cy23fs04 Cypress Semiconductor Corporation., cy23fs04 Datasheet - Page 3

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

Document #: 38-07304 Rev. *C
Table 2. FailSafe Timing Table
In this mode, should the reference frequency fail (i.e. stop or
disappear), the DCXO maintains its last setting and a flag
signal (FAIL#/SAFE) is set to indicate failure of the reference
clock.
The CY23FS04 provides 2 select bits, S1 through S2 to control
the reference to crystal frequency ratio. The DCXO is internally
tuned to the phase and frequency of the external reference
Parameter
t
t
FSH
FSL
Figure 3. FailSafe Timing Diagram: Input Reference Slowly Drifting Out of FailSafe Capture Range
Fail#/Safe Assert Delay
Fail#/Safe De-assert Delay
Fail#/Safe
Reference
Reference Off
Output
Description
t
t
F S L ( m a x )
F S H ( m in )
t
FSL
Figure 2. Fail#/Safe Timing Formula
Measured at 80% to 20%, Load = 15 pF
Measured at 80% to 20%, Load = 15 pF
n
= 1 2
= 2
=
F
F
X T A L
R E F
(
(
t
t
= 4
R E F
R E F
Conditions
x n
x n
( in a b o v e e x a m p le )
only when the reference frequency divided by this ratio is
within the DCXO capture range. If the frequency is out of
range, a flag will be set on the FAIL#/SAFE pin notifying the
system that the selected reference is not valid. If the reference
moves in range, then the flag will be cleared, indicating to the
system that the selected reference is valid.
)
)
+
+
t
FSH
2 5 n s
2 5 n s
See Figure 2
Min.
Output + 300 ppm
Output - 300 ppm
Reference + 300 ppm
Reference - 300 ppm
Time
See Figure 2
Max.
CY23FS04
Page 3 of 12
Unit
ns
ns
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