JAJSME3B March 2022 – January 2023 UCC21737-Q1
PRODUCTION DATA
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, or even a fire hazard. In this case, the active short circuit (ASC) function is used to protect the system by forcing the output signal high, turning on the switch, and creating an active short circuit loop between the phases to bypass the battery. The timing diagram of ASC support with VCC UVLO, VDD UVLO, and OC fault are shown in GUID-A655F4CF-DE91-4C95-AF4D-199006A48D81.html#T6046196-2, GUID-A655F4CF-DE91-4C95-AF4D-199006A48D81.html#T6046196-3, and GUID-A655F4CF-DE91-4C95-AF4D-199006A48D81.html#T6046196-4.
The UCC21737-Q1 encodes the voltage signal VASC to a PWM signal, passing through the reinforced isolation barrier, and output to the APWM pin on the input side. Thus, the ASC pin status can be monitored. The PWM signal can either be transferred directly to the DSP/MCU to calculate the duty cycle, or filtered by a simple RC filter as an analog signal. The ASC input voltage varies from 0 V to 5 V, and the corresponding duty cycle of the APWM output ranges from 5% to 95% with a 400-kHz frequency.