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Original question:

TPS23754EVM-420: POE Design for 24V

TPS23754EVM-420: POE Design for 24V

Namith HL
Intellectual 570 points
Part Number: TPS23754EVM-420
Other Parts Discussed in Thread: TPS23861EVM-612, TPS23861, TPS23754,

HI Darwin,

One more question,

Now  we are looking to change RJ45 connector and External transformer solution instead modular jacks .If you any suggestion for suitable parts please let me know.

I have quick look at the online distributor sites ,but their im finding parts only suits for POE can we use that becoz we have POE+ option in our requirement.

Regards,

Namith

  

  • 0
    TI__Mastermind 40530 points
    Hi Namith,

    If looking for Type 2 data transformer, I recommend using the one in the TPS2378EVM below. Thanks!

    www.ti.com/.../slvu682.pdf
  • 0 in reply to Darwin Fernandez
    Intellectual 570 points

    Hi Darwin,

    Since we are new to POE concept, some how we have designed by referring several TI reference design and your valuable feedback.

    Now we have to test and validate the POE design . Kindly suggest how to test POE ,is there any Test procedure or any document available with your side please share and  What all the parameter and test equipment required to proceed.

    Regards,

    Namith

  • 0 in reply to Namith HL
    TI__Mastermind 40530 points

    Hi Namith,

    I recommend ordering a TPS23861EVM-612. This has a GUI that you can use to see if the PSE is measuring proper detection and class. Since the TPS23861 starts up to automode, the port should power the PD right away after passing detection.

    Regards,

    Darwin

  • 0 in reply to Darwin Fernandez
    Intellectual 570 points

    Hi Darwin,

    Please share test report for 24Vout using TPS23754  design.

    It would be helpful for us if have any specific document that how to test POE design and what all the test to be conducted for POE as per IEEE standards,Since we are doing POE design for the first time.

    Awaiting for your reply as earliest.

    Regards,

    Namith HL

  • 0 in reply to Namith HL
    TI__Mastermind 40530 points

    Hi Namith,

    Unfortunately, since this is an older design from a different engineer, we do not have the test report. The only thing that changed in this design is the power stage of the TPS23754EVM-420. So from a IEEE compliance point of view, it is unaffected. The tests on the TPS23754EVM-420's user's guide should be tested on your board. In addition, we did SIFOS testing (automated PoE test for the IEEE802.3 standard) for compliance. Please see attached report from the TPS23754EVM-420.

    TPS23754EVM-420_SIFOS.xls

  • 0 in reply to Darwin Fernandez
    Intellectual 570 points
    Thanks for quick response,

    Previously you have suggested TPS23861EVM-612 for our POE design using TPS23754, By using this can we test initially?

    How POE signature Detection,classification and power delivered to our PD.

    Is that board will provide 48V nominal voltage and rated current?

    Regards,
    Namith
  • 0 in reply to Namith HL
    TI__Mastermind 40530 points
    Hi Namith,

    Yes, using the TPS23861EVM-612 is a good way to test your PD solution because you only have to connect 50V (with a ~30W power supply or higher) to the EVM's input and the EVM will work in 'auto mode' where it will automatically do detection, classification, and turn ON per the IEEE standard when the PD is connected to it. Then if you want to get into more detailed values, you can download the PSE's GUI to look at currents, and voltages that the PSE is measuring.

    Thanks!
    Regards,
    Darwin
  • 0 in reply to Namith HL
    Intellectual 570 points
    Darwin,

    some questions related to design,
  • 0 in reply to Darwin Fernandez
    Intellectual 570 points
    Darwin,

    Some queries related to design,

    As per my understanding initially PSE will apply 2.1V to 10.2V during signature detection to DEN pin. Is it correct?

    DEN pin is pulled to VDD through 24.9Kohm (High impedance state ) if detection is in the outside the voltage range ,correct ?

    once Detection is done it will apply voltage range between 14.5V to 20.5 V?

    If we fixed 63.4ohm the Classfication in class 4 , then directly it will provide 48V and class 4 power range?

    Typical VC, CTL and T2P voltage?

    Can u please explain brief about classification and detection ,T2P

    What is the purpose of Power analyser , can we check the classification and detection hiccup waveforms over there

    Regards,
    Namith
  • 0 in reply to Namith HL
    TI__Mastermind 40530 points
    Hi Namith,

    Please see my comments below:
    As per my understanding initially PSE will apply 2.1V to 10.2V during signature detection to DEN pin. Is it correct?
    [DF] Correct, however please see Figure 20 of the datasheet for the correct detection range.

    DEN pin is pulled to VDD through 24.9Kohm (High impedance state ) if detection is in the outside the voltage range ,correct ?
    [DF] If outside detection range, there is no current through DEN pin or the 25k ohm (high impedance)

    once Detection is done it will apply voltage range between 14.5V to 20.5 V?
    [DF] Correct, except please see Figure 20 for the correct class range.

    If we fixed 63.4ohm the Classfication in class 4 , then directly it will provide 48V and class 4 power range?
    [DF] If passing detection, the PSE will power up to 48V. The power will depend on if the PSE can provide Class 4 power or not.

    Typical VC, CTL and T2P voltage?
    [DF] VC=12V, CTL=~2.25V, T2P is a logic signal either RTN or pulled up to VC (12V).

    Can u please explain brief about classification and detection ,T2P
    [DF] I believe section 7.4.1 overview of PoE is the best description of detection and class. T2P is needed for the PD to know what Type power the PSE delivered to the PD. The alternative to hardware classification is negotiation through the data layer.

    What is the purpose of Power analyser , can we check the classification and detection hiccup waveforms over there
    [DF] The purpose is to do automated testing of a PD for IEEE compliance. The newer PDA analyzers can take waveforms.
  • 0 in reply to Darwin Fernandez
    Intellectual 570 points
    Hi Darwin,

    Had a doubt while testing one of the Powered device designed earlier ,we have a midspan PSE that can give nominal 48V and maximum current upto 1.2A .
    if that is the case how we can check detection and classifcation ? also we have fixed our classification to class4 by keeping jumper to 63.4ohm
    then as per my understanding T2P signal to be low all the time since im getting POE+ input from PSE Midspan.

    How i can validate the POE ?
    Is this is called as automatic detection?

    Regards,
    Namith
  • 0 in reply to Namith HL
    TI__Mastermind 40530 points
    Hi Namith,

    To check detection and classification, you can try measuring the voltage between VDD and VSS and current through VSS path (Ethernet input current) with an oscope. A midspan is supposed to send voltage in between the detection voltage then there should be two class fingers afterwards (if connecting to a type 2 midspan). If you don't see this, then it could be failing detection.

    If you were to use the TPS23861, its GUI would show whether your PD passes detection and what class is being presented by the PD.

    I'm not sure what 'automatic detection' means however, yes the PSE midspan should try detection right away when the PD gets connected.

    Regards,
    Darwin
  • 0 in reply to Darwin Fernandez
    Intellectual 570 points

    Hi Darwin,

    Automatic detection, i mean auto mode detection.

    we have one PSE source that has 48V/1.2A  mentioned in the datasheet.By using that i have tested one of the PD designed earlier in our organization using some other chip for my reference since our design board will come early next week.

    I had checked the same point where datasheet mentioned similar to VDD-VSS in our design  as you mentined, but im not able to capture that detection and classification graph on oscilloscope.

    hence i have asked automatic detection happened,

    Can you suggest any Midspan PSE.?

    As for as you we can capture detection range in CRO right?

    But our source will give PSE 48V nominal output right away ,if i probe in VDD-VSS  i could see same voltage then?

    Regards,

    Namith

  • 0 in reply to Namith HL
    Intellectual 570 points
    Hi waiting for reply...

    Regards,
    Namith
  • 0 in reply to Namith HL
    TI__Mastermind 40530 points
    Hi Namith,

    Yes you can probe VDD-VSS even with multimeter. If the 48V is applied to the VDD-VSS then the PD has passed detection. If not, then it did not pass detection.

    I still believe it will be easier to debug with TPS23861EVM which will do auto-mode when 50V is inputted to the input connector. This means yes it will do detection right away when PD is connected to it and would do 2-finger classification.

    However, if you want to test with a off the shelf midspan, I recommend Phihong midspans that are IEEE802.3at (type 2) compliant.
    phihong.com/.../midspan_30.php
  • 0 in reply to Darwin Fernandez
    TI__Mastermind 40530 points
    Hi Namith,

    Has this thread be resolved? If so, please click the resolved button so we can close this thread. You can also post a new thread if having further questions. Thanks!
  • 0 in reply to Darwin Fernandez
    Intellectual 570 points

    Hi  Darwin,

    we have ordered TPS23861EVM-612  as per your feedback for testing our PD Design.

    But after seeing the test setup of the EVM i have found we need USB to GPIO adapter for GUI interface to PC.

    Is the evalaution model contain this Adater as a package or we have to take seperately. Kindly let me know more about this please.

    How to check the GUI reading with this Evaluation model.

    Regards,

    Namith

  • 0 in reply to Namith HL
    TI__Mastermind 40530 points
    Hi Namith,

    If wanting to use the GUI to see the detection/class values it records, yes it will need the USB to GPIO adapter from below link.
    www.ti.com/.../usb-to-gpio

    The EVM can still work in automode when you apply the 48V to the power input. Then you can connect the PD to see if it passes (it will be like midspan injector).