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TPS2121: Please provide a circuit for dual power switching and somt questions about TPS2121

Part Number: TPS2121

Hello:
I now need a circuit for dual power switching with the following requirements:
1 The first connected segment of power supply has priority (regardless of which port)
2 Need to be able to set the power switching threshold voltage
3 When the voltage of the power supply terminal is lower than the switching threshold voltage, the power supply is automatically switched to the other terminal, and the switching time is not longer than 20us
4 Need to be able to manually switch the power supply port through external MCU control.
5 The normal power supply voltage is 12~17V, and the steady state current is not more than 0.5A
6 Support hot swap, or you can add external hot swap management circuit
7 with power status output

Now I have made a test board with TPS2121, and I haven't finished the test. Now I find that when the power supply port is controlled by the external CP2 pin to be IN2, when the power supply of IN2 is unplugged, Vout will drop to a very low voltage, which will cause the post-stage system Power-down reset.

Excuse me:
1 Is there a plan for my request?
2 Is this problem with TPS2121 a common problem? Is there a way to solve it?

thanks

  • Hi User,

    TPS2121 is capable of fast switching. We define the switching time as the time during when no input is connected to the output. Do you have a waveform that describes this event that you are seeing? We would like to see PR1, CP2, VOUT and ST in the first scopeshot and VIN1, VIN2, VOUT and IOUT in the second scopeshot. Please also provide a schematic. Do note that if you are switching from a higher voltage to a lower voltage, the device will wait for the output to discharge just below the lower voltage level before completing the connection to avoid any backflow of current. 

    Secondly, it looks like you are performing manual switchover with the CP2 pin. the CP2 voltage has to be high for fast switchover to work and so I would recommend swapping your inputs in a way to use PR1 to toggle between the inputs with your external controller. TPS2121 and powerMUXes as a whole do not have any hotswap protection but I would ercommend using clamping diodes on the input to avoid any voltage spikes during the hotplug event.

    Thirdly, I would recommend the use of hysteresis to avoid any sort of bouncing between the inputs during switchover

    For further information on seamless switchover I would recommend you looking at this FAQ: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1023453/faq-tps2121-how-do-i-achieve-a-seamless-power-switchover-using-ti-s-power-mux-devices

    Thanks,

    Shreyas