19-2102; Rev 2; 5/06
KIT
ATION
EVALU
BLE
AVAILA
1.2GHz VCO with Linear
Modulation Input
Features
♦
Fully Monolithic VCO Construction with On-Chip
Inductor and Varactor Tuning Elements
♦
Guaranteed 1145MHz to 1250MHz Tuning Range
to Support 1/2 LO Applications
♦
Modulation Linearity Within ±4%
♦
Precise Modulation Gain (-500kHz/V)
♦
Low Phase Noise (-137dBc/Hz at 4MHz offset)
♦
+2.7V to +5.5V Single-Supply Operation
♦
Low-Current Shutdown Mode
♦
Miniature 8-Pin µMAX
®
Package
General Description
The MAX2754 self-contained, linear modulation, volt-
age-controlled oscillator (VCO) is intended for use in
the 2.4GHz to 2.5GHz ISM band, particularly for FSK
modulation systems that utilize a direct frequency-mod-
ulation transmit architecture. This device features a lin-
ear modulation input in addition to the standard
frequency tuning input. The frequency tuning range of
1145MHz to 1250MHz (1/2 LO) also supports an IF up
to 110MHz with low side LO. The VCO is based on
Maxim’s proprietary monolithic VCO technology, where
all VCO components are integrated on-chip, including
the varactor and inductor.
The MAX2754 linear modulation input offers a means to
directly FM modulate the VCO with a constant modula-
tion sensitivity over the tuning voltage input range.
Typical frequency deviation is -500kHz/V which is linear
to ±4% over the guaranteed frequency limits. The tun-
ing input voltage range is +0.4V to +2.4V and the oscil-
lator frequency is factory adjusted to provide
guaranteed limits. The oscillator signal is buffered by
an output amplifier stage (internally matched to 50Ω) to
provide higher output power and isolate the oscillator
from load impedance variations.
The MAX2754 operates over a +2.7V to +5.5V supply
range. This device also provides a digitally controlled
shutdown mode to permit implementation of sophisti-
cated power-supply management. In shutdown, the
supply current is reduced to 0.2µA. Even when active,
power consumption is a modest 41mW.
The MAX2754 is packaged in the miniature 8-pin µMAX
to offer the world’s smallest, complete 2.4GHz direct-
modulation VCO solution.
MAX2754
Ordering Information
PART
MAX2754EUA
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
8 µMAX
8-pin µMAX
(3mm
✕
5mm)
µMAX is a registered trademark of Maxim Integrated Circuits, Inc.
Applications
HomeRF WLAN
Bluetooth
2.4GHz Cordless Phones
2.4GHz Wireless Data Radios
VREG
330nF
Typical Operating Circuit
V
CC
REG AND BIAS
V
CC
330nF
Pin Configuration
TOP VIEW
TUNE
TUNE
OSCILLATOR
CORE
OUT
OUT TO
MIXER/
SYNTHESIZER
GND1
GND2
LINEAR
MODULATION
INTERFACE
VREG
TUNE
GND1
MOD
1
2
3
4
8
V
CC
OUT
GND2
SHDN
MODULATION
VOLTAGE
SIGNAL
MOD
SHDN
SHDN
MAX2754
7
6
5
µMAX
MAX2754
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1.2GHz VCO with Linear
Modulation Input
MAX2754
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ...........................................................-0.3V to +6.0V
VREG to GND ........................................................-0.3V to +6.0V
TUNE,
SHDN,
MOD to GND.......................-0.3V to (V
CC
+ 0.3V)
OUT to GND ..........................................................-0.3V to +6.0V
Continuous Power Dissipation (T
A
= +70°C)
8-Pin µMAX (derate 5.7mW/°C above T
A
= +70°C) ....457mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
CAUTION!
ESD SENSITIVE DEVICE
DC ELECTRICAL CHARACTERISTICS
(V
CC
= +2.7V to +5.5V, V
TUNE
= +0.4V to +2.4V, V
SHDN
≥
+2.0V, V
MOD
= +1.4V, OUT is connected to a 50Ω load, T
A
= -40°C to
+85°C. Typical values are at V
CC
= +3.0V, T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
Supply Voltage
Supply Current
Digital Input Voltage High
Digital Input Voltage Low
Digital Input Current High
Digital Input Current Low
Modulation Input Voltage Range
TUNE Leakage Current (Note 2)
SYMBOL
V
CC
T
A
= +25°C, V
SHDN
≥
2.0V
I
CC
V
IH
V
IL
I
IH
I
IL
V
MOD
V
TUNE
= +0.4V to +2.4V
V
SHDN
≥
2.0V
V
SHDN
≤
0.6V
-2
-1
0.4
0.01
T
A
= -40°C to +85°C, V
SHDN
≥
2.0V
V
SHDN
≤
0.6V
-2
2.0
0.6
2
1
2.4
0.2
CONDITIONS
MIN
2.7
13.7
TYP
MAX
5.5
19
20
2
UNITS
V
mA
µA
V
V
µA
µA
V
nA
AC ELECTRICAL CHARACTERISTICS
(MAX2754 EV kit. V
CC
= +2.7V to +5.5V, V
TUNE
= +0.4V to +2.4V, V
SHDN
≥
+2.0V, V
MOD
= +1.4V, OUT is connected to a 50Ω load,
T
A
= +25°C. Typical values are at V
CC
= +3.0V, T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
Oscillator Guaranteed Frequency
Limits
Phase Noise
Tuning Gain
Output Power
Modulation Peak Frequency
Deviation
Modulation Sensitivity
f
MIN
< f < f
MAX
(Note 2)
Common-mode V
MOD
= 1.4V
±400
SYMBOL
fMIN,
fMAX
CONDITIONS
V
TUNE
= +0.4V to +2.4V,
T
A
= -40°C to +85°C
f
OFFSET
= 4MHz
Noise floor
V
TUNE
at f
MIN
V
TUNE
at f
MAX
MIN
1145
-137
-151
124
81
-5
±500
-500
±600
TYP
MAX
1250
UNITS
MHz
dBc/Hz
dBm/Hz
MHz/V
dBm
kHz
kHz/V
2
_______________________________________________________________________________________
1.2GHz VCO with Linear
Modulation Input
AC ELECTRICAL CHARACTERISTICS (continued)
(MAX2754 EV kit. V
CC
= +2.7V to +5.5V, V
TUNE
= +0.4V to +2.4V, V
SHDN
≥
+2.0V, V
MOD
= +1.4V, OUT is connected to a 50Ω load,
T
A
= +25°C. Typical values are at V
CC
= +3.0V, T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
Modulation Linearity
Modulation Full-Power Bandwidth
(Note 5)
Return Loss (Note 6)
Output Harmonics
Load Pulling
Supply Pushing
Oscillator Turn-On Time (Note 7)
Oscillator Turn-Off Time (Note 8)
VSWR = 2:1, all phases
V
CC
stepped: +3.3V to +2.8V
f
MIN
< f < f
MAX
SYMBOL
CONDITIONS
V
MOD
= +0.4 to +2.4V,
f
MIN
< f < f
MAX
(Note 4)
MIN
TYP
±4
2.5
7.5
-20
1.5
0.16
10
8
MAX
UNITS
%
MHz
dB
dBc
MHz
p-p
MHz/V
µs
µs
MAX2754
Specifications are production tested at T
A
= +25°C. Limits over temperature are guaranteed by design and characterization.
Limits are guaranteed by production test at +25°C.
Center point is nominally +1.4V.
Maximum variation in the modulation sensitivity from its average value over the guaranteed frequency limits.
Bandwidth is defined as the point where the response to the modulation port is 0.707 times the low-frequency response.
Bandwidth limits on the modulation input for a 1Vp-p sine wave. Common-mode V
MOD
= +1.4V.
Note 6:
Refer to
Output Buffer
section for suggestions to improve the return loss to 12dB.
Note 7:
Turn-on time to within 3dB of final output power.
Note 8:
Turn-off time to output power of -10dBm.
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
_______________________________________________________________________________________
3
1.2GHz VCO with Linear
Modulation Input
MAX2754
Typical Operating Characteristics
(MAX2754 EV kit, V
CC
= +3.0V, V
SHDN
≥
+2.0V, V
TUNE
= V
MOD
= +1.4V, and T
A
= +25°C, unless otherwise noted.)
VCO TUNING CURVE
MAX2754 toc01
1350
1300
1250
FREQUENCY (MHz)
1200
1150
1100
1050
1000
950
0
0.5
1.0
1.5
V
TUNE
(V)
2.0
2.5
T
A
= +85°C
T
A
= +25°C
T
A
= -40°C
MODULATION SENSITIVITY vs.
CARRIER FREQUENCY
MAX2754 toc02
TUNE INPUT CURRENT
vs. TEMPERATURE
MAX2754 toc03
-400
-420
MODULATION SENSITIVITY (kHz/V)
-440
-460
-480
-500
-520
-540
-560
-580
T
A
= +85°C
1140
1160
1180
1200
T
A
= +25°C
T
A
= -40°C
1.0
TUNING INPUT CURRENT (nA)
0.8
0.6
0.4
0.2
3.0
-600
1220
1240
1260
CARRIER FREQUENCY (MHz)
0
-40
-15
10
35
60
85
TEMPERATURE (°C)
OUTPUT POWER vs. FREQUENCY
MAX2754 toc04
-3.0
-3.5
OUTPUT POWER (dBm)
-4.0
-4.5
V
CC
= +4.0V
-5.0
-5.5
-6.0
1140
1160
1180
1200
1220
1240
V
CC
= +2.7V
V
CC
= +5.5V
OUTPUT POWER
vs. FREQUENCY
MAX2754 toc05
NORMALIZED HARMONIC
OUTPUT SPECTRUM
MAX2754 toc06
-2
-3
OUTPUT POWER (dBm)
-4
-5
T
A
= +25°C
-6
-7
T
A
= -40°C
T
A
= +85°C
∆
= -20dBc
OUTPUT POWER (dBm)
∆
= -30dBc
1260
-8
1140
1160
1180
1200
1220
1240
1260
ƒ
O
2ƒ
O
FREQUENCY
3ƒ
O
FREQUENCY (MHz)
FREQUENCY (MHz)
PHASE NOISE
MAX2754 toc07
OSCILLATOR TURN-ON/
TURN-OFF TIME
MAX2754 toc08
OUTPUT S
11
MAX2754 toc09
-60
-70
-80
PHASE NOISE (dBc/Hz)
-90
-100
-110
-120
-130
-140
-150
-160
10
100
1000
0
-10
-20
OUTPUT POWER (dBm)
-30
-40
-50
-60
-70
-80
-90
-100
SHDN HIGH-TO-LOW
AT TIME = 0
SHDN LOW-TO-HIGH
AT TIME = 0
0
-5
S
11
(dB)
50
-10
-15
-20
0
10
20
30
40
800 900 1000 1100 1200 1300 1400 1500 1600
FREQUENCY (MHz)
TIME (µs)
10,000
OFFSET FREQUENCY (kHz)
4
_______________________________________________________________________________________
1.2GHz VCO with Linear
Modulation Input
Pin Description
PIN
1
2
3
4
5
6
7
8
NAME
VREG
TUNE
GND1
MOD
SHDN
GND2
OUT
V
CC
FUNCTION
Capacitor Connection to the On-Chip Linear Regulator Output. Connect a 330nF capacitor to ground.
Oscillator Frequency Tuning-Voltage Input. High-impedance input with a voltage range of +0.4V (low
frequency) to +2.4V (high frequency).
Ground Connection for the Oscillator Core. Requires a low-inductance connection to the circuit-
board ground plane.
Linear Modulation Input. High-impedance CMOS input with a voltage range of +0.4V to +2.4V.
Shutdown Input. Drive logic low to place the device in shutdown mode. Drive logic high for normal
operation.
Ground Connection for Output-Buffered Amplifier, Linear Modulation Interface, and Biasing.
Requires a low-inductance connection to the circuit-board ground plane.
Buffered Oscillator Output. Incorporates an internal DC-blocking capacitor. OUT is internally
matched to 50Ω.
Supply Voltage Connection. Requires external RF bypass capacitor to ground for low noise and low
spurious content performance from the oscillator. Bypass with a 330pF capacitor to ground.
MAX2754
Detailed Description
Oscillator
The MAX2754 VCO is implemented as an LC oscillator
topology, integrating all of the tank components on-
chip. This fully monolithic approach provides an
extremely easy-to-use VCO, equivalent to a VCO mod-
ule. The frequency is controlled by a voltage applied to
the TUNE pin. The VCO core uses a differential topolo-
gy to provide a stable frequency versus supply voltage
and improve the immunity to load variations. In addi-
tion, there is a buffer amplifier following the oscillator
core to provide added isolation from load and supply
variations and to boost the output power.
Linear Modulation
The linear modulation input offers a means to directly
FM modulate the VCO with a controlled amount of fre-
quency deviation for a given input voltage deviation.
The unique technique maintains a consistent modula-
tion gain (df/dV
MOD
) across the entire frequency tuning
range of the part, enabling accurate FM modulation
derived solely from the filtered NRZ “data” stream (the
modulation voltage input).
The modulation input is single-ended and centered
about +1.4V. The linear modulation full-scale range is
±1V around this point, for a +0.4V to +2.4V input volt-
age range. A very important point to note is that the
sign of the modulation gain is negative. A positive
change in V
MOD
results in a negative change in oscilla-
tion frequency. This convention for the modulation gain
is due to the practical implementation of the internal lin-
earizing circuitry. This gain inversion must be consid-
ered when designing the analog voltage interface that
drives the linear modulation input. The easiest way to
handle this is to invert the logic polarity of the modula-
tion data three-state output buffer (TX data output).
Where it is impossible to invert the data-stream logic
polarity, an external inverter and three-state buffer
would be required. These devices are offered in small
single-logic gates in SC-79 style packages from various
manufacturers (e.g., Fairchild—Tiny Logic, On
Semiconductor, or Rohm).
Figure 1 illustrates the frequency versus V
MOD
charac-
teristic of the modulation input. Note the negative slope
of the curve, df
MOD
/dV
MOD
< 0, where f
MOD
= f
OUT
-
f
NOM
.
Output Buffer
The oscillator signal from the core drives an output
buffer amplifier. The amplifier is internally matched to
50Ω including an on-chip DC-blocking capacitor. The
return loss can be improved to a minimum of 12dB over
1145MHz to 1250MHz by adding a 2.5nH series induc-
tor and a 3.0pF shunt capacitor. The output buffer has
a ground connection separate from the oscillator core
to minimize load-pulling effects. The amplifier boosts
the oscillator signal to a level suitable for driving most
RF mixers.
_______________________________________________________________________________________
5
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
