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TCAN1043A-Q1: About INH line processing

oaku.hiroshi
Prodigy 190 points

Part Number: TCAN1043A-Q1

Hi

Similar to the recommended circuit for TCAN1043A-Q1, we are considering a circuit that controls by connecting INH to EN of the regulator IC.

As for the recommended terminal treatment for the INH pin, we have placed 100kΩ, but looking at the data sheet "8.3.4 INH Pin", is it correct to understand that lowering the resistance value will work more advantageously? I have installed 47kΩ, but please let me know if there are any concerns (other than increased current consumption) with lowering it to less than 100kΩ.

  • +1
    TI__Guru 53535 points

    Hi Hiroshi-san,

    Thanks for bringing your question to E2E. 

    The INH output from the TCAN1043A is an open-source output referenced to the VSUP supply. When active, the open-source FET is active and the output drives to the VSUP potential. When the transceiver moves to Sleep mode, the INH output will be turned off into a high-impedance state. In order to allow the INH signal to fall to a low-state in a timely manner, it is recommended to place a pull-down resistor on the signal line. This will allow the capacitance of the signal line to discharge towards ground. Because the timing of this shutdown is not critical to most application, the value of this resistor is not typically of great concern. Therefore a relatively large value of 100k-ohms is used as an example such that the output will consume minimal current while active while providing sufficient leakage for a timely shutdown of the system. 

    I don't see any issue using a 47k-ohm pull-down value for this case. You will see slightly more nominal current from the VSUP supply during an active state (12V / 53k-ohm ~= 200uA). This will not impact the Sleep current consumption of the system. 

    Let me know if you have any more questions.

    Regards,
    Eric Schott