mirror of
git://projects.qi-hardware.com/ben-wpan.git
synced 2024-12-24 00:54:15 +02:00
2406f674f5
- atrf/ecn/ecn0001.txt, atrf/ecn/ecn0002.txt: changed ECN format to separate title from body by two blank lines and, where a conclusions has been reached, put it into a section separated from body also by two blank lines - atrf/ecn/ecn0003.txt: researched balun design and availability - atrf/ecn/INDEX, atrf/ecn/ecn0004.txt: new ECN: Take into account layout considerations for RF - TODO: removed item covered by ECN0002 - TODO: removed bug fixed in f32xbase commit 79396b17772639cea615d1c87870d55f08c11850 - TODO: added reference to ECN0003
49 lines
1.4 KiB
Plaintext
49 lines
1.4 KiB
Plaintext
Add load capacitors to 16 MHz crystal (C14, C15)
|
|
|
|
|
|
The crystal has a specified load capacitance of 8 pF. The AT86RF230 has
|
|
an internal capacitor array that can be trimmed in 16 steps from 0 pF to
|
|
4.5 pF.
|
|
|
|
The crystal has a nominal tolerance of 15 ppm at 25 C plus a temperature
|
|
tolerance of 15 ppm. The following deviations from 1 MHz at CLKM were
|
|
measured with the CNTR board, roughly at 20-25 C:
|
|
|
|
Board Error Meas. accuracy C14/C15 Trim
|
|
(f, ppm) (ppm, nom.) (pF) (pF)
|
|
--------------- --------------- --------------- ------------ --------
|
|
2, "orange" +268 99.6 NC 0
|
|
+266 99.5 NC 0
|
|
+266 40.0 NC 0
|
|
+148 99.8 NC 3.0
|
|
+147 99.7 NC 3.0
|
|
+147 40.0 NC 3.0
|
|
+111 100.0 NC 4.5
|
|
+110 99.8 NC 4.5
|
|
- 13 99.9 15 0
|
|
- 14 100.0 15 0
|
|
+ 11 99.9 12 0
|
|
+ 11 99.6 12 0
|
|
(cleanup) + 14 100.0 12 0
|
|
+ 14 100.0 12 0
|
|
|
|
1, "red" +263 99.7 NC 0
|
|
+263 100.0 NC 0
|
|
+107 99.3 NC 4.5
|
|
+108 100.0 NC 4.5
|
|
+ 24 99.8 10 0
|
|
+ 24 100.0 10 0
|
|
- 9 99.7 10 4.5
|
|
- 9 100.0 10 4.5
|
|
(cleanup) + 14 100.0 12 0
|
|
+ 14 100.0 12 0
|
|
|
|
(Multiple measurements to assess CNTR performance and drift. Note that
|
|
CNTR measurements are repeatable within 1 ppm, so the nominal accuracy
|
|
appears to be far too pessimistic.)
|
|
|
|
|
|
Conclusion: these measurements suggest that, combined with parasitic
|
|
capacitance, load capacitors of 12 pF make the crystal roughly half the
|
|
trim range faster than 16 MHz.
|