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TCAN4551-Q1: Questions regarding nWKRQ

Kei Kuwahara
Expert 4870 points
Part Number: TCAN4551-Q1

Hello team,

My customer has 4 questions on the nWKRQ pin.

1. Is there any timing chart when 16'h0800[8] = 1? On the datasheet, it seems that the timing chart represents when 16'h0800[8] = 0 as the nWKRQ is related to INH state.

2. Is it going to be asserted to LOW when wake event is occured?

3. Is my understanding below about 16'h0800[19] correct?

    0 = nWKRQ is going to be operated by internal 3.6V rail with push-pull output.

    1 = nWKRQ is going to be operated by external VIO voltage with Open drain output.

    

4. Is internal 3.6V going to be active, under consdition of VSUP: ON and VIO: OFF? The customer is planning to use nWKRQ as the WAKE signal with VIO.

Best Regards,

Kei Kuwahara

  • 0
    TI__Mastermind 49975 points

    Hi Kei,

    Kei Kuwahara said:
    1. Is there any timing chart when 16'h0800[8] = 1? On the datasheet, it seems that the timing chart represents when 16'h0800[8] = 0 as the nWKRQ is related to INH state.

    No. The nWKRQ pin when configured as a wake request interrupt will indicate the status of the unmasked CANINT, LWU and WKERR interrupts. These interrupts become active immediately upon the receiving of the wake and will be indicated by the pin by an active low. 

    Kei Kuwahara said:
    2. Is it going to be asserted to LOW when wake event is occured?

    Yes, this pin will be driven low when any of the unmasked CANINT, LWU and WKERR interrupts are set. 

    Kei Kuwahara said:
    3. Is my understanding below about 16'h0800[19] correct?

    Yes, your description is correct. Please ensure an external pull up to Vio is used for nWKRQ_VOLTAGE = 1.

    Kei Kuwahara said:
    4. Is internal 3.6V going to be active, under consdition of VSUP: ON and VIO: OFF? The customer is planning to use nWKRQ as the WAKE signal with VIO.

    The internal 3.6V rail for the digital core is active for all modes where Vsup > UVsup. This includes modes where the Vio rail may be disabled. However, the pin will still depend on an external rail to pull the pin to a high state as it is an open-drain output. [EDIT]: This is only true when configured for use with Vio. nWKRQ is push-pull when using the internal 3.6V rail.

    Regards, 
    Eric Schott 

  • 0 in reply to Eric Schott1
    TI__Expert 4870 points

    Hi Eric-san,

    Thank you for your detailed answer.

    I have additional question on Question 4.

    Eric Schott1 said:
    The internal 3.6V rail for the digital core is active for all modes where Vsup > UVsup. This includes modes where the Vio rail may be disabled. However, the pin will still depend on an external rail to pull the pin to a high state as it is an open-drain output. 

    Do you mean push-pull output here? On the datasheet Note for table 14, says that nWKRQ pin is configured push-pull when based on internal voltage rail.

    Best Regards,

    Kei Kuwahara

  • 0 in reply to Kei Kuwahara
    TI__Mastermind 49975 points

    Hi Kei,

    Sorry for the wrong information. You are correct. The nWKRQ pin operates as push-pull when configured to use the internal 3.6V rail. It only operates as open-drain when configured for use with Vio. 

    Regards, 
    Eric Schott