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MICRF218 3.3v, 315/433mhz wide-if bandwidth ask receiver qwikradio is a registered trademark of micrel, inc. mlf and micro leadframe are trademarks of amkor technology, inc. micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? te l +1 (408) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micre l.com november 2011 m9999-111111 (408) 944-0800 general description the MICRF218 is a 3.0v to 3.6v, 300mhz to 450mhz ask/ook super-heterodyne receiver with user selectable intermediate frequency (if) bandwidths of 550khz or 1500khz at 433.92mhz, making it an excellent solution for use with low-cost saw-based transmitters or transmitters which use low-cost, medium- grade (~30ppm) crystals. the device requires a single, low-cost crystal to select the proper rf frequency, integrated automatic gain control (agc), data slicer, and programmable baseband filter bandwidths of 1.6khz to 13khz allowing the device to support bit-rates up to 20kbps at 433.92mhz. the MICRF218 consumes 4.0ma of supply current at 315mhz and 5.5ma of supply current at 433.92mhz. the device also features a low-power shutdown mode where the device consumes 1 ? a of supply current. the device achieves a sensitivity of -108dbm at 1kbps. for transmitters using higher-qua lity (~10ppm) crystals, the micrf219a/micrf220 offer an if-bandwidth of 330khz and a sensitivity of -110dbm at 1kbps, which can provide better sensitivity and longer range performance. features ? fully integrated 300 to 450mhz ask/ook receiver ? no external if filter required ? wide if-bandwidth filter supports reception of saw based and medium-grade (~30ppm) transmitter ? sensitivity at 433.92mhz at 1kbps with 0.1% ber o -108dbm sensitivity with 550khz if bandwidth o -106dbm sensitivity with 1500khz if bandwidth ? low-supply current o 4.0ma at 315mhz o 5.5ma at 433.92mhz o 1a low-power shutdown mode ? data rates to 10 kbps (manchester encoded) @ 433.92 mhz ? duty cycling capable > 100:1 (shut down mode) ? 60db analog received signal strength indicator ? 16-pin qsop (4.9mm x 6.0mm) package ordering information part number temperature range package MICRF218ayqs ?40 to +85c 16-pin qsop application example +3v c4 0.1f 16v c2 1.5pf 50v ant pcb pattern c5 4.7f 6.3v y1 9.8131mhz c1 6.8pf u1 MICRF218ayqs 1 2 3 4 5 6 7 89 10 11 12 13 14 15 16 ro1 gndrf ant gndrf vdd if_bw sel0 shdn gnd do sel1 cth cagc rssi nc ro2 c3 0.1f 16v l1 39nh l2 68nh do rssi if_bw control
micrel MICRF218 november 2011 2 m9999-111111 (408) 944-0800 315mhz/315.802, 900hz baud rate example pin configuration 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ro1 gndrf ant gndrf vdd if_bw sel0 shdn gnd do sel1 cth cagc rssi nc ro2 MICRF218ayqs pin description 16-pin qsop pin name pin function 1 ro1 reference resonator input connection to colpitts o scillator stage. may also be driven by external reference signal of 1.5v p-p amplitude maximum. 2 gndrf negative supply connection associated with ant rf input. 3 ant rf signal input from antenna. internally ac-coup led. it is recommended that a matching network with an inductor to rf ground is used to improve esd protection. 4 gndrf negative supply connection associated with ant rf input. 5 vdd positive supply connection for all chip functions. 6 if_bw if bandwidth control logic input. use vdd for wide if bandwidth or vss for narrow if bandwidth. this pin must not be left floating, must be tied to vdd or vss. 7 sel0 logic control input with active internal pull-up. used in conjunction with sel1 to control the demodulator low pass filter bandwidth. (see filter table for sel0 and sel1 in application subsection) 8 shdn shutdown logic control input. active internal pull-up and must be pulled low for normal operation. 9 gnd negative supply connection for all chip functions except rf input. 16-pin qsop pin name pin function 10 do demodulated data output. 11 sel1 logic control input with active internal pull-up. used in conjunction with sel0 to control the demodulator low pass filter bandwidth. (see filter table for sel0 and sel1 in application subsection) 12 cth demodulation threshold voltage integration capacitor . capacitor to gnd sets the settling time for the demodulation data slicing level. values a bove 1nf are recommended and should be optimized for data rate and data profile. 13 cagc agc filter capacitor. a c apacitor, normally greater than 0.47uf, is connected from this pin to gnd 14 rssi received signal strength indication output. output is from a buffer with 200 ohms typical output impedance. 15 nc not connected 16 ro2 reference resonator connection. 7pf in parallel with low resistance mos switch to gnd during normal operation. driven by startup excitation circ uit during the internal startup control sequence.
micrel MICRF218 november 2011 3 m9999-111111 (408) 944-0800 absolute maximum ratings (1) supply voltage (v dd ) .................................................+5v input volt age .............................................................+5v junction temperature ......................................... +150c lead temperature (solde ring, 10sec .) .................. 260c storage temperature (t s ) .....................-65oc to +150c maximum receiver i nput power ........................+10dbm esd rating (3) ......................................................... 3kv operating ratings (2) supply voltage (v dd )............................ +3.0v to +3.6v ambient temperature (t a ).................. ?40c to +85c input voltage (v in ) ...................................... 3.6v (max) maximum input rf power .............................. ?20dbm operating frequenc y.......................... 300 to 450 mhz electrical characteristics (4) specifications apply for vdd = 3.0v, vss = 0v, cagc = 4.7uf, cth = 0.1uf, bold values indi cate ?40c - ta +85c. symbol parameter condition min typ max units continuous operation, f rx = 315 mhz 4.0 ma 20:1 duty cycle, f rx = 315 mhz 0.2 ma continuous operation, f rx = 433.92 mhz 5.5 ma i dd MICRF218 operating supply current 20:1 duty cycle, f rx = 433.92 mhz 0.3 ma ishut shut down current 1 a rf/if section image rejection 20 db f rx = 315 mhz, narrow if 0.98 mhz 1 st if center frequency f rx = 433.92 mhz, narrow if 1.4 mhz f rx = 315 mhz, wide if 1.8 mhz 1 st if center frequency f rx = 433.92 mhz, wide if 2.4 mhz f rx = 315 mhz, narrow if (50 ohms) -108 dbm receiver sensitivity @ 1kbps f rx = 433.92 mhz, narrow if (50 ohms) -108 dbm f rx = 315 mhz, wide if (50 ohms) -106 dbm receiver sensitivity @ 1kbps f rx = 433.92 mhz, wide if (50 ohms) -106 dbm f rx = 315 mhz, narrow if 400 khz f rx = 433.92 mhz, narrow if 550 khz f rx = 315 mhz, wide if 1000 khz if bandwidth f rx = 433.92 mhz, wide if 1500 khz f rx = 315 mhz 16-j211 ? antenna input impedance f rx = 433.92 mhz 9.54-j152 ? receive modulation duty cycle note 6 20 80 %
micrel MICRF218 november 2011 4 m9999-111111 (408) 944-0800 symbol parameter condition min typ max units agc attack / decay ratio t attack / t decay 0.1 t a = 25oc 2 na agc pin leakage current t a = +85oc 800 na rfin @ -50dbm 1.13 v agc dynamic range @ frx = 433.92mhz rfin @ -110dbm 1.70 v reference oscillator f rx = 315 mhz, narrow if, if_bw = vss crystal load cap = 10pf 9.8131 mhz f rx = 315 mhz, wide if, if_bw = vdd crystal load cap = 10pf 9.78823 mhz f rx = 433.92 mhz narrow if, if_bw = vss crystal load cap = 10pf 13.5178 mhz frequency f rx = 433.92 mhz wide if , if_bw = vdd crystal load cap = 10pf 13.48352 mhz input impedance 300 k ? input range 0.2 1.5 vp-p source current v(refosc) = 0v 3.5 a demodulator cth source impedance f refosc = 9.8131mhz, 315mhz, note 8 165 k ? ta = 25oc 2 cth leakage current ta = +85oc 800 na sel0=0, sel1=0 1180 hz sel0=0, sel1=1 2360 hz sel0=1, sel1=0 4720 hz demodulator filter bandwidth @ 315 mhz sel0=1, sel1=1 9420 hz cth source impedance f refosc = mhz, 433.92mhz, note 8 120 k ? ta = 25oc 2 cth leakage current ta = +85oc 800 na sel0=0, sel1=0 1625 hz sel0=0, sel1=1 3250 hz sel0=1, sel1=0 6500 hz demodulator filter bandwidth @ 433.92 mhz sel0=1, sel1=1 13000 hz
micrel MICRF218 november 2011 5 m9999-111111 (408) 944-0800 symbol parameter condition min typ max units digital / control functions input high voltage pins do (as input), shdn 0.8v dd v input low voltage pins do (as input), shdn 0.2v dd v source @ 0.8 vdd 260 do pin output current sink @ 0.2 vdd 600 a output rise and fall times ci = 15 pf, pin do, 10-90% 2 sec rssi rssi dc output voltage range 0.22 to 2 v rssi response slope -90 dbm to -40 dbm 35 mv/ dbm rssi output current 1.5 ma rssi output impedance 200 ? rssi response time 50% data duty cycle, input power to antenna = -20 dbm 0.3 sec notes: 1. exceeding the absolute maximum rating may damage the device. 2. the device is not guaranteed to function outside its operating rating. 3. device are esd sensitive. use appropriate esd precaution. exceeding the absolute maximu m rating may damage the device. 4. sensitivity is defined as the average si gnal level measured at the input necessary to achieve 10-2 ber (bit error rate). the input signal is defined as a return-to-zero (rz) waveform with 50% average du ty cycle (manchester encoded) at a data rate of 1kbps. conductive measurement is performed usi ng 50 ohm test circuit . 5. spurious reverse isolation represents the spurious component that appear on the rf input pin (ant) measured into 50 ohms wit h an input rf matching network. 6. when data burst does not contain preamble, the duty cycle is then defined as total duty cycle, including any ?quiet? time be tween data bursts. when data bursts contain preamble sufficient to charge the slice level on capacitor cth, then duty cycle is the effective duty cycle of the burst alone. [for example, 100msec burst with 50% duty cycle, and 100 msec ?quiet? time between bursts . if burst includes preamble, duty cycle is t on /(t on + t off ) = 50%; without preamble, duty cycle is t on /(t on + t off + t quiet ) = 50msec/(200msec) = 25%. t on is the (average number of 1?s/burst) bit time, and t off = t burst ? t on .) 7. parameter scales linearly with reference oscillator frequency f t . for any reference oscillator frequency other than one of the tabulated frequencies (called f tab ), compute new parameter value as the ratio: parameter at f refosc mhz = ( f refosc mhz /f tab ) ( parameter at f tab mhz ) 8. parameter scales inversely with reference oscillator frequenc y ft. for any reference oscillator frequency other than one of the tabulated frequencies (called f tab ), compute new parameter value as the ratio: parameter at f refosc mhz = ( f tab / f refosc mhz ) ( parameter at f tab mhz )
micrel MICRF218 november 2011 6 m9999-111111 (408) 944-0800 typical characteristics
micrel MICRF218 november 2011 7 m9999-111111 (408) 944-0800
micrel MICRF218 november 2011 8 m9999-111111 (408) 944-0800 lo leakage in rf port re-radiation from mi crf218 antenna port
micrel MICRF218 november 2011 9 m9999-111111 (408) 944-0800 figure 1 simplified block diagram functional description figure 1 illustrates the basic structure of the MICRF218. it is composed of three sub-blocks; image rejection uhf down-converter with switch-able dual if bandwidths, the ook demodulator, and reference and control logics. outside the device, the MICRF218 requires only three components to operate: two capacitors (cth, and cagc) and the reference frequency device, usually a quartz crystal. additional five components may be used to improve performance. these are: low cost linear regulator decoupling capacitor, two components for the matching network, and two components for the pre- selector band pass filter. receiver operation lna the rf input signal is ac-coupled into the gate circuit of the grounded source lna input stage. the lna is a cascoded nmos. mixers and synthesizer the lo ports of the mixers are driven by quadrature local oscillator outputs from the synthesizer block. the local oscillator signal from the synthesizer is placed on the low side of the desired rf signal to allow suppression of the image frequency at twice the if frequency below the wanted signal. the local oscillator is set to 32 ti mes the crystal reference frequency via a phase-locked loop synthesizer with a fully integrated loop filter. image reject filter a nd if band-pass filter the if ports of the mixer produce quadrature down converted if signals. these if signals are low-pass filtered to remove higher frequency products prior to
micrel MICRF218 november 2011 10 m9999-111111 (408) 944-0800 the image reject filter where they are combined to reject the image frequencies. the if signal then passes through a third order band pass filter. the if band-pass filters are fully integrated inside the MICRF218. after filtering, f our active gain controlled amplifier stages enhance the if signal to proper level for demodulation. if bandwidth gene ral description the MICRF218 has if filters which may be configured for operation in a narrow band or wide band mode using the if_bw pin. this pin must not be left floating; it must be tied to vdd or vss. with the use of a 13.4835mhz crystal and the if_bw = vdd (wide mode) the if frequency is set to 2.4mhz with a bandwidth of 1500khz. with the use of a 13.5178mhz crystal and the if_bw = vss (narrow mode) the if frequency is set to 1.4mhz with a bandwidth of 550khz at 433.92mhz. the crystal frequency for wide bandwidth if operation is given by: mhz ) 12 2.178 (32 freq operating refosc ? ? (1) the crystal frequency for narrow bandwidth if operation is given by: mhz ) 12 1.198 (32 freq operating refosc ? ? (2) note: the if frequency, if bandwidth, and if separation between if_bw modes using a single crystal will scale linearly and can be calculated as follows: ? ? ? ? ? ? ? ? ? ) 433.92(mhz (mhz) freq operating * er if_parame t er if_parame t mhz 433.92 @ (3) switched crystal application operation appropriate choice of two crystal frequencies and if_bw mode switching allows operation at two different frequencies; one with low bandwidth operation and the other with high bandwidth operation. either the lower or higher reception frequency may use the wider if bandwidth by utilizing the appropriate equation (1) or (2) for each crystal frequency. the following circuit, figure 4, is an example of switched crystal operation. the if bandwidth control and ref-osc control allow switching between two operating frequencies with either a narrow bandwidth or a wide bandwidth. in this case, the logic control switches between 390mhz in wide band mode and 315mhz in narrow bandwidth mode. the advantage of this circuit is when a rf interferer is at one frequency, the receiver can go to another frequency to get clear reception. figure 5 shows pcb layout for MICRF218 with switched crystal operation. please contact the micrel rf application group for detailed document. dual frequency configuration examples: scenario 1: ? frequency 1 - 315mhz narrow bandwidth ? frequency 2 - 433.92mhz wide bandwidth a 9.81314mhz crystal switched in circuit during narrow if mode, combined with a 13.48352mhz crystal, allows operation at 315mhz with 400khz if bandwidth, and at 433.92mhz with 1500khz bandwidth. scenario 2: ? frequency 1 - 315mhz wide bandwidth ? frequency 2 - 433.92mhz narrow bandwidth a 9.78823mhz crystal switched in circuit during wide if mode, combined with a 13.51783mhz crystal, allows operation at 315mhz with 1000khz if bandwidth, and 433.92mhz with 550khz if bandwidth. scenario 3: ? frequency 1 - 315mhz narrow bandwidth ? frequency 2 - 433.92mhz narrow bandwidth a 9.8131mhz crystal switched in circuit, combined with a 13.51783mhz crystal during narrow if mode, allows operation at 315mhz with 400khz if bandwidth, and at 433.92mhz with 550khz bandwidth.
micrel MICRF218 november 2011 11 m9999-111111 (408) 944-0800 +3v c4 0.047f c2 2.2pf j2 rf in c5 4.7f c3 33pf u1 MICRF218ayqs 1 2 3 4 5 6 7 89 10 11 12 13 14 15 16 ro1 gndrf ant gndrf vdd if_bw sel0 shdn gnd do sel1 cth cagc rssi nc ro2 c5 100nf l2 3.9nh y1 9.8131mhz 1 2 c1 np j1 refosc jpr1 0 ohms jpr2 np r11 100k tsdf1220w q2 tsdf1220w q1 r7 100k y2 12.1287mhz r2 np r1 np +3v r6 10k r9 10k r10 100k +3v r8 10k r4 0 ohms c7 np 1 2 j4 con2 if bandwidth control external reference oscillator input vdd = wide bandwidth 0v = narrow bandwidth 1 2 3 4 5 6 7 r5 100k r3 np +3v 3.0 to 3.3v 3.0 to 3.3v com shdn do ref-osc cntr com j3 data out l3 zcb-0603 notes: 1. 0v = common 2. vdd input = 3.0 to 3.3v 3. ref-osc control: 0v = 315 mhz operation, vdd = 390.1 mhz operation l3 100nh l4 100nh np = not placed figure 4. dual frequency qr218bp_swref, 315 mhz and 390 mhz
micrel MICRF218 november 2011 12 m9999-111111 (408) 944-0800 single crystal operation for dual frequency operation when using a single crystal, the if_bw function may be used to switch between two operating frequencies. bandwidth will scale directly with operating frequency (equation 3). higher operating frequency will have the wider if bandwidth. given one operating frequency, the other frequency can be determined.: 2.178) - (384 1.198) (384 * freq1 freq2 bandwidth wide bandwidth narrow ? ? (4) 1.198) - (384 2.178) (384 * freq1 freq2 bandwidth narrow bandwidth wide ? ? (5) ook demodulator the following section discusses the demodulator which is comprised of detector, programmable low pass filter, slicer, and agc comparator. detector and programmable low-pass filter the demodulation starts with the detector removing the carrier from the if signal. post detection, the signal becomes baseband information. the programmable low-pass filter further enhances the baseband information through the use of sel0 and sel1. there are four programmable low-pass filter bw settings for 433.92mhz operation, see table 1. low pass filter bw will vary with rf operating frequency. filter bw values can be easily calculated by direct scaling. see equation below for filter bw calculation: 433.92 freq) (operating * b bw @433.92mhz freq operating w ? (6) it is very important to choose the filter setting that best fits the intended data rate to minimize data distortion. demod bw is set at 13000hz @ 433.92mhz as default (assuming both sel0 and sel1 pins are floating). the low pass filter can be hardware set by external pins sel0 and sel1. sel0 sel1 demod bw (@ 434mhz) 0 0 1625hz 1 0 3250hz 0 1 6500hz 1 1 13000hz - default table 1. demodulation bw selection slicer and slicing level the signal prior to slicer is still linear demodulated am. data slicer converts this signal into digital ?1?s and ?0?s by comparing with the threshold voltage built up on the cth capacitor. this threshold is determined by detecting the positive and negative peaks of the data signal and storing the mean value. slicing threshold is at 50%. after the slicer, the signal is now digital ook data. during long periods of ?0?s or no data period, threshold voltage on the cth capacitor may be very low. large random noise spikes during this time may cause erroneous ?1?s at do pin. agc comparator the agc comparator monitors the signal amplitude from the output of the programmable low-pass filter. when the output signal is less than 750mv, the threshold 1.5a current is sourced into the external cagc capacitor. when the output signal is greater than 750mv, a 15a current sink discharges the cagc capacitor. the voltage developed on the cagc capacitor acts to adjust the gain of the mixer and the if amplifier to compensate for rf input signal level variation. reference control there are two components in reference and control sub-block: 1) reference oscillator and 2) control logic through parallel inputs: sel0, sel1, shdn and if_bw. reference oscillator figure 6. reference oscillator circuit the reference oscillator in the MICRF218 (figure 6)
micrel MICRF218 november 2011 13 m9999-111111 (408) 944-0800 uses a basic colpitts crys tal oscillator configuration with mos transconductor to provide negative resistance. all capacitors shown in figure 6 are integrated inside the micr f218. r01 and r02 are external pins of MICRF218. user only needs to connect reference osc illation crystal. see equation (1) and (2) to calculate reference oscillator crystal frequency for either narrow or wide bandwidth. crystal parameters to operate the MICRF218 with minimum offset, crystal frequencies should be specified with 10pf loading capacitance. please contact micrel rf applications department for crystal parameters.
micrel MICRF218 november 2011 14 m9999-111111 (408) 944-0800 application information figure 7. qr218he1 application example, 433.92 mhz, narrow band the MICRF218 can be fully tested by using one of many evaluation boards designed at micrel for this device. as simple demonstrator, the qr218he1 (figure 7) offers a good start for most applications. it has a helical pcb antenna with its matching network, a bandpass-filter front-end as a pre-selector filter, matching network and the minimum components required to make the device work, which are a crystal, cagc, and cth capacitors. the matching network of the helical pcb antenna (c9 and l3) can be removed and a whip antenna (ant2) or a rf connector (j2) can be used instead. figure 7 shows the entire schematic of it for 433.92mhz. other frequencies can be used. matching network values for other frequencies are listed in the tables below. capacitor c9 and inductor l3 are the passive elements for the helical pcb matching network. tight tolerance is recommended for these devices, like 2% for the inductor and 0.1pf for the capacitor. pcb variations may require different component values and optimization. table 2 shows the matching elements for the device frequency range. for additional information look for small pcb antennas for micrel rf products application note. freq (mhz) c9 (pf) l3(nh) 315.0 1.2 75 390.0 1.2 43 418.0 1.2 36 433.92 1.5 30 table 2. matching values for the helical pcb antenna if whip antenna is used, remove c9 and place the whip antenna in the hole provided in the pcb. also, rf signal can be injected there (add rf connector). l1 and c8 form the pass-b and-filter front-end. its purpose is to attenuate undesired outside band noise which reduces the receiver performance. it is calculated by the parallel resonance equation: c8) * l1 * (2 1 f ? ?
micrel MICRF218 november 2011 15 m9999-111111 (408) 944-0800 table 3 shows the most used frequency values. freq (mhz) c8 (pf) l1(nh) 315.0 6.8 39 390.0 6.8 24 418.0 6.0 24 433.92 5.6 24 table 3. band-pass-filter front-end values there is no need for the bandpass-filter front-end for applications where it is pr oven that the outside band noise does not cause a problem. the MICRF218 has image reject mixers which improve significantly the selectivity and rejection of outside band noise. capacitor c3 and inductor l2 form the l-shape matching network. the capacitor provides additional attenuation for low frequency outside band noise, and the inductor provides additional esd protection for the antenna pin. two methods can be used to find these values, which are matched close to 50 ? . one method is done by calculating the values using the equations below, and the other method uses a smith chart. the latter is made easier by using software that plots the values of the components c8 and l1, like winsmith by noble publishing. to calculate the matching values, one needs to know the input impedance of t he device. table 4 4 shows the input impedance of the MICRF218 and suggested matching values for the most used frequencies. these suggested values may be different if the layout is not exactly the same as the one made here. freq (mhz) c3 (pf) l2(nh) z device ( ? ) 315.0 1.5 68 16.3 -j210.8 390.0 1.2 47 8.26 ? j163.9 418.0 1.2 43 11.1 ? j161.9 433.92 1.1 39 9.54 ? j152.3 table 4. matching values for the most used frequencies for the frequency of 433.92 mhz, the input impedance is z = 9.54 ? j152.3 ? . the matching components are calculated by: equivalent parallel = b = 1/z = 0.410 + j6.54 msiemens rp = 1 / re (b); xp = 1 / im (b) rp = 2.44k ? ; xp = 345.8 ? q = sqrt (rp/50 + 1) q = 7.06 xm = rp / q xm = 345.8 ? resonance method for l-shape matching network: lc = xp / (2pif); lp = xm / (2pif) l2 = (lclp) / (lc + lp); c3 = 1 / (2pifxm) l2 = 38.9nh c3 = 1.06pf doing the same calculation example with the smith chart, it would appear as follows, first, the input impedance of the device is plotted, (z = 9.54 ? j152) ? @ 433.92mhz.(figure 8). figure 8. device?s input impedance, z = 9.54-j152 ? second, the shunt inductor (39nh) and the series capacitor (1.1pf) for the desired input impedance are plotted (figure 9). one can see the matching leading to the center of the smith chart or close to 50 ? .
micrel MICRF218 november 2011 16 m9999-111111 (408) 944-0800 figure 9. plotting the shunt inductor and series capacitor crystal y1 may be either smt or leaded. it is the reference clock for all the device internal circuits. crystal characteristics of 10pf load capacitance, 30ppm, esr < 50 ? , -40oc to +85oc temperature range are desired. table 5 shows the crystal frequencies for wb or nb and one of micrel?s approved crystal manufacturers ( www.hib.com.br ). refosc (mhz) carrier (mhz) hib part number 9.813135, nb 315 sa-9. 813135-f-10-g-30-30-x 12.149596, nb 390.0 sa- 12.149596-f-10-g-30-30-x 13.021874, nb 418.0 sa- 13.021874-f-10-g-30-30-x 13.517827, nb 433.92 sa- 13.517827-f-10-g-30-30-x 9.788232, wb 315 sa-9. 788232-f-10-g-30-30-x 12.118764, wb 390.0 sa- 12.118764-f-10-g-30-30-x 12.988829, wb 418.0 sa- 12.988829-f-10-g-30-30-x 13.483523, wb 433.92 sa- 13.483523-f-10-g-30-30-x table 5. crystal frequency and vendor part number
micrel MICRF218 november 2011 17 m9999-111111 (408) 944-0800 the oscillator of the MICRF218 is colpitts in configuration. it is very sensitive to stray capacitance loads. thus, very good care must be taken when laying out the printed circuit board. avoid long traces and ground plane on the top layer close to the refosc pins ro1 and ro2. when care is not taken in the layout, and crystals from other vendors are used, the oscillator may take longer times to start as well as the time to good data in the do pin to show up. in some cases, if the stray capacitance is too high (> 20pf), the oscillator may not start at all. refer to equations 1 and 2 for crystal frequency calculations. the local osc illator is low side injection (32 13.51783mhz = 432.571mhz), that is, its frequency is below the rf carrier frequency and the image frequency is below the lo frequency. see figure 10. the product of the incoming rf signal and local oscillator signal will yield the if frequency, which will be demodulated by the detector of the device. -f lo f (mhz) desired signal image frequency figure 10. low side injection local oscillator narrow and wide band crystal part numbers, wb = if wide band, nb = if narrow band jp1 and jp2 are the bandwidth selection for the demodulator bandwidth. to set it correctly, it is necessary to know the shor test pulse width of the encoded data sent in the transmitter. similar to the example of the data profile in the figure 11 below, pw2 is shorter than pw1, so pw2 should be used for the demodulator bandwidth calculation which is found by 0.65/shortest pulse width. after this value is found, the setting should be done according to table 6 . for example, if the pulse period is 100sec, 50% duty cycle, the pulse width w ill be 50sec (pw = (100sec 50%) / 100). so, a bandwidth of 13khz would be necessary (0.65 / 50sec). however, if this data stream had a pulse period with 20% duty cycle, then the bandwidth required would be 32.5khz (0.65 / 20sec), which exceeds the maximum bandwidth of the demodulator circuit. if one tries to exceed the maximum bandwidth, the pulse would appear stretched or wider. sel0 jp1 sel1 jp2 demod. bw (hertz) shortest pulse (sec) maximum baud rate for 50% duty cycle (hertz) short short 1625 400 1250 open short 3250 200 2500 short open 6500 100 5000 open open 13000 50 10000 table 6 . jp1 and jp2 setting, 433.92 mhz other frequencies will have different demodulator bandwidth limits, which are derived from the reference oscillator frequency. table 7 and 8 below shows the limits for the other two most used frequencies. sel0 jp1 sel1 jp2 demod. bw (hertz) shortest pulse (sec) maximum baud rate for 50% duty cycle (hertz) short short 1565 416 1204 open short 3130 208 2408 short open 6261 104 4816 open open 12523 52 9633 table 7 . jp1 and jp2 setting, 418.0 mhz sel0 jp1 sel1 jp2 demod. bw (hertz) shortest pulse (sec) maximum baud rate for 50% duty cycle (hertz) short short 1460 445 1123 open short 2921 223 2246 short open 5842 111 4493 open open 11684 56 8987 table 8. jp1 and jp2 setting, 390.0 mhz sel0 jp1 sel1 jp2 demod. bw (hertz) shortest pulse (sec) maximum baud rate for 50% duty cycle (hertz) short short 1180 551 908 open short 2360 275 1815 short open 4720 138 3631 open open 9400 69 7230 table 9. jp1 and jp2 setting, 315.0 mhz.
micrel MICRF218 november 2011 18 m9999-111111 (408) 944-0800 selection of cth and cagc capacitors capacitors c6 and c4, cth and cagc respectively provide time-based reference for the data pattern received. these capacitors are selected according to data profile, pulse duty cycl e, dead time between two received data packets, and if the data pattern has or does not have a preamble. see figure 11 for an example of a data profile. preamble 123456 78910 header pw1 pw2 t1 t2 pw2 = narrowest pulse width t1 & t2 = data period figure 11. example of a data profile for best results, the capacitors should always be optimized for the data pattern used. as the baud rate increases, the capacitor values decrease. table shows suggested values for manchester encoded data, 50% duty cycle. sel0 jp1 sel1 jp2 demod. bw (hertz) cth (c6) cagc (cagc) short short 1625 100nf 4.7f open short 3250 47nf 2.2f short open 6500 22nf 1f open open 13000 10nf 0.47f table 10. suggested cth and cagc values. other components used include c5, which is a decoupling capacitor for the vdd line; r4 reserved for future use and not needed for the evaluation board; r3 for the shutdown pin (shdn = 0, device is operation), which can be removed if that pin is connected to a microcontroller or an external switch, and r1 and r2 which form a voltage divider for the agc pin. one can force a voltage in this agc pin to purposely decrease the devic e sensitivity. special care is needed when doing this operation, as an external control of the agc voltage may vary from lot to lot and may not work the same for several devices. do, rssi and shutdown functions three other pins are worthy of comment. they are the do, rssi, and shut down pins. the do pin has a driving capability of 0.6ma. this drive current is good enough for most of the logic family ics in the market today. the rssi pin provides a transfer function of the rf signal intensity vs. voltage. it is very useful to determine the signal to noise ratio of the rf link, crude range estimate from the transmitter source and am demodulation, which requires a low cagc capacitor value. shut down control the shut down pin (shdn) is useful to save energy. when its level close to v dd (shdn = 1), the device is not in operation. its dc current consumption is less than 1a (do not forget to remove r3). when toggling from high to low, there will be a time required for the device to come to steady state mode, and a time for data to show up in the do pin. this time will be dependent upon many things such as temperature, choice of crystal used, and if the there is an external oscillator with faster start up time. normally, with the crystal vendors suggested, the data will show up in the do pin around 1msec time, and 2msec over the temperature range of the device. see figures 12. figure 12. time-to-good data after shut down cycle, room temperature
micrel MICRF218 november 2011 19 m9999-111111 (408) 944-0800 pcb considerations and layout figures 14 to 17 show top, bottom and silkscreen layers of printed circuit board for the qr218he1 board. gerber files are provided and are downloadable from micrel w ebsite: www.micrel.com, to fabricate this board. keep traces as short as possible. long traces will al ter the matching network, and the values suggested will not be valid. suggested matching values may vary due to pcb variations. a pcb trace 100 mills (2.5mm) long has about 1.1nh inductance. optimization should always be done with exhaustive range tests. make individual ground connections to the ground plane with a via for each ground connection. do not share vias with ground connections. each ground connection = 1 via or more vias. ground plane must be solid and possibly without interruptions. avoid ground plane on top next to the matching elements. it normally adds additional stray capacitance which changes the matching. do not use phenolic material. use only fr4 or better materials. phenolic material is conductive above 200mhz. rf path should be as straight as possible avoiding loops and unnecessary turns. separate ground and vdd lines from other circuits (m icrocontroller, etc). known sources of noise should be laid out as far as possible from the rf circuits. avoid thick traces, the higher the frequency, the thinner the trace should be in order to minimize losses in the rf path. figure 14. qr218he1 top layer. figure15. qr218he1 bottom layer, mirror image.
micrel MICRF218 november 2011 20 m9999-111111 (408) 944-0800 figure 16. qr218he1 top silkscreen layer. figure 17. qr218he1 dimensions.
micrel MICRF218 november 2011 21 m9999-111111 (408) 944-0800 qr218he1 bill of materials, 433.92 mhz item part number manufacturer description qty. ant1 helical pcb antenna pattern 1 ant2 (np)50-ohm ant 168mm 20 awg, rigid wire 0 c9 murata 1.5pf , 0402/0603 1 c4 murata / vishay 4.7f, 0805 1 c3 murata/vishay 1.1pf, 0402/0603 c6,c5 murata / vishay 0.1f, 0402/0603 2 c8 murata 5.6pf, 0402/0603 1 jp1,jp 2, jp3 vishay short, 0402, 0 ? resistor 2 jp4 (np) not placed 0 j2 (np) not placed 0 j3 con6 1 l1 coilcraft / murata / act1 24nh 5%, 0402/0603 1 l2 coilcraft / murata / act1 39nh 5%, 0402/0603 1 l3 coilcraft / murata / act1 30nh 2%, 0402/0603 1 r1,r2, r4 (np) 0402, not placed 0 r3 vishay 100k ? , 0402 1 y1 hcm49 www.hib.com.br (np)13.51783mhz crystal 0 y1a hc49/us www.hib.com.br 13.51783mhz crystal 1 u1 MICRF218ayqs micrel semiconductor qsop16 1 notes: 1. on semiconductor tel: 800-344-3860 2. micro commercial corp. tel: 800-346-3371 3. sumida tel: 408-982-9660 4. murata tel: 949-916-4000 5. vishay tel: 402-644-4218 6. micrel semiconductor tel: 408-944-0800 table 11. qr218he1 bill of materi als, 433.92 mhz, narrow band.
micrel MICRF218 november 2011 22 m9999-111111 (408) 944-0800 package information qsop16 package type (aqs16) micrel, inc. 2180 fortune drive san jose, ca 95131 usa tel +1 (408) 944-0800 fax +1 (408) 474-1000 web http:/www.micrel.com the information furnished by micrel in this data sheet is belie ved to be accurate and reliable. however, no responsibility is a ssumed by micrel for its use. micrel reserves the right to change circuitry and specificati ons at any time without notification to the customer. micrel products are not designed or authori zed for use as components in life support app liances, devices or systems where malfu nction of a product can reasonably be expected to result in personal injury. li fe support devices or systems are devices or systems that (a ) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to resul t in a significant injury to the user. a purchaser?s use or sale of micrel produc ts for use in life support appliances , devices or systems is at p urchaser?s own risk and purchaser agrees to fully indemnify micrel fo r any damages resulting from such use or sale. ? 2007 micrel, incorporated.
micrel MICRF218 november 2011 23 m9999-111111 (408) 944-0800 revision history date edits by: revision number

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