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TPS2117: short circuit protection for tps2117

Hossam Moghrabi
Intellectual 310 points
Part Number: TPS2117
Other Parts Discussed in Thread: TPS564247, , TPS25925, TPS2597, TPS2595

Tool/software:

hello,

i have this ic after 2 buck regulators, both dcap3 and have over-current protection. 

i want to know how does this circuit deal with over current or short circuit? like when a short circuit happens, assuming no protection from previous stages, what will happen to this ic?

regards, 

  • 0
    TI__Guru 70460 points

    Hi Hossam,

    This chip will not offer short circuit protection. It might get damaged if no short protection in power path. You can use a eFuse before it for short circuit protection.

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Intellectual 310 points

    hello,

    before it there is a buck regulator which is tps564247 with max of 4 amps current rated. it could be a bit more than 4 amps when over current protection kicks in so kindly check how much can tps2117 tolerate.

    what about its thermal shutdown? isn't it related to protection?

    also, if it had say 6 amps, what could happen?

    adding efuse now will be costly and actually there is no space left to use in the board. i could maybe squeeze in a resettable fuse but at which current i should have it?

    regards, 

  • 0 in reply to Hossam Moghrabi
    TI__Guru 70460 points

    Thermal protection might not always protect from fast rising load currents.

    Device can tolerate 6.5A for 1ms. 4A is DC rating.

    Buck should be able to protect.

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Intellectual 310 points

    hello,

    so if it had continuous 4.5 amps or so it will get damaged?

    i can add TPS25925 efuse just before the switching circuit, please check it and confirm if it is good enough. could be made to trip at 3.7-3.9 amps instead of full 4 amps to make sure all go nice.

    ^ this is for my 3.3v rail.

    for 5v rail, it is actually connected to one output pin directly without switching, and connected to tps2117 which its output is connected to the other output pin. therefore, when user picks 5v on tps2117 it will get delivered to the output pin while it is also available on the other output pin.

    having 6 amps as absolute max the buck can deliver, will it be safe without an efuse? meaning it could divide 6 amps between the 2 pins so that max of 3 amps goes through the tps2117... but it is not that safe in my opinion.

    i will try to make a dedicated efuse for the 5v input as well. just please check the suggested efuse and advise. i need it to be very cheap and easy to use.

    thanks

  • 0 in reply to Hossam Moghrabi
    TI__Guru 70460 points

    Hi Hossam,

    Yes continuous 4.5A can cause damage . 

    Yes TPS25925 should be fine. You can check latest devices like TPS2595, TPS2597 also. 

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Intellectual 310 points

    hello,

    yesterday i tried my device and it damaged tps2117 (smoked out) on 3.3v rail even under 4 amps. now only the 2nd route of the ic is still valid but when running some current, it causes big voltage drop. like at 2 amps from 5v to about 4.7v.

    is there any better device which can have more tolerance to high currents + protection?

    thanks 

  • 0 in reply to Hossam Moghrabi
    TI__Guru 70460 points

    Hi Hossam,

    What was the test case under which it got damaged? 

    TPS2117 is the max current device we have for PMUX. 

    Regards

    Kunal Goel