Other Parts Discussed in Thread: , TIDA-00646, TIDA-01519, TIDA-01476, TIDA-00489, TIDA-00488, TIDA-00838
Hello.
In CC1310 datasheet (SWRS181C) on paragraph 5.19.3.2 noted that crystal load capacitance should be in range 6-12 pF. On the dev boards CC1310EM-7XD-7793 and LAUNCHXL-CC1310 TI engineers used crystal 32768Hz with CL=7pF (FC-135 32.7680KA-AG0) which corresponds to the datasheet. External crystal capacitors are 12pF, and from that we can make conclusion that TI took Cstray = 1 pF in their calculations.
However, on most of the TI dev boards (TIDA-01519, TIDA-01476, TIDA-00488, TIDA-00489, TIDA-00646, TIDA-00838 ), used crystal FC-12M 32.7680KA-A3 with CL = 12.5pF, which slightly exceeds the datasheet MAX value of 12 pF.
And more than that, on this boards external crystal capacitors are also 12pF, however this equation:
CL = (C1 * C2) / (C1 + C2) + Cstray
gives us C1, C2 = 22pF.
This is pretty confusing.
Can anyone comment on this?
