Dear Team,
We connected the left Crystal in the figure below to XIN and Xout of 6214, and configured 22PF capacitors on the two pins of the crystal. Now we find that the crystal on some single boards cannot start to vibrate.
Our CDCI6214 firmware sets its Cxin_load to 5PF, as shown in Figure 3, it should be wrongly matched.
In the following formula, CL1 and CL2 are the matching capacitors on the crystal pins, Cic is the chip pins and internal capacitors, and Cstray is the capacitance of the wiring on the PCB:
CL = CL1 x CL2 / (CL1 + CL2) + Cstray+Cic
Now my question is:
1. How much is appropriate to estimate the wiring capacitance on the PCB? The wiring diagram is given on the right of Figure 1, and the line width is 5mil;
2. TICS provides a calculation method. Clext refers to a single value of CL1 or CL2, right? According to our schematic diagram, we configured it in Figure 4, please see if this configuration is correct?
Figure 1:
Figure 2:
Figure 3:
Figure 4:
Many Thanks,
Jimmy
