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TPS23758: Can it be powered with 24V?

Part Number: TPS23758
Other Parts Discussed in Thread: TIDA-010083,

The  TPS23758 EVB shows 48V auxiliary input voltage

The TIDA-010083 reference design shows that TPS23758 can be powered with 24V

Also, this thread claims that only 48V auxiliary power is allowed

http://e2e.ti.com/support/power-management/f/196/t/860626?tisearch=e2e-sitesearch&keymatch=tps23758

So I'm confused - what is the right question? Can TPS23758 be powered with 24V?

  • Hello Israel,

     

    Some information from The TIDA-010083 reference design report:

    " When operating from PoE power, the PD controller passes through a voltage roughly in the range between 36 V and up to 57 V. When operating from the auxiliary 24-V input, a voltage range of 18 V up to 36 V is specified. This leads to an overall voltage range of 18 V to 57 V for the flyback converter to operate. When designing the transformer and the power stage, the whole voltage range must be considered. However, the output power must be reduced when operating from the auxiliary input to limit the power dissipation to a reasonable level."

     

    Now looking at the efficiency and output regulation of the TIDA-010083 for Auxiliary power, the output drops as well as the efficiency. Also note the load current for 24Vin: it is not raised above ~ 1.8A. The TPS23758-EVM shows a stronger load regulation and efficiency all the way through 2.3A. 

     

    So as I said in the other E2E post, it depends on the load of the system. You could use 24Vin but the transformer may begin to saturate at higher loads. The key factor is the current through the FET of the TPS23758 since it is integrated, the limit is fixed and breaking it means replacing the IC. The recommended operating conditions is 1.6A. If you truly want the load at 2.3A with a 24V input, I still recommend getting a wide Vin transformer. 

    I standby the 37-57V operating range of the EVM since the EVM is rated for 5V / 2.3A. However, you could put 24V in and get 5V at certain loads.

     

    Regards,

    Michael Pah

  • So can you recommend a wide Vin transformer to get full output power from 24V? 

  • Hello,

    Please look at our wide Vin reference designs to find a suitable transformer for your design requirements: 

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments