LD2981ABM25TR

Overview

The LD2981ABM25TR is a fixed-output low-dropout voltage regulator manufactured by STMicroelectronics. It provides a nominal output voltage of 2.5 V with a guaranteed maximum output current of 100 mA. The device operates within an input voltage range of 2.5 V to 16 V and features ultra-low dropout characteristics, typically 7 mV at 1 mA load and 180 mV at 100 mA load. Quiescent current is 80 µA in on-mode and drops below 1 µA when the inhibit pin is pulled low. The component includes logic-controlled electronic shutdown via Pin 3 (INHIBIT), internal current limiting, and thermal protection. It maintains ±0.75% output voltage tolerance and exhibits an output noise voltage of 160 µVRMS. Designed for stability with low ESR ceramic capacitors, it functions across a temperature range of -40°C to +125°C.

Feature Summary

• Ultra-low quiescent current consumption with less than 1 µA draw in off mode
• Logic-controlled electronic shutdown function compatible with TTL levels
• Stable operation utilizing low ESR ceramic output capacitors
• Integrated internal current limit and thermal shutdown protection

Applications

• Battery-powered portable systems requiring extended standby life
• Cellular phones and personal digital assistants (PDA)
• Palmtop and laptop computer local regulation
• Camcorders and camera modules

Procurement Notes

Verify that the specific part number matches the required package type and output voltage variant. Confirm the presence of the 'A' suffix indicates the tighter ±0.75% voltage tolerance version. Ensure the ordering code corresponds to the SOT-23-5L package configuration. Check datasheet specifications for minimum capacitance requirements to maintain stability with ceramic capacitors.

Selection Notes

Select this component for applications demanding minimal power consumption during standby states due to its sub-1 µA shutdown current. The tight ±0.75% voltage tolerance makes it suitable for precision analog circuits. Consider the SOT-23-5L package for space-constrained designs. Verify that the system's input voltage remains within the 2.5 V to 16 V operational range under all conditions.

Part Context

This device belongs to the LD2981 series of ultra-low drop voltage regulators from STMicroelectronics. The series offers various fixed output voltages including 1.5 V, 1.8 V, 3.0 V, 3.3 V, and 5.0 V. The 'AB' designation specifically denotes the high-precision ±0.75% tolerance version. The 'M' suffix identifies the SOT-23-5L surface-mount package, while 'U' would indicate the SOT-89 package.

Replacement Considerations

LD2981CM25TR: C-version alternative with standard voltage tolerance.

FAQ

How does the INHIBIT pin affect power consumption?

Pulling the INHIBIT pin low disables the regulator, reducing the quiescent current to less than 1 µA. When not used, the pin must be tied to VI to keep the output active.

What are the capacitor requirements for stability?

The LD2981 is designed to work with low ESR ceramic capacitors. A minimum input capacitor of 1 µF is required, and the output capacitor value depends on the specific output voltage version to ensure stability.

Does the device support reverse current flow?

No inherent diode exists between input and output. If the output is forced above the input, no current flows through the pass transistor; instead, a typical reverse current of 160 µA flows to ground through internal feedback resistors.