- i - rct-43 3 -as / asb low-cost saw-stabilized surface mount ook rf tr ansmitter e m bedding the wireless future. . typical applications rct -4 33-as r c t -4 33-as b ordering information features ? 315/41 8/433. 92 mhz versi ons ? low co st ? 1.5-12v o peration ? 5ma cu rre nt con s um ption at 3v ? small size. ? 0dbm output power at 3v ? 4800 b aud o p e ration ? remote keyless entry (rke) ? remote li ght ing co ntrol s ? on-site pagi ng ? a sset t r a cki n g ? wirel e ss alarm and securi ty systems ? long ran ge rfid ? automated reso urce ma n ageme n t description the rct - 433 -as is ideal for rem o te co ntrol appli c ation s whe r e lo w co st and lon ger rang e are requi re d. the transmitte r o perate s from a 1.5-12v sup p ly, makin g it ideal for battery-po w e r e d appli c ation s . the tran smitt e r empl oys a saw- stabili zed o scillator, ensuri ng accu rate freque ncy control for be st rang e pe rforma nce. output power and ha rmo n ic emissi on s are easy to co n t rol, makin g fcc and etsi co mplian c e ea sy. the manufa c turi n g -frie ndly smt style packa ge and lo w- co st make the rct -4 33-a s suitable for high volume appli c ations. the RCT-433-ASb is suitable for ir reflo w ovens a nd ho t air solde r in g . frequenc y part numb er 433.92 mhz RCT-433-AS 433.92 mhz RCT-433-ASb dome stic a n d internation a l orde rs: mouser ele c troni cs 1 - 8 00-346-687 3 ( http://www.m o u s er. c om ) future elec tronics ( http:// www.futureelec tronics . com ) for a radiotronix rep r e s e n tative in your are a plea se visit www.radi otronix.co m and visit our corpo r ate informatio n p age.
- ii - document control created by steve montgomery 05/21/02 engineering review tom marks 8/21/03 marketing review bryan montgomery 8/21/03 approved - engineering tom marks 8/21/03 approved - marketing bryan montgomery 8/21/03 revision history revision author date description 1.1.0 sjm 05/21/02 document created 1.2.0 bfa 07/30/03 revision 1.3.0 sjm 8/21/03 revision. added troubleshooting and design tips. 1.4.0 gwh 6/7/05 added RCT-433-ASb specification to datasheet.
RCT-433-AS low-cost saw-stabiliz ed sur f ace mount ook rf transmitter ? 2001,20 02,2 003 a l l rig h t s rese r v ed pin out diagram pin descrip tion pin no. pin name descrip tion 1 a n t 50 ohm ante n na output. th e antenn a po rt impeda nce affects outp u t power an d ha rmoni c emi ssi ons. an l-c l o w-pa ss filter may be need ed to suf f iciently filter harm oni c emi ssi on s. 2 gnd tran smitter g r oun d. con n e c t to grou nd p l ane. 3 d a t a digital data in put. this inpu t is cmos co mpatible an d sho u ld be driven with cmos level inputs. 4 v c c pin 4 provide s ope rating v o ltage for the transmitter. vcc sho u ld be bypasse d wit h a .01uf ceramic capa cito r and filtere d with a 4.7uf tantalum capacitor. noise on the power supply will degrade transmitter no ise pe rform a n c e. mechanical draw ing 0.30? figure 1: mecha n ical draw ing o f rct- 433-as figure 2: suggested pad l a y out figure 3: mecha n ical draw ing o f rct- 433-asb figure 4: suggested pad l a y out - 2 - 6/7/2005
RCT-433-AS low-cost saw-stabiliz ed sur f ace mount ook rf transmitter ? 2001,20 02,2 003 a l l rig h t s rese r v ed RCT-433-ASb reflow details the rct - 433-asb is suitable for reflow ovens and heat guns. to prevent dam age to the module throug h exce ss h eat, the reflow oven te mperatur e p r ofiling is very importa nt. a sug g e s ted ov en profile is d e ta iled in figure 5 belo w . figure 5: rct-4 33-asb reflo w o v en tem peratu r e profile absolute maximum ratings parameter min max units powe r suppl y and all input pins - 0 . 3 + 1 5 v d c storage te m peratu r e -50 100 c solderi ng te mperature ( 1 0s ec ) 1 n a 3 5 0 c no tes 1 ) t he r c t-43 3-as is ha nd solder only. t he trans m i tter is not suitable for i r reflow o r hot ai r soldering. the rc t-4 33-a sb is suitable for ir reflow an d ho t air soldering. - 3 - 6/7/2005
RCT-433-AS low-cost saw-stabiliz ed sur f ace mount ook rf transmitter ? 2001,20 02,2 003 a l l rig h t s rese r v ed detailed electrical specifications parameter (gener al) sy mbol min ty p. max units notes operating vol t age v cc 1 . 5 3 . 0 1 2 v o l t s d c operating cu rre nt data=v cc i cc -- - 4 . 5 -- - m a @ 3 v operating cu rre nt data= g n d icc - - - 1 0 0 - - - u a @ 3 v freq uen cy accura cy tol fc - 7 5 0 + 7 5 k h z @ 3 v cente r fre q u ency f c - - - 3 1 5 . 0 418.0 433.92 -- - m h z rct -3 15-as rct -4 18-as rct -4 33-as output powe r --- 0 dbm @3v baud rate ? nrz dc --- 4800 bps theory of operation ook modul ation ook modul ation is a bin a ry form of amplitude m odul a t ion. when a l ogical 0 (data line low) i s being sent, the transmitter i s off, fully suppressi ng the carrier. in this stat e, the transmi tter current is very low, less than 1ma. whe n a logi cal 1 is bein g sent, the carrie r is fully on. in this state, the modul e cu rre nt con s um ption is at its highe st, about 4.5 m a with a 3v powe r su ppl y. ook is the m odulatio n method of ch oice for remote control ap plica t ions where p o we r con s um ption and cost are the prim ary factors. becau s e ook tra n smitters d r aw no po wer wh en they transmit a 0, they exhibit significantl y better powe r con s u m ptio n than fsk transmitte rs. ook data rat e is limited by the start-up time of t he oscillator. high-q osc ill ators which have very stable cente r freque nci e s t a ke lo nge r to start-up than l o w-q o scillat o rs. th e sta r t-up time of the oscillator determines the maximum dat a rate that the transmitter can send. design hi n t ?u si ng the rct -43 3 - a s wi t h a microcontroller u art ? : data s h ould be inverted whe n usin g the transmitte r wit h a uart. t he normal ma rkin g state of a uart i s a logic 1, which will cause constant transmi ssi on. by in vertin g the data, the transmitter will be off in a marking state and on in a spaci ng state (logical 0) , en suri ng that the transmitter i s on only whe n data is bei ng sent. the out put of the receiver wo uld al so ne ed to be inverted to properly recove r data. - 4 - 6/7/2005
RCT-433-AS low-cost saw-stabiliz ed sur f ace mount ook rf transmitter ? 2001,20 02,2 003 a l l rig h t s rese r v ed saw stabilized oscillat o r the tran smitt e r is ba si cally a negative re sista n ce lc o scill ator who s e cente r freq uen cy is tightly controlled by a saw re son a tor. saw (s urface aco u st ic wave ) re so nators are fundame n tal freque ncy de vices that resonate at freq uen cie s much highe r than cry s tals. the output of the oscill ator is der ived di rectly from the collector of the oscillator transistor. it i s , therefo r e, very sensitive to vswr. the module i s de sign ed to wo rk with a 50 o h m load, whi c h exhibits a vswr of 1. th e desi gne r m u st en su re that the antenn a exhibits no more tha n a vswr of 2 to guara n tee o peratio n. this is pa rticul arl y true for pcb trace ante n nas. if the module d o e s not appe ar to have any output at the antenna p o rt, it is likely that the antenn a do es not meet this requi rem ent. tro u bleshoo ting hint: if the module appe ars to ha ve no output at the antenn a port, try the following: di sconn ect the antenn a and put a 1000 pf cap in serie s with a 51 oh m resi sto r to grou nd. this will en sure that the tran smitter is prope rly loade d. then look at the o u tput with a scop e and you shoul d se e the oscillator wo rking. if it is worki ng, the an t enna is n o t prope rly tuned and that is th e rea s on that the module i s not working prop erly. if n o t, then che c k the po wer supply and d a ta input for proper voltage levels. data rate the oscillato r start-u p time is on the orde r of 40use c , whi c h limits the maximum data rate to 4 . 8 k b it/s ec . tro u bleshoo ting hint: if the module appe ars to ha ve a good out put, but your data rate is corrupted, that could b e a si gn that the start-up time of the oscill ator is t oo long. the load on the a n tenna affe cts oscillato r st art- up time. to determin e the start-up time of the oscill ator, use a 2 ch annel di gital storage oscillo scope. attach cha n n e l 1 to the data input and chann el 2 to the antenn a out put (don?t worry, it won?t affect the antenna vswr). trigge r the scope o n a ri sing e dge o n cha nnel 1. now, toggle the dat a pin from lo w to high an d captur e the resultin g wave form. you sh ould see a squ a re e dge on ch ann el 1 and the o scill ator rin g -u p o n cha nnel 2. measure the time betwe en the risin g edg e o n cha nnel 1 a nd wh en the oscillator wav e form is at its full voltage swing, an d you have the start - up time. to determi ne if the anten na is the proble m , remove it and place a 1 000 pf cap in seri es with a 51-oh m resi sto r to grou nd an d repeat the test . if the start-up time is co rrect with the test load, the pro b l e m is the ant enna. pow e r suppl y the rct - 433 -as is de sign ed to operate from a 1.5 -1 2v powe r sup p ly. it is cru c i a l that this power supply be very quiet. the powe r suppl y sh ould be bypa ssed usin g a 0.01u f low-es r cerami c ca pa citor an d a 4.7uf ce rami c cap a cito r. th ese cap a cito rs sh ould b e p l ace d as clo s e to the power pin s as p o ssibl e . - 5 - 6/7/2005
RCT-433-AS low-cost saw-stabiliz ed sur f ace mount ook rf transmitter ? 2001,20 02,2 003 a l l rig h t s rese r v ed antenna output pin 1 is a 50 ohm antenna output. it will support most antenna types, including printed antennas integrate d directly onto the pcb. the perform an ce o f the different antenn as vari es. there are many good a pplication not es ava ila ble that descri be external an d pcb trace an tenna s. we maintain a list in the techni cal supp ort section of ou r web s ite. design hi n t ?an t en na traces ?: any time a trace i s long er than 1/8 th the wavele ngth o f the frequen cy it is carrying , it should be a 50 ohm mi cro strip. this e n su re s that a prop er mat c h is maintaine d betwe en th e transmitter output and th e antenn a. design hi n t ?harmonic filter? : the impe dan ce at the ante nna po we r affects t he vswr, power out put, and harmonic o u tput of the trans m itter. in mos t c a s e s , the output of the transmitter may ne ed a low-pa ss lc filter to redu ce h a rm onic emi s sion s. a good cal c ulato r is avai lable on line at http://www- use r s. cs.york.ac.uk/ ~fish e r/lcfilter/ . calculate the filter for a 3db cut - off of the module? s ce nter freque ncy plu s 10%. for e x ample, the cut-o ff for a 43 3.92 mhz mo dule would b e about 47 0 mhz. design hi n t ?t-p a d ? : the rct - 433 -as transmitter ca n be sen s itive to unbal anced or u n m a tche d load s and could fail to operate or o p e rate inte rmittently in this conditi on. try to match you r antenn a load as cl ose to 50 ohms a s po ssible. use a t - pad if ne ce ssary to gi ve the tran smitter a close 50 o h m match b e fore your anten na. a t-pad will also a c t as a n attenuator. see figure 6 belo w , for a t-pad match/attenu ator ci rcuit. figure 6: t-pad example. re sisto r valu es in this t - p ad example a r e: r1 - 10 o h m s . r3 - 15 0 ohm s. - 6 - 6/7/2005
RCT-433-AS low-cost saw-stabiliz ed sur f ace mount ook rf transmitter ? 2001,20 02,2 003 a l l rig h t s rese r v ed contact information addre s s: 207 indu strial blvd moore, okla h o ma 731 60 phone: 405-794 -77 3 0 fax: 405-794 -74 7 7 ww w: www.ra diotro nix.com sale s: sale s@radiot ronix.co m technical support policy radi otronix h a s built a soli d techni cal su pport infras tructure so that you can get answe rs to your que stion s wh en you nee d them. our p r ima r y tech nical su pp ort tools a r e the su ppo rt forum an d kn o w led ge ba se found on o u r web s ite. we are continu o u s ly updatin g these tools. t o find t he latest informatio n about these techni cal sup port tools, ple a se visit http://www.radi otro nix.com/su pp ort/ our te chni cal supp ort engi neers a r e ava ilable mon - f r i betwee n 9:3 0 am and 4:3 0 pm cent ral stand ard time . the best way to reach a techni cal sup port engi nee r is to send a n email by visiting the suppo rt page at http://www.ra diotro nix.com/su pp ort/ . e-mail suppo rt req u e s ts a r e given prio rity beca u s e we ca n ha ndle them mo re efficiently that phon e su pport requ est s . for custo m ers that woul d prefe r to talk dire ct ly to a suppo rt engin e e r, we do offe r phon e su pp ort free of ch arg e . all support reque sts a r e placed in a q ueue a nd ret u rne d in the o r de r that they are received. - 7 - 6/7/2005
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