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TCAN1043-Q1: TCAN1043xx-Q1 max. Vsup current

Alex L
Prodigy 210 points

Part Number: TCAN1043-Q1
Other Parts Discussed in Thread: TCAN1043A-Q1,

Dear all,

is TCAN1043xx-Q and TCAN1043A-Q maximum current drawn in Normal mode by Vsup pin (and hence also in Sleep and Standby modes) respectively 80 uA and 130 uA ?

Is the pin subject to any current transient which exceeds those values ? (e.g. during turn-on, etc.)

Best Regards

Alex

  • 0
    TI__Guru 74522 points

    Hi Alex,

    Yes, the VSUP pin current specifications are as specified, applying to steady-state operation in Normal, Standby, and Sleep modes. I.e., when the device fully enters the respective mode. During power-up and mode transitions, in-rush transients may occur different from the values. However, should not affect the average current consumption or device reliability, thanks.

    Best Regards,

    Michael.

  • 0
    Prodigy 210 points

    Hi Michael

    thank you very much.

    1) Therefore (considering steady state conditions):

     1.a) In Normal mode, Standby mode, Silent mode the Vsup current will see additionally the current drawn by INH port,
     since datasheet shows that INH port is connected to VSUP through an enabled PMOS.
     Therefore, tot. Isup current will be: Isup (max. 70uA TCAN1043-Q1/130 uA TCAN1043A-Q1) + I,INH.

     1.b) In sleep mode, only an Isup of max. 30mA flows through Vsup (INH PMOS is disabled).

     Are the above considerations (1.a and 1.b) correct?

    2) could you give me an estimation of max. Isup current (i.e. current which flows through Vsup pin)
     required to switch between the different operating modes (max. transient current e.g. from sleep to normal and vice-versa) ?

    3) Is a resistor on Vsup line (upstreams Vsup pin) advised or not ?
     If yes, what is its recommended value ? (some manufacturers state 1K as the optimal value) 

    Many thanks

    Alex

  • 0 in reply to Alex L
    TI__Guru 74522 points

    Hi Alex,

    1a) Please help note that the data sheet's spec should refer only to the transceivers internal consumption and INH should not be included in the spec. Hence, similiar to your statement, any additional load on INH may be added to the spec as needed.

    1b) In sleep mode, the INH PMOS should be disabled and should not contribute. Hence uA as specified.

    2) Unfortunately, this is dependent on the system / power supply used with the device as there isn't any specified max in-rush current spec. However, I have seen negligible current typically around < 1 mA range.

    3) Generally not recommended as it may delay internal bias startup / cause brownout during INH assertion or increase EMC concerns. Would rather recommend sufficient decoupling caps similar to the data sheet's layout example instead, and suspect the 1K example applies to an always-on logic IC, thanks.

    Best Regards,

    Michael.

  • 0 in reply to Michael Ikwuyum
    Prodigy 210 points

    Hi Michael

    regarding point no.3: the 1K is advised in an App. note of a well-known T*1043 manufacturer.
    It is placed upstreams the decoupling capacitor, of course.
    It is meant " for enhanced protection against automotive transient".

    Do you agree with that?
    Given the fact that our Vsup will never go below 18V, and the Undervoltage level on Vsup of 4.4V, the current for a brownout would be >10mA.
    As you mention, you only saw 1mA during transients (such as your answer on point no.2).

    Would it be safer to choose a decade lesser resistor (i.e. 100 Ohms) and thus a decade lesser filtering on Vsup?
    Or maybe we should consider enhancing decoupling caps (i.e. 1uF//100nF) and a decade or two lower resistor ? (i.e. 10 Ohms or 100 Ohms)
    Or do you advise working with no series resistor at all on Vsup ?

    Thank you very much

    Best regards

    Alex

  • +1 in reply to Alex L
    TI__Guru 74522 points

    Hi Alex,

    Please note that my feedback is for customer's specific concerns. Hence, customers may confirm if no concerns for their specific use case per any µs-scale voltage drops that may be observed during mode switching. However, would rather suggest 10 to 100 ohms to verify as needed (combined with the 1 uF || 100 nF decoupling caps), thanks.

    Best Regards,

    Michael.