STMicroelectronics LD3980PU135R

Overview

LD3980PU135R from STMicroelectronics is a 1.35V fixed-output, 300mA low-dropout linear regulator in DFN6 (3x3) package, featuring 130mV typical dropout at full load, ±1.0% output accuracy at 25°C, 110µA typical quiescent current at no load, and logic-controlled active-low shutdown. It operates from 1.7V to 3.6V input and is optimized for battery-powered mobile phones and PDAs.

For engineers reviewing the LD3980PU135R datasheet, LD3980PU135R pinout, LD3980PU135R application, or LD3980PU135R equivalent, key selection criteria include ultra-low dropout under 300mA load, ceramic capacitor compatibility down to 1µF, thermal shutdown at 140°C, shutdown current below 0.5µA, and guaranteed stability across -40°C to 85°C ambient.

Technical Context

The LD3980PU135R uses a P-channel MOSFET pass element with precision bandgap reference (0.7V) and error amplifier feedback loop, enabling stable regulation with minimal headroom. Its internal current limiting caps peak output at 610mA and short-circuit current at 650mA.

Thermal protection activates at 140°C junction temperature with ~15°C hysteresis, causing pulsed output during sustained overload. Shutdown control is active-low on pin 5 (SHDN), reducing total supply current to ≤0.5µA when asserted.

Key Specifications

Pinout & Package

LD3980PU135R is housed in a thermally enhanced DFN6 (3mm × 3mm, 0.75mm height) package with exposed thermal pad. Pin 1 is OUT; pins 2–3 are NC; pin 4 is GND; pin 5 is SHDN (active-low); pin 6 is IN. The exposed pad must be soldered to PCB ground plane for optimal thermal performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6206P132MR and RT9193-13GB, LD3980PU135R delivers tighter output tolerance (±1.0%), lower dropout (130mV vs ≥200mV), and superior shutdown efficiency (0.5µA), making it optimal for high-accuracy, long-runtime battery applications where thermal management and ceramic capacitor integration are design priorities.

Availability

LD3980PU135R is available at Aetrix Electronics and suitable for mobile phone baseband power, wireless headset audio cores, PDA application processor rails, and cordless phone DECT subsystems requiring stable component supply, consistent parametric performance, and long-term lifecycle support.

Supply support for LD3980PU135R 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing silicon solutions for automotive, industrial, and consumer markets since 1987.

The LD3980 belongs to ST's high-efficiency, low-IQ LDO portfolio targeting portable battery-powered equipment; it was engineered specifically to extend runtime while maintaining tight regulation under dynamic load and low-input-voltage conditions.

FAQ

What is the minimum input voltage required for stable 1.35V output at 300mA?

The LD3980PU135R requires a minimum input voltage of 1.48V (1.35V + 130mV dropout) to maintain regulation at 300mA load. Below this, output voltage collapses linearly with input; operation down to 1.7V input is specified, but usable headroom begins at 1.48V.

Can LD3980PU135R be used with aluminum polymer capacitors instead of ceramic?

Yes, aluminum polymer capacitors may be used if their ESR falls within 10–5000mΩ and capacitance is ≥1µF, but ceramic is strongly preferred: the device is characterized and guaranteed stable with 1µF X5R/X7R ceramics, which offer lower ESR, smaller size, and better high-frequency noise filtering than polymer alternatives.

How does the thermal shutdown behave during continuous overload?

When junction temperature exceeds 140°C, the LD3980PU135R disables the pass transistor and enters thermal shutdown. It remains off until temperature drops ~15°C, then re-enables-creating automatic on-off cycling. This protects against permanent damage but causes pulsed output; sustained overload must be addressed at system level.

Is the exposed thermal pad electrically connected internally?

No-the exposed pad on the DFN6 package is not electrically connected to any internal node; it is solely for thermal conduction. ST recommends soldering it to a large PCB ground plane using ≥4 thermal vias to maximize heat transfer and keep junction temperature within -40°C to 85°C operating range.