MCP1725-ADJE/MC 3.3V Low-Dropout Linear Regulator Application Note

Introduction

The MCP1725-ADJE/MC is a high-performance, 3.3V low-dropout (LDO) linear regulator from Microchip Technology, designed to deliver a maximum output current of 500 mA. It is engineered for applications requiring a stable, clean voltage supply with minimal noise and high power supply rejection ratio (PSRR). This LDO is particularly suited for powering noise-sensitive components such as microcontrollers, RF modules, and analog sensors in various embedded systems.

Key Features and Benefits

A standout feature of the MCP1725-ADJE/MC is its extremely low dropout voltage, typically 178 mV at 500 mA. This allows the regulator to maintain a stable 3.3V output even when the input voltage dips very close to the output level, enhancing efficiency and extending battery life in portable devices. Furthermore, the device offers a very low quiescent current of 120 µA (typical) at full load, which is crucial for power-conscious applications.

The regulator incorporates advanced over-current and over-temperature protection circuits, safeguarding both the IC and the downstream load from damage under fault conditions. Its high PSRR (typically 70 dB at 1 kHz) ensures excellent rejection of noise and ripple from the input supply, providing a clean and stable output voltage.

Typical Application Circuit

The basic application circuit for the MCP1725-ADJE/MC is straightforward, requiring only two external capacitors for operation. A 1 µF ceramic capacitor on the input (CIN) and a 10 µF ceramic capacitor on the output (COUT) are sufficient for stability. The enable (EN) pin allows for external logic control to turn the regulator on or off, facilitating power management sequences and further reducing system-wide power consumption when the device is shut down.

Design Considerations

1. Thermal Management: When operating at high load currents or with a large input-to-output voltage differential, power dissipation (PD = (VIN - VOUT) IOUT) becomes critical. Proper PCB layout, including the use of thermal vias and adequate copper pour connected to the tab of the DFN package, is essential to maximize heat dissipation and prevent the internal thermal shutdown from activating.

2. Stability: While stable with ceramic capacitors, it is imperative to use capacitors with a low Effective Series Resistance (ESR). The recommended 10 µF COUT capacitor ensures stability across the entire operating temperature and load current range.

3. Input Voltage Range: The device operates with an input voltage range from 2.3V to 5.5V. The input must always remain higher than VOUT + VDROPOUT for regulated operation.

Conclusion

The MCP1725-ADJE/MC is a robust and efficient solution for providing a stable 3.3V power rail. Its combination of low dropout voltage, low quiescent current, high PSRR, and integrated protection features makes it an ideal choice for a wide array of applications, including battery-powered equipment, consumer electronics, and industrial control systems.

ICGOODFIND: A reliable and efficient LDO choice for noise-sensitive 3.3V applications, offering excellent transient response and protection features in a small package.

Keywords: Low-Dropout (LDO) Regulator, Quiescent Current, Power Supply Rejection Ratio (PSRR), Thermal Management, Dropout Voltage.