CY28SRC01
itance on each side of the crystal must be twice the specified
load capacitance (CL). While the capacitance on each side of
the crystal is in series with the crystal, trim capacitors
(Ce1,Ce2) should be calculated to provide equal capacitance
loading on both sides.
Use the following formulas to calculate the trim capacitor
values for Ce1 and Ce2.
Load Capacitance (each side)
Ce
= 2 * CL – (Cs + Ci)
Total Capacitance (as seen by the crystal)
CLe
CL....................................................Crystal load capacitance
CLe......................................... Actual loading seen by crystal
using standard value trim capacitors
Ce..................................................... External trim capacitors
Cs .............................................. Stray capacitance (terraced)
Ci ...........................................................Internal capacitance
(lead frame, bond wires etc.)
=
1
(
Ce1 + Cs1 + Ci1
+
1
1
Ce2 + Cs2 + Ci2
)
Rev 1.0, November 20, 2006
Page 6 of 9
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