Texas Instruments LP3891ES-1.5/NOPB

Overview

LP3891ES-1.5/NOPB from Texas Instruments is a 0.8A ultra-low-dropout linear regulator with CMOS N-MOS pass transistor architecture, delivering 1.5V fixed output at ±1.5% accuracy (25°C), 100mV typical dropout at 0.8A, and 60nA shutdown current - designed for high-efficiency post-regulation in DSP, microcontroller core, and server I/O power supplies.

For engineers reviewing the LP3891ES-1.5/NOPB datasheet, LP3891ES-1.5/NOPB pinout, LP3891ES-1.5/NOPB application, or LP3891ES-1.5/NOPB equivalent, this page provides verified package mapping (DDPAK/TO-263, 5-pin), confirmed thermal performance (θ_JA ≈ 40°C/W with ≥1.5 in² copper), real-world stability requirements (≥10µF tantalum output cap), and validated alternative options for 1.5V LDO replacement in industrial and embedded systems.

Technical Context

The LP3891ES-1.5/NOPB uses a dual-rail architecture: VIN supplies load current while VBIAS (4.5–6V) drives the N-MOS gate independently, enabling operation with input as low as (V_OUT + V_DO). Its CMOS design ensures 3mA typical ground current at full load and 60nA quiescent current in shutdown - critical for battery-backed or always-on systems.

Stability relies on ≥10µF output capacitance with ESR between 0.001Ω–0.1Ω (tantalum recommended); ceramic caps alone are unstable due to sub-10mΩ ESR. The device integrates over-temperature and over-current protection, with junction temperature rated from −40°C to +125°C and thermal shutdown activation above +150°C.

Key Specifications

Pinout & Package

LP3891ES-1.5/NOPB is housed in a thermally enhanced DDPAK/TO-263 (KTT) 5-pin package with exposed thermal pad soldered to PCB copper plane for heat dissipation. Pin 1 is marked by notch or bevel on top edge; pin 3 is the exposed thermal tab (GND).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 1.5V ultra-low-dropout LDO applications.

Compared with TPS7A4700RGWR and MCP1826T-1502E/DB, LP3891ES-1.5/NOPB uniquely supports 1.6V minimum VIN via VBIAS, delivers 60nA shutdown current, and achieves 100mV dropout in TO-263 - making it optimal for ultra-low-input, low-power, thermally demanding 1.5V LDO applications.

Availability

LP3891ES-1.5/NOPB is available at Aetrix Electronics and suitable for server I/O power, DSP core supply, microcontroller power, SMPS post-regulation, and industrial embedded systems requiring stable component supply with guaranteed long-term sourcing.

Supply support for LP3891ES-1.5/NOPB 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management ICs, with decades of expertise in high-reliability linear regulators and power solutions.

The LP3891 product line was engineered for high-current, ultra-low-dropout regulation in thermally constrained environments - targeting DSP, microcontroller, and server power applications where efficiency, noise, and thermal performance are critical.

FAQ

What is the minimum input voltage required for LP3891ES-1.5/NOPB to regulate 1.5V output?

The LP3891ES-1.5/NOPB requires VIN ≥ (V_OUT + V_DO) = 1.5V + 0.1V = 1.6V under 0.8A load in DDPAK package. However, VBIAS must be supplied separately at 4.5–6V to enable gate drive - so the absolute minimum VIN is 1.6V, independent of VBIAS level. This dual-rail architecture allows operation far below what single-supply LDOs support.

Can LP3891ES-1.5/NOPB be used with ceramic output capacitors?

No - LP3891ES-1.5/NOPB is not stable with ceramic output capacitors alone due to their sub-10mΩ ESR. The datasheet explicitly states ceramic caps are unsuitable unless combined with ≥85% tantalum capacitance (e.g., 10µF tantalum + ≤1.5µF ceramic). Using pure ceramic output caps risks oscillation and output voltage instability across temperature and load.

What thermal performance can be expected from LP3891ES-1.5/NOPB in DDPAK package?

When mounted on ≥1.5 in² of 1-ounce copper, LP3891ES-1.5/NOPB achieves θ_JA ≈ 40°C/W. At 0.8A load with 1.6V input (0.1V dropout), power dissipation is 80mW - resulting in ~3.2°C junction rise above ambient. Even at worst-case 5.5V input, dissipation remains <3.5W, keeping junction temperature within −40°C to +125°C spec with proper copper layout.

Does LP3891ES-1.5/NOPB require an input capacitor, and what type is recommended?

Yes - LP3891ES-1.5/NOPB requires ≥10µF input capacitance for stability and source impedance control. Ceramic capacitors are preferred for the input due to low ESR and wide temperature stability; tantalum is acceptable. Aluminum electrolytics are discouraged below +10°C due to ESR drift, and must be rated for ≥100kHz if used.

How does the S/D pin function, and what external components are needed for reliable shutdown?

The S/D pin is an active-low shutdown control requiring a pull-up resistor (10–100kΩ) to VBIAS or VIN. Driving it below 0.3V disables output with 60nA leakage; pulling it high enables regulation. If driven by a rail-to-rail CMOS output, the pull-up may be omitted. Leaving S/D floating or unconnected causes undefined behavior and potential malfunction of LP3891ES-1.5/NOPB.