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TCAN11625-Q1: The SLP cannot be raised, causing the system to keep shutting down and restarting

Vayne Li
Expert 2130 points

Part Number: TCAN11625-Q1

Hi Teams,

My customer specializes in car key positioning products and has been using the TCAN11625-Q1 product for the past year.

They encountered SLP not pulling high, causing the system to keep shutting down and restarting. They would like to know the reason.

This SLP pulse sends a command to the MCU to reset and then pull it high. If the action of resetting and pulling up the SLP is not performed, the SLP will always be at a low level.

image.png

image.png

9ms is active reset, and the blue wire is self reset for pin 11625.

image.png

This is the unfolded waveform, with SLP decreasing first, then approximately 27us followed by RST, and finally 20us followed by INH.

Now it has been found that during the MCU soft reset, the SLP inexplicably pulls down (which may be normal, as the microcontroller has not yet started up, but the SLP of TCAN11625 defaults to pulling down). The problem is that after the SLP pulls down, the RST is also pulled down internally, causing the INH to pull down and the system to not power on.

This test was conducted by disconnecting RST and MCU, but the system still couldn't start, proving that the root cause is still SLP. Can you help me find a solution.thank you.

  • 0
    Expert 2130 points

    Supplementary testing
    When SLP drops to 1.4V, Inh drops, which is a big problem for applications. Try adjusting the pull-up and pull-down resistors, there are two situations
    1. Either the SLP can only be pulled up, or pulled down a little bit;
    2. Either it can only be pulled down, and if it is pulled up, it will immediately fall down again (the waveform in the previous case corresponds to the second situation where it can only be pulled down)

  • 0 in reply to Vayne Li
    TI__Mastermind 32010 points

    Hi Vayne,

    Those waveforms make sense, nSLP pulled low from high to enter sleep mode, thus INH and nRST are turned off.

    For a MCU reset they need to externally pulled nRST low to enter reset mode, which will not turn off INH.

    Regards,

    Sean

  • 0 in reply to Sean Guo
    Expert 2130 points

    Hi Sean,

    Thank you for your reply,

    Can the NSLP foot be pulled up?

  • +1 in reply to Vayne Li
    TI__Mastermind 32010 points

    Hi Vayne,

    nSLP is integrated pulled down, so if your MCU lose the control of nSLP, it will be pulled low.

    Your MCU need to externally pull nSLP to high to enter (or remain in) normal mode. 

    Regards,

    Sean