How to Use INA 226: Examples, Pinouts, and Specs

The INA226 is a precision current shunt monitor designed to measure the voltage across a shunt resistor, enabling accurate current measurement. It features a high common-mode voltage range (up to 36V) and integrates a 16-bit ADC for precise measurements. The INA226 communicates via an I2C interface, making it easy to integrate into digital systems for power monitoring and energy management.

• Power monitoring in embedded systems
• Battery management systems
• DC-DC converter efficiency analysis
• Industrial automation and control
• Solar power systems and energy metering

1. Power Supply: Connect the V_CC pin to a 3.3V or 5V power source and the GND pin to the ground.
2. Shunt Resistor: Place a precision shunt resistor in series with the load whose current you want to measure. Connect the V_IN+ and V_IN- pins across the shunt resistor.
3. 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.
4. Address Configuration: Set the I2C address by connecting the ADDR pin to GND, V_CC, or leaving it floating (refer to the datasheet for address mapping).
5. Alert Pin (Optional): Use the ALERT pin to monitor programmable thresholds for current, voltage, or power.

• Use a low-resistance, high-precision shunt resistor to minimize power loss and ensure accurate measurements.
• Keep the traces between the shunt resistor and the INA226 as short as possible to reduce noise.
• Ensure proper decoupling by placing a 0.1µF capacitor close to the V_CC pin.
• Avoid exceeding the common-mode voltage range (0V to 36V) to prevent damage to the device.

The following example demonstrates how to configure and read data from the INA226 using an Arduino UNO.

#include <Wire.h>

// INA226 I2C address (default: 0x40)
#define INA226_ADDRESS 0x40

// Register addresses
#define CONFIG_REGISTER 0x00
#define SHUNT_VOLTAGE_REGISTER 0x01
#define BUS_VOLTAGE_REGISTER 0x02

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

  // Configure the INA226
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(CONFIG_REGISTER); // 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, mode
  Wire.endTransmission();
}

void loop() {
  int16_t shuntVoltage = readRegister(SHUNT_VOLTAGE_REGISTER);
  int16_t busVoltage = readRegister(BUS_VOLTAGE_REGISTER);

  // Convert raw values to meaningful units
  float shuntVoltage_mV = shuntVoltage * 0.0025; // 2.5µV per LSB
  float busVoltage_V = busVoltage * 0.00125; // 1.25mV per LSB

  // Print the results
  Serial.print("Shunt Voltage (mV): ");
  Serial.println(shuntVoltage_mV);
  Serial.print("Bus Voltage (V): ");
  Serial.println(busVoltage_V);

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

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
  while (Wire.available() < 2); // Wait for data

  int16_t value = (Wire.read() << 8) | Wire.read(); // Combine MSB and LSB
  return value;
}

1. No I2C Communication:

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

2. Incorrect Current or Voltage Readings:

   • Verify the shunt resistor value and ensure it matches the calculations in your code.
   • Minimize noise by keeping the shunt resistor traces short and using proper decoupling capacitors.

3. Device Not Responding:

   • Confirm the power supply voltage is within the specified range (2.7V to 5.5V).
   • Check for shorts or incorrect connections on the PCB.

Q: Can the INA226 measure negative currents?
A: Yes, the INA226 can measure bidirectional currents if configured appropriately. Refer to the datasheet for details on setting the calibration register.

Q: What is the maximum shunt voltage the INA226 can measure?
A: The INA226 can measure a maximum shunt voltage of ±81.92mV.

Q: How do I calculate the current from the shunt voltage?
A: Use Ohm's Law: Current (A) = Shunt Voltage (V) / Shunt Resistance (Ω). Ensure the shunt resistor value is known and precise.

Q: Can I use the INA226 with a 5V microcontroller?
A: Yes, the INA226 supports a supply voltage range of 2.7V to 5.5V, making it compatible with 5V systems.