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TCAN1043A-Q1: TCAN1043AVDRBRQ1

Anamika Pisharody
Prodigy 70 points
Part Number: TCAN1043A-Q1


Tool/software:

I have noticed that my RX line , ERR pin , Stb , EN and everything goes low when I send my txr to sleep : Isn't my RXD line supposed to stay recessive : 3.3V ?
In the Image below , CAN_Wake signal is taken across INH pin. It is connected to the enable pin of my HV Buck , so whenever I send a WUP over bus , INH pin will go high , and enable the buck .
When I send a command to bus , I can see my INH going high , but my ERR pin is also high , Rxd , which is already low is after a really long time , is mirroring the bus .

What am I doing wrong ? 


  • +1
    TI__Genius 17152 points

    Hi Anamika,

    Thanks for reaching out on E2E.

    Anamika Pisharody said:
    I have noticed that my RX line , ERR pin , Stb , EN and everything goes low when I send my txr to sleep

    Just a note here, TCAN1043A does not control EN and nSTB, rather your MCU is responsible for this. What mechanism are you using to enter Sleep mode?

    Anamika Pisharody said:
    Isn't my RXD line supposed to stay recessive : 3.3V ?

    RXD is dependent on VSUP and VIO while in Sleep mode. If the INH pin is tied to your VIO supply, then when INH goes low, VIO will also go low.

    Anamika Pisharody said:
    When I send a command to bus , I can see my INH going high , but my ERR pin is also high , Rxd , which is already low is after a really long time , is mirroring the bus .

    Based on that waveform, nFault is behaving as expected, and nothing is out of the ordinary here. Please reference the state machine in the datasheet (Figure 7-4) and the nFault table (Table 7-1). The wake-up request (WAKERQ) and wake-up source (WAKESR) flags are being signaled to nFault and RXD. 

    We know the transceiver is initially in Sleep mode because INH=0V. We can see that the transceiver changes to Standby mode because INH=high, RXD=low, and nFault=low. Once nFault goes high, this means the transceiver is in Normal mode (which is due to the MCU switching EN=nSTB=high), and it is ready to begin receiving/transmitting to the CAN bus. As such, it can be seen that RXD starts reading the CAN bus at that time.

    Please let me know if you need any further explanation or if you have additional questions!

    -Ethan