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TIDA-01411: Surge protection - MOVs or Thyristors

Parthan Mohan
Prodigy 70 points
Part Number: TIDA-01411

I need to implement the IEC61000-4-5 (Common mode：2kV, normal mode：1kV) surge protection to my PoE PD

I will be looking at a level 4 protection range.

In TIDA-01411 reference design MOVs has been used for the surge protection

I have seen other application where TVS thyristors has been for the surge protection 

which is better thyristor or metal oxide varistors for lightning surge protection ?




  • 0
    TI__Genius 15655 points

    Hi Parthan,

    The TVS is usually placed across the input rails of the PD/DC-DC controller IC, should be included as a minimum requirement for all of the test levels. MOVs are used to clamp the surge voltage to earth ground, creating an added current path to return the surge current to the generator when the MOVs are activated. Each MOV needs to be capable of handling the combined currents of two lines. The actual need for the MOVs depends on the test level requirement and the withstand strength of the PD. The MOVs may not be required for test levels up to 1000 V, since the IEEE 802.3 standard specifies that the PD must have a withstand strength of at least 1500 VPK for the 10/700 µs impulse test. If the PD has instead been designed with a withstand rating per the 1500-VRMS or 2250-VDC rating specified in the IEEE 802.3 standard, then the MOVs may not be required for the 2000-V test level. The MOVs would definitely be required to meet test levels that exceed the withstand strength of the PD, which in most cases includes the 4000-V test level. Although the MOVs might not be required to meet some of the lower test levels, implementing them for all conditions can lessen the stress on sensitive components within the DC-DC converter and add to the overall robustness of the PD. The intended operating environment of the PD should be considered to assess the potential risk of damage and downtime of the PD equipment versus the added cost of the protection.

    More detailed information can be found in this app note for PD lightning surge protection designs: www.ti.com/.../slua736.pdf. Thanks.

    Best regards,

    Penny