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OPA547, OPA548, and OPA549 - Low and High (and positive and negative) current limiting

Brian Berner
Mastermind 30280 points
Other Parts Discussed in Thread: OPA547, OPA549

This is with regards to charging and discharging a battery.

If the concept is to limit the current as LOW as +/-1mA and limit the current to as HIGH as +/-30A, would it be wise to use a combination of these 3 parts to achieve this goal (e.g. 1 OPA547 and 3 OPA549's)?

Since the application is charging and discharging a battery, the parts would obviously be used to limit both current and voltage at separate times throughout the charge cycle (i.e. initially you want to charge at a constant current as the voltage of the battery rises, then switch to constant voltage in the 2nd and 3rd stage of charging).

Is using these op-amps for this purpose logical? Or is there a more advanced battery charging and discharging system somewhere in the portfolio?

 

Thanks!

Brian

  • 0
    TI__Guru* 93105 points

    Hi Brian,

    The adjustable current limit feature makes the OPA549 easier to apply when that capability is required in an application. Note though that the OPA549 according to the Safe Operating Area (SOA) curves (Fig. 6) is shown to be capable of 10 Amps peak current, but only in pulse operation. The maximum RMS current is 8 Amps and three OPA549 amplifiers connected in the parallel output configuration will produce an RMS output current of 24 Amps. Thus, four OPA549 amplifiers would be required to handle 30 Amps in continuous maximum current operation. Then, one must be very careful to make sure that the SOA curves are observed such that the maximum power dissipation of the OPA549 isn't exceeded.

    I would recommend using the D/A current limit set method to set the current limit level. All 4 amplifiers would have the same ISET current developed. The current limit could be set in accordance with the charge/ discharge cycle requirements.

    I checked the Battery Management products portfolio and the maximum current is in the amperes. You may wish to wish to pose these questions to the E2E Battery Management > Chargers forum. They may have solutions as well.

    Regards, Thomas

    PA - Linear Applications Engineering

  • 0 in reply to Thomas Kuehl
    Prodigy 30 points

    Hi,

    Is it possible to generate 1.3  A of current using three parallel combinations of OPA 547.  I have used 3 OPA 547's in parallel i.e. load resistance (10 ohms) connected to three OPA 547 with a intermediate resistance of 10 ohms each.The power source i used was Aplab regulated DC power supply LQ 6324.

    I have verified this case using TINA software it shows me driving current of 1.3 A.