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INA281

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8.2.2 Detailed Design Procedure

The INA281 is designed to measure current in a typical solenoid application. The INA281 measures current

across the 50-mΩ shunt that is placed at the output of the half-bridge. The INA281 measures the differential

voltage across the shunt resistor, and the signal is internally amplified with a gain of 50 V/V. The output of the

INA281 is connected to the analog-to-digital converter (ADC) of an MCU to digitize the current measurements.

Solenoid loads are highly inductive and are often prone to failure. Solenoids are often used for position control,

precise fluid control, and fluid regulation. Measuring real-time current on the solenoid continuously can indicate

premature failure of the solenoid which can lead to a faulty control loop in the system. Measuring high-side

current also indicates if there are any ground faults on the solenoid or the FETs that can be damaged in an

application. The INA281, with high bandwidth and slew rate, can be used to detect fast overcurrent conditions to

prevent the solenoid damage from short-to-ground faults.

The INA281 is a unidirectional current-sense amplifier that is meant to operate with a positive differential input

8.2.3 Application Curve

Figure 31 shows the output response of a solenoid.

Figure 31. Solenoid Control Current Response

9 Power Supply Recommendations

The INA281 power supply can be 5 V, whereas the input common-mode voltage can vary between –4 V to 110

V. The output voltage range of the OUT pin, however, is limited by the voltage on the power-supply pin.