19-0455; Rev 1; 9/98 KIT ATION EVALU E L B AVAILA 3V, Ultra-Low-Power Quadrature Modulator/Demodulator The MAX2450 combines a quadrature modulator and quadrature demodulator with a supporting oscillator and divide-by-8 prescaler on a monolithic IC. It operates from a single +3V supply and draws only 5.9mA. The demodulator accepts an amplified and filtered IF signal in the 35MHz to 80MHz range, and demodulates it into I and Q baseband signals with 51dB of voltage conversion gain. The IF input is terminated with a 400Ω thinfilm resistor for matching to an external IF filter. The baseband outputs are fully differential and have 1.2Vp-p signal swings. The modulator accepts differential I and Q baseband signals with amplitudes up to 1.35Vp-p and bandwidths to 15MHz, and produces a differential IF signal in the 35MHz to 80MHz range. Pulling the CMOS-compatible ENABLE pin low shuts down the MAX2450 and reduces the supply current to less than 1µA. To minimize spurious feedback, the MAX2450’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 modulator sideband rejection of 38dB. The MAX2450 comes in a QSOP package. ____________________________Features ♦ Combines Quadrature Modulator and Demodulator ♦ Integrated Quadrature Phase Shifters ♦ On-Chip Oscillator (Requires External Tuning Circuit) ♦ On-Chip Divide-by-8 Prescaler ♦ Modulator Input Bandwidth Up to 15MHz ♦ Demodulator Output Bandwidth Up to 9MHz ♦ 51dB Demodulator Voltage Conversion Gain ♦ CMOS-Compatible Enable ♦ 5.9mA Operating Supply Current 1µA Shutdown Supply Current Ordering Information PART TEMP. RANGE MAX2450CEP 0°C to +70°C PIN-PACKAGE 20 QSOP Applications Functional Diagram Digital Cordless Phones GSM and North American Cellular Phones Wireless LANs 17 Digital Communications 16 DEMODULATOR Two-Way Pagers IF_IN 20 15 400Ω 14 TOP VIEW 20 IF_IN IF_OUT 2 19 GND GND 3 18 VCC I_IN 4 17 I_OUT I_IN 5 MAX2450 16 I_OUT Q_IN 6 15 Q_OUT Q_IN 7 14 Q_OUT LO_VCC TANK TANK LO_GND I_IN I_IN ENABLE 13 LO_GND 8 PRE_OUT 9 12 TANK LO_VCC 10 11 TANK QSOP 10 ÷2 11 12 13 I_OUT BIAS Pin Configuration IF_OUT 1 I _OUT LOCAL OSCILLATOR 0° PRESCALER QUADRATURE PHASE GENERATOR ÷ 2 90° ÷4 9 Q_OUT Q_OUT PRE_OUT MAX2450 4 5 Σ MODULATOR 6 Q_IN 7 Q_IN 18 VCC 1 IF_OUT 2 IF_OUT MASTER BIAS BANDGAP 3, 19 GND BIAS 8 ENABLE ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX2450 General Description MAX2450 3V, Ultra-Low-Power Quadrature Modulator/Demodulator ABSOLUTE MAXIMUM RATINGS VCC, LO_VCC to GND............................................-0.3V to +4.5V ENABLE, TANK, TANK, I_IN, I_IN, Q_IN, Q_IN to GND ..................................................-0.3V to (VCC + 0.3V) IF_IN to GND .........................................................-0.3V to +1.5V Continuous Power Dissipation (TA = +70°C) QSOP (derate 9.1mW/°C above +70°C) ......................727mW Operating Temperature Range...............................0°C to +70°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 = TANK = 2.7V to 3.3V, ENABLE = VCC - 0.4, GND = LO_GND = 0V, I_IN = I_IN = Q_IN = Q_IN = IF_IN = TANK = OPEN, TA = 0°C to +70°C, unless otherwise noted.) PARAMETER Supply Voltage Range Supply Current Shutdown Supply Current Enable/Disable Time ENABLE Bias Current ENABLE High Voltage ENABLE Low Voltage SYMBOL VCC, LO_VCC ICC(ON) ICC(OFF) tON/OFF IEN VENH VENL I_IN, I_IN, Q_IN, Q_IN Self-Bias DC Voltage Level VI_IN/I_IN, VQ_IN/Q_IN 1.25 1.5 Modulator Differential Input Impedance ZI_IN/I_IN, ZQ_IN/Q_IN 35 44 320 VCC - 1.5 400 480 V Ω ±11 ±50 mV IF_OUT, IF_OUT DC Bias Voltage Demodulator IF Input Impedance CONDITIONS MIN 2.7 5.9 2 10 1 ENABLE = 0.4V ENABLE = VCC MAX 3.3 8.2 20 0.4 UNITS V mA µA µs µA V V 1.75 V 3 VCC - 0.4 VIF_OUT/IF_OUT ZIF_IN Demodulator I and Q Baseband DC Offset I_OUT, I_OUT, Q_OUT, Q_OUT DC Bias Voltage Level TYP VI_OUT/I_OUT, VQ_OUT/Q_OUT kΩ 1.2 V AC ELECTRICAL CHARACTERISTICS (MAX2450 EV kit, VCC = LO_VCC = ENABLE = 3.0V, fLO = 140MHz, fI_IN/I_IN = fQ_IN/Q_IN = 600kHz, VI_IN/I_IN = VQ_IN/Q_IN = 1.2Vp-p, fIF_IN = 70.1MHz, VIF_IN = 2.82mVp-p, TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DEMODULATOR I and Q Amplitude Balance < ±0.45 dB I and Q Phase Accuracy < ±1.3 degrees Voltage Conversion Gain 51 Allowable I and Q Voltage Swing Noise Figure I and Q IM3 Level I and Q IM5 Level I and Q Signal 3dB Bandwidth Oscillator Frequency Range (Note 1) NF PRE_OUT Slew Rate 2 Vp-p 18 dB IM3I/Q (Note 2) -44 dBc IM5I/Q (Note 2) -60 dBc 9 MHz BWDEMOD fLO LO Phase Noise PRE_OUT Output Voltage dB 1.35 VPRE_OUT SRPRE_OUT (Notes 1, 3) 70 160 MHz 10kHz offset -80 dBc/Hz RL = 10kΩ, CL < 6pF 0.35 Vp-p 60 V/µs RL = 10kΩ, CL < 6pF, rising edge _______________________________________________________________________________________ 3V, Ultra-Low-Power Quadrature Modulator/Demodulator (MAX2450 EV kit, VCC = LO_VCC = ENABLE = 3.0V, fLO = 140MHz, fI_IN/I_IN = fQ_IN/Q_IN = 600kHz, VI_IN/I_IN = VQ_IN/Q_IN = 1.2Vp-p, fIF_IN = 70.1MHz, VIF_IN = 2.82mVp-p, TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 1.35 Vp-p 1.75 15 V MHz VI_IN/I_IN, = VQ_IN/Q_IN = 1.2Vp-p, RL = 200kΩ differential, CL < 5pF differential 65 mVp-p MODULATOR VI_IN/I_IN, VQ_IN/Q_IN Allowable Differential Input Voltage Input Common-Mode Voltage Range I and Q Signal 3dB Bandwidth IF Differential Output Voltage (Note 1) 1.25 BWMOD VIF_OUT/IF_OUT IF Output IM3 Level IM3IF VI_IN/I_IN = 1.35Vp-p composite (Note 4) -60 dBc IF Output IM5 Level IM5IF VI_IN/I_IN = 1.35Vp-p composite (Note 4) -60 dBc Sideband Rejection 38 dBc Carrier Suppression at Modulator Output -36 dBc Guaranteed by design, not tested. fIF_IN = 2 tones at 70.10MHz and 70.11MHz. VIF_IN = 1.41mVp-p per tone. The frequency range can be extended in either direction, but has not been characterized. At higher frequencies, the modulator IF output amplitude may decrease and distortions may increase. Note 4: Q_IN/Q_IN ports are terminated. fI_IN/I_IN = 2 tones at 550kHz and 600kHz. Note 1: Note 2: Note 3: __________________________________________Typical Operating Characteristics (MAX2450 EV kit, VCC = LO_VCC = ENABLE = 3.0V, fLO = 140MHz, fI_IN/I_IN = fQ_IN/Q_IN = 600kHz, VI_IN/I_IN = VQ_IN/Q_IN = 1.2Vp-p, fIF_IN = 70.1MHz, VIF_IN = 2.82mVp-p, TA = +25°C, unless otherwise noted.) SUPPLY CURRENT vs. TEMPERATURE SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE 6.0 10 VCC = 2.7V 5.8 5.6 5.4 8 6 VCC = 3.0V 4 2 MAX2450-03 -34 VCC = 3.3V OUTPUT (dBVRMS) VCC = 3.0V 6.2 -30 MAX2450-02 VCC = 3.3V 6.6 6.4 12 SUPPLY CURRENT (µA) SUPPLY CURRENT (mA) 6.8 MAX2450-01 7.0 MODULATOR IF OUTPUT vs. BASEBAND INPUT -38 -42 -46 dBVRMS 20 -50 VCC = 2.7V Vp-p = 2 2 x 10 5.2 5.0 -54 0 0 10 20 30 40 50 TEMPERATURE (°C) 60 70 80 (V) 0 10 20 30 40 50 60 TEMPERATURE (°C) 70 80 -26 -22 -18 -14 -10 -6 BASEBAND INPUT (dBVRMS) _______________________________________________________________________________________ 3 MAX2450 AC ELECTRICAL CHARACTERISTICS (continued) ____________________________Typical Operating Characteristics (continued) (MAX2450 EV kit, VCC = LO_VCC = ENABLE = 3.0V, fLO = 140MHz, fI_IN/I_IN = fQ_IN/Q_IN = 600kHz, VI_IN/I_IN = VQ_IN/Q_IN = 1.2Vp-p, fIF_IN = 70.1MHz, VIF_IN = 2.82mVp-p, TA = +25°C, unless otherwise noted.) MODULATOR IF OUTPUT vs.TEMPERATURE 68 IF OUTPUT (mVp-p) IF OUTPUT (mVp-p) SIDEBAND REJECTION (dBc) VCC = 3V 68 TA = +70°C 66 TA = +25°C 64 TA = 0°C 62 -30 MAX2450-05 70 MAX2450-04 70 MODULATOR SIDEBAND REJECTION vs. IF FREQUENCY 66 64 62 MAX2450-06 MODULATOR IF OUTPUT vs. SUPPLY VOLTAGE VI_IN/I_IN = 1.2Vp-p VQ_IN/Q_IN = 1.2Vp-p -32 -34 -36 -38 -40 -42 60 60 2.8 2.9 3.0 3.1 3.2 3.3 -44 0 20 40 60 80 35 40 45 50 55 70 IF FREQUENCY (MHz) MODULATOR SIDEBAND REJECTION vs. TEMPERATURE CARRIER SUPPRESSION vs. IF FREQUENCY PRE_OUT WAVEFORM -30 CARRIER SUPPRESSION (dBc) -38 -40 -42 VI_IN/I_IN = 1.2Vp-p VQ_IN/Q_IN = 1.2Vp-p -32 -34 100mV/ div -36 -38 -40 RL = 10kΩ CL < 6pF -42 -44 -44 20 40 60 80 35 40 45 TEMPERATURE (°C) 50 55 60 65 70 75 80 20ns/div IF FREQUENCY (MHz) MODULATOR OUTPUT SPECTRUM MAX2450-10 0 VI_IN/I_IN = 1.2Vp-p VQ_IN/Q_IN = 1.2Vp-p -10 (dBc) -20 -30 -40 -50 -60 69.0 69.4 70.0 75 80 MAX2450-09 MAX2450-07 VI_IN/I_IN = 1.2Vp-p VQ_IN/Q_IN = 1.2Vp-p 0 65 TEMPERATURE (°C) -36 70.6 71.0 (MHz) 4 60 VCC (V) MAX2450-08 2.7 SIDEBAND REJECTION (dBc) MAX2450 3V, Ultra-Low-Power Quadrature Modulator/Demodulator _______________________________________________________________________________________ 3V, Ultra-Low-Power Quadrature Modulator/Demodulator (MAX2450 EV kit, VCC = LO_VCC = ENABLE = 3.0V, fLO = 140MHz, fI_IN/I_IN = fQ_IN/Q_IN = 600kHz, VI_IN/I_IN = VQ_IN/Q_IN = 1.2Vp-p, fIF_IN = 70.1MHz, VIF_IN = 2.82mVp-p, TA = +25°C, unless otherwise noted.) 51.0 TA = +25°C 51 50 49 50.0 49.5 GAIN (dBV) 51.2 GAIN (dBV) 51.0 TA = +50°C 50.8 43 TA = +70°C 48.0 50.6 2.8 2.9 3.0 3.1 3.2 3.3 3.4 42 35 40 45 50 55 60 65 70 75 80 10k 100k IF FREQUENCY (MHz) VCC (V) -40 IM3 INTERMODULATION (dBc) 1.4 PHASE MATCH 1.2 10M 100M DEMODULATOR INTERMOD POWER vs. TEMPERATURE MAX2450-15 1.6 1M BASEBAND FREQUENCY (Hz) DEMODULATOR I/Q PHASE AND AMPLITUDE MISMATCH vs. TEMPERATURE MATCHING (DEGREES OR dBV) 46 44 48.5 2.7 47 45 49.0 2.6 48 1.0 0.8 MAX2450-16 50.5 DEMODULATOR VOLTAGE CONVERSION GAIN vs. BASEBAND FREQUENCY MAX2450-12 TA = 0°C GAIN (dBV) 51.4 MAX2450-11 51.5 DEMODULATOR VOLTAGE CONVERSION GAIN vs. IF FREQUENCY MAX2450-13 DEMODULATOR VOLTAGE CONVERSION GAIN vs. TEMPERATURE AND SUPPLY -45 -50 fOSC = 140MHz fIF1 = 70.1MHz fIF2 = 70.11MHz VIF_IN = 2.82mVp-p -55 -60 0.6 IM5 AMPLITUDE MATCH -65 0.4 0 10 20 30 40 50 TEMPERATURE (°C) 60 70 0 10 20 30 40 50 60 70 TEMPERATURE (°C) _______________________________________________________________________________________ 5 MAX2450 ____________________________Typical Operating Characteristics (continued) MAX2450 3V, Ultra-Low-Power Quadrature Modulator/Demodulator ______________________________________________________________Pin Description PIN NAME 1 IF_OUT Modulator IF Output FUNCTION Modulator IF Inverting Output 2 IF_OUT 3, 19 GND Ground 4 I_IN Baseband Inphase Input 5 I_IN Baseband Inphase Inverting Input 6 Q_IN Baseband Quadrature Input 7 Q_IN Baseband Quadrature Inverting Input 8 ENABLE 9 PRE_OUT Enable Control, active high 10 LO_VCC 11 TANK Local-Oscillator Resonant Tank Input (Figure 4) 12 TANK Local-Oscillator Resonant Tank Inverting Input (Figure 4) 13 LO_GND 14 Q_OUT Demodulator Quadrature Inverting Output 15 Q_OUT Demodulator Quadrature Output 16 I_OUT Demodulator Inphase Inverting Output 17 I_OUT Demodulator Inphase Output Local-Oscillator, Divide-by-8, Prescaled Output Local-Oscillator Supply. Bypass separately from VCC. Local-Oscillator Ground 18 VCC Modulator and Demodulator Supply 20 IF_IN Demodulator IF Input 2 2 A/D CONVERSION A/D CONVERSION DSP 0° R 90° T UP/DOWNCONVERTER ÷8 2 Σ 2 MAX2450 D/A CONVERSION D/A CONVERSION Figure 1. Typical Application Block Diagram 6 _______________________________________________________________________________________ 3V, Ultra-Low-Power Quadrature Modulator/Demodulator MAX2450 LO_VCC TANK Q1 70 Q4 TANK Q2 TO QUADRATURE GENERATOR AND PRESCALER OUTPUT LEVEL (mVp-p) Q3 MAX2450-fig03 75 RL 5k RL 5k 65 60 55 50 45 40 35 200 1k 10k 100k LOAD RESISTANCE (Ω) Figure 2. Local-Oscillator Equivalent Circuit Figure 3. Modulator Output Level vs. Load Resistance _______________Detailed Description and should provide 200mVp-p levels. A choke (typically 2.2µH) is required between TANK and TANK. Differential input impedance at TANK/TANK is 10kΩ. For single-ended drive, connect an AC bypass capacitor (1000pF) from TANK to GND, and AC couple TANK to the source. The following sections describe each of the functional blocks shown in the Functional Diagram. They also refer to the Typical Application Block Diagram (Figure 1). Demodulator The demodulator contains a single-ended-to-differential converter, two Gilbert-cell multipliers, and two fixed gain stages. The IF signal should be AC coupled into IF_IN. Internally, IF_IN is terminated with a 400Ω resistor to GND and provides a gain of 14dB. This amplified IF signal is fed into the I and Q mixers for demodulation. The multipliers mix the IF signal with the quadrature LO signals, resulting in baseband I and Q signals. The conversion gain of the multipliers is 15dB. These signals are further amplified by 21dB by the baseband amplifiers. The baseband I and Q amplifier chains are DC coupled. Local Oscillator The local-oscillator section is formed by an emitter-coupled differential pair. Figure 2 shows the equivalent local-oscillator circuit schematic. An external LC resonant tank determines the oscillation frequency, and the Q of this resonant tank affects the oscillator phase noise. The oscillation frequency is twice the IF frequency, so that the quadrature phase generator can use two latches to generate precise quadrature signals. The oscillator may be overdriven by an external source. The source should be AC coupled into TANK/TANK, 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. The inphase signal (at half the local-oscillator frequency) is further divided by four for the prescaler output. 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. Modulator The modulator accepts I and Q differential baseband signals up to 1.35Vp-p with frequencies up to 15MHz, and upconverts them to the IF frequency. Since these inputs are biased internally at around 1.5V, I and Q signals should be capacitively coupled into these highimpedance ports (the differential input impedance is approximately 44kΩ). The self-bias design yields very low on-chip offset, resulting in excellent carrier sup- _______________________________________________________________________________________ 7 MAX2450 3V, Ultra-Low-Power Quadrature Modulator/Demodulator pression. Alternatively, a differential DAC may be connected without AC coupling, as long as a commonmode voltage range of 1.25V to 1.75V is maintained. For single-ended drive, connect I_IN and Q_IN via ACcoupling capacitors (0.1µF) to GND. The IF output is designed to drive a high impedance (> 20kΩ), such as an IF buffer or an upconverter mixer. IF_OUT/IF_OUT must be AC coupled to the load. Impedances as low as 200Ω can be driven with a decrease in output amplitude (Figure 3). To drive a single-ended load, AC couple and terminate IF_OUT with a resistive load equal to the load at IF_OUT. To alter the oscillation frequency range, change the inductance, the capacitance, or both. For best phasenoise performance keep the Q of the resonant tank as high as possible: Q = REQ C EQ LEQ where REQ ≈ 10kΩ (Figure 2). The oscillation frequency can be changed by altering the control voltage, VCTRL. 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 less than 2µA. The master bias section includes a bandgap reference generator and a PTAT (Proportional To Absolute Temperature) current generator. TANK C1 = 33pF 47k 1/2 KV1410 10k L = 100nH VCTRL __________Applications Information Figure 4 shows the implementation of a resonant tank circuit. The inductor, two capacitors, and a dual varactor form the oscillator’s resonant circuit. In Figure 4, the oscillator frequency ranges from 130MHz to 160MHz. To ensure reliable start-up, the inductor is directly connected across the local oscillator’s tank ports. The two 33pF capacitors affect the Q of the resonant circuit. Other values may be chosen to meet individual application requirements. Use the following formula to determine the oscillation frequency: fo = 0.1µF 1/2 KV1410 47k TANK C2 = 33pF Figure 4. Typical Resonant Tank Circuit 1 2π LEQCEQ where CEQ = 1 + CSTRAY 1 1 2 + + C1 C2 C VAR and LEQ = L + LSTRAY where CSTRAY = parasitic capacitance and LSTRAY = parasitic inductance. 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 © 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.