When VCC loses power, or the MCU is malfunctioning, the motor can lose control and reversely charge the battery. Overvoltage of the battery can cause battery break down and can even be a fire hazard. For this scenario, the active short circuit (ASC) function can be used to protect the system by forcing the output on, turning on the power switch, and creating an active short circuit loop between the motor phases to bypass the battery.

When the ASC pin receives a logic high signal, the output is forced on regardless of the input side pin conditions. The ASC function has higher priority than the input signals and VCC UVLO. VDD UVLO, desaturation fault, and overtemperature protection have higher priority than ASC. The ASC_FB pin will output a logic high signal to indicate the ASC function is active when the ASC pin input voltage is high, the output is turned on due to the ASC input, and VCC is not in UVLO. Timing diagrams of ASC support with VCC UVLO, VDD UVLO and DESAT are shown in Figure 6-11, Figure 6-12 and Figure 6-13.

Figure 6-11 ASC Support with VCC UVLO

Figure 6-12 ASC Support with VDD UVLO

Figure 6-13 ASC Support with DESAT Fault