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5/30/2017 8:45 AM
 

Hello,

 

We've noticed that we can easily kill the MP24833 at startup by connecting and disconnecting the input voltage multiple times. The circuit surrounding the IC is what is recommended. Is there a known problem and does the MP24833A fix this issue.

 

Thanks.

 

PRH

Metaphase

 
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5/30/2017 11:14 AM
 

Hi Phil,

 

MP24833A is a newer version of MP24833. It is recommended to use the la version (MP24833A) in a new design. However, the damage may not be related to the version of the IC. One thing you may want to look into is when input is connected, is there high input voltage induced by inrush current charging the input cap. The inrush can be high if input is hot plugged. Input voltage higher than the absolute maximum value of the spec may damage the IC.

 

Thanks,

Kevin

 

 
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6/5/2017 9:00 AM
 

Hey Kevin,

 

Thanks so much for the reply. Yes, I can see there would be an in-rush current to the input cap. That would occur if you're hot-plugging or not. But that in-rush would only have averse affects on the cap. I can't see a higher-than-normal voltage being generated that would kill the IC. Perhaps if the input wiring had a bit of inductance so that the input voltage rings up higher, but even then it wouldn't ring up higher than twice our 24VDC supply.

 

We use a few thousand of these chips per year and see a few percent fail.

 

We'll keep looking at our circuit, but I guess you're saying that the -A version of this chip didn't fix a known problem where the chip's input was blowing up.

 

Thanks.

 

PRH

 

 
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6/5/2017 10:44 AM
 

Hi Phil,

 

The input wire parasitic inductance, input cap size, and the speed of the hot plug all have contribution to the inrush current. There are couples ways that I can think of to suppress inrush current or potential high voltage stress on the IC.

 

1. Clamp input voltage by adding TVS on the input.

2. Add strapping resistor on EN pin, so the IC will start up after the input voltage is build up. It can avoid IC turning on at low Vin, which has higher inrush current.

3. MP24833A has lower current limit than MP24833, it can help to limit inrush current at start up.

 

Thanks,

Kevin

 

 

 
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