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LM5146-Q1: Overcurrent protection vs. current control/limiting

Anthony Andrew
Prodigy 30 points
Part Number: LM5146-Q1
Other Parts Discussed in Thread: LM5085, , LM5146

Hello, 

We were using LM5085 as a battery charger configured for 16.8V output limited at 5A. We had to switch to LM5146-Q1 because it can accept up to 100V, while the LM5085 will only accept up to 75V. As far as I can understanding from using the evaluation board for LM5146-Q1, it is possible to set a current limit that will trip an over current protection -- however this seems to shut off the output current rather than clip it at a specified value. 

Is it possible to configure LM5146-Q1 so that it delivers current-limited power? i.e.: when the battery wants to pull 20A at 16.8V it will only get 5A from the circuit. 

Respectfully, 

-Anthony Andrew

  • 0
    TI__Mastermind 23845 points

    Hi,

    Yes, the LM5146 will engage a hiccup timer and shut off after 128 consecutive cycle being in the current limit state.

    Unfortunately since this is built in into the IC, it could not be disabled. 

    I found this article that might help http://www.ti.com/lit/an/snva829/snva829.pdf

    Since this is a controller, you might need a separate step down converter to power the VIN of the IC

    Thanks

    -Arief

  • 0 in reply to Arief Hernadi
    Prodigy 30 points

    Hello Arief, 

    Thank you for the resource, it was very helpful. Allow me to apologize for my lack of knowledge on the subject -- my background is not in electrical engineering. 

    I believe that our main issue is actually the input voltage. Like I said earlier, we were able to build a CV/CC converter out of the LM5085, but since the chip may see up to 85V or even 100V briefly during a load dump, we would like to find an alternative chip that can handle these high voltage conditions without relying on more external circuitry. Do you have any suggestions? 

    Respectfully, 

    -Anthony

  • 0 in reply to Anthony Andrew
    TI__Mastermind 23845 points

    Hi Anthony,

    No worries. I tried to look in TI for a battery charger up to 100V but I could not find one.

    Since this is a load dump type of condition, will it be possible to put somekind of protection such as TVS diode at the front end to limit the voltage seen by the IC?

    This might make it a little easier in the design. What is the operating (normal) voltage for your input voltage?

    Thanks

    -Arief

  • 0 in reply to Arief Hernadi
    TI__Mastermind 35210 points

    I assume that this issue is resolved. If not , please start a new thread and we will get back to you with an answer.

    Thank you.