CY28409
Byte 6: Control Register 6
Bit
7
6
5
@Pup
0
0
0
Reserved
Reserved
CPUC0, CPUT0
CPUC1, CPUT1
CPUC2, CPUT2
SRCT, SRCC
Reserved
PCIF
PCI
3V66
SRCT,SRCC
CPUT_ITP,CPUC_ITP
REF_1
REF_0
Name
Reserved, Set = 0
Reserved, Set = 0
FS_A & FS_B Operation
0 = Normal, 1 = Test mode
SRC Frequency Select
0 = 100 MHz, 1 = 200 MHz
Reserved, Set = 0
Spread Spectrum Enable
0 = Spread Off, 1 = Spread On
Description
4
3
2
0
0
0
1
0
1
1
REF_1 Output Enable
0 = Disabled, 1 = Enabled
REF_0 Output Enable
0 = Disabled, 1 = Enabled
Byte 7: Vendor ID
Bit
7
6
5
4
3
2
1
0
@Pup
0
1
0
0
1
0
0
0
Name
Revision ID Bit 3
Revision ID Bit 2
Revision ID Bit 1
Revision ID Bit 0
Vendor ID Bit 3
Vendor ID Bit 2
Vendor ID Bit 1
Vendor ID Bit 0
Revision ID Bit 3
Revision ID Bit 2
Revision ID Bit 1
Revision ID Bit 0
Vendor ID Bit 3
Vendor ID Bit 2
Vendor ID Bit 1
Vendor ID Bit 0
Description
Table 6. Crystal Recommendations
Frequency
(Fund)
14.31818 MHz
Cut
AT
Loading Load Cap
Parallel
20 pF
Drive
(max.)
0.1 mW
Shunt Cap
(max.)
5 pF
Motional
(max.)
0.016 pF
Tolerance
(max.)
50 ppm
Stability
(max.)
50 ppm
Aging
(max.)
5 ppm
Crystal Recommendations
The CY28409 requires a
Parallel Resonance Crystal.
Substituting a series resonance crystal will cause the
CY28409 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.
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.
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. Crystal Capacitive Clarification
Rev 1.0, November 22, 2006
Page 7 of 16
SPECTRALINEAR [ SPECTRALINEAR INC ]
