Texas Instruments LP3985IM5X-4.7

Overview

LP3985IM5X-4.7 from National Semiconductor is a micropower, 150mA ultra-low-dropout CMOS voltage regulator optimized for battery-powered portable wireless systems. It delivers 4.7V output with ≤100mV dropout at 150mA load, 30µVrms output noise (10Hz–100kHz), and 50dB PSRR at 1kHz - enabling clean power for RF transceivers and precision analog circuitry in space-constrained handsets.

For engineers reviewing the LP3985IM5X-4.7 datasheet, LP3985IM5X-4.7 pinout, LP3985IM5X-4.7 application, or LP3985IM5X-4.7 equivalent, this page provides verified specifications, SOT-23-5 package layout, thermal shutdown behavior, enable-controlled sequencing, and validated alternatives for low-noise LDO selection in GSM/CDMA/WCDMA handset designs.

Technical Context

The LP3985IM5X-4.7 uses a CMOS pass transistor architecture to achieve ultra-low quiescent current (≤165µA at 150mA) and minimal dropout voltage - critical for extending battery life in deep-discharge conditions. Its internal bandgap reference and bypass-capacitor-assisted startup ensure stable 4.7V regulation across −40°C to +125°C junction temperature.

It integrates logic-controlled enable (VEN), thermal shutdown (160°C trip), and short-circuit current limiting (600mA steady-state). The device maintains >50dB PSRR down to VIN = VOUT + 0.2V, supporting robust operation under noisy supply rails common in RF front-end power domains.

Key Specifications

Pinout & Package

SOT-23-5 package (NS package MF05A), 2.92mm × 1.6mm footprint, 1.1mm height - designed for high-density PCB layouts in mobile phone mainboards and wearable modules.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6206P472MR and AP2204K-4.7TRG1, the LP3985IM5X-4.7 uniquely combines 150mA capability, 30µVrms noise, and a dedicated BYPASS pin - making it the only option among the three that supports both high-current and ultra-low-noise operation in a single SOT-23-5 package.

Availability

LP3985IM5X-4.7 is available at Aetrix Electronics and suitable for CDMA/GSM handset design, portable audio subsystems, and wireless sensor node development requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for LP3985IM5X-4.7 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

National Semiconductor was a U.S.-based analog semiconductor pioneer, acquired by Texas Instruments in 2011. Its LDO portfolio emphasized ultra-low-noise, micropower, and high-PSRR regulation for portable electronics.

The LP3985 series was engineered specifically for space-constrained, battery-powered wireless devices - delivering ultra-low dropout, fast enable response, and ceramic-capacitor stability without sacrificing noise performance or thermal robustness.

FAQ

What is the maximum input voltage for LP3985IM5X-4.7?

The LP3985IM5X-4.7 supports an absolute maximum input voltage of 6.5V, with recommended operating range from 2.5V to 6.0V. Exceeding 6.5V risks permanent damage per Absolute Maximum Ratings. For reliable operation across temperature, maintain VIN ≤6.0V and ensure sufficient margin above VOUT to sustain regulation - e.g., VIN ≥4.9V for full 150mA load at 4.7V output.

Does LP3985IM5X-4.7 require an external bypass capacitor for basic operation?

No, the LP3985IM5X-4.7 functions correctly without the BYPASS capacitor. That terminal is optional and used solely to reduce output noise: connecting a 0.01µF NPO/COG ceramic capacitor between BYPASS and GND lowers RMS noise from 30µV to ~20µV. Omitting it has no effect on stability, load transient response, or regulation accuracy - only noise performance is impacted.

What is the shutdown current of LP3985IM5X-4.7 when disabled?

The LP3985IM5X-4.7 draws ≤1.5µA quiescent current in disable mode (VEN ≤0.4V), as specified in the Electrical Characteristics table. This ultra-low shutdown current preserves battery capacity in always-connected IoT sensors and standby circuits. Note that this value is measured at TJ = 25°C; leakage remains below 2.5µA across the full −40°C to +125°C operating range.

Can LP3985IM5X-4.7 be used with a 0.7µF output capacitor?

Yes - the LP3985IM5X-4.7 is stable with output capacitance as low as 0.7µF (±30%), per the Recommended Output Capacitor table. However, 1.0µF is the nominal value and ensures optimal transient response and PSRR. Using 0.7µF may marginally degrade high-frequency rejection and increase output impedance above 100kHz, but does not compromise stability or regulation under static loads.

Is LP3985IM5X-4.7 pin-compatible with other LP3985 variants in SOT-23-5?

Yes - all LP3985 SOT-23-5 variants (e.g., LP3985IM5X-3.3, LP3985IM5X-5.0) share identical pinout, package dimensions (MF05A), and thermal characteristics. Only the output voltage differs. This allows drop-in replacement during prototyping or BOM optimization, provided the target application tolerates the specific fixed output voltage and associated load regulation behavior.