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battery/usb switch

or sam
Expert 2020 points

Hi

My circuit works most of the time on battery.

I want that when I connect it to usb/external power the circuit it will automatically will take it power from there and disconnect the battery. when disconnecting the usb/external power it will automatically switch back to battery.

it shpuld be something simple and easy like this:

http://cds.linear.com/docs/en/datasheet/4412fa.pdf

does Ti have something similar?

Regards,

  • 0
    TI__Genius 13700 points

    Hello Sam,

    Looking at the LTC4412 a similar solution in TI hardware would involve the following.

    Using the TPS2421 you would connect your battery input assuming it is greater than 3V to the Vin pin. The wall adapter would be connected via diode to the output pin just like in the LTC case. The key have this device switch between he sources is to tie the enable pin to the positive pin of the wall adapter and have a large pull down resistor to ground.

    This would pull the enable pin when the wall wart is not connected causing the internal FET to turn on and pull power from the battery and then when the wall wart is plugged the resistor between the positive pin of the wall wart and ground would cause the EN pin to go high thereby opening the FET and when the wall wart is removed the EN pin voltage will drop and the FET will close connecting  the battery again.

    This solution is very similar to what you provided as an example does this sufficiently answer your question or were you looking for some other variation of a solution? Let me know if you have questions.

    Ryan May