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 wide range of applications. It features a precision 16-bit analog-to-digital converter (ADC) for accurate measurements and operates with a supply voltage range of 2.7V to 5.5V, making it ideal for battery-powered devices. The INA226 is commonly used in power management systems, battery monitoring, and industrial equipment.

• Battery management systems
• Power supply monitoring
• Energy metering
• Industrial automation
• IoT devices and embedded systems

1. Power Supply: Connect the V+ pin to a 2.7V to 5.5V power source and the GND pin to ground.
2. Shunt Resistor: Place a precision shunt resistor between the load and ground. Connect the VIN+ and VIN- pins across the shunt resistor to measure the voltage drop.
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 the SCL and SDA lines.
4. Address Configuration: Use the A0 and A1 pins to set the I2C address of the INA226. These pins can be connected to V+ or GND to select one of 16 possible addresses.
5. Bypass Capacitor: Place a 0.1µF ceramic capacitor close to the V+ pin for power supply decoupling.

• Ensure the shunt resistor value is chosen to provide a measurable voltage drop without exceeding the input voltage range of the INA226.
• Avoid long traces for the VIN+ and VIN- connections to minimize noise and ensure accurate measurements.
• The I2C pull-up resistors should be chosen based on the bus capacitance and speed.

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: 0x40 if A0 and A1 are grounded)
#define INA226_ADDRESS 0x40

// INA226 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 (default configuration)
  Wire.beginTransmission(INA226_ADDRESS);
  Wire.write(CONFIG_REGISTER); // 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 shuntVoltage = readRegister(SHUNT_VOLTAGE_REGISTER) * 0.0025; // Convert to volts
  float busVoltage = readRegister(BUS_VOLTAGE_REGISTER) * 0.00125; // Convert to volts

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

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

uint16_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
  uint16_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 (typically 4.7kΩ).
   • Verify the I2C address matches the configuration of the A0 and A1 pins.
   • Check for loose or incorrect wiring.

2. Incorrect Voltage or Current Readings:

   • Verify the shunt resistor value and connections.
   • Ensure the VIN+ and VIN- pins are connected across the shunt resistor.
   • Minimize noise by using short, twisted-pair wires for the shunt connections.

3. Device Not Responding:

   • Confirm the power supply voltage is within the 2.7V to 5.5V range.
   • Check for proper bypass capacitor placement near the V+ pin.

Q: Can the INA226 measure negative currents?
A: No, the INA226 is designed for unidirectional current measurement. For bidirectional current sensing, additional circuitry or a different device is required.

Q: What is the maximum current the INA226 can measure?
A: The maximum current depends on the value of the external shunt resistor and the maximum measurable voltage drop across it (±81.92mV).

Q: Can I use the INA226 with a 3.3V microcontroller?
A: Yes, the INA226 is compatible with 3.3V systems as long as the supply voltage (V+) is within the 2.7V to 5.5V range.