Accurate High-Side Current-Sense Amplifier Monitors PWM Load Current

By: Maurizio Gavardoni

Abstract: Accurate high-side current sensing is essential for automotive control systems such as electric power steering, automatic gear shifting, transmission control, engine fuel-injection control, valve control in braking, and active suspensions. All of these applications require precise regulation of the current through a motor or solenoid, to control either the torque of the motor or the drive of the solenoid. The circuit presented in this article includes a precision, high-side current-sense amplifier (MAX9918) for monitoring inductive load currents over a wide range of input common-mode voltages. It is suitable for applications in which the input common voltage can become negative due to inductive kick-back, reverse-battery conditions, or transient events.