I have a board designed that includes DRV8353RH where everything seems to work fine (buck regulator, VGLS, charge pump) until I pull high the ENABLE pin of the DRV8350. 745us after I pull the ENABLE pin HIGH I can see how the nFAULT pin goes LOW, even before I start sending any control PWM signal (all INLX, INH_X pins = LOW). No matter which PWM Mode I select, I always see the Fault pin to go LOW indicating a fault as soon as I pull the ENABLE pin HIGH (3V3).
Unfortunatelly this is not an SPI version of the chip, so I just have the nFAULT indication of something going wrong. I have reviewed all the possible fault conditions but I do not find the cause in my board:
1/ VM Undervoltage => My VM is 12V, which is well above 8.3V (VVM_UV), so this cannot be the cause
2/ VDRAIN Undervoltage => VDrain = VM = 12V, as VVDR_UV is 6V5 this is not the cause of the fault, too
3/ Charge Pump Undervoltage => VCP is 22V5 when I enable the board, well above 12V+5V = 17V, not the cause too
4/ VGLS Regulator => I measure VVGLS = 12V, above VVGLS_UV = 4.25V, not the cause
For the remaining causes of fault the PWM must be working, but as said I see the Fault before I start sending any PWM signal.
Do you have any recommendation on how can I proceed now to identify what is causing the FAULT?