Texas Instruments LP3985ITLX-3.1/NOPB

Overview

LP3985ITLX-3.1/NOPB from Texas Instruments is a fixed-output, ultra-low-dropout CMOS LDO voltage regulator delivering 150 mA at 3.1 V with ≤100 mV dropout at full load, 30 µVRMS output noise (10 Hz–100 kHz), and 50 dB PSRR at 1 kHz - optimized for RF power amplifier biasing in cellular handsets.

For engineers reviewing the LP3985ITLX-3.1/NOPB datasheet, LP3985ITLX-3.1/NOPB pinout, LP3985ITLX-3.1/NOPB application, or LP3985ITLX-3.1/NOPB equivalent, key selection criteria include low-noise operation with optional BYPASS capacitor support, DSBGA package footprint <1.6 mm², shutdown current ≤1.5 µA, and guaranteed stability with 1-µF ceramic output capacitance.

Technical Context

The LP3985ITLX-3.1/NOPB employs a PMOS pass transistor architecture enabling ultra-low dropout and minimal ground current variation in dropout. Its internal bandgap reference (1.23 V) feeds an error amplifier driving the pass device, with fast-turnon achieved via a 70-µA internal pre-charge current source on the BYPASS pin.

Thermal shutdown activates at 160°C with 20°C hysteresis; short-circuit current limit is 600 mA (steady-state). The EN pin provides logic-controlled enable with VIH = 1.4 V and VIL = 0.4 V, supporting direct connection to baseband processor GPIOs.

Key Specifications

Pinout & Package

LP3985ITLX-3.1/NOPB uses the YZR (DSBGA-5) package: 1.502 mm × 1.045 mm, 0.5-mm pitch, bottom-side solder balls. Requires no thermal pad; mounting per TI AN-1187.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPL720F31PDBVR and MCP1700T-3102E/TT, LP3985ITLX-3.1/NOPB uniquely combines DSBGA-5 footprint minimization (<1.6 mm²), dedicated BYPASS pin for noise optimization, and guaranteed 150-mA performance at ≤100-mV dropout - making it optimal for space-constrained RF subsystems requiring design margin.

Availability

LP3985ITLX-3.1/NOPB is available at Aetrix Electronics and suitable for cellular handset RF front-end design, portable medical sensor modules, and Bluetooth LE audio accessories requiring stable component supply, long-lifecycle availability, and RoHS-compliant packaging.

Supply support for LP3985ITLX-3.1/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, specializing in analog, embedded processing, and digital signal processing technologies for industrial, automotive, and communications markets.

The LP3985 product line was developed specifically for battery-powered wireless devices demanding ultra-low noise, micropower shutdown, and minimal PCB area - targeting CDMA, WCDMA, and GSM handset power management.

FAQ

What is the maximum input voltage rating for LP3985ITLX-3.1/NOPB?

The absolute maximum input voltage for LP3985ITLX-3.1/NOPB is 6.5 V, but the recommended operating range is 2.5 V to 6 V. Operation above 6 V risks permanent damage; operation below 2.5 V or below VOUT + 0.3 V (i.e., <3.4 V for LP3985ITLX-3.1/NOPB) results in loss of regulation. The device's 100-mV dropout specification applies only within the recommended input range.

Does LP3985ITLX-3.1/NOPB require an external bypass capacitor to meet its 30 µVRMS noise specification?

Yes - the 30 µVRMS output noise value for LP3985ITLX-3.1/NOPB is measured with a 0.01 µF capacitor connected between the BYPASS pin and GND. Omitting this capacitor increases output noise to approximately 230 nV/√Hz broadband density. The BYPASS capacitor does not affect load transient response or stability, and its value can be adjusted to trade off noise reduction versus startup time.

Can LP3985ITLX-3.1/NOPB operate with a 1-µF output capacitor in all temperature and bias conditions?

LP3985ITLX-3.1/NOPB is stable with a 1-µF ±30% X7R ceramic capacitor meeting ESR 5–500 mΩ across −40°C to 125°C. However, DC bias derating must be verified: a 0402 1-µF X7R capacitor may drop below 0.7 µF at 3.1 V bias, risking instability. TI recommends using 0603 or larger case sizes or verifying manufacturer's DC-bias curves before final selection.

What is the thermal performance difference between LP3985ITLX-3.1/NOPB in DSBGA versus SOT-23 packages?

LP3985ITLX-3.1/NOPB in DSBGA (YZR) has RθJA = 255°C/W, while the SOT-23 (DBV) version has RθJA = 220°C/W. The DSBGA's smaller footprint reduces board-level heat spreading, resulting in higher junction temperature rise under identical load and ambient conditions. For 150 mA at 3.1 V output with 4.2 V input (165 mW dissipation), DSBGA junction temperature rises ~42°C above ambient - requiring careful layout with thermal vias if ambient exceeds 85°C.

Is LP3985ITLX-3.1/NOPB pin-compatible with other members of the LP3985 family?

Yes - all LP3985 variants, including LP3985ITLX-3.1/NOPB, share identical DSBGA-5 (YZR) pinout and footprint regardless of output voltage (2.5 V–5 V). The BYPASS, EN, GND, IN, and OUT pins occupy identical physical locations across the family, enabling single PCB design reuse with only resistor or BOM changes for different voltage options.