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Switching regulator causing radio sensitivity degradation

skwok
Prodigy 30 points
Other Parts Discussed in Thread: BQ24278

I am using BQ24278 switching regulator with built in lion ion battery management.

With external wall plug supply, the radio works fine and sensitivity is good.

With battery supply, the radio also works well.

But when battery is plugged in with external supply connected, then current starts to switch in and out of battery. This seems to cause radio sensitivity degradation.

Our product does not need battery to supply current when external supply is connected. Is there anyway to stop the battery supplying current to the load? Please advise.


Thanks.

  • 0
    TI__Genius 13700 points

    Hello,

    What is the status of the /CE pin when you see this additional noise?

    Do you see this additional noise at all times when the adapter is plugged into the system with the battery or does the issue only occue when the battery voltage is above the recharge threshold which is 120mV below the Vbatreg voltage.

  • 0 in reply to Ryan May
    Prodigy 30 points

    Thank you for help.

    CE is tied to ground.

    When battery is plugged in and load current is small, it is fine.

    When I increase the load current, I can see current jumping up and down on power supply current meter then I have sensitivity problem.

    Again, is there anyway to force battery on charge mode only and not going to the supplement mode (i.e. supplying current to regulator)?

    Again, thanks.

  • 0 in reply to skwok
    TI__Genius 13700 points

    Hello Skwok,

    Sorry for the delay,

    I have not been able to find anything on disabling supplement mode. The best way to avoid it would be to have a higher voltage/stronger adapter to ensure that the supplement threshold is not reached during periods of higher load.

    I took one of the BQ24278 EVMs to the lab and tried to find a way to ensure that supplement mode would not occur.


    It would be interesting to see what the input source is doing during this jumping that is creating this problem. Does placing a bulk capacitor on the chip input influence this operation at all?


    One less desirable solution would be to utilize the CD pin to single source the power from the battery instead of the adapter to eliminate the toggling noise you are observing.