MOSFET short circuited

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MOSFET short circuited

Postby tiagosantos » Thu Jan 28, 2010 2:08 am

Hello folks,

I've been trying to drive a LUXEON REBEL WHITE LED with Power PSoC CY8CLED04D01 without success.
Every time I use more than 2 channels one randonly or 2 .. or 3 or 4. channes of the mosfet get short circuited.
I mean the leds turns ON even though the driver circuit is off.
I checked with a multimeter and it's Drain pin is short circuited with Source pin.
I made my own PCB layout following the AN rules for PCB and I'm using the same schematics as one of the reference designs.
(attached to this message)

I limited the current flow of the power source I'm using to this circuit at 200mA.
So it's very strange to see this MOSFET damaged when not even 10% of its driver capacity was reached.

Thanks in advance.
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tiagosantos
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Re: MOSFET short circuited

Postby yzr » Sun Jan 31, 2010 8:42 pm

Hello,
Are you using the internal switching regulator? If you are not, and making use of an external 5V source, then make sure that the regulator is disabled in software.
This option appears in the bottom of available global parameters.

If the above comment is not applicable or does not fix the issue, then, are you using one of the internal FETs or bringing the gate driver signal to an external FET?
Please send me a PM or email if you are interested in having Cypress review both the schematic and layout files for you.

Best Regards
Rakesh
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