AnsweredAssumed Answered

i.MX28 Power and Crystal problem

Question asked by Sebastien Picard on Aug 14, 2014
Latest reply on Aug 14, 2014 by Yuri Muhin

Hi all,

I'm currently debbuging a custom board based on the imx28evk schematic using an i.MX287. I'm using u-boot 2014-07 on a SD Card, and everything work fine on the imx28evk.

 

On my custom board, u-boot is not working, but i'm able to print debug info from spl_boot.c. After that, nothing. The baudrate on the DUART is around 100000 bauds on my board instead of 115200 on the evk (with the same sd card).

 

After reviewing my schematic, i've found that VDDIO33_EMI is connected to VDDIO_1V8 instead of VDDIO_3V3. Since this trace is under the imx28, I would like to confirm that my problems are related to this before making a new board.

 

When I probe the VDDIO_3V3 and VDDIO_1V8 rails, I measure a clean 3.3V and 1.8V. On the VDDIO33_EMI pin, I measure 1.8V. I can't find info in the datasheets about the difference between VDDIO33_x pins and VDDIO33_EMI pin. Are they link together internally?

 

The VDD4P2 linreg seems to start, but fall to 0V after 1s. My board is powered only by a 5V reg and the LI-ON_BATTERY net is not connected to an external regulator.

 

When I boot the EVK without the SD Card and I probe the crystal, I can see a clean 24MHz with a 500mVDC offset. When I boot my custom board (without the SD card), I see a flat 1VDC for about 2s, and then only 500mVDC. I'm using a C0603C180J5GACTU crystal (which seem very similar to the one on the evk: CS10-24.000MABJ-UT) with 18pf capacitors.

 

Do you think that all thoses issues are related to the VDDIO33_EMI wrong connection?

 

Thanks for you help.

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