PRELIMINARY
CY28443-2
Document #: 38-07718 Rev. *B
Page 10 of 24
The CY28443-2 requires a Parallel Resonance Crystal.
Substituting a series resonance crystal will cause the
CY28443-2 to operate at the wrong frequency and violate the
ppm specification. For most applications there is a 300-ppm
frequency shift between series and parallel crystals due to
incorrect loading.
Crystal Loading
Crystal loading plays a critical role in achieving low ppm perfor-
mance. To realize low ppm performance, the total capacitance
the crystal will see must be considered to calculate the appro-
priate capacitive loading (CL).
Figure 1 shows a typical crystal configuration using the two
trim capacitors. An important clarification for the following
discussion is that the trim capacitors are in series with the
crystal not parallel. It’s a common misconception that load
capacitors are in parallel with the crystal and should be
approximately equal to the load capacitance of the crystal.
This is not true.
3
0
CLKREQ#A
SRC[T/C]4 Control
0 = SRC[T/C]4 not stoppable by CLKREQ#A
1 = SRC[T/C]4 stoppable by CLKREQ#A
2
0
CLKREQ#A
SRC[T/C]3 Control
0 = SRC[T/C]3 not stoppable by CLKREQ#A
1 = SRC[T/C]3 stoppable by CLKREQ#A
1
0
CLKREQ#A
SRC[T/C]2 Control
0 = SRC[T/C]2 not stoppable by CLKREQ#A
1 = SRC[T/C]2 stoppable by CLKREQ#A
0
0
CLKREQ#A
SRC[T/C]1 Control
0 = SRC[T/C]1 not stoppable by CLKREQ#A
1 = SRC[T/C]1 stoppable by CLKREQ#A
Byte 14: Control Register 14 (continued)
Bit
@Pup
Name
Description
Byte 15: Control Register 15
Bit
@Pup
Name
Description
7
1
CLKREQ#B
SRC[T/C]8 Control
0 = SRC[T/C]8 not stoppable by CLKREQ#B
1 = SRC[T/C]8 stoppable by CLKREQ#B
6
0
RESERVED
RESERVED
5
0
RESERVED
RESERVED
4
0
CLKREQ#B
SRC[T/C]5 Control
0 = SRC[T/C]5 not stoppable by CLKREQ#B
1= SRC[T/C]5 stoppable by CLKREQ#B
3
0
CLKREQ#B
SRC[T/C]4 Control
0 = SRC[T/C]4 not stoppable by CLKREQ#B
1= SRC[T/C]4 stoppable by CLKREQ#B
2
0
CLKREQ#B
SRC[T/C]3 Control
0 = SRC[T/C]3 not stoppable by CLKREQ#B
1= SRC[T/C]3 stoppable by CLKREQ#B
1
0
CLKREQ#B
SRC[T/C]2 Control
0 = SRC[T/C]2 not stoppable by CLKREQ#B
1= SRC[T/C]2 stoppable by CLKREQ#B
0
0
CLKREQ#B
SRC[T/C]1 Control
0 = SRC[T/C]1 not stoppable by CLKREQ#B
1= SRC[T/C]1 stoppable by CLKREQ#B
Table 5. Crystal Recommendations
Frequency
(Fund)
Cut
Loading
Load Cap
Drive
(max.)
Shunt Cap
(max.)
Motional
(max.)
Tolerance
(max.)
Stability
(max.)
Aging
(max.)
14.31818 MHz
AT
Parallel
20 pF
0.1 mW
5 pF
0.016 pF
35 ppm
30 ppm
5 ppm
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