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SC4501 boost converter shorting out

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snipex

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Hi!

I'm currently working on a circuit that has a SC4501 boost converter IC on PCB.
I was testing the PCB yesterday and I shorted the input of the IC. It then started to draw more current as if it was shorted out.
I tested what was wrong and it seems that the VCC pin has fried.
The input voltage at the time of testing was 7V.
I then noticed that I forgot the input capacitor. Could this be a problem?
My theory is that the inductor caused a negative voltage on VCC pin and that fried it.

My circuit is the same as in the datasheet minus the input capacitor.
 

Hi,

I then noticed that I forgot the input capacitor. Could this be a problem?
Click to expand...

Capacitors in pulsed power applications ARE necessary. They are not optional!
It is not just a marketing trick when they say you should use them.

Klaus
 

I know now that they are necessary. I have 3 big electrolytic capacitor on my board also but they are not so close to the switch IC. I thought that maybe I could get away by just using the electrolytic.
So do you know exactly what happened here?
 

Hi,

the datasheet clearly tells to put a ceramic capacitor close to the IN pin.
It also tells it reduces EMI as well as voltage spikes.

An electrolytic capacitor is not suitable, because it can not thandle the high frequency peaks.

no capacitor --> high voltage peaks --> kills the IC.

**********

May I ask, why you didn´t read the datasheet on your own? It´s easier for you when I read the datasheet?

Klaus
 

IC should not short circuit if we are not connect input capacitor(This may effect the performance of the circuit)
Check 1) Ground is connected
2) PCB Track short circuit between pin 5 and pin 6
3) Feed back(pins -2) connected properly
 

Hi,

IC should not short circuit if we are not connect input capacitor
Click to expand...
I don´t agree.

The high voltage peaks destroy the isolation barrier within the IC... until it becomes conductive = short circuit.
It may short input to output or it may short input to GND.

Klaus
 

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