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TLIN1021A-Q1: VSUP current in sleep mode

Shohei Kosaka
Prodigy 20 points
Part Number: TLIN1021A-Q1

Tool/software:

Hello Experts,

I am experiencing an increase in the VSUP current when the LIN transceiver is in sleep mode (EN = LOW).

What is the cause of the increase in current?

The detailed situation is as follows.

Circuit configuration: See Figure 1.

Voltage/current waveforms: When the pull-up voltage of the TXD terminal decreases and 2.5V is applied to the TXD terminal, the VSUP current increases. (See Figure 2)

<Figure 1> Circuit Configration

<Figure 2> Voltage/current waveforms

  • 0
    TI__Mastermind 28310 points

    Hi Shohei,

    If you disconnect TXD from MCU and let it left it floating in sleep, would you still see that 0.5mA ISUP? Their would be some current consumption across the internal 350 kOhms pull-down resistor if TXD is pulled up to 5V which drops slowly.

    Regards,

    Sean

  • 0 in reply to Sean Guo
    Prodigy 20 points

    Hi Sean,

    Thank you for your answer.
    ISUP also becomes 0.5mA when going to sleep with TXD disconnected from the MCU.

    Also, with the TXD terminal and MCU disconnected, if you supply 5V to TXD pull-up from an external stabilized power supply,
    and gradually lower the 5V, the ISUP current suddenly increases at around 2.5V.

    We speculate that a shoot-through current is generated when an intermediate potential is applied to the TXD terminal's internal circuit (Dominant State Time-Out).

    Could you please tell me the configuration of the TXD terminal's internal circuit?

    Regards,

  • 0 in reply to Sean Guo
    Prodigy 20 points

    Hi Sean,

    I have sent additional questions so could you please answer them?

    Regards,

    Shohei

  • +1 in reply to Shohei Kosaka
    TI__Mastermind 26806 points

    Shohei-san,

    My apologies for the delay here.

    Yes, if you hold the TXD input to a midrail voltage, it is possible to see increased current consumption due to shoot-through current, as you mention. The specification for the device ISUP in Sleep mode is based upon TXD and RXD floating, so it's possible to have slightly increased current consumption if the TXD pin is biased to midrail.

    TXD has an internal weak pull-down, so it should bring the pin to LOW when nothing is connected. If you remove the pull-up resistor, you should see that this is the case.

    Best,

    Danny

  • 0 in reply to Danny Bacic
    Prodigy 20 points

    Hi Danny,

    Thank you for your reply.
    I have one more question, so please answer it.

    I understand that a shoot-through current occurs when the 5V input to the TXD terminal.
    Will the LIN transceiver be damaged by this shoot-through current?

    Please let me know if there is a maximum rated current for the VSUP terminal.

    Regards,

    Shohei

  • +1 in reply to Shohei Kosaka
    TI__Mastermind 26806 points

    Shohei-san,

    Good question. No, there should not be an issue of damage in this situation, the main concern is just the increased current draw from your battery line.

    Best,

    Danny

  • 0 in reply to Danny Bacic
    Prodigy 20 points

    Hi Danny,

    Thank you for answering my additional questions.
    All my questions have been answered.
    Your assistance is very much appreciated.
    Thanks again.

    Regards,

    Shohei