+/+…when timing is critical
C9815C
Low EMI Clock Generator for Intel 133MHz/2DIMM Chipset Systems
Preliminary
Suggested Oscillator Crystal 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 crystal’s rated load. Note 1
Note 2
TA
-
5
-
Operating Mode
-
-
Load Capacitance
CXTAL
RESR
20
40
-
pF
Effective Series
-
Ohms
Resistance (ESR)
Note1: For best performance and accurate frequencies from this device, It is recommended but not mandatory that the
chosen crystal meets or exceeds these specifications
Note 2: Larger values may cause this device to exibit oscillator startup problems
To obtain the maximum accuracy, the total circuit loading capacitance should be equal to CXTAL. This loading
capacitance is the effective capacitance across the crystal pins and includes the clock generating device pin
capacitance (CFTG), any circuit traces (CPCB), and any onboard discrete load capacitors (CDISC).
The following formula and schematic may be used to understand and calculate either the loading specification of a crystal for a
design or the additional discrete load capacitance that must be used to provide the correct load to a known load rated crystal.
CL = (CXINPCB + CXINFTG + CXINDISC) X (CXOUTPCB + CXOUTFTG + CXOUTDISC
(CXINPCB + CXINFTG + CXINDISC) + (CXOUTPCB + CXOUTFTG + COUTDISC
Where:
CXTAL
)
)
= the load rating of the crystal
CXOUTFTG = the clock generators XIN pin effective device internal capacitance to ground
CXOUTFTG = the clock generators XOUT pin effective device internal capacitance to ground
CXINPCB = the effective capacitance to ground of the crystal to device PCB trace
CXOUTPCB = the effective capacitance to ground of the crystal to device PCB trace
CXINDISC = any discrete capacitance that is placed between the XIN pin and ground
CXOUTDISC = any discrete capacitance that is placed between the XOUT pin and ground
XIN
CXINPCB
CXINDISC
CXINFTG
CXOUTPCB
CXOUTDISC
CXOUTFTG
XOUT
Clock Generator
INTERNATIONAL MICROCIRCUITS, INC. 525 LOS COCHES ST.,
MILPITAS, CA 95035, USA TEL: 408-263-6300, FAX 408-263-6571
http://www.imicorp.com
Rev 1.2
4/5/2000
Page 16 of 18
CYPRESS [ CYPRESS ]
