Burnt two MK60FN1M0VLQ12 when plug in USB port

[kakiayam]

Dear all,

I have connected the USB pins to the connector as detail in the image. But I burn the uC everytime I connect the USB port to a computer (host). I do not know what went wrong. As far as I am concern the uC needed the incoming Vbus 5V and regulate into the proper Vout to power the internal USB module of the uC.

But the problem was resolve when I replace the F8 ferrite bead with a 30R resistor. But I don't think this will solve the problem. Currently, I am not using the VOUT33 so loading at the output is not an issue. Was it due to the value of C32? The datasheet recommends a much larger cap (2uF), but surely, a lower cap should not cause it to load.

Please help and enlighten me on this. Thank you.

[bobpaddock]

I know this thread is old, however for future reference to anyone that comes across it, take look at Linear Tech's App Note #88:

"Ceramic Input Capacitors Can Cause Overvoltage Transients" by
Goran Perica.

http://cds.linear.com/docs/en/application-note/an88f.pdf

"A recent trend in the design of portable devices has been

to use ceramic capacitors to filter DC/DC converter inputs.

Ceramic capacitors are often chosen because of their

small size, low equivalent series resistance (ESR) and

high RMS current capability. Also, recently, designers have

been looking to ceramic capacitors due to shortages of

tantalum capacitors.

Unfortunately, using ceramic capacitors for input filtering

can cause problems. Applying a voltage step to a ceramic

capacitor causes a large current surge that stores energy

in the inductances of the power leads. A large voltage

spike is created when the stored energy is transferred

from these inductances into the ceramic capacitor. These

voltage spikes can easily be twice the amplitude of the

input voltage step. ... "

[Dekiru]

Hi,

I think that adding capacitors to power line and connect power line to pin 5 of U7 with reduce the effect of over-voltage transients occur on the USB power line when hot plugging, that may help to prevent the issue.

Of course choosing a higher serial resistance value at high frequency of ferrite will make a better result comparing to low value.

Regards

[CarlosCasillas · Accepted solution]

Hello,

The high level view of your hardware connections seems to be right if you have ensured that the pull-up resistors on D+ and D- are tied to 3.3V, and not 5V. However, you could refer to the USB connection of a Freescale Board (Freedom) which is also powered by the USB ports; on this board, the GND and VBUS signals from USB port areconnected to ferrites, but they have internal resistance of 330 ohm. You can review these details on Freedom´s schematic, available at the following link:

www.freescale.com/files/soft_dev_tools/hardware_tools/schematics/FRDM-KL25Z_SCH.pdf

Hope this information will be useful for you. Have a nice day.

[ec0359]

Hello,

I have the same problem with my prototype card with PK60N512VLL100.  when i plug the USB link, the uC is hot, and the power current from the USB connector is about 110 mA (i add 33 Ohm on this line). The VOUT33 is 0 V.

The decoupling capacitor is 4,7 uF on VOUT33.

And the USB-Device demo don't work.

     Thank you if somebody have idea.