19-0493; Rev 0; 12/95 IT K ATION EVALU BLE AVAILA 3V, Ultra-Low-Power Quadrature Demodulator ________________________Applications Digital Cordless Phones ____________________________Features ♦ Integrated Quadrature Phase Shifters ♦ On-Chip Oscillator (Requires External Tuning Circuit) ♦ 51dB Voltage Conversion Gain ♦ On-Chip Divide-by-8 Prescaler ♦ Baseband Output Bandwidth Up to 9MHz ♦ CMOS-Compatible Enable ♦ 5.5mA Operating Supply Current 2µA Shutdown Supply Current ______________Ordering Information PART GSM and North American Cellular Phones TEMP. RANGE MAX2451CSE 0°C to +70°C PIN-PACKAGE 16 Narrow SO Wireless LANs Digital Communications Pagers ________________Functional Diagram 14 13 __________________Pin Configuration DEMODULATOR IF 1 400Ω 11 IF 1 16 GND GND 2 15 VCC GND 3 N.C. 4 MAX2451 LO_VCC 14 I TANK 13 I TANK ENABLE 5 12 Q LO_GND PRE_OUT 6 11 Q VCC LO_VCC 7 10 LO_GND 9 TANK 8 SO 7 ÷2 8 9 10 I BIAS 12 TOP VIEW I LOCAL OSCILLATOR 0° PRESCALER QUADRATURE PHASE GENERATOR ÷ 2 90° ÷4 6 Q Q PRE_OUT MAX2451 15 MASTER BIAS BANDGAP BIAS TANK 2, 3, 16 GND 5 ENABLE ________________________________________________________________ Maxim Integrated Products Call toll free 1-800-998-8800, or visit our WWW site at http://www.maxim-ic.com for free samples or the latest literature. 1 MAX2451 _______________General Description The monolithic MAX2451 is a quadrature demodulator with a supporting oscillator and divide-by-8 prescaler. It operates from a single +3V supply and draws only 5.5mA. 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 thin-film resistor for matching to an external IF filter. The baseband outputs are fully differential and have 1.2Vp-p signal swings. Pulling the CMOS-compatible ENABLE pin low shuts down the MAX2451 and reduces the supply current to less than 2µA, typical. To minimize spurious feedback, the MAX2451’s internal oscillator is set at twice the IF frequency via external tuning components. The MAX2451 comes in a 16-pin narrow SO package. MAX2451 3V, Ultra-Low-Power Quadrature Demodulator ABSOLUTE MAXIMUM RATINGS Continuous Power Dissipation (TA = +70°C) Narrow SO (derate 8.70mW/°C above +70°C) .............696mW Operating Temperature Range...............................0°C to +70°C Storage Temperature Range .............................-65°C to +165°C Lead Temperature (soldering, 10sec) .............................+300°C VCC, LO_VCC to GND............................................-0.3V to +4.5V ENABLE, TANK, TANK, I, I, Q, Q to GND.............................................-0.3V to (VCC + 0.3V) IF to GND...............................................................-0.3V to +1.5V 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 - 0.4V, GND = LO_GND = 0V, I = I = Q = Q = IF = TANK = OPEN, TA = 0°C to +70°C, unless otherwise noted.) PARAMETER SYMBOL Supply Voltage Range VCC, LO_VCC CONDITIONS MIN TYP MAX UNITS 3.3 V 5.5 7.4 mA 2 20 µA 3 µA 2.7 Supply Current ICC(ON) Shutdown Supply Current ICC(OFF) Enable/Disable Time tON/OFF 10 ENABLE Bias Current IEN 1 ENABLE High Voltage VENH ENABLE Low Voltage VENL IF Input Impedance I, I, Q, Q Voltage Level Enable = 0.4V µs VCC - 0.4 ZIN 320 VI/I, VQ/Q V 400 0.4 V 480 Ω 1.2 Baseband I and Q DC Offset ±11 V ±50 mV AC ELECTRICAL CHARACTERISTICS VCC = LO_VCC = ENABLE = 3.0V, fLO = 140MHz, fIF = 70.1MHz, VIF = 2.82mVp-p, TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Baseband I and Q Amplitude Balance < ±0.45 dB Baseband I and Q Phase Accuracy < ±1.3 degrees 51 dB Voltage Conversion Gain Noise Figure NF Allowable I and Q Voltage Swing 18 (Note 1) dB 1.35 Vp-p I and Q IM3 Level IM3I/Q (Note 2) -44 I and Q IM5 Level IM5I/Q (Note 2) -60 dBc I and Q Signal 3dB Bandwidth BW3dB 9 MHz Oscillator Frequency Range PRE_OUT Output Voltage PRE_OUT Slew Rate Oscillator Phase Noise Note 1: Note 2: Note 3: 2 fLO VPRE_OUT SRPRE_OUT (Notes 1, 3) RL = 10kΩ, CL < 6pF 70 dBc 160 0.35 MHz Vp-p RL = 10kΩ, CL < 6pF, rising edge 60 V/µs Offset = 10kHz -80 dBc/Hz Guaranteed by design, not tested. fIF = 2 tones at 70.10MHz and 70.11MHz, VIF = 1.41mVp-p per tone. Oscillator frequencies up to 1GHz (500MHz IF) by externally overdriving (see Applications Information). _______________________________________________________________________________________ 3V, Ultra-Low-Power Quadrature Demodulator 6.0 5.8 5.6 5.4 51.5 MAX2451-02 6 SHUTDOWN ICC (µA) 6.2 VCC = 3.0V TA = 0°C 51.0 5 TA = +25°C 50.5 GAIN (dBV) VCC = 3.0V 4 3 50.0 49.5 TA = +50°C 2 49.0 1 48.5 TA = +70°C 0 10 20 30 40 50 60 70 30 40 50 60 VOLTAGE CONVERSION GAIN vs. IF FREQUENCY PHASE AND AMPLITUDE MATCHING vs. TEMPERATURE 49 48 47 46 fBASEBAND = 100kHz VLO_INJECT = 40mVRMS = 113mVp-p into 5OΩ VIF_IN = 2.82mVP-P 42 70 2.6 1.6 PHASE MATCH 1.0 0.8 200 300 400 500 3.2 3.3 3.4 -40 IM3 -45 -50 fLO = 140MHz fIF1 = 70.10MHz fIF2 = 70.11MHz VIF_IN = 1.41mVp-p per tone -55 IM5 AMPLITUDE MATCH -65 0 20 10 IF FREQUENCY (MHz) 30 40 50 60 0 70 10 20 30 40 50 60 70 TEMPERATURE (°C) TEMPERATURE (°C) PRE_OUT WAVEFORM MAX2451-07 100 2.9 3.0 3.1 -60 0.6 0.4 0 2.8 INTERMODULATION POWER vs. TEMPERATURE 1.4 1.2 2.7 VCC (V) MAX2451-05 MAX2451-04 50 43 20 TEMPERATURE (°C) 51 44 10 TEMPERATURE (°C) 52 45 48.0 0 MATCHING (DEGREES OR dBV) 0 MAX2451-06 5.2 INTERMODULATION (dBc) ICC (mA) 7 MAX2451-01 6.4 GAIN (dBV) VOLTAGE CONVERSION GAIN vs. TEMPERATURE AND SUPPLY VOLTAGE SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE MAX2451-03 SUPPLY CURRENT vs. TEMPERATURE 100mV/div RL = 10kΩ CL < 6pF 20ns/div _______________________________________________________________________________________ 3 MAX2451 __________________________________________Typical Operating Characteristics (VCC = LO_VCC = ENABLE = 3.0V, fLO = 140MHz, fIF = 70.1MHz, VIF = 2.82mVp-p, TA = +25°C, unless otherwise noted.) MAX2451 3V, Ultra-Low-Power Quadrature Demodulator _____________________Pin Description PIN NAME 1 IF IF Input FUNCTION 2, 3, 16 GND Ground 4 N.C. No Connect. No internal connection to this pin. 5 ENABLE Enable Control, active high 6 PRE_OUT Local-Oscillator Divide-by-8 Prescaled Output 7 LO_VCC Local-Oscillator Supply. Bypass separately from VCC. 8 TANK Local-Oscillator Resonant Tank Input 9 TANK Local-Oscillator Resonant Tank Inverting Input 10 LO_GND 11 Q Baseband Quadrature Inverting Output 12 Q Baseband Quadrature Output 13 I Baseband Inphase Inverting Output 14 I Baseband Inphase Output 15 VCC DOWNCONVERTER 2 A/D 0˚ 90˚ Local-Oscillator Ground 2 POST PROCESSING A/D MAX2451 ÷8 Demodulator Supply Figure 1. Typical Application Block Diagram _______________Detailed Description The following sections describe each of the functional blocks shown in the Functional Diagram. 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. Internally, IF is terminated with a 400Ω resistor to GND. The IF input signal is AC coupled into the input amplifier, which has 14dB of gain. This amplified IF signal is fed into the I and Q channel 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 amplifier chains are DC coupled. 4 Local Oscillator The local-oscillator section is formed by an emitter-coupled differential pair. Figure 2 shows the local-oscillator equivalent 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, for easy generation of quadrature signals. The oscillator may be overdriven by an external source. The source should be AC coupled into TANK/TANK, 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 singleended drive, connect an AC bypass capacitor (1000pF) from TANK to GND, and AC couple TANK to the source. The oscillator can be overdriven at frequencies up to 1GHz (500MHz IF), but conversion gain and prescaler output levels will be somewhat reduced. _______________________________________________________________________________________ 3V, Ultra-Low-Power Quadrature Demodulator MAX2451 LO_VCC RL 5k RL 5k Q3 TANK C1 = 33pF TANK 47k Q4 TANK 1/2 KV1410 10k L = 100nH Q1 0.1µF VCTRL Q2 1/2 KV1410 TO QUADRATURE GENERATOR AND PRESCALER 47k TANK Figure 2. Local-Oscillator Equivalent Circuit C2 = 33pF Figure 3. Typical Resonant Tank Circuit 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. cation requirements. The oscillation frequency can be determined using the following formula: fo = Master Bias During normal operation, ENABLE should be above VCC - 0.4V. Pulling the ENABLE input low shuts off the master bias and reduces the circuit current to typically 2µA. The master bias section includes a bandgap reference generator and a PTAT (Proportional To Absolute Temperature) current generator. __________Applications Information Figure 3 shows the implementation of a resonant tank circuit. The inductor, two capacitors, and a dual varactor form the oscillator’s resonant circuit. In Figure 3, 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 appli- 2π LEQCEQ where CEQ = 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. 1 1 + C STRAY 1 1 2 + + C1 C2 C VAR and LEQ = L + LSTRAY where CSTRAY = parasitic capacitance and LSTRAY = parasitic inductance. 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. _______________________________________________________________________________________ 5 MAX2451 3V, Ultra-Low-Power Quadrature Demodulator ________________________________________________________Package Information DIM D 0°-8° A 0.101mm 0.004in. e B A1 E C L Narrow SO SMALL-OUTLINE PACKAGE (0.150 in.) H 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 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. 6 ___________________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.