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PoE Sifos Testing

derli chan
Prodigy 20 points
Other Parts Discussed in Thread: TPS2378

Dear Sir/Lady,

 TI TPS23851 (PSE) and PSE TPS2378 (PD) are used in our PoE product at the same board. There is a critical issue for our product to our customer. It is that our PoE product can’t pass the IEEE Conformance Test with Sofos PSA-3002 (machine model name) in AT mode (30W). The failed big items include class_v, class_time, class_err, pwron_v, pwron_pwrcap, pwron_maxi, pweron_ovld, pwrdn_over. Especially, there are 3 big items (pwron_ovld and pwron_maxi) can’t be measurement.

 The related parameters in 3 key registers of TI TPS23851 as follows:

address 0x40 set to 2x  or 1x  power mode.

address 0x16 (timing configuration) set to default (0x0) or 0x04 or 0x3C.

address 0x2a (Icut 21 configuration) set to 374mA or 204mA.

Please kindly reply the following questions:

 Q1. Is it possible to solve this issue only by software just adjusting parameter values in TI TPS23851’s register? If so, please tell us how to do by software.

Q2. If not, please tell us how to do by hardware.

 Thanks.

Derli

  • 0
    TI__Mastermind 42795 points

    Please send the PSA3002 test log (Excel file containing the test fails and data). As step 1, can you configure TPS23851 in auto-mode and re-run the conformance test? This will help confirm that the hardware (without software) on your PSE board are working. You could try this in type 1 (15.4W/13W) mode first using TPS2378 with Rclass set for class 3.

    Secondarily, if using an MCU to conrtol the TPS23851, then the MCU will be doing a lot of work to set up and manage the internal registers. The management is not a static process as you've described. For example, when a PD is not connected the ICUT register will be in 1x mode and if when the PD is plugged in and discovered and found to be a class 4 device then the MCU must change the ICUT register to 2x. Unfortunately, TI did not develop any MCU software for the TPS23851.

  • 0 in reply to Eric Wright
    TI__Mastermind 42795 points

    Derli, I think I already received the data logs from your ODM (WTMEC) via email and will check them.

  • 0 in reply to Eric Wright
    TI__Mastermind 42795 points

    Derli, after a review of the logs it appears that the PSA3002 is expecting the TPS23851 PSE to furnish the type 2 hardware classification (also known as two-event physical layer classification) and TPS23851 does not support this. This does not mean that the TPS23851 does not comply with the IEEE802.3at standard because the standard allows a PSE that does not perform two-event physical layer classification to use another method called data link layer classification.

    Have your test engineer review the PSA3002 manual for setup when testing a PSE port that does not do the two-event physical layer classification.