APPROVED PRODUCT
C9777
Low EMI Clock Generator for 440BX, ALi1631 & Via Pro133+ / Pentium®III Systems
Suggested Crystal Oscillator Parameters
Characteristic
Frequency
Symbol
Fo
Min
Typ
Max
Units
MHz
PPM
PPM
PPM
Conditions
12.00
14.31818
16.00
Tolerance
TC
-
-
-
-
-
-
-
-
+/-100
Note 1
TS
+/- 100
Stability (Ta -10 to +60C) Note 1
Aging (first year @ 25C) Note 1
Parallel Resonant, Note 1
The crystals rated load. Note 1
Note 1
TA
-
5
-
Mode
OM
CL
-
Load Capacitance
18
40
-
pF
Effective Series
resistance (ESR)
R1
-
Ohms
Power Dissipation
Shunt Capacitance
DL
-
-
-
0.10
8
mW
pF
Note 1
Crystal’s internal package
capacitance (total)
CO
--
Note1: For best performance and accurate Center frequencies of this device, It is recommended but not mandatory that the chosen crystal meets
these specifications.
For maximum accuracy, the total circuit loading capacitance should be equal to CL. This loading capacitance is the
effective capacitance across the crystal pins and includes the device pin capacitance (CP) in parallel with any circuit
traces, the clock generator and any onboard discrete load capacitors.
Budgeting Calculations
Device pin capacitance: Cxtal = 34pF
In order to meet the specification for CL = 18pF following the formula:
CXIN xCXOUT
CL =
CXIN + CXOUT
Then the board trace capacitance between Xin and the crystal should be no more than 2pF. (same is applicable to the
trace between Xout and the crystal)
In this case the total capacitance from the crystal to Xin will be 36pF. Similarly the total capacitance between the crystal
and Xout will be 36pF. Hence using the above formula:
36pFx36pF
CL =
= 18pF
36pF + 36pF
Cypress Semiconductor Corporation
525 Los Coches St.
Document#: 38-07048 Rev. **
05/02/2001
Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571
http://www.cypress.com
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