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TCAN1145-Q1: The abnormal INH signal

Zoey Wu
Expert 5210 points
Part Number: TCAN1145-Q1

Hi expert,

 my customer is using TCAN1145 and they have questions as below. Could u kindly help to give some advise?

when they only supply VSUP with 12V and VIO/VCC stays at 0V at the same time, INH will be pulled high to 12V and will last for 3 minutes.

1. Is the signal of INH normal at this setting?

2. the pulled high signal of INH will lead to high current of about 115uA in 12V. do u have any advise of decrease the current in VSUP? 

  • 0
    Prodigy 40 points

    When an undervoltage occurs on VCC or VIO, the device transitions into either fail-safe mode or sleep mode as described in data sheet section 10.4.7.6.1 UVSUP, UVCC.

    Why fail-safe mode OR sleep mode? Can we make it  into  sleep mode all the time?

  • 0 in reply to Yongfeng Zhang
    TI__Guru 73052 points

    Yongfeng,

    Thanks for bringing this to E2E.

    Zoey Wu said:
    1. Is the signal of INH normal at this setting?

    Yes, INH is meant to be pulled up to battery voltage when it is enabled. The 3 minute timer is the SWE timer listed in the datasheet, once this elapses the device goes into sleep mode and INH is disabled.

    Zoey Wu said:
    2. the pulled high signal of INH will lead to high current of about 115uA in 12V. do u have any advise of decrease the current in VSUP? 

    The 15k resistor to GND on the INH pin is likely the reason. The customer can remove this because there is already an internal pull-down to help discharge the INH voltage once it is disabled and put into a high-impedance state.

    Yongfeng Zhang said:
    Why fail-safe mode OR sleep mode? Can we make it  into  sleep mode all the time?

    The device will only go into Failsafe mode if it is enabled in the SPI registers. Otherwise, it will go into Sleep mode.

    For all of these questions and more information, the datasheet can be referenced.

    Regards,

    Eric Hackett