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PDF MAX2754 Data sheet ( Hoja de datos )
| Número de pieza | MAX2754 | |
| Descripción | 1.2GHz VCO with Linear Modulation Input | |
| Fabricantes | Maxim Integrated | |
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19-2102; Rev 2; 5/06
EVAALVUAAILTAIOBNLEKIT
1.2GHz VCO with Linear
Modulation Input
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.
Applications
HomeRF WLAN
Bluetooth
2.4GHz Cordless Phones
2.4GHz Wireless Data Radios
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
PART
MAX2754EUA
Ordering Information
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.
Typical Operating Circuit
330nF
VREG
REG AND BIAS
VCC
VCC
330nF
TOP VIEW
Pin Configuration
VREG 1
TUNE 2
GND1 3
MOD 4
MAX2754
µMAX
8 VCC
7 OUT
6 GND2
5 SHDN
TUNE
TUNE
OSCILLATOR
CORE
GND1
MODULATION
VOLTAGE
SIGNAL
MOD
MAX2754
LINEAR
MODULATION
INTERFACE
OUT
OUT TO
MIXER/
SYNTHESIZER
GND2
SHDN SHDN
________________________________________________________________ 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 page  
1.2GHz VCO with Linear
Modulation Input
Pin Description
PIN NAME
FUNCTION
1
VREG
Capacitor Connection to the On-Chip Linear Regulator Output. Connect a 330nF capacitor to ground.
2
TUNE
Oscillator Frequency Tuning-Voltage Input. High-impedance input with a voltage range of +0.4V (low
frequency) to +2.4V (high frequency).
3
GND1
Ground Connection for the Oscillator Core. Requires a low-inductance connection to the circuit-
board ground plane.
4
MOD
Linear Modulation Input. High-impedance CMOS input with a voltage range of +0.4V to +2.4V.
5
SHDN
Shutdown Input. Drive logic low to place the device in shutdown mode. Drive logic high for normal
operation.
6
GND2
Ground Connection for Output-Buffered Amplifier, Linear Modulation Interface, and Biasing.
Requires a low-inductance connection to the circuit-board ground plane.
7
OUT
Buffered Oscillator Output. Incorporates an internal DC-blocking capacitor. OUT is internally
matched to 50Ω.
8
VCC
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.
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/dVMOD) 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 VMOD 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 VMOD charac-
teristic of the modulation input. Note the negative slope
of the curve, dfMOD/dVMOD < 0, where fMOD = fOUT -
fNOM.
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
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| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet MAX2754.PDF ] | |
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