AN120 00.19 SSX127x Reference De esign Overv view APPL LICATION NO OTE AN12 200.1 19 SX1 127x Referrence Desiggn Ov vervieew 2 December 2014 Revision 2, www.semtech.com m Page |1 AN120 00.19 SSX127x Reference De esign Overv view APPL LICATION NO OTE 1 Intrroduction n This purpo ose of this do ocument is to assist the en ngineer with bboth the selecction of the o optimum refeerence design mo odule and the e associated developmentt tool for thee SX127x family of LoRa™ long-range, ultralow powe er transceivers, and proviiding informaation relatingg to circuit o optimization ffor single anttenna port OEM M designs. It is recom mmended thaat this applicaation note is read r in conjunnction with th he following d documents: 1. 2. 3. 4. 5. 6. 7. SX X1272 Datash heet SX X1276 Datash heet SX X1272 Docum ment and Reso ources Design n Pack: SX X1276 Docum ment and Reso ources Design n Pack: SX X1232 Datash heet: SX X1232 Docum mentation and d Resources Design D Pack: Se emtech Appliication Note AN1200.6, A “SX1232 LNA annd PA Impedaance Matchin ng Techniques” LoRa™ ™ Modulattion LoRa™, Semtech’s S pro oprietary mo odulation is a spread-specctrum techniq que that usees wideband linear frequencyy modulated pulses to en ncode inform mation, whosee frequency increases or decreases o over a certain am mount of time e. As with other o spread--spectrum mo odulation tecchniques LoR Ra™ uses thee entire chan nnel bandwid dth to broadcastt a signal, making it robustt to channel noise. n In addittion, becausee LoRa modulation uses a broad band of the t spectrum it is also ressistant to lon ng term relative frequencyy error, multti-path, fading and Doppler effects. e 2 December 2014 Revision 2, www.semtech.com m Page |2 AN120 00.19 SSX127x Reference De esign Overv view APPL LICATION NO OTE 2 Sem mtech LoR Ra Module e Referen nce Design ns 2.1 SX X1272 The SX12 272RF1xAS re eference dessign module schematic iss illustrated below in Figgure 1. From m the schematicc it can be ob bserved that the split RX/TTX path as reeferenced in tthe specificattion section o of the datasheett [1] has been n employed. Figure 1: SX127 72RF1 Evaluatioon Module The split path approaach allows fo or the receive er RFI port tto be optimized for senssitivity ratherr than ned high-efficciency transm mitter RFO / RFI lumped--element matching singlee path employingg the combin network of o the SX1232 2. The high-po ower PA Boosst transmitterr port is emplloyed with th his design, enaabling transmitte ed output po ower up to +2 20 dBm. Note e that the higgh-efficiency RFO port is leeft open-circuit on this design implementaation. Port combination to a single anten nna port is achieved via tthe single control line RF switch. Whille the reference e module is in ntended to in nterface with the approprriate Semtech h SX127x Devvelopment Kiit and 2 December 2014 Revision 2, www.semtech.com m Page |3 AN120 00.19 SSX127x Reference De esign Overv view APPL LICATION NO OTE thus the switch s contro ol line is via a separate con ntrol port, byy open-circuiting R2 and pllacing a 1k reesistor at R1, the e RF switch may be controllled via the RX XTX pin of thee SX1272 (Pin n 23.) 2.2 SX X1276 There are e three versions of the SX1276 reference design moddule and thesse are summaarized below: 1. SX X1276RF1IAS: 169 MHz / 868 8 – 915 MH Hz 2. SX X1276RF1JASS: 433 MHz / 868 8 – 915 MH Hz 3. SX X1276RF1KASS: 470 – 490 MHz M / 868 – 915 9 MHz All SX127 76RF1xAS refference modu ule designs employ e the split RX / TXX path architecture to eensure optimum performance e of both the transmitter and a receiver [[2]. 2.2.1 SX X1276RF1IA AS The SX127 76RF1IAS 169 9 MHz / 868 – 915 MHz re eference desiign module scchematic is illlustrated bellow in Figure 2. Figu ure 2: SX1276RFF1IAS 169 MHz / 868 – 915 MHzz Dual-Band Refference Design 2 December 2014 Revision 2, www.semtech.com m Page |4 AN120 00.19 SSX127x Reference De esign Overv view APPL LICATION NO OTE The 868 – 915 MHz band b is confiigured using RFI_HF and RFO_HF, wh hile the 169 MHz band utilizes PA_Boostt and RFI_LF. Note that the e RFO_LF pin is not conneccted. This referrence design configuratio on is primarilly targeted ffor ETSI / EU U applicationss. The high-p power transmitte er PA_Boost is optimized for the 169 MHz M band to take advantage of the 50 00 mW ERP p power limit available in this band. b RFO_HF is optimize ed for 868 M Hz – 915 MH Hz. The +14 d dBm output p power E permittedd in the majo ority of the Eu uropean 863 – 870 available at this port iss suitable for the 25 mW ERP d as well as th he proposed g2, g g2.1, g3 and g3.1 bannd extensionss (870 – 876 M MHz and 915 – 921 MHz band MHz) 2.2.2 SX X1276RF1JA AS The SX127 76RF1JAS 433 3 MHz / 868 – 915 MHz re eference desiign module scchematic is illlustrated bellow in Figure 3: Figu ure 3: SX1276RFF1JAS 433 MHz / 868 – 915 MHzz Dual-Band Refference Design The 433 MHz M band is configured c with RFI_LF and RFI_LF. Thee high-efficien ncy transmittter is ideally ssuited to meet the maximum m ERP limits prescribed p by both ETSI annd the FCC, even when an ntenna efficieency is reduced due d to size co onstraints. 2 December 2014 Revision 2, www.semtech.com m Page |5 AN120 00.19 SSX127x Reference De esign Overv view APPL LICATION NO OTE The 868 / 915 MHz band b is configgured with PA_Boost P andd RFI_HF. No ote that the RFO_LF pin iis not connected d. This reference design module m configuration is in ntended prim arily for the N North Americcan 902 – 928 8 MHz ISM band. The high po ower transmitter available e at the PA_B Boost pin can n deliver up to +20 dBm o output power. Th he reference design modu ule can also be used to eexploit the hiigher ERP lim mit available iin the European g1.3 band (8 869.40 – 869..65 MHz) and d is also suita ble for the 1000 mW ERP cchannels prop posed uropean g3.1 band extension. for the Eu The high-efficiency, low w-power RFO O_LF port is su uitable for booth the 433 M MHz European n ISM band as well FCC 15.23 31 and 15.24 40 application ns, where low w transmit ppower but lo ong-range, robust links may be required. 2.2.3 SX X1276RF1K KAS The SX12 276RF1KAS 49 90 MHz / 91 15 MHz reference designn module sch hematic is illustrated belo ow in Figure 4: Figure F 4: SX1276 6RF1JAS 490 MH Hz / 915 MHz Duual-Band Refereence Design 2 December 2014 Revision 2, www.semtech.com m Page |6 AN120 00.19 SSX127x Reference De esign Overv view APPL LICATION NO OTE The 490 MHz M band is configured c viaa PA_Boost an nd RFI_LF. Noote that the R RFO_LF pin is left unconnected. The 915 MHz M band is configured c viaa RFO_HF and d RFI_HF. This referrence module e is intended for applicatio ons the Chineese 470-510 M MHz ISM band, where the highpower PA A_Boost transmitter can ou utput the 50 mW ERP allow wed by regulations, even when the anttenna efficiencyy is reduced due d to the dim mensions of an a electricallyy short anten nna. The refeerence modulle can also be used for applications in the e North Ame erican 915 MH Hz and 920 M MHz Japanese ISM band aand is pliant with th he requiremen nts of ARIB Sttandard T1088. fully comp 2.3 SX X127x Refe erence Dessigns The Semtech reference e designs for both SX1272 and SX1276 can be down nloaded from the product pages mtech websitte [3, 4]. The reference de esigns are avaailable in Gerrber format o or as Altium D Design of the Sem packages.. 2.4 SX X127x Development Kits The follow wing develop pment kits are e available fo or Semtech’s SX127x famiily of LoRa™ long-range, ultralow powe er transceivers: 2.4.1 • • SX X1272 / SX1 1273 SX X1272DVK1BAS (868 MHz) SX X1272DVK1CA AS (915 MHz) 2.4.2 • • • SX X1276 / SX1 1277 / SX12 278 SX X1276DVK1IA AS (169 MHz / 868 MHz) SX X1276DVK1JA AS (433 MHz / 868 MHz) SX X1276DVK1KA AS (490 MHz / 915 MHz) 2 December 2014 Revision 2, m www.semtech.com Page |7 AN120 00.19 SSX127x Reference De esign Overv view APPL LICATION NO OTE 3 Dessign Optim mization 3.1 Sin ngle Path (Combine ( d RFI / RF FO) Single patth optimizatio on allows the e designer to o remove thee need for thee RF switch tthrough a lum mpedelement matching m netw work betwee en RFI and RFO O pins. 3.1.1 SX X1272 The SX1272 single patth RF design is identical to t that of thhe SX1232 refference desiggn [6], as thee two devices sh hare a similarr front-end arrchitecture. The recom mmended sch hematic layou ut is illustrated below in Figgure 5: 5.6 nnH 1.8 1 pF 4.7 pF 4.7 pF 1.5 ppF 10 nH RFI RFO 7.5 nH 8.2 nH 33 pF 33 n nH VR_PA 10nF 47 pF OOST PA_BO Figgure 5: SX1272 Single S RF_IO Patth Schematic Note thatt it is recomm mended that PA_Boost is not combineed with the RFI port via a lumped-eleement matching network. 2 December 2014 Revision 2, m www.semtech.com Page |8 AN120 00.19 SSX127x Reference De esign Overv view APPL LICATION NO OTE 3.1.2 SX X1276 The recom mmended SX1276 single path p referencce design is il lustrated in FFigure 6 and the correspo onding BOMs for the three low w-frequency bands in Tablle 1, below: Figgure 6: SX1276 Single S RF_IO Patth Schematic 2 December 2014 Revision 2, www.semtech.com m Page |9 AN120 00.19 SSX127x Reference De esign Overv view APPL LICATION NO OTE COMPO ONENT IDENTTIFIER CC CD C1 C2 C3 C4 C10 L0 LP L1 L2 L3 FR REQUENCY B BAND 169 MHzz 433 MHz 220 pF 47 pF 220 pF 100 pF 15 pF 6.8 pF 33 pF 15 pF 33 pF 12 pF 8.2 pF 4.7 pF 5.6 pF 2.2 pF 82 nH 18 nH 100 nH 47 nH 56 nH 22 nH 47 nH 12 nH 33 nH 18 nH Table 1: RF_LF Matching Netw work BOM Again it is i recommen nded that PA A_Boost is no ot combinedd with the RFI port via a lumped-eleement matching network. 3.2 Lo oad-Pull an nd Matchin ng It may no ot be possible to replicate e the topology and layouut of the Sem mtech referen nce design d due to design constraints or PCB P stack deffinition. In this case the cuustomer will require detaiils of the optimum port impe edances to en nable both op ptimum noise e matching foor the receiveer RFI ports aand optimum loadimpedancce for the tran nsmitter RFO and PA_Boosst ports. Details off the matching network and recomm mended optiimization pro ocedure for SX1272, thee high frequencyy RF ports (RFI_HF and RFFO_HF) of the e SX1276 as well as PA_B Boost when tthe high-frequ uency band is se elected, can be b found in [7 7]. This procedure can also be used for matching the SX1276 ports for opeeration in the lower-frequ uency he optimum port p impedancces measured d for the TX pports are tabu ulated below: bands. Th 2 December 2014 Revision 2, www.semtech.com m P a g e | 10 AN120 00.19 SSX127x Reference De esign Overv view APPL LICATION NO OTE PORT RFO_LF PA_Boost FREQ QUENCY (MHzz) 169 434 490 169 434 490 Zopt (Ω) 47.8 8 + j28.9 65.2 2 – j1.7 61.3 3 – j7.8 13.2 2 + j6.7 13.7 7 + j2,6 14.0 0 + j1.1 Table T 2: Optimu um SX1276 Port impedance 2 December 2014 Revision 2, www.semtech.com m P a g e | 11 AN120 00.19 SSX127x Reference De esign Overv view APPL LICATION NO OTE 4 Refferences [1]. SX X1272 Datash heet - http://w www.semtecch.com/apps//filedown/dow wn.php?file=sx1272.pdf [2]. SX X1276 Datash heet - http://w www.semtecch.com/apps//filedown/dow wn.php?file=sx1276.pdf [3]. SX X1272 Document and Resources R Design D Pack - http://ww ww.semtech.ccom/wireless-rf/rftrransceivers/sxx1272/ [4]. SX X1276 Document and Resources R Design D Pack - http://ww ww.semtech.ccom/wireless-rf/rftrransceivers/sxx1276/ [5]. SX X1232 Datash heet - http://w www.semtecch.com/apps//filedown/dow wn.php?file=sx1232.pdf [6]. SX X1232 Docum mentation an nd Resources Design Packk - http://ww ww.semtech.ccom/wirelesss-rf/rftrransceivers/sxx1232/ [7]. Se emtech Appliication Note AN1200.6, “SSX1232 LNA and PA Impeedance Match hing Techniqu ues” htttp://www.se emtech.com//apps/filedow wn/down.php ?file=AN12000-16_SX1232__API_RF_ST.p pdf 2 December 2014 Revision 2, m www.semtech.com P a g e | 12 AN120 00.19 SSX127x Reference De esign Overv view APPL LICATION NO OTE © Semtech 2014 uction in whole or o in part is proh hibited without the prior writte n consent of thee copyright owner. The All rights resserved. Reprodu information n presented in th his document do oes not form parrt of any quotatiion or contract, is believed to bee accurate and rreliable and may be e changed witho out notice. No liability will be acccepted by the publisher for anny consequence of its use. Publlication thereof doe es not convey no or imply any license under paten nt or other indusstrial or intellecttual property rigghts. Semtech asssumes no responsibility or liabilitty whatsoever for f any failure or unexpected operation resuulting from misu use, neglect im mproper mited to, expossure to installation, repair or imprroper handling or unusual phyysical or electriccal stress includding, but not lim parameters beyond the spe ecified maximum m ratings or operration outside thhe specified rangge. SEMTECH PRODUCTS P ARE NOT DESIGNED D, INTENDED, AUTHORIZED A O R WARRANTED D TO BE SUITAB BLE FOR USE IN N LIFESUPPORT APPLICATIONS, A DEVICES D OR SYSSTEMS OR OTHEER CRITICAL AP PLICATIONS. INCLUSION OF SEEMTECH PRODU UCTS IN SUCH APPLLICATIONS IS UN NDERSTOOD TO O BE UNDERTAKEN SOLELY ATT THE CUSTOM MER’S OWN RISK K. Should a customer purchase orr use Semtech products p for any such unauthorized application,, the customer sshall indemnify and hold Semteech and its officers, employees, sub bsidiaries, affiliaates, and distrib butors harmless against all claim ms, costs damages and attorneey fees d arise. which could Contact In nformation Semtecch Corporation Wireless Sensing an nd Timing Prroducts Diviision 200 0 Flynn Road d, Camarillo o, CA 93012 Phone e: (805) 498--2111 Fax: (8805) 498-3804 E-m mail: supportt_rf_na@se mtech.com Intternet: http:://www.sem mtech.com 2 December 2014 Revision 2, www.semtech.com m P a g e | 13
