19-0425; Rev 1; 9/95 KIT ATION EVALU BLE A IL A V A 3V, Ultra-Low-Power Quadrature Modulator ________________________Applications Digital Cordless Phones GSM and North American Cellular Phones ____________________________Features ♦ IF Output Frequency up to 80MHz ♦ Input Bandwidth up to 15MHz ♦ On-Chip Oscillator with External Tuning Circuit ♦ On-Chip Divide-by-8 Prescaler ♦ Integrated Quadrature Phase Shifters ♦ Self-Biased Differential Baseband Inputs ♦ CMOS-Compatible Enable ♦ 4.1mA Operating Supply Current 2µA Shutdown Supply Current ______________Ordering Information PART MAX2452ISE* TEMP. RANGE -20°C to +85°C PIN-PACKAGE 16 Narrow SO * An alternate marking, MAX2452CSE, has been identically tested. Wireless LANs Digital Communications Two-Way Pagers ________________Functional Diagram __________________Pin Configuration LO_VCC TOP VIEW TANK TANK LO_GND IF 1 11 8 9 10 LOCAL OSCILLATOR PRESCALER 0° ÷4 12 PRE_OUT QUADRATURE PHASE GENERATOR 90° ÷2 16 IF GND 2 15 GND I 3 I 3 14 VCC I 4 I 4 ÷2 MAX2452 13 N.C. Q 5 12 PRE_OUT Q 6 11 LO_VCC ENABLE 7 10 LO_GND TANK 8 9 SO TANK 16 MODULATOR Q Q VCC 5 Σ 1 IF IF 6 14 MASTER BIAS BANDGAP BIAS 2, 15 GND MAX2452 7 ENABLE ________________________________________________________________ Maxim Integrated Products Call toll free 1-800-998-8800 for free samples or literature. 1 MAX2452 _______________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 2µA. 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 3V, Ultra-Low-Power Quadrature Modulator 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 = +70°C) SO (derate 8.33mW/°C above +70°C) ..........................667mW Operating Temperature Range ...........................-20°C to +85°C Storage Temperature Range ............................–65°C to +165°C Lead Temperature (soldering, 10sec) .............................+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. DC ELECTRICAL CHARACTERISTICS (VCC = LO_VCC = 2.7V to 3.3V, TA = -20°C to +85°C, unless otherwise noted.) PARAMETER Supply Voltage Range Supply Current SYMBOL CONDITIONS VCC, LO_VCC MIN TYP MAX 2.7 ICC ON Enable = VCC - 0.4V Shutdown Supply Current ICC OFF Enable = 0.4V Enable/Disable Time tON/OFF ENABLE Bias Current IEN UNITS 3.3 V 4.1 7 mA 2 20 µA 10 µA 0.4 V 10 Enable = VCC - 0.4V µs 1 ENABLE Low Voltage VENL ENABLE High Voltage VENH VCC - 0.4 IF Voltage Level VIF VCC - 1.7 VCC - 1.35 V IF Voltage Level V IF VCC - 1.7 VCC - 1.35 V V TANK Voltage Level VTANK LO_VCC - 1.1 LO_VCC - 0.8 V TANK Voltage Level V TANK LO_VCC - 1.1 LO_VCC - 0.8 V I, I, Q, Q Voltage Level Differential Input Impedance V I , V I , VQ , V Q 1.25 1.5 ZII, ZQQ 35 44 1.75 V kΩ AC ELECTRICAL CHARACTERISTICS (VCC = LO_VCC = 3.0V, fOSC = 140MHz, ENABLE = 2.6V, fII = fQQ = 600kHz, TA = -20°C to +85°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS Differential Input Voltage VIIp-p, VQQp-p (Note 1) I and Q Signal Bandwidth BWIQ (Note 1) IF Differential Output Voltage VIFIFp-p MIN VII = VQQ = 1.2Vp-p, RL = 200kΩ differential, CL < 5pF differential I/Q Phase Match Sideband Rejection Oscillator Frequency Range PRE_OUT Output Voltage PRE_OUT Slew Rate VII = VQQ = 1.2Vp-p fOSC VPRE_OUT SRPRE_OUT (Notes 1, 2) RL = 10kΩ, CL < 6pF RL = 10kΩ, CL < 6pF, rising edge, TA = +25°C MAX UNITS 1.2 1.35 Vp-p 15 MHz 65 I/Q Amplitude Match LO Leakage at Output TYP 70 mVp-p <±0.3 dB <±3 degrees 42 dB -36 dBc 140 160 MHz 0.35 Vp-p 60 V/µs 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 MAX2452 __________________________________________Typical Operating Characteristics (VCC = LO_VCC = 3.0V, fOSC = 140MHz, ENABLE = 2.6V, fII = fQQ = 600kHz, RL (IF, IF) = 200kΩ differential, CL (IF, IF) < 5pF differential, TA = +25°C, unless otherwise noted.) VCC = 3V VCC = 2.7V 10 30 50 70 8 6 VCC = 2.7V Vp-p = 2 2 x 10 (V) -54 -10 10 30 50 70 90 -26 -22 -18 -14 -10 IF OUTPUT vs. SUPPLY VOLTAGE IF OUTPUT vs. TEMPERATURE SIDEBAND REJECTION vs. IF FREQUENCY IF OUTPUT (mVp-p) TA = +85°C TA = +70°C TA = +25°C TA = 0°C 62 60 TA = -25°C 66 64 62 56 VII = 1.2Vp-p VQQ = 1.2Vp-p -32 -6 MAX2452-06 -30 SIDEBAND REJECTION (dBc) VCC = 3V MAX2452-05 MAX2452-04 70 58 -34 -36 -38 -40 -42 -44 -46 -48 54 2.9 3.0 3.1 3.2 -50 -10 10 30 50 70 35 90 40 45 50 55 60 65 70 75 80 VCC (V) TEMPERATURE (°C) IF FREQUENCY (MHz) SIDEBAND REJECTION vs. TEMPERATURE LO LEAKAGE vs. IF FREQUENCY PRE_OUT WAVEFORM -30 MAX2452-07 -30 -32 3.3 VII = 1.2Vp-p VQQ = 1.2Vp-p -32 MAX2452-09 2.8 60 -30 MAX2452-08 2.7 RL = 10kΩ CL < 6pF -34 LO LEAKAGE (dBc) SIDEBAND REJECTION (dBc) dBVRMS 20 -50 68 64 -46 4 BASEBAND INPUT (dBVRMS) 70 66 -42 TEMPERATURE (°C) 72 68 -38 TEMPERATURE (°C) 74 IF OUTPUT (mVp-p) VCC = 3V 10 0 -30 90 -34 VCC = 3.3V 12 2 -10 -30 MAX2452-03 14 OUTPUT (dBVRMS) VCC = 3.3V IF OUTPUT vs. BASEBAND INPUT MAX2452-02 16 MAX2452-01 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 SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE SUPPLY CURRENT (µA) SUPPLY CURRENT (mA) SUPPLY CURRENT vs. TEMPERATURE -36 -38 -40 -42 -44 -34 -36 100mV/ div -38 -40 -46 -42 -48 -50 -30 -44 -10 10 30 50 TEMPERATURE (°C) 70 90 35 40 45 50 55 60 65 IF FREQUENCY (MHz) 70 75 80 20ns/div _______________________________________________________________________________________ 3 ____________________________Typical Operating Characteristics (continued) (VCC = LO_VCC = 3.0V, fOSC = 140MHz, ENABLE = 2.6V, fII = fQQ = 600kHz, RL (IF, IF) = 200kΩ differential, CL (IF, IF) < 5pF differential, TA = +25°C, unless otherwise noted.) MODULATOR OUTPUT SPECTRUM -10 MAX2453-10 0 VII = 1.2Vp-p VQQ = 1.2Vp-p -20 (dBc) MAX2452 3V, Ultra-Low-Power Quadrature Modulator -30 -40 -50 -60 69.0 69.4 70.0 70.6 71.0 (MHz) _____________________Pin Description PIN 4 NAME FUNCTION 1 IF 2, 15 GND IF Inverting Output 3 I Inphase Input 4 I Inphase Inverting Input 5 Q Quadrature Input 6 Q Quadrature Inverting Input 7 ENABLE Enable Control, active high 8 TANK Local-Oscillator Resonant Tank Input 9 TANK Local-Oscillator Resonant Tank Inverting Input 10 LO_GND Local-Oscillator Ground 11 LO_VCC Local-Oscillator Supply 12 PRE_OUT 13 N.C. No Connect, no internal connection to this pin 14 VCC Modulator Supply 16 IF Ground Local-Oscillator Divide-by-8 Prescaled Output IF Output _______________________________________________________________________________________ 3V, Ultra-Low-Power Quadrature Modulator Local Oscillator MAX2452 _______________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 RL 5k RL 5k Q3 TANK Q1 Q4 TANK Q2 TO DIVIDE-BY-2 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. 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. 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 44kΩ). 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 (>20kΩ), such as an IF buffer or an upconverter mixer. Figure 1. Local-Oscillator Equivalent Circuit Prescaler The prescaler output, PRE_OUT, is buffered and swings typically 0.35Vp-p with a 10kΩ 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 2µA. The master bias section includes a bandgap reference generator and a PTAT (Proportional To Absolute Temperature) current generator. _______________________________________________________________________________________ 5 MAX2452 3V, Ultra-Low-Power Quadrature Modulator I DSP PROCESSING 0° 90° Σ 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 = 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. Q = REQ CEQ LEQ where REQ = 10kΩ (see Figure 1). The oscillation frequency can be changed by altering the control voltage, VCTRL. C1 = 33pF 47k TANK 1/2KV1410 1 0.1µF 2π LEQ CEQ 10k VCTRL L = 100nH where CEQ = 1 1 1 2 + + C1 C2 C VAR 1/2KV1410 + CSTRAY C2 = 33pF 47k TANK and LEQ = L + LSTRAY CSTRAY, LSTRAY: parasitic capacitance and inductance. 6 Figure 3. Typical Resonant Tank Circuit _______________________________________________________________________________________ 3V, Ultra-Low-Power Quadrature Modulator DIM D 0°-8° A 0.101mm 0.004in. e B A1 E C H L Narrow SO SMALL-OUTLINE PACKAGE (0.150 in.) A A1 B C E e H L 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 DIM PINS D D D 8 14 16 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 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 MAX2452 ________________________________________________________Package Information MAX2452 3V, Ultra-Low-Power Quadrature Modulator 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 © 1995 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.