane.