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TPS2560: TPS2560 OUTx pin

Part Number: TPS2560
Other Parts Discussed in Thread: TPS2556, , TPS2561, TSD05C

Hi TI experts,

I have two questions:

1. For low current efuse like TPS2560/61 or TPS2556, does it need a Schottky diode from OUT pin to GND to protect the device during short circuit condition? if a diode is required, any guide on calculate/select the diode?

2. For below OUTx pin absolute max voltage ratings -0.8V from TPS2560 datasheet, is it for continuous DC voltage or a short voltage pulse? If it's a pulse, what's the time duration for this pulse? Thanks.

Thanks

Neo

  • Hi Neo, regarding your questions:

    1- Not required. The devices in question will current limit in case of a short. During the current limit operation if the device exceeds its shutdown temperature, the switch will turn off until it cools and then retry.

    2- This is for any condition pulsed or static. However, extended time under abs max conditions may affect device reliability (see note 1 in the table you reference). There is no timing spec on max time, but in general abs max conditions should be avoided if possible and if not should be momentary not static. These are the max levels that the device is built to withstand - but not continuous operational levels --> the "Recommended Operation Conditions" are the intended continuous parameters to ensure expected device reliability.

    Hope this helps to clarify, thanks,

    Zack

  • Hi Zack,

    Here is a waveform we captured when we "hot" short the OUT pin to GND for TPS2561 device. We observed the negative voltage on OUT pin is over -0.8V for 5us, but the TPS2561 device was not damaged. Is there still some tolerance on -0.8V abs max voltage? say more negative voltage is acceptable as long as the time duration is short enough. Can you please clarify? Is there any concern with this? There was no Schottky diode on OUT pin during testing.

    Thanks

  • "Hot" short means shorting the OUT to GND instantaneously when TPS2561 is under normal operation.

  • Hi Neo, I see. I believe that there is some tolerance beyond the abs max so not too surprised the device is working after the pulse. However, from a device specification, the abs max is the official limit and any operation beyond these levels may cause damage or reduce lifetime of the product. Can you provide more detail regarding how the test is performed? E.g. how long is the connection on the OUT and how/where is the short introduced?

    Also, can you share a schematic of the circuitry specific to the TPS2561? What is the configured Ilim in your design?

    Thank you - Zack

  • Hi Zack,

    Here is the schematic.

    The short point is red cycled location with short wires (10-15cm) to Ground. Voltage near OUT1 pin was captured with negative voltage >-0.8V for about 5us.

    Thanks

    Neo

  • Hi Neo, thank you for sharing the sch. Let me review and discuss internally - will followup in the next day. - Zack

  • Hi Zack,

    Any update on this topic?

    Thanks

    Neo

  • Hi Zack,

    Is there any conclusion after your internally discussion? Is a Schottky diode is required?

    Thanks

    Neo

  • Hi Neo,

    Sorry for the long response time.

    From what I see, the negative surge condition that you are experiencing is likely causing some well break down in the power switch, even though it is short duration and will require an external schottky diode to protect the device in this condition.

    Regards,

    Chuck

  • Hi Neo,

    You may want to look at the TSD05C https://www.ti.com/lit/ds/symlink/tsd05c.pdf.

    This part will protect for short fast surge voltage events better than a schottky.  I am not an expert in this part, so you can refer to that team for more support on it's application.

    Regards,
    Chuck