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APPLICATION NOTE 530
VCO Tank Design for the MAX2310
Sep 30, 2002
Abstract: This application note presents various voltage-controlled oscillator (VCO) designs for popular IF
frequencies of 85MHz, 190MHz, and 210MHz. These designs reduce the number of iterations required
for optimized results. Analysis can be accomplished with a simple spreadsheet program.
Additional Information:
Wireless Product Line Page
Quick View Data Sheet for the MAX2306/MAX2308/MAX2309
Quick View Data Sheet for the
MAX2310/MAX2312/MAX2314/MAX2316
Applications Technical Support
Introduction
Click here for an overview of the wireless
components used in a typical radio
transceiver.
This application note presents various voltage-controlled oscillator
(VCO) designs for popular IF frequencies of 85MHz, 190MHz, and
210MHz. These designs reduce the number of iterations required for optimized results. Analysis can be
accomplished with a simple spreadsheet program.
VCO Design
Figure 2 shows the differential tank circuit used for the MAX2310 IF VCO. For analysis purposes, the
tank circuit must be reduced to an equivalent simplified model. Figure 1 depicts the basic VCO model.
The frequency of oscillation can be characterized by EQN1:
EQN1
fosc = frequency of oscillation
L = inductance of the coil in the tank circuit
C int = internal capacitance of the MAX2310 tank port
C t = total equivalent capacitance of the tank circuit
Page 1 of 21
Figure 1. Basic VCO model.
R n = equivalent negative resistance of the MAX2310 tank port
C int = internal capacitance of the MAX2310 tank port
C t = total equivalent capacitance of the tank circuit
L = inductance of the coil in the tank circuit
Figure 2. The MAX2310 tank circuit.
Inductor L resonates with the total equivalent capacitance of the tank and the internal capacitance of the
oscillator (Ct +Cint) (see Figure 1). C coup provides DC block and couples the variable capacitance of the
varactor diodes to the tank circuit. C cent is used to center the tank's oscillation frequency to a nominal
value. It is not required but adds a degree of freedom by allowing one to fine-tune resonance between
inductor values. Resistors (R) provide reverse-bias voltage to the varactor diodes via the tune voltage
line (Vtune ). Their value should be chosen large enough so as not to affect loaded-tank Q but small
enough so that 4kTBR noise is negligible. The resistors' noise voltage gets modulated by KVCO,
producing phase noise. Capacitance C v is the variable tuning component in the tank. The capacitance of
varactor diode (Cv ) is a function of reverse-bias voltage (see Appendix A for the varactor model). Vtune
is the tuning voltage from a phase-locked loop (PLL).
Figure 3 shows the lumped C stray VCO model. Parasitic capacitance and inductance plague every RF
circuit. In order to predict the frequency of oscillation, the parasitic elements must be taken into account.
The circuit in Figure 3 lumps the parasitic elements in one capacitor called C stray. The frequency of
oscillation can be characterized by EQN2:
Page 2 of 21
EQN2
L = inductance of the coil in the tank circuit
C int = internal capacitance of the MAX2310 tank port
C cent = tank capacitor used to center oscillation frequency
C stray = lumped stray capacitance
C coup = tank capacitor used to couple the varactor to the tank
C v = net variable capacitance of the varactor diode (including series inductance)
C vp = varactor-pad capacitance
Figure 3. Lumped C stray model.
Figure 4 depicts the detailed VCO model. It takes into account the capacitance of the pads but does not
include the effects of series inductance for simplicity. C stray is defined as:
EQN3
C L = capacitance of the inductor
C LP = capacitance of the inductor pads
C DIFF = capacitance due to parallel traces
Page 3 of 21
Figure 4. Detailed VCO model.
R n = equivalent negative resistance of the MAX2310 tank port
C int = internal capacitance of the MAX2310 tank port
L T = inductance of series trace to the inductor tank circuit
C DIFF = capacitance due to parallel traces
L = inductance of the coil in the tank circuit
C L = capacitance of the inductor
C LP = capacitance of inductor pads
C cent = tank capacitor used to center oscillation frequency
C coup = tank capacitor used to couple the varactor to the tank
C var = variable capacitance of the varactor diode
C vp = varactor-pad capacitance
L S = series inductance of the varactor
R = resistance of the varactor reverse-bias resistors
To simplify analysis, inductance L T is ignored in this design. The effects of L T are more pronounced at
higher frequencies. To mathematically model the shift in frequency due to L T with the spreadsheets that
follow, the value of C DIFF can be increased appropriately. Minimize inductance L T to prevent undesired
series resonance. This can be accomplished by making the traces short.
Tuning Gain
Tuning gain (Kvco ) must be minimized for best closed-loop phase noise. Resistors in the loop filter as
well as the resistors "R" (Figure 2) will produce broadband noise. Broadband thermal noise (
) will modulate the VCO by Kvco , which is measured in MHz/V. There are two ways to
minimize Kvco . One is to minimize the frequency range over which the VCO must tune. The second way
is to maximize the tuning voltage available. To minimize the frequency range over which the VCO must
tune, tight tolerance components must be used, as will be shown. To maximize tuning voltage, a charge
pump with a large compliance range is needed. This is usually accomplished by using a larger Vcc. The
compliance range for the MAX2310 is 0.5V to Vcc-0.5V. In battery-powered applications, the compliance
range is usually fixed by battery voltage or a regulator.
Basic Concept for Trimless Design
VCO design for manufacturability with real-world components will require an error budget analysis. In
order to design a VCO to oscillate at a fixed frequency (fosc ), the tolerance of the components must be
taken into consideration. Tuning gain (Kvco ) must be designed into the VCO to account for these
component tolerances. The tighter the component tolerance, the smaller the possible tuning gain, and
the lower the closed-loop phase noise. For worst-case error budget design, we will look at three VCO
models:
1. Maximum-value components (EQN5)
Page 4 of 21
2. Nominal tank, all components perfect (EQN2)
3. Minimum-value components (EQN4)
All three VCO models must cover the desired nominal frequency. Figure 5 shows visually how the three
designs must converge to provide a manufacturable design solution. Observation of EQN1 and Figure 5
reveal that minimum-value components will shift the oscillation frequency higher and that maximumvalue components will shift the oscillation frequency lower.
Figure 5. Worst-case and nominal-tank centering.
Minimum tuning range must be used in order to design a tank with the best closed-loop phase noise.
Therefore, the nominal tank should be designed to cover the center frequency with overlap to take into
account device tolerance. The worst-case high-tune tank and worst-case low-tune tank should tune just
to the edge of the desired oscillation frequency. EQN2 can be modified by component tolerance to
produce a worst-case high-tune tank EQN4 and a worst-case low-tune tank EQN5.
EQN4
Page 5 of 21
EQN5
TL = % tolerance of the inductor (L)
TCINT = % tolerance of the capacitor (CINT)
TCCENT = % tolerance of the capacitor (CCENT)
TCCOUP = % tolerance of the capacitor (CCOUP)
TCV = % tolerance of the varactor capacitance (CV )
EQN4 and EQN5 assume that the strays do not have a tolerance.
General Design Procedure
Step 1
Estimate or measure pad capacitance and other strays. The stray capacitance on the MAX2310 Rev C
EV kit has been measured with a Boonton Model 72BD capacitance meter. C LP = 1.13pF, C VP =
0.82pF, C DIFF = 0.036pF.
Step 2
Determine the value for capacitance C int. This can be found in the
MAX2310/MAX2312/MAX2314/MAX2316 data sheet on Page 5. Typical operating characteristic TANKH
PORT 1/S11 vs. FREQUENCY shows the equivalent parallel RC values for several popular LO
frequencies. Appendix B includes tables of C int versus frequency for the high- and low-band tank ports.
Keep in mind that the LO frequency is twice the IF frequency.
Example:
For an IF frequency of 210MHz (high-band tank), the LO will operate at 420MHz. From Appendix B,
Table 5, C int = 0.959pF.
Step 3
Choose an inductor. A good starting point is using the geometric mean. This will be an iterative process.
EQN6
This equation assumes L in (nH) and C in (pF) (1x10 -9 x 1x10 -12 = 1x10 -21 ). L = 11.98nH for a fosc =
420MHz. This implies a total tank capacitance C = 11.98pF. An appropriate initial choice for an inductor
would be 12nH Coilcraft 0805CS-12NXGBC 2% tolerance.
When choosing an inductor with finite step sizes, the following formula EQN6.1 will be useful. The total
product LC should be constant for a fixed oscillation frequency fosc .
Page 6 of 21
EQN6.1
LC = 143.5 for a fosc = 420MHz. The trial-and-error process with the spreadsheet in Table 3 yielded an
inductor value of 18nH 2% with a total tank capacitance of 7.9221pF. The LC product for the tank in
Figure 8 is 142.59, close enough to the desired LC product of 143.5. One can see this is a useful
relationship to have on hand. For best phase noise, choose a high-Q inductor like the Coilcraft 0805CS
series. Alternatively, a micro-strip inductor can be used if the tolerance and Q can be controlled
reasonably.
Step 4
Determine the PLL compliance range. This is the range over which the VCO tuning voltage (Vtune ) will
be designed to work. For the MAX2310, the compliance range is 0.5V to Vcc-0.5V. For a Vcc = 2.7V,
this would set the compliance range to 0.5 to 2.2V. The charge-pump output will set this limit. The
voltage swing on the tank is 1Vp-p centered at 1.6VDC. Even with large values for C coup, the varactor
diodes will not be forward-biased. This is a condition to be avoided, as the diode will rectify the AC
signal on the tank pins, producing undesirable spurious response and loss of lock in a closed-loop PLL.
Step 5
Choose a varactor. Look for a varactor with good tolerance over your specified compliance range. Keep
the series resistance small. For a figure of merit, check that the self-resonant frequency of the varactor is
above the desired operating point. Look at the C v (2.5V)/C v (0.5V) ratio at your compliance-range voltage.
If the coupling capacitors C coup were chosen large, then the maximum tuning range can be calculated
using EQN2. Smaller values of capacitor C coup will reduce this effective frequency tuning range. When
choosing a varactor, it should have a tolerance specified at your given compliance-range mid and end
points. Select a hyperabrupt varactor such as the Alpha SMV1763-079 for linear tuning response. Take
the value for total tank capacitance, and use that for Cjo of the varactor. Remember, C coup will reduce
the net capacitance coupled to the tank.
Step 6
Pick a value for C coup. Large values of C coup will increase tuning range by coupling more of the varactor
into the tank at the expense of decreasing tank-loaded Q. Smaller values of C coup will increase the
effective Q of the coupled varactor and loaded Q of the tank at the expense of reducing tuning range.
Typically this will be chosen as small as possible, while still getting the desired tuning range. Another
benefit of choosing C coup small is that it reduces the voltage swing across the varactor diode. This will
help thwart forward-biasing the varactor.
Step 7
Pick a value for C cent, usually around 2pF or greater for tolerance purposes. Use C cent to center the
VCO's nominal frequency.
Step 8
Iterate with the spreadsheet.
MAX2310 VCO Tank Designs for IF Frequencies of 85MHz,
190MHz, and 210MHz
The following spreadsheets show designs for several popular IF frequencies for the MAX2310. Keep in
Page 7 of 21
mind that the LO oscillates at twice the desired IF frequency.
Figure 6. 85MHz low-band IF tank schematic.
Table 1. 85MHz Low-Band IF Tank Design
Light grey indicates calculated
values.
Darker grey indicates user input.
MAX2310 Low-Band Tank Design and Tuning Range
Total Tank Capacitance vs. V tune
V tune
Total C
Ct
(Nominal)
Ct
(Low)
Ct
(High)
0.5V
Ct high
14.1766pF
13.3590pF 14.9459pF
1.375V
Ct mid
12.8267pF
11.7445pF 13.7620pF
2.2V
Ct low
11.4646pF
10.3049pF 12.4534pF
Tank Components
Tolerance
C coup
18pF
0.9pF
5%
C cent
5.6pF
0.1pF
2%
C stray
0.70pF
L
C int
68nH
2.00%
0.902pF
10.00%
Parasitics and Pads (C stray)
Due to Q
C L
0.1pF
Page 8 of 21
Ind. pad
C Lp
1.13pF
Due to ||
C diff
0.036pF
Var. pad
C vp
0.82pF
Varactor Specs
Alpha SMV1255-003
Cjo
82pF
Vj
17V
0.5V
19.00%
M
14
1.5V
29.00%
Cp
0pF
2.5V
35.00%
Rs
1Ω
Ls
1.7nH
Varactor Tolerance
Reactance
X Ls
1.82
170.00MHz
Freq
Nominal Varactor
Xc
Net Cap
Cv high
54.64697pF
-17.1319
61.12581pF
Cv mid
27.60043pF
-33.92
29.16154pF
Cv low
14.92387pF
-62.7321
15.36874pF
Negative Tol Varactor (Low Capacitance)
Cv high
44.26404pF
-21.1505
48.42117pF
Cv mid
19.59631pF
-47.7746
20.37056pF
Cv low
9.700518pF
-96.5109
9.886531pF
Positive Tol Varactor (High Capacitance)
Cv high
65.02989pF
-14.3965
74.41601pF
Cv mid
35.60456pF
-26.2945
38.24572pF
Cv low
20.14723pF
-46.4682
20.96654pF
Nominal LO
(Nom) Range
Low Tol IF
(High) Range
Nominal IF
(Nom) Range
High Tol IF
(Low) Range
F low
162.10MHz
84.34MHz
81.05MHz
78.16MHz
F mid
170.42MHz
89.95MHz
85.21MHz
81.45MHz
F high
180.25MHz
96.03MHz
90.13MHz
85.62MHz
BW
18.16MHz
11.69MHz
9.08MHz
7.46MHz
10.65%
12.99%
10.65%
9.16%
% BW
Nominal IF Frequency
85.00MHz
Design Constraints
Page 9 of 21
Condition for bold number
IF
Delta
0.66
-0.21
0.62
Test
pass
pass
pass
-0.21
MHz
Inc or dec BW
-1.28
MHz
Cent adj for min BW
84.98
MHz
Raise or lower cent freq by
K vco
10.68MHz/V
Figure 7. 190MHz high-band IF tank schematic.
Table 2. 190MHz High-Band IF Tank Design
Light grey indicates calculated
values.
Darker grey indicates user input.
MAX2310 High-Band Tank Design and Tuning Range
Total Tank Capacitance vs. V tune
V tune
Total C
Ct
(Nominal)
Ct
(Low)
Ct
(High)
0.5V
Ct high
10.4968pF
10.0249pF 10.9126pF
1.375V
Ct mid
9.6292pF
8.8913pF 10.2124pF
2.2V
Ct low
8.6762pF
7.7872pF
9.3717pF
Tank Components
Tolerance
C coup
12pF
0.1pF
1%
Page 10 of 21
C cent
3.4pF
C stray
0.70pF
L
C int
0.1pF
3%
18nH
2.00%
0.954pF
10.00%
Parasitics and Pads (C stray)
Due to Q
C L
0.01pF
Ind. pad
C Lp
1.13pF
Due to ||
C diff
0.036pF
Var. pad
C vp
0.82pF
Varactor Specs
Alpha SMV1255-003
Cjo
82pF
Vj
17V
0.5V
19.00%
M
14
1.5V
29.00%
Cp
0pF
2.5V
35.00%
Rs
1Ω
Ls
1.7nH
Varactor Tolerance
Reactance
X Ls
4.06
380.00MHz
Freq
Nominal Varactor
X c
Net Cap
Cv high
54.64697pF
-7.66426
116.1695pF
Cv mid
27.60043pF
-15.1747
37.67876pF
Cv low
14.92387pF
-28.0643
17.44727pF
Negative Tol Varactor (Low Capacitance)
Cv high
44.26404pF
-9.46205
77.51615pF
Cv mid
19.59631pF
-21.3728
24.19031pF
Cv low
9.700518pF
-43.1759
10.70708pF
Positive Tol Varactor (High Capacitance)
Cv high
65.02989pF
-6.44056
175.8588pF
Cv mid
35.60456pF
-11.7633
54.36221pF
Cv low
20.14723pF
-20.7884
25.03539pF
Nominal LO
(Nom) Range
Low Tol IF
(High) Range
Nominal IF
(Nom) Range
High Tol IF
(Low) Range
F low
366.15MHz
189.23MHz
183.07MHz
177.78MHz
F mid
382.29MHz
200.94MHz
191.14MHz
183.78MHz
Page 11 of 21
F high
BW
402.74MHz
214.71MHz
201.37MHz
191.84MHz
36.59MHz
25.47MHz
18.29MHz
14.06MHz
9.57%
12.68%
9.57%
7.65%
% BW
Nominal IF Frequency
190MHz
Design Constraints
Condition for bold number
< IF
= IF
> IF
Delta
0.77
-1.14
1.84
Test
pass
pass
pass
Raise or lower cent freq by
-1.14
MHz
Inc or dec BW
-2.61
MHz
190.54
MHz
Cent adj for min BW
21.52MHz/V
K vco
Figure 8. 210MHz high-band IF tank schematic.
Table 3. 210MHz High-Band IF Tank Design
Light grey indicates calculated
values.
Darker grey indicates user input.
MAX2310 High-Band Tank Design and Tuning Range
Total Tank Capacitance vs. V tune
V tune
Total C
Ct
Ct
Ct (High)
Page 12 of 21
(Nominal)
(Low)
0.5V
Ct high
8.8304pF
8.1465pF 9.4877pF
1.35V
Ct mid
7.9221pF
7.0421pF 8.6970pF
2.2V
Ct low
6.9334pF
5.9607pF 7.7653pF
Tank Components
Tolerance
C coup
12pF
0.6pF
5%
C cent
1.6pF
0.1pF
6%
C stray
0.70pF
L
C int
18nH
2.00%
0.959pF
10.00%
Parasitics and Pads (C stray)
Due to Q
C L
0.1pF
Ind. pad
C Lp
1.13pF
Due to ||
C diff
0.036pF
Var. pad
C vp
0.82pF
Varactor Specs
Alpha SMV1255-003
Cjo
82pF
Vj
17V
0.5V
19.00%
M
14
1.5V
29.00%
Cp
0pF
2.5V
35.00%
Rs
1Ω
Ls
1.7nH
Varactor Tolerance
Reactance
X Ls
4.49
420.00MHz
Freq
Nominal Varactor
Xc
Net Cap
Cv high
54.64697pF
-6.93433
154.787pF
Cv mid
27.60043pF
-13.7295
40.99616pF
Cv low
14.92387pF
-25.3916
18.12647pF
Negative Tol Varactor (Low Capacitance)
Cv high
44.26404pF
-8.56091
92.99806pF
Cv mid
19.59631pF
-19.3373
25.51591pF
Cv low
9.700518pF
-39.0639
10.95908pF
Positive Tol Varactor (High Capacitance)
Cv high
65.02989pF
-5.82717
282.5852pF
Page 13 of 21
Cv mid
35.60456pF
-10.643
61.54791pF
Cv low
20.14723pF
-18.8086
26.45795pF
Nominal LO
(Nom) Range
Low Tol IF
(High) Range
Nominal IF
(Nom) Range
High Tol IF
(Low) Range
F low
399.20MHz
209.92MHz
199.60MHz
190.67MHz
F mid
421.47MHz
225.78MHz
210.73MHz
199.14MHz
F high
450.52MHz
245.41MHz
225.26MHz
210.75MHz
BW
51.31MHz
35.49MHz
25.66MHz
20.09MHz
12.18%
15.72%
12.18%
10.09%
% BW
Nominal IF Frequency
210MHz
Design Constraints
condition for bold number
< IF
= IF
> IF
Delta
0.08
-0.73
0.75
Test
pass
pass
pass
Raise or lower cent freq by
-0.73
MHz
Inc or dec BW
-0.83
MHz
210.34
MHz
Cent adj for min BW
K vco
30.18MHz/V
Figure 9. High-Q 210MHz high-band IF tank schematic.
Table 4. High-Q 210MHz High-Band IF Tank Design
Page 14 of 21
Light grey indicates calculated
values.
Darker grey indicates user input.
MAX2310 High-Band Tank Design and Tuning Range
Total Tank Capacitance vs. V tune
V tune
Total C
Ct
(Nominal)
Ct
Ct
(Low) (High)
0.5V
Ct high
5.8856
5.5289 6.2425
1.375V
Ct mid
5.2487
4.9113 5.5858
2.2V
Ct low
4.8371
4.5156 5.1581
C coup
15pF
0.75pF
5%
C cent
1.6pF
0.1pF
6%
C stray
0.77pF
Tank Components
L
C int
27
2.00%
0.959
10.00%
Parasitics and Pads (C stray)
Due to Q
C L
0.17pF
Ind. pad
C Lp
1.13pF
Due to ||
C diff
0.036pF
Var. pad
C vp
0.82pF
Varactor Specs
Alpha SMV1763-079
Cjo
8.2pF
Varactor Tolerance
Vj
15V
0.5V
7.50%
M
9.5
1.5V
9.50%
Cp
0.67pF
2.5V
11.50%
Rs
0.5Ω
Ls
0.8nH
Reactance
X Ls
2.11
420.00MHz
Freq
Nominal Varactor
Xc
Net Cap
Cv high
6.67523pF
-56.7681
6.933064pF
Cv mid
4.23417pF
-89.4958
4.336464pF
Cv low
2.904398pF
-130.471
2.952167pF
Page 15 of 21
Negative Tol Varactor (Low Capacitance)
Cv high
6.174588pF
-61.3709
6.39456pF
Cv mid
3.831924pF
-98.8904
3.915514pF
Cv low
2.570392pF
-147.425
2.607736pF
Positive Tol Varactor (High Capacitance)
Cv high
7.175873pF
-52.8076
7.474698pF
Cv mid
4.636416pF
-81.7313
4.759352pF
Cv low
3.238404pF
-117.015
3.297904pF
Nominal LO
(Nom) Range
Low Tol IF
(High) Range
Nominal IF
(Nom) Range
High Tol IF
(Low) Range
F low
399.25MHz
208.05MHz
199.62MHz
191.92MHz
F mid
422.78MHz
220.75MHz
211.39MHz
202.89MHz
F high
440.40MHz
230.22MHz
220.20MHz
211.14MHz
BW
41.15MHz
22.16MHz
20.58MHz
19.21MHz
9.73%
10.04%
9.73%
9.47%
% BW
Nominal IF Frequency
210MHz
Design Constraints
Condition for bold number
< IF
= IF
> IF
Delta
1.95
-1.39
1.14
Test
pass
pass
pass
Raise or lower cent freq by
-1.39
MHz
Inc or dec BW
-3.08
MHz
209.60
MHz
Cent adj for min BW
K vco
24.21MHz/V
Appendix A
Page 16 of 21
Figure 10. Varactor model.
Alpha Application Note AN1004 has additional information on varactor models. Varactor capacitance is
defined in EQN7:
EQN7
Alpha SMV1255-003
C jo = 82 pF
Vj =17 V
M = 14
Cp = 0
R s = 1Ω
L s = 1.7 nH
Alpha SMV1763-079
C jo = 8.2 pF
Vj =15 V
M = 9.5
C p = 0.67
R s = 0.5Ω
L s = 0.8 nH
The series inductance of the varactor is taken into account by backing out the inductive reactance and
calculating a new effective capacitance C v :
EQN8
Appendix B
Table 5. C int vs. Frequency for the MAX2310 High-Band Tank
Frequency (MHz) C int (pF) Frequency (MHz) (cont.) C int (pF) (cont.)
100
0.708
360
0.949
110
0.759
370
0.955
Page 17 of 21
120
0.800
380
0.954
130
0.809
390
0.954
140
0.839
400
0.954
150
0.822
410
0.955
160
0.860
420
0.959
170
0.869
430
0.956
180
0.880
440
0.959
190
0.905
450
0.964
200
0.917
460
0.962
210
0.920
470
0.963
220
0.926
480
0.963
230
0.924
490
0.960
240
0.928
500
0.964
250
0.935
510
0.965
260
0.932
520
0.968
270
0.931
530
0.966
280
0.933
540
0.968
290
0.927
550
0.967
300
0.930
560
0.974
310
0.933
570
0.977
320
0.943
580
0.976
330
0.944
590
0.984
340
0.945
600
0.982
350
0.956
-
-
Page 18 of 21
Figure 11. C int vs. frequency for the MAX2310 high-band tank (sixth-order polynomial curve fit)
Table 6. C int vs. Frequency for the MAX2310 Low-Band Tank
Frequency (MHz) C int (pF) Frequency (MHz) (cont.) C int (pF) (cont.)
100
0.550
360
1.001
110
0.649
370
0.982
120
0.701
380
0.992
130
0.764
390
1.001
140
0.762
400
0.985
150
0.851
410
0.980
160
0.838
420
0.986
170
0.902
430
0.992
180
0.876
440
0.994
190
0.907
450
1.001
200
0.913
460
1.003
210
0.919
470
1.007
220
0.945
480
0.992
230
0.952
490
1.010
240
0.965
500
1.004
250
0.951
510
1.011
260
0.954
520
1.022
270
0.974
530
1.019
280
0.980
540
1.044
290
0.973
550
1.026
300
0.982
560
1.041
Page 19 of 21
310
0.970
570
1.038
320
0.982
580
1.032
330
0.991
590
1.036
340
0.993
600
1.025
350
0.991
-
-
Figure 12. C int vs. frequency for the MAX2310 low-band tank (sixth-order polynomial curve fit).
References
1.
2.
3.
4.
5.
6.
7.
8.
Chris O'Connor, Develop Trimless Voltage-Controlled Oscillators, Microwaves and RF, July1999.
Wes Hayward, Radio Frequency Design, Chapter 7.
Krauss, Bostian, Raab, Solid State Radio Engineering, Chapters 2, 3, 5.
Alpha Industries Application Note AN1004.
Coilcraft, RF Inductors Catalog, March 1998, p.131.
Maxim, MAX2310/MAX2312/MAX2314/MAX2316 Data Sheet, Rev 0.
Maxim, MAX2310/MAX2314 Evaluation Kit Data Sheet, Rev 0.
Maxim, MAX2312/MAX2316 Evaluation Kit Data Sheet, Rev 0.
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More Information
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