USB and Coin battery switching

Dear team,

We are looking for a power switching device.

Power Train of module is powered through  USB and coin battery.

1. Power Train   

    A. Battery - Use 3.0V coin battery   

    B. USB power - After the coin battery is consumed, supplying the coin battery, the main power is supplied via USB. (At this time, the coin battery is connected - there is no battery current)

==>We are looking for the parts that switch the above two power source automatically.


Thank you.

Best regards,