Texas Instruments LP3990MF-1.8

Overview

LP3990MF-1.8 from Texas Instruments is a 150-mA, 1.8-V fixed-output linear voltage regulator in SOT-23-5 package, designed for portable digital systems. It delivers ±1.5% output voltage accuracy at 25°C, operates from 2 V to 6 V input, achieves 120 mV typical dropout at 150 mA, and consumes only 43 µA quiescent current when enabled - ideal for battery-powered microcontroller core rails and low-power sensor interfaces.

For engineers reviewing the LP3990MF-1.8 datasheet, LP3990MF-1.8 pinout, LP3990MF-1.8 application, or LP3990MF-1.8 equivalent, key selection considerations include its ceramic-capacitor stability (1 µF min), logic-controlled enable with internal 1-MΩ pull-down, <10 nA shutdown current, 150 µV_RMS output noise, and thermal shutdown at 155°C.

Technical Context

The LP3990MF-1.8 implements a PMOS pass transistor architecture enabling ultra-low quiescent current and fast 105 µs startup time. Its internal reference and error amplifier maintain regulation across –40°C to 125°C junction temperature with no external compensation required.

It features active-high enable control with VIH = 0.95 V and VIL = 0.4 V thresholds, integrated thermal overload protection that disables output above 155°C with 15°C hysteresis, and short-circuit current limiting at 550–1000 mA - all within a 3.0 mm × 3.0 mm SOT-23-5 footprint.

Key Specifications

Pinout & Package

SOT-23-5 package (3.00 mm × 3.00 mm), thermally enhanced with exposed pad connected to GND. Pin 1 = IN, Pin 2 = GND, Pin 3 = EN, Pin 4 = N/C, Pin 5 = OUT.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar linear regulator applications.

Compared with TPL7407LPGEDR and MCP1700-1802E/TO, the LP3990MF-1.8 offers superior accuracy (±1.5% vs ±1.8%), lower dropout (120 mV vs 600 mV), and smaller SOT-23-5 footprint - making it optimal for compact, noise-sensitive, battery-operated 1.8-V digital rails.

Availability

LP3990MF-1.8 is available at Aetrix Electronics and suitable for cellular handsets, wearable sensor hubs, industrial PLC I/O modules, and medical point-of-care displays requiring stable component supply, long-term lifecycle support, and guaranteed traceability.

Supply support for LP3990MF-1.8 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 company headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.

The LP3990MF-1.8 belongs to TI's precision low-dropout linear regulator product line, engineered specifically for space-constrained, battery-powered digital applications demanding ultra-low IQ, ceramic-capacitor compatibility, and robust thermal protection.

FAQ

What is the minimum input voltage required for LP3990MF-1.8 to regulate 1.8 V?

The LP3990MF-1.8 requires a minimum input voltage of 2.0 V or (VOUT + VDO), whichever is greater. With a typical dropout of 120 mV at 150 mA, the device regulates stably from 1.92 V input - but per datasheet specifications, VIN must be ≥2.0 V to ensure full functionality across temperature and process variation. Below 2.0 V, internal circuitry may not operate reliably.

Can LP3990MF-1.8 operate without an enable signal connected?

Yes - the LP3990MF-1.8 has an internal 1-MΩ pull-down resistor on the EN pin. If left unconnected, EN defaults to GND, disabling the output and reducing quiescent current to <10 nA. To enable the regulator permanently, tie EN to VIN. No external pull-up is required unless active control is needed.

What ceramic capacitor characteristics are mandatory for stable operation of LP3990MF-1.8?

The LP3990MF-1.8 requires a 1-µF ceramic output capacitor with ESR between 5 mΩ and 500 mΩ - X7R or X5R dielectrics are recommended for stable capacitance over temperature. Input capacitor must also be ≥1 µF ceramic, placed ≤1 cm from the IN pin. Z5U/Y5V types are acceptable only if DC bias derating keeps effective capacitance ≥0.7 µF across operating voltage and temperature.

Does LP3990MF-1.8 require a thermal pad connection for safe operation at 150 mA?

Yes - the SOT-23-5 package includes an exposed thermal pad (Pin 2/GND). For reliable 150 mA operation at ambient temperatures up to 85°C, this pad must be soldered to a minimum 100 mm² copper pour connected to GND. Without proper thermal relief, junction temperature may exceed 125°C, triggering thermal shutdown and reducing output current capability.

How does the PSRR of LP3990MF-1.8 compare at different frequencies, and what does that mean for system design?

The LP3990MF-1.8 delivers 55 dB PSRR at 1 kHz and 35 dB at 10 kHz. This means it attenuates 1-kHz ripple by ~600× and 10-kHz ripple by ~55× - sufficient to suppress low-frequency switching noise from buck converters but less effective against high-frequency noise. System designers should place LP3990MF-1.8 downstream of bulk filtering and avoid sharing input traces with high-dV/dt sources.