Operation
10
SBOU241A – April 2020 – Revised June 2020
Copyright © 2020, Texas Instruments Incorporated
INA228, INA229, INA237, INA238, and INA239 EVM User’s Guide
4.2.2
Current Sensing Operation
The EVM allows the user to either emulate the voltage developed across a sense resistor based on a
given set of system conditions by applying a differential voltage across the IN+ and IN– terminals directly,
or to connect the device inputs to an external shunt. Optionally, a surface-mount technology (SMT) shunt
resistor can be soldered across the pads of R1, and these inputs can be connected in series with the
external system and load current. There are 2 terminals each for IN+ (J1 pins 5 and 6) and IN– (J1 pins 3
and 4) for convenience.
To configure a measurement evaluation without a shunt resistor, follow these steps:
1. Connect a differential voltage across the IN+ and IN– terminals as shown in
a. If the differential voltage supply is a floating supply, connect a –0.3-V to 85-V common-mode
voltage (leave powered off until finished setting up) to the inputs by connecting the positive lead of
the external voltage source to either the IN+ or IN– terminal. This action effectively raises the
absolute common-mode voltage of the input pins. Make sure that the differential voltage plus or
minus the common-mode voltage does not go out of the –0.3-V to 85-V range.
Figure 8. IN+ and IN– Wiring Without a Shunt Resistor
2. Connect the VBUS terminal (J1 pin 2) to the desired bus voltage (likely either IN+ or IN–).
3. Connect the source ground to the GND terminal (J1 pin 1).
4. Power on the system, and observe the device states and outputs through the GUI.
To configure a measurement evaluation with a shunt resistor, follow these steps:
1. Connect a shunt resister by doing either of the following:
a. Solder a 2512 resistor across the pads of R1 that connects the IN+ and IN– inputs.
b. Connect an external shunt across the IN+ and IN– terminals of J1, preferably across pins 4 and 5,
as shown in
.
i.
If an external shunt is being used, make the connections such that the sensing location is
across the shunt and there will be no high current on the sensing path. See the
Labs - Current Sense Amplifiers: Shunt Resistor Layout
video for more information.
2. Connect the IN+ and IN– terminals in series with the load while powered off.
