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TPS23753A low cost design using Würth 749119350

Michael Gilge
Expert 1720 points
Other Parts Discussed in Thread: TPS23753A, TPS23753, PMP7355, TPS23754, PMP6812, PMP8803

Hello,

I am looking for a low cost TPS23753A reference design for 5V output using the Würth Elektronik transformer 749119350.

Regards,

Michael

  • 0
    TI__Mastermind 40820 points
    Hi Michael,

    I don't believe we have designed with this transformer in the past for poe. However, if looking to design around this transformer, I recommend using the below link to design a very simple low cost flyback using this transformer's parameters.
    www.ti.com/.../slva305c.pdf

    Regards,
    Darwin
  • 0 in reply to Darwin Fernandez
    Expert 1720 points

    Hi Darwin,

    we need a low-profile design with 10-13W power and below 9mm height. Maybe you do have a reference design with a transformer on a EFD15 or similar low profile core?

    Best regards,

    Michael

  • 0 in reply to Michael Gilge
    TI__Mastermind 40820 points
    Hi Michael,

    Unfortunately, we currently do not in our poe designs. I recommend using the design guide above. Or talking to your local TI FAE to help with a custom power supply design.

    Regards,
    Darwin
  • 0
    Prodigy 130 points
    Hi Michael

    I have achieved a PD using TPS23753 and 749119350, please refer to this post

    e2e.ti.com/.../481280
  • 0 in reply to Navin Narayanan
    Expert 1720 points

    Hi Navin,

    thank you so much for pointing me to your design change, based on the slvua27a. My only concern is that you are limited to 9W of output power by using only 2 of the 3 secondary windings of the 749119350.

    We have based our design on the low cost reference design slvrb20.pdf, replacing the Coilcraft POE13P-50L with the Würth 749119350. Of course there is no synchronous but a single Schottky diode rectifier, so efficiency will not be as good as in your design.

    Best regards,

    Michael

  • 0 in reply to Michael Gilge
    Prodigy 130 points
    Hi Michael

    Youre welcome, hope I have been able to help, our system only requires 1.2A @5V so this is suitable for us

    Which is the slvrb20.pdf, is it the TPS23753AEVM001?

    Thanks
    Navin
  • 0 in reply to Navin Narayanan
    Expert 1720 points
    Hi Navin,

    it is the design PMP7355 from the TIDesigns Library:
    www.ti.com/.../PMP7355

    Best regards,
    Michael
  • 0 in reply to Darwin Fernandez
    Expert 1720 points

    Hi Darwin,

    following your advice I have a functional TPS23753A low cost flyback design. Do you have a proposal for a TPS23754 low cost design?

    I would need only 3W on the 3,3V output side but app. 20W on the 48-57V DC/DC input rail. Could I use the DC/DC flyback from the TPS23753A also on the TPS23754?

    Regards,

    Michael

  • 0 in reply to Michael Gilge
    TI__Mastermind 40820 points
    Hi Michael,

    I don't see an issue with using the same power stage as your TPS23753A converter for the low power solution then having the TPS23754 take the rest of the power between VDD and RTN. You can even use the app note on the first post of this thread to calculate the solution for any of the parameters that might've changed.
  • 0 in reply to Darwin Fernandez
    Expert 1720 points
    Hi Darwin,

    is there a low-cost flyback design (i.e. diode rectifiers) with dual output voltages? We are in need of 12V and 3,3V output.
    Thanks,
    Michael
  • 0 in reply to Michael Gilge
    TI__Expert 7500 points
    Hi Michael,

    What is your output current?
    We have some reference design with dual output, but it's not a diode rectifiers design.
    However, you can modify the schematic to meet your spec.

    -Ben
    Please click the Verify Answer button on this post if it answers your question. Thanks!
  • 0 in reply to Ben Kuo
    Expert 1720 points
    Hi Ben,
    thanks for the reply. We have about 0.5 - 0.6 A of current.
    Please not that the role of "output" or "input" is not fixed: Depending on where power is available, inputs and outputs might switch places.
    --Michael
  • 0 in reply to Michael Gilge
    TI__Expert 7500 points
    Hi Michael,

    Sorry, I can't catch what you mean "inputs and outputs might switch places". Can you give me more detail about your block diagram for you application? It's will very useful for me to give a best solution for you.

    I assume that you want to find 12@0.6A and 3.3V @0.6A, so we can modify reference design "PMP8454" to meet your spec.

    -Ben
  • 0 in reply to Ben Kuo
    Expert 1720 points

    Hi Ben,

    sorry for not being clear. We have 2 boxes, one local and one remote, which are connected by a DC@48V 2-wire line. Usually the local box would feed 48V@0.6A to the remote box. The remote box has a bridge rectifier at the 2-wire input, in order to safeguard against wrong polarity of the 2-wire line. So the 2-wire line is polarity agnostic. In this case the local box provides the power output and the remote box the power input.

    However, if there is no power at the local end available, we would like the option to reverse feed the local box from the remote box. In this case the power input and output are reversed and we have the task to go around the bridge rectifier for the reverse power direction. One idea was to use 2 hot-swap circuits and enable them for each direction.

    Does this help? --Michael

  • 0 in reply to Ben Kuo
    Expert 1720 points
    Hi Ben,
    sorry - I mixed up a different thread. Forget what I just wrote. Yes, we need a low cost design with 12V@0.1A and 3.3V@0.5 or a total of app. 3W. I believe at 3W power the synchronous rectification is not justified and we could use Schottky diodes instead.
    --Michael
  • 0 in reply to Michael Gilge
    TI__Expert 7500 points

    Hi Michael,

    Thanks for your update!

    We don't have 12V and 3.3V reference design. But we can modify the schematic from PMP8752. 

    Change sendary MOSFET to diode, transformer,connect DT to VB,etc.

    If you need any help, please contact us.

    -Ben

  • 0 in reply to Ben Kuo
    Expert 1720 points

    Hi Ben,

    I have 3 PoE reference designs with 12V output:

    - SLVU314F (with components selected for 12V from the BOM)

    - PMP6812

    - PMP8803

    The point is that component values differ a lot, and I am confused which of the above I should use. For example the feedback loop or the series resistor for current sensing are quite different in terms of resistor and capacitor values

    Best regards,

    Michael

  • 0 in reply to Michael Gilge
    TI__Expert 7500 points
    Hi Michael,

    Choose the right compensation value is based on your whole system.
    For example, you used different transformer and had different inductance. so your compensation value should be different.

    Choose one of above reference designs which is fittest your spec.

    -Ben
  • 0 in reply to Ben Kuo
    Expert 1720 points
    Hi Ben,

    do you happen to have a reference schematic using the Coilcraft POE70P12L (or any other 12V @ 5-7W) transformer?

    --MIchael
  • 0 in reply to Michael Gilge
    TI__Expert 7500 points

    Hi MIchael,

    We have PMP4745 which is 12V@1A application.

    You can refere to application note, SLVA305C, to modify the schematic and match your spec.

    --Ben

    If this post answered your question, please click Verify Answer.

  • 0 in reply to Ben Kuo
    Expert 1720 points

    Hi Ben,

    I have done so. Would you be willing to take a look at the schematics in order to catch anything I might have overlooked?

    Please note that the design is a "no electrolytics" one and uses only ceramics (X7Rs).

    Best,

    Michael

  • 0 in reply to Ben Kuo
    Expert 1720 points

    Hi Ben,

    would you be so kind to take a look at our schematics and act as a second pair of eyes? Can you endorse our schematic?

    --Michael

  • 0 in reply to Michael Gilge
    TI__Expert 7500 points

    Hi Michael,

    below are my suggestion.

    1. C69 value should be 0.05uF to 0.1uF

    2. What are your rated voltage of input cap? (C73, C74, C75, C76)

    3. 80K ohm for R35 is enough.

    4. Please check R34, R35, R44, R51 Size.

    5. What is the function of D10?

    -Ben

    If this post answered your question, please click Verify Answer.

  • 0 in reply to Ben Kuo
    Expert 1720 points

    Ben Kuo said:

    Hi Michael,

    below are my suggestion.

    1. C69 value should be 0.05uF to 0.1uF

    OK, thank you!

    2. What are your rated voltage of input cap? (C73, C74, C75, C76)

    They are all 100V: 100V_4u7_1812

    3. 80K ohm for R35 is enough.

    OK

    4. Please check R34, R35, R44, R51 Size.

    R_TF_20R_5_0805               |SMT 0805 5% 0,5W                        |R34,R51

    R_MS_100K_1_0805              |SMD 100ppm 0,125W     Cad=C             |R35

    R_MS_0R51_1_1206              |SMD 75ppm 0,250W     Cad=M              |R44

    5. What is the function of D10?

    I found D10 in one of the reference designs. I would presume the Zener acts as a safety device to keep the voltage on the APG Pin below 5.1 V.

    -Ben

    --Michael

    If this post answered your question, please click Verify Answer.

  • 0 in reply to Michael Gilge
    Expert 1720 points

    Hi Ben,

    do you approve the design with the change of C69 to 0.1uF?

    --Michael

  • 0 in reply to Michael Gilge
    TI__Mastermind 40820 points

    Hi Michael,

    There should be no issue with using 0.1uF. It is typical in most of our PD designs.

  • 0 in reply to Darwin Fernandez
    Expert 1720 points

    Hi Darwin,

    iI am referring to the eval schematic of slvu304c.pdf: 

    Question: To what extend can I decrease the value of R2 (now: 6.49k) in order to make the LED D21 brighter?

    Best regards,

    Michael