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.