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TPS25942A: Using TPS25942A for selecting between two different power sources

nta_xyz_co
Prodigy 20 points
Part Number: TPS25942A
Other Parts Discussed in Thread: TPS61089, TPS22953

Hi,

I have two different 5v input voltages in my circuit, one of them comes from an adaptor and the other one comes from USB type C connector.

I am thinking about the TPS2594x to use in my circuit as a Power MUXing solution. I have two questions:

1- Is this a good solution based on my power sources (the maximum current on my circuit is about 2A)?

2- Since the PCB size is critical in my project, should I use the output capacitors for both TPS2594x individually or can I share the output capacitors between them? (I mean the C2, C3, C4, C8, C9, C19 capacitors in the TPS25942xEVM Schematic.)

I am also using TPS61089 as a boost converter in my circuit, so I do not want to damage the USB devices connected to my board in case of reverse current or voltage or inrush current.

Thank you for your time in advance.

  • 0
    TI__Guru 57737 points

    Hi,

    Welcome to e2e!

    1. Yes TPS25944x can be used in Muxing configuration. You can have a look at  section '10.3.1.2  Priority Power MUX Operation' in datasheet. 

    2. In power Muxing configuration, the devices outputs are connected which means that the output capacitance is common for both the efuses. 

    If you can share a block diagram of your system, we will be able to comment better on the protection of your system .

  • 0 in reply to Praveen GD
    Prodigy 20 points

    Thank you for your fast reply.

    Here is the whole power section block diagram of my circuit, please let me know if you see any issue or you have any suggestion. 

    Since the fast switch over is not important in my design, can I use the TPS22953 instead of the TPS25942?
    Am I losing any protection features if I use TPS22953?

  • 0 in reply to nta_xyz_co
    TI__Guru 57737 points

    Hi,

    Thanks for sharing the block diagram. I don't see any issue in this configuration. Please be aware of the following while designing TPS25944x in your system,

    1. The maximum voltage rating of TPS25944x at Vin is 20V
    2. A fast reverse comparator controls the internal FET and turns off the FET whenever the output voltage V(OUT) exceeds the input voltage V(IN) by 10 mV (typical) for 1 μs (typical). This prevents damage to the devices on the input side of the TPS2594xx by preventing significant current from sinking into the input side. However, a reverse current of (V(OUT) - V(IN))/ RON) should flow from the output to the input to establish reverse voltage V(REVTH) of –10 mV across the device. The typical value of reverse current, needed for reverse voltage detection is –10 mV/ 42 mΩ = –238 mA
    3. TPS25944x does not support reverse polarity protection directly. In case, you have a chance of input being connected in reverse polarity then you need to add a signal diode in the return path of the IC as shown in section '10.3.1.4 Reverse Polarity Protection' of the datasheet. In this case, also add a bidirectional TVS at the input instead of unidirectional TVS for transient voltage suppression.