How to Use INA226: Examples, Pinouts, and Specs

The INA226, manufactured by Sensor, is a high-side current shunt monitor with an integrated I2C interface. It is designed to measure voltage, current, and power with high precision, thanks to its built-in analog-to-digital converter (ADC). The INA226 is highly versatile and operates over a wide voltage range, making it ideal for applications such as battery management, power monitoring, and energy-efficient system design.

• Battery management systems
• Power supply monitoring
• Energy metering in IoT devices
• Industrial automation and control
• Solar power systems

1. Power Supply: Connect the V+ pin to a 2.7V to 5.5V power source and GND to ground.
2. Shunt Resistor: Place a shunt resistor between the SHUNT+ and SHUNT- pins to measure current. The value of the resistor depends on the expected current range.
3. Voltage Measurement: Connect the VBUS pin to the voltage source you want to monitor.
4. I2C Communication: Connect the SCL and SDA pins to the corresponding I2C lines of your microcontroller. Use pull-up resistors (typically 4.7kΩ) on these lines.
5. Address Configuration: Set the A0 and A1 pins to configure the I2C address. These pins can be connected to V+ or GND to select one of 16 possible addresses.
6. Alert/Ready Pin: Optionally, use the ALERT/RDY pin for interrupt-driven alerts or to indicate data readiness.

• Shunt Resistor Selection: Choose a low-value, high-precision resistor to minimize power loss and ensure accurate current measurements.
• I2C Pull-Up Resistors: Ensure proper pull-up resistors are used on the I2C lines to maintain signal integrity.
• Bypass Capacitor: Place a 0.1µF ceramic capacitor close to the V+ pin to filter noise.
• Address Conflicts: If multiple INA226 devices are used on the same I2C bus, ensure each has a unique address by configuring the A0 and A1 pins.

#include <Wire.h>

// INA226 I2C address (default: A0 = GND, A1 = GND)
#define INA226_ADDRESS 0x40

// Register addresses
#define CONFIG_REGISTER 0x00
#define BUS_VOLTAGE_REGISTER 0x02
#define CURRENT_REGISTER 0x04

void setup() {
  Wire.begin(); // Initialize I2C communication
  Serial.begin(9600); // Initialize serial communication for debugging

  // Configure INA226 (example configuration)
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(CONFIG_REGISTER); // Point to configuration register
  Wire.write(0x45); // MSB: Set averaging, bus voltage conversion time
  Wire.write(0x27); // LSB: Set shunt voltage conversion time
  Wire.endTransmission();
}

void loop() {
  // Read bus voltage
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(BUS_VOLTAGE_REGISTER); // Point to bus voltage register
  Wire.endTransmission();
  
  Wire.requestFrom(INA226_ADDRESS, 2); // Request 2 bytes
  if (Wire.available() == 2) {
    uint16_t rawVoltage = (Wire.read() << 8) | Wire.read();
    float busVoltage = rawVoltage * 0.00125; // Convert to volts (1.25mV/LSB)
    Serial.print("Bus Voltage: ");
    Serial.print(busVoltage);
    Serial.println(" V");
  }

  delay(1000); // Wait 1 second before next reading
}

1. No I2C Communication:

   • Ensure the INA226 is powered correctly (V+ and GND connected).
   • Verify pull-up resistors are present on the SCL and SDA lines.
   • Check the I2C address configuration (A0 and A1 pins).

2. Incorrect Current or Voltage Readings:

   • Verify the shunt resistor value and connections.
   • Ensure the VBUS pin is connected to the correct voltage source.
   • Check for noise or interference on the measurement lines.

3. ALERT/RDY Pin Not Functioning:

   • Confirm the ALERT/RDY pin is configured correctly in the INA226 registers.
   • Ensure the microcontroller's interrupt pin is properly connected.

• Q: Can the INA226 measure negative currents?
  A: No, the INA226 is designed for high-side current sensing and measures only positive currents.

• Q: What is the maximum current the INA226 can measure?
  A: The maximum current depends on the shunt resistor value and the voltage drop across it. Ensure the voltage drop does not exceed the ADC's input range.

• Q: Can I use the INA226 with a 3.3V microcontroller?
  A: Yes, the INA226 operates with a supply voltage as low as 2.7V, making it compatible with 3.3V systems.