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Use of TPS2110A

Mario Hernandez
Intellectual 695 points
Other Parts Discussed in Thread: TPS2110A

Hi, I am planning to use the TPS2110A too. I want to do the OR'ing of three different Power Supplies: USB, 3.7V battery and 3.3V cell. I've studied the datasheet and seems to fit well for my purpose. However, I wanted to check with you in case I am missing something here. This is the a basic diagram of it:

-Do you recommend special in1 and in2 capacitors to avoid excessive slew rates in hot pluggable USB and LIPO Bat?

-A holdup capacitor in the output of 4.7uF should be enough for a max load of 35mA?

If you see anything I'm doing wrong or you think there is a better solution for OR'ring this, please let me know

Thanks

  • 0
    TI__Mastermind 42795 points

    The TPS2110A seems like a nice fit for your application. For the IN1 and IN2 sources, will this be only a battery or could some other source provide this power? For battery only and hot plug, I think that 0.1uF ceramic on both inputs will be enough unless the connections from the TPS2110A and battery are long and inductive (with an inductive source, there can be excessive voltage ringing which might damage the TPS2110A.

    4.7uF ceramic on OUT should be sufficient, but you will have to test IN1-IN2-IN1 switchover to ensure that the droop is well managed. You can probably verify this by using the EVM.

    By the way, your schematic symbol is missing a few pins.

  • 0 in reply to Eric Wright
    Intellectual 695 points

    Eric, thanks for your answer.

    Yes, the symbol misses a few pins. It was only for the sake of illustrating you I am planning to connect it.

    My biggest concern is not the switch over between In1 an In2, but the switch from USB to any any of In1 and In2. The power on time of the TPS2110A is a lot bigger than the swtich over time. What do you think about this?

    On the other hand I have to make sure if I have to meet any standard for the fact of placing protection diodes, I am not sure about this.

    Thanks again

  • 0 in reply to Eric Wright
    Intellectual 695 points

    Hi Eric,

    One last thing. If I cascaded two of this MUX. What should I do with the bypass and the input capacitors, add them up? I mean, if at the out of the above part I put another one in series, do I have to place another bypass capacitor or it's ok with the C that's already at the output? I really don't know what to do on those cases

    Thanks

  • 0 in reply to Mario Hernandez
    TI__Mastermind 42795 points

    I think you can use MUX#1 Cout as the bypass for MUX#2 as long as they are not too far from each other on the layout. If MUX#2 is placed some distance (the distance depends on how low the connection impedance between the two is) from MUX#1 then MUX#2 should at least have some local input bypass such as 0.1uF.