cy23fs04 Cypress Semiconductor Corporation., cy23fs04 Datasheet - Page 8

• Manufacturer Part Number: cy23fs04
• Description: 2.5v/ 3.3v Zero Delay Buffer
• Manufacturer: Cypress Semiconductor Corporation.

Document #: 38-07304 Rev. *C
Table 3. Pullability Range fro XTAL with Different C0/C1
Ratio
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) = 8 pF and Cl(max)= 32 pF has been used.
Using a XTAL that has a nominal frequency specified at load
capacitance of 14 pF, 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.
C0/C1 Ratio
200
300
400
-100.00
-200.00
-300.00
-400.00
Cload(min.) Cload(max.)
400.00
300.00
200.00
100.00
0.00
8.0
8.0
8.0
6
Figure 8. Frequency vs. Cload Behavior for Example XTAL
8 10 12 14 16 18 20 22 24 26 28 30 32 34
32.0
32.0
32.0
Pullability Range Vs. Cload
–385
–256
–192
Pullability
(Normalized to 14pF Cload)
Range
Cload (pF)
333
222
166
Calculating the capture range involves subtracting error toler-
ances 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.
C0/C1 = 200
C0/C1 = 300
C0/C1 = 400
CY23FS04
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