How to Use cn3722: Examples, Pinouts, and Specs

The CN3722 is a high-efficiency, step-down (buck) voltage regulator designed for low-power applications. It supports a wide input voltage range and provides an adjustable output voltage, making it versatile for various electronic designs. The CN3722 is equipped with built-in protection features, including overcurrent protection and thermal shutdown, ensuring reliable operation in demanding environments. Its compact design and high efficiency make it ideal for battery-powered devices, portable electronics, and other compact systems requiring efficient power regulation.

• Battery-powered devices
• Portable electronics
• IoT devices
• Low-power embedded systems
• LED drivers

The CN3722 is typically available in an 8-pin SOP package. Below is the pinout and description:

1. Input Voltage: Connect a DC voltage source (4.5V to 28V) to the VIN pin. Ensure the input voltage is within the specified range.
2. Output Voltage Adjustment: Use a resistor divider network connected to the FB pin to set the desired output voltage. The formula for the output voltage is: [ V_{OUT} = V_{REF} \times \left(1 + \frac{R1}{R2}\right) ] where ( V_{REF} ) is typically 0.8V.
3. Inductor Selection: Choose an inductor with a suitable current rating (greater than the output current) and low DC resistance for optimal efficiency.
4. Capacitor Selection: Use low ESR capacitors for input and output filtering to minimize voltage ripple.
5. Enable Pin: Pull the EN pin high to enable the regulator. Pull it low to disable the output.
6. Compensation: Connect a capacitor and resistor to the COMP pin to stabilize the feedback loop.

• Ensure proper heat dissipation by using a PCB with adequate thermal management (e.g., thermal vias, copper planes).
• Avoid exceeding the maximum input voltage or output current ratings to prevent damage.
• Use proper decoupling capacitors close to the VIN and VCC pins to reduce noise.

The CN3722 can be used to power an Arduino UNO by stepping down a higher voltage (e.g., 12V) to 5V. Below is an example circuit and Arduino code:

• Connect a 12V DC power supply to the VIN pin of the CN3722.
• Set the output voltage to 5V using a resistor divider on the FB pin.
• Connect the 5V output to the Arduino UNO's 5V pin.

// Example code to blink an LED using Arduino UNO powered by CN3722
// Ensure the CN3722 output is set to 5V before connecting to the Arduino.

const int ledPin = 13; // Built-in LED pin on Arduino UNO

void setup() {
  pinMode(ledPin, OUTPUT); // Set LED pin as output
}

void loop() {
  digitalWrite(ledPin, HIGH); // Turn the LED on
  delay(1000);                // Wait for 1 second
  digitalWrite(ledPin, LOW);  // Turn the LED off
  delay(1000);                // Wait for 1 second
}

1. No Output Voltage

   • Cause: EN pin is not pulled high.
   • Solution: Ensure the EN pin is connected to a high logic level (e.g., VIN).

2. Excessive Heat

   • Cause: Overloading the regulator or insufficient heat dissipation.
   • Solution: Reduce the load current or improve PCB thermal design.

3. Output Voltage Instability

   • Cause: Incorrect compensation network or poor capacitor selection.
   • Solution: Verify the compensation network and use low ESR capacitors.

4. High Output Ripple

   • Cause: Insufficient input/output filtering.
   • Solution: Add or replace capacitors with higher capacitance and lower ESR.

Q: Can the CN3722 be used for 3.3V output?
A: Yes, the CN3722 can be configured for 3.3V output by selecting appropriate resistor values for the feedback network.

Q: What is the maximum load current?
A: The CN3722 supports a maximum load current of 2A.

Q: Is the CN3722 suitable for battery charging applications?
A: While the CN3722 is primarily a step-down regulator, it can be used in battery charging circuits with proper design considerations.

Q: How do I calculate the inductor value?
A: The inductor value depends on the input voltage, output voltage, switching frequency, and load current. Refer to the CN3722 datasheet for detailed calculations.

This concludes the CN3722 documentation. For further details, consult the official datasheet or application notes.