The INA226 is an ultra-high-precision current shunt and power monitor with an I2C and SMBus-compatible interface. It represents a significant step up from the INA219, offering higher accuracy, a wider bus voltage range (up to 36V), and extremely low offset voltage. It monitors both the shunt voltage drop and the bus supply voltage, using an internal multiplier to provide direct readouts of current in Amperes and power in Watts.

Specifications

• Sensed Bus Voltage: 0V to 36V DC
• Operating Voltage (VCC): 2.7V to 5.5V DC
• Maximum Current: 20A (Default with 0.01 Ohm shunt)
• Accuracy:
  • Gain Error: 0.1% (Max)
  • Offset Voltage: 10uV (Max)
• Interface: I2C / SMBus (Up to 16 programmable addresses)
• Current Consumption: 330uA (Typical)
• Operating Temperature: -40°C to +125°C

Pin Description

• VBUS: Bus voltage input (measures the load voltage).
• SDA / SCL: I2C bus data and clock signal lines.
• ALERT: Multi-function programmable alarm output (triggers on over-current, under-voltage, etc.).
• A0 / A1: I2C address pins (determine the device's I2C address).
• IN+ / IN-: Connection points across the external shunt resistor (non-inverting and inverting inputs).

Features

• High-Side or Low-Side Sensing: Unlike many other sensors, the INA226 is flexible enough to be placed on either the positive rail (high-side) or the ground rail (low-side) of the circuit.
• Precision Measurements: With a maximum offset of only 10uV, this module can measure very small current changes with high reliability.
• Comprehensive Data Reporting: Directly provides Bus Voltage, Shunt Voltage, Current, and Power data through its internal registers.
• Configurable Averaging: Hardware-level averaging (up to 1024 samples) allows the module to deliver extremely stable readings even in electrically noisy environments.
• 16 Programmable Addresses: By connecting the A0 and A1 pins to GND, VCC, SDA, or SCL, you can operate up to 16 of these modules on a single I2C bus.

Common Applications

• Telecom & Server Equipment: Monitoring power distribution in high-reliability 24V or 36V systems.
• Precision Power Supplies: Acting as the digital feedback mechanism for DIY bench power supplies or battery chargers.
• Battery Management Systems (BMS): Tracking high-current discharge and charge rates for multi-cell packs.
• Energy Auditing: Detailed power logging for IoT devices and embedded systems.

Usage Tips

• Calibration: To get direct Ampere and Watt readings, you must program the Calibration Register based on the value of the shunt resistor (usually R010 or 0.01 Ohm on the 20A version).
• VBUS Connection: Ensure the VBUS pin is connected to the bus you wish to measure. In high-side sensing, this is usually connected to the IN+ side.
• The Alert Pin: This pin is open-drain. To use it as an interrupt for your microcontroller, you must use a pull-up resistor to your MCU's logic voltage (3.3V or 5V).