Operation
6
SBOU244 – June 2020
Copyright © 2020, Texas Instruments Incorporated
INA281EVM
4
Operation
4.1
Quick Start Setup
Follow these procedures to set up and use one of the panels of the INA281EVM. For the following
instructions, X is pinout A or B, and n is gain option 1, 2, 3, 4, or 5.
Step 1.
Choose the desired gain option panel and pin out variation.
Step 2.
Connect an external dc supply voltage (between 1.7 V and 20 V) to a VS test point, and
connect the ground reference of that supply to a GND test point on the same panel.
Step 3.
Provide a differential input voltage signal to the Vin+ and Vin– nodes by connecting the signal
leads to the J1_Xn pin 1 and J1_Xn pin 2 on the EVM, as explained in
. The
INA281 is a unidirectional current-sensing device because there is no reference pin;
therefore, the device can only measure current in one direction.
4.2
Measurements
The INA281EVM allows the user to either emulate the voltage developed across a sense resistor based
on a given set of system conditions, or to connect the device inputs to an external shunt. Optionally, a
surface-mount technology (SMT) shunt resistor can be soldered across the Vin+ and Vin– pads, and these
inputs can be connected in series with the external system and load.
To configure a measurement evaluation without a the onboard shunt resistor, follow this procedure:
1. Connect a positive differential voltage across the Vin+ (J1_Xn) and Vin– (J1_Xn) tabs. Given the
internal GND reference of the device, make sure that the Vin+ pin is the more positive of the two
inputs.
2. Additionally, if the differential voltage supply is a floating supply, connect a –4-V to 110-V common-
mode voltage to the inputs by connecting the positive lead of the external voltage source to the
Vin– (J1_Xn) tab, and source ground to a GND test point. This action effectively raises the absolute
common-mode voltage of the input pins, while still retaining a positive input differential signal.
3. 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
Getting Started with TI Precision
Labs - Current Sense Amplifiers: Shunt Resistor Layout
4. Measure the output voltage at the Vout test point with respect to GND.
To configure a measurement evaluation with a shunt resistor, follow this procedure:
1. Solder a 2512 resistor at the R1_Xn pads that connects the Vin+ (J1_Xn) and Vin– (J1_Xn) inputs.
2. Connect the Vin+ (J1_Xn) and Vin– (J1_Xn) tabs in series with the load and bus voltage sources
while powered off.
WARNING
If measuring current, first make sure that the equipment (shunt
resistor, wires, connectors, and so on) can support the
amperage and power dissipation. Secondly, make sure that the
current flowing through J1 does not exceed 5 A. Failure to do so
can result in hot surfaces (> 55°C), damage to the EVM, or
personal injury.
3. Power on the system and measure the output voltage at the Vout test point. Vout is equal to the
gain of the device multiplied by the differential voltage measured directly at the device input pins.
