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TPS3828 question.

T Kishi
Genius 4425 points
Other Parts Discussed in Thread: TPS3828, TPS3838, TPS3824, TPS3852, TPS3851, TPS3850

Hi

My customer has questions . Please cooperate me.

1. For "Ttout" and "Td"

    Ta = -40 ℃ Is there a max / min values of ~ 85 ℃ conditions?

2.If the WDI pin pulled up with 5kΩ, have a problem? Also, have the provisions of the Pullup resistance?

3.For "Table 1. Function Table"

　In the case of TPS3828,
　MR=H, VDD>VIT=0,/RESET=L
　MR=H, VDD>VIT=0,/RESET=OPEN
　Is no problem in recognition？

4.Specified value of "output current" of Open-Drain output are located in other than the Absolute maximum rating?

Best Regard

T Kishi

  • 0
    TI__Mastermind 44620 points

    HI Kishi-san,

    For Question #1; In our datasheets, any value in the Electrical Characteristics table where there is a minimum or maximum value, that value is guaranteed over the full operating temperature range.

    For Question #2; The TPS3828 Detects either a rising or falling edge to reset the timer. If left floating the TPS3838 disables the Watchdog. I think the real concern for the pull-up value (assuming you are using an open-drain GPIO to drive this) would be the sink capability of whatever is going to be pulling it low.

    For Question #3; the table has two columns for the reset output. the second column is the inverted output of the TPS3824/5

    For Question #4; the datasheet shows a VOL threshold of 0.4V with a pull-down current of 1.2mA. I think figure 5, gives the best idea as to how to decide on a pull-up resistor value based on the pull-up voltage: So if you select 5mA with VDD=2.66V, at 85C, the VOL can only reach 1.5V. See below:

    I think it is better to make sure the VOL is <0.4V.

    By the way we do have a much newer Watchdog family of devices. The TPS3850, TPS3851, and TPS3852 are a much more flexible watchdog timer series.

  • 0 in reply to JCHK
    Genius 4425 points
    Hi John
    Thank you for reply.

    We understand the #1 and #2.

    For Question #3:The Do you have a table add TPS3828?

    For Question #4:Does this graph also applies if the Open-Drain output?

    Best Regard

    T Kishi
  • 0 in reply to T Kishi
    TI__Mastermind 44620 points

    HI Kishi-san,

    I agree that it is confusing when we try to put multiple parts on the same datasheet.

    To clarify question #3, maybe this can help.

    As for question #4, this is describing our open-drain Reset outputs VOL Characteristics. The WDI pin is an edge sensitive input. If this is not clear, maybe I am not properly understanding your question.

    Please let me know if this helps.

  • 0 in reply to JCHK
    Genius 4425 points

    Hi John

    Sorry in the frequent question.

    For TPS3828 [Auto Reset Oscillator].

    This work if WDI is "OPEN",On behalf of the external signal is a function of input signals to the [Transition Detector].

    Is no problem in recognition?

    I want to make sure that it does not malfunction even if the Pullup the WDI pin in 5kΩ.

    Best Regard

  • 0 in reply to T Kishi
    TI__Guru 55940 points
    Hi Kishi-san,

    From a system level, floating the watchdog will be disabled when WDI is floated because the watchdog will not generate an external RESET event. Internally the watchdog will still be running, but the internal oscillator will reinitialize the watchdog timer. If you pull WDI high, the watchdog timer will not be reinitialized causing the watchdog to time out and generate a RESET event on the output.

    Very Respectfully,
    Ryan