How to Use INA226: Examples, Pinouts, and Specs

The INA226 is a high-side current shunt monitor with an integrated I2C interface, designed to measure voltage, current, and power with high precision. It is widely used in applications requiring accurate power monitoring, such as battery management systems, server power monitoring, and industrial automation. The device supports a wide input voltage range and offers programmable calibration for enhanced flexibility.

• Battery management systems
• Power supply monitoring
• Energy metering
• Industrial and automotive systems
• Server and data center power management

• Supply Voltage (V_CC): 2.7V to 5.5V
• Input Voltage Range: 0V to 36V
• Current Measurement Range: Determined by external shunt resistor
• Communication Interface: I2C (up to 1 MHz)
• Accuracy: ±0.1% (typical)
• Operating Temperature Range: -40°C to +125°C
• Power Consumption: 330 µA (typical)
• Package: 10-pin VSSOP

1. Power Supply: Connect the V_CC pin to a 3.3V or 5V power supply and the GND pin to the ground.
2. Shunt Resistor: Place a precision shunt resistor between the V_IN+ and V_IN- pins to measure current. The value of the resistor determines the measurable current range.
3. I2C Interface: 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. Address Configuration: Use the ADDR pin to set the I2C address of the INA226. This allows multiple devices to share the same I2C bus.
5. Alert Pin (Optional): Connect the ALERT pin to a microcontroller GPIO if you want to use the alert functionality for overcurrent or voltage thresholds.

• Ensure the shunt resistor is of high precision and low temperature coefficient for accurate measurements.
• The INA226 requires proper calibration for accurate current and power readings. Use the calibration register to set the correct scaling factor based on the shunt resistor value.
• Avoid exceeding the maximum input voltage (36V) to prevent damage to the device.

Below is an example of how to interface 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 differently)
#define INA226_ADDRESS 0x40

// INA226 register addresses
#define REG_CALIBRATION 0x05
#define REG_CURRENT     0x04
#define REG_BUS_VOLTAGE 0x02

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

  // Configure INA226 calibration register
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(REG_CALIBRATION); // Point to calibration register
  Wire.write(0x10); // Write high byte of calibration value
  Wire.write(0x00); // Write low byte of calibration value
  Wire.endTransmission();

  Serial.println("INA226 Initialized");
}

void loop() {
  float current = readCurrent(); // Read current in Amperes
  float voltage = readBusVoltage(); // Read bus voltage in Volts

  Serial.print("Current: ");
  Serial.print(current, 3); // Print current with 3 decimal places
  Serial.println(" A");

  Serial.print("Voltage: ");
  Serial.print(voltage, 3); // Print voltage with 3 decimal places
  Serial.println(" V");

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

float readCurrent() {
  int16_t rawCurrent = readRegister(REG_CURRENT); // Read raw current value
  return rawCurrent * 0.001; // Convert to Amperes (adjust scaling as needed)
}

float readBusVoltage() {
  int16_t rawVoltage = readRegister(REG_BUS_VOLTAGE); // Read raw voltage value
  return rawVoltage * 0.00125; // Convert to Volts (1.25 mV per LSB)
}

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 from the register
  int16_t value = (Wire.read() << 8) | Wire.read(); // Combine high and low bytes
  return value;
}

• Replace the calibration value in the code (0x1000) with the appropriate value based on your shunt resistor.
• Ensure the I2C pull-up resistors are properly connected to avoid communication issues.

1. No I2C Communication:

   • Ensure the SCL and SDA lines are connected correctly and have pull-up resistors.
   • Verify the I2C address of the INA226 matches the address in your code.

2. Incorrect Current or Voltage Readings:

   • Check the calibration register value. It must match the shunt resistor's specifications.
   • Verify the shunt resistor's connections and ensure it is of high precision.

3. Alert Pin Not Functioning:

   • Ensure the alert functionality is configured correctly in the INA226 registers.
   • Check the microcontroller GPIO pin configuration.

• Use an I2C scanner sketch to confirm the INA226 is detected on the I2C bus.
• Double-check all connections, especially the shunt resistor and power supply.
• Refer to the INA226 datasheet for detailed register descriptions and configuration options.