Texas Instruments LP3991TLX-1.7/NOPB

Overview

LP3991TLX-1.7/NOPB from Texas Instruments is a fixed-output 1.7-V, 300-mA low-dropout linear regulator in a 4-pin DSBGA package, designed for post-regulation of DC-DC converters and battery-powered digital loads. It operates from 1.65 V to 4 V input, delivers ±1% output accuracy at room temperature, features 125-mV dropout at full load, and maintains stability with 2.2-µF ceramic output capacitors.

For engineers reviewing the LP3991TLX-1.7/NOPB datasheet, LP3991TLX-1.7/NOPB pinout, LP3991TLX-1.7/NOPB application, or LP3991TLX-1.7/NOPB equivalent, key selection criteria include ultra-low quiescent current (50 µA at 1 mA), fast 100-µs startup time, PSRR of 65 dB at 1 kHz, and compatibility with 0402-size ceramic capacitors in space-constrained portable designs.

Technical Context

The LP3991TLX-1.7/NOPB integrates an internal PMOS pass transistor with thermal shutdown and short-circuit protection, enabling robust operation across –40°C to +125°C junction temperature. Its enable pin features a 1.2-MΩ internal pulldown resistor and defined VIH/VIL thresholds (0.95 V / 0.4 V) for reliable logic-level control.

Designed specifically for low-noise digital rail regulation, it achieves 280 µVRMS output noise (10 Hz–100 kHz) and exhibits load transient response of ≤110 mV for 1–300 mA steps. Input voltage headroom is minimized via low dropout-110 mV typical at 300 mA-and supports direct use after buck converters with ≥1.65 V minimum input.

Key Specifications

Pinout & Package

LP3991TLX-1.7/NOPB uses a 4-pin DSBGA (YZR) package measuring 1.43 mm × 0.96 mm with bottom-side solder bumps. The package is optimized for minimal PCB footprint and thermal conduction through the four terminals to the PCB.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPL720F17-DBVR and MCP1700T-1702E/TT, LP3991TLX-1.7/NOPB uniquely combines 300-mA capability, 1.65-V minimum input, integrated EN control, and DSBGA footprint-making it the only option for compact, high-current, battery-optimized digital rails requiring full feature set.

Availability

LP3991TLX-1.7/NOPB is available at Aetrix Electronics and suitable for mobile processor core rails, wearable sensor hubs, USB-powered IoT nodes, and industrial handheld terminals requiring stable component supply with guaranteed long-term sourcing.

Supply support for LP3991TLX-1.7/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 company headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.

The LP3991TLX-1.7/NOPB belongs to TI's precision low-dropout regulator product line, engineered specifically for space-constrained, battery-operated digital systems demanding ultra-low noise, fast transient response, and seamless integration with DC-DC converters.

FAQ

What is the minimum input voltage required for LP3991TLX-1.7/NOPB to regulate at 1.7 V?

The LP3991TLX-1.7/NOPB requires a minimum input voltage of 1.825 V to maintain regulation at 1.7 V under full 300-mA load, based on its 125-mV typical dropout specification. At lighter loads, it can operate down to 1.65 V input, but full-load regulation begins at VIN ≥ VOUT + VDO = 1.7 V + 0.125 V. This makes LP3991TLX-1.7/NOPB ideal for post-buck applications where upstream converters deliver ≥1.8 V nominal output.

Can LP3991TLX-1.7/NOPB operate with a 2.2-µF output capacitor?

Yes, LP3991TLX-1.7/NOPB supports a 2.2-µF ceramic output capacitor because its fixed 1.7-V output exceeds the 1.5-V threshold specified for reduced capacitance. However, using 2.2 µF instead of the recommended 4.7 µF may increase load transient deviation by ~10–15%, as documented in the datasheet. For applications with aggressive load steps (e.g., CPU burst), 4.7 µF is preferred to maintain ≤110 mV deviation.

Does LP3991TLX-1.7/NOPB require an external pull-up on the EN pin?

No, LP3991TLX-1.7/NOPB does not require an external pull-up on the EN pin because it includes an internal 1.2-MΩ pulldown resistor to GND. When left unconnected, EN defaults to logic low and the device remains disabled. To enable operation, drive EN to ≥0.95 V (e.g., tie directly to VIN or controlled GPIO). This eliminates external components and simplifies always-on or sequenced power designs.

What is the thermal performance of LP3991TLX-1.7/NOPB in its DSBGA package?

LP3991TLX-1.7/NOPB in the YZR DSBGA package has a junction-to-board thermal resistance (RθJB) of 112.9°C/W and junction-to-ambient (RθJA) of 189.7°C/W on a high-K test board. With 300-mA load and 3.6-V input, power dissipation is ~0.57 W, resulting in ~108°C junction rise above ambient. Full-rated operation is supported up to +85°C ambient, making LP3991TLX-1.7/NOPB suitable for sealed handheld enclosures without forced airflow.

Is LP3991TLX-1.7/NOPB compatible with X5R and X7R ceramic capacitors?

Yes, LP3991TLX-1.7/NOPB is explicitly validated for use with X5R and X7R dielectric ceramic capacitors on both input and output. These types maintain sufficient capacitance across temperature and DC bias-critical for stability. Y5V and Z5U capacitors are discouraged due to >50% capacitance loss over temperature, which risks instability. For 4.7-µF output, X7R is preferred for –40°C to +125°C operation; X5R suffices for 0°C to +85°C applications.