onsemi NCP718BSN500T1G 500mA Low-Noise LDO Voltage Regulator: Technical Overview and Application Notes
In the realm of modern electronics, achieving clean and stable power is paramount for the performance of noise-sensitive circuits. The onsemi NCP718BSN500T1G stands out as a premier solution, a 500mA low-dropout (LDO) linear voltage regulator engineered specifically for applications where power supply noise can compromise signal integrity. This article provides a technical overview and key application notes for this robust component.
Technical Overview
The NCP718BSN500T1G is a high-performance, low-noise LDO regulator capable of delivering up to 500mA of output current with a remarkably low dropout voltage. Its primary function is to convert a higher, noisy input voltage (VIN) into a tightly regulated, clean lower output voltage (VOUT) with minimal added noise.
Key specifications that define its performance include:
Ultra-Low Output Noise: A critical feature, this LDO achieves an incredibly low output noise level of 6.5µVRMS (typical over 10 Hz to 100 kHz). This is essential for powering sensitive components like RF transceivers, precision analog-to-digital converters (ADCs), and oscillators.
Excellent Power Supply Rejection Ratio (PSRR): The device offers an outstanding PSRR of 70dB at 1kHz, effectively rejecting ripple and noise from the input supply before it can reach the output. This ensures a stable output even when the input voltage is noisy.
High Accuracy: The output voltage is accurate to within ±1.5% over line, load, and temperature variations, ensuring reliability and consistency for critical loads.
Low Dropout Voltage: With a dropout voltage of typically 180mV at 500mA, it can continue to regulate its output effectively even when the input voltage dips very close to the output level, enhancing efficiency and extending battery life in portable devices.
Wide Input Voltage Range: From 2.2V to 5.5V, it is perfectly suited for a variety of applications, including those powered by a single-cell Li-Ion battery or a 3.3V system rail.
Package: It is offered in a space-saving DFN-5 (1.2mm x 1.6mm) package, making it ideal for compact, portable consumer electronics.
Application Notes
Implementing the NCP718BSN500T1G effectively requires attention to a few key design considerations:
1. Input and Output Capacitors: Like all LDOs, stability is dependent on proper capacitance. The NCP718 is designed for stability with small, low-ESR ceramic capacitors. A 1.0µF ceramic capacitor on the input and a 2.2µF ceramic capacitor on the output are typically sufficient. These should be placed as close as possible to the regulator's pins to minimize parasitic inductance.
2. Noise Bypass Option: For applications requiring the absolute lowest noise performance, the NCP718 features a dedicated BYPASS pin. Connecting a small external capacitor (CBYP, typically 10nF) from this pin to ground further reduces the internal reference noise, pushing total output noise even lower.
3. Thermal Management: While LDOs are simple, their efficiency is not high; power is dissipated as heat (PDISS = (VIN - VOUT) ILOAD). At full load (500mA) with a large voltage differential, the package can get hot. It is crucial to ensure that the maximum junction temperature of 125°C is not exceeded. Using thermal vias and adequate copper pour on the PCB under the DFN package is essential for heat dissipation.
4. Typical Use Cases: This regulator is ideally deployed to provide a clean, quiet voltage rail for:
RF and Analog Modules: Wi-Fi, Bluetooth, GPS, and LTE modules.
Precision Sensors and Audio Codecs.
Medical and Industrial Instrumentation.
Post-regulation after a switching DC-DC converter, where it cleans up the residual switching noise.
ICGOODFIND: The onsemi NCP718BSN500T1G is an exceptional LDO voltage regulator that combines ultra-low noise, high PSRR, and high accuracy in a miniature package. It is an indispensable component for designers who need to ensure pristine power delivery for noise-sensitive circuitry, ultimately maximizing the performance and reliability of end applications.
Keywords: Low-Noise LDO, Power Supply Rejection Ratio (PSRR), Voltage Regulator, 500mA, Output Noise
