onsemi MC33275ST-5T3G 150 mA Low-Dropout Voltage Regulator: Datasheet, Pinout, and Application Circuits
In the realm of power management for compact electronic devices, low-dropout (LDO) regulators are indispensable for providing stable, clean voltage rails. The onsemi MC33275ST-5T3G stands out as a robust and efficient solution designed for a wide array of applications. This fixed 5V, 150 mA LDO regulator combines low power consumption with high performance, making it an ideal choice for power-sensitive designs.
Datasheet Overview and Key Features
The MC33275 series is part of onsemi's portfolio of linear regulators known for their reliability. The `ST-5T3G` variant comes in a space-saving SOT-223 package, suitable for automated PCB assembly. Key specifications from the datasheet include:
Output Voltage: Fixed at 5.0 V (±2% accuracy).
Maximum Output Current: 150 mA.
Dropout Voltage: Typically 100 mV at 50 mA load, ensuring efficient operation even when the input voltage dips close to the output level.
Low Quiescent Current: Only 6.5 µA typical in off mode and 450 µA during operation, which is crucial for extending battery life in portable devices.
Protection Features: Includes internal current limiting and thermal shutdown for enhanced system reliability.
Low Noise Output: Excellent for powering noise-sensitive analog and RF circuitry.
Pinout Configuration
The MC33275ST-5T3G has a simple three-terminal pinout:
1. Input (VIN): This pin receives the unregulated input voltage, which must be higher than the dropout voltage above 5V. A small input capacitor (typically 1 µF) is recommended for stability.
2. Ground (GND): The common ground reference for the regulator.
3. Output (VOUT): The regulated 5V output. A minimum output capacitor of 1 µF is required for stability, though a larger value (2.2 µF to 10 µF) is often used to improve transient response.
Application Circuits
The primary application for the MC33275ST-5T3G is as a localized power supply for microcontrollers, sensors, and other low-power ICs. Its simplicity makes circuit design straightforward.
1. Basic 5V Regulator Circuit:
The most common application is converting a higher DC voltage (e.g., 7V to 12V from a wall adapter or battery) down to a clean, stable 5V rail. The circuit requires just two capacitors.
Connect a 1 µF ceramic capacitor from the VIN pin to GND.
Connect a 2.2 µF ceramic capacitor from the VOUT pin to GND.
This simple setup provides a stable voltage for your load.
2. Battery-Powered Device Power Management:
In portable electronics powered by a 9V battery or two Li-Ion cells (nominal 7.4V), the MC33275ST-5T3G efficiently provides the necessary 5V rail. Its ultra-low quiescent current minimizes drain when the device is in sleep or standby mode, significantly preserving battery charge.
3. Post-DC/DC Converter Regulation:
Switch-mode DC/DC converters are efficient but can generate significant noise. Placing the MC33275ST-5T3G after a noisy buck converter acts as an effective filter to create a low-noise supply for sensitive components like audio codecs or precision sensors.
The onsemi MC33275ST-5T3G is a highly reliable and efficient LDO voltage regulator, offering an excellent balance of low dropout voltage, ultra-low quiescent current, and robust protection features. Its simplicity, minimal external component requirement, and cost-effectiveness make it a superior choice for designers seeking to create stable power rails in a vast range of low-power applications, from consumer gadgets to industrial controls.
Keywords: Low-Dropout (LDO) Regulator, Low Quiescent Current, Thermal Shutdown, 5V Output, Battery-Powered Devices
