TIDUDS9B December 2017 – November 2022
The MCU interface periodically sends 200-µs pulses MCU_Diag_Ctrl_Out2 with logic low for diagnostic purposes. The output of the switch is connected to the general-purpose input/outputs (GPIOS) of the MCU (Monitor_2), as Figure 2-4 shows by using a resistor divide network. And also connect to the STO_FB subsystem as STO_2_FB input.
The gate driver does not power off during these periodic pulses. This reference design uses a 20-µF capacitor to hold the 24-V secondary supply voltage. The TPS27S100 switch provides full diagnostics by accurately monitoring the output current. The output current is translated into volume, which is then fed back to the MCU, this feature enables intelligent control of the load. 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 turn disables the six gate drivers, the six IGBT will be turned off and the drive will enter the safe state.
Moreover, STO_2_FB is an active low signal and indicates the load switch state which works with the other channel STO_1_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.