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Original question:

PMP31092: PMP31092

PMP31092: Looking for alternates for the isolation transformer based on PMP31092 reference design

Snigdha B
Prodigy 90 points
Part Number: PMP31092
Other Parts Discussed in Thread: LM5045

Hello, 

I want to use the PMP31092 reference design for the POE PSE application. I'm looking for an isolation transformer that can be used with LM5045 per the ref design. 

However, the BOM component is not available online or OTS. Can other isolation transformers be used with this part for 100W (48V at 2.5A) output application? If yes, could you please provide a list of alternates.

Thank you,

Snigdha

  • 0
    TI__Expert 5915 points

    Hello Snigdha,

    Sorry for the late reply!

    I searched for an alternative part to replace the transformer for PMP31092, supplying 48V instead of 56V, but I didn't find any available off-the-shelf part.

    I believe you need to request a new custom transformer to your preferred vendor.

    Regards,

    Roberto 

  • 0
    Prodigy 90 points

    Hi Roberto, 

    Thank you for the update. I was curious about the shielding requirements for the isolation POE PSE application. Do you have any recommendations or resources you can point me to?

    Thank you,

    Snigdha

  • 0 in reply to Snigdha B
    TI__Expert 5915 points

    Hi Snigdha,

    Actually I don't have specific shielding requirement documentation available.

    I added my colleague David to check whether he does.

    Hi David,

    Can you please let Snigdha know whether we have resources about POE PSE isolation requirements?

    Thanks,

    Roberto

  • 0 in reply to Roberto S.
    TI__Intellectual 2530 points

    Snigdha,

    PoE isolation requirements are specified in the IEEE802.3at specification section 145.4.1.  These are isolation specifications for the PD, but I don’t think there are any isolation requirements for the PSE, though most customers use an isolated supply to avoid ground loop issues, especially during detection.

    One of these isolation tests must be passed:

    1.  1500Vrms at 60Hz for 60s

    2.  2250Vdc for 60s

    3.  Impulse testing at 1500V, 10/700us waveform, 10 times, 60s between pulses.

    These tests are specified in IEC60950 or IEC62368.

    As for shielding, Table 145-16 and section 145.2.10.5 give the ripple levels allowed on the PSE source.  There are four frequency ranges with corresponding peak to peak ripple allowed.

    Thanks,

    David