general description the max7044 crystal-referenced phase-locked-loop (pll) vhf/uhf transmitter is designed to transmit ook/ask data in the 300mhz to 450mhz frequency range. the max7044 supports data rates up to 100kbps, and provides output power up to +13dbm into a 50 load while only drawing 7.7ma at 2.7v. the crystal-based architecture of the max7044 elimi- nates many of the common problems with saw-based transmitters by providing greater modulation depth, faster frequency settling, higher tolerance of the trans- mit frequency, and reduced temperature dependence. the max7044 also features a low supply voltage of +2.1v to +3.6v. these improvements enable better overall receiver performance when using the max7044 together with a superheterodyne receiver such as the max1470 or max1473. a simple, single-input data interface and a buffered clock-out signal at 1/16th the crystal frequency make the max7044 compatible with almost any microcon- troller or code-hopping generator. the max7044 is available in an 8-pin sot23 package and is specified over the -40? to +125? automotive temperature range. applications remote keyless entry (rke) tire-pressure monitoring (tpm) security systems garage door openers rf remote controls wireless game consoles wireless computer peripherals wireless sensors features +2.1v to +3.6v single-supply operation ook/ask transmit data format up to 100kbps data rate +13dbm output power into 50 load low 7.7ma (typ) operating supply current* uses small, low-cost crystal small 3mm x 3mm 8-pin sot23 package fast-on oscillator: 250s startup time * at 50% duty cycle (315mhz, 2.7v supply, +13dbm output power) max7044 300mhz to 450mhz high-efficiency, crystal-based +13dbm ask transmitter ________________________________________________________________ maxim integrated products 1 data clkout paout 1 + 2 8 7 xtal2 v dd gnd pagnd xtal1 sot23 top view 3 4 6 5 max7044 pin configuration ordering information max7044 1 xtal1 antenna 3.0v 3.0v 680pf 220pf 100nf 100nf xtal2 f xtal 8 2 gnd v dd 7 3 pagnd data input clock output (f clkout = f xtal /16) data 6 4 paout clkout 5 typical application circuit 19-3221; rev 4; 2/11 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 max7044aka+t -40? to +125? 8 sot23 aejw + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel.
max7044 300mhz to 450mhz high-efficiency, crystal-based +13dbm ask transmitter 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics ( typical application circuit , all rf inputs and outputs are referenced to 50 , v dd = +2.1v to +3.6v, t a = -40? to +125?, unless otherwise noted. typical values are at v dd = +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 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? junction temperature ......................................................+150? lead temperature (soldering, 10s) .................................+300? soldering temperature (reflow) .......................................+260? parameter symbol conditions min typ max units system performance supply voltage v dd 2.1 3.6 v v data at 50% duty cycle, (notes 3, 4) 7.7 14.1 pa on (note 5) 13.8 25.4 f rf = 315mhz pa off (note 6) 1.7 2.8 v data at 50% duty cycle, (notes 3, 4) 8.0 14.4 pa on (note 5) 14.0 25.7 supply current (note 2) i dd f rf = 433mhz pa off (note 6) 1.9 3.1 ma t a < +25? 40 130 standby current i stdby v data < v il for more than wait time (notes 4, 7) t a < +125? 550 2900 na frequency range (note 4) f rf 300 450 mhz data rate (note 4) 0 100 kbps modulation depth (note 8) on to off p out ratio 90 db t a = +25 c, v dd = +2.7v 9.6 12.5 15.4 t a = +125 c, v dd = +2.1v 5.9 9.0 12.0 output power, pa on (notes 4, 5) p out f rf = 300mhz to 450mhz t a = -40 c, v dd = +3.6v 13.1 15.8 18.5 dbm oscillator settled to within 50khz 220 turn-on time t on oscillator settled to within 5khz 450 ? f rf = 315mhz 48 transmit efficiency with cw (notes 5, 9) f rf = 433mhz 47 % f rf = 315mhz 43 transmit efficiency with 50% ook (notes 3, 9) f rf = 433mhz 41 %
max7044 300mhz to 450mhz high-efficiency, crystal-based +13dbm ask transmitter _______________________________________________________________________________________ 3 electrical characteristics (continued) ( typical application circuit , all rf inputs and outputs are referenced to 50 , v dd = +2.1v to +3.6v, t a = -40? to +125?, unless otherwise noted. typical values are at v dd = +2.7v, t a = +25?, unless otherwise noted.) (note 1) note 1: supply current, output power, and efficiency are greatly dependent on board layout and paout match. note 2: production tested at t a = +25? with f rf = 300mhz and 450mhz. guaranteed by design and characterization over tem- perature and frequency. note 3: 50% duty cycle at 10kbps with manchester coding. note 4: guaranteed by design and characterization, not production tested. note 5: pa output is turned on in test mode by v data = v dd /2 + 100mv. note 6: pa output is turned off in test mode by v data = v dd /2 ?100mv. note 7: wait time: t wait = (2 16 x 32)/f rf . note 8: generally limited by pcb layout. note 9: v data = v ih . efficiency = p out /(v dd x i dd ). parameter symbol conditions min typ max units phase-locked loop (pll) 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 -74 reference spur f rf = 433mhz -80 dbc loop bandwidth 1.6 mhz crystal frequency f xtal f rf /32 mhz frequency pulling by v dd 3 ppm/v crystal load capacitance 3pf data input data input high v ih v dd - 0.25 v data input low v il 0.25 v maximum input current 10 ? pulldown current 10 ? clkout output output voltage low v ol i sink = 650? (note 4) 0.25 v output voltage high v oh i source = 350? (note 4) v dd - 0.25 v load capacitance c load (note 4) 10 pf clkout frequency f xtal /16 hz
max7044 300mhz to 450mhz high-efficiency, crystal-based +13dbm ask transmitter 4 _______________________________________________________________________________________ typical operating characteristics ( typical application circuit , v dd = +2.7v, t a = +25?, unless otherwise noted.) (note 1) 7 9 11 13 15 17 19 21 23 2.1 2.4 2.7 3.0 3.3 3.6 supply current vs. supply voltage max7044 toc01 supply voltage (v) supply current (ma) f rf = 315mhz pa on t a = -40 c t a = +25 c t a = +85 c t a = +125 c 5 6 7 8 9 10 11 12 13 2.1 2.4 2.7 3.0 3.3 3.6 supply current vs. supply voltage max7044 toc02 supply voltage (v) supply current (ma) t a = +25 c f rf = 315mhz pa 50% duty cycle at 10khz t a = -40 c t a = +85 c t a = +125 c 8 12 10 16 14 20 18 22 2.1 2.7 2.4 3.0 3.3 3.6 supply current vs. supply voltage max7044 toc03 supply voltage (v) supply current (ma) t a = +25 c f rf = 433mhz pa on t a = -40 c t a = +85 c t a = +125 c 6 7 8 9 10 11 12 13 14 2.1 2.4 2.7 3.0 3.3 3.6 supply current vs. supply voltage max7044 toc04 supply voltage (v) supply current (ma) t a = +25 c f rf = 433mhz pa 50% duty cycle at 10khz t a = -40 c t a = +85 c t a = +125 c 8 10 14 12 16 18 2.1 2.7 2.4 3.0 3.3 3.6 output power vs. supply voltage max7044 toc05 supply voltage (v) output power (dbm) f rf = 315mhz pa on t a = +25 c t a = -40 c t a = +85 c t a = +125 c 8 10 14 12 16 18 2.1 2.7 2.4 3.0 3.3 3.6 output power vs. supply voltage max7044 toc06 supply voltage (v) output power (dbm) f rf = 433mhz pa on t a = +25 c t a = -40 c t a = +85 c t a = +125 c -80 -78 -74 -76 -72 -70 2.1 2.7 2.4 3.0 3.3 3.6 reference spur magnitude vs. supply voltage max7044 toc07 supply voltage (v) reference spur magnitude (dbc) reference spur = f rf f xtal f rf = 433mhz f rf = 315mhz -3 -1 -2 1 0 2 3 2.1 2.7 2.4 3.0 3.3 3.6 frequency stability vs. supply voltage max7044 toc08 supply voltage (v) frequency stability (ppm) f rf = 433mhz f rf = 315mhz 30 35 40 45 50 55 60 65 70 2.1 2.4 2.7 3.0 3.3 3.6 transmit power efficiency vs. supply voltage max7044 toc09 supply voltage (v) transmit power efficiency (%) f rf = 315mhz pa on t a = -40 c t a = +85 c t a = +125 c t a = +25 c
max7044 300mhz to 450mhz high-efficiency, crystal-based +13dbm ask transmitter _______________________________________________________________________________________ 5 20 25 30 35 40 45 50 55 60 2.1 2.4 2.7 3.0 3.3 3.6 transmit power efficiency vs. supply voltage max7044 toc10 supply voltage (v) transmit power efficiency (%) f rf = 315mhz pa 50% duty cycle at 10khz t a = -40 c t a = +85 c t a = +125 c t a = +25 c 30 35 40 45 50 55 60 65 70 2.1 2.4 2.7 3.0 3.3 3.6 transmit power efficiency vs. supply voltage max7044 toc11 supply voltage (v) transmit power efficiency (%) f rf = 433mhz pa on t a = -40 c t a = +85 c t a = +125 c t a = +25 c 15 25 20 40 35 30 55 50 45 60 2.1 2.7 2.4 3.0 3.3 3.6 transmit power efficiency vs. supply voltage max7044 toc12 supply voltage (v) transmit power efficiency (%) f rf = 433mhz pa 50% duty cycle at 10khz t a = +25 c t a = -40 c t a = +85 c t a = +125 c -140 -110 -120 -130 -100 -90 -80 -70 -60 -50 -40 0.01 1 0.1 10 100 1 10 phase noise vs. offset frequency max7044 toc13 offset frequency (khz) phase noise (dbc/hz) 2 4 6 8 10 12 14 16 18 0 1 10 100 1000 10,000 supply current and output power vs. external resistor max7044 toc14 external resistor ( ) supply current (ma) -16 -12 -8 -4 0 4 8 12 16 power current f rf = 315mhz pa on output power (dbm) 0 6 3 12 9 15 18 -10 -2 2 -6 6 10 14 supply current vs. output power max7044 toc15 output power (dbm) supply current (ma) f rf = 315mhz pa on 50% duty cycle 50khz/ div 25 s/div frequency settling time max7044 toc16 am demodulation of pa output data rate = 100khz max7044 toc17 5db/ div 3.2 s/div output spectrum max7044 toc18 10db/ div 0db 100mhz/div f rf = 315mhz typical operating characteristics (continued) ( typical application circuit , v dd = +2.7v, t a = +25?, unless otherwise noted.) (note 1)
detailed description the max7044 is a highly integrated ask transmitter operating over the 300mhz to 450mhz frequency band. the ic requires only a few external components to complete a transmit solution. the max7044 includes a complete pll and a highly efficient power amplifier. the device is automatically placed into a low-power shutdown mode and powers up when data is detected on the data input. shutdown mode the max7044 has an automatic shutdown mode that places the device in low-power mode if the data input has not toggled for a specific amount of time (wait time). the wait time is equal to 2 16 clock cycles of the crystal. this equates to a wait time of approximately 6.66ms for a 315mhz rf frequency and 4.84ms for a 433mhz rf max7044 300mhz to 450mhz high-efficiency, crystal-based +13dbm ask transmitter 6 _______________________________________________________________________________________ pin description pin name function 1 xtal1 1st crystal input. f xtal = f rf /32. 2 gnd ground. connect to system ground. 3 pagnd ground for the power amplifier (pa). connect to system ground. 4 paout power-amplifier output. the pa output requires a pullup inductor to the supply voltage, which can be part of the output-matching network to an antenna. 5 clkout buffered clock output. the frequency of clkout is f xtal /16. 6 data ook data input. data also controls the power-up state (see the shutdown mode section). 7v dd supply voltage. bypass to gnd with a 100nf capacitor as close to the pin as possible. 8 xtal2 2nd crystal input. f xtal = f rf /32. max7044 clkout pagnd paout gnd data xtal1 /16 data activity detector lock detect 32x pll pa crystal- oscillator driver xtal2 v dd functional diagram -55 -52 -46 -49 -43 -40 2.1 2.7 2.4 3.0 3.3 3.6 clkout spur magnitude vs. supply voltage max7044 toc19 supply voltage (v) clkout spur magnitude (dbc) f rf = 315mhz typical operating characteristics (continued) ( typical application circuit , v dd = +2.7v, t a = +25?, unless otherwise noted.) (note 1)
frequency. for other frequencies, calculate the wait time with the following equation: where t wait is the wait time to shutdown and f rf is the rf transmit frequency. when the device is in shutdown, a rising edge on data initiates the warm up of the crystal and pll. the crystal and pll must have 220? settling time before data can be transmitted. the 220? turn-on time of the max7044 is dominated by the crystal oscillator startup time. once the oscillator is running, the 1.6mhz pll loop band- width allows fast frequency recovery during power amplifier toggling. when the device is operating, each edge on the data line resets an internal counter to zero and it begins to count again. if no edges are detected on the data line, the counter reaches the end-of-count (2 16 clock cycles) and places the device in shutdown mode. if there is an edge on the data line before the counter hits the end of count, the counter is reset and the process starts over. it may be necessary to keep the power amplifier on steadily for testing and debugging purposes. to do this, set the data pin voltage slightly above the mid- point between v dd and ground (v dd /2 + 100mv). phase-locked loop the pll block contains a phase detector, charge pump, integrated loop filter, vco, asynchronous 32x clock divider, and crystal oscillator. this pll requires no external components. the relationship between the carrier and crystal frequency is given by: f xtal = f rf /32 the lock-detect circuit prevents the power amplifier from transmitting until the pll is locked. in addition, the device shuts down the power amplifier if the reference frequency is lost. power amplifier (pa) the pa of the max7044 is a high-efficiency, open- drain, switch-mode amplifier. with a proper output matching network, the pa can drive a wide range of impedances, including the small-loop pcb trace anten- na and any 50 antenna. the output-matching network for an antenna with a characteristic impedance of 50 is shown in the typical application circuit . the output- matching network suppresses the carrier harmonics and transforms the antenna impedance to an optimal impedance at paout, which is about 125 . when the output matching network is properly tuned, the power amplifier transmits power with high efficiency. the typical application circuit delivers +13dbm at +2.7v supply with 7.7ma of supply current. thus, the overall efficiency is 48% with the efficiency of the power amplifier itself greater than 54%. buffered clock output the max7044 provides a buffered clock output (clkout) for easy interface to a microcontroller or fre- quency-hopping generator. the frequency of clkout is 1/16 the crystal frequency. for a 315mhz rf transmit fre- quency, a crystal of 9.84375mhz is used, giving a clock output of 615.2khz. for a 433.92mhz rf frequency, a crystal of 13.56mhz is used for a clock output of 847.5khz. the clock output is inactive when the device is in shut- down mode. the device is placed in shutdown mode by the internal data activity detector (see the shutdown mode section). once data is detected on the data input, the clock output is stable after approximately 220?. applications information output power adjustment it is possible to adjust the output power down to -15dbm with the addition of a resistor (see r pwradj in figure 1). the addition of the power adjust resistor also reduces power consumption. 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-frequency and a high-frequency decoupling capacitor as shown in figure 1. crystal oscillator the crystal oscillator in the max7044 is designed to present a capacitance of approximately 3pf between the xtal1 and xtal2 pins. if a crystal designed to t x f wait rf = 232 16 max7044 300mhz to 450mhz high-efficiency, crystal-based +13dbm ask transmitter _______________________________________________________________________________________ 7 max7044 1 xtal1 antenna 3.0v 3.0v 680pf r pwradj 220pf 100nf 100nf xtal2 f xtal 8 2 gnd v dd 7 3 pagnd data input clock output (f clkout = f xtal /16) data 6 4 paout clkout 5 figure 1. output power adjustment circuit
max7044 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 max7044, 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 (or c o ) is the vendor-specified case capacitance of the crystal. 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 max7044 pa is capable of delivering up to +13dbm of output power at v dd = 2.7v. the output of the pa is an open-drain tran- sistor that requires external impedance matching and pullup inductance for proper biasing. the pullup induc- tance from pa to v dd serves three main purposes: it resonates the capacitance of the pa output, provides biasing for the pa, and becomes a high-frequency choke to reduce the rf energy coupling into v dd . the recommended output-matching network topology is shown in the typical application circuit . the matching network transforms the 50 load to approximately 125 at the output of the pa in addition to forming a bandpass filter that provides attenuation for the higher order harmonics. output matching to pcb loop antenna in some applications, the max7044 power amplifier output has to be impedance matched to a small-loop antenna. the antenna is usually fabricated out of a cop- per trace on a pcb in a rectangular, circular, or square pattern. the antenna will have an impedance that con- sists of a lossy component and a radiative component. to achieve high radiating efficiency, the radiative com- ponent should be as high as possible, while minimizing the lossy component. in addition, the loop antenna will have an inherent loop inductance associated with it (assuming the antenna is terminated to ground). for example, in a typical application, the radiative imped- ance 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 power amplifier output to the small-loop antenna. the matching components thus transform the low radiative and resistive parts of the antenna into the much higher value of the pa output. this gives higher efficiency. the low radiative and lossy components of the small-loop antenna result in a higher q matching network than the 50 network; thus, the harmonics are lower. layout considerations a properly designed pcb is an essential part of any rf/microwave circuit. at the power amplifier output, use controlled-impedance lines and keep them as short as possible to minimize losses and radiation. at high frequencies, trace lengths that are approximately 1/20 the wavelength or longer become antennas. for exam- ple, a 2in trace at 315mhz can act as an antenna. keeping the traces short also reduces parasitic induc- tance. generally, 1in of pcb 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 inductor 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. f c cccc x p m case load case spec = + ? + ? ? ? ? ? ? 2 11 10 6 300mhz to 450mhz high-efficiency, crystal-based +13dbm ask transmitter 8 _______________________________________________________________________________________
max7044 300mhz to 450mhz high-efficiency, crystal-based +13dbm ask transmitter _______________________________________________________________________________________ 9 chip information process: cmos 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. package type package code outline no. land pattern no. 8 sot23 k8sn+1 21-0078 90-0176
max7044 300mhz to 450mhz high-efficiency, crystal-based +13dbm ask transmitter 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. 10 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2011 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision number revision date description pages changed 3 6/09 changed part number in ordering information to lead-free and made a correction in the power amplifier (pa) section 1, 7 4 2/11 deleted maximum crystal inductance spec and note 9 from the electrical characteristics table and updated the absolute maximum ratings , shutdown mode , and crystal oscillator sections 2, 3, 7, 8 revision history
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