How to Use INA226: Examples, Pinouts, and Specs

The INA226, manufactured by Sensor (Part ID: Volt/Current), is a high-side current shunt monitor with an integrated I2C interface. It is designed to measure voltage, current, and power in a wide range of applications. The device features a precision analog-to-digital converter (ADC) and operates with a supply voltage of 2.7V to 5.5V, making it ideal for battery-powered devices and energy monitoring systems.

• Battery management systems
• Power supply monitoring
• Solar inverters
• Industrial automation
• IoT devices requiring energy consumption tracking

The INA226 is available in a small 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 the ground.
2. Shunt Resistor: Place a precision shunt resistor between the load and ground. Connect the VSHUNT pin to the positive side of the shunt resistor and the GND pin to the negative side.
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: Use the ADDR pin to set the I2C address. This allows multiple INA226 devices to share the same I2C bus.
6. Alert Pin: Optionally, connect the ALERT pin to a microcontroller GPIO to monitor threshold violations.

• Shunt Resistor Selection: Choose a shunt resistor with a low resistance value to minimize power loss but high enough to generate a measurable voltage drop.
• I2C Pull-Up Resistors: Ensure proper pull-up resistors are used on the I2C lines for reliable communication.
• Bypass Capacitor: Place a 0.1µF ceramic capacitor close to the VCC pin to stabilize the power supply.

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

#include <Wire.h>

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

// Register addresses
#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 INA226 (e.g., calibration, averaging, etc.)
  configureINA226();
}

void loop() {
  float busVoltage = readBusVoltage(); // Read bus voltage
  float shuntVoltage = readShuntVoltage(); // Read shunt voltage
  float current = shuntVoltage / 0.01; // Calculate current (assuming 0.01Ω shunt resistor)

  // Print results to the serial monitor
  Serial.print("Bus Voltage: ");
  Serial.print(busVoltage);
  Serial.println(" V");

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

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

void configureINA226() {
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(0x00); // Configuration register
  Wire.write(0x45); // High byte of configuration
  Wire.write(0x27); // Low byte of configuration
  Wire.endTransmission();
}

float readBusVoltage() {
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(REG_BUS_VOLTAGE); // Bus voltage register
  Wire.endTransmission();

  Wire.requestFrom(INA226_ADDRESS, 2);
  uint16_t rawData = (Wire.read() << 8) | Wire.read();

  return rawData * 0.00125; // Convert to volts (1.25mV per LSB)
}

float readShuntVoltage() {
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(REG_SHUNT_VOLTAGE); // Shunt voltage register
  Wire.endTransmission();

  Wire.requestFrom(INA226_ADDRESS, 2);
  uint16_t rawData = (Wire.read() << 8) | Wire.read();

  return rawData * 0.0000025; // Convert to volts (2.5µV per LSB)
}

1. No I2C Communication:

   • Ensure the SCL and SDA lines have proper pull-up resistors (typically 4.7kΩ).
   • Verify the I2C address matches the configuration of the ADDR pin.
   • Check for loose or incorrect wiring.

2. Incorrect Voltage or Current Readings:

   • Verify the shunt resistor value and connections.
   • Ensure the VBUS and VSHUNT pins are connected to the correct points in the circuit.
   • Check the calibration settings in the INA226 configuration.

3. Alert Pin Not Functioning:

   • Confirm the alert threshold is correctly programmed.
   • Ensure the ALERT pin is connected to a microcontroller GPIO or an external pull-up resistor.

• Use an oscilloscope or logic analyzer to monitor the I2C lines for proper communication.
• Double-check all connections and component values in the circuit.
• Refer to the INA226 datasheet for detailed configuration and troubleshooting guidance.