INA3221 3-channel power monitor: specs and pinout
A three-channel high-side current and bus-voltage monitor chip with an I2C/SMBus interface. This page covers the INA3221 chip; the module board (shunt resistor values, address jumpers, pull-ups, connectors) is not covered by an official document.
Specs
| Spec | Value | Source |
|---|---|---|
| Supply voltage VS | 2.7 V to 5.5 V | source Recommended Operating Conditions, p.4 |
| Bus voltage range | 0 V to 26 V on each channel | source Electrical Characteristics, p.5 |
| Shunt voltage range | -163.84 mV to 163.8 mV across each shunt | source Electrical Characteristics, p.5 |
| Resolution | 13-bit ADC; 40 uV per LSB (shunt), 8 mV per LSB (bus) | source Electrical Characteristics, p.5 |
| Accuracy | Shunt and bus gain error 0.1% typ, 0.25% max; shunt offset +/-40 uV typ, +/-80 uV max (25 C) | source Electrical Characteristics, p.5 |
| Interface and address | I2C and SMBus; address set by pin A0: GND = 0x40, VS = 0x41, SDA = 0x42, SCL = 0x43 | source Table 7-1, p.19 |
| Supply current | 350 uA typical | source Description, p.1 |
| Alert outputs | Critical, Warning, Power Valid and Timing Control, all open-drain | source Table 5-1 Pin Functions, p.3 |
| Bus timeout | 28 ms timeout on the interface (typ) | source Electrical Characteristics p.5; Programming p.19 |
| Operating temperature | -40 C to 125 C | source Recommended Operating Conditions, p.4 |
Power
| Value | Source | |
|---|---|---|
| Supply | VS 2.7-5.5 V; the measured buses can be 0-26 V | source Description p.1; Recommended Operating Conditions p.4 |
| Current | 350 uA typical from VS | source Description p.1; Recommended Operating Conditions p.4 |
Chip pins
These are the pins of the chip on the module, from the chip datasheet. The module's own header may label or expose them differently.
The pins above belong to the INA3221 chip. The module board is not covered by an official document. Shunt resistor values and breakout header names are not verified.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| IN+1 / IN-1 (12 / 11) | Channel 1 shunt inputs (supply side / load side) | 0-26 V | Bus voltage is measured from IN- to ground | source Table 5-1, p.3 |
| IN+2 / IN-2 (15 / 14) | Channel 2 shunt inputs | 0-26 V | source Table 5-1, p.3 | |
| IN+3 / IN-3 (2 / 1) | Channel 3 shunt inputs | 0-26 V | source Table 5-1, p.3 | |
| VS (4) | Power supply | 2.7-5.5 V | source Table 5-1, p.3 | |
| GND (3) | Ground | source Table 5-1, p.3 | ||
| SCL (6) | Serial clock, open-drain input | source Table 5-1, p.3 | ||
| SDA (7) | Serial data, open-drain I/O | source Table 5-1, p.3 | ||
| A0 (5) | Address pin | GND, VS, SDA or SCL | Sets I2C address | source Table 5-1 p.3; Table 7-1 p.19 |
| Critical (9) | Conversion-triggered critical alert, open-drain | source Table 5-1, p.3 | ||
| Warning (8) | Averaged measurement warning alert, open-drain | source Table 5-1, p.3 | ||
| PV (10) | Power valid alert, open-drain | source Table 5-1, p.3 | ||
| TC (13) | Timing control alert, open-drain | source Table 5-1, p.3 | ||
| VPU (16) | Pull-up supply used to bias the power valid output | up to 26 V | source Table 5-1, p.3 |
Build with it
Project ideas for the INA3221 3-channel power monitor. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- Solar charge monitor: Channel 1 can watch the panel, channel 2 the battery and channel 3 the load, each on its own shunt with the bus under 26 V; the ESP32 3.3 V supply is inside the chip's 2.7-5.5 V range. Learning project: read the shunt value printed on the module to set the maximum current.
- Three-rail bench logger: Each channel measures a separate rail up to 26 V; the Uno 5 V supply is inside the chip's range and the LCD address does not collide with 0x40-0x43.
- Battery pack discharge test: A discharge run is slow, so the 13-bit resolution and averaging are adequate; the INA226 can cross-check one channel. Use cells with protection and never short the shunt inputs.
Common mistakes
- Letting the voltage across a shunt exceed about 163.8 mV: the shunt input range is -163.84 to +163.8 mV, so the shunt value sets the maximum current per channel and the value on the module is not documented here (source)
- Putting more than 26 V on a bus input, or more than 5.5 V on VS (absolute maximum 6 V) (source)
- Changing the A0 address pin while running: the pin is sampled on every bus communication and must be set before any activity; SDA, SCL and the alert pins are open-drain and need pull-ups (source)
Not covered by the official source
- Module board undocumented: shunt resistor value, A0 strap, pull-ups and connector order unknown.
- Digital logic thresholds are not given here.
Sources
- link (TI INA3221, SBOS576C, May 2012 revised Sept 2026; maker)