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19-0425; Rev 1; 9/95
KIT ATION EVALU LE VAILAB A
3V, Ultra-Low-Power Quadrature Modulator
____________________________Features
o IF Output Frequency up to 80MHz o Input Bandwidth up to 15MHz o On-Chip Oscillator with External Tuning Circuit o On-Chip Divide-by-8 Prescaler o Integrated Quadrature Phase Shifters o Self-Biased Differential Baseband Inputs o CMOS-Compatible Enable o 4.1mA Operating Supply Current 2A Shutdown Supply Current
_______________General Description
The monolithic MAX2452 is a quadrature modulator with supporting oscillator and divide-by-8 prescaler. It operates from a single +3V supply and draws only 4.1mA. The modulator accepts differential I and Q baseband signals with amplitudes up to 1.35Vp-p and bandwidths up to 15MHz. It produces a differential output up to 80MHz. Pulling the CMOS-compatible ENABLE pin low reduces the supply current to 2A. To minimize spurious feedback, the MAX2452's internal oscillator is set at twice the IF via external tuning components. The oscillator and associated phase shifters produce differential signals exhibiting low amplitude and phase imbalance, yielding 42dB sideband rejection. The MAX2452 comes in a 16-pin narrow SO package.
MAX2452
________________________Applications
Digital Cordless Phones GSM and North American Cellular Phones Wireless LANs Digital Communications Two-Way Pagers
______________Ordering Information
PART MAX2452ISE* TEMP. RANGE -20C to +85C PIN-PACKAGE 16 Narrow SO
* An alternate marking, MAX2452CSE, has been identically tested.
________________Functional Diagram
__________________Pin Configuration
LO_VCC 11 8 9 10 LOCAL OSCILLATOR /2 PRESCALER 0 /4 12 PRE_OUT
TOP VIEW
TANK TANK LO_GND IF 1 GND 2 I3 I4 Q5 Q6 ENABLE 7 TANK 8 16 IF 15 GND 14 VCC I I Q Q VCC
QUADRATURE PHASE GENERATOR 90 /2
3 4 MODULATOR 5 6 14 MASTER BIAS BANDGAP BIAS 16
MAX2452
13 N.C. 12 PRE_OUT 11 LO_VCC 10 LO_GND 9 TANK
IF IF
1
MAX2452
SO
2, 15 GND
7 ENABLE
________________________________________________________________ Maxim Integrated Products
1
Call toll free 1-800-998-8800 for free samples or literature.
3V, Ultra-Low-Power Quadrature Modulator MAX2452
ABSOLUTE MAXIMUM RATINGS
VCC, LO_VCC to GND............................................-0.3V to +4.5V ENABLE, TANK, TANK, I, I, Q, Q to GND ..................VCC + 0.3V Continuous Power Dissipation (TA = +70C) SO (derate 8.33mW/C above +70C) ..........................667mW Operating Temperature Range ...........................-20C to +85C Storage Temperature Range ............................-65C to +165C Lead Temperature (soldering, 10sec) .............................+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.
DC ELECTRICAL CHARACTERISTICS
(VCC = LO_VCC = 2.7V to 3.3V, TA = -20C to +85C, unless otherwise noted.) PARAMETER Supply Voltage Range Supply Current Shutdown Supply Current Enable/Disable Time ENABLE Bias Current ENABLE Low Voltage ENABLE High Voltage IF Voltage Level IF Voltage Level TANK Voltage Level TANK Voltage Level I, I, Q, Q Voltage Level Differential Input Impedance SYMBOL VCC, LO_VCC ICC ON ICC OFF tON/OFF IEN VENL VENH VIF V IF VTANK V TANK V I , V I , VQ , V Q ZII, ZQQ VCC - 0.4 VCC - 1.7 VCC - 1.7 LO_VCC - 1.1 LO_VCC - 1.1 1.25 35 1.5 44 VCC - 1.35 VCC - 1.35 LO_VCC - 0.8 LO_VCC - 0.8 1.75 Enable = VCC - 0.4V Enable = VCC - 0.4V Enable = 0.4V CONDITIONS MIN 2.7 4.1 2 10 1 10 0.4 TYP MAX 3.3 7 20 UNITS V mA A s A V V V V V V V k
AC ELECTRICAL CHARACTERISTICS
(VCC = LO_VCC = 3.0V, fOSC = 140MHz, ENABLE = 2.6V, fII = fQQ = 600kHz, TA = -20C to +85C, unless otherwise noted.) PARAMETER Differential Input Voltage I and Q Signal Bandwidth IF Differential Output Voltage I/Q Amplitude Match I/Q Phase Match Sideband Rejection LO Leakage at Output Oscillator Frequency Range PRE_OUT Output Voltage PRE_OUT Slew Rate fOSC VPRE_OUT SRPRE_OUT VII = VQQ = 1.2Vp-p (Notes 1, 2) RL = 10k, CL < 6pF RL = 10k, CL < 6pF, rising edge, TA = +25C 70 SYMBOL VIIp-p, VQQp-p BWIQ VIFIFp-p (Note 1) (Note 1) VII = VQQ = 1.2Vp-p, RL = 200k differential, CL < 5pF differential 65 <0.3 <3 42 -36 140 0.35 60 160 CONDITIONS MIN TYP 1.2 MAX 1.35 15 UNITS Vp-p MHz mVp-p dB degrees dB dBc MHz Vp-p V/s
Note 1: Guaranteed by design, not tested. Note 2: The frequency range can be extended in either direction, but has not been characterized. At higher frequencies, the IF output level may decrease and distortions may increase. 2 _______________________________________________________________________________________
3V, Ultra-Low-Power Quadrature Modulator
__________________________________________Typical Operating Characteristics
(VCC = LO_VCC = 3.0V, fOSC = 140MHz, ENABLE = 2.6V, fII = fQQ = 600kHz, RL (IF, IF) = 200k differential, CL (IF, IF) < 5pF differential, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
4.8 4.7 4.6 4.5 4.4 4.3 4.2 4.1 4.0 3.9 3.8 3.7 3.6 3.5 -30
MAX2452-01
MAX2452
SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
MAX2452-02
IF OUTPUT vs. BASEBAND INPUT
MAX2452-03
16 14 SUPPLY CURRENT (A) 12 10 8 6 4 2 0 -30 VCC = 2.7V VCC = 3V VCC = 3.3V
-30 -34 OUTPUT (dBVRMS) -38 -42 -46 -50 -54
dBVRMS 20
SUPPLY CURRENT (mA)
VCC = 3.3V VCC = 3V VCC = 2.7V
Vp-p = 2 2 x 10
(V)
-10
10
30
50
70
90
-10
10
30
50
70
90
-26
-22
-18
-14
-10
-6
TEMPERATURE (C)
TEMPERATURE (C)
BASEBAND INPUT (dBVRMS)
IF OUTPUT vs. SUPPLY VOLTAGE
MAX2452-04
IF OUTPUT vs. TEMPERATURE
MAX2452-05
SIDEBAND REJECTION vs. IF FREQUENCY
-32 SIDEBAND REJECTION (dBc) -34 -36 -38 -40 -42 -44 -46 -48 VII = 1.2Vp-p VQQ = 1.2Vp-p
MAX2452-06
74 72 70 IF OUTPUT (mVp-p) 68 66 64 62 60 58 56 54 2.7 2.8 2.9 3.0 VCC (V) 3.1 3.2 TA = +70C TA = +25C TA = 0C TA = -25C TA = +85C
70 VCC = 3V 68 IF OUTPUT (mVp-p)
-30
66
64
62
3.3
60 -30
-50 -10 10 30 50 70 90 35 40 45 50 55 60 65 70 75 80 TEMPERATURE (C) IF FREQUENCY (MHz)
SIDEBAND REJECTION vs. TEMPERATURE
MAX2452-07
LO LEAKAGE vs. IF FREQUENCY
MAX2452-08
PRE_OUT WAVEFORM
RL = 10k CL < 6pF
MAX2452-09
-30 -32 SIDEBAND REJECTION (dBc) -34 -36 -38 -40 -42 -44 -46 -48 -50 -30 -10 10 30 50 70 VII = 1.2Vp-p VQQ = 1.2Vp-p
-30 -32 LO LEAKAGE (dBc) -34 -36 -38 -40 -42 -44
100mV/ div
90
35
40 45 50
55
60
65
70 75
80
TEMPERATURE (C)
IF FREQUENCY (MHz)
20ns/div
_______________________________________________________________________________________
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3V, Ultra-Low-Power Quadrature Modulator MAX2452
____________________________Typical Operating Characteristics (continued)
(VCC = LO_VCC = 3.0V, fOSC = 140MHz, ENABLE = 2.6V, fII = fQQ = 600kHz, RL (IF, IF) = 200k differential, CL (IF, IF) < 5pF differential, TA = +25C, unless otherwise noted.)
MODULATOR OUTPUT SPECTRUM
MAX2453-10
0 -10 -20 (dBc) -30 -40 -50 -60 69.0 69.4 70.0 (MHz) 70.6 VII = 1.2Vp-p VQQ = 1.2Vp-p
71.0
_____________________Pin Description
PIN 1 2, 15 3 4 5 6 7 8 9 10 11 12 13 14 16 4 NAME IF GND I I Q Q ENABLE TANK TANK LO_GND LO_VCC PRE_OUT N.C. VCC IF FUNCTION IF Inverting Output Ground Inphase Input Inphase Inverting Input Quadrature Input Quadrature Inverting Input Enable Control, active high Local-Oscillator Resonant Tank Input Local-Oscillator Resonant Tank Inverting Input Local-Oscillator Ground Local-Oscillator Supply Local-Oscillator Divide-by-8 Prescaled Output No Connect, no internal connection to this pin Modulator Supply IF Output
_______________________________________________________________________________________
3V, Ultra-Low-Power Quadrature Modulator
_______________Detailed Description
The MAX2452 quadrature modulator integrates several important RF functions on a single chip. It includes differential buffers for the baseband inputs, two doublebalanced mixers, a local oscillator, a quadrature phase generator, and a divide-by-8 prescaler. The prescaler simplifies the implementation of a phase-locked loop. Each of the functional blocks (shown in the Functional Diagram) is described in detail in the following sections.
L0_VCC
MAX2452
RL 5k Q3 TANK TANK
RL 5k Q4
Local Oscillator
The local-oscillator section is formed by an emitter-coupled differential pair. Figure 1 shows the equivalent local-oscillator circuit schematic. An external LC resonant tank determines the oscillation frequency, and the Q of this resonant tank determines the phase noise of the oscillator. The oscillation frequency is twice the IF frequency, so that the quadrature phase generator can use two latches to generate precise quadrature signals.
Q1
Q2
TO DIVIDE-BY-2
Quadrature Phase Generator
The quadrature phase generator uses two latches to divide the local-oscillator frequency by two, and generates two precise quadrature signals. Internal limiting amplifiers shape the signals to approximate square waves to drive the Gilbert-cell mixers in the modulator. The inphase signal (at half the local-oscillator frequency) is further divided by four for an external phaselocked loop.
Figure 1. Local-Oscillator Equivalent Circuit
Prescaler
The prescaler output, PRE_OUT, is buffered and swings typically 0.35Vp-p with a 10k and 6pF load. It can be AC-coupled to the input of a frequency synthesizer.
Master Bias
During normal operation, ENABLE should remain above VCC - 0.4V. Pulling the ENABLE input low shuts off the master bias and reduces the circuit current to 2A. The master bias section includes a bandgap reference generator and a PTAT (Proportional To Absolute Temperature) current generator.
Modulator
The modulator accepts up to 1.35Vp-p I and Q differential baseband signals up to 15MHz, and upconverts them to higher-frequency IF signals. Since these inputs are biased internally at around 1.5V, you can improve carrier suppression by externally capacitively coupling the signals into these high-impedance ports (the differential input impedance is approximately 44k). The self-bias design is for very low on-chip offset, resulting in excellent carrier suppression. The IF output is designed to drive a high impedance (>20k), such as an IF buffer or an upconverter mixer.
_______________________________________________________________________________________
5
3V, Ultra-Low-Power Quadrature Modulator MAX2452
I
DSP PROCESSING
0 90 Q
UP CONVERTER /8
MAX2452
Figure 2. Typical Application Block Diagram
Applications Information
The MAX2452 quadrature modulator is designed to upconvert I and Q baseband signals to IF frequencies up to 80MHz. Figure 2 shows a typical application block diagram, in which the MAX2452 is used for the first upconversion in a dual-conversion transmitter. Figure 3 shows an implementation of a resonant tank circuit. The inductor, two capacitors, and a dual varactor form the resonant circuit of the oscillator. The frequency range of the oscillator shown in Figure 3 is 130MHz to 160MHz. The inductor is directly connected across the local oscillator's tank ports so that it will not lock up the oscillator in a stable state during start-up. The two 33pF capacitors increase the Q of the resonant circuit and reduce the VCO gain. They can be changed to meet individual applications requirements. The oscillation frequency can be determined using the following formula: fo = where CEQ = and LEQ = L + LSTRAY CSTRAY, LSTRAY: parasitic capacitance and inductance.
6
To alter the oscillation frequency range, change the inductance, the capacitance, or both. Make sure the Q of the resonant tank does not drop below 35. CEQ LEQ
Q = REQ
where REQ = 10k (see Figure 1). The oscillation frequency can be changed by altering the control voltage, VCTRL.
C1 = 33pF TANK
47k
1 2 LEQ CEQ
L = 100nH
1/2KV1410 0.1F 10k VCTRL 1/2KV1410
1 1 1 2 + + C1 C2 C VAR
+ CSTRAY
TANK
C2 = 33pF
47k
Figure 3. Typical Resonant Tank Circuit
_______________________________________________________________________________________
3V, Ultra-Low-Power Quadrature Modulator
________________________________________________________Package Information
DIM INCHES MAX MIN 0.069 0.053 0.010 0.004 0.019 0.014 0.010 0.007 0.157 0.150 0.050 0.244 0.228 0.050 0.016 MILLIMETERS MIN MAX 1.35 1.75 0.10 0.25 0.35 0.49 0.19 0.25 3.80 4.00 1.27 5.80 6.20 0.40 1.27
MAX2452
D A e B
0.101mm 0.004in.
0-8
A1
C
L
A A1 B C E e H L
E
H
Narrow SO SMALL-OUTLINE PACKAGE (0.150 in.)
DIM PINS D D D 8 14 16
INCHES MILLIMETERS MIN MAX MIN MAX 0.189 0.197 4.80 5.00 0.337 0.344 8.55 8.75 0.386 0.394 9.80 10.00
21-0041A
_______________________________________________________________________________________
7
3V, Ultra-Low-Power Quadrature Modulator MAX2452
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) 1995 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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