JAJU459B December 2017 – November 2022
For diagnostic purposes, the MCU interface periodically sends 200-µs pulses MCU_Diag_Ctrl_Out1 with logic low. The output of the switch is connected to the GPIOs of the MCU (Monitor_1) and the STO_FB subsystem as STO_1_FB input, as Figure 2-3 shows.
The gate driver not power off during these periodic pulses. A 0.47-µF capacitor is used to hold the 3.3-V primary supply voltage. Monitor_1 represents the status of the TPS22919 switch which is fed back to the MCU. If a short or stuck high was found, the MCU puts the 3-phase IGBT inverter into a safe state by driving both diagnostic pulses MCU_Diag_Ctrl_Out1 and MCU_Diag_Ctrl_Out2 continuously low. This in turns will disable the six gate drivers, the six IGBT will be turned off and the drive will enter the safe state.
Moreover, STO_1_FB is an active low signal and indicates the load switch state which works with the other channel STO_2_FB together to indicate the drive state. This state can be used for example by an external safety PLC to recognize a single fault in either STO_1 or STO_2 systems and take appropriate actions. The safety PLC and related action are out of scope for this reference design.