kevin amadiva

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9 years ago.

My FRDM-KL25Z is heating up and i cant even drop an Embed code to program it

I have been using the board for a few months now, am using it to control a bunch of stepper motors. but today, i noticed that some motors were not working, i removed all the connections to the board and in the process noticed that the region around the voltage regulator was heating up quickly when USB connected(with no connections made). i then tried to drop a binary file to reprogram, but that was not possible..... i have done some consultation, the response am getting is that my volt-regulator is faulty.... any advice please, or someone experienced such a problem...??

1 Answer

Ned Konz
9 years ago.

The voltage regulator U1 (a NCP1117ST33T3G) converts the 5V from either of the USB connectors (or the external 5-9V input) to 3.3V to run the processors. Depending on how you were powering the board and how the regulator failed, you may need a new board. These processors (the MK20DX128VFM5 debug processor and the MKL25Z128VLK4 target processor) both are rated for a maximum of 3.8V on their supply pins. If the voltage at TP7 (P3V3_VREG) is greater than 3.8V (or ever got that high), your processors may be damaged. The regulator is good to 20V on its inputs. However, if you were driving stepper motors off the same supply as the external voltage input to the board, it is possible that inductive transients could have caused spikes >20V on the power supply (this depends on your power supply and stepper driver circuitry).

I would test the voltage at TP7; if it's higher than 3.8V, I'd pitch the board and get a new one. If the voltage regulator failed shorted, the TP7 voltage will be less than a volt or so, and it is possible that the processors may have been spared. In that case, you could try replacing U1 with a new part. But given the $13 USD price of the board, it might be best to just replace the board.