How to Use S8V9F5: Examples, Pinouts, and Specs

The S8V9F5 is a high-performance DC-DC step-up/step-down voltage regulator manufactured by Pololu. This versatile component is designed to efficiently regulate voltage in a wide range of electronic applications. It can step up or step down the input voltage to provide a stable output, making it ideal for systems where the input voltage may vary above or below the desired output voltage.

• Battery-powered devices where the input voltage fluctuates (e.g., lithium-ion batteries)
• Robotics and embedded systems requiring stable voltage
• Portable electronics and IoT devices
• Powering microcontrollers, sensors, and communication modules
• Applications requiring protection against overcurrent and thermal overload

• Input Voltage Range: 2.8 V to 32 V
• Output Voltage: Fixed at 5 V
• Maximum Output Current: Up to 2 A (depending on input voltage)
• Efficiency: Up to 90% (varies with input/output conditions)
• Quiescent Current: Approximately 1 mA
• Built-in Protections:
  • Overcurrent protection
  • Thermal shutdown
• Operating Temperature Range: -40°C to +85°C
• Dimensions: 12.7 mm × 12.7 mm × 3.8 mm
• Weight: 1.2 g

The S8V9F5 module has six pins. Below is the pinout and description:

1. Power Connections:

   • Connect the VIN pin to the positive terminal of your power source (e.g., battery or DC supply).
   • Connect the GND pins to the negative terminal of your power source.
   • Ensure the input voltage is within the range of 2.8 V to 32 V.

2. Output Connections:

   • Connect the VOUT pin to your load. The output voltage is fixed at 5 V.

3. Enable/Disable Functionality:

   • To enable the regulator, leave the SHDN pin floating or drive it high.
   • To disable the regulator, drive the SHDN pin low.

4. Power Good Indicator:

   • Use the PG pin to monitor the output voltage. A high signal indicates that the output voltage is stable.

• Input Capacitor: Place a low-ESR capacitor (e.g., 10 µF) close to the VIN pin to reduce input voltage ripple.
• Output Capacitor: Use a low-ESR capacitor (e.g., 10 µF) near the VOUT pin to stabilize the output voltage.
• Thermal Management: Ensure adequate ventilation or heat dissipation if operating near the maximum current limit.
• Wiring: Keep the input and output wires as short as possible to minimize noise and voltage drops.
• Load Current: The maximum output current depends on the input voltage. Refer to the efficiency and current graphs in the Pololu datasheet for detailed performance data.

The S8V9F5 can be used to power an Arduino UNO from a variable power source. Below is an example circuit and Arduino code to monitor the PG pin.

1. Connect the VIN pin to a 9 V battery.
2. Connect the GND pin to the battery's negative terminal and the Arduino's GND pin.
3. Connect the VOUT pin to the Arduino's 5 V pin.
4. Connect the PG pin to Arduino digital pin 2.

// Define the pin connected to the PG (Power Good) signal
const int pgPin = 2;

void setup() {
  // Initialize serial communication for debugging
  Serial.begin(9600);

  // Set the PG pin as an input
  pinMode(pgPin, INPUT);

  // Print a startup message
  Serial.println("S8V9F5 Power Good Monitoring Started");
}

void loop() {
  // Read the state of the PG pin
  int pgState = digitalRead(pgPin);

  // Check if the output voltage is stable
  if (pgState == HIGH) {
    Serial.println("Output voltage is stable (Power Good).");
  } else {
    Serial.println("Output voltage is not stable!");
  }

  // Wait for 1 second before checking again
  delay(1000);
}

1. No Output Voltage:

   • Ensure the SHDN pin is not driven low. Leave it floating or drive it high.
   • Verify that the input voltage is within the specified range (2.8 V to 32 V).
   • Check for loose or incorrect connections.

2. Output Voltage is Unstable:

   • Add low-ESR capacitors to the input and output pins as recommended.
   • Ensure the load does not exceed the maximum current rating.

3. Component Overheating:

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

4. PG Pin Always Low:

   • Verify that the output voltage is within the expected range.
   • Check the wiring and ensure the load is properly connected.

Q1: Can the S8V9F5 output a voltage other than 5 V?
No, the S8V9F5 is a fixed 5 V regulator. For adjustable output voltages, consider other Pololu regulators.

Q2: What happens if the input voltage exceeds 32 V?
The regulator may be damaged. Always ensure the input voltage stays within the specified range.

Q3: Can I use the S8V9F5 with a rechargeable battery?
Yes, the S8V9F5 is ideal for battery-powered applications, as it can handle varying input voltages.

Q4: Is reverse polarity protection included?
No, the S8V9F5 does not have built-in reverse polarity protection. Use an external diode to protect the circuit.

Q5: How do I calculate efficiency for my application?
Refer to the efficiency graphs in the Pololu datasheet. Efficiency depends on the input voltage, output voltage, and load current.