SNLS614A September 2018 – December 2018 DP83869HM
A 25-MHz, parallel, 15-pF to 40-pF load crystal resonator should be used if a crystal source is desired. Figure 110 shows a typical connection for a crystal resonator circuit. The load capacitor values vary with the crystal vendors. Check with the vendor for the recommended loads.
As a starting point for evaluating the oscillator performance, the value of CL1 and CL2 should each be equal to 2x the specified load capacitance from the crystal vendor’s data sheet. For example, if the specified load capacitance of the crystal is 10 pF, set CL1 = CL2 = 20 pF. CL1, CL2 value may need to be adjusted based on the parasitic capacitance. Depending on the crystal drive level, R1 may or may not be needed.
Specification for 25-MHz crystal are listed in Table 97.
|Frequency Tolerance||Operational Temperature||±50||ppm|