onsemi NCP785AH33T1G 3V LDO Voltage Regulator: Features and Application Circuits

The onsemi NCP785AH33T1G is a high-performance, low-dropout (LDO) linear voltage regulator designed to deliver a fixed 3.3V output from a higher input voltage source. Renowned for its exceptional accuracy, low noise, and high power supply rejection ratio (PSRR), this component is an ideal choice for powering sensitive analog and digital circuits where clean and stable voltage is paramount.

Key Features

The NCP785AH33T1G stands out in the crowded LDO market due to its robust set of features tailored for modern electronic applications.

High Accuracy and Low Dropout Voltage: The regulator maintains an output voltage accuracy within ±2% and features a low dropout voltage, enabling it to continue regulating even when the input voltage dips very close to the output level. This maximizes efficiency and extends battery life in portable devices.

Excellent Noise Performance: With extremely low output noise (typically 30µV RMS), this LDO is perfectly suited for powering noise-sensitive components like RF transceivers, precision sensors, audio codecs, and PLLs, ensuring signal integrity is not compromised.

High Power Supply Rejection Ratio (PSRR): It offers a high PSRR of up to 70dB at 1kHz, effectively rejecting ripples and noise from the input power supply. This acts as a clean filter, isolating the load from input voltage variations.

Wide Input Voltage Range: Operating with an input voltage range from 4.0V to 24V, it offers great flexibility, allowing it to be used with various power sources, including unregulated wall adapters and batteries.

Protection Features: The device includes crucial internal protection circuits such as current limiting and thermal shutdown, safeguarding both the regulator and the downstream circuitry from damage under fault conditions.

Low Quiescent Current: It consumes a very low ground current, which is critical for applications that demand high efficiency, especially in battery-powered "always-on" systems.

Typical Application Circuits

The NCP785AH33T1G is simple to implement, requiring only a few external components for most applications.

1. Standard 3.3V Regulation Circuit

The most common application is a basic voltage regulation circuit. The design requires an input capacitor (C_IN, typically 1µF to 10µF) placed close to the IC's input pin to ensure stability and improve transient response. An output capacitor (C_OUT, typically 1µF to 22µF) with an Equivalent Series Resistance (ESR) between 50mΩ and 1Ω is critical for maintaining loop stability and filtering the output. A ceramic capacitor is usually recommended.

2. Enhanced Noise Filtering Circuit

For applications demanding the absolute lowest noise performance (e.g., high-resolution ADCs or DACs), an additional RC filter can be added at the output. A small resistor (e.g., 1Ω) in series with a second capacitor to ground after the main output capacitor can further reduce high-frequency noise, pushing performance beyond the already excellent native specs of the LDO.

3. High-Current Load Support

While the NCP785AH33T1G can deliver up to 500mA, proper PCB layout is essential for optimal performance. Wide traces for the input, output, and ground paths are necessary to minimize parasitic resistance and inductance. The thermal pad must be soldered to a sufficient copper pour on the PCB to act as a heatsink, dissipating heat under high load conditions and preventing premature thermal shutdown.

ICGOODFIND Summary

The onsemi NCP785AH33T1G is a premium LDO voltage regulator that excels in providing an exceptionally clean and stable 3.3V power rail. Its standout combination of high PSRR, ultra-low noise, and wide input voltage range makes it an superior solution for powering critical subsystems in a vast array of applications, including industrial instrumentation, medical devices, telecommunications infrastructure, and consumer electronics. Its ease of use and integrated protection make it a reliable and efficient choice for designers.

Keywords:

LDO Voltage Regulator

Power Supply Rejection Ratio (PSRR)

Low Output Noise

Thermal Shutdown

Application Circuit