This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TCAN1043A-Q1: TCAN1043A-Q1 nFAULT

Part Number: TCAN1043A-Q1
Other Parts Discussed in Thread: TCAN1043

Tool/software:

hi, 

I use TCAN1043ADMTRQ1 in my design , I  want the CAN trasciver to go to Sleeo Mode  as soon as possible, but not throgh the Normal Mode.

I power up Vsup(cold power on start up), VCC and and VIO are Powered normal , the TCAN1043 is in standby mode beacause both EN and nSTB are pull-down by 47K resistor .

then the MCU control its IO pin to this command "  EN = HIGH fistly and then nSTB =HIGH " to force the CAN IC to go to Normal mode .

I see the nFAULT becomes to High level after nSTB becomes high , but the delay time is about 600mS

when I control the CAN to sleep mode by command "nSTB =Low, keep EN=high" ,the CAN IC is in sleep mode , I can observe the nFAULT becomes to high-impendance . 

when I re-control nSTB=high, I mean the CAN transciver transition from Sleep mode to normal mode , the nFAULT is only 4uS delay after the nSTB rising edge.

my question is : 

why nFAULT is delay too much time to nSTB rising edge when the cold power on? 

  • sorry , please ignore this sentence.

     I use TCAN1043ADMTRQ1 in my design , I  want the CAN trasciver to go to Sleeo Mode  as soon as possible, but not throgh the Normal Mode.

  • please see the picture. 

  • Please see picture below,  another question is : if I keep EN high level and nSTB is only high for 50us , what  the nFAULT  behavior is ? thanks !

  • Hi Bin,

    Thank you for all the details you shared.

    Just a note, the fastest way to enter sleep mode regardless of the current mode is to either turn off VCC or VIO (or both). I have highlighted this below:

    For the nFault question, this delay you are seeing is likely due to the PWRON, WAKERQ, and WAKESR flags that are turned on due to the cold start. This allows the system to properly power everything on. Section 8.3.7.1 and Table 8-1 in the datasheet detail these conditions. These flags are cleared once the device enters Normal mode. That is why when you enter Normal mode from Sleep mode the next time, nFault time is smaller. 

    For your second question, assuming the device is previously in the Standby mode with no previous flags present, it will briefly enter Normal mode. Then the device will enter Sleep mode after time t_GOTOSLEEP. So nFault should be high while in Normal mode and then turn back to high-impedance once it enters Sleep mode.

    Best regards,

    Ethan