MCP1702T-3302E/CB 3.3V LDO Voltage Regulator: Technical Overview and Application Circuit Design
The MCP1702T-3302E/CB is a popular low-dropout (LDO) voltage regulator from Microchip Technology, renowned for its high efficiency, low quiescent current, and robust performance. Designed to deliver a fixed 3.3V output at up to 250 mA of current, this regulator is an ideal choice for a wide array of applications, particularly in battery-powered and portable devices where power efficiency is paramount.
Technical Overview
The MCP1702 series stands out due to its exceptionally low quiescent current, which is typically just 2 µA during operation and drops to a mere 100 nA in shutdown mode. This feature makes it exceptionally suitable for applications that demand long battery life, such as IoT sensor nodes, wearable electronics, and handheld instruments. The device boasts a very low dropout voltage—typically 178 mV at 100 mA load—allowing it to regulate the output voltage even when the input voltage is very close to 3.3V, thus maximizing the utilization of the available power source.
Furthermore, the regulator incorporates key protection features including overcurrent protection (OCP) and thermal shutdown, ensuring safe operation under fault conditions. Its high power supply rejection ratio (PSRR) of up to 75 dB at 1 kHz makes it effective at filtering out noise from noisy input sources, which is critical for powering sensitive analog and digital circuits.
Application Circuit Design
Implementing the MCP1702T-3302E/CB in a design is straightforward, typically requiring only two external capacitors for stable operation. A basic application circuit is illustrated below.
```
Vin ────╱╲───┐
[C1] │
│ │
├──┴── VIN (Pin 1)
│ MCP1702T-3302
GND ────────┼───── GND (Pin 2)
│
├────── VOUT (Pin 3)
[C2]
│
GND ────────┘
```
Input Capacitor (C1): A 1 µF ceramic capacitor is recommended to be placed between the VIN pin and ground. This capacitor improves the regulator's transient response and stability, especially when the device is located far from the primary power source.
Output Capacitor (C2): A 1 µF ceramic capacitor on the output is sufficient for stability. This value ensures stability and improves load transient response. Larger values can be used for applications with higher transient load demands.
The design process focuses on managing heat dissipation. The maximum power dissipation is given by PD(MAX) = (VIN(MAX) - VOUT) IOUT. For a 5V input and 250 mA load, the power dissipated would be (5V - 3.3V) 0.25A = 0.425W. For the SOT-23 package, careful attention to the PCB layout is necessary; maximizing copper area connected to the GND pin is essential to act as a heatsink and prevent the internal junction temperature from exceeding the maximum rating of 125°C.
In summary, the MCP1702T-3302E/CB is a highly efficient and reliable LDO regulator. Its combination of ultra-low quiescent current, low dropout voltage, and simple design requirements solidify its position as a superior solution for power regulation in space-constrained and power-sensitive 3.3V applications.
Keywords: LDO Voltage Regulator, Low Quiescent Current, 3.3V Output, Battery-Powered Devices, Thermal Shutdown.
