general description the max1472 is a crystal-referenced phase-lockedloop (pll) vhf/uhf transmitter designed to transmit ook/ask data in the 300mhz to 450mhz frequency range. the max1472 supports data rates up to 100kbps, and adjustable output power to more than +10dbm into a 50 ? load. the crystal-based architec- ture of the max1472 eliminates many of the commonproblems with saw transmitters by providing greater modulation depth, faster frequency settling, higher tolerance of the transmit frequency, and reduced temperature dependence. combined, these improve- ments enable better overall receiver performance when using a superheterodyne receiver such as the max1470 or max1473. the max1472 is available in a 3mm x 3mm 8-pin sot23 package and is specified for the automotive (-40? to +125?) temperature range. an evaluation kit is available. contact maxim integrated products for more information. applications remote keyless entryrf remote controls tire pressure monitoring security systems radio-controlled toys wireless game consoles wireless computer peripherals wireless sensors features ? 2.1v to 3.6v single-supply operation ? low 5.3ma operating supply current* ? supports ask with 90db modulation depth ? output power adjustable to more than +10dbm ? uses small low-cost crystal ? small 3mm ? 3mm 8-pin sot23 package ? fast-on oscillator 220 s startup time max1472 300mhz-to-450mhz low-power, crystal-based ask transmitter 1 data enable paout 12 8 7 xtal2 v dd gnd pagnd xtal1 sot23 top view 3 4 6 5 max1472 + pin configuration ordering information 8 7 6 5 1 + 2 3 4 data enable paout xtal2 v dd gnd pagnd xtal1 max1472 3.0v data input standby or power-up * 680pf 220pf 50 ? antenna typical application circuit 19-2872; rev 4; 6/12 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. evaluation kit available part temp range pin-package top mark max1472aka+t -40 c to +125 c 8 sot23 aeks * optional power adjust resistor. + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. * at 50% duty cycle (315mhz, 2.7v supply, +10dbm output power) downloaded from: http:///
max1472 300mhz-to-450mhz low-power, crystal-based ask transmitter 2 absolute maximum ratings stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. v dd to gnd ..........................................................-0.3v to +4.0v all other pins to gnd ................................-0.3v to (v dd + 0.3v) continuous power dissipation (t a = +70?) 8-pin sot23 (derate 8.9mw/? above +70?)............714mw operating temperature range .........................-40? to +125? storage temperature range .............................-60? to +150? lead temperature (soldering, 10s) .................................+300? soldering temperature (reflow) .......................................+260? electrical characteristics ( typical application circuit , output power is referenced to 50 ? , v dd = 2.1v to 3.6v, v enable = v dd , t a = -40 c to +125 c, unless otherwise noted. typical values are at v dd = 2.7v, t a = +25 c, unless otherwise noted.) (note 1) parameter symbol conditions min typ max units system performance supply voltage v dd 2.1 3.6 v v enable = v dd (note 2) 5.3 9.4 v enable = v dd , v data = v dd 9.1 16.6 f rf = 315mhz v enable = v dd , v data = 0v 1.5 2.3 v enable = v dd (note 2) 5.7 v enable = v dd , v data = v dd 9.6 supply current i dd f rf = 433mhz v enable = v dd , v data = 0v 1.7 2.7 ma v enable < v il , t a < +85 c (note 3) 5 350 na standby current i stdby v enable < v il t a < +125 c (note 3) 1.7 ? frequency range f rf (note 1) 300 450 mhz data rate (note 3) 0 100 kbps modulation depth on to off p out ratio (note 4) 90 db t a = +25 c, v dd = 2.7v (notes 5, 6) 7.3 10.3 12.8 t a = + 125 c , v d d = 2.1v ( n otes 5, 6) 3.3 6.0 output power p out t a = -40 c, v dd = 3.6v (notes 5, 6) 13.7 16.2 dbm to f offset < 50khz (note 7) 220 turn-on time t on to f offset < 5khz (note 7) 450 ? f rf = 315mhz (note 8) 43.6 transmit efficiency with cw f rf = 433mhz (note 8) 41.3 % f rf = 315mhz (note 9) 37.6 transmit efficiency at 50%duty cycle f rf = 433mhz (note 9) 35.1 % downloaded from: http:///
max1472 300mhz-to-450mhz low-power, crystal-based ask transmitter 3 electrical characteristics (continued) ( typical application circuit , output power is referenced to 50 ? , v dd = 2.1v to 3.6v, v enable = v dd , t a = -40 c to +125 c, unless otherwise noted. typical values are at v dd = 2.7v, t a = +25 c, unless otherwise noted.) (note 1) parameter symbol conditions min typ max units phase-locked loop performance vco gain 330 mhz/v f offset =100khz -84 f rf = 315mhz f offset = 1mhz -91 f offset =100khz -82 phase noise f rf = 433mhz f offset = 1mhz -89 dbc/hz f rf = 315mhz -50 maximum carrier harmonics f rf = 433mhz -50 dbc f rf = 315mhz -75 reference spur f rf = 433mhz -81 dbc loop bandwidth 1.6 mhz crystal frequency f xtal f rf / 32 mhz oscillator input capacitance from each xtal pin to gnd 6.2 pf frequency pushing by v dd 3 ppm/v digital inputs data input high v ih v d d - 0.25 v data input low v il 0.25 v maximum input current 2n a pulldown current 25 ? note 1: 100% tested at t a = +25?. guaranteed by design and characterization over temperature. note 2: 50% duty cycle at 10khz data. note 3: guaranteed by design and characterization, not production tested. note 4: generally limited by pc board layout. note 5: output power can be adjusted with external resistor. note 6: guaranteed by design and characterization at f rf = 315mhz. note 7: v enable < v il to v enable > v ih . f offset is defined as the frequency deviation from the desired carrier frequency. note 8: v enable > v ih , v data > v ih , efficiency = p out /(v dd x i dd ). note 9: v enable > v ih , data toggled from v il to v ih , 10khz, 50% duty cycle, efficiency = p out /(v dd x i dd ). downloaded from: http:///
max1472 300mhz-to-450mhz low-power, crystal-based ask transmitter 4 typical operating characteristics ( typical application circuit , v dd = 2.7v, t a = +25?, unless otherwise noted.) supply current vs. supply voltage max1472 toc01 supply voltage (v) supply current (ma) 3.2 2.4 2.8 6 7 8 9 10 11 12 13 5 2.0 3.6 v enable = v ih , v data = v ih , f rf = 315mhz -40 c +25 c +85 c +125 c supply current vs. supply voltage max1472 toc02 supply voltage (v) supply current (ma) 3.2 2.8 2.4 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 3.6 +85 c +125 c -40 c +25 c v enable = v ih , v data = v il , f rf = 315mhz supply current vs. supply voltage max1472 toc03 supply voltage (v) supply current (ma) 3.2 2.8 2.4 7 8 9 10 11 12 13 65 2.0 3.6 v enable = v ih , v data = v ih , f rf = 433mhz +25 c -40 c +125 c +85 c supply current vs. supply voltage max1472 toc04 supply voltage (v) supply current (ma) 3.2 2.8 2.4 1.2 1.4 1.6 1.8 2.0 2.2 2.0 3.6 +125 c -40 c v enable = v ih , v data = v il , f rf = 433mhz +85 c +25 c output power vs. supply voltage max1472 toc05 supply voltage (v) output power (dbm) 3.2 2.4 2.8 6 7 8 9 10 11 12 13 14 5 2.0 3.6 v enable = v ih , v data = v ih , f rf = 315mhz -40 c -25 c +85 c +125 c output power vs. supply voltage max1472 toc06 supply voltage (v) output power (dbm) 3.2 2.4 2.8 6 7 8 9 10 11 12 13 14 2.0 3.6 v enable = v ih , v data = v ih , f rf = 433mhz -40 c +25 c +85 c +125 c reference spur magnitude vs. supply voltage max1472 toc07 supply voltage (v) reference spur (dbc) 3.2 2.8 2.4 -83 -81 -79 -77 -75 -73 -71 -69 -67 -65-85 2.0 3.6 315mhz 433mhz frequency stability vs. supply voltage max1472 toc08 supply voltage (v) offset frequency (ppm) 3.2 2.8 2.4 -3 -2 -1 0 1 2 -4 2.0 3.6 433mhz 315mhz transmit power efficiency vs. supply voltage max1472 toc09 supply voltage (v) efficiency (%) 3.2 2.8 2.4 30 35 40 45 50 5525 2.0 3.6 +25 c +85 c +125 c -40 c cw outputf rf = 315mhz downloaded from: http:///
max1472 300mhz-to-450mhz low-power, crystal-based ask transmitter 5 transmit power efficiency vs. supply voltage max1472 toc10 supply voltage (v) efficiency (%) 3.2 2.8 2.4 30 35 40 45 5025 2.0 3.6 -40 c +25 c +85 c +125 c cw outputf rf = 433mhz transmit power efficiency vs. supply voltage max1472 toc11 supply voltage (v) efficiency (%) 3.2 2.8 2.4 20 25 30 35 40 45 50 2.0 3.6 -40 c +25 c +85 c +125 c ook output at50% duty cycle f rf = 315mhz transmit power efficiency vs. supply voltage max1472 toc12 supply voltage (v) efficiency (%) 3.2 2.4 2.8 25 30 35 40 4520 2.0 3.6 -40 c +25 c +85 c +125 c ook output at50% duty cycle f rf = 433mhz phase noise vs. offset frequency max1472 toc13 f offset (hz) phase noise (dbc/hz) 1m 100k 10k 1k 100 -130 -120 -110 -100 -90 -80 -70 -60 -50 -40 -140 10 10m supply current and output power vs. external resistor max1472 toc14 external resistor ( ? ) output power (dbm) 100 10 1 2 4 6 8 10 12 0 0.1 1000 2 4 6 8 10 120 supply current (ma) power current f rf = 315mhz supply current vs. output power max1472 toc15 output power (dbm) supply current (ma) 8 6 2 4 3 4 5 6 7 8 9 10 2 01 0 f rf = 315mhz 50% duty cycle cw frequency settling time max1472 toc16 25khz/div enabletransition from low to high enabletransition from low to high 2.5khz/div start: 0sstart: 0s 1ms 1ms typical operating characteristics (continued) ( typical application circuit , v dd = 2.7v, t a = +25?, unless otherwise noted.) am demodulation of pa output max1472 toc17 data rate = 100khz start: 0s stop: 20 s 15%/div downloaded from: http:///
max1472 300mhz-to-450mhz low-power, crystal-based ask transmitter 6 detailed description the max1472 is a highly integrated ook/ask transmit-ter operating over the 300mhz to 450mhz frequency range. the ic includes a complete pll and a highly efficient pa. the device can also be easily placed into a 5na low-power shutdown mode. shutdown mode the enable pin is internally pulled down with a 15?current source. if the pin is left unconnected or pulled low, the max1472 goes into shutdown mode, where the supply current drops to less than 5na. when enable is high, the ic is enabled and is ready for transmission after 220? (frequency settles to within 50khz). the 220? turn-on time of the max1472 is mostly domi- nated by the crystal oscillator startup time. once the oscillator is running, the 1.6mhz pll loop bandwidth allows fast-frequency recovery during power-amplifier toggling. phase-locked loop the pll block contains a phase detector, chargepump, integrated loop filter, vco, 32x clock divider, and crystal oscillator. this pll requires no external components, other than a crystal. the relationship between the carrier and crystal frequency is given by: f xtal = f rf / 32 the lock-detect circuit prevents the pa from transmit-ting until the pll is locked. in addition, the device shuts down the pa if the reference frequency is lost. power amplifier (pa) the pa of the max1472 is a high-efficiency, open-drain,switch-mode amplifier. with proper output matching net- work, the pa can drive a wide range of impedances, including the small-loop pc board trace antenna and any 50 ? antenna. the output-matching network for a 50 ? antenna is shown in the typical application circuit . the output-matching network suppresses the carrier har-monics and transforms the antenna impedance to an optimal impedance at paout (pin 4), which is between 100 ? and 150 ? for a 2.7v supply. when the output matching network is properly tuned,the pa transmits power with high efficiency. the typical application circuit delivers 10.3dbm at 2.7v supply with 9.1ma of supply current. thus, the overall efficiency is44%. the efficiency of the pa itself is more than 52%. applications information output power adjustment it is possible to adjust the output power down to -10dbm with the addition of a resistor. the addition of the power-adjust resistor also reduces power con- sumption. see the supply current and output power vs. external resistor and supply current vs. output power graphs in the typical operating characteristics section. it is imperative to add both a low-frequencyand a high-frequency decoupling capacitor as shown in the typical application circuit . pin description pin name function 1 xtal1 1st crystal input. f rf = 32 x f xtal . 2 gnd ground. connect to system ground. 3 pagnd ground for the power amplifier (pa). connect to system ground. 4 paout power-amplifier output. this output requires a pullup inductor to the supply voltage, which may be partof the output-matching network to a 50 antenna. 5 enable standby/power-up input. a logic low on enable places the device in standby mode. 6 data ook data input. power amplifier is on when data is high. 7v dd supply voltage. bypass to gnd with capacitor as close to the pin as possible. 8 xtal2 2nd crystal input. f rf = 32 x f xtal . downloaded from: http:///
max1472 300mhz-to-450mhz low-power, crystal-based ask transmitter 7 crystal oscillator the crystal oscillator in the max1472 is designed topresent a capacitance of approximately 3.1pf between the xtal1 and xtal2 pins. if a crystal designed to oscillate with a different load capacitance is used, the crystal is pulled away from its intended operating fre- quency, thus introducing an error in the reference fre- quency. crystals designed to operate with higher differential load capacitance always pull the reference frequency higher. for example, a 9.84375mhz crystal designed to operate with a 10pf load capacitance oscillates at 9.84688mhz with the max1472, causing the transmitter to be transmitting at 315.1mhz rather than 315.0mhz, an error of about 100khz, or 320ppm. in actuality, the oscillator pulls every crystal. the crys- tal? natural frequency is really below its specified fre- quency, but when loaded with the specified load capacitance, the crystal is pulled and oscillates at its specified frequency. this pulling is already accounted for in the specification of the load capacitance. additional pulling can be calculated if the electrical parameters of the crystal are known. the frequency pulling is given by: where: f p is the amount the crystal frequency is pulled in ppm. c m is the motional capacitance of the crystal. c case is the case capacitance. c spec is the specified load capacitance. c load is the actual load capacitance. when the crystal is loaded as specified, i.e., c load = c spec , the frequency pulling equals zero. output matching to 50 ? ? when matched to a 50 ? system, the max1472 pa is capable of delivering more than +10dbm of outputpower at v dd = 2.7v. the output of the pa is an open- drain transistor that requires external impedancematching and pullup inductance for proper biasing. the pullup inductance from pa to v dd serves three main purposes: it resonates the capacitance of the paoutput, provides biasing for the pa, and becomes a high-frequency choke to reduce the rf energy cou- pling into v dd . the recommended output-matching net- work topology is shown in the typical application circuit . the matching network transforms the 50 ? load to a higher impedance at the output of the pa in addi-tion to forming a bandpass filter that provides attenua- tion for the higher order harmonics. output matching to pc board loop antenna in most applications, the max1472 pa output has to beimpedance matched to a small-loop antenna. the antenna is usually fabricated out of a copper trace on a pc board in a rectangular, circular, or square pattern. the antenna has an impedance that consists of a lossy component and a radiative component. to achieve high radiating efficiency, the radiative component should be as high as possible, while minimizing the lossy component. in addition, the loop antenna has an inherent loop inductance associated with it (assuming the antenna is terminated to ground). for example, in a typical application, the radiative impedance is less than 0.5 ? , the lossy impedance is less than 0.7 ? , and the inductance is approximately 50nh to 100nh.the objective of the matching network is to match the pa output to the small loop antenna. the matching components thus transform the low radiative and resis- tive parts of the antenna into the much higher value of the pa output, which gives higher efficiency. the low radiative and lossy components of the small loop anten- na result in a higher q matching network than the 50 ? network; thus, the harmonics are lower. f c cccc p m case load case spec = + + ? ? ? ? ? ? 2 11 10 6 downloaded from: http:///
max1472 layout considerations a properly designed pc board is an essential part ofany rf/microwave circuit. on the pa output, use con- trolled-impedance lines and keep them as short as possible to minimize losses and radiation. at high fre- quencies, trace lengths that are on the order of /10 or longer can act as antennas.keeping the traces short also reduces parasitic induc- tance. generally, 1in of pc board trace adds about 20nh of parasitic inductance. the parasitic inductance can have a dramatic effect on the effective inductance. for example, a 0.5in trace connecting a 100nh induc- tor adds an extra 10nh of inductance, or 10%. to reduce the parasitic inductance, use wider traces and a solid ground or power plane below the signal traces. using a solid ground plane can reduce the par- asitic inductance from approximately 20nh/in to 7nh/in. also, use low-inductance connections to ground on all gnd pins, and place decoupling capacitors close to all v dd connections. 300mhz-to-450mhz low-power, crystal-based ask transmitter 8 pa and gate v dd paout pagnd gnd crystal- oscillator driver 32 x pll lock detect max1472 data enable xtal1 xtal2 functional diagram chip information process: cmos package type package code outline no. land pattern no. 8 sot23 k8sn+1 21-0078 90-0176 package information for the latest package outline information and land patterns(footprints), go to www.maxim-ic.com/packages . note that a ?? ?? or ??in the package code indicates rohs status only.package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. downloaded from: http:///
max1472 300mhz-to-450mhz low-power, crystal-based ask transmitter 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. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. 9 __________________maxim integrated products, inc. 160 rio robles, san jose, ca 95134 usa 1-408-601-1000 2012 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history reision number reision date description pages changed 1 4/05 2 6/09 updated ec table max supply currents, added lead-free note, and corrected electrical characteristics notes 1, 2, 3, 6, 8 3 10/10 removed maximum crstal inductance spec from electrical characteristics table 3 4 6/12 updated electrical characteristics , updated power amplifier (pa) section 3, 6 downloaded from: http:///
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