ICS10001B21 View Datasheet(PDF) - Integrated Circuit Systems
Part Name
Description
MFG CO.
'ICS10001B21' PDF : 21 Pages View PDF
Integrated
Circuit
Systems, Inc.
PRELIMINARY
ICS810001-21
FEMTOCLOCKS™ DUAL VCXO VIDEO PLL
VCXO CRYSTAL SELECTION
Choosing a crystal with the correct characteristics is one of the
most critical steps in using a Voltage Controlled Crystal Oscillator
(VCXO). The crystal parameters affect the tuning range and
accuracy of a VCXO. Below are the key variables and an
example of using the crystal parameters to calculate the tuning
range of the VCXO.
VC
“Control Voltage”
CV
Oscillator
CV
VCXO (Internal)
CS1
XTAL
CS2
CL1
CL2
Optional
FIGURE 1: VCXO OSCILLATOR CIRCUIT EXAMPLE
VC Control voltage used to tune frequency
C Varactor capacitance, varies due to the change in
V
control voltage
CL1, CL2 Load tuning capacitance used for fine tuning or
centering nominal frequency
CS1, CS2 Stray Capacitance caused by pads, vias, and other
board parasitics
CRYSTAL PARAMETER EXAMPLES
Symbol Parameter
fN
Nominal Frequency
fT
Frequency Tolerance
fS
Frequency Stability
Operating Temperature Range
CL
CO
C0/C1
ESR
Load Capacitance
Shunt Capacitance
Pullability Ratio
Equivalent Series Resistance
Drive Level
Aging @ 25°C
Mode of Operation
Minimum Typical Maximum
19.44
±20
±20
0
70
12
4
220
240
20
1
±3 per year
Fundemental
Units
MHz
ppm
ppm
°C
pF
pF
mW
ppm
VARACTOR PARAMETERS
Symbol
CV LOW
CV HIGH
Parameter
Low Varactor Capacitance
High Varactor Capacitance
Test Condition
VC = 0V
VC = 3.3V
Typical
15.4
29.6
Unit
pF
pF
810001BK-21
www.icst.com/products/hiperclocks.html
16
REV. A AUGUST 12, 2005
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