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LM74670-Q1: TIDA-00858 for anti-surge

Jerry Chen
Expert 5110 points
Part Number: LM74670-Q1
Other Parts Discussed in Thread: TIDA-00858

Hi,

I see the max input voltage of TIDA-00858 is 42V AC, so, as the Absolute Maximum Ratings in the LM74670 datasheet stated, the 42V from Cathode to Anode(continuous) is actually a AC value? That means the DC value can be 42Vx1.414 (or 45Vx1.414)?

From previous experience, my customer should use 100V diode for the bridge, because 100V is the minimum reverse voltage level that can survive a surge. The AC input range is just 24Vac, but a 3000V peak surge would still remain around 100V after passing a 58V TVS. Could you check if LM74670 can survive a 110V surge with 50us time duration? Any suggestion for this anti-surge design?

Thanks! 

   

  • 0
    TI__Expert 5940 points
    Jerry,

    42v is the 'peak' level of the AC voltage on the input. I think it may have been spec'd this way as 'AC' can mean different waveshapes other than pure sinewave. I can see the confusion as an AC/DC power designer myself in using 42v AC and having A = Anode and C = Cathode additional. Abs max 2ms rating is 45v with 42v continuous for reverse voltage Cathode (C) to Anode (A). So for a sinewave AC, the Vin AC should be 42/1.414 = ~ 29.7VAC RMS. A lower voltage TVS large enough to suppress (clamp and survive) the input energy from the surge would be needed.

    The CA rating isn't an issue since the body diode is present and the voltage would be passed along to the load.

    Brian
  • 0 in reply to Brian Daugherty
    TI__Expert 5110 points

    Thank you, Brian.

    My customer will design a full-bridge rectifier like TIDA-00858. M1 and M3 is conducting to pass the surge energy to load, but M2 and M4 have to bear the reverse high voltage. It seems negative for LM74610 for this full-bridge application.

    I'm looking at LM5050 with 75V (100V max). Before, we found LM5050 could pass the anti-surge in a telecom 48Vdc application. Can LM5050 be configured as a full-bridge rectifier as TIDA-00858?

    Thanks.