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general description the MAX2822 single-chip transceiver is designed for 802.11b (11mbps) applications operating in the 2.4ghz to 2.5ghz ism band. the transceiver includes all the circuitry required to implement an 802.11b rf-to-base- band transceiver solution, including the power amplifi- er, transmit/receive switch, and 50 ? matching. the fully integrated receive path, transmit path, vco, frequency synthesis, and baseband/control interface provide all the required active rf circuitry. only a small number of passive components are needed to form the complete radio front-end solution. the ic eliminates the need for external if saw and rf image-reject filters by utilizing a direct-conversion radio architecture and monolithic baseband filters for both receiver and transmitter. it is specifically optimized for 802.11b (11mbps cck) and 22mbps pbcc applica- tions. the baseband filtering and rx and tx signal paths support the cck modulation scheme for ber = 10 -5 at the required sensitivity levels. the transceiver is suitable for the full range of 802.11b data rates (1mbps, 2mbps, 5.5mbps, and 11mbps) as well as the higher-rate 22mbps pbcc standard. the MAX2822 is available in the very small 7mm x 7mm 48- lead qfn or thin qfn packages. the small solution size makes it ideal for small form-factor 802.11b applications such as pdas, smartphones, and embedded modules. applications 802.11b pdas and smartphones 802.11b embedded modules 802.11b pc cards, mini-pci cards features ? 2.4ghz to 2.5ghz ism band operation ? 802.11b (11mbps cck and 22mbps pbcc) phy compatible ? integrated +17dbm pa ? integrated pa power detector ? integrated transmit/receive switch ? complete rf-to-baseband transceiver direct up/down conversion monolithic low-phase-noise vco integrated baseband lowpass filters integrated pll with 3-wire serial interface digital bias control for pa transmit power control receive baseband agc complete baseband interface digital tx/rx mode control ? -95dbm rx sensitivity at 1mbps ? -85dbm rx sensitivity at 11mbps ? single +2.7v to +3.0v supply ? 2? shutdown mode ? very small 48-pin qfn package MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch ________________________________________________________________ maxim integrated products 1 ordering information 19-2884; rev 0; 7/03 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. pin configuration/functional diagram appears at end of data sheet. pbcc is a trademark of texas instruments, inc. part temp range pin-package MAX2822egm -40 c to +85 c 48 qfn MAX2822etm -40 c to +85 c 48 thin qfn evaluation kit available
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch 2 _______________________________________________________________________________________ absolute maximum ratings dc electrical characteristics (MAX2822 ev kit: v cc = +2.7v to +3.0v, rf_gain = v ih , 0v v tx_gc +2.0v, 0v v rx_agc +2.0v, r bias = 12k ? , no input sig- nals at rf and baseband inputs, rf i/o terminated into 50 ? though a 2:1 balun, receiver baseband outputs are open, transmitter baseband inputs biased at +1.2v, registers set to default power-up settings, t a = -40? to +85?, unless otherwise noted. typical values are for v cc = +2.7v, t a = +25?, 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. v cc pins to gnd ...................................................-0.3v to +3.6v rf i/o: rfp, rfn (current into pin).....................................50ma baseband inputs: tx_bbip, tx_bbin, tx_bbqp, tx_bbqn to gnd ..................................-0.3v to (v cc + 0.3v) baseband outputs: rx_bbip, rx_bbin, rx_bbqp, rx_bbqn to gnd ..................................-0.3v to (v cc + 0.3v) analog inputs: rx_agc, tx_gc, tune, roscn, roscp to gnd ......................................-0.3v to (v cc + 0.3v) analog outputs: pwr_det, cp_out to gnd....................................................-0.3v to (v cc + 0.3v) digital inputs: rx_on, tx_on, shdnb, csb, sclk, din, rf_gain, rx_1k to gnd...............-0.3v to (v cc + 0.3v) bias voltages: rbias, byp ..................................+0.9v to +1.5v short-circuit duration digital output: dout ..........................10s rf input power ...............................................................+10dbm continuous power dissipation (t a = +70?) 48-lead qfn (derate 27.0mw/ c above +70?) ......2162mw operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +160? lead temperature (soldering, 10s) .................................+300? parameters conditions min typ max units supply voltage 2.7 3.0 v shutdown current shdnb = v il , rx_on = v il , tx_on = v il 250a t a = +25? 25 35 standby-mode supply current shdnb = v ih , rx_on = v il , tx_on = v il t a = -40? to +85? 40 ma t a = +25? 80 100 receive-mode supply current shdnb = v ih , rx_on = v ih , tx_on = v il t a = -40? to +85? 110 ma p out = +3dbm 98 t a = +25? 157 175 p out = +12dbm t a = -40? to +85? 185 transmit-mode supply current s h dn b = v ih , rx _on = v il , tx _on = v ih , b i as r eg i ster s set as i n tab l e 9 p out = +17dbm 220 ma logic inputs: shdnb, rx_on, tx_on, sclk, din, csb, rf_gain digital input voltage high (v ih ) v cc - 0.5 v digital input voltage low (v il ) 0.5 v digital input current high (i ih )-5+5a digital input current low (i il )-5+5a logic output: dout digital output voltage high (v oh ) sourcing 100? v cc - 0.5 v digital output voltage low (v ol ) sinking 100? 0.5 v analog output: pwr_det power-detector output impedance 400 ?
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch _______________________________________________________________________________________ 3 dc electrical characteristics (continued) (MAX2822 ev kit: v cc = +2.7v to +3.0v, rf_gain = v ih , 0v v tx_gc +2.0v, 0v v rx_agc +2.0v, r bias = 12k ? , no input sig- nals at rf and baseband inputs, rf i/o terminated into 50 ? though a 2:1 balun, receiver baseband outputs are open, transmitter baseband inputs biased at +1.2v, registers set to default power-up settings, t a = -40? to +85?, unless otherwise noted. typical values are for v cc = +2.7v, t a = +25?, unless otherwise noted.) (note 1) parameters conditions min typ max units rx baseband i/o rx_agc input resistance 0v v rx_agc +2.0v 50 k ? rx i/q common-mode voltage 1.25 v rx i/q output dc offsets 3 limit ?5 mv tx baseband i/o tx bb input common-mode range 1.0 1.2 1.4 v tx bbi and bbq input bias current -10 ? tx bb input impedance differential resistance 100 k ? tx_gc input bias current 0v v tx_gc +2.0v 10 ? tx_gc input impedance resistance 250 k ? reference oscillator input reference oscillator input impedance 20 k ? voltage reference reference voltage i load = ?ma 1.10 1.20 1.30 v ac electrical characteristics?eceive mode (MAX2822 ev kit: v cc = +2.7v to +3.0v, f rf and f lo = 2400mhz to 2499mhz, f osc = 22mhz or 44mhz, receive baseband output levels = 500mv p-p , v shdnb = v rx_on = v ih , v tx_on = v il , v csb = v ih , v sclk = v din = v il , v rf_gain = v ih , 0v v rx_agc +2.0v, r bias = 12k ? , i cp = +2ma, bw pll = 45khz, registers set to default power-up settings, t a = +25?, unless otherwise noted. typical values are for v cc = +2.7v, f lo = 2437mhz, f osc = 22mhz, unless otherwise noted.) (note 2) parameter conditions min typ max units receiver cascaded performance (rf input to baseband output) rf frequency range 2400 2499 mhz lo frequency range 2400 2499 mhz t a = +25? 97 105 rf_gain = v ih , v rx_agc = 0v t a = -40? to +85? 95 rf_gain = v ih , v rx_agc = +2.0v 35 rf_gain = v il , v rx_agc = 0v 75 voltage gain (note 3) rf_gain = v il , v rx_agc = +2.0v 3 db rf gain step from rf_gain = v ih to rf_gain = v il 32 db
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch 4 _______________________________________________________________________________________ ac electrical characteristics?eceive mode (continued) (MAX2822 ev kit: v cc = +2.7v to +3.0v, f rf and f lo = 2400mhz to 2499mhz, f osc = 22mhz or 44mhz, receive baseband output levels = 500mv p-p , v shdnb = v rx_on = v ih , v tx_on = v il , v csb = v ih , v sclk = v din = v il , v rf_gain = v ih , 0v v rx_agc +2.0v, r bias = 12k ? , i cp = +2ma, bw pll = 45khz, registers set to default power-up settings, t a = +25?, unless otherwise noted. typical values are for v cc = +2.7v, f lo = 2437mhz, f osc = 22mhz, unless otherwise noted.) (note 2) parameter conditions min typ max units rf_gain = v ih , rx gain 80db 5.5 6.0 rf_gain = v ih , rx gain = 50db 8 dsb noise figure (note 4) rf_gain = v il , rx gain = 50db 35 db adjacent channel rejection rx gain = 70db (note 5) 45 db rf_gain = v ih , rx gain = 80db -13 input third-order intercept point (note 6) rf_gain = v il , rx gain = 50db +19 dbm rf_gain = v ih , rx gain = 80db +23 input second-order intercept point (note 7) rf_gain = v il , rx gain = 50db +60 dbm lo leakage at balun input -65 dbm input return loss 15 db receiver baseband baseband filter response -3db frequency default bandwidth setting bw(2:0) = (010) 7 mhz at 12.5mhz 40 at 16mhz 65 at 20mhz 70 attenuation relative to passband at 25mhz 85 db baseband output characteristics rx i/q gain imbalance 3 limit ? db rx i/q phase quadrature imbalance 3 limit ? d eg r ees rx i/q output 1db compression differential voltage into 5k ? 1 v p-p rx i/q output thd v out = 500mv p-p at 5.5mhz, z l = 5k ? ||5pf -35 dbc baseband agc amplifier agc range v rx_agc = 0 to +2.0v 70 db agc slope peak gain slope 60 db/v agc response time 20db gain step (80db to 60db), settling to 1db 2s
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch _______________________________________________________________________________________ 5 ac electrical characteristics?ransmit mode (MAX2822 ev kit, characteristics relative to rfp/rfn: v cc = +2.7v to +3.0v, f rf and f lo = 2400mhz to 2499mhz, f osc = 22mhz or 44mhz, transmit baseband input signal: 500mv p-p at 5.5mhz, v shdnb = v rx_on = v il , v tx_on = v ih , v csb = v ih , v sclk = v din = v il , v rf_gain = v ih , 0v v tx_agc +2.0v, r bias = 12k ? , i cp = +2ma, bw pll = 45khz, baseband inputs dc biased to +1.2v, reg- isters set to default power-up settings, measurements taken within 1s of txon rising edge, t a = +25?, unless otherwise noted. typical values are for v cc = +2.7v, f lo = 2437mhz, f osc = 22mhz, unless otherwise noted.) (note 2) parameter conditions min typ max units transmit signal path: baseband input to rf output rf output frequency range 2400 2499 mhz lo output frequency range 2400 2499 mhz t a = +25? + 16.5 + 17.5 tx rf output power 11mb p s c c k si g nal , ac pr ( ad j ) - 30d bc, ac pr ( al t) - 50d bc ( n ote 4) t a = - 40c to + 85c + 15.5 dbm adjacent (adj): -22mhz f offset -11mhz, 11mhz f offset 22mhz, p out = + 16.5d bm -33 tx rf acpr (note 8) alternate (alt): -33mhz f offset < -22mhz, 22mhz < f offset 33mhz, p out = + 16.5d bm -56 dbc unwanted sideband -40 lo signal -30 in-band spurious signals relative to carrier f rf = 2400mhz to 2483mhz (note 9) spurs > 22mhz -80 dbc 2 f rf -45 tx rf harmonics 11mbps cck at +16.5dbm 3 f rf -30 dbm < 2400mhz -50 2500mhz to 3350mhz -35 tx rf spurious signal emissions (outside 2400mhz to 2483.5mhz) nonharmonic signals > 3350mhz -40 dbm tx rf output noise f offset 22mhz, 0v v tx_gc +2.0v -125 dbm/hz tx rf output return loss 100 ? balanced output impedance, p out = +17dbm 10 db tx baseband filter response -3db frequency 10 mhz at 22mhz 25 attenuation relative to passband at 44mhz 50 db tx gain-control characteristics gain-control range 0v v tx_gc +2.0v 20 db gain-control slope peak gain slope 30 db/v gain-control response time v tx_gc = +2.0v to 0v step, settled to within ?db 0.3 ?
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch 6 _______________________________________________________________________________________ ac electrical characteristics?ransmit mode (continued) (MAX2822 ev kit, characteristics relative to rfp/rfn: v cc = +2.7v to +3.0v, f rf and f lo = 2400mhz to 2499mhz, f osc = 22mhz or 44mhz, transmit baseband input signal: 500mv p-p at 5.5mhz, v shdnb = v rx_on = v il , v tx_on = v ih , v csb = v ih , v sclk = v din = v il , v rf_gain = v ih , 0v v tx_agc +2.0v, r bias = 12k ? , i cp = +2ma, bw pll = 45khz, baseband inputs dc biased to +1.2v, reg- isters set to default power-up settings, measurements taken within 1s of txon rising edge, t a = +25?, unless otherwise noted. typical values are for v cc = +2.7v, f lo = 2437mhz, f osc = 22mhz, unless otherwise noted.) (note 2) parameter conditions min typ max units power detector power-detection range 0.1v v pwr_det 1.5v 17 db p out = +3dbm ?.7 power-detection error (3 limit) fixed v pwr_det , t a = +25? p out = +17dbm ?.5 db power-detection error variation with temperature t a = -40? to +85?, relative to t a = +25? ?.3 db ac electrical characteristics?ynthesizer (MAX2822 ev kit: v cc = +2.7v to +3.0v, f rf and f lo = 2400mhz to 2499mhz, f osc = 22mhz or 44mhz, shdnb = v ih , csb = v ih , r bias = 12k ? , i cp = +2ma, bw pll = 45khz, registers set to default power-up settings, t a = +25?, unless otherwise noted. typical values are for v cc = +2.7v, f lo = 2437mhz, f osc = 22mhz, unless otherwise noted.) (note 2) parameter conditions min typ max units frequency synthesizer lo frequency range 2400 2499 mhz synth:r(0) = 0 22 reference frequency synth:r(0) = 1 44 mhz minimum channel spacing 1 mhz charge-pump output current ? ma charge-pump compliance range 0.4 v cc - 0.4 v -11mhz f offset 11mhz -41 -22mhz f offset < -11mhz, 11mhz < f offset 22mhz -75 reference spur level (note 10) f offset < -22mhz, f offset > 22mhz -90 dbc f offset = 10khz -80 closed-loop phase noise f offset = 100khz -87 dbc/hz closed-loop integrated phase noise noise integrated from 100hz to 10mhz, measured at the tx_rf output 2.5 rms reference oscillator input level ac-coupled sine wave input 200 300 500 mv p-p voltage-controlled oscillator f lo = 2400mhz 0.4 vco tuning voltage range f lo = 2499mhz 2.3 v f lo = 2400mhz 170 vco tuning gain f lo = 2499mhz 130 mhz/v
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch _______________________________________________________________________________________ 7 note 1: parameters are production tested at +25 c only. min/max limits over temperature are guaranteed by design and characterization. note 2: guaranteed by design and characterization. note 3: defined as the baseband differential rms output voltage divided by the rms input voltage (at the rf balun input). note 4: specification excludes the loss of the external balun. the external balun loss is typically ~0.5db. note 5: cck interferer at 25mhz offset. desired signal equals -73dbm. interferer amplitude increases until baseband output from interferer is 10db below desired signal. adjacent channel rejection = p interferer - p desired . note 6: measured at balun input. two cw tones at -43dbm with 15mhz and 25mhz offset from the MAX2822 channel frequency. ip3 is computed from 5mhz imd3 product measured at the rx i/q output. note 7: two cw interferers at -38dbm with 24.5mhz and 25.5mhz offset from the MAX2822 channel frequency. ip2 is computed from the 1mhz imd2 product measured at the rx i/q output. note 8: v txgc adjusted for +16.5 dbm output power; adjacent and alternate channel power relative to the desired signal. power measured with 100khz video bw and 100khz resolution bw. note 9: cw tone at 2.25mhz offset from carrier with v txgc set for maximum modulated p out at -30dbc/-50dbc (adj/alt) acpr limits. unwanted sideband refers to suppressed image resulting from i/q baseband input tones. note 10: relative amplitude of reference spurious products appearing in the tx rf output spectrum relative to a cw tone at 2.25mhz offset from the lo. note 11: time required to reprogram the pll, change the operating channel, and wait for the operating channel center frequency to settle within ?0khz of the nominal (final) channel frequency. ac electrical characteristics?ystem timing (MAX2822 ev kit: v cc = +2.7v to +3.0v, f rf and f lo = 2400mhz to 2499mhz, f osc = 22mhz or 44mhz, shdnb = v ih , csb = v ih , r bias = 12k ? , i cp = +2ma, bw pll = 45khz, registers set to default power-up settings, t a = +25?, unless otherwise noted. typical values are for v cc = +2.7v, f lo = 2437mhz, f osc = 22mhz, unless otherwise noted.) (note 2) parameter conditions min typ max units channel-switching time f lo = 2400mhz ? 2499mhz, f lo settles to ?0khz (note 11) 150 200 ? rx to tx, f lo settles to within ?0khz, relative to the rising edge of tx_on 5 rx/tx turnaround time tx to rx, f lo settles to within ?0khz, relative to the rising edge of rx_on 10 ? standby-to-receive mode standby to rx, f lo settles to within ?0khz, relative to the rising edge of rx_on 10 ? standby-to-transmit mode standby to tx, f lo settles to within ?0khz, relative to the rising edge of tx_on 5s ac electrical characteristics?erial interface timing (MAX2822 ev kit: v cc = +2.7v to +3.0v, registers set to default power-up settings, t a = +25?, unless otherwise noted.) (note 2) parameter conditions min typ max units serial interface timing (see figure 1) t cso sclk rising edge to csb falling edge wait time 5 ns t css falling edge of csb to rising edge of first sclk time 5 ns t ds data-to-serial clock setup time 5 ns t dh data-to-clock hold time 10 ns t ch serial clock pulse-width high 10 ns t cl clock pulse-width low 10 ns t csh last sclk rising edge to rising edge of csb 5 ns t csw csb high pulse width 10 ns t cs1 time between the rising edge of csb and the next rising edge of sclk 5ns f clk clock frequency 50 mhz
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch 8 _______________________________________________________________________________________ typical operating characteristics (MAX2822 ev kit, v cc = +2.7v, f bb = 1mhz, f lo = 2437mhz, receive baseband outputs = 500mv p-p , transmit baseband inputs = 400mv p-p , icp = +2ma, bwpll = 45khz, differential rf input/output matched to 50 ? through a balun, baseband input biased at +1.2v, registers set to default power-up settings, t a = +25?, unless otherwise noted.) supply current vs. temperature MAX2822 toc01 temperature ( c) rx and stby i cc (ma) tx i cc (ma) 50 40 20 30 -20 -10 0 10 -30 10 20 30 40 50 60 70 80 90 100 0 160 170 180 190 200 210 220 230 240 250 260 -40 60 80 70 90 rx, lna low gain tx (p out = +17dbm) stby rx, lna high gain supply current vs. supply voltage MAX2822 toc02 v cc (v) rx and stby i cc (ma) tx i cc (ma) 2.95 3.00 2.80 2.85 2.90 2.75 10 20 30 40 50 60 70 80 90 100 0 160 170 180 190 200 210 220 230 240 250 260 2.70 rx, lna high gain tx, fixed, p out = +17dbm stby rx, lna low gain supply current vs. tx output power MAX2822 toc03 output power (dbm) i cc (ma) 18 16 -2 0 2 6 8 10 12 4 14 100 120 140 160 180 200 220 240 80 -4 20 +17dbm application +12dbm application +3dbm application traces end at linearity limits (-30dbc/-50dbc) receiver gain vs. gain-control voltage MAX2822 toc04 v rx_agc (v) receiver gain (db) 2.0 1.8 1.4 1.6 0.4 0.6 0.8 1.0 1.2 0.2 10 20 30 40 50 60 70 80 90 100 110 0 0 v out = 500mv p-p f bb = 1mhz f lo = 2437mhz lna low gain lna high gain receiver voltage gain vs. frequency MAX2822 toc05 frequency (mhz) rx gain, high-gain lna (db) 5 10 15 20 25 30 35 40 0 2400 2500 2480 2460 2440 2420 low-gain lna high-gain lna v rx_agc = 2.0v receiver noise figure vs. gain MAX2822 toc06 rx gain (db) noise figure (db) 100 90 70 80 20 30 40 50 60 10 5 10 15 20 25 30 35 40 45 50 0 0110 high-gain lna low-gain lna f bb = 2.25mhz f lo = 2437mhz receiver blocker rejection vs. rf frequency MAX2822 toc07 rf frequency (mhz) interferer level (dbm) 2200 2000 1800 1600 1400 1200 1000 -50 -40 -30 -20 -10 0 10 -60 800 2400 2lo/3 lo/2 gain = 80db p int (max) for snr degraded to 10db (per = 8%) lo/3 receiver blocker rejection vs. carrier offset MAX2822 toc08 offset from carrier (mhz) interferer level (dbm) 45 40 15 20 25 30 35 -70 -60 -50 -40 -30 -20 -10 0 -80 10 50 gain = 80db p int (max) for snr degraded to 10db (per = 8%) MAX2822 toc09 frequency (khz) normalized response (db) 100 10 -80 -70 -60 -50 -40 -30 -20 -10 0 10 -90 1 1000 receiver filter response (1khz to 1mhz) rx_1k = v ih rx_1k = v il
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch _______________________________________________________________________________________ 9 MAX2822 toc10 frequency (mhz) normalized response (db) 10 -80 -70 -60 -50 -40 -30 -20 -10 0 10 -90 1100 f -3db = 8.5mhz f -3db = 7.5mhz receiver filter response (1mhz to 100mhz) receiver leakage spectrum max2811 toc11 frequency (ghz) leakage power (dbm) 7 6 45 23 1 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 -110 08 p out is 50 ? referred (single ended) rbw = 100khz f lo = 2437mhz lna high gain receiver baseband output spectrum (single tone) MAX2822 toc12 bb frequency (mhz) baseband output power (dbm) 40 51015 2530 20 35 -70 -60 -50 -40 -30 -20 -10 0 -80 0 p out is 50 ? referred (single ended) rbw = 100khz f lo = 2437mhz lna high gain receiver baseband output spectrum (modulated) MAX2822 toc13 bb frequency (mhz) baseband output power (dbm) 40 51015 2530 20 35 -70 -60 -50 -40 -30 -20 -10 0 -80 0 p out is 50 ? referred (single ended) rx gain = 50db rbw = 100khz f lo = 2437mhz lna high gain signal applied no signal applied transmitter output power vs. supply voltage MAX2822 toc14 v cc (v) transmitter output power (dbm) 2.95 2.90 2.75 2.88 2.85 13 14 15 16 17 18 19 20 12 2.70 3.00 t a = +85 c t a = +25 c t a = -40 c v in = 400mv p-p 802.11b signal v tx_gc for +17.0dbm output power at 2437mhz, +25 c transmitter output power vs. frequency MAX2822 toc15 rf frequency (mhz) transmitter output power (dbm) 2480 2460 2440 2420 14.5 15.0 15.5 16.0 16.5 17.0 17.5 18.0 18.5 19.0 14.0 2400 2500 t a = +85 c t a = +25 c t a = -40 c v in = 400mv p-p 802.11b signal v tx_gc for +17.0dbm output power at 2437mhz, +25 c acpr vs. output power MAX2822 toc16 output power (dbm) acpr, adjacent (dbc) 18 16 2 4 6 10 12 8 14 -40 -38 -36 -34 -32 -30 -28 -26 -42 acpr, alternate (dbc) -60 -58 -56 -54 -52 -50 -48 -46 -62 020 +3dbm app. alt adj alt alt adj adj 802.11b spec limits +17dbm app. +12dbm app. transmitter output spectrum MAX2822 toc17 frequency (ghz) power (dbm) 7 6 45 23 1 -70 -60 -50 -40 -30 -20 -10 0 10 20 -80 08 f lo = 2437mhz f bb = 1mhz rbw = 100khz transmitter gain vs. gain-control voltage MAX2822 toc18 v tx_gc (v) normalized transmitter gain (db) 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 -25 -20 -15 -10 -5 0 5 -30 0 2.0 t a = -40 c t a = +25 c t a = +85 c normalized to +25 c v tx_gc = 0v typical operating characteristics (continued) (MAX2822 ev kit, v cc = +2.7v, f bb = 1mhz, f lo = 2437mhz, receive baseband outputs = 500mv p-p , transmit baseband inputs = 400mv p-p , icp = +2ma, bwpll = 45khz, differential rf input/output matched to 50 ? through a balun, baseband input biased at +1.2v, registers set to default power-up settings, t a = +25?, unless otherwise noted.)
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch 10 ______________________________________________________________________________________ transmitter baseband filter response MAX2822 toc19 baseband frequency (mhz) normalized response (db) 45 40 30 35 10 15 20 25 5 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 -50 050 normalized to 1mhz lo frequency vs. tuning voltage MAX2822 toc20 v tune (v) lo frequency (ghz) 2.0 1.5 1.0 0.5 2.25 2.30 2.35 2.40 2.45 2.50 2.55 2.60 2.65 2.20 0 2.5 +25 c +85 c -40 c synthesizer closed-loop phase noise MAX2822 toc21 f offset (khz) phase noise (dbc/hz) 100 10 -110 -100 -90 -80 -70 -60 -50 -40 -120 1 1000 f osc = 2437mhz i cp = 2ma pll bw = 45khz ttl integrated phase noise = 2.0 rms vco/pll setting time MAX2822 toc22 time ( s) frequency error (khz) -40 -30 -20 -10 0 10 20 30 40 50 -50 360 320 240 280 80 120 160 200 40 0400 bw loop = 45khz f lo = 2499mhz to 2400mhz rx/tx turnaround time MAX2822 toc23 time ( s) frequency error (khz) 18 16 12 14 46810 2 -40 -30 -20 -10 0 10 20 30 40 50 -50 020 triggered on rising edge of txon synthesizer settings do not change pa power-detector output voltage vs. output power MAX2822 toc24 output power (dbm) detector output voltage (v) 18 16 12 14 4 6 8 10 2 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0 020 modulated baseband input signal typical operating characteristics (continued) (MAX2822 ev kit, v cc = +2.7v, f bb = 1mhz, f lo = 2437mhz, receive baseband outputs = 500mv p-p , transmit baseband inputs = 400mv p-p , icp = +2ma, bwpll = 45khz, differential rf input/output matched to 50 ? through a balun, baseband input biased at +1.2v, registers set to default power-up settings, t a = +25?, unless otherwise noted.)
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch ______________________________________________________________________________________ 11 bias MAX2822 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 vcc_lna v ref rf_gain vcc_ref gnd rfp rfn pwr_det gnd vcc_pa vcc_drvr tx_gc vcc_tmx tx_bbin tx_bbip tx_bbqp tx_bbqn vcc_txf gnd_dig vcc_dig pwr_det roscp roscn din shdnb vcc_rxf vcc_lo vcc_vco byp tune gnd_vco gnd_cp cp_out vcc_cp csb sclk rx_agc tx_on vcc_rmx rx_on vcc_buf rx_bbip rx_bbin rx_bbqn rx_bbqp rx_1k dout n.c. programming and mode control 90 0 90 0 integer-n synthesizer serial interface vos comp input match t/r switch output match pwr det pin configuration/functional diagram
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch 12 ______________________________________________________________________________________ pin description pin name function 1 vcc_lna supply voltage connection for lna. bypass with a capacitor as close to the pin as possible. do not share the bypass capacitor ground vias with other branches. 2v ref voltage reference output for baseband ic. requires external rf bypass to gnd. 3 rf_gain lna gain-select logic input. logic high for lna high-gain mode, logic low for lna low-gain mode. 4 vcc_ref supply voltage for bias circuitry and autotuner. bypass with a capacitor as close to the pin as possible. do not share the bypass capacitor ground vias with other branches. 5, 8 gnd ground 6 rfp rf balanced i/o port (positive). on-chip matched for 100 ? balanced. 7 rfn rf balanced i/o port (negative). on-chip matched for 100 ? balanced. 9 vcc_pa supply voltage connection for power amplifier. requires external rf bypass to gnd. 10 vcc_drvr supply voltage connection for pa driver. requires external rf bypass to gnd. 11 bias precision bias resistor pin. connect a 12k ? precision resistor ( 2%) to gnd. 12 tx_gc transmit gain-control input. analog high-impedance input. connect directly to baseband ic dac output. see figure 3 for transmitter gain vs. gain-control voltage. 13 vcc_tmx supply voltage for transmit mixer and vga. bypass with a capacitor as close to the pin as possible. do not share the bypass capacitor ground vias with other branches. 14 tx_bbin transmit negative in-phase baseband input. analog high-impedance differential input. connect directly to baseband ic dac voltage output. requires a 1.2v common-mode voltage. 15 tx_bbip transmit positive in-phase baseband input. analog high-impedance differential input. connect directly to baseband ic dac voltage output. requires a 1.2v common-mode voltage. 16 tx_bbqp transmit positive quadrature baseband input. analog high-impedance differential input. connect directly to baseband ic dac voltage output. requires a 1.2v common-mode voltage. 17 tx_bbqn transmit negative quadrature baseband input. analog high-impedance differential input. connect directly to baseband ic dac voltage output. requires a 1.2v common-mode voltage. 18 vcc_txf supply voltage for transmit baseband filter. bypass with capacitor as close to the pin as possible. do not share the bypass capacitor ground vias with other branches. 19 gnd_dig digital ground 20 vcc_dig supply voltage for digital circuitry. bypass with capacitor as close to the pin as possible. do not share the bypass capacitor ground vias with other branches. 21 pwr_det transmitter power-detector output 22 roscp reference oscillator positive input. analog high-impedance differential input. dc-coupled. requires external ac-coupling. connect an external reference oscillator to this analog input. 23 roscn reference oscillator negative input. analog high-impedance differential input. dc-coupled. requires external ac-coupling. bypass this analog input to ground with capacitor for single-ended operation. 24 din 3-wire serial interface data input. digital high-impedance input. connect directly to baseband ic serial interface cmos output (spi/qspi/microwire compatible). 25 sclk 3-wire serial interface clock input. digital high-impedance input. connect this digital input directly to baseband ic serial interface cmos output (spi/qspi/microwire compatible). spi and qspi are trademarks of motorola, inc. microwire is a trademark of national semiconductor corp.
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch ______________________________________________________________________________________ 13 pin description (continued) pin name function 26 csb 3-wire serial interface enable input. digital high-impedance input. connect directly to baseband ic serial interface cmos output (spi/qspi/microwire compatible). 27 vcc_cp supply voltage for pll charge pump. bypass with capacitor as close to the pin as possible. do not share the bypass capacitor ground vias with other branches. 28 cp_out pll charge-pump output. analog high-impedance output. current source. connect directly to the pll loop filter input. 29 gnd_cp pll charge-pump ground. connect to pc board ground plane. 30 gnd_vco vco ground. connect to pc board ground plane. 31 tune vco frequency tuning input. analog high-impedance voltage input. connect directly to the pll loop filter output. 32 byp vco bias bypass. bypass with a 2000pf capacitor to ground. 33 vcc_vco s up p l y v ol tag e for v c o. byp ass w i th cap aci tor as cl ose to the p i n as p ossi b l e. d o not shar e the b yp ass cap aci tor g r ound vi as w i th other b r anches. im p o r t a n t n o t e : op er ate fr om sep ar ate r eg ul ated sup p l y vol tag e. 34 vcc_lo supply voltage for vco, lo buffers, and lo quadrature circuitry. bypass with capacitor as close to the pin as possible. do not share the bypass capacitor ground vias with other branches. 35 vcc_rxf supply voltage for receiver baseband filter. bypass with capacitor as close to the pin as possible. do not share the bypass capacitor ground vias with other branches. 36 shdnb acti ve- low s hutd ow n inp ut. d i g i tal hi g h- i m p ed ance c m o s i np ut. c onnect d i r ectl y to b aseb and ic m od e- contr ol c m os outp ut. log i c l ow to d i sab l e al l d evi ce functi ons. log i c hi g h to enab l e nor m al chi p op er ati on. 37 dout serial interface data output . digital cmos output. optional connection. 38 rx_1k receiver 1khz highpass bandwidth control. digital cmos input. connect directly to baseband ic cmos output. controls receiver baseband highpass -3db corner frequency; logic low for 10khz, logic high for 1khz. see the applications information section for proper use of this function. 39 rx_bbqp receive positive quadrature baseband output. analog low-impedance differential buffer output. connect output directly to baseband adc input. internally biased to 1.2v common-mode voltage and can drive loads up to 5k ? || 5pf. 40 rx_bbqn receive negative quadrature baseband output. analog low-impedance differential buffer output. connect output directly to baseband adc input. internally biased to 1.2v common-mode voltage and can drive loads up to 5k ? || 5pf. 41 rx_bbin receive negative in-phase baseband output. analog low-impedance differential buffer output. connect output directly to baseband adc input. internally biased to 1.2v common-mode voltage and can drive loads up to 5k ? || 5pf. 42 rx_bbip receive positive in-phase baseband output. analog low-impedance differential buffer output. connect output directly to baseband adc input. internally biased to 1.2v and can drive loads up to 5k ? || 5pf. 43 n.c. no connection. make no connections to this pin. 44 vcc_buf supply voltage for receiver baseband buffer. bypass with capacitor as close to the pin as possible. do not share the bypass capacitor ground vias with other branches.
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch 14 ______________________________________________________________________________________ detailed description operating modes the MAX2822 has four primary modes of operation: shutdown, standby, receive active, and transmit active. the modes are controlled by the digital inputs shdnb, tx_on, and rx_on. table 1 shows the operating mode vs. the digital mode-control inputs. shutdown mode shutdown mode is enabled by driving shdnb low. in shutdown mode, all circuit blocks are powered down, except for the serial interface circuitry. while the device is in shutdown, the serial interface registers can still be loaded by applying v cc to the digital supply voltage (vcc_dig). all previously programmed register values are preserved during the shutdown mode, as long as vcc_dig is applied. standby mode standby mode is achieved by driving shdnb high, and rx_on and tx_on low. in standby mode, the pll, vco, lo generation circuitry, and filter autotuner are powered on by default. the standby mode is intended to provide time for the slower-settling circuitry (pll and autotuner) to turn on and settle to the correct frequency before making rx or tx active. the 3-wire serial inter- face is active and can load register values at any time. refer to the serial interface specifications for details. receive mode receive mode is enabled by driving shdnb high, rx_on high, and tx_on low. in receive mode, all receive circuit blocks are powered on and all vco, pll, and autotuner circuits are powered on. none of the transmit path blocks are active in this mode. although the receiver blocks turn on quickly, the dc offset nulling requires ~10? to settle. the receiver signal path is ready ~10? after a low-to-high transition on rx_on. transmit mode transmit mode is enabled by driving the digital inputs shdnb high, rx_on low, and tx_on high. in transmit mode, all transmit circuit blocks are powered on and all vco, pll, and autotuner circuits are powered on. none of the receive path blocks are active in this mode. although the transmitter blocks turn on quickly, the baseband dc offset calibration requires ~2.2? to complete. in addition, the tx driver amplifier is ramped from the low-gain state (minimum rf output) to high- gain state (peak rf output) over the next 1? to 2?. also, the lo takes a few microseconds after tx_on rises to resettle. the transmit signal path is ready ~5? after a low-to-high transition on tx_on. pin description (continued) pin name function 45 rx_on receiver-on control input. digital cmos input. connect to baseband ic mode-control cmos output. 46 vcc_rmx supply voltage for receiver downconverter. bypass with capacitor as close to the pin as possible. do not share the bypass capacitor ground vias with other branches. 47 tx_on transmitter-on control input. digital cmos input. connect directly to baseband ic mode-control cmos output. 48 rx_agc receive agc control. analog high-impedance input. connect directly to baseband ic dac voltage output. see figure 2 for gain vs. v rx_agc . exposed paddle gnd dc and ac ground return for ic. connect to pc board ground plane using multiple vias. mode-control inputs circuit block states operating mode shdnb tx_on rx_on rx_path tx_path pll/vco/lo gen shutdown 0 x x off off off standby 1 0 0 off off on receive 1 0 1 on off on transmit 1 1 0 off on on not allowed 1 1 1 table 1. operating mode truth table
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch ______________________________________________________________________________________ 15 programmable registers the MAX2822 contains programmable registers to con- trol various modes of operation for the major circuit blocks. the registers can be programmed through the 3-wire spi/qspi/microwire-compatible serial port. the MAX2822 includes five programmable registers: 1) block-enable register 2) synthesizer register 3) channel frequency register 4) receiver settings register 5) transmitter settings register each register consists of 16 bits. the four most signifi- cant bits (msbs) are the register? address. the twelve least significant bits (lsbs) are used for register data. table 2 summarizes the register configuration. a detailed description of each register is provided in tables 4?. data bits are shifted in the msb first. the data sent to the MAX2822, in 16-bit words, is framed by csb. when csb is low, the clock is active and data is shifted with the rising edge of the clock. when csb transitions to high, the shift register is latched into the register select- ed by the contents of the address bits. only the last 16 bits shifted into the MAX2822 are retained in the shift register. no check is made on the number of clock pulses. figure 1 documents the serial interface timing for the MAX2822. power-up default states the MAX2822 provides power-up loading of default states for each of the registers. the states are loaded on a vcc_dig supply voltage transition from 0v to v cc . the default values are retained until repro- grammed through the serial interface or the power-sup- ply voltage is taken to 0v. the default state of each register is described in table 3. note: putting the ic in shutdown mode does not change the contents of the programming registers. block-enable register the block-enable register permits individual control of the enable state for each major circuit block in the MAX2822. the actual enable condition of the circuit block is a logical function of the block-enable bit setting and other control input states. table 4 documents the logical definition of state for each major circuit block. synthesizer register the synthesizer register (synth) controls the reference frequency divider and charge-pump current of the pll. see table 5 for a description of the bit settings. channel frequency register the channel frequency register (channel) sets the rf carrier frequency for the MAX2822. the channel is pro- grammed as a number from 0 to 99. the actual fre- quency is 2400 + channel in mhz. the default setting is 37 for 2437mhz. see table 6 for a description of the bit settings. csb sclk t css din dout t cso t csw t csh t cl t cs1 t tr bit 16 bit 15 bit 16 bit 15 bit 14 bit 8 bit 7 bit 6 bit 2 bit 1 bit 14 bit 8 bit 7 bit 6 bit 2 bit 1 t ch t dh t do t dv t ds figure 1. MAX2822 serial interface timing diagram
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch 16 ______________________________________________________________________________________ 4 address bits 12 data bits a3a2a1a0d11d10d9d8d7d6d5d4d3d2d1 d0 register name msb151413121110 98765432 lsb enable 0001 e11 e10 e9 e8 e7 e6 e5 e4 e3 e2 e1 e0 synth 0010 xxxx010 0000 r0 channel 0011 xxxxx cf6 cf5 cf4 cf3 cf2 cf1 cf0 receive 0100 2c2 2c1 2c0 1c2 1c1 1c0 dl1 dl0 sf bw2 bw1 bw0 transmit 0101 xxxxx de dr1 dr0 pa3 pa2 pa1 pa0 table 2. programming register definition summary register address default function enable 0001 0000 0001 1110 block-enable control settings (e) synth 0010 0000 0100 0000 synthesizer settings: ? reference frequency (r) channel 0011 0000 0010 0101 channel frequency settings (cf) receive 0100 1111 1101 0010 receiver settings: ? -3db lowpass filter bandwidth (bw) ? detector midpoint level (dl) transmit 0101 0000 0010 1101 transmit settings: ? pa bias (pa) ? pa driver bias (d) ? pa driver enable (de) table 3. register power-up defaults states receiver settings register the receiver settings register (receive) controls the receive filter -3db corner frequency and vga dc offset nulling parameters. the defaults are intended to pro- vide proper operation. however, the filter frequency and detector can be modified if desired. do not repro- gram vga dc offset nulling parameters. these settings were optimized during development. see table 7 for a description of the bit settings. transmitter settings register the transmitter settings register (transmit) provides a 6-bit digital control of the pa bias and 1-bit enable for the transmit power detector. bits d0:d3 control the pa output stage bias current (0000 lowest, 1111 highest) and pa driver stage bias current (00 lowest, 11 high- est). the appropriate values vs. target output power are given in table 9. the detector enable bit allows inde- pendent turn-on of the detector for testing purposes. x = don? care.
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch ______________________________________________________________________________________ 17 address data bit content default description d11:d8 x 0000 reserved d7 0 must be 0 for proper operation d6 1 must be 1 for proper operation 0 0 1 0 d5:d0 r(5:0) 000000 reference frequency divider: ? 000000 = 22mhz ? 000001 = 44mhz table 5. synthesizer settings register (synth) address data bit content default description d11:d7 x 00000 reserved 0 0 1 1 d6:d0 cf(6:0) 0100101 c hannel fr eq uency s el ect: f lo = ( 2400 + c f( 6:0) ) m h z ? 0000000 = 2400mhz ? 0000001 = 2401mhz ? ? 1100010 = 2498mhz ? 1100011 = 2499mhz table 6. channel frequency register (channel) address data bit content default description and logical definition d11 e(11) 0 reserved d10 e(10) 0 pa bias-control enable (pab_en) pab_en = shdnb ?(e(10) + tx_on) d9 e(9) 0 transmit baseband filters enable (txflt_en) txflt_en = shdnb ?(e(9) + tx_on) d8 e(8) 0 tx upconverter + vga + driver amp enable (txuvd_en) txuvd_en = shdnb ?(e(8) + tx_on) d7 e(7) 0 reserved d6 e(6) 0 rx downconverter + filters + agc amps enable (rxdfa_en) rxdfa_en = shdnb ?(e(6) + rx_on) d5 e(5) 0 receive lna enable (rxlna_en) rxlna_en = shdnb ?(e(5) + rx_on ) d4 e(4) 1 autotuner enable (at_en) at_en = shdnb ?(e(4) + rx_on + tx_on) d3 e(3) 1 pll charge-pump enable (cp_en) cp_en = shdnb ?e(3) d2 e(2) 1 pll enable (pll_en) pll_en = shdnb ?e(2) d1 e(1) 1 vco enable (vco_en) vco_en = shdnb ?e(1) 0 0 0 1 d0 e(0) 0 reserved table 4. block-enable register (enable)
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch 18 ______________________________________________________________________________________ address data bit content default description d11:d4 11111111 must be 11111111 for proper operation d3 0 must be 0 for proper operation 0 1 0 0 d2:d0 bw(2:0) 010 receive filter -3db frequency select (frequencies are approximate): ? 000 = 8.5mhz ? 001 = 8.0mhz ? 010 = 7.5mhz ? 011 = 7.0mhz ? 100 = 6.5mhz ? 101 = 6.0mhz table 7. receiver settings register (receive) applications information rf i/o and tx/rx switching the MAX2822 completely integrates the power amplifi- er, low-noise amplifier, transmit/receive (tx/rx) switch, as well as all matching components, to allow direct connection to the antenna through a balun or combina- tion balun/filter. this single rf interface (rfp and rfn) is internally matched to form a 100 ? balanced port?o additional components are required to impedance- match the i/o. most applications employ a 100 ? bal- anced to 50 ? single-ended rf bandpass filter between the rf port and the antenna. receive path lna given the lna input is internally matched to 100 ? dif- ferential, it is important that the differential pair from rfp/rfn to the rf bpf be an identical pair of transmis- sion lines to present a 100 ? differential impedance to the balun. identical line layout on the differential input traces is important in maintaining good ip2 perfor- mance and rf common-mode noise rejection. the MAX2822 has two lna gain modes that are digitally controlled by the logic signal applied to rf_gain. rf_gain high enables the high-gain mode, and rf_gain low enables the low-gain mode. the lna gain step is nominally 32db. in most applications, rf_gain is connected directly to a cmos output of the baseband ic, and the baseband ic controls the state of the lna gain based on the detected signal amplitude. address data bit content default description d11:d7 x x reserved d6 de 0 transmit power-detector enable d5:d4 d(1:0) 10 pa predriver bias: ? 11 = highest predriver bias ? ? 00 = lowest predriver bias 0 1 0 1 d3:d0 pa(3:0) 1101 pa bias select: ? 1111 = highest pa bias ? ? 0000 = lowest pa bias table 8. transmit settings register (transmit)
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch ______________________________________________________________________________________ 19 receiver baseband lowpass filtering the MAX2822 on-chip receive lowpass filters provide the steep filtering necessary to attenuate the out-of- band (> 11mhz) interfering signals to sufficiently low lev- els to preserve receiver sensitivity. the filter frequency response is precisely controlled on-chip and does not require user adjustment. however, a provision is made to permit the -3db corner frequency and entire response to be slightly shifted up or down in frequency. this is intended to offer some flexibility in trading off adjacent channel rejection vs. passband distortion. the filter -3db frequency is programmed through the serial interface. the specific bit setting vs. -3db frequency is shown in table 7. the typical receive baseband filter gain vs. fre- quency profile is shown in the typical operating characteristics . default filter settings are optimal (-3db corner at 7.5mhz)?his provides the best trade-off between noise filtering and baseband distortion to obtain best receive sensitivity. no user adjustment is required. receive gain control the MAX2822 receive path gain is varied through an external voltage applied to the pin rx_agc. maximum gain is at v rx_agc = 0v and minimum gain is at v rx_agc = 2v. the rx_agc input is a high-impedance analog input designed for direct connection to the rx_agc dac output of the baseband ic. the gain- control range, which is continuously variable, is typical- ly 70db. the gain-control characteristic is shown in the typical operating characteristics receiver voltage gain vs. gain-control voltage graph and again as a full-page plot in figure 2. some local noise filtering through a simple rc network at the input is permissible. however, the time constant of this network should be kept sufficiently low to not limit the desired response time of the rx gain-control function. receiver baseband amplifier outputs the MAX2822 receiver baseband outputs (rx_bbip, rx_bbin, rx_bbqp, and rx_bbqn) are differential low-impedance buffer outputs. the outputs are designed to be directly connected (dc-coupled) to the in-phase (i) and quadrature-phase (q) adc inputs of the baseband ic. the rx i/q outputs are internally biased to +1.2v common-mode voltage. the outputs are capable of driving loads up to 5k ? || 5pf with the full bandwidth baseband signals at a differential ampli- tude of 500mv p-p . proper board layout is essential to maintain good bal- ance between i/q traces. this provides good quadra- ture phase accuracy. transmit path transmitter baseband inputs the MAX2822 transmitter baseband inputs (tx_bbip, tx_bbin, tx_bbqp, and tx_bbqn) are high-imped- ance differential analog inputs. the inputs are designed to be directly connected (dc-coupled) to the in-phase (i) and quadrature-phase (q) dac outputs of the baseband ic. the inputs must be externally biased to +1.2v common-mode voltage. typically, the dac outputs are current outputs with external resistor loads to ground. i and q are driven by a 400mv p-p (nominal) differential baseband signal. proper board layout is essential to maintain good bal- ance between i/q traces. this provides good quadra- ture phase accuracy by maintaining equal parasitic capacitance on the lines. in addition, it is important not to expose the tx i/q circuit board traces going from the digital baseband ic to the MAX2822. the lines should be shielded on an inner layer to prevent coupling of rf to these tx i/q inputs and possible envelope demodu- lation of the rf signal. transmit path baseband lowpass filtering the MAX2822 on-chip transmit lowpass filters provide the filtering necessary to attenuate the unwanted higher- frequency spurious signal content that arises from the dac clock feedthrough and sampling images. in addi- tion, the filter provides additional attenuation of the sec- ond sidelobe of signal spectrum. the filter frequency response is set on-chip. no user adjustment or program- ming is required. the typical gain vs. frequency profile is shown in the typical operating characteristics . transmitter dc offset calibration in a zero-if system, the dc offset of the tx baseband signal path must be reduced to as near zero as possi- ble to minimize lo leakage at the rf output. given that the amplifier stages, baseband filters, and tx dac pos- sess some finite dc offset that is too large for the required lo leakage specification, it is necessary to null the dc offset. the MAX2822 accomplishes this through an on-chip calibration sequence. during this sequence, the net tx baseband signal path offsets are sampled and cancelled in the baseband amplifiers. this calibration occurs in the first ~2.2? after tx_on is taken high. the calibration corrects for any dc offset from the dac, but this dc offset must not change after this cal sequence. be sure the dac outputs are set to zero state before taking tx_on high.
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch 20 ______________________________________________________________________________________ receiver gain vs. gain-control voltage 110 100 90 80 70 60 50 40 30 20 10 0 receiver gain (db) 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 v rx_agc (v) lna low gain lna high gain v out = 500mv p-p f bb = 1mhz f lo = 2437mhz figure 2. receiver gain vs. v rx_agc
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch ______________________________________________________________________________________ 21 transmitter gain vs. gain-control voltage 5 0 -5 -10 -15 -20 -25 -30 normalized transmitter gain (db) 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 v tx_gc (v) normalized to +25 c v tx_gc = 0v t a = +85 c t a = +25 c t a = -40 c figure 3. transmitter gain vs. v tx_gc
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch 22 ______________________________________________________________________________________ the dc offset circuitry uses a sample-and-hold tech- nique to accomplish this dc offset nulling. over time (many seconds), the sample-and-hold storage cap slowly discharges, causing the dc value at the tx bb to slowly increase, and the lo level in the rf output to slowly increase. this can be seen on the bench during evaluation, when the transceiver is left in tx mode for more than 30 to 60 seconds. even under worst-case conditions, however, the dc null value changes very lit- tle during the longest 802.11b tx burst of 20ms?o suppression in 802.11b applications always remains around the -30dbc typical level specified in the electrical characteristics table. transmit gain control the transmit gain-control input provides a direct analog control over the transmit path gain. the transmit gain of the MAX2822 is controlled by an external voltage at pin tx_gc. the typical gain-control characteristic is pro- vided in the typical operating characteristics transmitter gain control vs. gain-control voltage graph and again as a full-page plot in figure 3. the input is a high-impedance analog input designed to directly connect to the dac output of the baseband ic. some local noise filtering through a simple rc network at the input is permissible. however, the time constant of this network should be kept sufficiently low so the desired response time of the tx gain-control function is not limited. during the tx turn-on sequence, internally the gain is set at the minimum while the tx baseband offset cali- bration is taking place. the rf output is effectively blanked for the first 2.2? after tx_on is taken high. after 2.2?, the blanking is released, and the gain-con- trol amplifier ramps to the gain set by the external volt- age applied to the tx_gc input. power amplifier the MAX2822 provides two programmable analog cur- rent sources for internally biasing the on-chip rf power amplifier and the pa predriver. the pa predriver current is controlled by two bits in the transmit control register (transmit:d5, d4). the value of the pa bias current is determined by four bits (transmit:d3?0). this pro- grammability permits optimizing of the power amplifier idle current based on the output power level of the pa. see table 8 for a description of the transmit control bits, and the corresponding pa predriver and pa bias currents. these two bias current settings significantly affect both efficiency and linearity. they should be cho- sen based on the target output power for the application. table 9 shows the recommended register settings for three target output powers. synthesizer channel frequency and reference frequency the synthesizer/pll channel frequency and reference settings establish the divider/counter settings in the integer-n synthesizer of the MAX2822. both the chan- nel frequency and reference divider are programmable through the serial interface. the channel frequency is programmed as a channel number 0 to 99 to set the carrier frequency to 2400mhz to 2499mhz (lo fre- quency = channel + 2400). the reference divider is programmable to allow for 22mhz or 44mhz reference oscillators. these settings are intended to cover only the required 802.11b channel spacing and the two typi- cal crystal oscillator options used in the radios. reference oscillator input the reference oscillator inputs roscp and roscn are high-impedance analog inputs. they are designed to be connected to the reference oscillator output through a coupling capacitor. the input amplitude can range from 200mv p-p to 500mv p-p ; therefore, in the case of a reference oscillator with a cmos output, the signal must be attenuated before being applied to the rosc inputs. the signal can be attenuated with a resistor- or capacitor-divider network. loop filter the pll uses a classical charge pump into an external loop filter (c-rc) in which the filter output connects to the voltage tuning input of the vco. this simple third- order lowpass loop filter closes the loop around the synthesizer. the typical application circuit shows the loop filter elements around the MAX2822. the capacitor and resistor values are set to provide the loop band- width required to achieve the desired lock time while also maintaining loop stability. refer to the MAX2822 target output power (dbm) pa driver bias setting (transmit: d5, d4) pa bias setting (transmit: d3?0) +3 00 0011 +12 01 0111 +17 10 1101 table 9. suggested pa and pa driver bias current settings
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch ______________________________________________________________________________________ 23 ev kit schematic for component values. a 45khz loop bandwidth is recommended to ensure the loop settles quickly enough to achieve 5? tx turnaround time and 10? rx turnaround time. this is the loop filter on the ev kit. narrowing the loop bandwidth increases the set- tling time and results in unacceptable tx/rx turnaround time performance. pc board layout careful pc board layout is mandatory for any radio to meet its specifications. general rules for rf layout apply: keep differential pairs close together, keep all rf traces as short as possible, keep rf bypassing as close to the ic as possible, provide a separate filtered supply line from a large central filter capacitor for each v cc pin (star supply bypassing topology), and have each ground pin use its own via to the ground plane do not connect ground pins directly to the ground slug on the ic. in addition, below is a list of more specific layout issues to keep in mind for the MAX2822: ? rf i/o: keep rf differential pair from the ic to the balun/filter electrically and environmentally symmet- rical. that is, shape the top layer ground equally on either side of the traces, and place the rf decou- pling caps for the nearby rf supplies in a symmet- rical fashion. this minimizes second-order distortion of the signal on the differential pair. ? rbias: this external resistor sets the bias for the rf section of the transceiver, and this pin is connected directly to the bias section. the network connected to this port must look high impedance to rf, so do not place any rf filtering here?se only a 1% or 2% 12k ? resistor, as specified in the typical application circuit . place this resistor as close to the ic as possible on the top layer of the pc board. ? gnd_dig: use a via to connect this digital ground to the main pc board ground plane. the small inductance of the trace and the via helps to filter out the noise from the digital interface, and helps keep the main system ground clean. it is very important not to connect this directly to the ic ground slug, or directly to any other ground pins, which allows noise from the digital section to couple into sensi- tive sections of the radio. ? pll section (cp_out, gnd_cp, gnd_vco, tune): the capacitors directly at the output of the pll? charge pump need to have their ground return connected as close to the charge pump? ground as possible, and as isolated from the vco? ground as possible. create separate vias to the ground plane for each of the two grounds (gnd_cp and gnd_vco). referring to the typical application circuit , connect the ground side of c30 and c52 to the ground path for gnd_cp, and con- nect the ground side of c31 to the ground path for gnd_vco. keeping the charge-pump return cur- rents from bouncing the vco? ground minimizes the lo comparison frequency spurs. ? byp: this bypass capacitor is directly connected to the vco bias circuitry?t is used to filter out noise within the loop bandwidth of the pll (about 50khz). the value for this capacitor is critical?e sure to use the 2000pf capacitor specified in the typical application circuit . keep this cap as close to the ic as possible, since noise pickup on this trace couples directly into the vco bias and degrade phase noise. supply and regulation the typical application circuit for the MAX2822 employs two low-dropout linear regulators (ldos)?ne supplies the internal vco, and the other supplies everything else (see the pin description table for details on supply pin names, numbers, and functions). supplying the vco from a dedicated ldo minimizes noise pickup by the vco that can degrade phase noise and produce spurs. the vco only draws 10ma, so power dissipation is not an issue. choose a small, low-noise, high-psrr ldo like the max8510. this ldo comes in a tiny 5-pin sc70 package and is available in many preset output voltages in the 2.7v to 3.0v range. having the vco and the rest of the ic supplied from different voltages is acceptable. therefore, if the MAX2822 main supply is 2.7v, but the application already has a low-noise, 3.0v supply available, simply run the vco from this 3.0v supply?here is no need for another dedicated 2.7v supply for the vco. switching power supplies should not be used to directly power any rf transceiver; the spurious content of their outputs often falls in the middle of the system? baseband spectrum (50khz to 11mhz). this can couple into the tx path and degrade the output spectrum, and can couple into the rx path and degrade sensitivity and ber. when laying out the supply lines for the ic, always use a star bypassing topology. have a large (10?) low- esr capacitor at the main supply connection point, and run dedicated traces to each of the supply pins (there are about ten in total). each supply pin should have a pair of smaller decoupling caps (10nf and 100pf work well). it is especially important to isolate the supplies for the lna bias (vcc_lna) and the rx baseband filter bias (vcc_buf). also be sure to use local rf decoupling on the logic lines. proper decoupling minimizes noise pickup and coupling.
MAX2822 chip information transistor count: 16,097 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch 24 ______________________________________________________________________________________ bias vcc_lna v ref rf_gain vcc_ref gnd to bbic rfp rfn gnd vcc_pa vcc_drvr tx_gc vcc_tmx tx_bbin tx_bbip tx_bbqp tx_bbqn vcc_txf gnd_dig vcc_dig pwr_det roscp roscn din shdnb vcc_rxf vcc_lo vcc_vco byp tune gnd_vco gnd_cp cp_out vcc_cp csb sclk loop filter rx_agc tx_on vcc_rmx rx_on vcc_buf rx_bbip rx_bbin rx_bbqn rx_bbqp rx_1k dout n.c. digital mode-control signals from/to baseband ic tx analog input signal from baseband ic reference oscillator input pa power-detector output rx analog output signal to baseband ic digital mode-control signals to/from baseband ic rx gain-control signals to/from baseband ic rf i/o to rf bpf and ant serial interface to baseband ic dac output from baseband ic dac output from baseband ic MAX2822 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 pwr_det programming and mode control 90 0 90 0 integer-n synthesizer serial interface vos comp input match t/r switch output match pwr det typical application circuit
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch ______________________________________________________________________________________ 25 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 .) 32, 44, 48l qfn.eps h 1 2 21-0092 package outline 32,44,48l qfn, 7x7x0.90 mm
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch 26 ______________________________________________________________________________________ package information (continued) (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 .) u h 2 2 21-0092 package outline, 32,44,48l qfn, 7x7x0.90 mm
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch ______________________________________________________________________________________ 27 package information (continued) (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 .) 32, 44, 48l qfn .eps proprietary information approval title: document control no. 21-0144 package outline 32, 44, 48l qfn thin, 7x7x0.8 mm 1 b rev. 2 e l e l a1 a a2 e/2 e d/2 d detail a d2/2 d2 b l k e2/2 e2 (ne-1) x e (nd-1) x e e c l c l c l c l k
MAX2822 2.4ghz 802.11b zero-if transceiver with integrated pa and tx/rx switch maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 28 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2003 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information (continued) (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 .) proprietary information document control no. approval title: b rev. 2 2 exposed pad variations 21-0144 package outline 32, 44, 48l qfn thin, 7x7x0.8 mm common dimensions ** note: t4877-1 is a custom 48l pkg. with 4 leads depopulated. total number of leads are 44.

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