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rev. 0.3 2/13 copyright ? 2013 by silicon laboratories AN602 AN602 si4822/26/27/40/44 a ntenna , s chematic , l ayout , and d esign g uidelines 1. introduction this document provides general si48 22/26/27/40/44 design and am/fm/sw antenna selection guidelines, including schematic, bom, and pcb layout. all users s hould follow the si4822/26/27/40/44 design guidelines presented in ?2. si4822/26/27/40/44 default frequency ba nd definition and selecti on?and ?3. si48422/26/27/40/44 ssop/soic schematic and layout? and choose the appropriate antennas based on the applications and device used as described in ?4. headphone antenna for fm receive? through ?8. whip antenna for sw receiver?. table 1. part selection guide ? part number ? general description function fm antenna am antenna sw antenna fm receiver am receiver sw receiver headphone whip ferrite loop air loop whip si4822 entry level wheel-tuned digital display am/fm receiver, mono audio ? ? ? ? ? ?? si4826 entry level wheel-tuned digital display am/fm/sw receiver, mono audio ???????? si4827 entry level wheel-tuned digital display am/fm/sw receiver, wide fm/sw band, mono audio ???????? si4840 wheel-tuned digital display am/fm receiver, stereo audio ?? ???? si4844 wheel-tuned digital display am/fm/ sw receiver , wide fm/sw band, ste- reo audio ????????
AN602 2 rev. 0.3 2. si4822/26/27/40/44 default freque ncy band definition and selection for si4822/26/27/40/44, there are two methods for defini ng a frequency band, one is to select one of the chip internal default bands by using the slide switch and re sistor ladder. another method is to use the host mcu sending command to make the chip work in the desired band. refer to application note, ?an610: si48xx atdd programming guide?, for information on how to use the si 4822/26/27/40/44 to define a frequency band and set a band property. this section describes how to select the default frequency band by using the slide switch and resistors ladder. the si4822/40 has five defined fm bands and five de fined am bands. the si4826/27/44 has an added 16 sw bands. in each fm band, the parts also offer two de-e mphasis selections and two led stereo separation threshold selections, which results in a tota l 41 combinations to choose from. the si4822/26/40/44-a supports fm band range less t han 23 mhz and sw band range less than 1.15 mhz. the si4827-a/44-b supports wider fm/sw band range. refer to application note, ?an610: si48xx atdd programming guide? for details. 2.1. si4822/26/27/40/44 default band definition for si4822/26/27/40/44, the fm band definition is in fact a combination of frequency range, de-emphasis, and led stereo separation threshold. customers should choose th e band according to not only frequency range, but also de-emphasis setting and led stereo separation requirements. for am and sw, simply choose the band according to the frequency range desired. table 2. band sequence definition band number band name band frequency range de-emphasis (fm) channel space (am) stereo led on conditions (only for si4840/44) total r to gnd (k ? , 1%) band1 fm1 87?108 mhz 75 s separation = 6 db, rssi = 20 47 band2 fm1 87?108 mhz 75 s separation = 12 db, rssi = 28 57 band3 fm1 87?108 mhz 50 s separation = 6db, rssi = 20 67 band4 fm1 87?108 mhz 50 s separation = 12 db, rssi = 28 77 band5 fm2 86.5?109 mhz 75 s separation = 6 db, rssi = 20 87 band6 fm2 86.5?109 mhz 75 s separation = 12 db, rssi = 28 97 band7 fm2 86.5?109 mhz 50 s separation = 6 db, rssi = 20 107 band8 fm2 86.5?109 mhz 50 s separation = 12 db, rssi = 28 117 band9 fm3 87.3?108.25 mhz 75 s separation = 6 db, rssi = 20 127
AN602 rev. 0.3 3 band10 fm3 87.3?108.25 mhz 50 s separation = 12 db, rssi = 28 137 band11 fm3 87.3?108.25 mhz 75 s separation = 6 db, rssi = 20 147 band12 fm3 87.3?108.25 mhz 50 s separation = 12 db, rssi = 28 157 band13 fm4 76?90 mhz 75 s separation = 6 db, rssi = 20 167 band14 fm4 76?90 mhz 75 s separation = 12 db, rssi = 28 177 band15 fm4 76?90 mhz 50 s separation = 6 db, rssi = 20 187 band16 fm4 76?90 mhz 50 s separation = 12 db, rssi = 28 197 band17 fm5 64?87 mhz 75 s separation = 6 db, rssi = 20 207 band18 fm5 64?87 mhz 75 s separation = 12 db, rssi = 28 217 band19 fm5 64?87 mhz 50 s separation = 6 db, rssi = 20 227 band20 fm5 64?87 mhz 50 s separation = 12 db, rssi = 28 237 band21 am1 520?1710 khz 10 khz 247 band22 am2 522?1620 khz 9khz 257 band23 am3 504?1665 khz 9khz 267 band24 am4 520?1730 khz 10 khz 277 band25 am5 510?1750 khz 10 khz 287 band26 sw1 5.6?6.4 mhz 297 band27 sw2 5.95?6.2 mhz 307 band28 sw3 6.8?7.6 mhz 317 band29 sw4 7.1?7.6 mhz 327 band30 sw5 9.2?10 mhz 337 table 2. band sequence definition (continued) band number band name band frequency range de-emphasis (fm) channel space (am) stereo led on conditions (only for si4840/44) total r to gnd (k ? , 1%)
AN602 4 rev. 0.3 2.2. default band selection refer to figure 1 for the band selection circuits. selecting a band is to determine the resistance value from the band select pin to gnd. to select a specific band, you need to ensure two things: ?? total value of resistance from the band to gn d is equal to the value specified in table 2 ?? total resistance from tune1 to gnd is 500 k ? in 1% tolerance some commonly used bands and their respective selectio n circuits are listed below for your quick reference. 2.2.1. typical 12-band application figure 1 and table 3 illustrate the band and resistor value details for a typical 12-band application. band31 sw6 9.2?9.9 mhz 347 band32 sw7 11.45?12.25 mhz 357 band33 sw8 11.6?12.2 mhz 367 band34 sw9 13.4?14.2 mhz 377 band35 sw10 13.57?13.87 mhz 387 band36 sw11 15?15.9 mhz 397 band37 sw12 15.1?15.8 mhz 407 band38 sw13 17.1?18 mhz 417 band39 sw14 17.48?17.9 mhz 427 band40 sw15 21.2?22 mhz 437 band41 sw16 21.45?21.85 mhz 447 table 2. band sequence definition (continued) band number band name band frequency range de-emphasis (fm) channel space (am) stereo led on conditions (only for si4840/44) total r to gnd (k ? , 1%)
AN602 rev. 0.3 5 figure 1. a typical 12-band selection circuit fm1 (87mhz - 108mhz) fm5 (64mhz - 87mhz) am1 (520khz - 1710khz) fm4 (76mhz - 90mhz) sw1 (5.6mhz - 6.4mhz) sw3(6.8mhz - 7.6mhz) sw5(9.2mhz - 10.0mhz) sw7(11.45mhz - 12.25mhz) sw9 (13.4mhz - 14.2mhz) sw11 (15mhz - 15.9mhz) sw13 (17.1mhz - 18mhz) sw15 (21.2mhz - 22mhz) si4826/27/44 only 12 3 4 5 6 7 8 9 10 11 12 13 s2 r15 20k 1% r10 20k 1% r12 20k 1% r11 20k 1% r14 20k 1% r9 20k 1% r7 40k 1% r8 50k 1% r28 40k 1% r29 120k 1% r33 0r 1% r35 20k 1% r36 33k 1% r43 30k 1% r44 47k 1% ba nd tune1
AN602 6 rev. 0.3 2.2.2. typical 2-band application for europe figure 2 and table 4 show the band and resistor valu e details for a typical european 2-band application. table 3. typical 12-band selection band number band name band frequency range de-emphasis (fm) channel space (am) stereo led on conditions (only for si4840/44) total r to gnd (k ? , 1%) band1 fm1 87?108 mhz 75 s separation = 6 db, rssi = 20 47 band13 fm4 76?90 mhz 75 s separation = 6 db, rssi = 20 167 band17 fm5 64?87 mhz 75 s separation = 6 db, rssi = 20 207 band21 am1 520?1710 khz 10 khz 247 band26 sw1 5.6?6.4 mhz 297 band28 sw3 6.8?7.6 mhz 317 band30 sw5 9.2?10 mhz 337 band32 sw7 11.45?12.25 mhz 357 band34 sw9 13.4?14.2 mhz 377 band36 sw11 15?15.9 mhz 397 band38 sw13 17.1?18 mhz 417 band40 sw15 21.2?22 mhz 437 table 4. typical european 2-band selection band number band name band frequency range de-emphasis (fm) channel space (am) stereo led on conditions (only for si4840/44) total r to gnd (k ? , 1%) band4 fm1 87?108 mhz 50 s separation = 12 db, rssi = 28 77 band22 am2 522?1620 khz 9khz 257
AN602 rev. 0.3 7 figure 2. typical 2-band selection circuit for europe 2.2.3. typical 2-band application for us figure 3 and table 5 show the band and resistor value details for a typical 2-band application for us. figure 3. typical 2-band selection circuit for us table 5. typical us 2-band selection band number band name band frequency range de-emphasis (fm) channel space (am) stereo led on conditions (only for si4840/44) total r to gnd (k ? , 1%) band2 fm1 87?108 mhz 75 s separation = 12 db, rssi = 28 57 band21 am1 520?1710 khz 10 khz 247 fm am r4 180k 1% r3 243k 1% r5 77k 1% 12 3 s2 ba nd tune1 fm am r4 190k 1% r3 253k 1% r5 57k 1% 12 3 s2 ba nd tune1
AN602 8 rev. 0.3 3. si48422/26/27/40/44 ssop /soic schematic and layout this section shows the typical schematic and layout requ ired for optimal si4822/26/27 /40/44 performance. si4822/ 26/40/44 offer two methods to select the radio band by tu ner setting and two methods to set band property by tuner setting. normally, there are four kinds of typical application circuits in real application, however, the si4827 offers two methods to select the radio band by tuner setting and two methods to set band property by host mcu, so there are two kinds of typical application circuits in real application. 3.1. si4822/26/40/44 applicat ion circuit: host mcu sel ect radio band and set band property figure 4 shows the applications circuits of si4822/26/40/44 when the application is to us e the host mcu to select radio band and set band property. normally, a push button for selecting band is connected to the host mcu. the mcu then detects the push button?s action and sends a command to si4822/26/40/44 to set the desired band. the host mcu can also set the band property, such as band top frequency point and bottom frequency point, stereo indication threshold (only for si4840/ 44), de-emphasis, am tuning spacing, etc. the two key points to ensure si4822/26/40/44 works properly are as follows: 1. no pull-up resistor is connected to pin 1 lna_en 2. pin 5 band is connected to its power supply v cc directly c6 & c15 are required bypass capacitors for v dd1 /v dd2 power supply pin 20/21. place c6/c15 as close as possible to the v dd1 /v dd2 pin 20/21 and dbyp pin 22. these recommendatio ns are made to reduce the size of the current loop created by the bypass cap and routing, minimi ze bypass cap impedance, and return all currents to the dbyp pin. pin 22 is the dedicated bypass capacitor pin. do not connect it to power supply gnd on pcb. pin 13 and pin 14 are the gnd of the chip; these pins must be well connected to the power supply gnd on pcb. pin 9 is the rfgnd of the chip ; it must be well connected to the power supply gnd on pcb. c4 and/or c7 (4.7 f) are ac coupling caps for receiver analog audio output from pin 23 and/or pin 24. the input resistance of the amplifier, r, such as a headphone amplifier, and the capaci tance, c, will set the high pass pole given by equation 1. placement locati ons of c4 and c7 are not critical. equation 1. high-pass pole calculation c28 and c29 (22 pf) are cr ystal loading caps required on ly when using the internal o scillator feature. refer to the crystal data sheet for the proper load capacitance and be ce rtain to account for parasitic capacitance. place caps c28 and c29 such that they share a co mmon gnd connection and the current loop area of the crystal and loading caps is minimized. y1 (32.768 khz) is an optional crystal required only when using t he internal oscillator feature. place the crystal y1 as close to xtalo pin 18 and xtali pin 19 as possible to minimize current loops. if applying an external clock (32.768 khz) to xtali, leave xtalo floating. do not route digital signals or reference clock traces near pin 6 and 7. do not route pi n 6 & 7. these pins must be left floating to guarantee proper operation. pin 2, 15, 16, 17 are the required communi cation pins with host mcu. a 100 k ? pull-up resistor r6 and 0.1 f bypass cap c19 are recommended for the pin 15 rst. pull-up resistor r3 of 10 k ? is necessary for pin 16 sdio. vr1 (100 k / 10%), r27, c1, c13 co nstitute the tuning circuit. 100k ?? at 10% tolerance is recommended for vr1. q1(2sc9018), together with its peripherals b6, c30,31,33, 36, r31,32,34,41, is the lna circuit for all sw bands. the lna is switched off by lna_en signal in am and fm mode controlled by si4826/44. for si4822/26, do not route pin 23. this pin must be left floating to guarantee proper operation. f c 1 2 ? rc --------------- - =
AN602 rev. 0.3 9 figure 4. si4822/26/40/44 applications circuit: mcu select band and set band property si4822/26/40/44 si4826/44 only fm/sw optional to host mcu to host mcu (for si4822/26, pin23 is nc) (for si4822/26, pin24 is aout) l2 270nh c19 0.1u c15 4.7u vr1 100k 10% c6 0.1u r6 100k c5 0.47u q1 2sc9018 r31 1k r32 10r c30 33n c33 10p r41 120k c31 33n b6 2.5k/100m c36 0.47u ant1 mw ferrite antenna r34 100k c34 33p 1 lna_en 2 irq 3 tune1 4 tune2 5 ba nd 6 nc 7 nc 8 fmi 9 rfgnd 10 nc 11 nc 12 ami 13 gnd 14 gnd 15 rst 16 sdio 17 sclk 18 xtalo 19 xtali 20 vdd1 21 vdd2 22 dbyp 23 rout/nc 24 lout/aout u1 c1 0.1u r27 100r c13 47u c4 4.7u c7 4.7u y1 32.768khz c28 22p c29 22p r3 10k ant2 lna_en [1] lna_en [1] tune1 reset vcc vcc vcc irq sclk sdio vcc vcc vcc lout rout
AN602 10 rev. 0.3 3.2. si4822/26/40/44 appl ication circuits: host mcu select default band and use default band property figure 5 shows si4822/26/40/44 applicati on circuits that enable the host mcu to select default bands. in this application, the host mcu sends comm ands to si4822/26/40/44 to select t he desired default band. however, the mcu cannot define those band properties already fixed in th e default band definition, as stated in ?2.1. si4822/26/ 27/40/44 default band definition?. the host mcu can only define the band properties which are not fixed in the default band definition, such as softmute property, etc. for more details, refer to ?an610: si48xx atdd programming guide?. the two key points to ensure si4822/26/40/44 works properly are as follows: 1. add pull-up resistor r42 of 10k ? to pin 1 lna_en. 2. ensure pin 5 band is connected to its power supply v cc directly. figure 5. sisi4822/26/40/44 applications circuit: mcu select default band and use default band property si4822/26/40/44 si4826/44 only fm/sw to host mcu optional to host mcu (for si4822/26, pin23 is nc) (for si4822/26, pin24 is aout) l2 270nh c19 0.1u c15 4.7u vr1 100k 10% c6 0.1u r6 100k c5 0.47u q1 2sc9018 r31 1k r32 10r c30 33n c33 10p r41 120k c31 33n b6 2.5k/100m c36 0.47u ant1 mw ferrite antenna r34 100k c34 33p 1 lna_en 2 irq 3 tune1 4 tune2 5 ba nd 6 nc 7 nc 8 fmi 9 rfgnd 10 nc 11 nc 12 ami 13 gnd 14 gnd 15 rst 16 sdio 17 sclk 18 xtalo 19 xtali 20 vdd1 21 vdd2 22 dbyp 23 rout/nc 24 lout/aout u1 c1 0.1u r27 100r c13 47u c4 4.7u c7 4.7u y1 32.768khz c28 22p c29 22p r3 10k r42 10k ant2 lna_en [1] lna_en [1] tune1 reset vcc vcc vcc irq sclk sdio vcc vcc vcc lout rout vcc
AN602 rev. 0.3 11 3.3. si4822/26/40/44 applicat ion circuits: slide switch se lect band and mcu re-define band property figure 7 illustrates an si4822/26 /40/44 application circuit wh ich uses a slide switch for band selection and enables the host mcu to re-define the band property. for the band selection method using slide switch and resistors ladder, refer to "2.2. default band se lection" on page 4. in this application, the user can select any default band and the mcu will re-define the band?s property according to the design requirement. the mcu can only re-define the selected band?s property, it cannot change an fm band to an am or sw band, and vice versa. the two key points to ensure the si4822/26/40/44 works properly are as follows: 1. no pull-up resistor is connected to pin 1 lna_en. 2. pin 5 band is connected to slide switch. figure 6. si4822/26/40/44 applications circuit: slide switch select band and mcu re-define band property fm1 (87mhz - 108mhz) fm5 (64mhz - 87mhz) am1 (520khz - 1710khz) si4822/26/40/44 fm4 (76mhz - 90mhz) sw1 (5.6mhz - 6.4mhz) sw3(6.8mhz - 7.6mhz) sw5(9.2mhz - 10.0mhz) sw7(11.45mhz - 12.25mhz) sw9 (13.4mhz - 14.2mhz) sw11 (15mhz - 15.9mhz) sw13 (17.1mhz - 18mhz) sw15 (21.2mhz - 22mhz) si4826/44 only si4826/44 only fm/sw optional to host mcu to host mcu (for si4822/26, pin23 is nc) (for si4822/26, pin24 is aout) 12 3 4 5 6 7 8 9 10 11 12 13 s2 r15 20k 1% r10 20k 1% r12 20k 1% r11 20k 1% r14 20k 1% r9 20k 1% r7 20k 1% r8 50k 1% r28 40k 1% r29 120k 1% l2 270nh c19 0.1u c15 4.7u vr1 100k 10% c6 0.1u r6 100k c5 0.47u q1 2sc9018 r31 1k r32 10r c30 33n c33 10p r41 120k c31 33n b6 2.5k/100m c36 0.47u ant1 mw ferrite antenna r34 100k c34 33p 1 lna_en 2 irq 3 tune1 4 tune2 5 ba nd 6 nc 7 nc 8 fmi 9 rfgnd 10 nc 11 nc 12 ami 13 gnd 14 gnd 15 rst 16 sdio 17 sclk 18 xtalo 19 xtali 20 vdd1 21 vdd2 22 dbyp 23 rout/nc 24 lout/aout u1 c1 0.1u r27 100r r33 20k 1% r35 20k 1% r36 33k 1% c13 47u r43 30k 1% r44 47k 1% c4 4.7u c7 4.7u y1 32.768khz c28 22p c29 22p r3 10k ant2 ba nd [1] lna_en [1] lna_en [1] ba nd [1] tune1 [1] tune1 [1] reset vcc vcc vcc irq sclk sdio vcc lout rout
AN602 12 rev. 0.3 3.4. si4822/26/40/44 application circ uits: slide switch select band and use default band property figure 7shows an application circuit th at uses a slide switch for band select ion. in this example, the host mcu cannot change those band properties already fixed in the default band definition, as stated in section 2.1, it can only define the band properties which are not fixed in the default band definition, such as softmute property, etc. for more details, refer to ?an610: si48xx atdd programmi ng guide?. the two key points to ensure si4822/26/40/ 44 works properly are as follows: 1. add pull-up resistor r42 of 10 k ? to pin 1 lna_en. 2. pin 5 band is connected to slide switch. figure 7. si4822/26/40/44 applications circuit: slide switch select band and use default band property fm1 (87mhz - 108mhz) fm5 (64mhz - 87mhz) am1 (520khz - 1710khz) si4822/26/40/44 fm4(76mhz - 90mhz) sw1 (5.6mhz - 6.4mhz) sw3(6.8mhz - 7.6mhz) sw5(9.2mhz - 10.0mhz) sw7(11.45mhz - 12.25mhz) sw9 (13.4mhz - 14.2mhz) sw11 (15mhz - 15.9mhz) sw13 (17.1mhz - 18mhz) sw15 (21.2mhz - 22mhz) si4826/44 only si4826/44 only fm/sw to host mcu optional to host mcu (for si4822/26, pin23 is nc) (for si4822/26, pin24 is aout) 12 3 4 5 6 7 8 9 10 11 12 13 s2 r15 20k 1% r10 20k 1% r12 20k 1% r11 20k 1% r14 20k 1% r9 20k 1% r7 20k 1% r8 50k 1% r28 40k 1% r29 120k 1% l2 270nh c19 0.1u c15 4.7u vr1 100k 10% c6 0.1u r6 100k c5 0.47u q1 2sc9018 r31 1k r32 10r c30 33n c33 10p r41 120k c31 33n b6 2.5k/100m c36 0.47u ant1 mw ferrite antenna r34 100k c34 33p 1 lna_en 2 irq 3 tune1 4 tune2 5 ba nd 6 nc 7 nc 8 fmi 9 rfgnd 10 nc 11 nc 12 ami 13 gnd 14 gnd 15 rst 16 sdio 17 sclk 18 xtalo 19 xtali 20 vdd1 21 vdd2 22 dbyp 23 rout/nc 24 lout/aout u1 c1 0.1u r27 100r r33 20k 1% r35 20k 1% r36 33k 1% c13 47u r43 30k 1% r44 47k 1% c4 4.7u c7 4.7u y1 32.768khz c28 22p c29 22p r3 10k r42 10k ant2 ba nd [1] lna_en [1] lna_en [1] ba nd [1] tune1 [1] tune1 [1] reset vcc vcc vcc irq sclk sdio vcc lout rout vcc
AN602 rev. 0.3 13 3.5. si4827 applicati on circuit: host mcu to select radio band figure 8 shows the si4827 application circuit that the host m cu uses to select radio band. in this application, the host mcu sends commands to the si4827 to select the desired band. setting the band property by mcu or using the tuner default band property is determined by host mcu. setting the band property by mcu means that the host mcu can set the band property, such as band top frequency point and bottom frequency point, de-emphasis, am tuning spacing, etc. using the tuner default band property means that the mcu cannot define those band properties already fixed in the default band definition, as stated in section ?2.1. si4822 /26/27/40/44 default band definition?. the host mcu can only define the band properties which are not fixed in the default band definition, such as softmute property, etc. for more details, refer to application note, "an610: si48xx atdd programming guide". the key point to ensure the si4827 works properly is t hat pin 4 band is connected to it's power supply v cc directly. figure 8. si4827 application circuit: host mcu select band ?
AN602 14 rev. 0.3 3.6. si4827 applicat ion circuit: slide switch select band figure 9 shows the si4827 application circuit in which a slide switch is used for band selection. for the band selection method using slide switch and resistors ladder, re fer to section.?2.2. default band selection?. setting the band property by mcu or using the tuner defau lt band property is determined by host mcu. when setting the band property by mcu, the user c an select any default band an d the mcu will re-define the band's property according to the design requirement. th e mcu can only re-define the selected band's property, it cannot change an fm band to an am or sw band, and vice versa. when using the tuner default band property, the host mc u cannot change those band properties already fixed in the default band definition, as stated in section ?2.1. si 4822/26/27/40/44 default band de finition?, it can only define the band properties which are not fixed in the default band definition, such as softmute property, etc. for more details, refer to application note, "an610: si48xx atdd programming guide". the key point to ensure the si4827 works properly is that pin 4 band is connected to slide switch. figure 9. si4827 application circuit: slide switch select band ?
AN602 rev. 0.3 15 3.7. si4822/26/27/40/ 44 bill of materials table 6. si4822/26/40/44 applications circuit: host mcu select band and set band property component(s) value/description supplier c1,c6,c19 supply bypass capacitor, 0.1 f, 20%, z5u/x7r murata c5 capacitor, 0.47 f, 20%, z5u/x7r murata c34 rf coupling capacitors, 33 pf, 5%, cog murata c4,c7,c15 capacitor 4.7 f, 20%, z5u/x7r murata c13 capacitor 47 f, 20%, z5u/x7r murata r27 resistor, 100 ? , 5% venkel r6 resistor, 100 k ? , 5% venkel r3 resistor, 10 k ? , 5% venkel u1 si4822/26/40/44 am/fm/sw anal og tune digital display radio tuner silicon laboratories l2 inductor 270 nh murata ant1 mw ferrite antenna 220 h. jiaxin electronics ant2 whip antenna various vr1 variable resistor (pot), 100 k ? , 10% changtaier si4826/44 only c36 capacitor, 0.47 f, 20%, z5u/x7r murata c33 capacitor, 10 pf, 5%, cog murata c30-31 capacitor, 33 nf, 5%, cog murata b6 ferrite bead,2.5 k/100 mhz. murata q1 rf transistor, 2sc9018. etc r34 resistor, 100 k ? , 5% venkel r41 resistor, 120 k ? , 5% venkel r32 resistor, 10 ? , 5% venkel r31 resistor, 1 k ? , 5% venkel optional c28, c29 crystal load capacitors, 22 pf, 5%, cog (optio nal: for crystal oscillator option) murata y1 32.768 khz crystal (optional: fo r crystal oscillator option) epson
AN602 16 rev. 0.3 table 7. si4822/26/40/44 applications circuit: mcu select default band and use default band property component(s) value/description supplier c1,c6,c19 supply bypass capacito r, 0.1 f, 20%, z5u/x7r murata c5 capacitor, 0.47 f, 20%, z5u/x7r murata c34 rf coupling capacitors, 33 pf, 5%, cog murata c4,c7,c15 capacitor 4.7 f, 20%, z5u/x7r murata c13 capacitor 47 f, 20%, z5u/x7r murata r27 resistor, 100 ? , 5% venkel r6 resistor, 100 k ? , 5% venkel r3, r42 resistor, 10 k ? , 5% venkel u1 si4822/26/40/44 am/fm/sw anal og tune digital display radio tuner silicon laboratories l2 inductor 270 nh murata ant1 mw ferrite antenna 220 h. jiaxin electronics ant2 whip antenna various vr1 variable resistor (pot), 100 k ? , 10% changtaier si4826/44 only c36 capacitor, 0.47 f, 20%, z5u/x7r murata c33 capacitor, 10 pf, 5%, cog murata c30-31 capacitor, 33 nf, 5%, cog murata b6 ferrite bead, 2.5 k/100 mhz murata q1 rf transistor, 2sc9018. etc r34 resistor, 100 k ? , 5% venkel r41 resistor, 120 k ? , 5% venkel r32 resistor, 10 ? , 5% venkel r31 resistor, 1 k ? , 5% venkel optional c28, c29 crystal load capacitors, 22 pf, 5%, cog (optional: for crystal oscillator option) murata y1 32.768 khz crystal (optional: fo r crystal oscillator option) epson
AN602 rev. 0.3 17 table 8. si4822/26/40/44 application circuits: slide switch select band and mcu re-define band property component(s) value/description supplier c1,c6,c19 supply bypass capacitor, 0.1 f, 20%, z5u/x7r murata c5 capacitor, 0.47 f, 20%, z5u/x7r murata c34 rf coupling capacitors, 33 pf, 5%, cog murata c4,c7,c15 capacitor 4.7 f, 20%, z5u/x7r murata c13 capacitor 47 f, 20%, z5u/x7r murata r27 resistor, 100 ? , 5% venkel r6 resistor, 100 k ? , 5% venkel r3 resistor, 10 k ? , 5% venkel r7,r33 band switching resistor, 20 k ? , 1% venkel r28 band switching resistor, 40 k ? , 1% venkel r29 band switching resistor, 120 k ? , 1% venkel r44 band switching resistor, 47 k ? , 1% venkel r43 band switching resistor, 30 k ? , 1% venkel r36 band switching resistor, 33 k ? , 1% venkel u1 si4822/26/40/44 am/fm/sw analog tune digital display radio tuner silicon laboratories l2 inductor 270 nh murata ant1 mw ferrite antenna 220 h jiaxin electronics ant2 whip antenna various vr1 variable resistor (pot), 100 k ? , 10% changtaier s2 slide switch shengda si4826/44 only c36 capacitor, 0.47 f, 20%, z5u/x7r murata c33 capacitor, 10 pf, 5%, cog murata c30-31 capacitor, 33 nf, 5%, cog murata b6 ferrite bead, 2.5 k/100 mhz murata q1 rf transistor, 2sc9018. etc r34 resistor, 100 k ? , 5% venkel r41 resistor, 120 k ? , 5% venkel r32 resistor, 10 ? , 5% venkel
AN602 18 rev. 0.3 r31 resistor, 1 k ? , 5% venkel r9-12, r14-15, r35 band switching resistor, 20 k ? , 1% venkel r8 band switching resistor, 50 k ? , 1% venkel optional c28, c29 crystal load capacitor, 22 pf, 5%, cog (optional: for crystal oscillator option) murata y1 32.768 khz crystal (optional: fo r crystal oscillator option) epson table 9. si4822/26/40/44 application circuits: slide switch select band and use default band property component(s) value/description supplier c1,c6,c19 supply bypass capacitor, 0.1 f, 20%, z5u/x7r murata c5 capacitor, 0.47 f, 20%, z5u/x7r murata c34 rf coupling capacitors, 33 pf, 5%, cog murata c4,c7,c15 capacitor 4.7 f, 20%, z5u/x7r murata c13 capacitor 47 f, 20%, z5u/x7r murata r27 resistor, 100 ? , 5% venkel r6 resistor, 100 k ? , 5% venkel r3, r42 resistor, 10 k ? , 5% venkel r7,r33 band switching resistor, 20 k ? , 1% venkel r28 band switching resistor, 40 k ? , 1% venkel r29 band switching resistor, 120 k ? , 1% venkel r44 band switching resistor, 47 k ? , 1% venkel r43 band switching resistor, 30 k ? , 1% venkel r36 band switching resistor, 33 k ? , 1% venkel u1 si4822/26/40/44 am/fm/sw analog tune digital display radio tuner silicon laboratories l2 inductor 270 nh murata ant1 mw ferrite antenna 220 h jiaxin electronics ant2 whip antenna various table 8. si4822/26/40/44 application circuits: slide switch select band and mcu re-define band property (continued)
AN602 rev. 0.3 19 vr1 variable resistor (pot), 100 k ? , 10% changtaier s2 slide switch shengda si4826/44 only c36 capacitor, 0.47 f, 20%, z5u/x7r murata c33 capacitor, 10 pf, 5%, cog murata c30-31 capacitor, 33 nf, 5%, cog murata b6 ferrite bead, 2.5 k/100 mhz murata q1 rf transistor, 2sc9018 etc r34 resistor, 100 k ? , 5% venkel r41 resistor, 120 k ? , 5% venkel r32 resistor, 10 ? , 5% venkel r31 resistor, 1 k ? , 5% venkel r9-12, r14-15, r35 band switching resistor, 20 k ? , 1% venkel r8 band switching resistor, 50 k ? , 1% venkel optional c28, c29 crystal load capacitor, 22 pf, 5%, cog (optional: for crystal oscillator option) murata y1 32.768 khz crystal (optional: fo r crystal oscillator option) epson table 9. si4822/26/40/44 application circuits: slide switch select band and use default band property (continued) component(s) value/description supplier
AN602 20 rev. 0.3 table 10. si4827 application circuit: mcu select band component(s) value/description supplier c1,c6,c19 supply bypass capacitor, 0.1 f, 20%, z5u/x7r murata c5,c36 capacitor, 0.47 f, 20%, z5u/x7r murata c34 rf coupling capacitors, 33 pf, 5%, cog murata c7,c15 capacitor 4.7 f, 20%, z5u/x7r murata c13 capacitor 47 f, 20%, z5u/x7r murata r27 resistor, 100 ? , 5% venkel r6 r34 resistor, 100 k ? , 5% venkel r3 resistor, 10 k ? , 5% venkel u1 si4827-a am/fm/sw analog tune digital display radio tune r silicon laboratories l2 inductor 270 nh murata ant1 mw ferrite antenna 220 h jiaxin electronics ant2 whip antenna various vr1 variable resistor (pot), 100 k ? , 10% changtaier c33 capacitor, 10 pf, 5%, cog murata c30-31 capacitor, 33 nf, 5%, cog murata b6 ferrite bead,2.5k/100 mhz murata q1 rf transistor, 2sc9018 etc r41 resistor, 120 k ? , 5% venkel r32 resistor, 10 ? , 5% venkel r31 resistor, 1 k ? , 5% venkel optional c28, c29 crystal load ca pacitors, 22 pf, 5%, cog (optional: for crystal oscillator option) murata y1 32.768 khz crystal (optional: fo r crystal oscillator option) epson
AN602 rev. 0.3 21 table 11. si4827 application circuit: slide switch select band component(s) value/description supplier c1,c6,c19 supply bypass capacitor, 0.1 f, 20%, z5u/x7r murata c5,c36 capacitor, 0.47 f, 20%, z5u/x7r murata c34 rf coupling capacitors, 33 pf, 5%, cog murata c7,c15 capacitor 4.7 f, 20%, z5u/x7r murata c13 capacitor 47 f, 20%, z5u/x7r murata r27 resistor, 100 ? , 5% venkel r6 r34 resistor, 100 k ? , 5% venkel r3 resistor, 10 k ? , 5% venkel u1 si4827-a am/fm/sw analog tune digital display radio tuner silicon laboratories l2 inductor 270 nh murata ant1 mw ferrite antenna 220 h jiaxin electronics ant2 whip antenna various vr1 variable resistor (pot), 100 k ? , 10% changtaier c33 capacitor, 10 pf, 5%, cog murata c30-31 capacitor, 33 nf, 5%, cog murata b6 ferrite bead, 2.5 k/100 mhz murata q1 rf transistor, 2sc9018 etc r41 resistor, 120 k ? , 5% venkel r32 resistor, 10 ? , 5% venkel r31 resistor, 1 k ? , 5% venkel optional c28, c29 crystal load capacitors, 22 pf, 5%, cog (optional: for crystal oscillator option) murata y1 32.768 khz crystal (o ptional: for crystal oscillator option) epson
AN602 22 rev. 0.3 3.8. si4822/26/27/40/44 pcb layout guidelines ?? 1-layer pcb is used for si4822/26/27/40/44 ?? gnd routed by large plane ?? power routed with traces ?? 0402 component size or larger ?? 10 mil traces width ?? 20 mil trace spacing ?? 15 mil component spacing ?? keep the am ferrite loop at least 5 cm away from the tuner chip (recommended) ?? keep the am ferrite loop antenna away from the m cu, audio amp, and other circuits which have am interference place v dd1 /v dd2 bypass capacitor c6, c15 as close as possible to the supply (pin20/pin 21) and dbyp (pin 22). do not connect the dbyp (p in 22) to the board gnd. place the crystal as close to xtalo (pin18) and xtali (pin19) as possible, and make the loop area of xtalo trace and xtali trace as small as possible. route all gnd (including rfgnd) pi ns to the gnd plane underneath the chip. try to create a large gnd plane underneath and around the chip. do not route pin 6 and 7. these pins must be left floating to guarantee proper operation. keep the tune1 and tune2 traces away from pin 6 and pi n 7, route tune1 and tune2 traces in parallel and the same way. place c1, c13 as close to pin3 tune1 as possible. for si4822/26, do not route pin 23, leave it floating to guarantee proper operation. try to refer to the si4840/44 pcb layout example as much as possible when doing si4822/26/27 pcb layout. figure 10. si4840/44 pcb layout example
AN602 rev. 0.3 23 4. headphone antenna for fm receive the si4822/26/27/40/44 fm receiver component supports a headphone antenna interface through the fmi pin. a headphone antenna with a length between 1.1 and 1.45 m suits the fm applicatio n very well because it is approximately half the fm wave length (fm wavelength is ~3 m). 4.1. headphone antenna design a typical headphone cable will contain th ree or more conductors. the left and right audio channels are driven by a headphone amplifier onto left and right audio conductors and the common audio conductor is used for the audio return path and fm antenna. additional conductors may be used for microphone audio, switching, or other functions, and in some app lications the fm antenna will be a separate conductor within the cable. a representation of a typical application is shown in figure 11. figure 11. typical headphone antenna application
AN602 24 rev. 0.3 4.2. headphone antenna schematic figure 12. headphone antenna schematic the headphone antenna implementation requires components l match , c4, f1, and f2 for a minimal implementation. the esd protection diodes and headpho ne amplifier components are system components that will be required for proper implementation of any tuner. inductor l match is selected to maximize the voltage gain across the fm band. l match should be selected with a q of 15 or greater at 100 mhz and minimal dc resistance. ac-coupling capacitor c4 is used to remove a dc offset on the fmi input. this capacitor must be chosen to be large enough to cause negligible loss with an lna input capacitance of 4 to 6 pf. the recommended value is 100 pf to 1nf. ferrite beads f1 and f2 provide a low-impedance a udio path and high-impedance rf path between the headphone amplifier and the headphone. ferrite beads shou ld be placed on each antenna conductor connected to nodes other than the fmip, such as left and right audio, microphone audio, switching, etc. in the example shown in figure 12, these nodes are the left and right audio conductors. ferrite beads should be 2.5 k ? or greater at 100 mhz, such as the murata blm18bd252sn1. high resistance at 100 mhz is desirable to maximize r shunt and, therefore, r p . refer to ?an383: si47 xxantenna, schematic, and layout guidelines?, appendix a, for a complete description of r shunt , r p , etc. esd diodes d1, d2, and d3 are recommended if design requirements exceed the esd rating of the headphone amplifier and the si4822/26/40/44. diodes should be chosen with no more than 1 pf parasitic capacitance, such as the california micro devices cm1210. diode capa citance should be minimized to minimize c shunt and, therefore, c p . if d1 and d2 must be chosen with a capacitance greate r than 1 pf, they should be placed between the ferrite beads f1 and f2 and the headphone amplifier to minimize c shunt . this placement will, however, reduce the effectiveness of the esd protection devices. diode d3 may not be relocated and must therefore have a capacitance less than 1 pf. note that each diode packag e contains two devices to pr otect against positive and negative polarity esd events. c9 and c10 are 125 f ac coupling capacitors required when the audio amplifier does not have a common mode output voltage and the audio output is swinging above and below ground. optional bleed resistors r5 and r6 may be desirable to discharge the ac-coupling capacitors when the headphone cable is removed.
AN602 rev. 0.3 25 optional rf shunt capacitors c5 and c6 may be placed on the left and right audio traces at the headphone amplifier output to reduce the level of digital noise passed to the antenna. the recommended value is 100 pf or greater; however, the designer should confirm that the head phone amplifier is capable of driving the selected shunt capacitance. this schematic example uses the na tional semiconductor lm4910 headphone amplifier. passive components r1- r4 and c7-c8 are required for the lm4910 headphone amplif ier as described in the lm4910 data sheet. the gain of the right and left amplifiers is -r3/r1 and -r4/r2, respectively. these gains can be adjusted by changing the values of resistors r3 and r4. as a general guide, gain between 0.6 and 1.0 is recommended for the headphone amplifier, depending on the gain of the headphone elements. capacitors c7 and c8 are ac-coupling capacitors required for the lm4910 interface. these capacitors, in conjunction with resistors r1 and r2, create a high-pass filter that sets the audio amplifier' s lower frequency limit. the high-pass corner frequencies for the right and left amplifiers are: with the specified bom components, the corner frequen cy of the headphone amplifie r is approximately 20 hz. capacitor c1 is the supply bypass capacitor for the audio amplifier. the lm4910 can also be shut down by applying a logic low voltage to the number 3 pin. the ma ximum logic low level is 0.4 v and the minimum logic high level is 1.5 v. the bill of materials for the typical ap plication schematic shown in figure 12 is provided in t able 12. note that manufacturer is not critical for resistors and capacitors. 4.3. headphone antenna bill of materials table 12. headphone antenna bill of materials designator description lmatch ind, 0603, sm, 270 nh, murata, lqw18anr27j00d c4 ac coupling cap, sm, 0402, x7r, 100 pf d1, d2, d3 ic, sm, esd diod e, sot23-3, california micro devices, cm1210-01st u3 ic, sm, headphone amp, national semiconductor, lm4910ma r1, r2, r3, r4 res, sm, 0603, 20 k ? c7, c8 cap, sm, 0603, 0.39uf, x7r c5, c6 cap, sm, 0402, c0g, 100 pf r5, r6 res, sm, 0603, 100 k ? f1, f2 ferrite bead, sm, 0603, 2.5 k ? , murata, blm18bd252sn1d c1 cap, sm, 0402, x7r, 0.1 f r7 res, sm, 0402, 10 k ? f cright 1 2 ? r1 ? c7 ? ----------------------------------- , f cleft 1 2 ? r2 c8 ? ? ----------------------------------- ==
AN602 26 rev. 0.3 4.4. headphone antenna layout to minimize inductive and capacitive coupling, inductor l match and headphone jack j24 should be placed together and as far from noise source s such as clocks and digital circuits as possible. l match should be placed near the headphone connector to keep audio currents away from the chip. to minimize c shunt and c p , place ferrite beads f1 and f2 as close as possible to the headphone connector. to maximize esd protection diode effe ctiveness, place diodes d1, d2, and d3 as close as possible to the headphone connector. if capacitance larger than 1 pf is required for d1 and d2, both components should be placed between fb1 and fb2 and the headphone amplifier to minimize c shunt . place the chip as close as possible to the headpho ne connector to minimize antenna trace capacitance, cpcbant. keep the trace length short and narrow and as far above the reference plane as possible, restrict the trace to a microstrip topology (trace routes on the top or bottom pcb layers only), mi nimize trace vias, and relieve ground fill on the trace layer. note that minimizing capacitance has the effect of maximizing characteristic impedance. it is not ne cessary to design for 50 ? transmission lines. to reduce the level of digital noise passed to the antenna, rf shunt capacitors c5 and c6 may be placed on the left and right audio traces close to the headphone ampl ifier audio output pins. the recommended value is 100 pf or greater, however, the designer should confirm that the headphone amplifier is capable of driving the selected shunt capacitance. 4.5. headphone antenna design checklist ?? select an antenna length of 1.1 to 1.45 m. ?? select matching inductor l match to maximize signal strength across the fm band. ?? select matching inductor l match with a q of 15 or greater at 100 mhz and minimal dc resistance. ?? place inductor l match and headphone connector together and as far from potential noise sources as possible to reduce capacitive and inductive coupling. ?? place the chip close to the headphone connector to mini mize antenna trace length. minimizing trace length reduces cp and the possibility for i nductive and capacitive coupling into the antenna by noise sources. this recommendation must be followed for optimal device performance. ?? select ferrite beads f1-f2 with 2.5 k ? or greater resistance at 100 mhz to maximize rshunt and, therefore, rp. ?? place ferrite beads f1-f2 close to the headphone connector. ?? select esd diodes d1-d3 with minimum capacitance. ?? place esd diodes d1-d3 as close as possible to th e headphone connector for maximum effectiveness. ?? place optional rf shunt capacitors near the headphone amplifier?s left and right audio output pins to reduce the level of digital noise passed to the antenna.
AN602 rev. 0.3 27 5. whip antenna for fm receiver a whip antenna is a typical monopole antenna. 5.1. fm whip antenna design a whip antenna is a monopole antenna with a stiff but flex ible wire mounted ve rtically with one end adjacent to the ground plane. there are various types of whip antennas including long non-telescopic metal whip antennas, telescopic metal whip antennas, and rubber whip antennas. figure 13 shows the telescopic whip antenna. figure 13. telescopic whip antennas the whip antenna is capacitive, and its output capaci tance depends on the length of the antenna (maximum length ~56 cm). at 56 cm length, the capacitance of the whip antenna ranges from 18 to 32 pf for the us fm band. the antenna capacitance is about 22 pf in the center of the us fm band (98 mhz). 5.2. fm whip antenna schematic figure 14. fm whip antenna schematic l1 (56 nh) is the matching inductor and it combin es with the antenna impedance and the fmi impedance to resonate in the fm band. c5 (1 nf) is the ac coupling cap going to the fmi pin. u3 is a required esd diode since the antenna is expose d. the diode should be chosen with no more than 1 pf parasitic capacitance, such as t he california micro device cm1213.
AN602 28 rev. 0.3 5.3. fm whip antenna bill of materials 5.4. fm whip antenna layout place the chip as close as possible to the whip antenna. this will minimize the trace le ngth between the device and whip antenna which in turn will minimize parasitic capacitance and th e possibility of noise co upling. place inductor l1 and the antenna connector together and as far from pot ential noise sources as possi ble. place the ac coupling capacitor c5 as close to the fmi pin as possible. place esd diode u3 as close as possible to the whip antenna input connector for maximum effectiveness. 5.5. fm whip antenna design checklist ?? maximize whip antenna length for optimal performance. ?? select matching inductor l1 with a q of 15 or greater at 100 mhz and minimal dc resistance. ?? select l1 inductor value to maximize resonance gai n from fm frequency (6 4 mhz) to fm frequency (109 mhz). ?? place l1 and whip antenna close together and as far fr om potential noise sources as possible to reduce capacitive and inductive coupling. ?? place the chip as close as possible to the whip antenna to minimize the antenna tr ace length. this reduces parasitic capacitance and hence reduces coupling into the antenna by noise sources. this recommendation must be followed for optimal device performance. ?? place esd u3 as close as possible to the whip antenna for maximum effectiveness. ?? select esd diode u3 with minimum capacitance. ?? place the ac coupling capacitor, c5, as close to the fmi pin as possible. table 13. fm whip antenna bill of materials designator description wip_antenna whip antenna l1 tuning inductor, 0603, sm, 56 nh, murata, lqw18an56nj00d c5 ac coupling capacitor, 1nf, 10%, cog u3 ic, sm, esd diode, sot23-3, california micro devices, cm1213-01st
AN602 rev. 0.3 29 6. ferrite loop an tenna for am receive there are two types of antennas that will work well for an am receiv er: a ferrite loop antenna or an air loop antenna. a ferrite loop antenna can be placed internally on the device or externally to the device with a wire connection. when the ferrite loop antenn a is placed internally on the device, it is more susceptible to picking up any noise within the device. when the ferrite loop antenna is placed outside a device, e.g., at the end of an extension cable, it is less prone to device noise activity and may result in better am reception. 6.1. ferrite loop antenna design figure 15 shows an example of ferrite loop antennas. the le ft figure is the standard size ferrite loop antenna. it is usually used in products with a lot of space, such as deskt op radios. the right figure is the miniature size of the loop antenna. it is usually used in small products where space is at a premium, such as cell phones. if possible, use the standard size ferrite loop antenna as it has a better sensitivity than the miniature one. figure 15. standard and miniature ferrite loop antennas a loop antenna with a ferrite inside should be designed such that the inductance of the ferrite loop is between 180 and 450 h for the si4822/26/27/40/44 am receiver. table 14 lists the recommended ferrite loop ante nna for the si4822/26/27/40/44 am receiver. the following is the vendor information for the ferrite loop antennas: jiaxin electronics shenzhen sales office email: sales@firstantenna.com web: www.firstantenna.com table 14. recommended ferrite loop antenna part # diameter length turns ui type application sl8x50mw70t 8 mm 50 mm 70 400 mn-zn desktop radios sl4x30mw100t 4 mm 30 mm 100 300 ni-zn portable radios (mp3, cell, gps) sl3x30mw105t 3 mm 30 mm 105 300 ni-zn sl3x25mw100t 3 mm 25 mm 110 300 ni-an sl5x7x100mw70t 5 x 7 mm 100 mm 70 400 mn-zn desktop radios
AN602 30 rev. 0.3 6.2. ferrite loop antenna schematic figure 16. am ferrite loop antenna schematic c1 is the ac coupling cap going to the ami pin and its value should be 0.47 f. d1 is an optional esd diode if there is an exposed pad going to the ami pin. 6.3. ferrite loop antenna bill of materials table 15. ferrite loop antenna bill of materials designator description note ant1 ferrite loop antenna, 180~450 h c1 ac coupling capacitor, 0.47 f, 10%, z5u/x7r d1 esd diode, ic, sm, sot23-3, california micro devices, cm1213-01st optional; only needed if there is any exposed pad going to the ami pin.
AN602 rev. 0.3 31 6.4. ferrite loop antenna layout place the chip as close as possible to the ferrite loop ant enna feedline. this will minimize the trace going to the ferrite antenna, which in tu rn will minimize parasitic capacitance and also will minimize the possibility of noise sources coupling to the trace. the placement of the am antenna is critical, since am is susceptible to noise sources causing interference in the am band. noise sources can come from clock signals, sw itching power supply, and digital activities (e.g., mcu). when the am input is interfaced to a ferrite loop stick antenna, the placement of the ferrite loop stick antenna is critical to minimize inductive coupling. place the ferrite loop stick antenna as far away from interference sources as possible. in particular, make sure th e ferrite loop stick antenn a is away from signals on the pcb and away from even the i/o signals of the chip. do not route any signal u nder or near the ferrite loop stick. route digital traces in between ground plane for best performance. if that is not po ssible, route digital traces on the opposite side of the chip. this will minimize capacitive coup ling between the plane (s) and the antenna. to tune correctly, the total capacitance seen at the ami input needs to be minimized and kept under a certain value. the total acceptable capacitance depends on the inductance seen by the chip at its am input. the acceptable capacitance at the am input can be calcul ated using the formula shown in equation 2 equation 2. expected total capacitance at ami where: c to ta l = total capacitance at the ami input l effective = effective inductance at the ami input f max = highest frequency in am band the total allowable capacitance, when in terfacing a ferrite loop stick antenna, is the effective capacitance resulting from the ami input pin, the capacitance from the pcb, and the capacitance from the ferrite loop stick antenna. the inductance seen at the ami in this ca se is primarily the inductance of the ferrite loop stick antenna. the total allowable capacitance in the case of an air loop antenna is the effective capacitance resulting from the ami input pin, the capacitance of the pcb, the capacitance of the transformer, and the capacitance of the air loop antenna. the inductance in this case should also take all the elem ents of the circuit into account. the input capacitance of the ami input is 8 pf. the formula shown in equation 2 gives a total capacitance of 28 pf when a 300 h ferrite loop stick antenna is used for an am band with 10 khz spacing, where the highest frequency in the band is 1750 khz. 6.5. ferrite loop an tenna design checklist ?? place the chip as close as possible to the ferrite loop antenna feedline to minimize parasitic capacitance and the possibility of noise coupling. ?? place the ferrite loop stick antenna away from any sour ces of interference and even away from the i/o signals of the chip. please make sure that the am antenna is as fa r away as possible from circuits that switch at a rate which falls in the am band (504?1750 khz). ?? keep the am ferrite loop antenna at least 5 cm away from the tuner chip (recommended). ?? place optional component d1 if the antenna is exposed. ?? select esd diode d1 with minimum capacitance. ?? do not place any ground plane under the ferrite loop stick antenna if the ferrite loop stick antenna is mounted on the pcb. the recommended ground separation is 1/4 inch or the width of the ferrite. ?? route traces from the ferrite loop stick connectors to the ami input via the ac coupling cap c1 such that the capacitance from the traces and the pads is minimized. c total 1 2 ? f max ?? 2 l effective -------------------------------------------------- =
AN602 32 rev. 0.3 7. air loop antenna for am an air loop antenna is an external am antenna (bec ause of its large size) typically found on home audio equipment. an air loop antenna is placed external to the product enclosure maki ng it more immune to system noise sources. it also will have a better sensitivity compared to a ferrite loop antenna. 7.1. air loop antenna design figure 17 shows an example of an air loop antenna. figure 17. air loop antenna unlike a ferrite loop, an air loop ante nna will have a smaller equiva lent inductance because of the absence of ferrite material. a typical inductance is on the order of 10 to 20 h. therefore, in order to interface with the air loop antenna properly, a transformer is required to raise the inductance into the 180 to 450 h range. t1 is the transformer to raise the inductance to within 18 0 to 450 h range. a simple fo rmula to use is as follows: equation 3. typically, a transformer with a turn ratio of 1:5 to 1:7 is good for an air loop antenna of 10 to 20 h to bring the inductance within the 180 to 450 h range. choose a high-q transformer with a coupling coefficient as close to 1 as possible and use a multiple strands litz wire for the transformer winding to reduce the skin effect. all of this will ensure that the transformer will be a low loss transformer. finally, consider using a shielded enclosure to house the transformer or a toroidal shape core to prevent noise pickup from interfering sources. a few recommended transformers are listed in table 16. l equivalent n 2 l airloop =
AN602 rev. 0.3 33 the following is the vendor information for the above transformer: vendor #1: jiaxin electronics shenzhen sales office email: sales@firstantenna.com web: www.firstantenna.com vendor #2: umec usa, inc. website: www.umec-usa.com www.umec.com.tw table 16. recommended transformers transformer 1 transfo rmer 2 transformer 3 vendor jiaxin electronics umec umec part number sl9x5x4mwtf1 tg-utb01527s tg-utb01526 type surface mount surface mount through hole primary coil turns (l1) 12t 10t 10t secondary coil turns (l2) 70t 55t 58t wire gauge ulsa / 0.07 mm x 3 n/a n/a inductance (l2) 380 h 10% @ 796 khz 184 h min, 245 h typ @ 100 khz 179 h min, 263 h typ @ 100 khz q 130 50 75
AN602 34 rev. 0.3 7.2. air loop antenna schematic figure 18. am air loop antenna schematic c1 is the ac coupling cap going to the ami pin and its value should be 0.47 f. d1 is a required esd diode since the antenna is exposed. 7.3. air loop antenna bill of materials 7.4. air loop antenna layout place the chip and the transf ormer as close as possible to the air loop antenna feedline. th is will minimize the trace going to the air loop antenna, which in turn will minimize parasitic capacitance and the possibility of noise coupling. when an air loop antenna with a transformer is used with the si4822/26/27/40/44, mi nimize inductive coupling by making sure that the transformer is pl aced away from all sources of interf erence. keep the transformer away from signals on the pcb and away from even the i/o signals of the si4822/26/27/40/44. do not route any signals under or near the transformer. use a shielded transformer if possible. 7.5. air loop antenna design checklist ?? select a shielded transformer or a toroidal shape tran sformer to prevent noise pickup from interfering sources ?? select a high-q transformer with coupling coefficient as close to 1 as possible ?? use multiple strands litz wir e for the transformer winding ?? place the transformer away from any sources of interference and even away from the i/o signals of the chip. ensure that the am antenna is as far away as possibl e from circuits that switch at a rate which falls in the am band (504 to 1750 khz). ?? route traces from the transformer to the ami input via the ac coupling cap c1 such that the capacitance from the traces and the pads is minimized. ?? select esd diode d1 with minimum capacitance. table 17. air loop antenna bill of materials designator description loop_antenna air loop antenna t1 transformer, 1:6 turns ratio c1 ac coupling capacitor, 0.47 f, 10%, z5u/x7r d1 esd diode, ic, sm, sot23-3, california micro devices, cm1213-01st
AN602 rev. 0.3 35 8. whip antenna for sw receiver sw reception usually uses whip antennas, the same as fm. 8.1. sw whip antenna design a whip antenna is a monopole antenna with a stiff but flex ible wire mounted ve rtically with one end adjacent to the ground plane. figure 19 shows the telescopic whip antenna. figure 19. telescopic whip antenna for sw 8.2. sw whip antenna schematic figure 20. sw whip antenna schematic q1 2sc9018 is a low noise rf transistor and it constitu tes a lna to amplify the sw signal coming from the whip antenna. c30 (33 nf) is the ac coupling cap between whip antenna and lna input. c33 (0.47 f) is the ac coupling cap going to the ami pin. r31, r41 are bias resistors of the transistor.
AN602 36 rev. 0.3 8.3. sw whip antenn a bill of materials 8.4. sw whip antenna layout place the chip and 2sc9018 as close as possible to the wh ip antenna feedline. this wi ll minimize the trace going to the whip antenna, which in turn will minimize parasitic capacitance and also will minimize the possibility of noise sources coupling to the trace. 8.5. sw whip antenna design checklist ?? maximize whip antenna length for optimal performance. ?? place q1 and whip antenna close together and as far from potential noise sources as possible to reduce capacitive and inductive coupling. ?? place the chip as close as possible to the whip antenna to minimize the antenna tr ace length. this reduces parasitic capacitance and hence reduces coupling into the antenna by noise sources. this recommendation must be followed for optimal device performance. ?? place the ac coupling capacitor c33, as close to the ami pin as possible. table 18. sw whip antenna bill of materials designator description whip_antenna whip antenna q1 low noise rf transistor, 2sc9018 c30 ac coupling capacitor, 33 nf, 10%, cog c33 coupling capacitor, 0.47 f, 20%, z5u/x7r r31 resistor, 1 k, 5% r41 resistor, 200 k, 5%
AN602 rev. 0.3 37 d ocument c hange l ist revision 0.2 to revision 0.3 ? updated "1.in troduction" ? updated "2.si4822/26/27/40/44 default frequency band definition and selection" ? added "3.5 si4827 application circuit: host mcu select radio band" ? added "3.6 si4827 applicat ion circuit: slide switch select radio band" ? added "table10.si44827 application circuit: host mcu select radio band" ? added "table11. si4827 application circuit: slide switch select radio band"
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