Post Go back to editing

TMC9660-3PH-EVKIT - TMC9660-STP-EVKIT : external crystal oscillator

Category: Hardware
Product Number: TMC9660
On the evaluation boards for the TMC9660 (STEPPER + 3-PHASE) a 16MHz 12pF crystal is used.
According to the BOM X301 "Jauch Quartz Q 16,0-JXS32-12-10/15-T1-WA-LF" is used. This is a 16MHz 12pF crystal.
If we assume a stray capacitance of Cs=3pF, and a load capacitance of CL=12pF, with the following equation, we should add C1=C2=18pF.


On the evaluation board only 9pF was used for C301 & C302. On our circuit board with slightly shorter traces (less capacitance), the crystal fails to start up using 9pF (works with 18pF).
Are my calculations correct? Has anyone tried to actually use the external oscillator on the evaluation baords?

In the datasheet there is the recommandation to use a crystal of ESR <70Ohm and CL=9pF running at 16MHz.
Is this recommandation correct and a crystal with 9pF would perform better or should we stick to the 12pF crystal?

BR
Gabriel
Parents
  • Die Fragen wurden nun intern an einen Kollegen weitergereicht - da es sich um einen recht neuen und hochkomplexen Baustein handelt, gibt es leider noch kein entsprechend geschultes Supporter-Team wie bei unseren anderen Produkten. 

    This is very valuable to us. 

     

    I forwarded this request to the colleague who finally designed the oscillator circuit, just to be sure. She will take care, that our TMC9660 EVAL-BOARD BOM be corrected - exactly in the way that you write. 

     

    She also gave the following hint:

    During the bench evaluation, we evaluate with 9pF assuming that we have some stray capacitance of Cs=3pF, you can use 12pF load cap and please activate the XTAL_BOOST to provide a boost current to the crystal to start up, for 16MHz the configuration on the CLK_CTRL_SOURCE is h36. The boost current automatically disables after start-up. The boost current ensures start up also with higher loads.

Reply
  • Die Fragen wurden nun intern an einen Kollegen weitergereicht - da es sich um einen recht neuen und hochkomplexen Baustein handelt, gibt es leider noch kein entsprechend geschultes Supporter-Team wie bei unseren anderen Produkten. 

    This is very valuable to us. 

     

    I forwarded this request to the colleague who finally designed the oscillator circuit, just to be sure. She will take care, that our TMC9660 EVAL-BOARD BOM be corrected - exactly in the way that you write. 

     

    She also gave the following hint:

    During the bench evaluation, we evaluate with 9pF assuming that we have some stray capacitance of Cs=3pF, you can use 12pF load cap and please activate the XTAL_BOOST to provide a boost current to the crystal to start up, for 16MHz the configuration on the CLK_CTRL_SOURCE is h36. The boost current automatically disables after start-up. The boost current ensures start up also with higher loads.

Children
No Data

Before You Switch


Switching languages will make ADI Explorer unavailable. Resume your session by switching back to English and reopening ADI Explorer.