INA219 — Zero-Drift, Bidirectional Current / Power Monitor with I2C Interface

Overview

The INA219 is a high-side, bidirectional current and power monitoring IC with an I2C interface manufactured by Texas Instruments. It monitors both shunt voltage drop across an onboard precision current sense resistor ( $0.1\text{ }\Omega$ ) and bus supply voltage up to 26 V DC.

It includes a 12-bit ADC, a programmable multiplier for onboard current (in Amperes) and power (in Watts) calculations, and programmable averaging filtering. It is standard in solar monitoring, battery fuel-gauge systems, and power-metering projects.

Quick reference


Logic supply (`VCC`)	3.0 V to 5.5 V DC
Target bus voltage range (`VIN+`)	0.0 V to +26.0 V DC
Max current range (Standard breakout)	$\pm 3.2\text{ A}$ (with $0.1\text{ }\Omega$ shunt resistor)
Max shunt voltage	$\pm 320\text{ mV}$ (PGA gain /8)
Resolution	12-bit ( $0.8\text{ mA}$ current resolution, $4\text{ mV}$ bus voltage resolution)
I2C slave address	Base `0x40` (selectable `0x40` to `0x4F` via jumpers A0, A1)
Operating current	1 mA active, 6 µA power-down

Pinout

Standard INA219 Breakout Board Header & Screw Terminal

Pin / Terminal	Name	Type	Description
Screw Terminal 1	`VIN+`	High-Side Power Input	Connect to Positive Power Supply Output / Battery
Screw Terminal 2	`VIN-`	High-Side Load Connection	Connect to Positive Load terminal
Header Pin 1	`VCC`	Power	Logic supply (+3.0 V to +5.5 V DC)
Header Pin 2	`GND`	Power	Logic Ground (0 V)
Header Pin 3	`SCL`	Digital Input	I2C Serial Clock input
Header Pin 4	`SDA`	Digital I/O	I2C Serial Data line
Header Pin 5	`Vin+`	Power	High-Side Voltage Input (bridged to terminal `VIN+`)
Header Pin 6	`Vin-`	Power	High-Side Voltage Output (bridged to terminal `VIN-`)

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Logic Supply Voltage	$V_{CC}$	3.0	3.3 / 5.0	5.5	V	DC
Bus Operating Voltage	$V_{BUS}$	0.0	—	26.0	V	$V_{IN+}$ to GND
Max Shunt Voltage Range	$V_{SHUNT}$	-320	—	+320	mV	$V_{IN+} - V_{IN-}$
Bus Voltage Offset Error	$V_{OS,BUS}$	—	4.0	12.0	mV
Shunt Gain Error	$E_{GAIN}$	—	0.2	0.5	%
Quiescent Current	$I_{CC}$	—	1.0	1.5	mA	Active conversion mode
Power-Down Current	$I_{PD}$	—	6	15	µA	Shutdown mode

Register Map

Address	Register	Access	Reset	Description
`0x00`	`CONFIGURATION`	R/W	`0x399F`	Bus voltage range, PGA gain, ADC resolution & mode
`0x01`	`SHUNT_VOLTAGE`	R	`0x0000`	Differential shunt voltage ( $1\text{ LSB} = 10\text{ }\mu\text{V}$ )
`0x02`	`BUS_VOLTAGE`	R	`0x0000`	Bus voltage ( $1\text{ LSB} = 4\text{ mV}$ )
`0x03`	`POWER`	R	`0x0000`	Calculated Power ( $1\text{ LSB} = 20 \times \text{Current\_LSB}$ )
`0x04`	`CURRENT`	R	`0x0000`	Calculated Current ( $1\text{ LSB} = \text{Current\_LSB}$ )
`0x05`	`CALIBRATION`	R/W	`0x0000`	Calibration value ( $0.04096 / (\text{Current\_LSB} \times R_{SHUNT})$ )

Wiring

text

        Power Supply (+12V) ─────► [ VIN+ ]  INA219  [ VIN- ] ─────► Load (+ Terminal)
                                      ▲                 ▲
                                      └───── Shunt ─────┘
                                           (0.1 Ω)

INA219 Breakout Pin	→	Microcontroller / Circuit
`VCC`		`5V` (or `3.3V`)
`GND`		Common `GND` (MCU GND + Load GND)
`SDA`		`SDA` (A4 on Uno, GPIO21 on ESP32)
`SCL`		`SCL` (A5 on Uno, GPIO22 on ESP32)

Warning

High-Side Voltage Limit: The target bus voltage ( $V_{IN+}$ ) MUST NOT exceed 26.0 V DC. Attempting to measure mains AC or DC voltages $> 26\text{ V}$ will permanently destroy the INA219 chip.

Common mistakes

Low-side wiring instead of high-side: The INA219 is designed for high-side current measurement (inserted on the positive supply wire). Wiring it on the ground side distorts ground reference levels for downstream sensors.
Forgetting common ground: Not connecting the microcontroller ground to the power supply ground prevents I2C communication and causes erratic readings.
Uncalibrated current register reads: The CURRENT (0x04) and POWER (0x03) registers remain zero until software writes a valid value to the CALIBRATION register (0x05).

Notes

Modifying the onboard sense resistor to a $0.01\text{ }\Omega$ shunt expands maximum current measurement up to $\pm 32\text{ A}$ .