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input ceramic Capacitor short for Li Ion charger ckt

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tiwari.sachin

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Below is SCH for li ion 2 cell charging. Its working fine but sometimes the CAP showed in sch burns/shows short. Replacing it works.

What could be causing this.

I am not sure if it burns at the instant i try to connect 9.6V which is ON first

or battery voltage and input 9.6V. As C8 would already be charged by battery voltage and suddenly connecting 9.6V has issues

or its the inductor.

I tried probing at C8 point, it shows 8V (Battery Voltage) and jumps to 9.4 or 9.5V when i supply input voltage for charging. I dint observe any spikes.

Why are the possibilities for capacitor to burn/short

Charging.png
 

Hi,

Please post the exact type of capacitor. Manufacturer and the exact code.

I hope you didn't buy from any unreliable source.

Klaus
 

Hi,

According datasheet there is a 100nF capacitor. This one should be as close as possible connected at the IC.
A 100nF capacitor has less stray inductance than your 10uF one.
Depending on PCB layout this may cause ringing.

Without seeing the layout it is hard to say.
Indeed I'd say it is not very likely that this may cause the 10uF capacitor to fail.

16V DC rated capacitors are the minimum for this 10V switching node.
Datasheet says to use the highest possible voltage rating at those capacitors. Whatever that means.

Klaus
 

Below is routing for diode and cap.

I am changing to a 0.1uF/50V part and checking. but the burn or short is random and i donot know when it happens (I am unable to recreate the cause as i dont know one yet)

Diode_Cap Flow.png
 

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