STMicroelectronics LD2981ABM30TR

Overview

LD2981ABM30TR from STMicroelectronics is a 100 mA fixed-output 3.0 V ultra-low-dropout linear regulator with logic-controlled inhibit function, 0.17 V typical dropout at 100 mA, 80 μA typical quiescent current in active mode, and <1 μA shutdown current - designed for battery-powered portable electronics requiring stable low-noise supply under dynamic load conditions.

For engineers reviewing the LD2981ABM30TR datasheet, LD2981ABM30TR pinout, LD2981ABM30TR application, or LD2981ABM30TR equivalent, key selection criteria include dropout voltage at 100 mA, inhibit logic thresholds (0.18 V low / 1.6 V high), ±0.75% output tolerance, 160 μVRMS noise, and SOT23-5L thermal resistance (RthJA = 255 °C/W).

Technical Context

The LD2981ABM30TR implements a PNP-based LDO architecture with internal current and thermal limiting, enabling stable regulation down to 0.17 V dropout while maintaining 160 μVRMS output noise across 300 Hz–50 kHz. Its inhibit pin (Pin 3) accepts TTL-compatible logic levels to disable output and reduce quiescent current below 1 μA without external circuitry.

It operates across –40 °C to +125 °C junction temperature, supports ceramic output capacitors as low as 2.2 μF (for 3.0 V version), and features reverse-current blocking - no body diode between VIN and VOUT - eliminating backfeed risk when VOUT > VIN.

Key Specifications

Pinout & Package

LD2981ABM30TR is housed in a RoHS-compliant SOT23-5L package (1.3 mm × 2.9 mm × 1.15 mm), optimized for space-constrained portable designs and compatible with standard reflow profiles. Thermal resistance is RthJA = 255 °C/W (still air) and RthJC = 81 °C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-dropout regulator applications.

Compared with MCP1700T-3002E/TT and NCP1117ST30T3G, LD2981ABM30TR uniquely balances 100 mA capability, sub-μA shutdown, 0.17 V dropout, and SOT23-5L size - making it optimal for portable systems where enable control, noise, and board area are co-constrained.

Availability

LD2981ABM30TR is available at Aetrix Electronics and suitable for cellular handset power, portable medical sensors, wireless headset audio, and industrial IoT edge nodes requiring stable component supply with guaranteed long-term availability.

Supply support for LD2981ABM30TR 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, specializing in automotive, industrial, power, and microcontroller solutions with broad manufacturing scale and automotive-grade quality systems.

LD2981ABM30TR belongs to ST's ultra-low-IQ LDO family, engineered specifically for battery-powered portable electronics demanding precision regulation, minimal standby power, and small-footprint integration.

FAQ

What is the minimum input voltage required for 3.0 V output at 100 mA load?

The LD2981ABM30TR requires a minimum input voltage of 3.17 V (3.0 V + 170 mV typical dropout) to maintain regulation at 100 mA. At elevated temperatures or worst-case process corners, dropout may reach 375 mV, so 3.375 V input ensures margin across full operating range.

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 unused, tie Pin 3 directly to VIN to ensure continuous operation; floating causes undefined output state and potential instability.

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

Yes - a minimum 1 μF ceramic capacitor is required on VIN, placed within 12.7 mm of the pin and returned to clean analog ground. Ceramic (X5R/X7R) is preferred for low ESR and stable capacitance over temperature; tantalum or film types are acceptable but less optimal for PSRR.

Does LD2981ABM30TR support reverse-voltage protection?

It provides reverse-current blocking: when VOUT exceeds VIN, no current flows through the pass element due to absence of an intrinsic body diode. However, it does not protect against reverse-polarity input - external diode or protection IC is required if VIN polarity reversal is possible.