**LT1761IS5-3#TRMPBF: A Comprehensive Guide to the 3V, Low-Noise LDO Voltage Regulator**

In the world of electronic design, achieving a clean, stable, and reliable power supply is paramount. For applications sensitive to noise and power quality, **low-dropout (LDO) linear regulators** are the components of choice. Among them, the **LT1761IS5-3#TRMPBF** from Analog Devices stands out as a premier solution for 3V regulation. This comprehensive guide delves into its key features, applications, and design considerations.

The LT1761IS5-3#TRMPBF is a specific model in the LT1761 series, fixed to provide a precise **3.3V output** from an input voltage range of 2.85V to 20V. Its defining characteristic is its remarkably **low dropout voltage**—typically 300mV at full load. This means it can continue to regulate its output even when the input voltage dips to just 3.6V, making it exceptionally efficient in battery-powered systems where the input voltage decays over time.

A primary advantage of this regulator is its **ultra-low noise performance**. Unlike switching regulators that generate significant high-frequency noise, the LT1761IS5-3#TRMPBF utilizes advanced architecture to achieve a noise output of just **20μVRMS over a 10Hz to 100kHz bandwidth**. This makes it indispensable for powering sensitive analog circuitry such as **RF modules, precision sensors, audio amplifiers, and data converters (ADCs/DACs)**, where noise on the supply rail would directly degrade system performance.

Beyond low noise, the device offers excellent **line and load regulation** and **outstanding power supply rejection ratio (PSRR)**. Its high PSRR, typically 75dB at 1kHz, allows it to effectively attenuate ripples and noise coming from the input supply, acting as a clean filter between a noisy primary power source and a sensitive load.

Housed in a compact **SOT-23-5 package**, the LT1761IS5-3#TRMPBF is designed for space-constrained applications. Despite its small size, it incorporates essential protection features like **reverse battery protection, current limiting, and thermal shutdown**, safeguarding both the regulator and the load under fault conditions. Its maximum output current of 100mA is well-suited for powering microcontrollers, low-power FPGAs, and other subsystem components.

Designing with this LDO is straightforward. While it requires only input and output capacitors for stability, careful component selection is crucial. A 10μF ceramic capacitor on the output is typically sufficient to ensure stability and provide good transient response. For the lowest possible noise, the optional bypass (BYP) pin can be used with a small external capacitor to further reduce output noise.

**ICGOOODFIND Summary**: The LT1761IS5-3#TRMPBF is a high-performance, low-noise LDO regulator that provides a critical combination of ultra-low noise, high PSRR, and low dropout voltage in a miniature package. It is the ideal power management solution for noise-sensitive applications across telecommunications, industrial sensing, medical instrumentation, and portable battery-operated devices, ensuring a pristine and stable 3.3V supply where it matters most.

**Keywords**: Low-Dropout (LDO) Regulator, Ultra-Low Noise, Power Supply Rejection Ratio (PSRR), 3.3V Output, SOT-23-5 Package.