How to Use INA226-: Examples, Pinouts, and Specs

The INA226 is a high-side current shunt monitor with an integrated I2C interface, manufactured by ESP (Part ID: 32). It is designed for precise current sensing and power monitoring in a variety of applications. The INA226 can measure both current and voltage, enabling real-time power calculations. Its wide input voltage range and high accuracy make it ideal for power management systems, battery monitoring, and industrial automation.

• Power management in embedded systems
• Battery monitoring in portable devices
• Energy metering in industrial equipment
• Solar power systems
• Data center power monitoring

1. Power Supply: Connect the V+ pin to a 2.7V to 5.5V power source and the GND pin to ground.
2. Current Sensing: Place a shunt resistor between the VIN+ and VIN- pins. The voltage drop across this resistor will be used to calculate the current.
3. I2C Communication: Connect the SCL and SDA pins to the corresponding I2C lines of your microcontroller. Use pull-up resistors (typically 4.7 kΩ) on these lines.
4. I2C Address: Configure the I2C address using the ADDR pin. Refer to the datasheet for address selection options.
5. Alert Function: If needed, connect the ALERT pin to a microcontroller GPIO to monitor programmable thresholds.

• Shunt Resistor Selection: Choose a resistor with a low temperature coefficient and appropriate power rating to ensure accurate measurements.
• Bypass Capacitor: Place a 0.1 µF ceramic capacitor close to the V+ pin to stabilize the power supply.
• I2C Pull-Up Resistors: Ensure proper pull-up resistors are used on the SCL and SDA lines for reliable communication.
• Input Voltage Range: Ensure the voltage at VIN+ and VIN- does not exceed the specified range (0V to 36V).

Below is an example of how to interface the INA226 with an Arduino UNO to measure current and voltage:

#include <Wire.h>

#define INA226_ADDRESS 0x40  // Default I2C address of INA226

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

  // Configure INA226 (example: set calibration register)
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(0x05);  // Calibration register address
  Wire.write(0x10);  // High byte of calibration value
  Wire.write(0x00);  // Low byte of calibration value
  Wire.endTransmission();
}

void loop() {
  // Request voltage data from INA226
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(0x02);  // Bus voltage register address
  Wire.endTransmission();
  Wire.requestFrom(INA226_ADDRESS, 2);  // Request 2 bytes of data

  if (Wire.available() == 2) {
    uint16_t rawVoltage = (Wire.read() << 8) | Wire.read();
    float busVoltage = rawVoltage * 1.25 / 1000;  // Convert to volts
    Serial.print("Bus Voltage: ");
    Serial.print(busVoltage);
    Serial.println(" V");
  }

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

• Replace the calibration value in the setup function with the appropriate value for your shunt resistor.
• The bus voltage conversion factor (1.25 mV per LSB) is based on the INA226 datasheet.

1. No I2C Communication:

   • Ensure the SCL and SDA lines have proper pull-up resistors (4.7 kΩ recommended).
   • Verify the I2C address matches the configuration of the ADDR pin.

2. Incorrect Current Readings:

   • Check the shunt resistor value and ensure it matches the calibration settings in your code.
   • Verify the connections to the VIN+ and VIN- pins.

3. Alert Pin Not Functioning:

   • Ensure the ALERT pin is properly configured in the INA226 registers.
   • Check the microcontroller GPIO pin configuration.

4. High Noise in Measurements:

   • Add a bypass capacitor (0.1 µF) close to the V+ pin.
   • Use shielded cables for long connections to reduce EMI.

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 input voltage range. Ensure the voltage drop across the shunt does not exceed the input range of the INA226.

Q: Can I use the INA226 with a 3.3V microcontroller?
A: Yes, the INA226 operates with a supply voltage of 2.7V to 5.5V and is compatible with 3.3V logic levels.

Q: How do I calculate power using the INA226?
A: Power can be calculated by multiplying the measured current and bus voltage. The INA226 can also perform this calculation internally and provide the result via I2C.