Overview
Monitoring multiple power rails usually means juggling several multimeters, moving probes around, and still missing transient current spikes. This Adafruit INA3221 breakout board simplifies that entire workflow by allowing you to monitor three independent power supplies simultaneously, measuring both bus voltage and DC current over a single I2C connection.
Unlike traditional low-side current meters that require inserting a shunt resistor in the ground path, this board supports true high-side current sensing. That means you can place the measurement point between the power source and the load without disturbing the system ground reference—critical for sensitive digital and mixed-signal electronics. Despite being powered from just 3V or 5V, the INA3221 can accurately measure bus voltages up to 26V DC, making it ideal for battery-powered systems, solar panels, and multi-rail embedded designs.
Each channel includes a precision 0.05Ω, 1% sense resistor paired with an internal amplifier capable of handling a differential input of ±163.8 mV. This allows current measurement up to ±3.2A per channel with a fine 0.4 mA resolution thanks to the onboard 13-bit ADC. For advanced users, the onboard sense resistors can be removed and replaced with lower-value shunts—such as 0.01Ω—to extend the measurable current range up to 16A, at the cost of reduced resolution.
Getting started is straightforward: power the board with 2.7–5.5V, connect SDA and SCL to your microcontroller, and wire each monitored supply through the VIN+/VIN– terminals. Official libraries are available for Arduino, CircuitPython, and Python, making it compatible with everything from basic ATmega-based boards to Raspberry Pi and other Linux SBCs.
Specification
Technical details for Adafruit INA3221 Triple 26V ±3.2A DC Power Monitor.
| Specification | Details |
|---|---|
| IC / Chipset | INA3221 (Triple-Channel Shunt & Bus Voltage Monitor) |
| Monitoring Channels | 3 independent channels |
| Bus Voltage Sensing Range | 0V to 26V DC |
| Board Supply Voltage (VCC) | 2.7V to 5.5V |
| Current Sensing Method | High-side or low-side shunt measurement |
| Sense Resistors (Onboard) | 0.05Ω, 1% (one per channel; replaceable for custom range) |
| Max Differential Input (Shunt) | ±163.8mV (amplifier input limit) |
| Default Current Range | Up to ±3.2A per channel (with 0.05Ω shunt) |
| ADC Resolution | 13-bit |
| Current Resolution | 0.4mA at ±3.2A range |
| Accuracy | ±1% (typical measurement precision) |
| Offset Voltage | ±80µV (max) |
| Gain Error | 0.25% (max) |
| Averaging | Configurable averaging options |
| Interface | I2C |
| I2C Addresses | 0x40 (Default) 0x41 (by closing solder jumper) |
| Alert Outputs | Programmable Warning and Critical IRQ pins |
| Logic Level | Matches board supply voltage (3V or 5V I2C logic) |
| Libraries / Software Support | Arduino, CircuitPython, Python |
| Dimensions | 38.6mm × 22.9mm × 10.5mm |
| Weight | 5.8g |
Pinout
| Pin / Connector | Description |
|---|---|
| VCC | Board power input (2.7V–5.5V). Match microcontroller logic level (3V or 5V). |
| GND | Common ground for power and logic. |
| VPU | Pull-up supply for VALID interrupt pin. Connect to VCC when using VALID. |
| SCL | I2C clock input. 3–5V logic, onboard 10K pull-up. |
| SDA | I2C data line. 3–5V logic, onboard 10K pull-up. |
| STEMMA QT | JST-SH connector for I2C + power (Qwiic compatible). |
| VIN1+ / VIN1- | Channel 1 current & voltage sense inputs (up to 26V). |
| VIN2+ / VIN2- | Channel 2 current & voltage sense inputs (up to 26V). |
| VIN3+ / VIN3- | Channel 3 current & voltage sense inputs (up to 26V). |
| WRN | Warning alert interrupt (active-low, averaged current threshold). |
| CRI | Critical overcurrent interrupt (active-low). |
| TC | Power-up sequence timing alert interrupt (active-low). |
| VALID | Power-valid alert interrupt (upper limit = HIGH, lower limit = LOW). Requires VPU. |
| Addr (Jumper) | I2C address select: open = 0x40 (default), closed = 0x41. |
| Power LED | Green LED indicates board power. |
| LED (Jumper) | Cut trace to disable the power LED. |
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