CY23FS08
Document #: 38-07518 Rev. *A
Page 8 of 12
Calculated value of the pullability range for the XTAL with
C0/C1 ratio of 200, 300 and 400 are shown in Table 3. For this
calculation Cl(min) = 8pF and Cl(max)= 32pF has been used.
Using a XTAL that has a nominal frequency specified at load
capacitance of 14pF, almost symmetrical pullability range has
been obtained.
Next, it is important to calculate the pullability range including
error tolerances. This would be the capture range of the input
reference frequency that the FailSafe device and XTAL combi-
nation would reliably span.
Calculating the capture range involves subtracting error
tolerances as follows:
Parameter........................................................ f error (ppm)
Manufacturing frequency tolerance ...................................15
Temperature stability ..........................................................30
Aging ................................................................................... 3
Board/trace variation ........................................................... 5
Total ....................................................................................53
Example: Capture Range for XTAL with C0/C1 Ratio of 200
Negative Capture Range= –385 ppm + 53 ppm = –332 ppm
Positive Capture Range = 333 ppm – 53 ppm = +280 ppm
It is important to note that the XTAL with lower C0/C1 ratio has
wider pullability/capture range as compared to the higher
C0/C1 ratio. This will help the user in selecting the appropriate
XTAL for use in the FailSafe application.
Table 3. Pullability Range from XTAL with Different C0/C1
Ratio
C0/C1 Ratio
Cload(min.)
Cload(max.)
Pullability
Range
200
8.0
32.0
–385 333
300
8.0
32.0
–256 222
400
8.0
32.0
–192 166
Absolute Maximum Conditions
Parameter
Description
Condition
Min.
Max.
Unit
VDD
Supply Voltage
–0.5
4.6
V
VIN
Input Voltage
Relative to VSS
–0.5
VDD+0.5
VDC
TS
Temperature, Storage
Non Functional
–65
+150
°C
TA
Temperature, Operating Ambient
Commercial Grade
0
70
°C
Industrial Grade
–40
85
°C
TJ
Temperature, Junction
Functional
125
°C
ESDHBM
ESD Protection (Human Body Model)
MIL-STD-883, Method 3015
2000
V
ØJC
Dissipation, Junction to Case
Mil-Spec 883E Method 1012.1
36.17
°C/W
ØJA
Dissipation, Junction to Ambient
JEDEC (JESD 51)
100.6
°C/W
UL–94
Flammability Rating
At 1/8 in.
V–0
MSL
Moisture Sensitivity Level
1
Multiple Supplies: The Voltage on any input or I/O pin cannot exceed the power pin during power-up. Power supply sequencing is NOT required.
Recommended Pullable Crystal Specifications[6]
Parameter
Name
Comments
Min.
Typ.
Max.
Unit
FNOM
Nominal crystal frequency
Parallel resonance, fundamental mode,
AT cut
8.00
–
30.00
MHz
CLNOM
Nominal load capacitance
–
14
–
pF
R1
Equivalent series resistance (ESR)
Fundamental mode
–
–
25
Ω
R3/R1
Ratio of third overtone mode ESR to
fundamental mode ESR
Ratio used because typical R1 values
are much less than the maximum spec
3–
–
DL
Crystal drive level
No external series resistor assumed
–
0.5
2
mW
F3SEPLI
Third overtone separation from 3*FNOM High side
300
–
–
ppm
F3SEPLO
Third overtone separation from 3*FNOM Low side
–
–
–150
ppm
C0
Crystal shunt capacitance
–
–
7
pF
C0/C1
Ratio of shunt to motional capacitance
180
–
250
C1
Crystal motional capacitance
14.4
18
21.6
fF
Note:
6.
Ecliptek ECX-5788-13.500M, ECX-5807-19.440M, ECX-5872-19.53125M, ECX-5806-18.432M, ECX-5808-27.000M, ECX-5884-17.664M,
ECX-5883-16.384M,ECX-5882-19.200M,ECX-5880-24.576M meet these specifications.
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