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TPS3813: How to use TPS3813 to detect MCU is work or not?

Jimmy WANG
Genius 4085 points
Part Number: TPS3813
Other Parts Discussed in Thread: TPS3851, , TPS35, TPS3705, TPS3435, TPS3899

Tool/software:

Hi team,

Can I use a PWM signal from MCU into WDI of TPS3818 and if the PWM is gone then RESET from High to low? thanks 

I hope green is PWM and yellow is TPS3818's RESET pin. Can it achieve? 

  • 0
    TI__Mastermind 18121 points

    Our team will respond shortly. Thank you. 

  • +1
    TI__Mastermind 19100 points

    Hi Jimmy,

    Since the TPS3813 is a window watchdog, if the rising edge of the PWM falls in the lower boundary window, it will assert a RESET as well as well. If the fault that you want to detect is the PWM stop functioning, I would recommend using a timeout watchdog, such as TPS35 or TPS3851 for example.

    If the PWM signal is design as such that a rising edge will not fall in the lower boundary of the window, the TPS3813 can be used. 

    Jesse 

  • 0 in reply to Jesse Villanueva
    Genius 4085 points

    Hi Jesse,

    Understood. thanks 

  • 0 in reply to Jesse Villanueva
    Genius 4085 points

    Hi team,

    Can TPS3813 RESET output latch low when PWM stop? 

  • 0 in reply to Jimmy WANG
    TI__Mastermind 19100 points

    Hi Jimmy,

    Unfortunately the TPS3813 does not provide Latched output personality. Currently we only have the devices below with a latched output.

    Another latched output device we have is the TPS3705. It is not explicitly mentioned on the datasheet but behaviorally it has a latched output.

    Jesse  

  • 0 in reply to Jesse Villanueva
    Genius 4085 points

    Hi team,

    Does the TPS3435JAJAJDSER support Latched output?

    After PWM to WDI is stopped for 10ms.

    The part number shows WD Timeout is 1.4S. But does the second picture mean that it can be set to 10ms or 1.28S?

  • 0 in reply to Jimmy WANG
    TI__Mastermind 19100 points

    Hi Jimmy,

    On the table below, I have highlighted the devices we have currently released and available in TI.com with the latched output.

    The TPS3435JAJAJDSER is currently not released.

    As for your timing question, the time on the WD timeout column is going to be the base timeout of the device or when the time scaling is set to 1x.

    For example TPS3435CAGBJDDFRQ1, when SET[1:0]=00, timeout is set to 100ms, and when SET[1:0]=11, timeout is set to 800ms.

    Jesse 

  • 0 in reply to Jesse Villanueva
    Genius 4085 points

    Hi team,

    I'm looking for a RESET IC.
    When powered on, the output cannot be high.
    When a PWM input signal is detected, the output signal is high (frequency 10K).
    But when PWM is stopped (high or low), the output signal is low.

    Which one can meet? thanks 

  • 0 in reply to Jimmy WANG
    TI__Mastermind 19100 points

    Hi Jimmy

    Unfortunately for standalone watchdog devices, the first frame of the timer has to be started at a good state. Meaning the device will go HIGH at startup then go latch LOW when no pulse is detected. For a watchdog + supervisor device, the RESET will stay low until the VDD goes above the supervisor threshold. This behavior can be taken advantage by limiting the VDD of the device below its threshold then pump it up above the threshold when the PWM is ready. The highlighted device below can be worked around to accomplish this.

    Jesse 

  • 0 in reply to Jesse Villanueva
    Genius 4085 points

    Hi team,

    The application cannot meet the requirement. PWM signal work after VDD is built up.

    So do you have a solution that can support this requirement? 

  • 0 in reply to Jimmy WANG
    TI__Mastermind 19100 points

    Hi Jimmy,

    The best we can do is offer a two device solution. I have the schematic and timing diagram below.

    The down side is that the RESET output is not going to go HIGH for Twd time after the first falling edge of the PWM is detected. 

    TPS3899DL01DSER is recommended for the TPS3899. The TPS3435 is based on the timing requirement. 

     Jesse