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not for new design this is information on a product still in production but not recommended for new designs. january 2009 rev 7 1/48 1 tda7461 car radio signal processor features high performance signal processor for car radio systems device includes audio processor, stereo decoder, noise blanker and multipath detector no external components required fully programmable via i 2 c bus low distortion low noise description the tda7461 is a high performance signal processor specifically designed for car radio applications. the device includes a complete audioprocessor and a stereo decoder with noise blanker, stereo blend and all signal processing functions necessary for state-of-the-art as well as future car radio systems. switched-capacitors design technique allows to obtain all these features without external components or adjustments. this means that higher quality and reliab ility walks alongside an overall cost saving. the csp is fully programmable by i 2 c bus interface allowing to customize key device parameters and especially filter characteristics. the bicmos process combined with the optimized signal processing assure low noise and low distortion performances. so-28 table 1. device summary order code package packing tda7461nd so-28 tube tda7461ndtr so-28 tape and reel E-TDA7461ND (1) 1. device in ecopack? package, see chapter 7: package information on page 46 . so-28 tube E-TDA7461NDtr (1) so-28 tape and reel www.st.com
contents tda7461 2/48 contents 1 block diagram and pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.1 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2 pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2 electrical specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.1 absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2 supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.3 esd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.4 thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.5 audio processor part feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.5.1 input multiplexer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.5.2 volume control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.5.3 bass control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.5.4 treble control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.5.5 speaker control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.5.6 mute function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.6 audio processor electric al characteristics . . . . . . . . . . . . . . . . . . . . . . . . 10 3 description of the audi o processor part . . . . . . . . . . . . . . . . . . . . . . . . 13 3.1 programmable input matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.1.1 how to find the right input configuration . . . . . . . . . . . . . . . . . . . . . . . . 14 3.1.2 input stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.1.3 autozero . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.2 mux output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.3 mixing stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3.1 loudness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3.2 softmute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.3.3 soft step volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.3.4 bass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.3.5 dc mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.3.6 treble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.3.7 speaker attenuator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
tda7461 contents 3/48 4 stereo decoder part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.1 stereo decoder feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.2 stereo decoder electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.3 noise blanker part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 4.4 multipath detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 4.5 description of stereo decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4.5.1 stereo decoder mute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4.5.2 input stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4.5.3 demodulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 4.5.4 de-emphasis and high cut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 4.5.5 pll and pilot tone detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 4.5.6 fieldstrength control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 4.5.7 level input and gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 4.5.8 stereo blend control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 4.5.9 high cut control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 4.6 functional description of the noise blanker . . . . . . . . . . . . . . . . . . . . . . . 29 4.6.1 trigger path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 4.6.2 automatic noise controlled threshold adjustment (atc) . . . . . . . . . . . . 30 4.6.3 automatic threshold control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 4.6.4 over deviation detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 4.7 functional description of the multipath detector . . . . . . . . . . . . . . . . . . . . 31 4.8 test mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 5i 2 c bus interface description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 5.1 interface protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 5.2 auto increment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 6 data byte specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 7 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 8 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
list of tables tda7461 4/48 list of tables table 1. device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 table 2. pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 table 3. absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 table 4. supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 table 5. thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 table 6. audio processor electrical characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 0 table 7. input and source programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 table 8. stereo decoder electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 0 table 9. noise blanker electrical characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 table 10. multipath detector electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 table 11. transmitted data (send mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 table 12. subaddress (receive mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 table 13. input selector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 table 14. loudness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 table 15. mute, beep and mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 table 16. volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 table 17. bass and treble attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 table 18. bass and treble filter characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 table 19. speaker attenuation (lf, lr, rf, rr) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 table 20. stereo decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 table 21. noise blanker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 table 22. field strength control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 table 23. configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 table 24. stereo decoder adjustment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 table 25. testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 table 26. document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
tda7461 list of figures 5/48 list of figures figure 1. block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 figure 2. pin connection (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 figure 3. input configuration tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 4. input stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 figure 5. loudness attenuation @ fc = 400 hz (second order) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 figure 6. loudness center frequency @ atten. = 15 db (second order) . . . . . . . . . . . . . . . . . . . . . . 16 figure 7. loudness attenuation = 15 db @ fc = 400 hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 figure 8. softmute timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 figure 9. soft step timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 figure 10. bass control @ fc = 80 hz, q = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 figure 11. bass center @ gain = 14 db, q = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 figure 12. bass quality factors @ gain = 14 db, fc = 80 hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 figure 13. bass normal and dc mode @ gain = 14 db, fc = 80 hz . . . . . . . . . . . . . . . . . . . . . . . . . . 19 figure 14. treble control @ fc = 17.5 khz) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 figure 15. treble center frequencies @ gain = 14 db . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 figure 16. noise blanker diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 figure 17. trigger threshold vs. vpeak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 figure 18. deviation controlled trigger adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 figure 19. fieldstrength controlled trigger adjustment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 figure 20. block diagram of the stereo decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 figure 21. signals during stereo decoder?s soft mute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 7 figure 22. internal stereo blend characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 figure 23. relation between internal and external level voltage and setup of stereo blend . . . . . . 29 figure 24. high cut characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 figure 25. block diagram of the noiseblankert. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 figure 26. block diagram of the multipath detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 figure 27. application example 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 figure 28. application example 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 figure 29. interface protocol diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 figure 30. so-28 mechanical data and package dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
block diagram and pin description tda7461 6/48 1 block diagram and pin description 1.1 block diagram figure 1. block diagram 1.2 pin description figure 2. pin connection (top view) supply loudness demodulator + stereo adjust + stereo blend cref mpin out lr d97au646a digital control pilot cancellation vs cass l input multiplexer + auto zero ph gnd beep mpx mixing stage volume bass treble out lr out lf out rr out rf out lf out rr out rf scl sda 80khz lp pll 25khz lp s & h high cut control multipath- detector pulse former d mpout level cdl cdg cdr am cass r phone gnd smute phone soft mute pil det i 2 c bus noise blanker a mux r mux l acoutl acoutr acinl acinr 765 10 3 4 9 8 11 21 20 26 13 14 12 23 25 22 24 18 19 16 15 2 1 27 28 17 acinl acinr cassr cassl cdr cdl cdgnd ph gnd phone gnd vs outrr outrf outlr outlf cref acoutr acoutl 1 3 2 4 5 6 7 8 9 26 25 24 23 22 20 21 19 27 10 28 am sda d97au647 mpx level mpin muxr smute scl 11 12 13 18 16 17 15 14 mpout muxl
tda7461 block diagram and pin description 7/48 pin type: i = input o = output i/o = input/output s = supply table 2. pin description n. name function type 1 acinl speaker stage input left i 2 acinr speaker stage input right i 3 cassr cassette input right i 4 cassl cassette input left i 5 cdr cd right channel input i 6 cdgnd ground reference cd i 7 cdl cd left channel input i 8 phgnd phone ground i 9 phone phone input i 10 am am input i 11 mpx fm input (mpx) i 12 level level input stereo decoder i 13 mpin multipath detector input i 14 mpout multipath detector output o 15 muxl multiplexer output left channel (stereo decoder output left selectable (1) 1. see data byte specificat ion - speaker attenuator o 16 muxr multiplexer output right channel (stereo decoder output right selectable (1)) o 17 smute soft mute drive i 18 scl i 2 c clock line i/o 19 sda i 2 c data line i/o 20 gnd supply ground s 21 vs supply voltage s 22 outrr right rear speaker output o 23 outlr left rear speaker output o 24 outrf right front speaker output o 25 outlf left front speaker output o 26 cref reference capacitor pin s 27 acoutr pre-speaker ac output right channel o 28 acoutl pre-speaker ac output left channel o
electrical specification tda7461 8/48 2 electrical specification 2.1 absolute maximum ratings 2.2 supply 2.3 esd all pins are protected against esd according to the mil883 standard. 2.4 thermal data table 3. absolute maximum ratings symbol parameter value unit v s operating supply voltage 10.5 v t amb operating ambient temperature range -40 to 85 c t stg storage temperature range -55 to 150 c table 4. supply symbol parameter test condition min. typ. max. unit v s supply voltage 7.5 9 10 v i s supply current v s = 9v 25 30 35 ma svrr ripple rejection @ 1 khz audioprocessor (all filters flat) 60 db stereo decoder + audioprocessor 45 db table 5. thermal data symbol parameter value unit r th j-pins thermal resistance junction to pins max 85 c/w
tda7461 electrical specification 9/48 2.5 audio processor part feature 2.5.1 input multiplexer fully differential or quasi-differential cd and cassette stereo input am mono or stereo input phone differential or single ended input internal beep with 2 frequencies (selectable) mixable phone and beep signals loudness second order frequency response programmable center frequency and quality factor 15 x 1 db steps selectable flat-mode (constant attenuation) 2.5.2 volume control 1 db attenuator max. gain 20 db max. attenuation 79 db soft-step gain control 2.5.3 bass control 2 nd order frequency response center frequency programmable in 4 (5) steps dc gain programmable 7 x 2 db steps 2.5.4 treble control 2 nd order frequency response center frequency programmable in 4 steps 7 x 2 db steps 2.5.5 speaker control 4 independent speaker controls (1 db steps control range 50 db) 2.5.6 mute function direct mute digitally controlled softmute with 4 programmable time constants
electrical specification tda7461 10/48 2.6 audio processor electrical characteristics table 6. audio processor electrical characteristics (v s = 9 v; t amb = 25 c; r l = 10 k ; all gains = 0 db; f = 1 khz; unless otherwise specified). symbol parameter test cond ition min. typ. max. unit input selector r in input resistance all inputs except phone 70 100 130 k v cl clipping level 2.2 2.6 v rms s in input separation 80 100 db g in min min. input gain -1 0 1 db g in max max. input gain 13 14 15 db g step step resolution 1 2 3 db v dc dc steps adjacent gain step -5 0 +5 mv g min to g max -5 1 +5 mv differential cd stereo input r in input resistance differential 70 100 130 k common mode 20 30 40 k cmrr common mode rejection ratio v cm = 1 v rms @ 1 khz 45 70 db v cm = 1 v rms @ 10 khz 45 60 db e n output noise @ speaker output 20 hz to 20 khz flat; all stages 0db 9 15 v differential phone input r in input resistance differential 10 15 20 k common mode 20 30 40 k cmrr common mode rejection ratio v cm = 1 v rms @ 1 khz 45 70 db v cm = 1 v rms @ 10 khz 45 60 db beep control v rms beep level 250 350 500 mv f bmin lower beep frequency 570 600 630 hz f bmax higher beep frequency 1.15 1.2 1.25 khz mixing control m level mixing level source -1 0 1 db source -5 -6 -7 db source -10 -12 -14 db beep/phone -1 0 1 db volume control g max max gain 19 20 21 db a max max attenuation -83 -79 -75 db
tda7461 electrical specification 11/48 a step step resolution 0.5 1 1.5 db e a attenuation set error g = -20 to 20 db -1.25 0 1.25 db g = -60 to 20 db -4 0 3 db e t tracking error 2db v dc dc steps adjacent attenuation steps -3 0.1 3 mv from 0 db to gmin -7 0.5 +7 mv loudness control a step step resolution 0.5 1 1.5 db a max max. attenuation -16 -15 -14 db f cmin lower center frequency 180 200 220 hz f cmax higher center frequency 360 400 440 hz soft mute a mute mute attenuation 60 100 db t d delay time t1 0.48 1 ms t2 0.96 2 ms t3 20 40.4 60 ms t4 200 324 600 ms v thlow low threshold for sm pin (1) 1v v thhigh high threshold for sm pin 2.5 v r pu internal pull-up resistor 70 100 130 k v pu pull-up voltage 4.7 v soft step t sw switch time 5 10 15 ms bass control c range control range 13 14 15 db a step step resolution 1 2 3 db f c center frequency f c1 54 60 66 hz f c2 63 70 77 hz f c3 72 80 88 hz f c4 90 100 (2) 110 hz q bass quality factor q 1 0.911.1 q 2 1.11.251.4 q 3 1.3 1.5 1.7 q 4 1.822.2 table 6. audio processor electrical characteristics (continued) (v s = 9 v; t amb = 25 c; r l = 10 k ; all gains = 0 db; f = 1 khz; unless otherwise specified). symbol parameter test cond ition min. typ. max. unit
electrical specification tda7461 12/48 dc gain bass-dc-gain dc = off -1 0 +1 db dc = on 4 4.4 6 db treble control c range control range 13 14 15 db a step step resolution 1 2 3 db f c center frequency f c1 81012khz f c2 10 12.5 15 khz f c3 12 15 18 khz f c4 14 17.5 21 khz speaker attenuator c range control range -53 -50 -47 db a step step resolution 0.5 1 2 db a mute output mute attenuation 80 90 db e e attenuation set error -2 2 db v dc dc steps 0.1 5 mv audio outputs v clip clipping level 2.2 2.6 v rms r l output load resistance 2 k c l output load capacitance 10 nf r out output impedance 30 100 w v dc dc voltage level 3.6 3.8 4.0 v general e no output noise bw = 20 hz to 20 khz output muted 315 v all gain = 0 db bw = 20 hz to 20 khz 6.5 15 v s/n signal to noise ratio all gain = 0 db flat; v o = 2 v rms 106 db bass treble at 12 db; v o = 2.6v rms 100 db d distortion v in = 1 v rms ; all stages 0 db 0.002 0.1 % v in = 1 v rms ; bass & treble = 12 db 0.05 0.1 % s c channel separation left/right 80 100 db e t total tracking error a v = 0 to -20 db -1 0 1 db a v = -20 to -60 db -2 0 2 db 1. the sm pin is active low (mute = 0) 2. see description of audioprocessor part - bass & treble filter charac teristics programming table 6. audio processor electrical characteristics (continued) (v s = 9 v; t amb = 25 c; r l = 10 k ; all gains = 0 db; f = 1 khz; unless otherwise specified). symbol parameter test cond ition min. typ. max. unit
tda7461 description of the audio processor part 13/48 3 description of the audio processor part 3.1 programmable input matrix the programmable input matrix of the tda7461 offers several possibilities to adapt the audioprocessor to the desired application. in to the standard application we have: cd quasi differential cassette stereo phone differential am mono stereo decoder input. the input matrix can be configured by only 2 bi ts: bits 3 and 4 of subaddress 0. basically the bit of subaddress 13 is fixed by the application and has to be programmed only once at the startup of the ic. for many configurations the two bits are also fixed during one application (e.g. the standard application) and a change of the input source can be done by loading the first three bits of subaddress 0. in other configurations for some sources a programming of bit 3 and 4 of subaddress 0 is necessary in addition to the three source selection bits. in every case only the subaddress 0 has to be changed to switch from one source to another. the following picture shows the input and source programming flow: figure 3. input configuration tree 1. in amstd configuration the am mono signal is l ead through the fm stereo decoder part to use its additional filters. tda7461 cd qd cd fd appl. 2 appl. 1 appl. 3 appl. 5 appl. 4 appl. 6 cd qd cassette fm std am mono phone (d) cd qd cassette fm std am stereo phone (se) cd qd cassette fm std am std phone (d) cd fd cassette fm std am mono phone (se) cd fd cassette fm std am stereo cd fd cassette fm std am std phone (se) d97au632b
description of the audio processor part tda7461 14/48 3.1.1 how to find the ri ght input configuration the best way to come to the desired configuration may be to go through the application tree from the top to the bottom while making the specific decisions. this way will lead to one of the six possible applications. then take the number of the application and go into the pinni ng table. here you will find th e special pinout as well as the special programming code s for selecting sources. for example in appl. 6 the tda7461 has to be configured while startup with the data byte 0/xxxx0xxx. to select the fm, am or phone source the last five significant bits of subaddress 0 have to be changed, for any other source the last three bits are sufficient (see data byte specification). 3.1.2 input stages most of the input circuits are the same as in previous st audio processors with exception of the cd inputs (see figure 4 ). in the meantime there are some cd players in the market having a significant high source impedance which affects strongly the common mode rejection of the normal differential input stage. the additional buffer of the cd input avoids this drawback and offers the full common mode rejection even with those cd players. table 7. input and source programming appl. n# pin number programming (1) 1. syntax 0/xxx11100 means: subaddress = 0 - data byte = xxx11100 (x - don?t care). 68910 1cd gnd phone gnd phone am mono startup 0/xxx11xxx 2cd gnd phone gnd amright am left startup 0/xxxx1xxx fm 0/xxx11100 am 0/xxx01011 phone 0/xxx11010 3cd gnd phone gnd phone amstd startup 0/xxxx1xxx fm 0/xxx11100 am 0/xxx01100 phone 0/xxx11010 4 cdr gnd cdl gnd phone am mono startup 0/xxxx0xxx 5 cdr gnd cdl gnd amright am left startup 0/xxxx0xxx fm 0/xxx10100 am 0/xxx00011 6 cdr gnd cdl gnd phone am std startup 0/xxxx0xxx fm 0/xxx10100 am 0/xxx00100 phone 0/xxx10010
tda7461 description of the audio processor part 15/48 the tda7461 can be configured with an additional input; if the ac coupling before the speaker stage is not used (bit 7 in subaddress 5 set to "1") acinl and acinr pins can be used as an additional stereo input. figure 4. input stages 3.1.3 autozero in order to reduce the number of pins there is no ac coupling between the in-gain and the following stage, so that any offset generated by or before the in-gain stage would be transferred or even amplified to the output. to avoid that effect a special offset cancellation stage called autozero is implemented. to avoid audible clicks the audioprocessor is muted before the loudness stage during this time. in some cases, for example if the p is executing a refresh cycle of the i 2 c bus programming, it is not useful to start a ne w autozero action because no new source is selected and an undesired mute would appear at the outputs. for such applications the tda7461 could be switched in the "auto zero remain" mode (bit 6 of the subaddress byte). if this bit is set to high, the databyte 0 coul d be loaded without in voking the autozero and the old adjustment value remains. 3.2 mux output the mux_l and mux_r outputs can provide selectively the output of the input multiplexer (speaker rf register, byte 8, bit 6=1) or the output of the stereo decoder (speaker rf register byte 8 bit 6=0). if bit d3 byte 10 (stdec register) is set to 1, then the stdec signal is automatically muted, when another source is selected at the input multiplexer. 15k 15k 100k cd cdgnd 15k 15k - + 15k 15k phone ph_gnd 15k 15k - + d97au633a 100k 100k 100k stereodecoder in gain cassette am mpx
description of the audio processor part tda7461 16/48 if bit d3 byte 10 (stdec register ) is set to 0, then the stdec signal will be always available at the mux out pins, no matter which is the selected source. the selection of the stereodecoder input, via a special procedure, is recommended. 1. soft mute or mute the signal path 2. temporary deselect the stereodec 3. wait 100-200 ms to allow the stdec internal filters to settle 4. select sterodec input (with automatic autozero) this procedure guarantees an optimum offsetcancellation, avoiding big dc offsets due to the autozero circuitry, which otherwise could try to compensate the signal sourced at the mpx input instead of the stereodecoder intrinsic offset. 3.3 mixing stage this stage offers the possibilit y to mix the internal beep or the phone signal to any other source. due to the fact that the mixing stage is also located behind the in-gain stage fine adjustments of the main source level can be done in this way. 3.3.1 loudness there are four parameters programmable in the loudness stage (see figure 5 , 6 and 7 ): attenuation center frequency loudness q flat mode: in this mode the loudness stage works as a 0 - 15db attenuator. figure 5. loudness attenuation @ fc = 400 hz (second order) figure 6. loudness center frequency @ atten. = 15 db (second order)
tda7461 description of the audio processor part 17/48 figure 7. loudness attenuation = 15 db @ fc = 400 hz 3.3.2 softmute the digitally controlled softmute stage allows muting/demuting the signal with a i 2 c bus programmable slope. the mute process can either be activated by the softmute pin or by the i 2 c bus. the slope is realized in a special s shaped curve to mute slow in the critical regions (see figure 8 ). for timing purposes the bit 3 of the i 2 c bus output register is set to 1 from the start of muting until the end of demuting. figure 8. softmute timing 1. please notice that a started mute action is alwa ys terminated and could not be interrupted by a change of the mute signal. 3.3.3 soft step volume when volume level is changed often an audible click appears at the output. the root cause of those clicks could be either a dc offset before the volume stage or the sudden change of the envelope of the audio signal. with the soft step feature both kinds of clicks could be reduced to a minimum and are no more audible (see figure 9 ). 10 100 1,000 hz -20 -15 -10 -5 (db) d98au844 1 ext. mute +signal ref -signal 1 i 2 c bus out time d97au634
description of the audio processor part tda7461 18/48 figure 9. soft step timing 1. for steps more than 1db the soft step mode should be deactivated because it could generate a 1db error during the blend-time. 3.3.4 bass there are three parameters programmable in the bass stage (see figure 10 , 11 , 12 , 13 ): attenuation center frequency (60, 70, 80 and 100 hz) quality factors (1, 1.25, 1.5 and 2) 3.3.5 dc mode in this mode the dc gain is increased by 4.4 db. in addition the programmed center frequency and quality factor is decreased by 25 % which can be used to reach alternative center frequencies or quality factors. 3.3.6 treble there are two parameters programmable in the treble stage (see figure 14 , 15 ): attenuation center frequency (10, 12.5, 15 and 17.5 khz). 3.3.7 speaker attenuator due to practical aspects the steps in the speaker attenuator are not linear over the full range. at attenuations more than 24 db the steps increase from 1.5 db to 10 db (please see data byte specification). 2db 1db -1db -2db time d97au635 vout 10ms
tda7461 description of the audio processor part 19/48 (1) in general the center frequency, q and dc-mode can be set independently. the exception from this rule is the mode (5/xx1111xx) where the center frequency is set to 150hz instead of 100 hz. figure 10. bass control @ fc = 80 hz, q = 1 figure 11. bass center @ gain = 14 db, q = 1 figure 12. bass quality factors @ gain = 14 db, fc = 80 hz figure 13. bass normal and dc mode @ gain = 14 db, fc = 80 hz (1) figure 14. treble control @ fc = 17.5 khz) figure 15. treble center frequencies @ gain = 14 db
stereo decoder part tda7461 20/48 4 stereo decoder part 4.1 stereo decoder feature no external components necessary pll with adjustment free fully integrated vco automatic pilot dependent mono/stereo switching very high suppression of intermodulation and interference programmable roll-off compensation dedicated rds softmute high cut and stereo blend characteristics programmable in a wide range internal noise blanker with threshold controls multipath detector with programmable internal/external influence i 2 c bus control of all necessary functions 4.2 stereo decoder electrical characteristics . table 8. stereo decoder electrical characteristics (v s = 9 v; de-emphasis time constant = 50 s, v mpx = 500 mv, 75 khz deviation, f = 1 khz. g i = 6 db, t amb = 25 c; unless otherwise specified) symbol parameter test cond ition min. typ. max. unit v in mpx input level input gain = 3.5 db 0.5 1.25 v rms r in input resistance 70 100 130 k g min minimum input gain 1.5 3.5 4.5 db g max max input gain 8.5 11 12.5 db g step step resolution 1.75 2.5 3.25 db svrr supply voltage ripple rejection v ripple = 100 mv, f = 1 khz 55 db a max channel separation 30 50 db thd total harmonic distortion 0.02 0.3 % signal plus noise to noise ratio s = 2 v rms 80 91 db mono/stereo switch v pthst1 pilot threshold voltage for stereo, pth = 1 10 15 25 mv v pthst0 pilot threshold voltage for stereo, pth = 0 15 25 35 mv v pthmo1 pilot threshold voltage for mono, pth = 1 7 12 17 mv v pthmo0 pilot threshold voltage for stereo, pth = 0 10 19 25 mv pll f/f capture range 0.5 % sn + n --------------
tda7461 stereo decoder part 21/48 de-emphasis and high cut (1) hc50 de-emphasis time constant bit = 7, subadr. 10 = 0 v level >> v hch 25 50 75 s hc75 de-emphasis time constant bit = 7, subadr. 10 = 1 v level >> v hch 50 75 100 s hc50 high cut time constant bit = 7, subadr. 10 = 0 v level >> v hcl 100 150 200 s hc75 high cut time constant bit = 7, subadr. 10 = 1 v level >> v hcl 150 225 300 s stereo blend and high cut-control ref5v internal reference voltage 4.7 5 5.3 v tc ref5v temperature coefficient 3300 ppm l gmin min. level gain -1 0 +1 db l gmax max. level gain 8 10 12 db l gstep level gain step resolution 0.3 0.67 1.0 db v sblmin min. voltage for mono 29 33 37 %ref5v v sblmax max. voltage for mono 54 58 62 %ref5v v sblstep step resolution 5.0 8.4 12 %ref5v vhch min min.voltage for no high cut 36 42 46 %ref5v vhch max max. voltage for no high cut 62 66 70 %ref5v vhch step step resolution 5 8.4 12 %ref5v vhcl min min. voltage for full high cut 13 17 21 %vhch vhcl max max. voltage for full high cut 29 33 37 %vhch carrier and harmonic suppression at the output 19 pilot signal f = 19 khz 40 50 db 38 sub carrier f = 38 khz 75 db 57 sub carrier f = 57 khz 62 db 76 sub carrier f = 76 khz 90 db intermodulation (2) ) 2 pilot signal f mod = 10 khz f spur = 1 khz; 65 db 3 f mod = 13 khz; f spur = 1 khz; 75 db table 8. stereo decoder electrical characteristics (continued) (v s = 9 v; de-emphasis time constant = 50 s, v mpx = 500 mv, 75 khz deviation, f = 1 khz. g i = 6 db, t amb = 25 c; unless otherwise specified) symbol parameter test cond ition min. typ. max. unit
stereo decoder part tda7461 22/48 traffic radio (3) 57 signal f = 57 khz 70 db sca - subsidiary communications authorization (4) 67 signal f = 67 khz 75 db aci - adjacent channel interference (5) 114 signal f = 114 khz 95 db 190 signal f = 190 khz 84 db 1. by design/characterization but functionally guaranteed through dedicated test mode structure 2. intermodulation suppression: measured with: 91% pilot signal; fm = 10khz or 13khz. 3. traffic radio (v.f.) su ppression: measured with: 91 % stereo signal; 9 % pilot signal; fm=1 khz; 5% sub carrier (f = 57 khz, fm = 23 hz am, m = 60 %) 4. sca (subsidiary communications authoriza tion) measured with: 81% mono signal; 9% pilot signal; fm = 1 khz; 1 0% sca sub carrier (fs = 6 7 khz, unmodulated). 5. aci (adjacent channel interference) m easured with: 90% mono signal; 9% pilot si gnal; fm = 1 khz; 1% spurious signal (fs = 110 khz or 186 khz, unmodulated). table 8. stereo decoder electrical characteristics (continued) (v s = 9 v; de-emphasis time constant = 50 s, v mpx = 500 mv, 75 khz deviation, f = 1 khz. g i = 6 db, t amb = 25 c; unless otherwise specified) symbol parameter test cond ition min. typ. max. unit
tda7461 stereo decoder part 23/48 4.3 noise blanker part internal 2 nd order 140 khz high pass filter programmable trigger threshold additional circuits for trigger adjustment (deviation, field-strength) very low offset current during hold time four selectable pulse suppression times table 9. noise blanker electrical characteristics symbol parameter test condition min. typ. max. unit v tr trigger threshold (1) , (2) meas. with v peak = 0.9v nbt = 111 30 mv op nbt = 110 35 mv op nbt = 101 40 mv op nbt = 100 45 mv op nbt = 011 50 mv op nbt = 010 55 mv op nbt = 001 60 mv op nbt = 000 65 mv op v trnoise noise controlled trigger threshold (3) meas. with v peak = 1.5v nct = 00 260 mv op nct = 01 220 mv op nct = 10 180 mv op nct = 11 140 mv op v rect rectifier voltage v mpx = 0mv 0.5 0.9 1.3 v v mpx = 50mv; f = 150khz 1.5 1.7 2.1 v v mpx = 100mv; f = 150khz 2.2 2.5 2.9 v v rect dev deviation dependent (4) rectifier voltage means. with v mpx = 800mv (75khz dev.) ovd = 11 0.5 0.9(off) 1.3 mv op ovd = 10 0.9 1.2 1.5 mv op ovd = 01 1.7 2.0 2.3 mv op ovd = 00 2.5 2.8 3.1 mv op v rect fs fieldstrength controlled (5) rectifier voltage means. with v mpx = 0mv v level << v sbl (fully mono) fsc = 11 0.5 0.9(off) 1.3 v fsc = 10 1.0 1.3 1.6 v fsc = 01 1.5 1.8 2.1 v fsc = 00 2.0 2.3 2.6 v 1. all thresholds are measured using a pulse with t r = 2 s, t high = 2 s and t f = 10 s. 2. nbt represents the noise blank er-byte bits d2; d0 for the noi se blanker trigger threshold 3. nat represents the noise blank er-byte bit pair d4,d3 for the noi se controlled trigger adjustment 4. ovd represents the noise blanker-byte bit pair d7,d6 for the over deviation detector 5. fsc represents the fieldstrength-byte bit pair d1,d0 for the fieldstrength control
stereo decoder part tda7461 24/48 figure 16. noise blanker diagram figure 17. trigger threshold vs. v peak figure 18. deviation controlled trigger adjustment v op v in dc t r t high t f time d97au636 65mv 30mv 8 steps noise controlled trig. threshold min. trig. threshold 260mv(00) 220mv(01) 180mv(10) 140mv(11) 0.9v vth 1.5v v peak(v) d97au648 v peak (v op ) d97au649 20 deviation(khz) 0.9 1.2 2.0 2.8 detector off (11) 32.5 45 75 10 01 00
tda7461 stereo decoder part 25/48 figure 19. fieldstrength controlled trigger adjustment 4.4 multipath detector internal 19 khz bandpass filter programmable bandpass and rectifier gain two pin solution fully independent usable for external programming selectable internal influence on stereo blend 2.3v(00) 0.9v v peak e' d98au863 1.8v(01) 1.3v(10) mono stereo noisy signal good signal atc_sb off (11) noise ?3v table 10. multipath detector electrical characteristics symbol parameter test condition min. typ. max. unit f cmp center frequency of multipath- bandpass stereo decoder locked on pilot tone 19 khz g bpmp bandpass gain bits d 2 , d 1 configuration byte = 00 6 db bits d 2 , d 1 configuration byte = 01 16 db bits d 2 , d 1 configuration byte = 10 12 db bits d 2 , d 1 configuration byte = 11 18 db g rectmp rectifier gain bits d 7 , d 6 configuration byte = 00 7.6 db bits d 7 , d 6 configuration byte = 01 4.6 db bits d 7 , d 6 configuration byte = 10 0 db i chmp rectifier charge current 1 a i dismp rectifier discharge current 1.5 ma
stereo decoder part tda7461 26/48 4.5 description of stereo decoder the stereo decoder part of the tda7461 (see figure 20 ) contains all functions necessary to demodulate the mpx signal like pilot tone dependent mono/stereo switching as well as ?stereo blend? and ?high cut? functions. adaptations like programmable input gain, roll-off compensation, selectable de-emphasis time constant and a programmable fieldstrength input allow to use different if devices. figure 20. block diagram of the stereo decoder 4.5.1 stereo decoder mute the tda7461 has a fast and easy to control rds mute function which is a combination of the audioprocessor softmute and the high-ohmic mute of the stereo decoder. if the stereo decoder is selected and a softmute command is sent (or activated through the sm pin) the stereo decoder will be set automa tically to the high-ohmic mu te condition after the audio signal has been soft muted. hence a checking of alternate frequencies could be performed. to release the system from the mute condition simply the unmute command must be sent: the stereo decoder is unmuted immediately and the audioprocessor is softly unmuted. figure 21 shows the output signal v o as well as the internal stereo decoder mute signal. this influence of softmute on the stereo decoder mute can be switched off by setting bit 3 of the softmute byte to "0". a stereo decoder mute comma nd (bit 0, stereo dec oder byte set to "1") will set the stereo decoder in any case independently to the high-ohmic mute state. if any other source than the stereo decoder is selected the decoder remains muted and the mpx pin is connected to vref to avoid any discharge of the coupling capacitor through leakage currents. 4.5.2 input stages the in gain stage allows to adjust the mpx signal to a magnitude of about 1vrms internally which is the recommended value. the 4 th order input filter has a corner frequency of 80 khz and is used to attenuate spikes and noise and acts as an anti aliasing filter for the following switch capacitor filters. ingain 3.5 ... 11db step 2.5db infilter lp 80khz 4.th order demodulator - plot canc - roll-off comp. - lp 25khz pll + pilot-det. f19 noise blanker f38 stereo holdn sb control deemphasis + highcut t=50 or 75 s ref 5v vsbl mpinfl level intern hc control vhcch vhccl - multipath detector d a mpout level input lp 2.2khz 1.th order mpin level fm_l fm_r mpx 100k d97au762 gain 0..10db
tda7461 stereo decoder part 27/48 4.5.3 demodulator in the demodulator block the left and the right channel are separated from the mpx signal. in this stage also the 19 khz pilot tone is cancelled. for reaching a high channel separation the tda7461 offers an i 2 c bus programmable roll off adj ustment which is able to compensate the lowpass behavi or of the tuner section. if the tuner attenuation at 38 khz is in a range from 20.2 % to 31 % the tda7461 needs no external network before the mpx pin. within this range an adjustment to obtain at least 40 db channel separation is possible. the bits for this adjustment are located together with the fieldstrength adjustm ent in one byte. this gives the po ssibility to perform an optimization step during the production of the carradio where the channel separation and the fieldstrength control are trimmed. figure 21. signals during stereo decoder?s soft mute 4.5.4 de-emphasis and high cut the lowpass filter for the de-emphasis allows to choose between a time constant of 50 s and 75 s (bit d7, stereo decoder byte). the high cut control range will be in both cases t hc = 2 * t deemp . inside the high cut control range (between vhch and vhcl) the level sign al is converted into a 5 bit word which controls the lowpass time constant between t deemp ...3 t deemp . there by the resolution will remain always 5 bits independently of the absolute voltage range between the vhch and vhcl values. the high cut function can be switched off by i 2 c bus (bit d7, fieldstrength byte set to "0"). 4.5.5 pll and pilot tone detector the pll has the task to lock on the 19 khz pilotone during a stereo transmission to allow a correct demodulation. the included detector enables the demodulation if the pilot tone reaches the selected pilottone threshold vpthst. two different thresholds are available. the detector output (signal stereo, see block diagram) can be checked by reading the status byte of the tda7461 via i 2 c bus. softmute command std mute v o t d97au638 t t
stereo decoder part tda7461 28/48 4.5.6 fieldstrength control the fieldstrength input is used to control the high cut and the stereo blend function. in addition the signal can be also used to control the noise blanker thresholds. 4.5.7 level input and gain to suppress undesired high frequency modulation on the high cut and stereo blend function the level signal is lowpass filtered firstly. the filter is a combination of a 1 st order rc lowpass at 53 khz (working as anti-aliasing filter) and a 1storder switched capacitor lowpass at 2.2 khz. the second stage is a programmable gain stage to adapt the level signal internally to different if. the gain is widely programmable in 16 steps from 0 db to 10 db (step = 0.67 db). these 4 bits are located together with the roll-off bits in the ?stereo decoder adjustment? byte to simplify a possible adaptation during the production of the carradio. figure 22. internal stereo blend characteristics 4.5.8 stereo blend control the stereo blend control block converts the internal level voltage (level intern) into an demodulator compatible analog signal whic h is used to control the channel separation between 0db and the maximum separation. internally this control range has a fixed upper limit which is the internal re ference voltage ref5v. the lower limit can be programmed to be 33%, 42%, 50% or 58% of ref5v (see figure 23 ). to adjust the external level voltage to the inte rnal range two values must be defined: the level gain l g and vsbl. to adjust the voltage where the full channel separation is reached (vst) the level gain lg has to be defined. the follo wing equation can be used to estimate the gain: the gain can be programmed through 4 bits in the "stereo decoder-adjustment" byte. the mono voltage vmo (0 db channel separation) can be chosen selecting 33, 42, 50 or 58 % of ref5v. l g ref5v field strength voltage stereo [] ------------------------------------------------------------------------------------------------ =
tda7461 stereo decoder part 29/48 all necessary internal reference voltages like ref5v are derived from a band gap circuit. therefore they have a temperature coefficient near zero. this is useful if the fieldstrength signal is also temperature compensated. but most if devices ap ply a level voltage with a tc of 3 300 ppm. the tda7461 offers this tc for the reference voltages, too. the tc is selectable with bit d7 of the ?stereo decoder adjustment" byte. figure 23. relation betwee n internal and external level voltage and setup of stereo blend 4.5.9 high cut control the high cut control setup is similar to the stereo blend control setup: the starting point vhch can be set with 2 bits to be 42, 50, 58 or 66% of ref5v whereas the range can be set to be 17 or 33% of vhch (see figure 24 ). figure 24. high cut characteristics 4.6 functional description of the noise blanker in the automotive environment the mpx signal is disturbed by spikes produced by the ignition and for example the wiper motor. the aim of the noise blanker part is to cancel the audible influence of the spikes. therefore the output of the stereo decoder is held at the actual voltage for 40 s. in a first stage the spikes must be detected but to avoid a wrong triggering on high frequency (white) noise a complex trigger control is implemented. behind the trigger stage a pulse former generates the "blanking" pulse. to avoid any crosstalk to the signal path the noise blanker is supplied by his own biasing circuit. internal voltages t d97au639 vsbl ref 5v setup of vst internal voltages t 33% ref 5v setup of vmo level level intern fieldstrenght voltage vst vmo level intern 42% 50% 58% vsbl vst vmo fieldstrenght voltage lowpass time constant d97au640 deemp fieldstrenght vhch vhcl 3 ? deemp
stereo decoder part tda7461 30/48 4.6.1 trigger path the incoming mpx signal is highpass filtered, amplified and rectified. this second order highpass-filter has a corner frequency of 140 khz. the rectified signal, rect, is lowpass filtered to generate a signal called peak. also noise with a frequency 140 kh z increases the peak voltage. the peak voltage is fed to a thre shold generator, which adds to the peak voltage a dc dependent threshold vth. both signals, rect and peak+vth are fed to a comparator which triggers a re-triggerable monoflop. the monoflop?s output activates the sample-and-hold circuits in the signalpath for 40 s. the block diagram of the noiseblanker is given in figure 25 . 4.6.2 automatic noise controll ed threshold adjustment (atc) there are mainly two independent possibilities for prog ramming the trig ger threshold: the low threshold in 8 steps (bits d0 to d2 of the noiseblanker byte) the noise adjusted threshold in 4 steps (bits d3 and d4 of the noiseblanker byte, see fig. 18). the low threshold is active in combination with a good mpx signal without any noise; the peak voltage is less than 1v. the sensit ivity in this operation is high. if the mpx signal is noisy the peak voltage increases due to the higher noise, which is also rectified. with increasing of the peak voltage the trigger thre shold increases, too. this particular gain is programmable in 4 steps (see figure 17 ). figure 25. block diagram of the noiseblankert 4.6.3 automatic threshold control besides the noise controlled th reshold adjustment there is an additional possibility for influencing the trigger threshold. it is depending on the stereo blend control. the point where the mpx signal starts to become noisy is fixed by the rf part. therefore also the starting point of the normal noise-controlled trigger adjustment is fixed ( figure 19 ). in some cases the behavior of the noise blanker can be improved by increasing the threshold even in a region of higher fieldstrength. sometimes a wrong triggering occurs for the mpx signal often shows distortion in this range which can be avoided even if using a low threshold. + - rectifier lowpass rect + + threshold generator vth peak additional threshold control monoflop holdn mpx d98au861 high pass
tda7461 stereo decoder part 31/48 because of the overlap of this range and the range of the stereo/mono transition it can be controlled by stereo blend. this threshold increase is programmable in 3 steps or switched off with bits d0 and d1 of the fieldstrength control byte. 4.6.4 over deviation detector if the system is tuned to stations with a high deviation the noise blanker can trigger on the higher frequencies of the modulation. to avoid this wrong behavior, which causes noise in the output signal, the noise blanker offers a deviation dependent threshold adjustment. by rectifying the mpx signal a further signal repres enting the actual deviation is obtained. it is used to increase the peak voltag e. offset and gain of this circuit are programmable in 3 steps with the bits d6 and d7 of the stereo decoder byte (the first step turns off the detector, see figure 18 ). 4.7 functional description of the multipath detector using the internal detector the audible effects of a multipath condition can be minimized. a multipath condition is detected by rectifying the 19 khz spectrum in the fieldstrength signal. selecting the "internal influence" in the configuration byte, the channel separation is automatically reduced during a multipath condition according to the voltage appearing at the mpout pin. to obtain a optimal performance an adaptation is necessary. therefore the gain of the 19 khz bandpass is programmable in four steps as well as the rectifier gain. the attack and decay times can be set by th e external capacitor value. 4.8 test mode during the test mode which can be activated by setting bit d0 of the testing byte and bit d5 of the subaddress byte to "1" several internal signals are avai lable at the cassr pin. during this mode the input resistance of 100 k is disconnected from the pin. the internal signals available are shown in the software specification. figure 26. block diagram of the multipath detector rectifier bandpass 19khz - to sb d97au880 mpin gain 2 bits gain 2 bits dc=1 a vdd mpout level int. influence 220nf
stereo decoder part tda7461 32/48 figure 27. application example 1 figure 28. application example 2 = +v cc 9v 100nf cass r cass l 100nf 100nf cdr cdg 100nf 22 f cdl 100nf phone_gnd 220nf cass r cass l cdr cdg cdl phgnd phone 220nf phone outrr mpx 220nf outrr mpx am 220nf am outlr outlr outrf outrf outlf outlf cref 10 f d97au763a level smute scl sda level smute scl sda gnd v s unweighted level 220nf mpin mpout muxr muxl sound effects acoutl acoutr acinl acinr note: bit d7 of "bass and treble filter characteristics" set to 1 tda7461 = +v cc 9v 100nf cass r cass l 100nf 100nf cdr cdg 100nf 22 f cdl 100nf phone_gnd 220nf cass r cass l cdr cdg cdl phgnd phone 220nf phone outrr mpx 220nf outrr mpx am 220nf am outlr outlr outrf outrf outlf outlf cref 10 f d97au764 level smute scl sda level smute scl sda gnd v s unweighted level 220nf mpin mpout muxr muxl acoutl acoutr pre-speaker output additional input 100nf 100nf acinl acinr note: bit d7 of "bass and treble filter characteristics" set to 0 tda7461
tda7461 i 2 c bus interface description 33/48 5 i 2 c bus interface description 5.1 interface protocol the interface protocol comprises: a start condition (s) a chip address byte (the lsb bit determines read/ write transmission) a subaddress byte a sequence of data (n-bytes + acknowledge) a stop condition (p) figure 29. interface protocol diagram s = start ack = acknowledge az = autozero-remain t = testing i = auto increment p = stop max. clock speed: 500 kbits/s the transmitted data is automatically updated after each ack. transmission can be repeated without new chip address. 5.2 auto increment if bit i in the subaddress byte is set to "1", the auto increment of the subaddress is enabled. sm = soft mute activated st = stereo x = not used d97au627 s 1 0 0 0 1 1 0 r/w ack ack ack p msb lsb msb lsb msb lsb chip address x i subaddress data 1 to data n az t a3 a2 a1 a0 data table 11. transmitted data (send mode) msb lsb xxxxstsmxx
i 2 c bus interface description tda7461 34/48 t = testmode i = auto increment az = auto zero remain x = not used table 12. subaddress (receive mode) msb lsb function x az t i a3a2a1a0 0000input selector 0001lou dness / auto-zero 0010volume 0011softmute / beep 0100bass / treble attenuator 0101bass / treble configuration 0110s peaker attenuator lf 0111s peaker attenuator lr 1000s peaker attenuator rf 1001 speaker attenuator rr / blank time adjust 1010stereo decoder 1011noise blanker 1100fieldstrength control 1101configuration 1110stereo decoder adjustment 1111testing
tda7461 data byte specification 35/48 6 data byte specification for example to select the cd input in quasi-differentia l mode with gain of 8 db the data byte is: 0/01111000 table 13. input selector msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 source selector cd cassette phone am stereo decoder input fm mute ac inputs 0 1 cd mode cd full-differential cd quasi-diff 1 0 0 1 0 0 1 1 1 1 0 0 1 1 0 0 am/fm mode am mono am stereo am through stereo decoder fm- stereo decoder 0 0 : 1 1 0 0 : 1 1 0 1 : 0 1 in-gain 14 db 12 db : 2 db 0 db
data byte specification tda7461 36/48 note: the attenuation is specified at high frequencie s. around the center frequency the value is different depending on the programmed attenuati on (see loudness frequency response). table 14. loudness msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 : 1 1 0 0 : 1 1 0 0 : 1 1 0 1 : 0 1 attenuation 0 db -1 db : -14 db -15 db 0 1 filter on off (flat) 0 1 center frequency 200 hz 400 hz 0 1 loudness q low (1 s t order) normal (2 nd order) 1 must be "1?
tda7461 data byte specification 37/48 note: for more information to the stereo decoder-s oftmute-influence please refer to the stereo decoder description. table 15. mute, beep and mixing msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 1 0 0 1 1 0 1 0 1 0 1 mute enable softmute disable softmute mute time =0.48 ms mute time =0.96 ms mute time =40.4 ms mute time =324 ms stereo decoder softmute influence = off stereo decoder softmute influence = on 0 1 beep beep frequency = 600 hz beep frequency = 1.2 khz 0 0 1 1 0 1 0 1 0 1 mixing mix-source = beep mix-source = phone full mix signal source -12 db + mix-signal -2.5 db source -6 db + mix-signal -6 db full source
data byte specification tda7461 38/48 note: it is not recommended to use a gain more than 20db for system performance reason. in general, the max. gain should be limited by software to the maximum value, which is needed for the system. table 16. volume msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 : 0 0 0 : 0 0 0 : 1 1 0 0 : 0 0 0 : 0 1 1 : 1 1 0 0 : 0 0 0 : 1 0 0 : 0 0 0 0 : 1 1 1 : 1 0 0 : 1 1 0 0 : 1 1 1 : 1 0 0 : 1 1 0 0 : 0 0 1 : 1 0 0 : 1 1 0 1 : 0 1 0 : 1 0 1 : 0 1 gain/attenuation +32 db +31 db : +20 db +19 db +18 db : +1 db 0 db - 1 db : -78 db -79 db 0 1 soft step soft step volume = off soft step volume = on
tda7461 data byte specification 39/48 for example 12db treble and -8db bass gi ve the following data byte: 0 0 1 1 1 0 0 1. table 17. bass and treble attenuation msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 : 0 0 1 1 : 1 1 0 0 : 1 1 1 1 : 0 0 0 0 : 1 1 1 1 : 0 0 0 1 : 0 1 1 0 : 1 0 treble steps -14 db -12 db : -2 db 0 db 0 db +2 db : +12 db +14 db 0 0 : 0 0 1 1 : 1 1 0 0 : 1 1 1 1 : 0 0 0 0 : 1 1 1 1 : 0 0 0 1 : 0 1 1 0 : 1 0 bass steps -14 db -12 db : -2 db 0 db 0 db +2 db : +12 db +14 db
data byte specification tda7461 40/48 for example treble center frequency = 15khz, bass center frequency = 100h z, bass q = 1 and dc = 0db give the following data byte: 1 0 0 0 1 1 1 0 table 18. bass and treble filter characteristics msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 1 1 0 1 0 1 treble center frequency = 10 khz center frequency = 12.5 khz center frequency = 15 khz center frequency = 17.5 khz 0 1 1 0 0 1 1 1 0 1 0 1 0 0 1 1 1 0 1 0 1 1 bass center frequency = 60 hz center frequency = 70 hz center frequency = 80 hz center frequency = 100 hz center frequency = 150 hz quality factor = 1 quality factor = 1.25 quality factor = 1.5 quality factor = 2 dc-gain = 0 db dc-gain = 4.4 db 0 1 ac coupling (1) for external connection internally connection 1. for deeper information s ee application examples figure 27 and 28 .
tda7461 data byte specification 41/48 ) table 19. speaker attenuation (lf, lr, rf, rr) msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 11 0 0 : 0 0 0 0 0 0 0 0 0 1 0 0 : 1 1 1 1 1 1 1 1 1 0 0 : 0 1 1 1 1 1 1 1 1 0 0 : 1 0 0 0 0 1 1 1 1 0 0 : 1 0 0 1 1 0 0 1 1 0 1 : 1 0 1 0 1 0 1 0 1 attenuation 0 db -1 db : -23 db -24.5 db -26 db -28 db -30 db -32 db -35 db -40 db -50 db speaker mute must be "1" (except rf, rr speaker; see below) 0 0 1 1 0 1 0 1 blank time adj. (subaddress speaker rr) 38 s 25.5 s 32 s 22 s 0 1 output selector for pins 15 and 16 . subaddress speaker rf) stereo decoder output selected input multiplexer output selected
data byte specification tda7461 42/48 table 20. stereo decoder msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 1 std unmuted std muted 0 0 1 1 0 1 0 1 in-gain 11 db in-gain 8.5 db in-gain 6 db in-gain 3.5 db 1 0 stereo decoder unmuted with stdec input selected an d automatically muted at the selection of any other source. stereo decoder unmuted whichever is the selected source. 1 01 forced mono mono/stereo switch automatically 0 1 pilot threshold high pilot threshold low 0 1 de-emphasis 50 s de-emphasis 75 s table 21. noise blanker msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 low threshold 65 mv low threshold 60 mv low threshold 55 mv low threshold 50 mv low threshold 45 mv low threshold 40 mv low threshold 35 mv low threshold 30 mv 0 0 1 1 0 1 0 1 noise controlled threshold 320 mv noise controlled threshold 260 mv noise controlled threshold 200 mv noise controlled threshold 140 mv 0 1 noise blanker off noise blanker on 0 0 1 1 0 1 0 1 over deviation adjust 2.8 v over deviation adjust 2.0 v over deviation adjust 1.2 v over deviation detector off
tda7461 data byte specification 43/48 l table 22. field strength control msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 1 1 0 1 0 1 noise blanker field strength adj 2.3 v noise blanker field strength adj 1.8 v noise blanker field strength adj 1.3 v noise blanker field strength adj off 0 0 1 1 0 1 0 1 vsbl at 33 % ref 5 v vsbl at 42 % ref 5 v vsbl at 50 % ref 5 v vsbl at 58 % ref 5 v 0 0 1 1 0 1 0 1 vhch at 42 % ref 5 v vhch at 50 % ref 5 v vhch at 58 % ref 5 v vhch at 66 % ref 5 v 1 0 vhcl at 17 % vhch vhcl at 33 % vhch 0 1 high cut off high cut on table 23. configuration msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 1 1 0 1 0 1 noise rectifier discharge resistor r = infinite r = 56 k r = 33 k r =18 k 0 0 1 1 0 1 0 1 multipath detector bandpass gain 6 db 16 db 12 db 18 db 0 1 multipath detector internal influence on off 1 mute be ?1? 0 0 1 1 0 1 0 1 multipath detector reflection gain gain = 7.6 db gain = 4.6 db gain = 0 db off
data byte specification tda7461 44/48 table 24. stereo decoder adjustment msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 0 0 : 1 : 1 0 0 1 : 0 : 1 0 1 0 : 0 : 1 roll-off compensation not allowed 20.2% 21.9% : 25.5% : 31.0% 0 0 0 : 1 0 0 0 : 1 0 0 1 : 1 0 1 0 : 1 level gain 0db 0.66 db 1.33 db : 10 db 0 1 temperature compensation at level input tc = 0 tc = 16.7 mv/k (3300 ppm)
tda7461 data byte specification 45/48 note: this byte is used for testing or evaluation pur poses only and must not be set to other values than the default "11111110" in the application! table 25. testing msb lsb function d7 d6 d5 d4 d3 d2 d1 d0 0 1 stereo decoder test signals off test signals enabled if bit d5 of the subaddress (test mode bit) is set to "1", too 0 1 external clock internal clock 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 test signals at cass_r vhcch level intern pilot magnitude vcocon; vco control voltage pilot threshold holdn nb threshold f228 vhccl vsbl not used not used peak not used ref5v not used 0 1 vco off on 0 1 audio processor test mode only if bit d5 of the subaddress (test mode bit) is set to "1" off
package information tda7461 46/48 7 package information in order to meet environmental requirements, st offers these devices in different grades of ecopack ? packages, depending on their level of environmental compliance. ecopack ? specifications, grade definitions and product status are available at: www.st.com . ecopack ? is an st trademark. figure 30. so-28 mechanical data and package dimensions so-28 dim. mm inch min. typ. max. min. typ. max. a 2.65 0.104 a1 0.1 0.3 0.004 0.012 b 0.35 0.49 0.014 0.019 b1 0.23 0.32 0.009 0.013 c 0.5 0.020 c1 45 (typ.) d 17.7 18.1 0.697 0.713 e 10 10.65 0.394 0.419 e 1.27 0.050 e3 16.51 0.65 f 7.4 7.6 0.291 0.299 l 0.4 1.27 0.016 0.050 s8 (max.) outline and mechanical data
tda7461 revision history 47/48 8 revision history table 26. document revision history date revision changes 20-oct-2003 6 initial release. 13-jan-2009 7 document reformatted. document status changed from data sheet to ?not for new design?. removed all refences to dip28 package. added table 1: device summary on page 1 . updated section 7: package information on page 46 .
tda7461 48/48 please read carefully: information in this document is provided solely in connection with st products. stmicroelectronics nv and its subsidiaries (?st ?) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described he rein at any time, without notice. all st products are sold pursuant to st?s terms and conditions of sale. purchasers are solely responsible for the choice, selection and use of the st products and services described herein, and st as sumes no liability whatsoever relating to the choice, selection or use of the st products and services described herein. no license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. i f any part of this document refers to any third party products or services it shall not be deemed a license grant by st for the use of such third party products or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoev er of such third party products or services or any intellectual property contained therein. unless otherwise set forth in st?s terms and conditions of sale st disclaims any express or implied warranty with respect to the use and/or sale of st products including without limitation implied warranties of merchantability, fitness for a parti cular purpose (and their equivalents under the laws of any jurisdiction), or infringement of any patent, copyright or other intellectual property right. unless expressly approved in writing by an authorized st representative, st products are not recommended, authorized or warranted for use in milita ry, air craft, space, life saving, or life sustaining applications, nor in products or systems where failure or malfunction may result in personal injury, death, or severe property or environmental damage. st products which are not specified as "automotive grade" may only be used in automotive applications at user?s own risk. resale of st products with provisions different from the statements and/or technical features set forth in this document shall immediately void any warranty granted by st for the st product or service described herein and shall not create or extend in any manner whatsoev er, any liability of st. st and the st logo are trademarks or registered trademarks of st in various countries. information in this document supersedes and replaces all information previously supplied. the st logo is a registered trademark of stmicroelectronics. all other names are the property of their respective owners. ? 2009 stmicroelectronics - all rights reserved stmicroelectronics group of companies australia - belgium - brazil - canada - china - czech republic - finland - france - germany - hong kong - india - israel - ital y - japan - malaysia - malta - morocco - singapore - spain - sweden - switzerland - united kingdom - united states of america www.st.com

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