Overheated problem of K60

[wangfukai]

Hi all,

     I am using MK60FX512VLQ12 in bare-metal mode. Every 0.833ms it will perform ADC . The loop in the main() do some Key Scanning and

Uart Sending. No other features in its code. Now the K60 chip will be overheated(may be 60℃) after 20 minutes' running. If debug K60 with

J-link, it will be overheated(may be 90℃) in less time.

     The chip runs well and can be debugged.

     What could be the problem and how can I identify it?

Bests

Fukai from BeiJing

[chris_brown]

Hi Fukai,

What is the ambient temperature near the part? 

Can you measure the current draw of the part when this happens?

Can you also post a schematic?  At least a snippet of the device and the power capacitors and other power supply circuitry?  That may help to provide some clues. 

Thanks,

Chris

[wangfukai]

Hi Chris,

Thanks for your kind help firstly.

That's how the cpu board should be used, in a box with other boards. Initially, I guess the over heated problem

was caused by the  power board. There is a big AC/DC module on power board.

So I pluged the CPU board out and soldered a 5V power on LM1117 pin directly as showed after.

And the over heated problem still exist. The ambient temperature is 27℃ and we have an air-conditioner in our school lab

so this should not be the cause.

I measured current of the whole CPU  board and it is 0.341A.

There are four modules on the CPU board:  Internet port, RS485 port, EEPROM, IO port. But none of these modules were

used in the project code. The CPU only do A/D conversation every 0.833ms with the internal ADC.

Thanks

Fukai

[vicentegomez]

Hi

Would be possible that you send me your schematics?

Please check if you do not have any electrical short or wrong component?

What happens if you load a empty project, the board gets hot?

I believe that you are using a LQFP package, can you please check that there is not any solder short between the pins

Have a great day,
Vicente

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[wangfukai]

Hi Vicente,

       I soldered another board and no overheat problem occurred. So that MCU on the overheat  board

may has something wrong.

     I checked the MCU and no pins was shorted. And the MCU still can be linked with Jlink.

     So, it is strange. The temperature in the box which contains the MCU board is a little bit hot, So I guess

may that cause the MCU to be destroyed but not totally destroyed.

Regards.

Fukai

[vicentegomez]

Hi, you can check the impedance between the good part and the failed part, I do not know if this is possible but what happened if you place a new MCU on the failed board, I am thinking that the problem is on the board (hardware), probably a wrong or missing component. If you place a new MCU and the board still did not work, I will check the hardware.

Have a great day,
Vicente

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[wangfukai]

Hi Vicente,

Actually, the board was good in the beginning. And days later it went to wrong so I soldered another MCU on the board. It keeped well

for another days and then went wrong again.

So I suppose the box's high temperature  is the cause.

I chang another new board with new MCU and check what will happen.

Thank you,

Fukai

[daweiyou · Accepted solution]

Hi Fukai:

300mA current is large enough to make chip overheated.

Maybe something short, you could check every pin to clear the short pin to GND.

Do you use internal USB regulator module?

Dawei You（尤大为）

Mobile: +86 13675169919

[wangfukai]

Hi Dawei,

     I thought I find the problem. The box we use is made of metal and it let two boards be shorted.

Thanks.

Fukai