CY28435
Byte 14: Control Register 14 (continued)
Bit
@Pup
Name
Description
1
1
PCIF
Free running 33-MHz Output Drive Strength
0 = 2x, 1 = 1x
0
0
Recovery_N8
Watchdog Recovery Bit
Byte 15: Control Register 15
Bit
7
@Pup
Name
Description
Watchdog Recovery Bit
Watchdog Recovery Bit
Watchdog Recovery Bit
Watchdog Recovery Bit
Watchdog Recovery Bit
Watchdog Recovery Bit
Watchdog Recovery Bit
Watchdog Recovery Bit
0
0
0
0
0
0
0
0
Recovery N7
Recovery N6
Recovery N5
Recovery N4
Recovery N3
Recovery N2
Recovery N1
Recovery N0
6
5
4
3
2
1
0
Byte 16: Control Register 16
Bit
@Pup
Name
Description
7
1
REF1
REF1 Output Enable
0 = Disable, 1 = Enable
6
5
1
0
USB48_1
USB48_1 Output Enable
0 = Disable, 1 = Enable
SRC_FREQ_SEL
SRC Frequency selection
0: SRC frequency is selected via the FSE pin
1: SRC frequency is initially set to 167 MHz.
4
3
0
0
RESERVED
SRC_SATA
RESERVED, Set = 0
SATA PLL Spread Spectrum Enable
0 = Spread off, 1 = Spread on
2
1
0
0
0
1
Prog_SRC_EN
Prog_CPU_EN
Programmable SRC frequency enable
0 = disabled, 1 = enabled.
Programmable CPU frequency enable
0 = disabled, 1 = enabled.
Watchdog Autorecovery Watchdog Autorecovery Mode
0 = Disable (Manual), 1= Enable (Auto)
Crystal Recommendations
Crystal Loading
The CY28435 requires a Parallel Resonance Crystal. Substi-
tuting a series resonance crystal will cause the CY28435 to
operate at the wrong frequency and violate the ppm specifi-
cation. For most applications there is a 300-ppm frequency
shift between series and parallel crystals due to incorrect
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 2 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.
Table 4. Crystal Recommendations
Frequency
(Fund)
Drive
(max.)
Shunt Cap Motional
(max.)
Tolerance
(max.)
Stability
(max.)
Aging
(max.)
Cut
Loading Load Cap
Parallel 20 pF
(max.)
14.31818 MHz
AT
0.1 mW
5 pF
0.016 pF
35 ppm
30 ppm
5 ppm
Rev 1.0,November 20, 2006
Page 10 of 22
SPECTRALINEAR [ SPECTRALINEAR INC ]
