MC100EL1648MNR4G View Datasheet(PDF) - ON Semiconductor
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MC100EL1648MNR4G Datasheet PDF : 16 Pages
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MC100EL1648
FIXED FREQUENCY MODE
The MC100EL1648 external tank circuit components are
used to determine the desired frequency of operation as
shown in Figure 8, tank option #2. The tank circuit
components have direct impact on the tuning sensitivity, IEE,
and phase noise performance. Fixed frequency of the tank
circuit is usually realized by an inductor and capacitor (LC
network) that contains a high Quality factor (Q). The plotted
curve indicates various fixed frequencies obtained with a
single inductor and variable capacitor. The Q of the
components in the tank circuit has a direct impact on the
resulting phase noise of the oscillator. In general, when the
Q is high the oscillator will result in lower phase noise.
570
470
Measured Frequency (MHz)
Calculated Frequency (MHz)
370
270
170
70
0
−30
0.3
300
500
1000 2000
CAPACITANCE (pF)
VCC
10000
0.1 mF
Test
Point
0.1 mF
8 (10)
3 (1)
L
C
1 (12)
Tank #2
VEE
6 (7) 7 (8)
0.1 mF
2 (14)
4 (3)
FOUT
5 (5)
100 mF 0.01 mF
0.1 mF 0.1 mF
L = Micro Metal torroid #T20−22, 8 turns #30
Enameled Copper wire (@ 40 nH)
C = 3.0−35 pF Variable Capacitance (@ 10 pF)
Note 1 Capacitor for tank may be variable type.
(See Tank Circuit #3.)
Note 2 Use high impedance probe (> 1 MW ).
8 pin (14 pin) lead package
QL ≥ 100
Figure 8. Fixed Frequency LC Tank
Only high quality surface−mount RF chip capacitors
should be used in the tank circuit at high frequencies. These
capacitors should have very low dielectric loss (high−Q). At
a minimum, the capacitors selected should be operating at
100 MHz below their series resonance point. As the desired
frequency of operation increases, the values of the tank
capacitor will decrease since the series resonance point is a
function of the capacitance value. Typically, the inductor is
realized as a surface−mount chip or a wound coil. In
addition, the lead inductance and board inductance and
capacitance also have an impact on the final operating point.
The following equation will help to choose the appropriate
values for your tank circuit design.
f0
+ 2p
1
Ǹ LT * CT
Where
LT = Total Inductance
CT = Total Capacitance
Figure 9 and Figure 10 represent the ideal curve of
inductance/capacitance versus frequency with one known
tank component. This helps the designer of the tank circuit
to choose desired value of inductor/capacitor component for
the wanted frequency. The lead inductance and board
inductance and capacitance will also have an impact on the
tank component values (inductor and capacitor).
50
45
40
35
30
25
Inductance vs. Frequency with 5 pF Cap
20
15
10
5
0
400
700
1000
1300
FREQUENCY (MHz)
Figure 9. Capacitor Value Known (5 pF)
50
45
1600
40
35
30
Capacitance vs. Frequency with 4 nH Inductance
25
20
15
10
5
0
400
700
1000
1300
FREQUENCY (Hz)
Figure 10. Inductor Value Known (4 nH)
1600
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