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LM25183: can't pass radiated emission test

Ethan Liu
Intellectual 1445 points
Part Number: LM25183
Other Parts Discussed in Thread: LM25184, LM25184EVM-S12

Tool/software:

Hi team,

We use LM25183 in the fylback circuit, and we have been tested for CE and RE (level 5), and the RE test result exceeds the standard. Here are some questions we would like to confrim with you.


1: For the RE and CE tests of LM25183, can the demo pass? Especially RE (only CE test is included in the datasheet)
2: Many measures have been tried on site, but none of them have passed. Do we have any measures to pass the RE test?
3: If the LM25183 flyback solution is difficult to pass the level 5 test, it will be changed to Boost/buck+ push-pull circuit (SN6505 or 6507)?


Requirements: Input voltage 6-18V
Isolated output voltage: 24V
Output capacity: 110mA

Best regards!

Ethan

  • 0
    TI__Guru* 78380 points

    Hi Ethan,

    Could you share their emi spectrum and show in which frequency range it fails?  We also need to know the operating conditions, sch, and layout to take a review.

    Sorry I do not find the LM25183 RE results.  However, I found the RE results in the LM25184EVM-S12 User's Guide, and it passed RE of CISPR-25 Class5.  It does mentioned transformer was shielded.  The LM25183 is similar to the LM25184, and only difference is in their current limit thresholds.  The latter has higher current capability. 

    Thanks,

    Youhao

  • 0 in reply to Youhao Xi
    TI__Intellectual 1445 points

    Hi Youhao,

    The EMI spectrum and frequency range are shown as below.  

    The opearion conditions:  Input voltage: 6-18V
                                              Isolated output voltage: 24V
                                               Output current: 110mA

    The frequency range shown in the datashee (sent by you) is 30M-1G, which is not the frequency band we exceed the standard. In addition, the actual measured frequency of LM25183 is about 350K, so the risk of exceeding the standard at low frequency is greater.

    Ethan

  • 0 in reply to Ethan Liu
    TI__Mastermind 40040 points

    Hello Ethan,

    Engineer supporting this thread will answer tomorrow sometime.  Thanks.

    David.

  • 0 in reply to David Baba
    TI__Guru* 78380 points

    Hi Ethan,

    Thank you for the info. Could you tell which standard is this about?  Can you help me to get their schematic, and maybe layout, too?

    Regards,

    Youhao

  • 0 in reply to Youhao Xi
    TI__Guru* 78380 points

    Hi Ethan,

    Having not seen any updates from the customer, may I assume the issue is resolved so I can close the thread?  You are always welcome to re-open it by adding a new post, or start a new thread.

    Regards,

    Youhao