DRV8323: pros and cons of Bi-directional and Uni-directional mode for current sense

Hi Mahendra,

The bidirectional current sense configuration will sense both positive and negative currents that flow through the sense resistors. The reason there are negative currents through the sense resistor is due to current recirculating through the coils on the low side when the driver switches between driving one phase and driving the next. However to do this, the reference voltage is Vref/2, which may reduce the dynamic range of the amplifier. However, adjusting the gain of the amplifier and the value of the sense resistor should help to accommodate this. This brief app note explains how bidirectional current sensing is used in motor drive applications.

Unidirectional current sensing will only sense positive currents flowing through the sense resistor into ground. Any negative recirculating currents will make the SO output saturate at the Vref voltage. This might give you a better dynamic range, but you cannot sense negative currents.