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[blunone]

We have a custom design c5509a board. When we set the CLKMD register to 0x2512 to adjust the PLL frequency to 120 MHz , everything is ok but when we set the value to 0x2892 to adjust the PLL frequency to 204 MHz ( and we have to run the code at this speed) the code sometimes run but sometimes hangs on.

I saw some suggestions on internet to disable the CLKMD pin for PLL unstability situations. See below internet links for details

http://www.dsprelated.com/groups/c55x/show/979.php.

How CLKOUT disabling can influence the PLL stabiliy or unstability. And in detail do you have any ideas about this problem. We encounter the same problem in all of our new PCBs.

First I thought that our core voltage is not enough to run on this speed and increased it a little to 1.72Volt but the problem is still there.

12Mhz Oscillator clock is very good when I look with an oscilloscope.

The PCB has 8 layers ans as you figure I can not touch some of the DSP pins because it is BGA

Is there a problem on c5509a about the PLL or something.



Target : c5509a

Crystal : 12 Mhz

Emulator : xds510 usb plus CC Studio 3.1

DSP/BIOS was USED in the project

CLKMD value : 0x2892

PLL Freq = 204MHz

Used peripherals in design : EMIF for sdram, audio processing, SPI, I2C nearly all of the peripherals
waiting for your urgent reply



http://e2e.ti.com/forums/p/12457/48495.aspx#48495

http://www.dsprelated.com/groups/c55x/show/1947.php


http://e2e.ti.com/forums/p/12107/48499.aspx#48499


http://wiki.davincidsp.com/index.php?title=Preventing_EMI_Issues


http://www.dsp-bg.info/viewtopic.php?p=10345#10345