INA219 DC Power Sensor

The INA219 ICIntegrated Circuit is a high-side current and voltage monitor chip using an external shunt resistor. It can measure voltage, current, and power consumption in an external circuit. This hardware overview of the INA219 IC and Modules covers specs, board layout, pinout, and operation.

INA219 IC

The INA219 ICIntegrated Circuit is a high-side current and voltage monitor chip with an I2CInter-Integrated Circuit. Also referred to as IIC or I²C. interface that operates from a single 3V to 5.5V DC supply. It has a Programmable Gain Amplifier (PGAA Programmable Gain Amplifier (PGA) is an electronic amplifier whose gain can be controlled by external digital or analog signals.) and 12-Bit ADCAnalog-to-Digital Converter (ADC, A/D, or A-to-D) for continuous or trigger operation. It also has programmable calibration, gain, filtering, and ADC resolution.

The INA219 measures the voltage, current, and power consumption of a circuit using an external shunt resistor. It can output the following measurements on an external load circuit:

Bus Voltage [Volts]
Shunt Voltage [Volts]
Current [Amps]
Power [Watts]

The load supply voltage can also be computed by summing the shunt and bus voltages: V_LOAD = V_SHUNT + V_BUS. The INA219 measures bus voltage on the load side instead of load power supply according to the INA219 Datasheet (PDF). These voltages are shown in the figure below.

INA219 High-Side Current/Voltage Sensing

Inside the INA219 IC the PGA and ADC measures the differential voltage V_IN = V_IN+ - V_IN- across an external shunt resistor. Using internal switching this device monitors both the shunt voltage drop and the bus voltage V_BUS = V_IN- - GND on an external load. In order to calculate the current and power values, the user must program the resolution of the Current Register and value of the shunt resistor.

INA219 Functional Diagram from Datasheet — INA219 Functional Diagram (Source: Datasheet)

Specs

INA219 Specs
Feature	Description
IC Info	INA219 High-Side Current/Power Monitor by Texas Instruments (TI) INA219 Product Page INA219 Datasheet (PDF)
Voltage Supply (V_S)	3.0V to 5.5V single supply
Interface	I2C 2-Wire (SCL, SDA) Fast Mode (1kHz to 400kHz) High-Speed Mode (1kHz to 2.56MHz)
Analog Inputs Differential (VIN+ - VIN-)	±26V
Analog Inputs Common-Mode (VIN+ + VIN-)/2	-0.3V to 26V
ADC Resolution	12-Bit (15-Bit Averaging)
Offset Voltage	PGA = 1: 10μV typical, 100μV max PGA = 1/2: 20μV typical, 125μV max PGA = 1/4: 30μV typical, 150μV max PGA = 1/8: 40μV typical, 200μV max
Offset Voltage Drift	0.1μV/°C
Max Shunt Voltage	PGA = 1: 40mV PGA = 1/2: 80mV PGA = 1/4: 180mV PGA = 1/8: 320mV
Operating Temperature	-40°C to 125°C

PGA Gain & Range

The PGA configuration sets the gain and Full-Scale Range (FSR) of voltage across the shunt resistor. The PGA gain settings in the table below can be found in Table 4 of the INA219 Datasheet (PDF).

INA219 PGA Settings
PGA Gain	FSR
1	±40mV
1/2	±80mV
1/4	±160mV
1/8	±320mV

Resolution & Sampling

The ADC resolution settings adjust the number of ADC bits or number of samples used when averaging results for the Bus Voltage Register and Shunt Voltage Register. Higher ADC resolution or sampling requires longer conversion times. The ADC resolution settings in the table below can be found in Table 5 of the INA219 Datasheet.

INA219 ADC Settings
Bit/Samples	Conversion Time
9-Bit / 1 Sample	84µs
10-Bit / 1 Sample	148µs
11-Bit / 1 Sample	276µs
12-Bit / 1 Sample	532µs
12-Bit / 2 Samples	1.06ms
12-Bit / 4 Samples	2.13ms
12-Bit / 8 Samples	4.26ms
12-Bit / 16 Samples	8.51ms
12-Bit / 32 Samples	17.02ms
12-Bit / 64 Samples	34.05ms
12-Bit / 128 Samples	68.10ms

Registers

The INA219 has six 16-bit registers for Configuration, Shunt Voltage, Bus Voltage, Power, Current, and Calibration. You can read or write to the configuration and calibration registers.

The configuration register includes Reset, ADC resolution, gain, and bus range. The calibration register contains a scale factor used for adjusting the current resolution. The Shunt Voltage, Bus Voltage, Power, and Current registers are read-only the provide measured or calculated data.

INA219 Registers
Register	Hex Address	Read/Write
Configuration	0x00	Read/Write
Shunt Voltage	0x01	Read-Only
Bus Voltage	0x02	Read-Only
Power	0x03	Read-Only
Current	0x04	Read-Only
Calibration	0x05	Read/Write

Chip Versions

The INA219 IC comes in a SOIC-8 (3.91mm x 4.90mm) or SOT-23 (1.63mm x 2.90mm) package. There are two versions of the INA219 chip: A and B. The A version has a ±1% total max current measurement error over the entire operating temperature range and the B version has a ±0.5% total max current measurement error over the entire operating temperature range, but the overall functionality is otherwise the same. The markings on the chip indicate whether its the A or B version.

INA219 Modules

Breakout board modules are available for INA219 that have pin through holes with 0.1" (2.54mm) spacing so you can easily attach it to a breadboard and 3.5mm terminal plug mount holes so you can easily connect your load.

Most INA219 modules have a 0.1Ω 1% shunt resistor that can measure up to 3.2A with ±0.8mA resolution. The module power supply can be in the range of 3V to 5.5V and the load supply voltage can be in the range of 0V to 26V DC.

There are two common INA219 modules: the Adafruit (PID 904) module and a generic module. Both modules have a 0.1Ω 1% shunt resistor that can measure up to 3.2A with ±0.8mA resolution. The Adafruit board has a small size of 25.6mm x 20.4mm (1.0in x 0.8in) and the generic boards usually have a size about 25.5mm x 22.3mm (1.0in x 0.9in). The main difference between these modules is the Adafruit module has STEMMA QTSTEMMA QT ('cutie') connectors are Adafruit's name for 4-pin JST SH connectors with 1.0mm pitch. These connectors were implemented on Adafruit boards to make it easy to plug-n-play various sensors and devices without soldering and wiring. The STEMMA QT (JST SH) are a smaller connector than the STEMMA (JST PH) that do not fit on smaller boards. STEMMA QT is cross-compatible with SparkFun Qwiic connectors. connectors for I2C and an onboard power LEDLight Emitting Diode.

Adafruit INA219 Module

The Adafruit board comes with a 6-pin header and a 3.5mm terminal plug for the load. On each side of the board are STEMMA QTSTEMMA QT ('cutie') connectors are Adafruit's name for 4-pin JST SH connectors with 1.0mm pitch. These connectors were implemented on Adafruit boards to make it easy to plug-n-play various sensors and devices without soldering and wiring. The STEMMA QT (JST SH) are a smaller connector than the STEMMA (JST PH) that do not fit on smaller boards. STEMMA QT is cross-compatible with SparkFun Qwiic connectors. connectors for supplying power VCC to the INA219 chip and the two I2C lines (SCLSerial Clock (SCL) is the output clock signal line from the master device. Also referred to as SCK, SCLK, or CLK. and SDASerial Data Line ).

Adafruit INA219 Breakout (PID 904) — Adafruit INA219 Module

Adafruit INA219 Board Layout (Bottom View)

On the back of the board are A0 and A1 solder jumpers that can be bridged with solder to change the I2C address to the list below.

Default = 0x40
A0 soldered = 0x41
A1 soldered = 0x44
A0 and A1 soldered = 0x45

There is also an LED jumper that can be cut to disable the board's power LED if you want to reduce power consumption.

Adafruit provides a tutorial on the board, including pinout, assembly, Arduino code, CircuitPython code, schematic, and PCB. They provide an Arduino Library and CircuitPython Library on GitHub for communicating with the device over I2C.

Generic INA219 Module

The Generic INA219 modules are similar to the Adafruit module, with the same functionality, except they do not include the STEMMA QT connectors for I2C and the onboard power LED. A couple other minor differences are the power pin is labeled VCC instead of VIN and the I2C solder jumpers are on the front of the board instead of the back of the board.

Generic INA219 Board Layout (Bottom View)

Basic Hookup

The INA219 module can be powered from 3V to 5V. If you're using a microcontroller board or SBCSingle Board Computer, they often have a 3.3V/5V output pin that you can connect to the INA219 VCC, where the device ground GND must be connected to the INA219 GND.

The two I2C communication lines (SCLSerial Clock (SCL) is the output clock signal line from the master device. Also referred to as SCK, SCLK, or CLK. and SDASerial Data Line) also needs to be connected between the INA219 and the device. The INA219 modules usually have built-in 10kΩ pull-up resistors to VCC on both I2C lines. Since I2C bus drivers are open drain drivers, they can drive drive their output low, but cannot drive it high. For the line to be able to go high there has to be pull-up resistors.

The current needs to be measured on the high-side, so the load power supply is connected directly to the INA219 V_IN+ pin and the V_IN- pin is connected to the load resistor and then to ground. There are two ways of connecting the load, either through the terminal holes using a 3.5mm screw terminal plug or by using the pin through holes (PTH).

INA219 Module Hookup using Screw Terminals — INA219 Module Hookup (Terminals)

INA219 Module Hookup using Pin Through Holes — INA219 Module Hookup (PTH)

Calibration

By default the INA219 has an ADC setting with 12-Bit resolution and 1 sample, a gain setting of 320mV shunt full-scale range (PGA = 1/8), and a 32V bus full-scale voltage range, using continuous conversion of shunt and bus voltage.

These default settings use the largest range of input voltage and current, but with the lowest resolution. If the maximum current and bus voltage are known, these default settings can be changed to improve the resolution of voltage and current readings.

First the current LSBThe Least Significant Bit (LSB) in a binary number is the bit that represents the smallest place value carrying the lowest weight. It is also sometimes referred to as the low-order bit or right-most bit due to the convention in positional notation of writing less significant digits further to the right. needs to be determined from the maximum expected currently. The current register has a value in the range ±2¹⁵. It is common to select a value for the Current_LSB to the nearest round number above this value to simplify the conversion of the Current Register and Power Register to amps and watts respectively.

The calibration register is calculated based on the current LSB (Current_LSB) and shunt resistance (R_SHUNT). The constant 0.04096 is an internal fixed value used to ensure scaling is maintained properly.

The table below gives examples of rounded Current_LSB and Cal values for different maximum expected currents.

INA219 Current_LSB and Cal Values
Max Expected Current	Current LSB	Current LSB (Rounded)	Cal
400mA	0.012mA	0.2mA	20480
800mA	0.024mA	0.04mA	10240
1.6A	0.049mA	0.05mA	8192
3.2A	0.098mA	0.1mA	4096

When the calibration register is supplied with the Cal value, the current register can compute the current value internally from the Shunt_Voltage_Register using the equation below.

The gain can be determined from max expected current by finding the minimum full-scale voltage range (40mV, 80mV, 160mV, 320mV) that is above the max expected shunt voltage (V_SHUNT(Max) = Max_Expected_Current∙R_SHUNT). For example, if Max_Expected_Current is 1A, where R_SHUNT = 0.1Ω, then the max expected shunt voltage is 1A∙0.1Ω = 100mA, the minimum full-scale range > 100mA is 160mV, and the gain is 1/4.

Gain from Max Expected Current
Max Expected Current	Max Expected Shunt Voltage	Shunt Voltage Range	Gain
I < 400mA	V < 40mV	40mV	1
400mA ≤ I < 800mA	40mV ≤ V < 80mV	80mV	1/2
800mA ≤ I < 1.6A	80mV ≤ V < 160mV	160mV	1/4
1.6A ≤ I < 3.2A	160mV ≤ V < 320mV	320mV	1/8

The bus voltage is measured from V_IN- to ground (V_BUS = V_IN- - GND) on an external load and its full-scale range can be set to either 0V to 16V or 0V to 32V. Using the smaller 16V range can improve the resolution of the bus voltage readings and also the power readings, since the Power Register is internally computed from the product of the current register and bus voltage register.

0V to 16V Bus Range:: The bus voltage range is set from 0V to 16V using the hex address 0x0000.
0V to 32V Bus Range:: The bus voltage range is set from 0V to 32V using the hex address 0x2000.

Readings

The voltage, current, and power values read from the registers need to be converted to a meaningful format. The table below gives the conversion factors for the Current_Register, Shunt_Voltage_Register, Bus_Voltage_Register, and Power_Register.

INA219 Register Conversions
Reading	Register Conversion
Bus Voltage [V]	(Bus_Voltage_Register << 3) x 4 / 1000
Shunt Voltage [mV]	Shunt_Voltage_Register / 100
Current [mA]	Current_Register x Current_LSB x 1000
Power [mW]	Power_Register x Power_LSB x 1000

Bus Voltage [V]:: The Bus Voltage Register has an address of 0x02 and is internally measured at the V_IN- pin to calculate the voltage level delivered to the load. The Bus Voltage register bits are not right-aligned; therefore, they must be shifted right by 3 bits. Multiply the shifted contents by the 4mV LSB to compute the bus voltage measured by the device in volts.
Shunt Voltage [mV]:: The Shunt Voltage Register has an address of 0x01 and is the voltage measured across the shunt resistor. The shunt voltage has an LSB of 10μV, which is 1mV/100. To get the shunt voltage in mV, the shunt voltage register must be multiplied by the 1mV/100 LSB.
Current [mA]:: The current register has an address of 0x04 and is the current through the shunt resistor that is internally computed from the shunt voltage register and calibration register (see Figure 13). The current register content is multiplied by the Current_LSB and converted from Amps to milliAmps by a factor of 1000.
Power [mW]:: The Power Register has an address of 0x03 and is internally computed from the product of the current register and bus voltage register. The Power Register content is multiplied by Power LSB which is 20 times the Current_LSB for a power value in Watts. To convert Watts to milliWatts, the power is multiplied by 1000.

These conversions are performed internally by libraries discussed in the next section.

Libraries

Arduino

The two most common libraries in Arduino code are the Adafruit_INA219 and INA219_WE. Both of these libraries can be found and installed using the Arduino IDEIntegrated Development Environment (IDE) is a software application that helps develop software code efficiently. Library Manager or they can be downloaded from GitHub. The Wire Library is also used to communicate over I2C and is already included in the Arduino IDE by default.

The Adafruit_INA219 library was created by Adafruit for their INA219 module, although the library also works with generic modules. The INA219_WE library was created by Wolfgang Ewald to provide more functionality and control over the INA219.

The Adafruit library is the easiest to use with three pre-calculated calibration options (32V 2A, 32V 1A, and 16V 400mA) and simple function commands to make measurements. The INA219_WE library has more functionality and control that allows you to set the gain and bus voltage range, choose between continuous or trigger measurement modes, set ADC mode resolution and conversion times, set a correction factor and shunt offset voltage, and check for overflow.

CircuitPython & MicroPython

The two most common libraries in Python are the Adafruit_CircuitPython_INA219 in CircuitPython and pyb_ina219 in MicroPython. Both of these libraries can be downloaded from GitHub.

The Adafruit CircuitPython library uses its own BusDevice Library and Register Library for communicating over I2C. The pyb_ina219 MicroPython library uses the I2C Class from the built-in Machine library.

The Adafruit library is the easiest to use with three pre-calculated calibration options (32V 2A, 32V 1A, and 16V 400mA) and simple function commands to read measurements. The pyb_ina219 library has more functionality and control that allows you to set the gain and bus voltage range, set ADC resolution/sampling, set wake or sleep modes, and check for overflow. Both libraries currently only support continuous reads of voltage and power, but not triggered reads.

Conclusion

This hardware overview of the INA219 IC and Modules covered specs, board layout, pinout, operation, basic hookup, and libraries in Arduino, CircuitPython, and MicroPython.

The output of the INA219 is an I2C digital communication interface that can be read using libraries. The Adafruit libraries in Arduino or CircuitPython are is the easiest to use with pre-calculated calibration options and simple function commands to read measurements, while the the custom made libraries in Arduino or MicroPython have more functionality to control of the INA219.

The INA219 has a wide input voltage of ±26V, and with a 0.1Ω shunt resistor it supports up to 3.2A with 0.8mA resolution. The programmable gain and ADC resolution allows you to lower the input range to 16V 400mA to improve the resolution to 0.1mA. The I2C interface makes it compatible with most microcontrollers and Single Board Computers (SBCs).

Products

INA219 DC Power Sensor Products

Created: 21Oct2022 20:27:49 UTC 2022-10-21T20:27:49Z
Updated: 13May2024 00:25:43 UTC 2024-05-13T00:25:43Z

The INA219 IC measures the current and voltage drop across an external shunt resistor with high side sensing and also measures the bus supply voltage. The shunt current, shunt voltage, and bus voltage are output through an I2C interface.