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TPS2120: SEL function

Cristopher Mendez
Prodigy 20 points
Part Number: TPS2120

Hello,

We've designed a product that uses the IC mentioned as a selector of two batteries (see picture below), where EXT_BATT is a 12V battery and INT_BATT is a 7.4V.
This product is in the development process, we are already waiting for the prototype of the PCB to arrive but before we get our hands on it, we want to confirm if this configuration really works. 
The SEL pin will be normally pulled down, thus selecting INT_BATT, and when the conditions to switch batteries are met, an MCU will pull SEL pin high to switch to EXT_BATT.
Thanks in advance for the support and regards,
  • 0
    TI__Prodigy 580 points

    Hey Cristopher,

    That's correct. It should work as intended.

    Thanks,

    Sam

  • 0
    Prodigy 20 points

    Hi Sam Isaac, I just tested the circuit and for some reason, it's selecting IN2 as the defaut power source with SEL pin Low and even when I pull SEL pin High, with both power sources connected, it does not change the power source, it stays with IN2. Any advice as why is this happening?

    Regards, 

  • 0 in reply to Cristopher Mendez
    TI__Prodigy 580 points

    Hey Christopher, 

    So SEL pin does not automatically change which Input it picks:
    If SEL is low and PR1 is High then Input 1 is chosen.

    If SEL is low and PR1 is low then Greater supply is chosen.

    If SEL is high and PR1 is low then IN2 is selected if inputs are valid.

    In your case, You have PR1 connected to ground which leads to either pick IN2 or pick greater (in this case IN2).

    Please advise to use PR1 connected to one of the 2 sources that needs prioritizing using a voltage divider.

    Please refer to the following table:

    Thanks,

    Sam