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TPS2121: TPS2121 doesn't switch over between 12V and 6V

Part Number: TPS2121

We are using TPS2121 as a power path switch between 12V supply and 6V supply. When the voltage is 12V it should give 12V as output, which it does. But when the 12V power goes 0, the output should switch to 6V which doesn't happen in our case.

The circuit is as shown below- 

Can someone help and tell what could have been going wrong?

  • Also to add that in the given schematic Pin 8 and Pin 1 are not connected together as suggested in some reference schematics.

    Could that be the reason for automatic switch over not happening?

  • Hi Ashish,

    Pin 8 and Pin 1 are the VOUT pins. These are the same node. What do you mean by "they are not connected together"? 

    There are two things I noticed:

    1. The voltage on OV2 is 1V. This is very close to the threshold that can trip OV protection. Noise on the 6V rail could trip OV.

    2. You current limit is extremely low. During fast switchover, the might be a spike of current due to the capacitive loading which could cause the current limit being tripped. I would recommend a larger current limit.

    If the error persists, please share scopeshots of IN1, IN2, VOUT and IOUT. 

  • hello Shreyas Dmello,

    Thanks for the help. Our circuit is working now.