ZHCSH31B August 2017 – February 2018 DRV10987
When the DRV10987 device transitions from driving the motor into a high-impedance state, the inductive current in the motor windings continues to flow and the energy returns to the power supply through the intrinsic body diodes in the FET output stage (see Figure 40).
To prevent the inductive energy from being returned to the power supply, the DRV10987 system transitions from driving to a high-impedance state by first turning OFF the active high-side drivers, and turning ON all low-side drivers. The DRV10987 device monitors phase current after entering the BRAKE state and transitions into the high-impedance state when the amplitude of the phase current is less than BrkCurThrSel for a fixed period of time (BrkDoneThr[2:0])(see Figure 41).
In this example, current is applied to the motor through the high-side driver on phase U (S1) and returned through the low-side driver on phase W (S6). The high-side driver on phase U is turned OFF' and all low-side drivers are tunned ON to allow the inductive energy in the resulting LR circuit to decay. If BrkDoneThr[2:0] = 000, no brake is applied and the device does not protect from inductive energy even with the inductive AVS feature enabled.