The active short circuit (ASC) function allows the system to force the state of the power transistor regardless of the PWM input. The ASC interface is located on both the primary and secondary sides, depending on the architecture of the safety controller. For cases where the main MCU is not available due to fault or otherwise, a secondary control circuit drives the ASC_EN input high to force the output of the UCC5870-Q1 to the state defined by the ASC input, denoted as the HV Controller in Figure 3-24.

From system point of view, the implementation of ASC function is to control the inverter output to be a zero vector. The zero vector can be generated through two approaches: Main MCU or secondary control circuit. The ASC function is usually triggered when there is a system fault. If the fault is not a MCU fault, the MCU can implement diagnosis through the SPI interface and generate the appropriate zero vector based on fault type. If the fault happens in the MCU, then the secondary control circuit pulls the ASC_EN pin to be HIGH and suitable state on the ASC pin. With the ASC_EN pin pulled high, the driver output follows the state on the ASC pin. For the primary side, two dedicated inputs are available for the ASC control. The ASC control is also available on the secondary side using the AI5 and AI6 inputs. The driver is configured with the secondary ASC function using SPI. In this configuration, AI5 works as ASC_EN and AI6 is the ASC input. The primary and secondary ASC interfaces are shown in Figure 3-24.

Figure 3-24 ASC primary and secondary side interfaces