LANSDALE ML12149 Low power voltage controlled oscillator buffer Datasheet

ML12149
Low Power Voltage
Controlled Oscillator Buffer
Legacy Device: Motorola MC12149
The ML12149 is intended for applications requiring high frequency signal generation up to 1300 MHz. An external tank circuit
is used to determine the desired frequency of operation. The VCO
is realized using an emmiter–coupled pair topology. The ML12149
can be used with an emitter PLL IC such as the Motorola
ML12210 1.1 GHz Frequency Synthesizer to realize a complete
PLL sub–system. The device is specified to operate over a voltage
supply range of 2.7 to 5.5 V. It has a typical current consumption
of 15 mA at 3.0 V which makes it attractive for battery operated
handheld systems.
NOTE: The ML12149 is NOT suitable as a crystal oscillator
•
•
•
•
•
•
•
•
•
Operated Up to 1.3 GHz
Space–Efficient 8–Pin SOIC Package
Low Power 15 mA Typical @ 3.0 V Operation
Supply Voltage of 2.7 to 5.5 V
Typical 900 MHz Performance
–Phase Noise – 105 dBc/Hz @ 100 Khz Offset
–Tuning Voltage Sensitivity of 20 MHz/V
Output Amplitude Adjustment Capability
Two High Drive Output with an Adjustable Range from
–8.0 to –2.0 dBm
One Low–Drive Output for Interfacing to a Prescaler
Operating Temperature Range TA = –40 to 85°C
The device has three high frequency outputs which make it
attractive for transceiver applications which require both a transmit
and receive local oscillator (LO) signal as well as a lower amplitude signal to drive the prescaler input of the frequency synthesizer. The outputs Q and QB are available for servicing the receiver
IF and transmitter up–converter single–ended. In receiver applications, the outputs can be used together if it is necessary to generate
a differential signal for the receiver IF. Because the Q and QB outputs are open collector, terminations to the VCC supply are
required for proper operation. Since the outputs are complementary, both outputs must be terminated even if only one is needed.
The Q and QB outputs have a nominal drive level of –8dBm to
conserve power. A level adjustment pin (CNTL) is available, which
when tied to ground, boosts the nominal output levels to –2.0
dBm. A low power VCO output (Q2) is also provided to drive the
prescaler input of the PLL. The amplitude of this signal is nominally 500 mV which is suitable for most prescalers.
External components required for the ML12149 are: (1) tank circuit (LC network); (2) Inductor/capacitor to provide the termination for the open collector outputs; and (3) adequate supply voltage
bypassing. The tank circuit consists of a high–Q inductor and varactor components. The preferred tank configuration allows the user
to tune the VCO across the full supply range. VCO performance
such as center frequency, tuning voltage sensitivity, and noise characteristics are dependent on the particular components and configuration of the VCO tank circuit.
Page 1 of 12
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SO 8 = -5P
PLASTIC PACKAGE
CASE 751
(SO–8)
8
1
CROSS REFERENCE/ORDERING INFORMATION
PACKAGE
MOTOROLA
LANSDALE
SO 8
MC12149D
ML12149-5P
Note: Lansdale lead free (Pb) product, as it
becomes available, will be identified by a part
number prefix change from ML to MLE.
PIN CONNECTIONS
Q2
Q
GND
QB
8
7
6
5
2
3
1
VCC
CNTL TANK
4
VREF
(Top View)
Issue B
LANSDALE Semiconductor, Inc.
ML12149
PIN NAMES
Pin
VCC
CNTL
TANK
VREF
QB
GND
Q
Q2
Function
Power Supply
Amplitude Control for Q, QB Output Pair
Tank Circuit Input
Bias Voltage Output
Open Collector Output
Ground
Open Collector Output
Low Power Output
MAXIMUM RATINGS (Note 1)
Symbol
Value
Unit
VCC
–0.5 to 7.0
V
TA
–40 to 85
C
TSTG
–65 to 150
C
Maximum Output Current, Pin 8
IO
7.5
mA
Maximum Output Current, Pin 5,7
IO
12
mA
Parameter
Power Supply Voltage, Pin 1
Operating Temperature Range
Storage Temperature Range
NOTES: 1. Maximum Ratings are those values beyond which damage to the device may occur.
Functional operation should be restricted to the Recommended Operating Conditions.
ELECTRICAL CHARACTERISTICS (VCC = 2.7 to 5.5 VDC, TA = –40 to 85 C, unless otherwise noted.)
Symbol
Min
Typ
Max
Unit
Supply Current (CNTL=GND)VCC = 3.3 V
VCC = 5.5 V
ICC
–
–
16
23.5
20
30
mA
Supply Current (CNTL=OPEN)VCC = 3.3 V
VCC = 5.5 V
ICC
–
–
10
15
15.0
24.5
mA
Output Amplitude (Pin 8)VCC = 2.7 V
High Impedance LoadVCC = 2.7 V
VOH,
VOL
1.75
1.20
1.85
1.35
1.95
1.50
V
Output Amplitude (Pin 8)VCC = 5.5 V
High Impedance LoadVCC = 5.5 V
VOH,
VOL
4.50
3.85
4.6
4.0
4.70
4.15
V
Output Amplitude (Pin 5 & 7) [Note 1] VCC = 2.7 V
50 Ω to VCC
VCC = 2.7 V
VOH,
VOL
2.6
2.1
2.7
2.3
–
2.4
V
Output Amplitude (Pin 5 & 7) [Note 1] VCC = 5.5 V
50Ω to VCC
VCC = 5.5V
VOH,
VOL
5.4
4.8
5.5
5.0
–
5.1
V
Tstg
FC
–
20
–
MHz/V
100
–
1300
MHz
Characteristic
Tuning Voltage Sensitivity [Notes 2 and 3]
Frequency of Operation
CSR at 10 kHz Offset, 1Hz BW [Notes 2 and 3]
(f)
–
–85
–
dBc/Hz
CSR at 100 kHz Offset, 1Hz BW [Notes 2 and 3]
(f)
–
–105
–
dBc/Hz
Fsts
fstt
–
–
0.8
50
–
–
MHz/V
KHz/ C
Frequency Stability [Notes 3 and 4]
Supply Drift
Thermal Drift
NOTES: 1. CNTL pin tied to ground.
2. Actual performance depends on tank components selected.
3. See Figure 12, 750 MHz tank.
4. T = 25 C, VCC = 5.0 V ±10%
Page 2 of 12
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LANSDALE Semiconductor, Inc.
ML12149
OPERATIONAL CHARACTERISTICS
A simplified schematic of the ML12149 is found in Figure 1.
The oscillator incorporates positive feedback by coupling the base
of transistor Q2 to the collector of transistor Q1. In order to minimize interaction between the VCO outputs and the oscillator tank
transistor pair, a buffer is incorporated into the circuit. This differential buffer is realized by the Q3 and Q4 transistor pair. The differential buffer drives the gate which contains the primary open
collector outputs, Q and QB. The output is actually a current
which has been set by an internal bias driver to a nominal current
of 4mA. Additional circuitry is incorporated into the tail of the
current source which allows the current source to be increased to
approximately 10 mA. This is accommodated by the addition of a
resistor which is brought out to the CNTL pin. When this pin is
tied to ground, the additional current is sourced through the current source thus increasing the output amplitude of the Q/QB output pair. If less than 10mA of current is needed, a resistor can be
added to ground which reduces the amount of current.
The Q/QB outputs drive an additional differential buffer which
generate the Q2 output signal. To minimize current, the circuit is
realized as an emitter–follower buffer with an on chip pull down
resistor. This output is intended to drive the prescaler input of the
PLL synthesizer block.
APPLICATION INFORMATION
Figure 2 illustrates the external components necessary for the
proper operation of the VCO buffer. The tank circuit configuration in this figure allows the VCO to be tuned across the full
operating voltage of the power supply. This is very important in
3.0 V applications where it is desirable to utilize as much of the
operating supply range as possible so as to minimize the VCO
sensitivity (MHz/V). In most situations, it is desirable to keep the
sensitivity low so the circuit will be less susceptible to external
noise influences. An additional benefit to this configuration is
that additional regulation/ filtering can be incorporated into the
Vcc line without compromising the tuning range of the VCO.
With the AC–coupled tank configuration, the Vtune voltage can
be greater than the VCC voltage supplied to the device. There are
four main areas that the user directly influences the performance
of the VCO. These include Tank Design, Output Termination
Selection, Power Supply Decoupling, and Circuit Board
Layout/Grounding. The design of the tank circuit is critical to the
proper operation of the VCO. This tank circuit directly impacts
the main VCO operating characteristics:
1) Frequency of Operation
2) Tuning Sensitivity
3) Voltage Supply Pushing
4) Phase Noise Performance
The tank circuit, in its simplest form, is realized as an LC circuit which determines the VCO operating frequency. This is
described in Equation 1.
fo =
1
Equation 1
2 √ LC
In the practical case, the capacitor is replaced with a varactor
diode whose capacitance changes with the voltage applied, thus
changing the resonant frequency at which the VCO tank operates.
The capacitive component in Equation 1 also needs to include the
input capacitance of the device and other circuit and parasitic elements. 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.
Figure 1. Simplified Schematic
VCC
Q3
Q4
TANK
VREF
Q1
Q
QB
Q5
Q6
VCC
Q2
Q2
VREF
136Ω
CNTL
1000Ω
200Ω
GND
Page 3 of 12
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Issue B
LANSDALE Semiconductor, Inc.
ML12149
Figure 2. ML12149 Typical External Component Connections
VCC Supply
C3a
C3a
VCC
1
Q2
8
C7
CNTL
Q
L2a
2
7
C2a
Note 1
R1
C2a
TANK
C1
LT
CV
Cb
VREF
4
C6a
VCO Output
GND
3
Vin
To Prescaler
6
VCO
QB
L2b
C6b
5
VCO Output
1. This input can be left open, tied to ground, or tied with a resistor to ground, depending
on the desired output amplitude needed at the Q and QB output pair.
2. Typical values for R1 range from 5.0 kΩ to 10 kΩ.
Legacy Applications Information
A simplified linear approximation of the device, package, and
typical board parasitics has been developed to aid the designer in
selecting the proper tank circuit values. All the parasitic contributions have been lumped into a parasitic capacitive component and a
parasitic inductive component. While this is not entirely accurate, it
gives the designer a solid starting point for selecting the tank components. Below are the parameters used in the model.
Cp Parasitic Capacitance
Lp Parasitic Inductance
LT Inductance of Coil
C1 Coupling Capacitor Value
Cb Capacitor for decoupling the Bias Pin
CV Varactor Diode Capacitance (Variable)
The values for these components are substituted into the following equations:
x
Ci = C1 CV
C1 + CV
x
C = Ci Cb
Ci + Cb
L=
Lp + LT
Cp
Equation 2
Equation 3
Equation 4
From Figure 2, it can be seen that the varactor capacitance (CV) is
in series with the coupling capacitor (C1). This is calculated in
Equation 2. For analysis purposes, the parasitic capacitances (CP) are
treated as a lumped element and placed in parallel with the series
combination of C1 and CV. This compound capacitance (Ci) is in
series with the bias capacitor (Cb) which is calculated in Equation 3.
The influences of the various capacitances; C1, CP, and Cb, impact
the design by reducing the variable capacitance effects of the varactor which controls the tank resonant frequency and tuning range.
Page 4 of 12
Now the results calculated from Equation 2, Equation 3 and
Equation 4 can be substituted into Equation 1 to calculate the actual frequency of the tank.
To aid in analysis, it is recommended that the designer use a simple spreadsheet based on Equation 1 through Equation 4 to calculate the frequency of operation for various varactor/inductor selections before determining the initial starting condition for the tank.
The two main components at the heart of the tank are the inductor (LT) and the varactor diode (CV). The capacitance of a varactor
diode junction changes with the amount of reverse bias voltage
applied across the two terminals. This is the element which actually
“tunes” the VCO. One characteristic of the varactor is the tuning
ratio which is the ratio of the capacitance at specified minimum
and maximum voltage points. For characterizing the ML12149, a
Matsushita (Panasonic) varactor – MA393 was selected. This
device has a typical capacitance of 11 pF at 1.0 V and 3.7 pF at 4.0
V and the C–V characteristic is fairly linear over that range.
Similar performance was also acheived with Loral varactors. A
multi–layer chip inductor was used to realize the LT component.
These inductors had typical Q values in the 35 to 50 range for frequencies between 500 and 1000 MHz.
Note: There are many suppliers of high performance varactors
and inductors and Motorola can not recommend one vendor over
another.
The Q (quality factor) of the components in the tank circuit has a
direct impact on the resulting phase noise of the oscillator. In general, the higher the Q, the lower the phase noise of the resulting
oscillator. In addition to the LT and CV components, only high
quality surface–mount RF chip capacitors should be used in the
tank circuit. These capacitors should have very low dielectric loss
(high–Q). At a minimum, the capacitors selected should be operating 100 MHz below their series resonance point. As the desired frequency of operation increases, the values of the C1 and Cb capacitors will decrease since the series resonance point is a function of
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Issue B
LANSDALE Semiconductor, Inc.
ML12149
Legacy Applications Information
9. Evaluate over temperature and voltage limits.
10. Perform worst case analysis of tank component
variation to insure proper VCO operation over full
temperature and voltage range and make any
adjustments as needed.
the capacitance value. To simplify the selection of C1 and Cb, a
table has been constructed based on the intended operating frequency to provide recommended starting points. These may need
to be altered depending on the value of the varactor selected.
Frequency
C1
Cb
200 – 500 MHz
47 pF
47 pF
500 – 900 MHz
5.1 pF
15 pF
900 – 1200 MHz
2.7 pF
15 pF
The value of the Cb capacitor influences the VCO supply pushing. To minimize pushing, the Cb capacitor should be kept small.
Since C1 is in series with the varactor, there is a strong relationship between these two components which influences the VCO
sensitivity. Increasing the value of C1 tends to increase the sensitivity of the VCO.
The parasitic contributions Lp and Cp are related to the
ML12149 as well as parasitics associated with the layout, tank
components, and board material selected. The input capacitance
of the device, bond pad, the wire bond, package/lead capacitance,
wire bond inductance, lead inductance, printed circuit board layout, board dielectric, and proximity to the ground plane all have
an impact on these parasitics. For example, if the ground plane is
located directly below the tank components, a parasitic capacitor
will be formed consisting of the solder pad, metal traces, board
dielectric material, and the ground plane. The test fixture used for
characterizing the device consisted of a two sided copper clad
board with ground plane on the back. Nominal values where
determined by selecting a varactor and characterizing the device
with a number of different tank/frequency combinations and then
performing a curve fit with the data to determine values for Lp
and Cp. The nominal values for the parasitic effects are seen
below:
Parasitic Capacitance
Parasitic Inductance
Cp
Lp
4.2 pF
2.2 nH
These values will vary based on the users unique circuit board
configuration.
Basic Guidelines:
1. Select a varactor with high Q and a reasonable
capacitance versus voltage slope for the desired
frequency range.
2. Select the value of Cb and C1 from the table above.
3. Calculate a value of inductance (L) which will result in
achieving the desired center frequency. Note that L
includes both LT and Lp.
4. Adjust the value of C1 to achieve the proper
VCO sensitivity.
5. Re–adjust value of L to center VCO.
6. Prototype VCO design using selected components. It is
important to use similar construction techniques and
materials, board thickness, layout, ground plane
spacing as intended for the final product.
7. Characterize tuning curve over the voltage
operation conditions.
8. Adjust, as necessary, component values – L, C1, and
Cb to compensate for parasitic board effects.
Page 5 of 12
Outputs Q and QB are open collector outputs and need a inductor to VCC to provide the voltage bias to the output transistor. In
most applications, DC–blocking capacitors are placed in series
with the output to remove the DC component before interfacing to
other circuitry. These outputs are complementary and should have
identical inductor values for each output. This will minimize
switching noise on the VCC supply caused by the outputs switching. It is important that both outputs be terminated, even if only
one of the outputs is used in the application.
Referring to Figure 2, the recommended value for L2a and L2b
should be 47 nH and the inductor components resonance should
be at least 300 MHz greater than the maximum operating frequency. For operation above 1100MHz, it may be necessary to reduce
that inductor value to 33nH. The recommended value for the coupling capacitors C6a, C6b, and C7 is 47 pF. Figure 2 also includes
decoupling capacitors for the supply line as well as decoupling for
the output inductors. Good RF decoupling practices should be
used with a series of capacitors starting with high quality 100pF
chip capacitors close to the device. A typical layout is shown
below in Figure 3.
The output amplitude of the Q and QB can be adjusted using
the CNTL pin. Refering to Figure 1, if the CNTL pin is connected
to ground, additional current will flow through the current source.
When the pin is left open, the nominal current flowing through
the outputs is 4 mA. When the pin is grounded, the current
increases to a nominal value of 10 mA. So if a 50 ohm resistor
was connected between the outputs and VCC, the output amplitude would change from 200 mV pp to 500 mV pp with an additional current drain for the device of 6 mA. To select a value
between 4 and 10 mA, an external resistor can be added to
ground. The equation below is used to calculate the current.
Iout(nom) =
(200 + 136 + Rext) x 0.8V
200 x (136 + Rext)
Figure 4 through Figure 13 illustrate typical performance
achieved with the ML12149. The curves illustrate the tuning
curve, supply pushing characteristics, output power, current drain,
output spectrum, and phase noise performance. In most cases, data
is present for both a 750 MHz and1200 MHz tank design. The
table below illustrates the component values used in the designs.
Component
750MHz Tank
1200MHz Tank
R1
5000
5000
Ω
C1
5.1
2.7
pF
LT
4.7
1.8
nH
CV
3.7 @ 1.0 V
11 @ 4.0 V
3.7 @ 1.0 V
11 @ 4.0 V
pF
Cb
100*
15
pF
C6, C7
47
33
pF
L2
47
47
nH
NOTE:
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Units
* The value of Cb should be reduced to minimize pushing.
Issue B
LANSDALE Semiconductor, Inc.
ML12149
Figure 3. ML12149 Typical Layout
(Not to Scale)
To Prescaler
C3a
C7
C2a
C6a
VCO Output 1
1
R2
R1
L2a
C3b
L2b
C2b
C1
Vtune
LT
Varactor
Cb
VCO Output 2
C6b
= Via to/or Ground Plane
= Via to/or Power Plane
Page 6 of 12
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Issue B
LANSDALE Semiconductor, Inc.
ML12149
Legacy Applications Information
Figure 4. Typical VCO Tuning Curve, 750 MHz Tank
850
825
Frequency of Operation (MHz)
800
775
750
725
700
–40°C
+25°C
+85°C
675
650
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Tuning Voltage (V)
Figure 5. Typical Supply Pushing, 750 MHz Tank
750
748
Frequency of Operation (MHz)
746
744
742
740
738
736
734
–40°C
+25°C
+85°C
732
730
2.7
3.0
3.3
3.6
3.9
4.2
4.5
4.8
5.1
5.4
VCC Supply Voltage (V)
Page 7 of 12
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Issue B
LANSDALE Semiconductor, Inc
ML12149
Legacy Applications Information
Figure 6. Typical Q/QB Output Power versus Supply, 750 MHz Tank
0
–1
–2
Output Power (dBm)
–3
–4
–5
–40°C
+25°C
+85°C
+25°C (LP)
CNTL to GND
–6
–7
–8
–9
CNTL–N/C
–10
2.7
3.0
3.3
3.6
3.9
4.2
4.5
4.8
5.0
VCC Supply Voltage (V)
Figure 7. Typical Current Drain versus Supply, 750 MHz Tank
25
Current Drain (mA)
20
15
CNTL to GND
–40°C
+25°C
+85°C
+25°C (LP)
10
CNTL–N/C
5
2.7
3.0
3.3
3.6
3.9
4.2
4.5
4.8
5.1
5.4
VCC Supply Voltage (V)
Page 8 of 12
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Issue B
LANSDALE Semiconductor, Inc.
ML12149
Legacy Applications Information
Figure 8. Typical VCO Tuning Curve, 1200 MHz Tank
(VCC = 5.0 V)
1300
Frequency of Operation (MHz)
1275
1250
1225
1200
1175
–40°C
+25°C
+85°C
1150
0
0.6
1.2
1.8
2.4
3.0
3.6
4.2
4.8
Tuning Voltage (V)
Figure 9. Typical Supply Pushing, 1200 MHz Tank
1210
1208
Frequency of Operation (MHz)
1206
1204
1202
1200
1198
1196
1194
–40°C
+25°C
+85°C
1192
1190
2.7
3.0
3.3
3.6
3.9
4.2
4.5
4.8
5.1
5.4
VCC Supply Voltage (V)
Page 9 of 12
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Issue B
LANSDALE Semiconductor, Inc
ML12149
Legacy Applications Information
Figure 10. Q/QB Output Power versus Supply, 1200 MHz Tank
2
1
Output Power (dBm)
0
–1
–2
–3
–40°C
+25°C
+85°C
–4
2.7
3.0
3.3
3.6
3.9
4.2
4.5
4.8
5.0
VCC Supply Voltage (V)
Figure 11. Typical VCO Output Spectrum
0
ATTEN 10
RL 0dBm
MARKER
909MHz –7.1dBm
10dB/
–10
–20
AMPLITUDE (dBm)
–30
–40
–50
–60
–70
–80
–90
–100
Page 10 of 12
START 10MHz
RBW 1.0MHz
STOP 10.0GHz
SWP 200ms
VBW 1.0MHz
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LANSDALE Semiconductor, Inc.
ML12149
Legacy Applications Information
Figure 12. Typical Phase Noise Plot, 750 MHz Tank
0
HP 3048A
CARRIER
784.2MHz
–25
dBc/Hz
–50
–75
–100
–125
–150
–170
100
1K
10K
100K
1M
10M
40M
10M
40M
(f) [dBc/Hz] vs f[Hz]
Figure 13. Typical Phase Noise Plot, 1200 MHz Tank
HP 3048A
CARRIER
1220MHz
0
–25
dBc/Hz
–50
–75
–100
–125
–150
–170
100
1K
10K
100K
1M
(f) [dBc/Hz] vs f[Hz]
Page 11 of 12
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LANSDALE Semiconductor, Inc
ML12149
OUTLINE DIMENSIONS
D
A
8
E
B
SO 8 = -5P
(ML12149-5P)
PLASTIC PACKAGE
CASE 751–06
(SO–8)
ISSUE T
5
0.25
H
1
M
B
M
4
h
e
X 45°
θ
A
C
SEATING
PLANE
L
0.10
A1
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME
Y14.5M, 1994.
2. DIMENSIONS ARE IN MILLIMETER.
3. DIMENSION D AND E DO NOT INCLUDE MOLD
PROTRUSION.
4. MAXIMUM MOLD PROTRUSION 0.15 PER SIDE.
5. DIMENSION B DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOW ABLE DAMBAR
PROTRUSION SHALL BE 0.127 TOTAL IN EXCESS
OF THE B DIMENSION AT MAXIMUM MATERIAL
CONDITION.
C
B
0.25
M
C B
S
A
S
DIM
A
A1
B
C
D
E
e
H
h
L
MILLIMETERS
MIN
MAX
1.35
1.75
0.10
0.25
0.35
0.49
0.19
0.25
4.80
5.00
3.80
4.00
1.27 BSC
5.80
6.20
0.25
0.50
0.40
1.25
0
Lansdale Semiconductor reserves the right to make changes without further notice to any products herein to improve reliability, function or design. Lansdale does not assume any liability arising out of the application or use of any product or circuit
described herein; neither does it convey any license under its patent rights nor the rights of others. “Typical” parameters which
may be provided in Lansdale data sheets and/or specifications can vary in different applications, and actual performance may
vary over time. All operating parameters, including “Typicals” must be validated for each customer application by the customer’s
technical experts. Lansdale Semiconductor is a registered trademark of Lansdale Semiconductor, Inc.
Page 12 of 12
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Issue B