How to Use INA226: Examples, Pinouts, and Specs

The INA226 is a high-side current shunt monitor with an integrated I2C interface. It is designed to measure the voltage across a shunt resistor, enabling precise current flow measurements. Additionally, the INA226 can calculate power consumption by combining current and voltage measurements, making it a versatile tool for power monitoring applications.

• Battery management systems
• Power supply monitoring
• Energy metering in industrial and consumer electronics
• Solar power systems
• Server and data center power monitoring

The INA226 offers a range of features and specifications that make it suitable for a variety of applications. Below are the key technical details:

The INA226 is available in a small 10-pin VSSOP package. Below is the pinout and description:

The INA226 is straightforward to use in a circuit. Below are the steps and considerations for integrating it into your design.

1. Power Supply: Connect the V_CC pin to a 2.7V to 5.5V power source and the GND pin to ground.
2. Shunt Resistor: Place a shunt resistor between the high-side power source and the load. Connect the V_IN+ and V_IN- pins across the shunt resistor.
3. I2C Interface: Connect the SCL and SDA pins to the corresponding I2C lines of your microcontroller. Use pull-up resistors (typically 4.7kΩ) on these lines.
4. I2C Address: Configure the I2C address using the ADDR pin. This allows multiple INA226 devices to share the same I2C bus.
5. Alert Pin (Optional): Use the ALERT pin to monitor programmable thresholds for current, voltage, or power.

• Shunt Resistor Selection: Choose a shunt resistor with a low resistance value to minimize power loss, but ensure it provides a measurable voltage drop within the INA226's input range (±81.92mV).
• 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_CC pin for power supply decoupling.

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

#include <Wire.h>

// INA226 I2C address (default is 0x40, adjust if ADDR pin is configured)
#define INA226_ADDRESS 0x40

// INA226 register addresses
#define REG_CONFIG 0x00
#define REG_SHUNT_VOLTAGE 0x01
#define REG_BUS_VOLTAGE 0x02

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

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

void loop() {
  float shuntVoltage = readShuntVoltage();
  float busVoltage = readBusVoltage();

  // Calculate current (I = V / R, where R is the shunt resistor value)
  float shuntResistor = 0.1; // Example: 0.1 ohm
  float current = shuntVoltage / shuntResistor;

  // Print the results
  Serial.print("Shunt Voltage (mV): ");
  Serial.println(shuntVoltage * 1000); // Convert to mV
  Serial.print("Bus Voltage (V): ");
  Serial.println(busVoltage);
  Serial.print("Current (A): ");
  Serial.println(current);

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

float readShuntVoltage() {
  return readRegister(REG_SHUNT_VOLTAGE) * 2.5e-6; // Convert to volts
}

float readBusVoltage() {
  return readRegister(REG_BUS_VOLTAGE) * 1.25e-3; // Convert to volts
}

int16_t readRegister(uint8_t reg) {
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(reg); // Point to the desired register
  Wire.endTransmission();

  Wire.requestFrom(INA226_ADDRESS, 2); // Request 2 bytes
  int16_t value = (Wire.read() << 8) | Wire.read(); // Combine MSB and LSB
  return value;
}

• Replace the shuntResistor value with the actual resistance of your shunt resistor.
• Ensure the I2C address matches your INA226 configuration.

1. No I2C Communication:

   • Ensure the correct I2C address is used.
   • Verify pull-up resistors are present on the SDA and SCL lines.
   • Check for proper wiring and connections.

2. Incorrect Current or Voltage Readings:

   • Verify the shunt resistor value and ensure it is within the INA226's input range.
   • Check for noise or instability in the power supply.

3. Alert Pin Not Functioning:

   • Ensure the ALERT pin is properly configured in the INA226 registers.
   • Verify the threshold values are set correctly.

• Use an I2C scanner sketch to confirm the INA226 is detected on the I2C bus.
• Double-check all connections, especially the shunt resistor and I2C lines.
• Use an oscilloscope or logic analyzer to debug I2C communication if needed.

By following this documentation, you should be able to successfully integrate and use the INA226 in your projects.