Dear TI Team,
We are working on a design for water metter with ESI and MSP430FR5989. We are having some problems and we want to check everything, so our PCB has a crystal that is on SLAA367, the CC7V-T1A-32.768KHZ-9PF-10PPM-TA-QC. I wanted to know if this configuration is right for this crystal and application.
The capacitors have been calculated as follow:
Recommended effective load capacitance values supported are 3.7 pF, 6 pF, 9 pF, and 12.5 pF. Maximum shunt capacitance of 1.6 pF. The PCB adds additional capacitance, so it must also be considered in the overall capacitance.
CL = (CIN + C1) x (C2 + COUT) / (CIN + C1 + C2 + COUT) + CStray
For CC7V-T1A-32.768KHZ-9PF-10PPM-TA-QC:
CL=9pF
C1=C2=C
For MSP430FR5989 and LFXT (page 41):
CIN=2pF
COUT=2pF
CStray=0.5pF
Result: 15 pF
More over, I provide you the layout of the crystal part:
Can someone confirm if this is right?
Best regards.
Samuel
