How to Use 5V Step-Up Voltage Regulator U3V40F5: Examples, Pinouts, and Specs

The 5V Step-Up Voltage Regulator U3V40F5 by Pololu is a DC-DC boost converter designed to increase a lower input voltage to a stable 5V output. This compact and efficient regulator is ideal for powering devices that require a consistent 5V supply, even when the input voltage is significantly lower. It is particularly useful in battery-powered applications, where the input voltage may drop as the battery discharges.

• Powering 5V microcontrollers (e.g., Arduino, Raspberry Pi) from lower voltage sources.
• Boosting voltage from single-cell lithium-ion batteries (3.7V nominal).
• Providing a stable 5V output for sensors, communication modules, or other peripherals.
• Applications in robotics, portable electronics, and IoT devices.

• Input Voltage Range: 2.9V to 5.5V
• Output Voltage: Fixed 5V
• Maximum Output Current: Up to 4A (depending on input voltage)
• Efficiency: Up to 90% (varies with input voltage and load)
• Quiescent Current: Approximately 1 mA
• Dimensions: 0.9" × 0.6" × 0.1" (22.9 mm × 15.2 mm × 3 mm)
• Weight: 1.2 g

The U3V40F5 regulator has six pins, as detailed in the table below:

1. Connect the Input Voltage:
   • Attach the positive terminal of your power source (e.g., battery) to the VIN pin.
   • Connect the negative terminal of your power source to the GND pin.
2. Connect the Output Voltage:
   • Connect the VOUT pin to the positive terminal of your load (e.g., microcontroller, sensor).
   • Connect the GND pin to the ground of your load.
3. Optional Connections:
   • Use the SHDN pin to enable or disable the regulator. Leave it unconnected or pull it high to enable the regulator. Pull it low to disable it.
   • The PG pin can be used to monitor the output voltage. It will output 5V when the output is stable.

• Ensure the input voltage is within the specified range (2.9V to 5.5V). Exceeding this range may damage the regulator.
• The maximum output current depends on the input voltage. For example:
  • At 3.3V input, the regulator can supply up to 2.5A.
  • At 5V input, it can supply up to 4A.
• Use capacitors on the input and output for improved stability:
  • A 10 µF capacitor on the input.
  • A 10 µF capacitor on the output.
• Avoid shorting the output pins, as this may damage the regulator.
• Ensure proper heat dissipation if operating at high currents for extended periods.

The U3V40F5 can be used to power an Arduino UNO from a 3.7V lithium-ion battery. Below is an example circuit and Arduino code to monitor the PG pin.

• Connect the battery's positive terminal to VIN and negative terminal to GND.
• Connect VOUT to the Arduino's 5V pin and GND to the Arduino's GND pin.
• Connect the PG pin to a digital input pin on the Arduino (e.g., pin 2).

// Example code to monitor the Power Good (PG) pin of the U3V40F5 regulator
const int pgPin = 2;  // PG pin connected to Arduino digital pin 2
const int ledPin = 13; // Onboard LED to indicate power status

void setup() {
  pinMode(pgPin, INPUT);  // Set PG pin as input
  pinMode(ledPin, OUTPUT); // Set LED pin as output
  Serial.begin(9600); // Initialize serial communication
}

void loop() {
  int pgStatus = digitalRead(pgPin); // Read the PG pin status

  if (pgStatus == HIGH) {
    // PG pin is HIGH, output voltage is stable
    digitalWrite(ledPin, HIGH); // Turn on the LED
    Serial.println("Power Good: Output voltage is stable.");
  } else {
    // PG pin is LOW, output voltage is not stable
    digitalWrite(ledPin, LOW); // Turn off the LED
    Serial.println("Warning: Output voltage is unstable!");
  }

  delay(500); // Wait for 500ms before checking again
}

1. No Output Voltage:

   • Ensure the input voltage is within the specified range (2.9V to 5.5V).
   • Verify that the SHDN pin is not pulled low. Leave it unconnected or pull it high to enable the regulator.
   • Check all connections for loose wires or poor solder joints.

2. Output Voltage is Unstable:

   • Add capacitors (10 µF) to the input and output pins for improved stability.
   • Ensure the load does not exceed the maximum current rating for the given input voltage.

3. Regulator Overheating:

   • Reduce the load current if operating near the maximum current limit.
   • Improve ventilation or add a heatsink to dissipate heat.

4. PG Pin Not Working:

   • Ensure the PG pin is connected to a pull-up resistor or a microcontroller input pin.
   • Verify that the output voltage is within the stable range (approximately 5V).

Q: Can I use this regulator with a 1.5V AA battery?
A: No, the input voltage must be at least 2.9V. A single 1.5V AA battery is insufficient. You can use two or more AA batteries in series to meet the input voltage requirement.

Q: What happens if the input voltage exceeds 5.5V?
A: Exceeding the maximum input voltage may permanently damage the regulator. Always ensure the input voltage stays within the specified range.

Q: Can I use this regulator to power a Raspberry Pi?
A: Yes, but ensure the input voltage and current requirements of the Raspberry Pi are met. For high-power models, the input voltage should be closer to 5V to provide sufficient current.

This concludes the documentation for the 5V Step-Up Voltage Regulator U3V40F5.