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TPS25942A: Priority MUX between POE and AUX PS

Noam Weidenfeld1
Intellectual 780 points
Part Number: TPS25942A

Hi,

I need to make a priority switch between 12V POE module (PD) and a 12V auxiliary power supply.

The POE has the highest priority (No EN signal).

I wonder if I can use the following architecture taken from the TPS25942A datasheet.

Considering:

1. The POE module need a minimal load to be present at start-up. What will happen if the auxiliary power is connected and then adding the POE.

2. The POE (PD) need to present a load in definite time, will the start up condition of the TPS25942 can meet the POE standard.

Thanks

Noam

  • 0
    TI__Guru** 105361 points
    Hi Noam,

    Thanks for reaching out!
    Yes, Priority Muxing configuration shown in Figure 79 of the datasheet can be used.

    1A> In this scenario, the auxiliary supply powers the load. As soon as POE module is available, the power path gets switched to POE source.
    2A> The startup time depends on external dVdT capacitor and the system load. How much is the timing requirement as per POE standard?
    I suggest you to get an EVM and evaluate as per your system conditions.

    Best Regards,
    Rakesh