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 in a single device. It is highly versatile, featuring a programmable gain and a wide operating supply voltage range of 2.7V to 5.5V. This makes it ideal for applications such as battery management, power monitoring, and energy optimization in embedded systems.

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

• Supply Voltage (Vcc): 2.7V to 5.5V
• Input Voltage Range: 0V to 36V
• Current Measurement Range: Determined by the shunt resistor
• Communication Interface: I2C (up to 1 MHz)
• Programmable Gain: Configurable for different shunt resistor values
• Operating Temperature Range: -40°C to +125°C
• Accuracy: ±0.1% (typical)
• Power Consumption: 330 µA (typical)

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

1. Power Supply: Connect the VCC 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 VSHUNT+ and VSHUNT- 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 I2C address using the ADDR pin. This allows multiple INA226 devices to share the same I2C bus.
6. Alert Pin (Optional): Configure the ALERT pin for overcurrent, overvoltage, or other threshold-based alerts.

• Ensure the shunt resistor is appropriately rated for the expected current to avoid excessive power dissipation.
• Use decoupling capacitors (e.g., 0.1 µF) near the VCC pin to stabilize the power supply.
• Verify the I2C pull-up resistors are correctly sized for the bus speed and capacitance.
• The INA226 can measure both current and voltage simultaneously, enabling real-time power calculations.

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

#include <Wire.h>

// INA226 I2C address (default is 0x40, but check your configuration)
#define INA226_ADDRESS 0x40

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

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 of configuration (example value)
  Wire.write(0x27);       // LSB of configuration (example value)
  Wire.endTransmission();
}

void loop() {
  float busVoltage = readBusVoltage();
  float shuntVoltage = readShuntVoltage();
  float current = shuntVoltage / 0.1; // Assuming a 0.1 ohm shunt resistor

  Serial.print("Bus Voltage: ");
  Serial.print(busVoltage);
  Serial.println(" V");

  Serial.print("Shunt Voltage: ");
  Serial.print(shuntVoltage);
  Serial.println(" V");

  Serial.print("Current: ");
  Serial.print(current);
  Serial.println(" A");

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

float readBusVoltage() {
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(REG_BUS_VOLTAGE); // Point to the bus voltage register
  Wire.endTransmission();

  Wire.requestFrom(INA226_ADDRESS, 2); // Request 2 bytes
  uint16_t rawData = (Wire.read() << 8) | Wire.read();
  return rawData * 0.00125; // Convert to volts (1.25 mV per bit)
}

float readShuntVoltage() {
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(REG_SHUNT_VOLTAGE); // Point to the shunt voltage register
  Wire.endTransmission();

  Wire.requestFrom(INA226_ADDRESS, 2); // Request 2 bytes
  uint16_t rawData = (Wire.read() << 8) | Wire.read();
  return rawData * 0.0000025; // Convert to volts (2.5 µV per bit)
}

1. No I2C Communication:

   • Ensure the INA226 is powered correctly (VCC and GND connected).
   • Verify the I2C pull-up resistors are present and correctly sized.
   • Check the I2C address configuration (ADDR pin).

2. Incorrect Current or Voltage Readings:

   • Confirm the shunt resistor value matches the expected current range.
   • Verify the connections to the VBUS and VSHUNT pins are correct.
   • Ensure the INA226 configuration register is set appropriately.

3. Alert Pin Not Functioning:

   • Verify the alert threshold settings in the INA226 configuration.
   • Check the connection to the ALERT pin and ensure it is not floating.

• Use an I2C scanner sketch to confirm the INA226 is detected on the I2C bus.
• Double-check all wiring and connections, especially the shunt resistor.
• Use a multimeter to verify the actual voltage and current values for comparison.

By following this documentation, you can effectively integrate the INA226 into your projects for accurate power monitoring and management.