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Original question:

TPS3813K33-EP: Watchdog reset issue at the time of flash and debugging

TPS3813K33-EP: Watchdog feature disable

Nilesh Karale
Prodigy 120 points
Part Number: TPS3813K33-EP
Other Parts Discussed in Thread: TPS3306, TPS3813, TMS320F28377D, TPS3823, TPS3820, TPS3851, TPS3850

Tool/software:

Hello,

I wanted to understand the behavior of watchdog feature. In my application I am pulling down WDI pin.

My question is, when we pull down WDI and if there is no rising edge at WDI pin then is this chip is in watchdog disable mode and only reset based on voltage?

As per below figure it is showed that till rising edge at WDI, output of chip is not asserted (reset is 1).

Thanks,

Nilesh

  • 0
    TI__Genius 9820 points

    Hi Nilesh, 

    According to datasheet, first WDI positive edge affects only lower boundary. Please find timing rules in below. 

    If you miss providing the positive edge before the watchdog timer ends, this will assert the RESET. 

    Depending on how you configure the WDT pin, you can either have 0.25 second or 2.5 second window timeout. 

    Hope this answer your question. 

    Best, 

    Sila 

  • 0 in reply to Sila Atalar
    Prodigy 120 points

    Hi Sila,

    Thank you for your reply and I understand that if no rising pulse at WDI pin within window timeout then it will assert reset.

    I have similar query regarding other watchdog chip TPS3306, as per datasheet it is mentioned that when WDI pin unconnected or connected to high impedance driver then watchdog is disable. I wanted to understand that if I connect this chip to TMS320F28377D microcontroller then what is the state of GPIO (connected to WDI pin) at very first time of programming or flash the code?  Also can you please confirm that this is the feature only available in TPS3306 and not in TPS3813.

  • 0 in reply to Nilesh Karale
    TI__Genius 9820 points

    Hi Nilesh, 

    As the datasheet highlighted, our some of supervisor can create internal WDI signal. And TPS3813 is not one of them. Please find the bench data I got for you in below. 

    WDI is not connected (left floating):

    WDI is connected to VDD:

    WDI is connected GND:

    Result: In all conditions, device is asserting due to WDI input signal is not applied on time. 

    Please check TPS3823, which is another supervisor with watchdog timer and,  if left floating or connected to a high impedance, the device generates pulses internally to prevent watchdog reset event.

    • I want to let you know that the watchdog timer can be disabled by disconnecting the WDI pin from the system. If the WDI pin detects a high-impedance state the TPS3820/3/4/8-xx-generates a WDI pulse to make sure that RESET does not assert.

    TPS3813 and TPS3823 are not p2p, if you are planning to change devices checking TPS3850/ TPS3851 might be also useful in your case since they have integrated WD_EN pin feature. You can disable the TPS3850/ TPS3851 by chancing SET0/SET1 pin(s).

    Hope this will be helpful!

    Best Regards,

    Sila