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TPS3831: Short Circuit Protection on RESET Line

Jason Schepler
Prodigy 120 points
Part Number: TPS3831
Other Parts Discussed in Thread: TPS3760, TPS3779, TPS3704

Hi,

I know the TPS3831 says that the max recommended current is 8 mA, but is the device short-circuit protected? We have an application where the RESET output is at 3.3V from the push-circuitry of the TPS3831, but we need to make it go to a logic-level 0 without modifying the MR input.

So, if we short the TPS3831 RESET output to GND for ~200 ms, will any damage be done to the component?

Thanks.

  • 0
    TI__Genius 9820 points

    Hi Jason, 

    Thanks for your question.

    I would like to understand your use case little bit more. Can you please share a schematic of your situation, it's not fully clear on my side what is happening on the output?

    What we want to avoid is pull-up is high but something on the output is low, since this will cause a high current, this can be more than what the device support. 

    Best Regards,

    Sila 

  • 0 in reply to Sila Atalar
    Prodigy 120 points

    I have attached a simple schematic.

    We purchase an off-the-shelf SOM that has the CPU and Ethernet PHY. The RESET output of the TPS3831 is tied to the RST line of the Ethernet PHY, and also goes onto our custom board section via a connector.

    I can use DIGOUT to manually cause the the IC1 RST pin to go low, without causing the Ethernet PHY to reset.

    Now, I need to be able to reset the Ethernet PHY without resetting IC1.

    I think the only way I can do that is by causing the RESET output to go over its max current so the voltage drops out. I cannot use the MR pin, because that only goes low when the CPU reboots, and I don't want to reboot the CPU. Also, if MR does go low, I still want the RESET output to reset everything downstream of it.

    If I added logic like the following red box, then I can reset the Ethernet PHY without resetting IC1, but It would short the RESET line of the TPS3831 to ground. Is it safe to ground this pin for ~200 ms?

  • 0 in reply to Jason Schepler
    TI__Genius 9820 points

    Hi Jason,

    Thank you for your detail explanation on your system requirements.

    I think there are two solutions. First one adding another switch that  removes RESET output from the ground, which can protect the TPS3831 is  since the RESET output will be floating when you need to reset ETHERNET PHY. 

    The other solution is that we have 2 channels devices with separate RESET outputs, such as TPS3704, TPS3760, TPS3779, you can assert the reset depending on your requirements. 

    I can assist you more on which supervisor would be better if you interested and can provide more details what voltage is needed for the rail, reset timing requirement, and functional safety is required or not? 

    I hope this helps!

    Best, 

    Sila