CY26049-36
Document #: 38-07415 Rev. *C
Page 2 of 7
Functional Description
CY26049 is a FailSafe frequency synthesizer with a reference
clock input and three clock outputs. The device provides an
optimum solution for applications where continuous operation
is required in the event of a primary clock failure. The
continuous, glitch-free operation is achieved by using a DCXO
which serves as a primary clock source. The FailSafe control
circuit synchronizes the DCXO with the reference as long as
the reference is within the pull range of the crystal.
In the event of a reference clock failure the DCXO maintains
the last frequency and phase information of the reference
clock. The unique feature of the CY26049-36 is that the DCXO
is in fact the primary clocking source. When the reference
clock is restored, the DCXO automatically re-synchronizes to
the reference. The status of the reference clock input, as
detected by the CY26049-36, is reported by the SAFE pin.
In the buffer mode (FS3:FS0 = 1110 or 1111), the CY26049-36
can be used as a jitter attenuator. In this mode, extensive jitter
on the input clock will be “filtered”, resulting in a low-jitter
output clock.
Pin Definitions
Pin Name Pin Number
Pin Description
ICLK
1
Reference Input Clock; 8 kHz or 10 to 60 MHz.
8K
2
Clock Output; 8 kHz or high impedance in buffer mode.
FS1
3
Frequency Select 1; Determines CLK outputs per Table 1.
FS2
4
Frequency Select 2; Determines CLK outputs per Table 1.
VDD
5
Voltage Supply; 3.3V.
VSS
6
Ground
CLK/2
7
Clock Output; Frequency per Table 1.
XIN
8
Pullable Crystal Input; 18.432 MHz.
XOUT
9
Pullable Crystal Output; 18.432 MHz.
SAFE
10
High = reference ICLK within range, Low = reference ICLK out of range.
VSS
11
Ground
VDD
12
Voltage Supply; 3.3V.
FS3
13
Frequency Select 3; Determines CLK outputs per Table 1.
FS0
14
Frequency Select 0; Determines CLK outputs per Table 1.
CLK
15
Clock Output; Frequency per Table 1.
NC
16
No Connect
Selector Guide
Part Number
Input Frequency Range
Outputs
Output Frequencies
CY26049-36
8 kHz or 10 to 60 MHz Reference Input
Crystal: 18.432-MHz pullable Crystal per Cypress Specification
3
8 kHz to 155.52 MHz
Selectable (see Table 1)
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