How to Use SX1308: Examples, Pinouts, and Specs

The SX1308 is a highly integrated step-up boost converter designed by Shenzhen Suosemi Tech. It is widely used in applications requiring efficient voltage step-up from a lower input voltage to a higher output voltage. The SX1308 is compact, cost-effective, and highly efficient, making it suitable for powering devices in battery-operated systems, portable electronics, and IoT applications.

• Powering microcontrollers and sensors in IoT devices
• Boosting voltage for LED strips and displays
• Battery-powered devices requiring higher operating voltages
• Portable electronics such as handheld gadgets and wearables

• Input Voltage Range: 2V to 24V
• Output Voltage Range: 2V to 28V
• Switching Frequency: 1.2 MHz
• Maximum Output Current: 2A (depending on input voltage and load conditions)
• Efficiency: Up to 95%
• Quiescent Current: < 120 µA
• Operating Temperature Range: -40°C to +85°C
• Package Type: SOT-23-6

The SX1308 is typically available in a 6-pin SOT-23 package. Below is the pinout and description:

1. Input and Output Capacitors:

   • Place a low-ESR capacitor (e.g., 10 µF ceramic) close to the VIN pin to stabilize the input voltage.
   • Use a similar capacitor at the VOUT pin to smooth the output voltage.

2. Inductor Selection:

   • Choose an inductor with a suitable current rating (e.g., 2A or higher) and an inductance value between 4.7 µH and 22 µH, depending on the desired output voltage and current.

3. Feedback Resistor Divider:

   • Use two resistors to set the output voltage. The formula is: [ V_{OUT} = V_{REF} \times \left(1 + \frac{R1}{R2}\right) ] where ( V_{REF} ) is typically 0.6V.

4. Enable Pin:

   • Connect the EN pin to VIN or a microcontroller GPIO pin to control the converter's operation.

5. Diode Selection:

   • Use a Schottky diode with a low forward voltage drop and a current rating higher than the maximum output current.

• Ensure proper PCB layout to minimize noise and improve efficiency. Place components as close to the IC as possible.
• Avoid exceeding the maximum input voltage (24V) or output voltage (28V) to prevent damage.
• Use a heat sink or proper ventilation if operating at high currents to manage thermal dissipation.
• For applications requiring precise output voltage, use resistors with a low tolerance (e.g., 1%).

The SX1308 can be used to power an Arduino UNO from a lower voltage source, such as a 3.7V Li-ion battery. Below is an example circuit and Arduino code to enable/disable the SX1308 using a GPIO pin.

• Connect the battery's positive terminal to the VIN pin of the SX1308.
• Connect the VOUT pin to the Arduino's 5V pin.
• Connect the EN pin to an Arduino GPIO pin (e.g., D7) for control.

// Define the pin connected to the SX1308 EN pin
const int enablePin = 7;

void setup() {
  // Set the enable pin as an output
  pinMode(enablePin, OUTPUT);

  // Enable the SX1308 by setting the pin HIGH
  digitalWrite(enablePin, HIGH);
}

void loop() {
  // Example: Toggle the SX1308 on and off every 5 seconds
  digitalWrite(enablePin, HIGH); // Enable the SX1308
  delay(5000);                   // Wait for 5 seconds
  digitalWrite(enablePin, LOW);  // Disable the SX1308
  delay(5000);                   // Wait for 5 seconds
}

1. No Output Voltage:

   • Check the input voltage and ensure it is within the specified range (2V to 24V).
   • Verify that the EN pin is pulled high to enable the converter.
   • Inspect the feedback resistor divider for correct values and connections.

2. Output Voltage is Unstable:

   • Ensure proper placement of input and output capacitors close to the IC.
   • Check the inductor value and ensure it is appropriate for the load conditions.
   • Verify that the load current does not exceed the maximum rating.

3. Excessive Heat:

   • Ensure the input and output voltages are within the specified range.
   • Use an inductor and diode with sufficient current ratings.
   • Improve PCB layout to enhance heat dissipation.

4. Low Efficiency:

   • Use low-ESR capacitors and a Schottky diode to minimize losses.
   • Optimize the feedback resistor values for the desired output voltage.

Q1: Can the SX1308 be used to power a 12V LED strip from a 5V source?
A1: Yes, the SX1308 can step up a 5V input to 12V, provided the current requirements of the LED strip do not exceed the SX1308's maximum output current.

Q2: What happens if the input voltage drops below 2V?
A2: The SX1308 will stop operating, and the output voltage will drop. Ensure the input voltage remains within the specified range.

Q3: Can I use the SX1308 for audio applications?
A3: While the SX1308 is not specifically designed for audio, it can be used in low-power audio circuits. However, ensure proper filtering to minimize noise.

Q4: How do I calculate the inductor value for my application?
A4: Refer to the SX1308 datasheet for detailed formulas and guidelines based on your input voltage, output voltage, and load current requirements.