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florian239955_stm1_stmicro_com
florian239955_stm1_stmicro_com
Associate
June 26, 2018
Solved

STM32F769 overheating problem

  • June 26, 2018
  • 4 replies
  • 2089 views
Posted on June 26, 2018 at 20:23

Hello, I have a PCB with LCD, SD-Ram, QSPI, CAN bus, SD card and everything works fine.

I use a STM32F769Bi (208pins LQFP).

Now I think the temp of the STM32F7 is very high (80-85deg).

Normally I work with Stm32f103 and have no temp problems.

(practically no temperature increase).

Does anyone have experience how much temperature is ok or do I have a PCB problem?

#stm32f768 #heat-problem
This topic has been closed for replies.
Best answer by STOne-32
Posted on June 26, 2018 at 23:09

Dear Gentleman,

That  behavior is not normal and you should have an issue somewhere. Having a temp offset of 50 between TC ( case) @82 and 32@ board .  That means more than 1W of PD ( Power dissipation) which is exceeding 1053mW of our LQFP208 package !  Please check your PCB , software configuration of I/Os , short cuts. Etc.

Good luck and let us know.

Cheers,

STOne-32

4 replies

Tesla DeLorean
Tesla DeLorean
Guru
June 26, 2018
Posted on June 26, 2018 at 21:21

Sorry don't have a thermal camera, perhaps you can do a comparative loading test with a F7 NUCLEO or DISCO board.

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STOne-32
STOne-32Best answer
ST Technical Moderator
June 26, 2018
Posted on June 26, 2018 at 23:09

Dear Gentleman,

That  behavior is not normal and you should have an issue somewhere. Having a temp offset of 50 between TC ( case) @82 and 32@ board .  That means more than 1W of PD ( Power dissipation) which is exceeding 1053mW of our LQFP208 package !  Please check your PCB , software configuration of I/Os , short cuts. Etc.

Good luck and let us know.

Cheers,

STOne-32

Vitaliy Chernobay
Vitaliy Chernobay
Senior
June 26, 2018
Posted on June 26, 2018 at 23:49

probably short cuts of output pin

T J
T J
Senior III
June 27, 2018
Posted on June 27, 2018 at 03:12

Of course its going to get hot.

with LCD and SDRAM, you are pounding the bus matrices.

is it your custom board ?

easy fix use a heatsink, biggest possible within the package

The proper fix is inline resistors on every high frequency line:

      data/address lines and Qspi lines ( nSS not needed)

      LCD too maybe... definately the LCD clock pin

I use 27R or 33R, upto 100R should be ok.

These are 4x33R packs. like this one

https://www.digikey.com/product-detail/en/rohm-semiconductor/MNR04MRAPJ300/RHM1349TR-ND/4083230

 

The advice is to place the resistor as far away from the processor as possible.

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