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TCAN1043A-Q1: Pull Down on INH

Khai Nguyen
Intellectual 1295 points

Part Number: TCAN1043A-Q1

Tool/software:

Hi Team, 

when using a pull down resistor on INH with 4k7 it will stay low and after 44ms will be high again. When using 100k (a weaker pull down) this does not happen.

Is there an explanation for this?

Best 
Khai

  • 0
    TI__Mastermind 18612 points

    Hi Khai,

    INH is a high voltage output pin that is either drive high or high-impedance during Sleep mode. A 100K resistor pull down is recommended on INH for faster transition times from the high to low state since the pin is left floating in Sleep mode. 

    However, this resistor value should not directly affect the state machine of this device (causing INH to toggle). Something else is likely influencing this transceiver to wake up out of Sleep mode where the INH pin is driven high. 

    Best,

    Ethan

  • 0 in reply to Ethan Sempsrott
    TI__Intellectual 1295 points

    Hi Ethan, 

    as for my understanding exiting sleep mode can only be triggered with following conditions: WUP, LWU or low to high transition of nSTB. Is this correct ? 

    Also, we see this behaviour at high and low temperature with 4k7 pull down. Asked for more infos on temperature and conditions. 

    Any guesses what could be the root cause ? 

    Best 
    Khai

  • 0 in reply to Khai Nguyen
    TI__Mastermind 18612 points

    Hi Khai,

    Khai Nguyen said:
    as for my understanding exiting sleep mode can only be triggered with following conditions: WUP, LWU or low to high transition of nSTB. Is this correct ? 

    For exiting Sleep mode, the only thing I would add is if VSUP resets. If VSUP drops below 3.5V and rises back to a normal voltage (i.e. greater than 4.5V), then TCAN1043A will restart and enter Standby mode with INH high. 

    Please provide a schematic of the transceiver. 

    Please also have the customer measure a waveform with INH, nSTB, CANH, and RXD with both pulldown resistor configurations. Specifically when the INH pin on the 4.7K configuration goes from low to high.

    When a 4.7K pulldown is used, how does the customer initially send TCAN1043A into Sleep mode (i.e. is nSTB driven low to exit Normal mode)?

    Best,

    Ethan

  • 0 in reply to Ethan Sempsrott
    TI__Intellectual 1295 points

    Hi Ethan, 

    I looped you in the mail. Lets follow up via mail and close this thread. Will also additionally ask for the latest schematics. 

    Best
    Khai