FX3 Crystal Compatibility

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Anonymous
Not applicable
        Hi. My Problem is that my FX3 board wont be displayed in the Control Center. On the Pins 1 and 3 of my Crystal (ABM8 19.2) are no typical Clock signals visible (there is nearly no Signal, yust a very Little offset). Because of that Ive removed the Crystal and used a function Generator instead. With this method the Board can be seen in the control Center and i can Transfer data as well. My question is, if my Crystal could be incompatible or if there could be any other typical flaw in my board which could cause this Problem. Here is the Datasheet of my Crystal. Ive used two 15pF capacitors as C1 and C2. http://www.mouser.com/ds/2/3/abm8-16794.pdf Ive used an incorrect Footprint in my PCB Design, so I dont have the Crystal connected to the Board Pins directly. They are connected to the Board via 15mm Long wires instead. Thanks for your helb.   
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4 Replies
Anonymous
Not applicable

 Hi ,

   

 

   

In the datasheet of crystal the load capacitance value is not specified at particualr frequency.Please check with manufacturer about the CL at 19.2Mhz.

   

 

   

Refer the app note http://www.cypress.com/?docID=50685(section crystal) for calculating the  load caps as per the crystal specs 

   

 

   

Regards,

   

Vikas.

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Anonymous
Not applicable

 This may also be because of the wire you have connected. As you are sending the signals through long wires the signal may get distorted. By probbing the pins of FX3, you can check whether you are receiving the signal and also its quality. 

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Anonymous
Not applicable

Ist not a Problem of the Quality of the Signal, because there is no Signal on the Crystal Pins at all.

   

 

   

I've checked the Hardware Design Guidlines and used the formula to calculate the C1 and C2 value. (18pF= [30x30]/[30+30] +3)

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DaAh_296361
Level 1
Level 1

 Hi,

   

Did you ever solve this problem? I am testing out a custom PCB I made for the FX3 and I don't see any clock being generated by my 19.2 crystal.

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