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LM2695: LM2695

Hussein A
Prodigy 80 points
Part Number: LM2695

Hi,

I take the low cost configuration design of LM2695 as reference for my application board, (Vin = 24V /Vout=10 Iout= 1.2 A same one in AN-1444 ). After first plug-in Vin=24VDC all good and (the consumption of my board 40mA in standby, then after 2-3 reset or plug-out and plug-in Vin, LM2695 is broken, I checked my design many times my deign all is ok, for the BOM, there is one modification the voltage divider on FB is 3K/1K, and the capacitor on output is low ESR same value 22uF, and I added a ressitor 2.2 ohms in serail, L=100uH/2A , and Diode Schottky 60V/2A.

But, I read again the datasheet, it is noted the capacitors C3 and C4 must be low ESR and C5 is recommended low ESR, but in my design they are not low ESR.

So my question if I change these capacitors (C3 = pin VCC, C4 = pin BST and C5 = Pin Vin) with other ones the same values and low ESR, could I fix this problem? for the capacitor C6=pin SS it isn't mandory to be low ESR?

BR

HA

  • 0
    TI__Guru 59335 points

    Hello

    It sounds like you may have some voltage transients that exceed the maximum input voltage of the device; either above 33V or a negative spike.

    The best way to tell is to monitor the input voltage with a 'scope while you apply power to the board.  You may need some kind of transient protection

    on the input, such as a TVS.

    Regarding the ceramic capacitors on VIN, VCC, and BST, they should be low ESR ceramics for best results.  However, another way to reduce transients and ringing on the input

    is to place an aluminium electrolytic capacitor in parallel with the ceramic input capacitor.  The moderate ESR of the electrolytic will help damp any transients on the input.

    The soft-start capacitor does not require low ESR.

    Thanks

  • 0 in reply to Frank De Stasi
    TI__Guru 59335 points

    Hello

    I will close this post because of inactivity.

    Thanks