Electrical – Wrong way usb connexion to MCP73831 lipo charger


I have a problem with my mcp73831 lipo charger; i have a connection with two neodym magnet connected to usb in one side and my circuit with the MCP73.. in the other side.

There is no problem when i respect the connexion polarity (5v from usb -> to 5v mcp73831 and Gnd from usb -> to Gnd mcp73831).

But, when i change the polarity, the mcp73831 burned… and i was wondering why this IC is not protected from wrong polarity connection ..

So, i want to add a diode with low drop voltage connected to 5v from mcp73831, in forward-biased mode.

I add two circuits to better understand the problem.

Without diode:

enter image description here

And with diode :

enter image description here

Am I allowed to put a diode between the MCP73, would the voltage drop of the diode be too much?

Best Answer

Yes, this kind of protection against a badly designed connector is fairly usual. The only thing would be to place the diode BEFORE C3 capacitor, to make sure the input source (capacitive) impedance is within recommended value, to avoid potential instability of the linear regulator.

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