How to Use INA228: Examples, Pinouts, and Specs

The INA228 is a high-precision, low-power current shunt monitor designed to measure current, voltage, and power in high-performance applications. It provides a digital output proportional to the current flowing through an external shunt resistor. With its wide common-mode voltage range and integrated ADC, the INA228 is ideal for applications requiring accurate power monitoring, such as battery management systems, server power supplies, and industrial automation.

• Battery management systems
• Power monitoring in servers and data centers
• Solar inverters and energy storage systems
• Industrial automation and motor control
• Electric vehicle (EV) power systems

The INA228 offers robust performance and flexibility for a variety of applications. Below are its key technical specifications:

The INA228 is typically available in a small package, such as a WSON-10. Below is the pinout and description:

The INA228 is straightforward to integrate into a circuit for current, voltage, and power monitoring. Below are the steps and considerations for using the component:

1. Shunt Resistor Selection:

   • Choose a shunt resistor with a low resistance value to minimize power loss.
   • Ensure the resistor's power rating can handle the maximum expected current.
   • The INA228 measures the voltage drop across this resistor to calculate current.

2. Power Supply:

   • Connect the V_CC pin to a stable 2.7 V to 5.5 V power source.
   • Decouple the power supply with a 0.1 µF ceramic capacitor close to the V_CC pin.

3. I²C Communication:

   • Connect the SCL and SDA pins to the corresponding I²C lines of the microcontroller.
   • Use pull-up resistors (typically 4.7 kΩ) on the SCL and SDA lines.

4. Alert Pin (Optional):

   • The ALERT pin can be used to signal fault conditions. Connect it to a microcontroller GPIO pin if needed.

5. Address Configuration:

   • Use the ADDR pin to set the I²C address of the INA228. Refer to the datasheet for address selection details.

The INA228 can be interfaced with an Arduino UNO using the I²C protocol. Below is an example code snippet to read shunt voltage and calculate current:

#include <Wire.h>

// INA228 I2C address (default: 0x40, adjust if ADDR pin is configured differently)
#define INA228_ADDRESS 0x40

// Register addresses (refer to the INA228 datasheet for details)
#define REG_SHUNT_VOLTAGE 0x04

// Shunt resistor value in ohms (adjust based on your circuit)
#define SHUNT_RESISTOR 0.01

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

void loop() {
  float shuntVoltage = readShuntVoltage(); // Read shunt voltage
  float current = shuntVoltage / SHUNT_RESISTOR; // Calculate current

  // Print the results
  Serial.print("Shunt Voltage (mV): ");
  Serial.println(shuntVoltage * 1000); // Convert to millivolts
  Serial.print("Current (A): ");
  Serial.println(current);

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

float readShuntVoltage() {
  Wire.beginTransmission(INA228_ADDRESS);
  Wire.write(REG_SHUNT_VOLTAGE); // Point to the shunt voltage register
  Wire.endTransmission(false); // Send repeated start condition
  Wire.requestFrom(INA228_ADDRESS, 2); // Request 2 bytes of data

  if (Wire.available() == 2) {
    uint16_t rawData = (Wire.read() << 8) | Wire.read(); // Combine MSB and LSB
    return rawData * 0.00000125; // Convert to volts (LSB = 1.25 µV)
  }

  return 0.0; // Return 0 if no data is available
}

• Use a high-precision, low-temperature-coefficient shunt resistor for accurate measurements.
• Keep the traces between the shunt resistor and the INA228 as short as possible to minimize noise.
• Ensure proper decoupling of the power supply to avoid voltage fluctuations.

1. No Communication with the INA228:

   • Verify the I²C address matches the configuration of the ADDR pin.
   • Check the pull-up resistors on the SCL and SDA lines.

2. Incorrect Current Measurements:

   • Ensure the shunt resistor value is correctly defined in the code.
   • Verify the connections to the V_IN+ and V_IN- pins are secure and correct.

3. Alert Pin Not Functioning:

   • Confirm the ALERT pin is configured correctly in the microcontroller code.
   • Check the fault thresholds programmed into the INA228.

Q: Can the INA228 measure bidirectional current?
A: Yes, the INA228 can measure both positive and negative currents, depending on the direction of current flow through the shunt resistor.

Q: What is the maximum current the INA228 can measure?
A: The maximum measurable current depends on the shunt resistor value and the ±163.84 mV shunt voltage range. For example, with a 0.01 Ω resistor, the maximum current is ±16.384 A.

Q: Is the INA228 suitable for high-voltage applications?
A: Yes, the INA228 supports a common-mode voltage range of -0.3 V to +85 V, making it suitable for high-voltage systems.

Q: Can I use the INA228 with a 3.3 V microcontroller?
A: Yes, the INA228 operates with a supply voltage of 2.7 V to 5.5 V and is compatible with 3.3 V logic levels.