ADVANCE
INFORMATION
FailSafeTM
Communications Clock Generator
CY26049-5
Cypress Semiconductor Corporation
3901 North First Street
San Jose
CA 95134
408-943-2600
Document #: 38-07485 Rev. **
Revised October 31, 2002
Features
Benefits
Fully integrated phase-locked loop (PLL)
Integrated high-performance PLL tailored for telecom-
munications frequency synthesis eliminates the need
for external loop filter components
FailSafe
output
When reference is off, DCXO maintains clock outputs
and SAFE pin indicates FailSafe conditions
PLL driven by a crystal oscillator.
DCXO maintains continuous operation should the input
reference clock fail
Glitch-free transition simplifies system design
76.8-MHz output from 19.2-MHz input.
Works with commonly available, low-cost 19.2-MHz
crystal
Low-jitter, high-accuracy outputs
Zero-ppm error for all output frequencies
3.3 V 5% operation
Compatibility across industry standard design
platforms
16-lead TSSOP
Industry standard package with 6.4 x 5.0 mm footprint
and a height profile of just 1.1 mm
Logic Block Diagram
X IN
X O U T
IC L K
C L K A
7 6 .8 M H z
S AF E
in p u t re fe re n c e c lo c k
(1 9 .2 M H z)
e xte rn a l p u lla b le c rys ta l
(1 9 .2 M H z)
D IG IT A L
C O N T R O L L E D
C R Y S T A L
O S C IL L A T O R
F A IL S A F E
TM
C O N T R O L
P H A S E
L O C K E D
L O O P
O U T P U T
D IV ID E R
IC L K d e te c te d
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INFORMATION
CY26049-5
Document #: 38-07485 Rev. **
Page 2 of 4
Description
CY26049 is a FailSafe frequency synthesizer with a reference
clock input and 76.8-MHz output. 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 oscillator 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 of the reference clock. The unique feature
of the CY26049-5 is that the DCXO is in fact the primary
clocking source. When the reference clock is restored, the
DCXO automatically resynchronizes to the reference. The
status of the reference clock input, as detected by the
CY26049-5, is reported by the SAFE pin.
Pin Configuration
Selector Guide
Part Number
Input Frequency Range
Outputs
Output Frequencies
CY26049ZC-5 Reference Input Clock: 19.2 MHz
Crystal: 19.2-MHz pullable Crystal per Cypress Specification
1
76.8 MHz
ICLK 1
16 NC
NC
2
15 NC
NC
3
14 NC
NC
4
13 NC
VDD
5
12 VDD
VSS
6
11 VSS
CLKA
7
10 SAFE
XIN
8
9 XOUT
CY26049-5
16-pin TSSOP
Top View
Pin Description
Pin Number Pin Name
Pin Description
1
ICLK
Reference Input Clock - 19.2-MHz clock
2
NC No
Connect
3
NC
No Connect
4
NC
No Connect
5
VDD
Connect to 3.3V power supply
6
VSS
Ground
7
CLKA
Clock Output; 76.8 MHz
8
XIN
19.2-MHz Pullable Crystal Input
9
XOUT
19.2-MHz Pullable Crystal Output
10
SAFE
High = reference ICLK within range, Low = reference ICLK out of range
11
VSS
Ground
12
VDD
Connect to 3.3V power supply.
13
NC
No Connect
14
NC
No Connect
15
NC
No Connect
16
NC
No Connect
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INFORMATION
CY26049-5
Document #: 38-07485 Rev. **
Page 3 of 4
Cypress Semiconductor Corporation, 2002. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use
of any circuitry other than circuitry embodied in a Cypress Semiconductor product. Nor does it convey or imply any license under patent or other rights. Cypress Semiconductor does not authorize
its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress
Semiconductor products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress Semiconductor against all charges.
Ordering Information
Package Drawing and Dimensions
FailSafe is a trademark of Cypress Semiconductor Corporation. All product and company names mentioned in this document are
the trademarks of their respective holders.
Recommended Pullable Crystal Specifications
Parameter
Name
Min.
Typ.
Max.
Unit
CL
XTAL
Crystal Nominal Load Capacitance
14
pF
C0/C1
250
ESR
Equivalent Series Resistance
30
50
T
o
Operating Temperature
0
70
C
Crystal Accuracy
Crystal Initial Accuracy
20
50
ppm
TT
s
Stability Over Temperature and Aging
20
50
ppm
C
O
Shunt Capacitance
6
7
pF
C
LBRD
Stray Capacitance--On XIN/XOUT
2
pF
All applicable DC and AC characteristics are as described in the CY26049-36 data sheet.
Ordering Code
Package Type
Operating Temperature Range
CY26049ZC-5
16-lead TSSOP
Commercial 0 to 70C
CY26049ZC-5T
16-lead TSSOP--Tape and Reel
Commercial 0 to 70C
16-lead Thin Shrunk Small Outline Package (4.40 MM Body) Z16
51-85091-**
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INFORMATION
CY26049-5
Document #: 38-07485 Rev. **
Page 4 of 4
Document History Page
Document Title: CY26049-5 FailSafeTM Communications Clock Generator
Document Number: 38-07485
REV.
ECN NO.
Issue
Date
Orig. of
Change
Description of Change
**
119591
10/31/02
CKN
New Data Sheet
PDF 
ZIP