STMicroelectronics LD2985BM27R

Overview

LD2985BM27R from STMicroelectronics is a 150 mA fixed-output low-dropout linear voltage regulator with 2.7 V nominal output, ultra-low dropout (280 mV at 150 mA), sub-1 µA shutdown current, and 30 µV_rms output noise enabled by a dedicated bypass pin. It integrates logic-controlled inhibit functionality on Pin 3 (TTL-compatible), internal thermal/current limiting, and operates across –40 °C to 125 °C - deployed in battery-powered portable electronics requiring stable, quiet, low-power local regulation.

For engineers reviewing the LD2985BM27R datasheet, LD2985BM27R pinout, LD2985BM27R application, or LD2985BM27R equivalent, key selection criteria include dropout behavior at light/heavy load, inhibit threshold compatibility (V_IL ≤ 0.15 V), bypass capacitor dependency for noise reduction, and SOT23-5L thermal performance (R_thJA = 255 °C/W).

Technical Context

The LD2985BM27R employs a PNP pass transistor architecture enabling ultra-low dropout voltage - 7 mV at 1 mA and 280 mV at full 150 mA load - critical for extending battery runtime in systems with tight input–output margins. Its inhibit function is implemented as an active-low TTL-compatible control input (Pin 3) that disables regulation and reduces quiescent current to <1 µA without requiring external pull-up.

Noise performance is architecturally enhanced via a dedicated Bypass (Pin 4) terminal: connecting a 10 nF capacitor to GND reduces output noise to 30 µV_rms (300 Hz–50 kHz). The device requires ceramic output capacitors (min. 2.2 µF for 2.7 V output) and does not conduct reverse current due to absence of intrinsic body diode in the pass element.

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-178, 2.95 mm × 1.60 mm × 1.30 mm height.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6219B272MR-G and ADP160ACBZ-2.7-R7, the LD2985BM27R uniquely combines sub-1 µA inhibit shutdown, 30 µV_rms noise with bypass pin, and 280 mV dropout at full load - making it optimal for battery-constrained, noise-sensitive systems requiring precise logic-level disable control.

Availability

LD2985BM27R is available at Aetrix Electronics and suitable for portable medical sensors, industrial IoT edge nodes, automotive cabin infotainment modules, and consumer audio DAC supplies requiring stable component supply with guaranteed long-term manufacturability.

Supply support for LD2985BM27R 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 silicon solutions for automotive, industrial, and consumer markets since 1987.

The LD2985 series belongs to ST's high-performance analog LDO portfolio, engineered specifically for ultra-low-noise, ultra-low-quiescent-current regulation in space- and power-constrained portable and automotive electronics.

FAQ

What is the minimum input voltage required for stable 2.7 V output at 150 mA?

The LD2985BM27R requires a minimum input voltage of 2.98 V (2.7 V + 280 mV dropout) to maintain regulation at full 150 mA load. At lighter loads, dropout falls to 7 mV (2.707 V input required at 1 mA), enabling operation down to near-battery-dead voltage in energy-harvesting or 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 control is not needed, it must be tied directly to the IN pin to ensure continuous operation. Floating the pin risks undefined output state and potential instability due to noise coupling.

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

Yes - the 30 µV_rms noise specification is measured with a 10 nF ceramic capacitor connected between the Bypass (Pin 4) and GND. Without this capacitor, output noise rises significantly (typ. >100 µV_rms). The capacitor must be placed adjacent to the pin with short, low-inductance traces to GND.

Does the LD2985BM27R support reverse-current protection?

Yes - the internal PNP pass transistor lacks an inherent body diode, preventing reverse current flow from OUT to IN when output voltage exceeds input. Reverse current under V_REV conditions flows only through internal feedback resistors (typ. 160 µA), eliminating need for external blocking diodes in backup-supply or hot-swap configurations.