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general description the max2420/max2421/max2422/MAX2460/max2463 are highly integrated front-end ics that provide the lowest cost solution for cordless phones and ism-band radios operating in the 900mhz band. all devices incorporate transmit and receive image-reject mixers to reduce filter cost. they operate with a +2.7v to +4.8v power supply, allowing direct connection to a three-cell battery stack. the receive path incorporates an adjustable-gain lna and an image-reject downconverter with 35db image suppression. these features yield excellent combined downconverter noise figure (4db) and high linearity with an input third-order intercept point (ip3) of up to +2dbm. the transmitter consists of a variable-gain if amplifier with more than 35db control range, an image-reject upconverter with 35db image rejection, and a power- amplifier (pa) predriver that produces up to +2dbm (in some applications serving as the final power stage). all devices include an on-chip local oscillator (lo), requiring only an external varactor-tuned lc tank for operation. the integrated divide-by-64/65 dual-modulus prescaler can also be set to a direct mode, in which it acts as an lo buffer amplifier. four separate power- down inputs can be used for system power manage- ment, including a 0.5? shutdown mode. these parts are compatible with commonly used modulation schemes such as fsk, bpsk, and qpsk, as well as fre- quency hopping and direct sequence spread-spectrum systems. all devices come in a 28-pin ssop package. for applications using direct vco or bpsk transmit mod- ulation, as well as receive image rejection, consult the max2424/max2426 data sheet. for receive-only devices, refer to the max2440/max2441/max2442 data sheet. ________________________applications cordless phones spread-spectrum communications wireless telemetry two-way paging wireless networks features receive/transmit mixers with 35db image rejection adjustable-gain lna up to +2dbm combined receiver input ip3 4db combined receiver noise figure >35db of transmit power control range pa predriver provides up to +2dbm low current consumption: 23ma receive 26ma transmit 9.5ma oscillator 0.5a shutdown mode operates from single +2.7v to +4.8v supply max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers ________________________________________________________________ maxim integrated products 1 28 27 26 25 24 23 22 21 20 19 18 17 16 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 gnd gnd gnd tank txon preout pregnd mod div1 vcoon rxon cap2 n.c. txin lnagain txout gnd gnd rxin txgain rxout cap1 ssop top view max2420 max2421 max2422 MAX2460 max2463 tank v cc v cc v cc v cc v cc ___________________pin configuration 19-1234; rev 4; 1/03 part max2420 eai max2421 eai max2422 eai -40? to +85? -40? to +85? -40? to +85? temp range pin-package 28 ssop 28 ssop 28 ssop _______________ordering information MAX2460 eai -40? to +85? 28 ssop functional diagram appears on last page. max2463 eai -40? to +85? 28 ssop high side injection type f rf + 10.7 lo freq (mhz) high side high side f rf + 70 f rf + 46 max2422 max2421 70 46 low side f rf - 110 max2463 110 max2420 part 10.7 if freq (mhz) ______________________selector guide low side f rf - 10.7 MAX2460 10.7 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. evaluation kit available
? max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers 2 _______________________________________________________________________________________ absolute maximum ratings dc electrical characteristics (v cc = +2.7v to +4.8v, no rf signals applied, lnagain = txgain = open, vcoon = 2.4v, rxon = txon = mod = div1 = 0.45v, pregnd = gnd, t a = t min to t max . typical values are at t a = +25?, v cc = +3.3v, unless otherwise noted.) (note 1) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. note 1: 25? guaranteed by production test, <25? guaranteed through correlation to worst-case temperature testing. note 2: calculated by measuring the combined oscillator and prescaler supply current and subtracting the oscillator supply current. note 3: calculated by measuring the combined oscillator and lo buffer supply current and subtracting the oscillator supply current. note 4: calculated by measuring the combined receive and oscillator supply current and subtracting the oscillator supply current. with lnagain = gnd, the supply current drops by 4.5ma. note 5: calculated by measuring the combined transmit and oscillator supply current and subtracting the oscillator supply current. v cc to gnd ...........................................................-0.3v to +5.5v txin input power (330 ? system) ......................................-8dbm voltage on txout......................................-0.3v to (v cc + 1.0v) voltage on txgain, lnagain, txon, rxon, vcoon, div1, mod ....................-0.3v to (v cc + 0.3v) rxin input power..............................................................10dbm tank, tank input power ...................................................2dbm continuous power dissipation (t a = +70?) ssop (derate 9.50mw/? above +70?) ......................762mw operating temperature range max242_eai/max246_eai ................................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +165? lead temperature (soldering, 10s) .................................+300? parameter min typ max units receive supply current (note 4) 23 36 ma prescaler supply current (buffer mode) (note 3) 5.4 8.5 ma oscillator supply current supply-voltage range 2.7 4.8 v 9.5 14 ma prescaler supply current (divide-by-64/65 mode) (note 2) 4.2 6 ma conditions rxon = 2.4v, pregnd = floating div1 = 2.4v pregnd = floating digital input voltage low 0.45 v transmitter supply current (note 5) 26 42 ma 0.5 rxon, txon, div1, vcoon, mod rxon = 0.45v, txon = 2.4v, pregnd = floating vcoon = rxon = txon = mod = div1 = gnd digital input current ? ?0 ? voltage on any one digital input = v cc or gnd digital input voltage high v 2.4 rxon, txon, div1, vcoon, mod shutdown supply current 10 ? t a = +25? t a = t min to t max
lnagain = 1v ac electrical characteristics (max242x/246x ev kit, v cc = +3.3v; f lo = 925.7mhz (max2420), f lo = 961mhz (max2421), f lo = 985mhz (max2422), f lo = 904.3mhz (MAX2460); f lo = 805mhz (max2463); f rxin = 915mhz; p rxin = -35dbm; p txin = -15dbm (330 ? ); lnagain = 2v; txgain = v cc ; vcoon = 2.4v; rxon = txon = mod = div1 = pregnd = gnd; t a = +25?; unless otherwise noted.) max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers _______________________________________________________________________________________ 3 conditions units min typ max parameter mhz 800 1000 input frequency range (notes 6, 7) max2421 36 46 55 max2420/MAX2460 8.5 10.7 12.5 max2463 mhz 86 110 132 if frequency range (notes 6, 7) 20 22 24.5 max2422 db 26 35 image frequency rejection 55 70 85 lnagain = v cc , t a = +25? 18 20 22.5 18 24 19.5 25 lnagain = 1v 12 div1 = v cc 45 lnagain = v cc , t a = t min to t max (note 6) lnagain = gnd db -16 conversion power gain (note 8) 17 23 19 21 23.5 db 12 noise figure (notes 6, 8) lnagain = 1v dbm -8 input third-order intercept (notes 6, 9) lnagain = v cc -19 -17 (note 10) ns 500 receiver turn-on time mhz 800 1000 output frequency range (notes 6, 7) receiver on or off dbm -60 lo to rxin leakage max2421 36 46 55 max2463 mhz 86 110 132 if frequency range max2420/MAX2460 max2422 55 70 85 db 11 13.5 16 91214.5 10 12.5 15 db 26 35 image frequency rejection 8.5 10.7 12.5 t a = +25? 81113.5 10 15.5 t a = t min to t max (note 6) 814 conversion gain 915 10.5 16.5 lnagain = 1v dbm -18 input 1db compression lnagain = v cc -26 max2420/max2421/MAX2460 max2422 max2463 max2420/max2421/MAX2460 max2422 max2463 max2420/2460 max2421 max2422 max2463 max2420/2460 max2421 max2422 max2463 lnagain = v cc lnagain = 1v receiver (rxon = 2.4v) transmitter (txon = 2.4v)
max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers 4 _______________________________________________________________________________________ ac electrical characteristics (continued) (max242x/246x ev kit, v cc = +3.3v; f lo = 925.7mhz (max2420), f lo = 961mhz (max2421), f lo = 985mhz (max2422), f lo = 904.3mhz (MAX2460); f lo = 805mhz (max2463); f rxin = 915mhz; p rxin = -35dbm; p txin = -15dbm (330 ? ); lnagain = 2v; txgain = v cc ; vcoon = 2.4v; rxon = txon = mod = div1 = pregnd = gnd; t a = +25?; unless otherwise noted.) parameter min typ max units transmitter turn-on time (note 14) gain control range (note 13) 36 txgain control slope (note 13) db 33 db/v 400 ns oscillator phase noise output 1db compression oscillator frequency range (notes 6, 15) 2 dbm 690 1100 mhz 82 dbc/hz 8 10khz offset (note 16) standby to tx, or standby to rx conditions 1v txgain 2v note 6: guaranteed by design and characterization. note 7: image rejection typically falls to 30dbc at the frequency extremes. note 8: refer to the typical operating characteristics for plots showing receiver gain vs. lnagain voltage, input ip3 vs. lnagain voltage, and noise figure vs. lnagain voltage. note 9: two tones at p rxin = -45dbm each, f1 = 915.0mhz and f2 = 915.2mhz. note 10: time delay from rxon = 0.45v to rxon = 2.4v transition to the time the output envelope reaches 90% of its final value. note 11: two tones at p txin = -21dbm each (330 ? ), f1 = 10.6mhz, f2 = 10.8mhz (max2420/MAX2460), f1 = 45.9mhz, f2 = 46.1mhz (max2421), f1 = 69.9mhz, f2 = 70.1mhz (max2422). note 12: refer to the typical operating characteristics for statistical data. note 13: refer to the typical operating characteristics for a plot showing transmitter gain vs. txgain voltage. note 14: time delay from txon = 0.45v to txon = 2.4v transition to the time the output envelope reaches 90% of its final value. note 15: refers to useable operating range. tuning range of any given tank circuit design is typically much narrower (refer to figure 2) . note 16: using tank components l3 = 5.0nh (coilcraft a02t), c2 = c3 = c26 = 3.3pf, r6 = r7 = 10 ? . note 17: this approximates a typical application in which txout is followed by an external pa and a t/r switch with finite isolation. note 18: relative to the rising edge of preout. prescaler output level 500 mv p-p -11 -8 required modulus setup time (note 6) 10 ns z l = 100k ? | | 10pf div1 = 2.4v, z l = 50 ? , t a = +25? divide-by-64/65 mode (note 18) required modulus hold time (note 6) 0 ns divide-by-64/65 mode (note 18) rx to tx with p rxin = -45dbm (rx mode) to p rxin = 0dbm (tx mode) (note 17) 70 oscillator buffer output level (note 6) -12 dbm div1 = 2.4v, z l = 50 ? , t a = t min to t max oscillator pulling khz output third-order intercept (note 11) 11 dbm noise figure 23 lo to txout suppression (note 12) 34 dbc db oscillator and prescaler
max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers _______________________________________________________________________________________ 5 24 28 26 34 32 30 40 38 36 42 -40 0 20 -20 40 60 80 100 receiver supply current vs. temperature max2420-01 temperature (?) i cc (ma) v cc = 2.7v rxon = v cc pregnd = floating includes oscillator current v cc = 3.3v v cc = 4.8v 26 30 28 36 34 32 44 42 40 38 46 -40 0 20 -20 40 60 80 100 tran s mitter s upply c urrent vs. temperature max2420-02 temperature ( c) i cc (ma) v cc = 2.7v v cc = 3.3v v cc = 4.8v txon = v cc pregnd = floating includes oscillator current 0 1.0 0.5 2.5 2.0 1.5 4.0 3.5 3.0 4.5 -40 0 20 -20 40 60 80 100 shutdown supply current vs. temperature max2420-03 temperature ( c) i cc ( a) v cc = 2.7v v cc = 3.3v v cc = 4.8v vcoon = gnd 25 20 15 10 5 0 -5 -10 -15 -20 0 0.5 1.0 1.5 2.0 receiver gain vs. lnagain max2420-04 lnagain voltage (v) receiver gain (db) adjustable gain max gain lna partially biased lna off avoid this region rxon = v cc 18 22 20 26 24 -40 0 20 -20 40 60 80 100 max2420 receiver gain vs. temperature max2420-07 temperature ( c) receiver gain (db) v cc = 2.7v v cc = 3.3v v cc = 4.8v lnagain = v cc rxon = v cc -20 -15 -10 -5 0 5 0 0.5 1.0 1.5 2.0 receiver input ip3 vs. v lnagain max2420-05 lnagain voltage (v) iip3 (dbm) adjustable gain avoid this region max gain lna partially biased lna off rxon = v cc 0 5 15 10 25 20 30 40 35 0 0.5 1.0 1.5 2.0 receiver noise figure vs. lnagain max2420-06 lnagain voltage (v) noise figure (db) adjustable gain avoid this region max gain lna partially biased lna off div1 = v cc rxon = v cc 3.0 4.0 3.5 5.0 5.5 4.5 -40 0 20 -20 40 60 80 100 receiver noise figure vs. temperature and supply voltage max2420-08 temperature ( c) noise figure (db) v cc = 2.7v v cc = 3.3v v cc = 4.8v lnagain = v cc rxon = v cc div1 = v cc -20 -16 -18 -8 -10 -6 -12 -14 -40 0 20 -20 40 60 80 100 receiver input ip3 vs. temperature max2420-09 temperature ( c) iip3 (dbm) lnagain = 1v lnagain = 2v rxon = v cc typical operating characteristics (max242x/246x ev kit, v cc = +3.3v; f lo = 925.7mhz (max2420), f lo = 961mhz (max2421), f lo = 985mhz (max2422), f lo = 904.3mhz (MAX2460); f lo = 805mhz (max2463); f rxin = 915mhz; p rxin = -35dbm; p txin = -15dbm (330 ? ); lnagain = 2v; txgain = v cc ; vcoon = 2.4v; rxon = txon = mod = div1 = pregnd = gnd; t a = +25?; unless otherwise noted.)
max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers 6 _______________________________________________________________________________________ typical operating characteristics (continued) (max242x/246x ev kit, v cc = +3.3v; f lo = 925.7mhz (max2420), f lo = 961mhz (max2421), f lo = 985mhz (max2422), f lo = 904.3mhz (MAX2460); f lo = 805mhz (max2463); f rxin = 915mhz; p rxin = -35dbm; p txin = -15dbm (330 ? ); lnagain = 2v; txgain = v cc ; vcoon = 2.4v; rxon = txon = mod = div1 = pregnd = gnd; t a = +25?; unless otherwise noted.) -20 10 -10 0 30 20 50 40 60 0 400 800 1200 1600 2000 receiver image rejection vs. rf frequency max2420-11 rf frequency (mhz) image rejection (db) rxon = v cc -9 -8 -4 -5 -3 -6 -7 -40 0 20 -20 40 60 80 max2420 rxout 1db compression point vs. temperature max2420-10 temperature ( c) 1db compression point (dbm) v cc = 2.7v v cc = 4.8v v cc = 3.3v rxon = v cc 60 0 1 1000 100 10 receiver image rejection vs. if frequency 20 10 40 30 50 max2420-12 if frequency (mhz) image rejection (db) max2420 MAX2460 max2463 max2422 max2421 rxon = v cc 2 6 4 10 8 14 16 12 18 -40 0 20 -20 40 60 80 100 max2420 transmitter gain vs. temperature max2420 toc16 temperature ( c) transmitter gain (db) v cc = 2.7v v cc = 4.8v txon = v cc v cc = 3.3v 0 25 30 15 20 10 5 35 40 45 50 -0 -60 -40 -20 -80 -100 800 600 1000 1200 1400 rxin input impedance vs. frequency max2420 toc14 frequency (mhz) real impedance ( ? ) imaginary impedance ( ? ) real imaginary rxon = v cc -40 -30 -10 -20 10 0 20 0.5 2.0 1.5 1.0 2.5 3.0 3.5 4.5 4.0 5.0 transmitter gain vs. txgain voltage max2420 toc15 txgain voltage (v) transmitter gain (db) v cc = 2.7v v cc = 4.8v v cc = 3.3v txon = v cc -300 -200 -250 -50 -100 -150 0 50 100 150 800 600 1000 1200 1400 1600 1800 2000 txout output impedance vs. frequency max2420toc17 frequency (mhz) real or imaginary impedance ( ? ) real imaginary txon = v cc -90 -70 -80 -50 -60 -30 -40 -20 0 -10 10 875 895 905 915 885 925 935 945 965 955 975 max2420 transmitter output spectrum max2420/21/22 toc18 frequency (mhz) power (dbm) fundamental txon = v cc lo image -70 -90 -80 -100 -60 -40 -50 -30 -10 -20 0 855 885 865 875 895 905 925 915 935 945 955 MAX2460 transmitter output spectrum max2420/21/22 toc18.1 frequency (mhz) power (dbm) txon = v cc image lo fundamental
max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers _______________________________________________________________________________________ 7 -1.0 0 -0.5 1.0 0.5 2.5 2.0 1.5 3.0 -40 0 -20 20 40 60 80 100 transmitter 1db compression point vs. temperature max2420/21/22toc19 temperature ( c) output 1db compression (dbm) v cc = 4.8v v cc = 3.3v v cc = 2.7v txon = v cc 42 44 46 48 50 52 54 1.0 2.0 1.5 2.5 3.0 3.5 4.0 4.5 5.0 max2420 transmitter im3 rejection vs. txgain voltage max2420/21/22 toc20 txgain voltage (v) im3 rejection v cc = 2.7v v cc = 3.3v txon = v cc f1 = 10.6mhz f2 = 10.8mhz -21dbm per tone v cc = 4.8v 0 20 25 15 10 5 35 30 40 45 100 900 500 1300 1700 2100 transmitter image rejection vs. rf frequency max2420/21/22 toc21 rf frequency (mhz) image rejection (db) txon = v cc 50 0 1 10 100 1000 transmitter image rejection vs. if frequency 10 5 max2420-22 if frequency (mhz) image rejection (db) 20 15 30 35 25 40 45 max2420 max2463 txon = v cc max2422 max2421 MAX2460 4 2 0 6 10 8 12 16 14 18 24 28 30 32 26 34 36 38 42 40 44 46 48 50 max2420 transmitter lo suppression histogram (n = 86) max2420/21/22 toc18.5 lo suppression (dbc) count txon = v cc -70 -90 -80 -100 -60 -40 -50 -30 -10 -20 0 710 810 910 1010 1110 1210 max2421 transmitter output spectrum max2420/21/22 toc18.2 frequency (mhz) power (dbm) txon = v cc image lo fundamental 550 500 0 1 1k 10k 100 100k prescaler output level vs. load resistance 100 50 max2420/21/22 toc24 load resistance ( ? ) prescaler output level (mvp-p) 200 150 350 300 250 450 400 load is plotted resistance in parallel with a 10pf oscilloscope probe ( 64/65 mode) typical operating characteristics (continued) (max242x/246x ev kit, v cc = + 3.3v; f lo = 925.7mhz (max2420), f lo = 961mhz (max2421), f lo = 985mhz (max2422), f lo = 904.3mhz (MAX2460); f lo = 805mhz (max2463); f rxin = 915mhz; p rxin = -35dbm; p txin = -15dbm (330 ? ); lnagain = 2v; txgain = v cc ; vcoon = 2.4v; rxon = txon = mod = div1 = pregnd = gnd; t a = +25?; unless otherwise noted.) -70 -90 -80 -100 -60 -40 -50 -30 -10 -20 0 735 835 935 1035 1135 1235 max2422 transmitter output spectrum max2420/21/22 toc18.3 frequency (mhz) power (dbm) txon = v cc image lo fundamental -70 -90 -80 -100 -60 -40 -50 -30 -10 -20 0 605 655 705 1005 1055 1105 max2463 transmitter output spectrum max2420/21/22 toc18.4 frequency (mhz) power (dbm) txon = v cc image lo fundamental
max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers 8 _______________________________________________________________________________________ pin description supply voltage input for receive low-noise amplifier. bypass with a 47pf low-inductance capacitor to gnd (pin 7 if possible). 6 receiver rf input, single-ended. the input match shown in figure 1 maintains an input vswr of better than 2:1 from 902mhz to 928mhz. 5 transmit gain-control input. connect to v cc for highest gain and best temperature stability. when driven with a control voltage, the if buffer gain can be adjusted over a 36db range (see typical operating characteristics ). 4 v cc rxin txgain prescaler/oscillator buffer output. in divide-by- 64/65 mode (div1 = low), the output level is 500mvp-p into a high-impedance load. in divide-by-1 mode (div1 = high), this output delivers -8dbm into a 50 ? load. ac couple to this pin. 21 transmit bias compensation pin. bypass with a 47pf low-inductance capacitor and 0.01? to gnd. do not make any other connections to this pin. 14 no connect. not internally connected. 13 ground connection for the prescaler. tie pregnd to ground for normal operation. leave floating to disable the prescaler and the output buffer. tie mod and div1 to ground and leave preout floating when disabling the prescaler. cap2 n.c. transmitter if input, 330 ? , single-ended. ac couple to this pin. 12 single-ended, 330 ? if output. ac couple to this pin. 3 receive bias compensation pin. bypass with a 47pf low-inductance capacitor and 0.01? to gnd. do not make any other connections to this pin. 2 supply-voltage input for master bias cell. bypass with a 47pf low-inductance capacitor and 0.1? to gnd (pin 28, if possible). 1 function pin low-noise amplifier gain-control input. drive this pin high for maximum gain. when lnagain is pulled low, the lna is capacitively bypassed and the supply current is reduced by 4.5ma. this pin can also be driven with an analog voltage to adjust the lna gain in intermediate states. refer to the receiver gain vs. lnagain voltage graph in the typical operating characteristics, as well as table 1. 10 pa predriver output. see figure 1 for an example matching network, which provides better than 2:1 vswr from 902mhz to 928mhz. 9 txin lnagain txout ground connection for receive low-noise amplifier 7 gnd rxout cap1 v cc name ground connection for signal-path blocks, except lna 8 gnd supply voltage input for signal-path blocks, except lna. bypass with a 47pf low-inductance capacitor and 0.01? to gnd (pin 8, if possible). 11 v cc 20 preout pregnd modulus control for the d ivide-by- 64/65 prescaler: high = divide-by- 64, low = divide-by- 65. note that the div1 pin must be at logic low when using the prescaler mode. 19 driving vcoon with a logic high turns on the vco, phase shifters, vco buffers, and prescaler. the prescaler can be selectively disabled by floating the pregnd pin. 17 driving rxon with a logic high enables the lna, receive mixer, and if output buffer. vcoon must also be high. 16 mod vcoon rxon driving txon with a logic high enables the transmit if variable-gain amplifier, upconverter mixer, and pa predriver. vcoon must also be high. 15 txon driving div1 with a logic high disables the divide- by-64/65 prescaler and connects the preout pin directly to an oscillator buffer amplifier, which outputs -8dbm into a 50 ? load. tie div1 low for divide-by- 64/65 operation. pull this pin low when in shutdown to minimize off current. 18 div1
max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers _______________________________________________________________________________________ 9 pin description (continued) ground connection for vco and phase shifters 26 gnd ground (substrate) 27 gnd ground connection for master bias cell 28 gnd supply-voltage input for vco and phase shifters. bypass with a 47pf low-inductance capacitor to gnd (pin 26 if possible). 23 v cc supply-voltage input for prescaler. bypass with a 47pf low-inductance capacitor and 0.01? to gnd (pin 20 if possible). 22 v cc function pin name differential oscillator tank port. see applications information for information on tank circuits or on using an external oscillator. 25 differential oscillator tank port. see applications information for information on tank circuits or on using an external oscillator. 24 tank tank v cc v cc v cc 17 16 15 18 19 21 1000pf transmit if input (330 ? ) varactor: alpha smv1299-004 or equivalent receive if output (330 ? ) see applications information section l3: coilcraft 0805hs-060tjbc coilcraft 0805hs-030tjbc 27 23 26 3 12 20 22 1 28 receive rf input transmit rf output 5 9 7 6 0.01 f 0.01 f 47pf v cc v cc 0.1 f v cc v cc 2 47pf 0.1 f 8.2nh 12nh 22nh 18nh 47pf 47pf 47pf 8 11 0.01 f 47pf 0.01 f max2420 max2421 max2422 MAX2460 max2463 6.8 3.3 3.3 6.8 6.8 l3 (nh) part vco tank components for 915mhz typical rf c26 (pf) c2, c3 (pf) 1.8 3.6 3.0 1.5 2.4 3.3 4.0 4.0 4.0 4.7 r6, r7 ( ? ) 10 15 20 15 15 47pf 47pf 14 0.01 f 47pf rxin txout gnd v cc v cc gnd cap2 gnd cap1 v cc v cc txon rxon vcoon div1 mod preout txon rxon vcoon div1 mod to pll gnd rxout txin 100nh gnd pregnd 47pf v cc 24 25 vco adjust c3 1k ? 47k ? 47pf 1k ? c2 r6 r7 v cc l3 c26 tank txgain lnagain txgain lnagain 10 4 max2420 max2421 max2422 MAX2460 max2463 tank figure 1. typical operating circuit
max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers 10 ______________________________________________________________________________________ detailed description the following sections describe each of the functional blocks shown in the functional diagram. receiver the max2420/max2421/max2422/MAX2460/max2463 s receive path consists of a 900mhz low-noise amplifier, an image-reject mixer, and an if buffer amplifier. the lna s gain and biasing are adjustable through the lnagain pin. proper operation of this pin can provide optimum performance over a wide range of signal lev- els. the lna can be placed in four modes by applying a dc voltage on the lnagain pin. see table 1, as well as the relevant typical operating characteristics plots. at low lnagain voltages, the lna is shut off, and the input signal capacitively couples directly into the mixer to provide maximum linearity for large-signal operation (receiver close to transmitter). as the lnagain voltage is raised, the lna begins to turn on. between 0.5v and 1v at lnagain, the lna is partially biased and behaves like a class c amplifier. avoid this operating mode for applications where linearity is a concern. as the lnagain voltage reaches 1v, the lna is fully biased into class a mode, and the gain is monotonical- ly adjustable at lnagain voltages above 1v. see the receiver gain, receiver ip3, and receiver noise figure vs. lnagain plots in the typical operating characteristics for more information. the downconverter is implemented using an image- reject mixer consisting of an input buffer with two out- puts, each of which is fed to a double-balanced mixer. the local-oscillator (lo) port of each mixer is driven from a quadrature lo. the lo is generated from an on- chip oscillator and an external tank circuit. its signal is buffered and split into phase shifters, which provide 90 of phase shift across their outputs. this pair of lo signals is fed to the mixers. the mixers outputs are then passed through a second pair of phase shifters, which provide a 90 phase shift across their outputs. the resulting mixer outputs are then summed together. the final phase relationship is such that the desired signal is reinforced and the image signal is canceled. the down- converter mixer output appears on the rxout pin, a sin- gle-ended 330 ? output. transmitter the transmitter operates similarly to the receiver, but with the phase shifters at the mixer inputs. the transmit- ter consists of an input buffer amplifier with more than 36db of gain-adjustment range via the txgain pin. this buffer s output is split internally into an in-phase (i) and a quadrature-phase (q) path. if phase-shifting net- works give the q-channel path a 90 phase shift with respect to the i channel. the i and q signals are input to a pair of double-balanced mixers, driven with quad- rature lo. the mixer outputs are then summed, cancel- ing the image component. the image-rejected output signal is fed to the pa predriver, which outputs typically -3dbm on the txout pin. since the transmit and receive sections share an lo and an if frequency, interference results if both sec- tions are active at the same time. phase shifters max2420/max2421/max2422/MAX2460/max2463 devices use passive networks to provide quadrature phase shifting for the receive if, transmit if, and lo signals. because these networks are frequency selec- tive, proper part selection is important. image rejection degrades as the if and rf move away from the designed optimum frequencies. the max2420/ max2421/max2422 s phase shifters are arranged such that the lo frequency is higher than the rf carrier fre- quency (high-side injection), while the MAX2460/ max2463 s phase shifters are arranged such that the lo frequency is lower than the rf carrier frequency (low-side injection). refer to the selector guide . local oscillator (lo) the on-chip lo is formed by an emitter-coupled differ- ential pair. an external lc resonant tank sets the oscil- lation frequency. a varactor diode is typically used to create a voltage-controlled oscillator (vco). see the applications information section for an example vco tank circuit. the lo may be overdriven in applications where an external signal is available. the external lo signal should be about 0dbm from 50 ? , and should be ac coupled into either the tank or tank pin. both tank and tank require pull-up resistors to v cc . see the applications information section for details. lna partially biased. avoid this mode the lna operates in a class c manner lna capacitively bypassed, minimum gain, maximum ip3 mode lna at maximum gain (remains monotonic) lna gain is monotonically adjustable 1.5 < v v cc 1.0 < v 1.5 0.5 < v < 1.0 0 < v 0.5 lnagain voltage (v) table 1. lna modes
max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers ______________________________________________________________________________________ 11 the local oscillator is resistant to lo pulling caused by changes in load impedance that occur as the part is switched from standby mode, with just the oscillator run- ning to either transmit or receive mode. the amount of lo pulling is affected if there is power at the rxin port in transmit mode. the most common cause of this is imper- fect isolation in an external transmit/receive (t/r) switch. the ac electrical characteristics table contains specifi- cations for this case as well. prescaler the on-chip prescaler can be used in two different modes: as a dual-modulus divi de-by- 64/65, or as oscil- lator buffer amplifier. the div1 pin controls this func- tion. when div1 is low, the prescaler is in dual-modulus divide-by- 64/65 mode; when it is high, the prescaler is disabled and the oscillator buffer amplifier is enabled. the buffer typically outputs -8dbm into a 50 ? load. to minimize shutdown supply current, pull the div1 pin low when in shutdown mode. in divide-by- 64/65 mode, the division ratio is controlled by the mod pin. when mod is high, the prescaler is in divide-by-64 mode; when it is low, it divides the lo fre- quency by 65. the div1 pin must be at a logic low in this mode. to disable the prescaler entirely, leave pregnd and preout floating. also tie the mod and div1 pins to gnd. disabling the prescaler does not affect operation of the vco stage. power management max2420/max2421/max2422/MAX2460/max2463 sup- ports four different power-management features to con- serve battery life. the vco section has its own control pin (vcoon), which also serves as a master bias pin. when vcoon is high, the lo, quadrature lo phase shifters, and prescaler or lo buffer are all enabled. the vco can be powered up prior to either transmitting or receiving, to allow it to stabilize. for transmit-to-receive switching, the receiver and transmitter sections have their own enable control inputs, rxon and txon. with vcoon high, bringing rxon high enables the receive path, which consists of the lna, image-reject mixers, and if output buffer. when this pin is low, the receive path is inactive. the txon input enables the if adjustable-gain amplifier, upconverter mixer, and pa predriver. vcoon must be high for the transmitter to operate. when txon is low, the transmitter is off. to disable all chip functions and reduce the supply current to typically less than 0.5a, pull vcoon, div1, mod, rxon, and txon low. applications information oscillator tank the on-chip oscillator requires a parallel-resonant tank circuit connected across tank and tank . figure 2 shows an example of an oscillator tank circuit. inductor l4 provides dc bias to the tank ports. inductor l3, capacitor c26, and the series combination of capaci- tors c2, c3, and both halves of the varactor diode capacitance set the resonant frequency as follows: where c d1 is the capacitance of one varactor diode. choose tank components according to your application needs, such as phase-noise requirements, tuning range, and vco gain. high-q inductors such as air- core micro springs yield low phase noise. use a low tol- erance inductor (l3) for predictable oscillation frequency. resistors r6 and r7 can be chosen from 0 to 20 ? to reduce the q of parasitic resonance due to series package inductance (l t ). keep r6 and r7 as small as possible to minimize phase noise, yet large enough to ensure oscillator start up in fundamental mode. oscillator start-up is most critical with high tun- ing bandwidth (low tank q) and high temperature. capacitors c2 and c3 couple in the varactor. light c = 1 1 c2 1 c3 2 c c26 eff d1 ++ ? ? ? ? ? ? + f = 1 2l3c r eff () () ? ? ? ? ? ? max2420 max2421 max2422 MAX2460 max2463 l t l t l3 c26 l4 100nh r5 1k ? r4 1k ? d1 = alpha smv1299-004 see figure 1 for r6, r7, c2, c3, c26, and l3 component values. 1/2 d1 1/2 d1 c1 47pf vco_ctrl r7 r6 c3 r8 47k ? c2 v cc figure 2. oscillator tank schematic, using the on-chip vco
max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers 12 ______________________________________________________________________________________ coupling of the varactor is a way to reduce the effects of high-varactor tolerance and increase loaded q. for a wider tuning range use larger values for c2 and c3 or a varactor with a large capacitance ratio. capacitor c26 is used to trim the tank oscillator frequency. larger val- ues for c26 helps negate the effect of stray pcb capacitance and parasitic inductor capacitance (l3). choose a low-tolerance capacitor for c26. for applications that require a wide tuning range and low phase noise, a series coupled resonant tank may be required as shown in figure 4. this tank uses the package inductance in series with inductors l1, l2, and capacitance of varactor d1 to set the net equiva- lent inductance which resonates in parallel with the internal oscillator capacitance. inductors l1 and l2 can be implemented as microstrip inductors, saving com- ponent cost. bias is provided to the tank port through chokes l3 and l5. r1 and r3 should be chosen large enough to de-q the parasitic resonance due to l3 and l5, but small enough to minimize the voltage drop across them due to bias current. values for r1 and r3 should be kept between 0 and 50 ? . proper high-fre- quency bypassing (c1) should be used for the bias voltage to eliminate power supply noise from entering the tank. oscillator-tank pc board layout the parasitic pc board capacitance, as well as pcb trace inductance and package inductance, can affect oscillation frequency, so be careful in laying out the pc board for the oscillator tank. keep the tank layout as symmetrical, tightly packed, and close to the device as possible to minimize lo feedthrough. when using a pc board with a ground plane, a cut-out in the ground plane (and any other planes) below the oscillator tank reduces parasitic capacitance. using an external oscillator if an external 50 ? lo signal source is available, it can be used as an input to the tank or tank pin in place of the on-chip oscillator (figure 3). the oscillator signal is ac coupled into the tank pin and has a level of about 0dbm from a 50 ? source. for proper biasing of the oscillator input stage, the tank and tank pins must be pulled up to the v cc supply via 50 ? resistors. if the application requires overdriving the internal oscil- lator, the pull-up resistors can be increased in order to save power. if a differential lo source such as the max2620 is available, ac couple the inverting output into tank . max2420 max2421 max2422 MAX2460 max2463 tank 50 ? 50 ? ext lo external lo level is 0dbm from a 50 ? source. v cc c block 0.01 f v cc tank figure 3. using an external local oscillator max2420 max2421 max2422 MAX2460 max2463 tank l1 l t l t l2 l3 l4 l5 r1 r2 r3 c i c1 c2 v cc v tune tank figure 4. series coupled resonant tank for wide tuning range and low phase noise
max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers ______________________________________________________________________________________ 13 functional diagram rxon txon cap2 txout cap1 rxin lnagain 90 90 90 0 0 max2420 max2421 max2422 MAX2460* max2463* phase shifter 1/64/65 bias rxout div1 mod preout pregnd tank tank vcoon txin *criss-crossed phase-shifter connections txgain 90 0 0
max2420/max2421/max2422/MAX2460/max2463 900mhz image-reject transceivers ssop.eps package outline, ssop, 5.3 mm 1 1 21-0056 c rev. document control no. approval proprietary information title: notes: 1. d&e do not include mold flash. 2. mold flash or protrusions not to exceed .15 mm (.006"). 3. controlling dimension: millimeters. 4. meets jedec mo150. 5. leads to be coplanar within 0.10 mm. 7.90 h l 0 0.301 0.025 8 0.311 0.037 0 7.65 0.63 8 0.95 max 5.38 millimeters b c d e e a1 dim a see variations 0.0256 bsc 0.010 0.004 0.205 0.002 0.015 0.008 0.212 0.008 inches min max 0.078 0.65 bsc 0.25 0.09 5.20 0.05 0.38 0.20 0.21 min 1.73 1.99 millimeters 6.07 6.07 10.07 8.07 7.07 inches d d d d d 0.239 0.239 0.397 0.317 0.278 min 0.249 0.249 0.407 0.328 0.289 max min 6.33 6.33 10.33 8.33 7.33 14l 16l 28l 24l 20l max n a d e a1 l c h e n 12 b 0.068 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. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 14 ? 2003 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .)

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