6 years, 8 months ago.

fried mbed - which part is it ?


I've fried my mbed :-( I've connected the wrong pin instead of Vin.

I can't identify the component part #

Here is a picture of it. /media/uploads/alainp/20130518_112405.jpg

Tip/advice about replacing it are welcome.



2 Answers

6 years, 8 months ago.

The resistor on top of it is 1.5kOhm, which according to the mbed schematics would probably mean it is a BSS84 transistor (PMOS).

All speculation next (and previous also btw): I think that is the one connected to the mini-USB adapter of the mbed. So if it is broken it could mean you cannot load new programs on it. But your old one should probably still run then.

Next would be the question if you can destroy it without destroying other components. Absolute maximum gate source voltage is +/- 20V for the transistor, and -50V for drain-source. For positive drain-source voltages it has a diode, so is current limitted. That means the most likely method to destroy it is by simply too high current levels, but it has a 1.5k resistor in series, so that isn't possible.

So yeah, unless I identified it wrong I have no idea how it can be broken :/. (Package does look cracked from the photo).

Accepted Answer
6 years, 8 months ago.

I had some smoke from it. I switched off the power quickly, but ... too late.

Your guess seems correct, only powering from USB seems broken :

- It's still running with (correctly plugged) power (+5V) applied to Vin. (simple test with blinking of LED1:4) - If I try to connect ONLY the USB, I see no sign of life (the led beetwen the "reset button" and "usb connector" stay off) - If I connect USB and +5V to Vin, everythings seems ok : program running, led on and I can reprogram thru USB.

I hope no other part has fried...