Texas Instruments LP3985IM5X-3.3

Overview

LP3985IM5X-3.3 from Texas Instruments is a fixed-output, micropower, ultra-low-dropout CMOS voltage regulator delivering 150 mA at 3.3 V with ≤100 mV dropout at full load, 30 µVRMS output noise (10 Hz–100 kHz), and 50 dB PSRR at 1 kHz - designed for RF power amplifiers and baseband ICs in space-constrained battery-powered handsets.

For engineers reviewing the LP3985IM5X-3.3 datasheet, LP3985IM5X-3.3 pinout, LP3985IM5X-3.3 application, or LP3985IM5X-3.3 equivalent, key selection criteria include verified low-noise performance under light-to-full load, DSBGA-5 package footprint < 1.6 mm², shutdown current ≤1.5 µA, and compatibility with 1-µF ceramic output capacitors without external compensation.

Technical Context

The LP3985IM5X-3.3 uses a PMOS pass transistor architecture enabling ultra-low dropout and minimal ground current variation in dropout. Its internal 1.23-V bandgap reference feeds an error amplifier driving the pass device, with fast-turnon achieved via a dedicated 70-µA pre-charge current source on the BYPASS pin.

It integrates thermal shutdown (160°C trip, 20°C hysteresis) and short-circuit current limiting (600 mA steady-state), operates from 2.5 V to 6 V input, and maintains regulation down to −40°C junction temperature - all while consuming only 85–140 µA quiescent current across 0–150 mA load.

Key Specifications

Pinout & Package

LP3985IM5X-3.3 is packaged in a 5-pin DSBGA (YZR) with 1.502 mm × 1.045 mm body size and 0.5-mm pitch - optimized for minimal PCB area in mobile phone front-end modules.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPL720F33DBVR and MCP1804T-3302I/OT, the LP3985IM5X-3.3 delivers superior noise performance and smallest footprint for RF-critical 150-mA loads, but requires DSBGA assembly capability and external BYPASS capacitor for optimal noise suppression.

Availability

LP3985IM5X-3.3 is available at Aetrix Electronics and suitable for CDMA/GSM handset design, portable GPS receivers, and WCDMA transceiver power management requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LP3985IM5X-3.3 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 connectivity technologies for industrial, automotive, and consumer markets.

The LP3985 product line was engineered specifically for micropower, low-noise, ultra-low-dropout regulation in space-constrained portable wireless devices - prioritizing battery life extension, RF signal integrity, and minimal PCB real estate.

FAQ

What is the maximum input voltage rating for the LP3985IM5X-3.3?

The LP3985IM5X-3.3 has an absolute maximum input voltage of 6.5 V, but its recommended operating range is 2.5 V to 6 V. Operation above 6 V risks permanent damage, and below 2.5 V (or below VOUT + 0.3 V) results in loss of regulation. The LP3985IM5X-3.3 is commonly used with 3.6–4.2 V Li-ion battery inputs, where its 100-mV dropout ensures full 3.3-V output until battery discharge reaches ~3.4 V.

Does the LP3985IM5X-3.3 require an external bypass capacitor to meet its 30 µVRMS noise specification?

Yes - the 30 µVRMS output noise (10 Hz–100 kHz) specified for the LP3985IM5X-3.3 is measured with a 0.01-µF capacitor connected between the BYPASS pin and GND. Without this capacitor, typical output noise rises to 230 nV/√Hz broadband density, increasing integrated RMS noise significantly. The LP3985IM5X-3.3's internal pre-charge circuit ensures fast startup even with the BYPASS cap installed.

Can the LP3985IM5X-3.3 operate stably with a 1-µF X5R ceramic capacitor on the output?

Yes - the LP3985IM5X-3.3 is explicitly characterized and guaranteed stable with 1-µF ±30% ceramic output capacitors, including X5R dielectrics. However, X5R exhibits greater capacitance loss over temperature (−55°C to +85°C) versus X7R (−55°C to +125°C). For wide-temperature applications like automotive telematics, X7R is preferred; for consumer handsets operating 0–70°C, X5R is acceptable and widely used with the LP3985IM5X-3.3.

What is the thermal shutdown behavior of the LP3985IM5X-3.3 during sustained overload?

The LP3985IM5X-3.3 activates thermal shutdown at 160°C junction temperature with 20°C hysteresis, meaning it resumes operation only after cooling to ≤140°C. During overload, its 600-mA short-circuit current limit and thermal foldback prevent destructive power dissipation. In a typical DSBGA layout on 2-layer FR-4, the LP3985IM5X-3.3 sustains 150 mA continuously at TA = 85°C without tripping, thanks to its 255°C/W θJA rating.

Is the LP3985IM5X-3.3 pin-compatible with other members of the LP3985 family, such as the LP3985IM5-2.8?

Yes - all LP3985 variants, including LP3985IM5X-3.3 and LP3985IM5-2.8, share identical pinouts and package footprints (DSBGA-5 or SOT-23-5), enabling voltage-option interchangeability on the same PCB. The only differences are output voltage setting (laser-trimmed internal resistor divider) and minor electrical specs like load regulation slope. No layout changes are needed when substituting LP3985IM5X-3.3 for another fixed-voltage variant in the same package.