STMicroelectronics LD2982AM18R

Overview

LD2982AM18R from STMicroelectronics is a 50 mA fixed-output low-dropout linear voltage regulator with 1.8 V output, 120 mV dropout at 50 mA, 30 µV_RMS output noise, logic-controlled inhibit function (TTL-compatible), and SOT23-5L package. It delivers ultra-low quiescent current (75 µA at 1 mA load) and supports battery-powered portable electronics requiring stable, low-noise power rails.

For engineers reviewing the LD2982AM18R datasheet, LD2982AM18R pinout, LD2982AM18R application, or LD2982AM18R equivalent, key selection criteria include dropout voltage under light/heavy load, inhibit logic thresholds (V_IL = 0.15 V, V_IH = 2 V), bypass capacitor noise reduction (10 nF to GND), ±1% output tolerance at 25 °C, and thermal performance in SOT23-5L (R_thJA = 255 °C/W).

Technical Context

The LD2982AM18R employs a PNP pass transistor architecture enabling ultra-low dropout (as low as 1 mV at 1 mA) and minimal quiescent current across load range. Its internal feedback loop is optimized for stability with 1 µF ceramic output capacitors - especially critical for 1.8 V versions requiring ≥2.2 µF minimum capacitance.

Inhibit control operates via Pin 3 (INHIBIT): pulled low (<0.18 V) disables regulation and reduces quiescent current to <1 µA; left unconnected it must be tied to V_IN to ensure enable. The Bypass pin (Pin 4) accepts a 10 nF capacitor to ground, reducing integrated output noise to 30 µV_RMS (300 Hz–50 kHz).

Key Specifications

Pinout & Package

LD2982AM18R is housed in a compact, surface-mount SOT23-5L package (2.8 × 1.75 × 1.3 mm), RoHS-compliant and ECOPACK®-qualified.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS78218DRVR and MCP1700T-1802E/TT, the LD2982AM18R uniquely balances ultra-low dropout (120 mV), industry-leading noise (30 µV_RMS), and TTL-compatible inhibit - making it optimal for space-constrained, battery-operated analog/RF systems where both efficiency and signal integrity are non-negotiable.

Availability

LD2982AM18R is available at Aetrix Electronics and suitable for cellular handset power rails, portable medical sensor nodes, PDA core logic supplies, and digital camera image sensor bias requiring stable component supply across long-lifecycle consumer and industrial programs.

Supply support for LD2982AM18R 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 analog, microcontroller, power, and sensor solutions for automotive, industrial, and consumer markets.

The LD2982 series belongs to ST's high-performance LDO portfolio targeting ultra-low-noise, low-power portable applications - engineered specifically for battery longevity, RF signal integrity, and seamless integration into space-constrained PCB layouts.

FAQ

What is the minimum input voltage required for LD2982AM18R to regulate 1.8 V output?

The LD2982AM18R requires a minimum input voltage of 2.5 V to maintain regulation at 1.8 V output, based on its absolute maximum rating table and electrical characteristics showing stable operation starting at V_IN = 2.5 V. At 50 mA load, the 120 mV dropout means V_IN must be ≥1.92 V, but the 2.5 V lower limit ensures full specification compliance across temperature and process variation.

Can the INHIBIT pin be left floating during operation?

No - the INHIBIT pin (Pin 3) has no internal pull-up or pull-down and must never be left floating. If inhibit functionality is unused, ST specifies that the pin must be tied directly to V_IN to guarantee reliable enable operation. Floating risk causes unpredictable shutdown due to noise coupling or leakage-induced threshold crossing.

Is a bypass capacitor mandatory for achieving 30 µV_RMS output noise?

Yes - the 30 µV_RMS noise figure is explicitly measured with a 10 nF ceramic capacitor connected between the Bypass pin (Pin 4) and GND. Without this capacitor, output noise rises significantly (typical data shows >100 µV_RMS), as the internal bandgap reference and error amplifier contribute thermal noise unfiltered.

What output capacitor value is required for stability at 1.8 V output?

For 1.8 V output, ST specifies a minimum 2.2 µF ceramic capacitor with low ESR. This requirement is voltage-dependent: ≥2.2 µF applies to VO = 1.8–3.3 V, while ≥1 µF suffices for VO ≥3.8 V. Using less than 2.2 µF risks instability unless a series resistor is added to emulate required ESR per application note section 6.3.