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TCAN1043-Q1: After power on, EN/nSTB = low/low. what state will it be?

Jimmy Gong
Expert 3600 points

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

Hi team,

Follow up tcan1043-Q1 state diagram below. when I power on the device will go to Standby Mode. at this time if EN / nSTB = low / low, what state will it be? 

As I know that If it is A-version at this state will start counting SWE timer then go to sleep mode.

the TCAN1043's function my customer expects is EN / nSTB = low / low for a while will from standby mode to sleep mode INH become high impendence. but as their experimental result INH is still on when they EN / nSTB = low / low. In addition, the reason don't replace 1043 with 1043A is ESD issue. 

BR,

Jimmy

  • 0
    TI__Guru 53535 points

    Hi Jimmy,

    Both the TCAN1043 and TCAN1043A treat initial power on of Vsup as a WAKE event and will set an internal wakerq flag. This flag will lock out the device from go-to-sleep mode so the EN and nSTB pin states will not be able to move the device to sleep mode and the device will remain in Standby mode until EN and nSTB drive the device to Normal or Silent modes or some fault causes a different mode change.

    For TCAN1043, the most common of these faults may be the UV timer for Vcc and/or Vio timing out. These timers are active immediately after initial power up and will put the device into sleep mode if the supplier are not enabled a few hundred ms after startup. By comparison, the TCAN1043A locks out these undervoltage timers until the supply has crossed the undervoltage threshold for first time since POR which gives the system more time to enable Vcc and Vio. Instead the TCAN1043A has to SWE timer that will automatically transition the device to does not enter normal mode after 4 minutes. 

    For all cases, if Vcc and Vio are supplied before the device times out into sleep mode, the EN and nSTB pins can be driven to move the transceiver into normal mode. 

    Let me know if you have any more questions. 

    Regards, 
    Eric Schott 

  • 0
    Intellectual 610 points

    Hi Eric,

    Our device is hanged on the battery directly

    We let the MCU cannot control the EN/STB pins intentionally, namely, the EN/STB pins are  always at low after power on (the power, VCC and VIO are good), 

    the pin, INH, will keep at high contiuously that will have a risk situation as follows,

    After power on, the MCU cannot boot normally owing to the software or flash device is not good but the power is good, the TCAN1043 will be always at standby moe that 

    keep the system power on continuously and the battery will have a risk to be exhausted

    Thanks

    Michael Su

  • 0 in reply to Michael Su
    TI__Guru 53535 points

    Hi Michael,

    This scenario is the reason why the SWE timer was implemented in the TCAN1043A. The TCAN1043 does not have any way to detect the case where the MCU is unresponsive after a good power on, so this will be a tradeoff for staying with the older device. 

    Regards, 
    Eric Schott 

  • 0 in reply to Eric Schott1
    Intellectual 610 points

    Hi Eric,

    Thanks for your reply

    The ESD tolerance of the TCAN1043A seems to be weaker than the TCAN1043, for our another project that used the TCAN1043A failed to ESD test, 

    replaced it with the TCAN1043, it passed the ESD test

    Thanks

    Michael Su

  • 0 in reply to Michael Su
    Intellectual 610 points

    Hi Eric,

    At this abnormal scenario, whether we can add the external resistor to let the TCAN1043 operate at GO-to-sleep mode, then enter into the sleep mode

    after power on  ?

    Thanks

    Michael Su

  • 0 in reply to Michael Su
    TI__Guru 74922 points

    Michael,

    That is one solution, and something we typically recommend if there will be a state where the MCU cannot control the EN and nSTB pins. At power-up, if the pull-up/pull-downs are populated correctly, the device will initially go into Standby mode then transition to sleep mode. Another way to do this is to not supply VIO and/or VCC so the undervoltage flag is tripped, and then the device will automatically go into sleep mode. Once VIO and VCC are supplied, the device can be transitioned to Standby mode through a wake event, and then the controller can transition the device into Normal mode.

    Regards,

    Eric Hackett 

  • 0 in reply to Eric Hackett
    Intellectual 610 points

    Hi Eric,

    We set the EN/STB=High/Low after power on, the TCAN1043 did not enter into the Go-to-sleep mode

    We check the datasheet, the standby mode changes to Go-to-sleep mode neeeds the following conditions:

    1. Set the EN/STB=High/Low

    2. WAKERQ cleared

    How to clear the WAKERQ after power on ?

    Thanks

    Michael Su

  • 0 in reply to Michael Su
    TI__Guru 53535 points

    Hi Michael,

    The WAKERQ flag is cleared when the device transitions to normal mode. The mode pins need to be driven to EN = nSTB = high before driving nSTB low to move to go-to-sleep mode. 

    Regards, 
    Eric Schott