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TPS2421-1: ISET Resistor

Ian Davis20
Prodigy 190 points
Part Number: TPS2421-1
Other Parts Discussed in Thread: TPS2596, TPS2595

Hi,

Following on from a previous question raised on the support Forum "ISET PIN resistance setting range"

What is the impact if a resistor higher than 200k is used for RRSET?

I have tested with 247k on the bench and all is working well and as expected across many devices, so I haven't seen any negative impact but I want to understand if there are any limitations.

As a side note can you suggest an alternative device that has a lower quiescent current .  TPS2421-1 has a TYP 3.9mA bias current when EN = 0. We are only interested in the current limit, and latch feature of the device.

Best Regards

Ian

  • 0
    TI__Guru 57737 points

    Hi Ian,

    Using higher value of Rrset than 200kohms can set the fault current threshold to a value lower than 1A (typ) and the device can work normally. The difference is that as we have not characterized the device  for Rrset > 200kohms, we cannot guarantee the variation in the fault current threshold that can be expected with Process, Voltage and Temperature variations.

    You can have a look at TPS2595 or TPS2596 family of deices. These devices are our latest products and are much better in size, cost and performance compared to TPS2421-1. Do let us know if these devices suit your requirement.  

     

     

  • 0 in reply to Praveen GD
    TI__Guru 57737 points

    Hi Ian,

    Hope your queries are answered. Please let us know if you have more questions. 

  • 0 in reply to Praveen GD
    Prodigy 190 points

    Hi Praveen,

    I did look at both these devices, but the way we are currently using the TPS2421 device, we expect a FLT condition when we get an overcurrent / short-circuit event and for the power to be latched off until we re-try by toggling the EN line.

    Looking at TPS2595 and TPS2596, they both only provide a FLT condition during an Over-voltage or over-temperature events. 

    Do you know of any other device that will provide us with a FLT condition during an over-current event?

    Thanks

    Ian

  • 0 in reply to Ian Davis20
    TI__Guru 57737 points

    Hi Ian,

    Most of our efuse devices including TPS2595 and TPS2596 assert a fault after thermal shutdown due to over current event. 

    In our next generation of devices we are considering to assert a fault when the device is in current limiting mode.

    Can you let us know your project timelines ? I can let you know if we can come up with our next generation device within your required timeline.

  • 0 in reply to Praveen GD
    TI__Guru 57737 points

    Hi Ian,

    Can you please let us know by when you need the part. I can let you know if we can come up with our next generation device within your required timeline.

  • 0 in reply to Praveen GD
    Prodigy 190 points

    Hi Praveen,

    We need a suitable part to be in production now really.

    We had to adjust the current limit during development and are using the TPS2421.  We would change to one of the alternatives you mentioned but we require a hard current limit and fault flag.  We will continue our own testing with RRSET>200kohms.

    Thanks

    Ian

  • 0 in reply to Ian Davis20
    TI__Guru 57737 points

    Hi Ian,

    As mentioned earlier, TPS2421 is not characterized for RRSET>200kohms and hence we will not be able to guarantee the current limit variation for the set current limit.

    Please keep us posted when you are ready to change to a new part, we will provide you details about our latest part which can suit your requirement. 

  • 0 in reply to Praveen GD
    Prodigy 190 points

    Hi Praveen,

    I understand that it is not characterised by TI.

    Are you suggesting this is something we can test and characterised ourselves? or that there is a technical reason why the variation will be non-predictable when using a RRSET>200k.

    Thanks

    Ian

  • 0 in reply to Ian Davis20
    TI__Guru 57737 points

    Hi Ian,

    The TPS2421-1 device has not been designed to support current limit functionality for < 1A (Typical). This is the reason why we have not characterized the device functionality for RRSET>200k.

    As the current limit function may or may not work as expected, we do not recommend to use the device for RRSET>200k.

  • 0 in reply to Praveen GD
    TI__Guru 57737 points

    Hi Ian,

    Do you have any other questions ? If not, can we close this thread ?

  • 0 in reply to Praveen GD
    Prodigy 190 points

    Hi Praveen,

    No further questions - you can close this thread.

    Thanks for your help

    Ian.