• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 64 subscribers
  • Views 1767 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

High Side MOSFET Driver LM5060 Options for Large Current

Michael Rasmussen
Prodigy 20 points
Other Parts Discussed in Thread: LM5060

I have been designing a device to switch the battery in a vehicle using MOSFETs. The main requirement is the high current conditions during starting (up to 500A). The current design that I have uses the LM5060 to control 4 large high side n-channel mosfets in parallel. This is working pretty well and able to handle the load for most cases.

However the area that I am struggling to get the desired performance is in over current or short circuit protection. I see on some of the other posts that the LM5060 isn't really designed to cope with short circuit conditions. The current circuit seems to fail to switch the mosfets off and puts them into a half turned on state where they subsequently fail due to power dissipation. 

Is there another device that is likely to be more suited to this application? I have listed below the desired power specifications of the device.

Current - up to 500A

Voltage - 12 to 24V battery (8-30V maximum)

Size - as small as possible so external sense resistors won't really work for the required current (this is why I like the LM5060)

I would apprieciate any feedback or suggestions that could work for this design. It may be that I have some kind of additional circuitry to shutdown in the event of a short circuit.

Thanks.

  • 0
    TI__Genius 10370 points
    Hi Michael,

    Welcome to the E2E forums :-) I'm happy that you're wanting to use one of our devices, but unfortunately are devices cannot support 500A. Our typical applications are from 2-20A for this device.
  • 0 in reply to Aramis P. Alvarez
    Prodigy 20 points

    Thanks for the reply. I would have thought that current was more a property of the mosfet?

  • 0 in reply to Michael Rasmussen
    TI__Genius 12621 points
    Hi Michael,

    That's correct, but there are a lot of things to consider once you get to high currents.

    For example, switching on/off that much current will lead to enormous di/dt which means any inductance (such as trace inductance - or worst case, wires) will cause large inductive voltage spikes. These spikes would need to be clamped by very power TVS diodes, MOVs, and/or power TVS diodes in order to protect the LM5060's abs_max ratings as well as the MOSFET's ratings such as Vds (we would not know what devices would be suitable for clamping this much current).

    Additionally, MOSFETs do not share well when you first turn on. The MOSFET will the lowest Vgs-th will turn on first and absorb most of the current. FETs do share well after they are fully on. This is because a MOSFET drawing more current will end up getting hotter. When a FET gets hotter, its Rds-on increases, so it will draw less current than the other FETs. This ends up balancing the current between the FETs after being on, but the transient state can be dangerous as one can be taking the majority.

    When you create a short circuit on the output, the LM5060 does not have a fast trip shutdown. Current can reach any value and would only be limited by impedance of traces and the short. The LM5060 would run a timer (if it's input voltage did not collapse) and would turn off the MOSFETs after the timer expires.

    If the MOSFETs are getting stuck in a half-on state, I would be concerned that the IC or FETs may already be damaged from exceeding their ABS_MAX rating.

    These are just a couple of considerations but overall we have no experience at these current levels and just cannot provide guidance on what possible issues may come. As Aramis had mentioned, this is orders of magnitude beyond our typical application.

    Thanks!
    Alex