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TPS23758: Does TI provide a mixed POE (at class1 and class2) PD solution?

Part Number: TPS23758
Other Parts Discussed in Thread: TPS23751, TPS23754, TPS23756, TIDA-050026-23882, TPS23882

Hi,

I am designing a camera with an embedded Cyclone 10 CX220 FPGA which should be powered over ethernet.

I found this pretty neat solution on TI website, https://www.ti.com/lit/ug/tidueu3/tidueu3.pdf. This could fit my application, but I have some doubts about the total power consumption of my future board. For example, the total consumption of the Cyclone 10 GX devkit provided by Intel FPGA is around 15W when running the DDR3 example. However, this board has a tons of external device and IOs, so this doesn't really reflect my case.  Does TI provide a POE PD device both POE at class1 and class2 capabilities?

Best regards,

John

  • Hi John,

    Thank you for your question. The TPS23758 is capable of being used in Class 0-3 power level applications. The design you are referring to uses the TPS23758 in a Class 0 design (up to 13W) and has Rclass set to 649 ohms. However, by changing the class resistor to Class 1 or Class 2 values, the PSE will negotiate and send only the class power being requested.

    In order to change this design to support Class 1 power levels only you can take this design and switch out the class resistor to Rclass = 121 ohm for Class 1 power levels (up to 3.84W).

    In order to change this design to support Class 2 power levels only, you can take this design and switch out the class resistor to Rclass = 68.1 ohm for Class 2 power levels (up to 6.49W).

    Please see Table 1 below in the TPS23758 datasheet which highlights the resistor values used for the various Class 0-3 power levels.

    Please let me know if you have any additional questions. Thanks!

    Best Regards,

    Brett Colteaux

  • Hi Brett,

    Thank you for your reply.

    I did a mistake when I was writing my question. In fact, I would like to change between class 0 and class 4 (13W and 25.5W). I don't know why I wrote class 1 and class 2 : / 

    I looked deeper into TI POE PD parts and there are some device that implements this feature. In my particular case, it should be a bit clever to use a class 4 PD. 

    However, my system has a central Arria10 FPGA + PSE which provides power to several cameras, let's say 12, so I have to take care of the startup sequence especially when the PSEs performs the classification stage as it doubles the amount of power compared to a class 0 device.

    Sorry again for the mistake,

    Have a nice day Brett

  • Hi John,

    Thank you for the clarification and no worries about the typo.

    If you'd like to use the same IC for both Class 4 (25W) and Class 0 (13W) designs, we have several options:

    1. TPS23751

    • This IC can be used in Class 0-4 designs and is targeted for flyback only applications.

    2. TPS23754 and TPS23756

    • These ICs can be used in Class 0-4 designs and are targeted for ACF and flyback applications.
    • The main difference between the TPS23754 and the TPS23756 is that the TPS23754 can support adapter ORing from 24V to 60V whereas the TPS23756 can support adapter ORing from 12V to 60V

    If you can provide your system level requirements (output voltage, output current, isolated or non-isolated, etc) than I may be able to help to recommend a reference design for your application. 

    FYI - If you are designing the PSE side of the cable as well I recommend you take a look at our TPS23882 PSE. We have a great reference design, TIDA-050026-23882, that can be used to accelerate your design and to implement port power management through our FirmPSE ecosystem. This reference design is a 24-port IEEE 802.3at design which can send up to 30W per port. 

    Please let me know if you have any additional questions. Thanks! 

    Best Regards,

    Brett Colteaux

  • Thank you,

    this sounds perfect to me.

    Can I contact you in private for the PSE module?

    Best regards,

    John