Bi-directional current monitoring circuit for low-side current sensing of vertical power field effect transistor and method thereof

Abstract

A bi-directional current monitoring circuit and method for a field effect transistor (FET) configured as a low-side power switch in a power stage enables positive current sensing and negative current sensing using voltages that are above the ground voltage. In some embodiments, the bi-directional current monitoring circuit and method measures the current flowing through a low-side power FET in a power stage using a smaller size sense FET connected substantially in parallel with the low-side power FET. Positive current sensing is carried out by biasing a sense node of the sense FET to the ground voltage while negative current sensing is carried out by biasing the sense node of the sense FET to a voltage greater than the drain-to-source voltage of the low-side power FET. The sensed positive current and sensed negative current are combined to provide a monitor current output signal.

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