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UCC27424: Suggestion for battery switching circuit using Gate Drivers

Part Number: UCC27424
Other Parts Discussed in Thread: UCC27524, UCC27624

Hi, 

I am looking for a design suggestion for automatic switching of battery supplies(primary and secondary) to the main processor in one of our projects. We are looking for a seamless transition between the batteries during operation. The use case is that the user can replace a dying battery with a fully recharged battery without shutting down the system.

We want the primary battery to connect to the system by default and switch to secondary battery when the back cover is removed which has a magnetic. It is sensed by the hall sensor on the main board. The hall sensor output is 1.8V logic( High when there is no magnetic field and 0 and when there is).

The peak load current can go up to 6A.

We plan to use back to back PMOS circuits as shown below:

Do we need to use High Side Gate Drivers in such an application? What kind of gate drivers do we need to use? Please suggest if there are seamless solutions from TI portfolio for such an application.

Please let me know if you need any details. Eagerly awaiting your response as we are running short of time for gerber release( in a week).

Thanks,

Naveen

  • Hello Naveen,

    If the high-side are PMOS, they may not need a high side driver depending on the voltage. Let me share a slide:

    So for the high-side, if N-type FETs are used, you will need some sort of charge pump/high-side driver which integrates that. If P-type is used, then as long as the driver's VDD can match the the battery voltage, you will be okay, here is a simulation:

    This is using a dual channel low-side driver such as UCC27524 or UCC27624 (a better choice but doesn't have a PSpice model yet). 

    So when the driver is high, Vgs = 0V, and the load is disconnected. When it is low, it goes to -12V here, and the load is connected. Your circuit is definitely different from what I have seen before, so there may be some extra things I haven't considered. If you don't think the driver will work, we have products in the Power Switches category that might. I believe that category will have some good options.

    Please let me know if you have any follow-up questions.

    Thanks,

    Alex M.