Texas Instruments LP3985ITL-3.1

Overview

LP3985ITL-3.1 from National Semiconductor is a micropower, 150mA ultra-low-noise ultra-low-dropout CMOS voltage regulator optimized for battery-powered portable wireless systems. It delivers 3.1V output from 2.5–6.0V input, achieves ≤100mV dropout at 150mA load, maintains 30µVrms output noise (10Hz–100kHz), and consumes ≤1.5µA in shutdown - enabling extended runtime in CDMA/GSM handsets and portable information appliances.

For engineers reviewing the LP3985ITL-3.1 datasheet, LP3985ITL-3.1 pinout, LP3985ITL-3.1 application, or LP3985ITL-3.1 equivalent, key selection criteria include its 3.1V fixed output, 5-bump thin micro SMD (TLA05) package, logic-controlled enable, stability with 1µF ceramic output capacitor, and guaranteed operation across −40°C to +125°C junction temperature.

Technical Context

The LP3985ITL-3.1 implements a CMOS-based LDO architecture with internal bandgap reference and active bypass capacitor pre-charge circuitry. Its low-quiescent-current design ensures minimal ground current increase in dropout, preserving battery life in deep-discharge conditions.

It features integrated thermal shutdown (160°C trip) and short-circuit current limiting (600mA steady-state), while maintaining >50dB PSRR at 1kHz under VIN = VOUT + 0.2V. The device operates stably with 0.7–1.3µF X7R ceramic output capacitors and supports optional 0.01µF noise-reduction bypass capacitance without degrading load transient response.

Key Specifications

Pinout & Package

LP3985ITL-3.1 uses the thin micro SMD (TLA05) package: 5-bump, 1.006mm × 1.463mm footprint, 0.6mm height, non-solder-mask-defined (NSMD) pads. JEDEC-compliant pin numbering applies.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6206P312MR and RT9193-31GB, LP3985ITL-3.1 offers the lowest noise (30µVrms) and smallest footprint (1.0mm × 1.5mm), making it optimal for space-constrained, noise-sensitive RF sections where 150mA suffices.

Availability

LP3985ITL-3.1 is available at Aetrix Electronics and suitable for CDMA/GSM handset manufacturing, portable information appliance production, and wireless headset assembly requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for LP3985ITL-3.1 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 and mixed-signal semiconductor company acquired by Texas Instruments in 2011; its legacy LDO portfolio remains widely deployed in portable electronics.

The LP3985 series was designed specifically for space- and power-constrained wireless handsets, emphasizing ultra-low noise, micropower shutdown, and micro SMD integration to meet aggressive miniaturization goals in 2G/3G mobile platforms.

FAQ

What is the maximum input voltage rating for LP3985ITL-3.1?

The absolute maximum input voltage for LP3985ITL-3.1 is 6.5V, but the recommended operating range is 2.5V to 6.0V. Exceeding 6.0V risks violating the specified electrical characteristics and may trigger internal protection circuits. For reliable operation in battery-powered systems, maintain VIN ≤ 6.0V - especially important when using fully charged Li-ion cells (4.2V) with boost-fed rails.

Does LP3985ITL-3.1 require an external bypass capacitor for basic operation?

No, LP3985ITL-3.1 functions correctly without the BYPASS capacitor; it is optional and used solely to reduce output noise. The device achieves 30µVrms noise with the 0.01µF capacitor, but operates at 42µVrms typical without it. The BYPASS pin must be left floating or grounded only via the capacitor - direct grounding degrades regulation accuracy due to bandgap reference loading.

What output capacitor types are validated for LP3985ITL-3.1 stability?

LP3985ITL-3.1 is validated with 1.0µF ±30% X7R ceramic capacitors (0402/0603) having ESR between 5mΩ and 500mΩ. X5R is acceptable for 0°C–70°C ambient, but X7R is required for full −40°C to +125°C operation. Tantalum capacitors are supported only if rated for surge current and meeting 0.7µF minimum capacitance after DC bias derating - however, ceramics are strongly preferred for size, cost, and ESR consistency.

How does the enable function behave on LP3985ITL-3.1 during power sequencing?

LP3985ITL-3.1 turns on when VEN rises above 1.4V (VIH) and turns off when VEN falls below 0.4V (VIL). During sequencing, tying VEN directly to VIN ensures immediate activation at power-up. For controlled startup, drive VEN from a GPIO with rail-to-rail swing; avoid open-drain outputs without pull-up, as leakage could cause partial enable. The 200µs turn-on time begins at VIH crossing, not power rail stabilization.

Is LP3985ITL-3.1 compatible with lead-free reflow profiles?

Yes, LP3985ITL-3.1 is RoHS-compliant and qualified for standard lead-free reflow profiles with peak temperatures up to 260°C. The thin micro SMD (TLA05) package uses SnAgCu solder and withstands JEDEC J-STD-020D moisture sensitivity level 1 (MSL-1), meaning floor life is unlimited at ≤30°C/60% RH. Pre-baking is not required unless exposed to humid environments exceeding MSL-1 conditions.