[LTC7801] Output capacitor issue

Question

Hello, 
 
 I designed several power supply converting 49V into 12V (7A) but output tantale capacitors are destroyed after power-up, do you know what happened? 
 
 Please find the design in attachment. PDF 
 The tantale capacitors are TR3D157K016C0075. 
 Beside, after removing them (leaving 3 ceramics 22uF), the design works well : 12V not load and 11.74V at 7A. But I cannot explain why when the load is around 1 or 2A, the voltage up to 13V. 
 
 Thank you for your help

Kurk · Accepted Answer

In the past when using 16V Tantalum capacitors on 12V outputs, I have seen surge failures due to current and voltage at the same time (constant current charge). Changing to 25V capacitors will likely solve the problem. I might also suggest looking at capacitors such as Panasonic TQC polymer Tantalum. Regarding output regulation, I am not sure. You could try forced continuous mode or remove the 240pF cap on FB and adjust ITH values, if necessary. Good Luck.

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[LTC7801] Output capacitor issue

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