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Input Protection Device recomendation

Jon Bilbao
Intellectual 1415 points
Other Parts Discussed in Thread: LM5069

Hi Team,

Customer is looking for an input protection device. Device is connected to the battery car and the device should be able to limit the current at 2A (limit, not turning off device when this happens, but to limit current at a certain value) where there may be short peaks of 20A and to limit the voltage to 36V where there may be peaks of 80V but the output should be max. 36V. Additionally, soft-start and polarity protection are required features. They do not have a microcontroller, so it must be able to work as stand alone.

It does NOT have to be AEQ100.

What would be your best recommendation?

Regards,

Jon

  • 0
    TI__Genius 10370 points

    Hi Jon,

    Our team has a really neat selection tool that helps you decide which Hot Swap might be the right choice for your application. You can find it at www.ti.com/hotswap ==> click on the "Tools & software" tab ==> select "Hot Swap selection tool". Below is a screenshot of where to go. 

    I hope this helps :-)

    Best Regards,

    Aramis P. Alvarez

  • 0 in reply to Aramis P. Alvarez
    TI__Intellectual 1415 points
    Hi Aramis,

    I was aware of the tool. Unfortunately I cannot dive so deep in the specifications using this tool. For example, which devices can work as stand alone, which devices limit the current at a certain level and do not turn-off when limit is reached, soft-start is not included in the tool as well. Certainly I am able to search on our tools for the "best" device but your team´s expertise can give more precise recommendation. Perhaps one device is not enough and you can also provide some reference designs, etc.

    Regards,
    Jon
  • 0 in reply to Jon Bilbao
    TI__Genius 12570 points
    Hi Jon,

    The LM5069 and surrounding components can handle most of these requirements (soft start, 2A current limit regulation, polarity protection, clamp output).

    This EVM can handle most of these features (values would need to be tweaked).
    www.ti.com/.../lm5069evm-627

    This EVM is designed based on many features described in this app-note:
    www.ti.com/.../snva683.pdf

    To add soft start, you would need to add a few components (1x ea of resistor, diode, PNP, cap) on the GATE. This can be found in the LM5069 design calculator tool which is on the product folder as well as the tools and software section Aramis has linked to.

    However, this solution would NOT be able to support 20A peak currents. When the device sense roughly 2x the current limit threshold, the device will shut off the FET within a couple microseconds. This feature is called "Circuit Breaker" for this device and is meant to protect against short circuits on the output.

    One possibility may be to install an RC filter on the SENSE lines to slow down the detection of the circuit breaker. It would need to be a large RC filter (depending on how long the 20A transient will be).

    Thanks!
    Alex