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PoE - TPS23756 - 12V out design

Ahmad Qadomi
Prodigy 80 points
Other Parts Discussed in Thread: TPS23756, TPS23753, TPS23752, TPS23751

Hi. I'm designing a type 2 PoE PD. I'm thinking about using TPS23756, The system limitations are:

-12v Output at 1.5 A.

-Auxiliary input range: 12-18 VDC.

- Efficiency: > 85%

-Auxiliary has the highest priority.

Could you please help me with a circuit schematic and BOM. and if there is a design example shows how to determine the values according to the system requirements it would be better because i might need other designs for other power levels.

Thank You

  • 0
    Prodigy 80 points

    I decided to use SLVA305A to help me in design, and i think i can apply the same circuit for TPS23753 on TPS23756 Right??!

    If this is possible then i have a question in SLVA305A, Page 7, 2.6.2 Secondary and Bias Winding Voltage Drops

    Where does VdropSECONDARY value (=0.4v) came from ? is there any equation?

    Thanks ..

  • 0 in reply to Ahmad Qadomi
    TI__Mastermind 42795 points

    There is a TI reference design for 12V, 1.25A posted on the TPS23756 product page (http://www.ti.com/tool/pmp6659) which is a good starting point. The additional output power required may push you into a larger transformer. This is a self-driven synchronous rectified flyback design and you can use the principles outlined in SLVA305A to size the transformer TR. For the controller, you could also use a new TI IC, TPS23751 (or TPS23752 with sleep mode feature) which can boost light load efficiency using VFO technology (there is a similar EVM design for 22.5W but at 5V output). TPS23751 can be used in wide VIN applications.

    For SLVA305A, 2.6.2, the Vdrop is in reference to conduction forward voltage drop of the rectifier. In this case a schottky diode is assumed. For a sync rectifier, a lower # can be used based on the Rdson and ON current of the FET.

  • 0 in reply to Eric Wright
    Prodigy 80 points

    Thanks for your kindness, when I start implementing this option, I may need more help and I'm really glad to know that you are there Eric, Thanks again