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19-2102; Rev 1; 8/03
KIT ATION EVALU ILABLE AVA
1.2GHz VCO with Linear Modulation Input
Features
o Fully Monolithic VCO Construction with On-Chip Inductor and Varactor Tuning Elements o Guaranteed 1145MHz to 1250MHz Tuning Range to Support 1/2 LO Applications o Modulation Linearity Within 4% o Precise Modulation Gain (-500kHz/V) o Low Phase Noise (-137dBc/Hz at 4MHz offset) o +2.7V to +5.5V Single-Supply Operation o Low-Current Shutdown Mode o Miniature 8-Pin MAX Package
General Description
The MAX2754 self-contained, linear modulation, voltage-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-modulation transmit architecture. This device features a linear 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 modulation sensitivity over the tuning voltage input range. Typical frequency deviation is -500kHz/V which is linear to 4% over the guaranteed frequency limits. The tuning input voltage range is +0.4V to +2.4V and the oscillator frequency is factory adjusted to provide guaranteed limits. The oscillator signal is buffered by an output amplifier stage (internally matched to 50) 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 sophisticated power-supply management. In shutdown, the supply current is reduced to 0.2A. Even when active, power consumption is a modest 41mW. The MAX2754 is packaged in the miniature 8-pin MAX to offer the world's smallest, complete 2.4GHz directmodulation VCO solution.
MAX2754
Ordering Information
PART MAX2754EUA TEMP RANGE -40C to +85C PIN-PACKAGE 8 MAX
8-pin MAX
(3mm 5mm)
Applications
HomeRF WLAN Bluetooth 2.4GHz Cordless Phones 2.4GHz Wireless Data Radios
330nF VREG
Typical Operating Circuit
VCC REG AND BIAS VCC 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
VCC OUT GND2 SHDN
MODULATION VOLTAGE SIGNAL MOD SHDN SHDN
MAX2754
7 6 5
MAX
MAX2754
________________________________________________________________ Maxim Integrated Products
1
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1.2GHz VCO with Linear Modulation Input MAX2754
ABSOLUTE MAXIMUM RATINGS
VCC to GND ...........................................................-0.3V to +6.0V VREG to GND ........................................................-0.3V to +6.0V TUNE, SHDN, MOD to GND.......................-0.3V to (VCC + 0.3V) OUT to GND ..........................................................-0.3V to +6.0V Continuous Power Dissipation (TA = +70C) 8-Pin MAX (derate 5.7mW/C above TA = +70C) ....457mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10s) .................................+300C
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
(VCC = +2.7V to +5.5V, VTUNE = +0.4V to +2.4V, V SHDN +2.0V, VMOD = +1.4V, OUT is connected to a 50 load, TA = -40C to +85C. Typical values are at VCC = +3.0V, TA = +25C, 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 VCC TA = +25C, V SHDN 2.0V ICC VIH VIL IIH IIL VMOD VTUNE = +0.4V to +2.4V V SHDN 2.0V V SHDN 0.6V -2 -1 0.4 0.01 TA = -40C to +85C, 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 16.4 20 2 UNITS V mA A V V A A V nA
AC ELECTRICAL CHARACTERISTICS
(MAX2754 EV kit. VCC = +2.7V to +5.5V, VTUNE = +0.4V to +2.4V, V SHDN +2.0V, VMOD = +1.4V, OUT is connected to a 50 load, TA = +25C. Typical values are at VCC = +3.0V, TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER Oscillator Guaranteed Frequency Limits Phase Noise Tuning Gain Output Power Modulation Peak Frequency Deviation Modulation Sensitivity fMIN < f < fMAX (Note 2) Common-mode VMOD = 1.4V 400 SYMBOL fMIN, fMAX CONDITIONS VTUNE = +0.4V to +2.4V, TA = -40C to +85C fOFFSET = 4MHz Noise floor VTUNE at fMIN VTUNE at fMAX 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
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1.2GHz VCO with Linear Modulation Input
AC ELECTRICAL CHARACTERISTICS (continued)
(MAX2754 EV kit. VCC = +2.7V to +5.5V, VTUNE = +0.4V to +2.4V, V SHDN +2.0V, VMOD = +1.4V, OUT is connected to a 50 load, TA = +25C. Typical values are at VCC = +3.0V, TA = +25C, 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 VCC stepped: +3.3V to +2.8V fMIN < f < fMAX SYMBOL CONDITIONS VMOD = +0.4 to +2.4V, fMIN < f < fMAX (Note 4) MIN TYP 4 2.5 7.5 -20 1.5 0.16 10 8 MAX UNITS % MHz dB dBc MHzp-p MHz/V s s
MAX2754
Specifications are production tested at TA = +25C. Limits over temperature are guaranteed by design and characterization. Limits are guaranteed by production test at +25C. 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 VMOD = +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:
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3
1.2GHz VCO with Linear Modulation Input MAX2754
Typical Operating Characteristics
(MAX2754 EV kit, VCC = +3.0V, V SHDN +2.0V, VTUNE = VMOD = +1.4V, and TA = +25C, 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 VTUNE (V) 2.0 2.5 TA = +85C TA = +25C TA = -40C
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 TA = +85C 1140 1160 1180 1200 TA = +25C TA = -40C
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 VCC = +4.0V -5.0 -5.5 -6.0 1140 1160 1180 1200 1220 1240 VCC = +2.7V VCC = +5.5V
OUTPUT POWER vs. FREQUENCY
MAX2754 toc05
NORMALIZED HARMONIC OUTPUT SPECTRUM
MAX2754 toc06
-2 -3 OUTPUT POWER (dBm) -4 -5 TA = +25C -6 -7 TA = -40C TA = +85C
= -20dBc OUTPUT POWER (dBm) = -30dBc
1260
-8 1140 1160 1180 1200 1220 1240 1260 O 2O FREQUENCY 3O FREQUENCY (MHz)
FREQUENCY (MHz)
PHASE NOISE
MAX2754 toc07
OSCILLATOR TURN-ON/ TURN-OFF TIME
MAX2754 toc08
OUTPUT S11
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 S11 (dB) 50
-10
-15
-20 0 10 20 30 40 800 900 1000 1100 1200 1300 1400 1500 1600 FREQUENCY (MHz) TIME (s)
10,000
OFFSET FREQUENCY (kHz)
4
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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 VCC 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 circuitboard 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 50. 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 onchip. This fully monolithic approach provides an extremely easy-to-use VCO, equivalent to a VCO module. The frequency is controlled by a voltage applied to the TUNE pin. The VCO core uses a differential topology to provide a stable frequency versus supply voltage and improve the immunity to load variations. In addition, there is a buffer amplifier following the oscillator core to provide added isolation from load and supply variations and to boost the output power.
tion frequency. This convention for the modulation gain is due to the practical implementation of the internal linearizing circuitry. This gain inversion must be considered 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 modulation 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 characteristic of the modulation input. Note the negative slope of the curve, dfMOD/dVMOD < 0, where fMOD = fOUT fNOM.
Linear Modulation
The linear modulation input offers a means to directly FM modulate the VCO with a controlled amount of frequency deviation for a given input voltage deviation. The unique technique maintains a consistent modulation 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 voltage 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-
Output Buffer
The oscillator signal from the core drives an output buffer amplifier. The amplifier is internally matched to 50 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 inductor 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.
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5
1.2GHz VCO with Linear Modulation Input MAX2754
Applications Information
Tune Input
The tuning input is typically connected to the output of the PLL loop filter. The loop filter provides an appropriately low-impedance source. Incorporate an extra RC filter stage to reduce high-frequency noise and spurious signals. Any excess noise on the tuning input is directly translated into FM noise, which can degrade the phase-noise performance of the oscillator. Therefore, it is important to minimize the noise introduced on the tuning input. A simple RC filter with low corner frequency is needed during testing to filter the noise present on the voltage source driving the tuning line.
fNOM + fMOD OUTPUT FREQUENCY (MHz)
fNOM
fNOM - fMOD 0.5 1.0 1.5 2.0 2.5
Two-Level FSK Applications
The MAX2754 is designed for use in FSK applications operating in the 2.4GHz to 2.5GHz ISM band. Specifically, it is targeted for those systems which utilize a direct TX modulation architecture in which the VCO is directly modulated with the data signal during the transmit (TX) mode. The VCO in these systems runs at half the RF output frequency and is used in conjunction with a frequency doubler to produce the final LO signal for both RX and TX modes of operation.
MODULATION VOLTAGE, VMOD (V)
Figure 1. Modulation Frequency Deviations Characteristics
Figure 2 shows a typical applications circuit. To compute R1, R2, R3, and R4, determine the modulation voltage center point (VMODB = +1.4V). Compute the required modulation voltage deviation as follows:
VCC VREG 330nF REG AND BIAS VCC 330nF
VCC R1 INVERTED CMOS SIGNAL R2
FROM PLL LOOP FILTER
TUNE
OSCILLATOR CORE
OUT
OUT TO MIXER/ SYNTHESIZER
GND1 R3 MOD. FILTER MOD R4 LINEAR MODULATION INTERFACE MAX2754
GND2
SHDN
FROM BASEBAND DIGITAL CONTROLLER
Figure 2. Typical Application Circuit for Two-Level FSK
6
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1.2GHz VCO with Linear Modulation Input
V = f / 500kHz/V (nominal modulation sensitivity) Let R = R1 + R3 + R4. Setting R based on the desired current from VCC and filter impedance level: R1 = , 2 V R R2 = MODB - 1 x , V 4 1 V R 3 = R x - MODB , VCC 2 R4 = VMODB VCC xR R
Layout Issues
Use controlled impedance lines (microstrip, co-planar waveguide, etc.) each time for high-frequency signals. Always place decoupling capacitors as close to the VCC pins as possible; for long VCC lines, it may be necessary to add additional decoupling capacitors located further from the device. Always provide a low-inductance path to ground, and keep GND vias as close to the device as possible. Thermal reliefs on GND pads are not recommended.
MAX2754
Chip Information
TRANSISTOR COUNT: 619
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1.2GHz VCO with Linear Modulation Input MAX2754
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
8LUMAXD.EPS
4X S
8
8
INCHES DIM A A1 A2 b MIN 0.002 0.030 MAX 0.043 0.006 0.037
MILLIMETERS MAX MIN 0.05 0.75 1.10 0.15 0.95
y 0.500.1
E
H
0.60.1
c D e E H L
1
1
0.60.1
S
D
BOTTOM VIEW
0.014 0.010 0.007 0.005 0.120 0.116 0.0256 BSC 0.120 0.116 0.198 0.188 0.026 0.016 6 0 0.0207 BSC
0.25 0.36 0.13 0.18 2.95 3.05 0.65 BSC 2.95 3.05 4.78 5.03 0.41 0.66 0 6 0.5250 BSC
TOP VIEW
A2
A1
A
c e b L
SIDE VIEW
FRONT VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL DOCUMENT CONTROL NO. REV.
21-0036
1 1
J
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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