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this is information on a product in full production. april 2012 doc id 13907 rev 6 1/25 1 sta540 4 x 13 w dual/quad power amplifier datasheet ? production data features high output power capability ? 2x 38 w into 4 at 18 v, 1 khz, 10% thd ? 2x 34 w into 8 at 22 v, 1 khz, 10% thd ? 2x 24w into 4 at 14.4 v, 1 khz, 10% thd ? 2x 15 w into 8 at 16 v, 1 khz, 10% thd ? 4x 13 w into 2 at 15 v, 1 khz, 10% thd ? 4x 11 w into 4 at 18 v, 1 khz, 10% thd ? 4x 7 w into 4 at 14.4 v, 1 khz, 10% thd minimum external components count: ? no bootstrap capacitors ? no boucherot cells ? internally fixed gain 20 db standby function (cmos compatible) no audible pop during standby operations diagnostic facilities: ? clip detector ? output to gnd short-circuit detector ? output to vs short-circuit detector ? soft short-circuit check at turn-on ? thermal shutdown warning protection output ac/dc short circuit soft short-circuit check at turn-on thermal cutoff/limiter to prevent chip from overheating high inductive loads esd description the sta540 is a 4-channel, class-ab audio amplifier designed for high quality sound applications. the amplifiers have single-ended outputs with integrated short-circuit protection, thermal protection and diagnostic functions. the chip is housed in the 15-pin multiwatt ecopack ? pb-free package which is rohs (2002/95/ec) compliant. multiwatt15 table 1. device summary order code temperature range package packing sta540 -40 to 150 c multiwatt15 tube www.st.com
contents sta540 2/25 doc id 13907 rev 6 contents 1 block diagram and pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.1 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2 pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2 electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.1 absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2 thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.3 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3 standard application circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4 electrical characteristics curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5 thermal information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.1 heatsink specification examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.1.1 r th_hs calculation for 4 single-ended channels . . . . . . . . . . . . . . . . . . . 15 5.1.2 r th_hs calculation for 2 single-ended channels plus 1 btl channel . . . 15 5.1.3 calculations using music power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 6 practical information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.1 highly flexible amplifier configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.2 easy single-ended to bridge transition . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.3 internally fixed gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.4 silent turn on/off and muting/standby function . . . . . . . . . . . . . . . . . . . . . 17 6.5 driving circuit for standby mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.6 output stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.6.1 rail-to-rail output voltage swing without bootstrap capacitors . . . . . . . . 18 6.6.2 absolute stability without external compen sation . . . . . . . . . . . . . . . . . 18 6.7 built?in protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 6.7.1 diagnostic facilities (pin 10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 6.7.2 short-circuit protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 6.7.3 clipping detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 6.7.4 thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
sta540 contents doc id 13907 rev 6 3/25 6.8 handling the diagnostic information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.9 pcb ground layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 6.10 mute function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 7 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 8 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
list of tables sta540 4/25 doc id 13907 rev 6 list of tables table 1. device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 table 2. pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 table 3. absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 table 4. thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 table 5. electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 table 6. document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
sta540 list of figures doc id 13907 rev 6 5/25 list of figures figure 1. block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 figure 2. pin connection (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 figure 3. quadraphonic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 figure 4. alternative single-ended speaker connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 figure 5. dual bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 figure 6. stereo plus bridge drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 figure 7. quiescent drain current versus supply voltage (single-ended and bridge) . . . . . . . . . . . . . 12 figure 8. quiescent output voltage versus supply voltage (single-ended and bridge). . . . . . . . . . . . 12 figure 9. output power versus supply voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 10. output power versus supply voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 11. output power versus supply voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 12. distortion versus output power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 13. distortion versus output power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 14. distortion versus output power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 15. output power versus supply voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 16. output power versus supply voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 17. supply voltage rejection versus frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 18. crosstalk versus frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 19. standby attenuation versus threshold voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 figure 20. total power dissipation and efficiency versus output power. . . . . . . . . . . . . . . . . . . . . . . . 14 figure 21. total power dissipation and efficiency versus output power. . . . . . . . . . . . . . . . . . . . . . . . 14 figure 22. the new output stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 figure 23. shared capacitor in single-ended configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 figure 24. clipping detection wave forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 figure 25. output fault waveforms (see figure 26 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 figure 26. fault waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 figure 27. waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 figure 28. interface circuit diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 figure 29. optional mute function circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 figure 30. mechanical data and package dimensions (multiwatt15) . . . . . . . . . . . . . . . . . . . . . . . . . 23
block diagram and pin description sta540 6/25 doc id 13907 rev 6 1 block diagram and pin description 1.1 block diagram figure 1. block diagram 13 1 + - + - + - + - in1 v cc2 v cc1 out1 4 st-by svr p-gnd s-gnd 7 in2 5 in3 12 in4 11 out2 out3 out4 d06au1630 diagnostic output 2 15 14 10 3 689 a1 a2 inv a3 a4 inv st-by diagnosticd vcc1 vcc2
sta540 block diagram and pin description doc id 13907 rev 6 7/25 1.2 pin description figure 2. pin connection (top view) table 2. pin description n name type function 1 out1 out channel 1 output 2 out2 out channel 2 output 3 vcc1 pwr power supply 4 in1 in channel 1 input 5 in2 in channel 2 input 6 svr in supply voltage rejection 7 st-by in standby control pin 8 p-gnd pwr power ground 9 s-gnd pwr signal ground 10 diagnosticd out diagnostics output 11 in4 in channel 4 input 12 in3 in channel 3 input 13 vcc2 pwr power supply 14 out4 out channel 4 output 15 out3 out channel 3 output 1 2 3 4 5 6 7 9 10 11 8 in4 diagnosticd s-gnd pw-gnd stand-by svr in2 in1 vcc out2 out1 13 14 15 12 out3 out4 vcc in3 d06au1631 out3 out4 vcc2 in3 in4 diagnosticd s-gnd p-gnd st-by svr in2 in1 vcc1 out2 out1
electrical specifications sta540 8/25 doc id 13907 rev 6 2 electrical specifications 2.1 absolute maximum ratings 2.2 thermal data 2.3 electrical characteristics the test conditions are v s = 14.4 v, r l = 4 , f = 1 khz, t amb = 25 c unless otherwise specified. table 3. absolute maximum ratings symbol parameter value unit v s supply voltage idle mode (no signal) 24 v supply voltage operating 22 v supply voltage ac-dc short safe 20 v p tot total power dissipation (t case = 85 c) 36 w t stg , t j storage and junction temperature -40 to150 c t op operating temperature 0 to 70 c table 4. thermal data symbol parameter value unit r th j-case thermal resistance junction to case (max) 1.8 c/w r th j-amb thermal resistance junction to ambient (max) 35 c/w table 5. electrical characteristics symbol parameter test condition min typ max unit v s supply voltage range 8 22 v i d total quiescent drain current 80 150 ma v os output offset voltage -150 150 mv p o output power, se thd=10%, r l =4 thd=10%, r l =2 thd=10%, r l =4 , v s =22 v 6.5 7 11.5 16 w output power, btl thd=10%, r l =4 thd=10%, r l =8 , v s =17 v thd=10%, r l =8 , v s =22 v 21 24 20 34 w thd total harmonic distortion r l = 4 , p o = 0.1 to 4 w 0.02 % i sc short-circuit output current 4.0 a
sta540 electrical specifications doc id 13907 rev 6 9/25 c t crosstalk f = 1 khz single-ended f = 10 khz single-ended f = 1 khz btl f = 10 khz btl 55 70 60 60 db r in input impedance single-ended btl 20 10 30 15 k g v voltage gain single-ended btl 19 25 20 26 21 27 db g v voltage gain match 0.5 db e n input noise voltage r gen = 0, "a" weighted, s.e.: non-inverting channels inverting channels 2 5 v v btl r gen = 0, f = 22 hz to 22 khz 3.5 v svr supply voltage rejection r gen = 0, f = 300 hz, c svr = 470 f 50 db a sb standby attenuation p o = 1 w 80 90 db i sb current consumption in standby v st_by = 0 to 1.5 v 100 a v sb st-by in threshold voltage 1.5 v st-by out threshold voltage 3.5 v i st-by pin st-by current play mode, v st-by = 5 v 50 a max driving current under fault 5 ma i cd_off clipping detector output average current d = 1% (*) 90 a i cd_on clipping detector output average current d = 5% (*) 160 a v diagno sticd saturation voltage on pin diagnosticd i diagnosticd = 1 ma sinking 0.7 v t w thermal warning 140 c t m thermal muting 150 c t s thermal shutdown 160 c table 5. electrical characteristics (continued) symbol parameter test condition min typ max unit
standard application circuits sta540 10/25 doc id 13907 rev 6 3 standard application circuits figure 3. quadraphonic figure 4. alternative single-ended speaker connection figure 5. dual bridge suggested applications: 4x 13 w into 2 , at 15 v 4x 11 w into 4 , at 18 v 4x 9 w into 2 , at 12 v 4x 8 w into 4 , at 16 v 4x 5 w into 4 , at 12 v 1 2 3 4 5 6 7 89 10 11 12 13 14 15 1000 f 220 nf 2200 f 100 nf 10 f 10 k in_1 out_1 v s st_by 47 f 2200 f out_2 2200 f out_3 2200 f out_4 220 nf in_2 220 nf in_3 220 nf in_4 sta540 1 470 f 2 18 470 f 19 * the best audio performance is obtained with the configuration where each speaker has its own dc blocking capacitor. howeve r, if the application allows a little degradation of the spatial image it is possible to connect a couple of speakers with only one low-value dc blocking capacitor. 1 2 15 14 s uggested applications: 2x 38 w into 4 , at 18 v, 1 khz, 10% thd 2x 34 w into 8 , at 22 v, 1 khz, 10% thd 2x 24 w into 4 , at 14.4 v, 1 khz, 10% thd 2x 15 w into 8 , at 16 v, 1 khz, 10% thd 1 2 3 4 5 6 7 89 10 11 12 13 14 15 1000 f 470 nf 100 nf 10 f 10 k in_l v s st_by 47 f out_r 470 nf in_r out_l sta540
sta540 standard application circuits doc id 13907 rev 6 11/25 figure 6. stereo plus bridge drive suggested applications: 2x 9 w into 2 , +1x 18 w into 4 , at 12 v 2x 12 w into 2 , +1x 26 w into 4 , at 14.4 v 2x 8 w into 4 , +1x 16 w into 8 , at 16 v 1 2 3 4 5 6 7 89 10 11 12 13 14 15 1000 f 220 nf 2200 f 100 nf 10 f 10 k in_l out_l v s st_by 47 f 2200 f out_r out_bridge 220 nf in_r 470 nf in_bridge sta540
electrical characteristics curves sta540 12/25 doc id 13907 rev 6 4 electrical characteristics curves figure 7. quiescent drain current versus supply voltage (single-ended and bridge) figure 8. quiescent output voltage versus supply voltage (single-ended and bridge) figure 9. output power versus supply voltage figure 10. output power versus supply voltage figure 11. output power versus supply voltage figure 12. distortion versus output power 8 9 10 11 12 13 14 15 16 17 18 vs (v) 0 2 4 6 8 10 12 14 16 18 20 po (w) rl= 2 f= 1 khz thd= 10 % thd= 1 % single ended 8 9 10 11 12 13 14 15 16 17 18 vs (v) 0 1 2 3 4 5 6 7 8 9 10 11 12 po (w) rl= 4 f= 1 khz thd= 10 % thd= 1 % single ended
sta540 electrical characteristics curves doc id 13907 rev 6 13/25 figure 13. distortion versus output power f igure 14. distortion versus output power figure 15. output power versus supply voltage figure 16. output power versus supply voltage figure 17. supply voltage rejection versus frequency figure 18. crosstalk versus frequency 0 12 1 2 3 4 5 6 7 8 9 10 11 +8 +2 4 +10 +12 +14 +16 +18 +20 +22 po(w) vs(v) t.h.d=1% t.h.d=10% s.e. rl=8ohm f=1khz 0 12 1 2 3 4 5 6 7 8 9 10 11 +8 +2 4 +10 +12 +14 +16 +18 +20 +22 po(w) vs(v) t.h.d=1% t.h.d=10% s.e. rl=8ohm f=1khz 0 35 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25 27.5 30 32.5 +8 +22 +10 +12 +14 +16 +18 +20 btl rl=8ohm f=1khz po(w) vs(v) t.h.d=1% t.h.d=10% 0 35 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25 27.5 30 32.5 +8 +22 +10 +12 +14 +16 +18 +20 btl rl=8ohm f=1khz po(w) vs(v) t.h.d=1% t.h.d=10%
electrical characteristics curves sta540 14/25 doc id 13907 rev 6 figure 19. standby attenuation versus threshold voltage figure 20. total power dissipation and efficiency versus output power figure 21. total power dissipation and efficiency versus output power
sta540 thermal information doc id 13907 rev 6 15/25 5 thermal information in order to avoid the intervention of the thermal protection, placed at t j =150 c for thermal muting and t j =160 c for thermal shutdown, it is important to calculate the heatsink thermal resistance, r th_hs , correctly. the parameters that influence the calculation are: maximum dissipated power for the device (p d max ) maximum thermal resistance junction to case (r th_j-case ) maximum ambient temperature t amb_max there is also an additional term that depends on the iq (quiescent current). 5.1 heatsink specification examples 5.1.1 r th_hs calculation for 4 single-ended channels given v s = 14.4 v, r l = 4 x 4 channels, r th_j-case = 1.8 c/w, t amb_max = 50 c and p out = 4 x 7 w then the maximum power dissipated in the device is: and the required thermal resistance of the heatsink is: 5.1.2 r th_hs calculation for 2 single- ended channels plus 1 btl channel given v s = 14.4 v, r l = 2x 2 (se) + 1x 4 (btl), p out = 2 x 12 w + 1 x 26 w then the maximum power dissipated in the device is: and the required thermal resistance of the heatsink is: p dmax nchannel v cc 2 2 2 r l ------------------- - 4 2.62 10.5w = ? = ? = r th_hs 150 t amb_max ? p dmax --------------------------------------------- - r th_j-case 150 50 ? 10.5 ---------------------- 1.8 7.7 c/w = ? = ? = p dmax 2 v cc 2 2 2 r l ------------------- - 2v cc 2 2 r l -------------------- 25.25 10.5 21w = + ? = + ? = r th_hs 150 t amb_max ? p dmax --------------------------------------------- - r th_j-case 150 50 ? 21 ---------------------- 1.8 3 c/w = ? = ? =
thermal information sta540 16/25 doc id 13907 rev 6 5.1.3 calculations using music power the thermal resistance value calculated in each of the two above examples specifies a heatsink capable of sustaining the maximum dissipated power. realistically, however, and as explained in the application note (an1965), the heatsink can be smaller when the application is musical content. when music power is considered the resulting dissipation is about 40% less than the calculated maximum. thus, smaller or cheaper heatsinks can be employed. the heatsink thermal resistance values are modified as follows: for example 5.1.1 : 10.5 w - 40% = 6.3 w, thus giving r th_c-amb = 14 c/w, for example 5.1.2 : 21 w - 40% = 12.6 w, thus giving r th_c-amb = 6 c/w.
sta540 practical information doc id 13907 rev 6 17/25 6 practical information 6.1 highly flexible amplifier configuration the availability of four independent cha nnels makes it possible to accomplish several kinds of applications ranging from four speakers stereo (f/r) to two-speaker bridge solutions. when working with single-ended configurations, the polarity of the speakers driven by the inverting amplifier must be reversed with respect to those driven by non-inverting channels. this is to avoid phase irregularities causing sound alterations especially during the reproduction of low frequencies. 6.2 easy single-ended to bridge transition the change from single-ended to bridge configuration is made simple by connecting the two inputs together and also the speaker directly between the two outputs (no need for additional external components, in fact the output dc blocking capacitors are eliminated). however, take care to use an inve rting/non-inverti ng amplifier pair. 6.3 internally fixed gain the advantages in internally fixing the gain (to 20 db in single-ended configuration and to 26 db in bridge configuration) are: components and space saving, output noise, supply voltage rejection and distortion optimization. 6.4 silent turn on/off an d muting/standby function the standby mode can be easily activated by means of a cmos logic level applied to pin st-by through a rc filter. under standby conditions, the device is turned off completely (supply current = 1 ma typical, output attenuation = 80 db minimum). all on/off operations are virtually pop-free. furthermore, at turn-on the device stays in mute condition for a time determined by the value of the svr capacitor. this prevents transients, coming from previous stages, from producing unpleasant acoustic effects at the speakers. 6.5 driving circuit for standby mode some precautions need to be taken when designing the driving circuit for pin 7, st-by. for instance, the pin cannot be directly driven by a voltage source having a current capability higher than 5 ma. in practical cases a series resistance must be inserted, giving it the double purpose of limiting the current at pin 7 and to smooth down the standby on/off transitions. and, when done in combination with a capacitor, prevents output pop. a capacitor of at least 100 nf from pin 7 to s-gnd, with no resistance in between, is necessary to ensure correct turn-on.
practical information sta540 18/25 doc id 13907 rev 6 6.6 output stage the fully complementary output stage is possible with the power icv pnp component. this novel design is based on the connection shown in figure 22 and allows the full exploitation of its capabilities. the clear advantages this new approach has over classical output stages are described in the following sections. 6.6.1 rail-to-rail output voltage swing without bootstrap capacitors the output swing is lim ited only by the v cesat of the output transistors, which are in the range of 0.3 (r sat ) each. classical solutions adopting composite pnp-npn for the upper output stage have higher saturation loss on the top side of the waveform. this unbalanced saturation causes a significant power reduction. the only way to recover power includes of the addition of expensive bootstrap capacitors. 6.6.2 absolute stability without external compensation with reference to the circuit shown in figure 22 , the low frequency gain v out /v in is greater than unity, that is, approximately 1 + r2/r1. the dc output level (vcc / 2) is fixed by an auxiliary amplifier common to all the channels. by controlling the amount of this local feedback it is possible to force the loop gain (a* ) to less than unity at frequency where the phase shift is 180. this means that the output buffer is intrinsically stable an d not prone to oscillation. the above feature has been achieved even though there is very low closed-loop gain of the amplifier. this contrasts with the classical pnp-npn st age which makes use of external rc networks, namely the boucherot cells, for reducing the gain at high frequencies. figure 22. the new output stage
sta540 practical information doc id 13907 rev 6 19/25 6.7 built?in protection 6.7.1 diagnostic facilities (pin 10) the sta540 is equipped with diagnostic circuitry that is able to detect the following events: clipping of the output signal, thermal shutdown, output fault: ? short circuit to gnd, ? short circuit to vs, ? soft short circuit at turn-on. the event is signalled when the open collector output of pin 10 begins to sink current. 6.7.2 short-circuit protection reliable and safe operation in the presence of all kinds of output short circuit is assured by the built-in protection. as well as the ac/dc short circuit to gnd and to vs, and across the speaker, there is a soft short-circuit conditio n, which is signalled on pin 10 (diagnosticd) during the turn-on phase, to verify output circuit integrity in order to ensure correct amplifier operation. this particular kind of protection acts in such a way as to prevent the device being turned on (via pin st-by) when a resistive path (that is a dc path) less than 16 exists between the output and gnd. this would avoid loud speaker damage should, for example, the output coupling capacitor develop an internal short circuit. as mentioned previously, it is important to limit the external current driving pin st-by to 5 ma. the reason is that the associated circuitry is normally disabled with currents greater than 5 ma. the soft short-circuit protection is particularly attractive when, in the single-ended configuration, one capacitor is shared between two outputs (see figure 23 ). figure 23. shared capacitor in single-ended configuration
practical information sta540 20/25 doc id 13907 rev 6 6.7.3 clipping detection figure 24. clipping detection waveforms current sinking at pin 10 occurs when a certain distortion level is reached at each output. this function initiates a gain- compression facility whenever the amplifier is overdriven. 6.7.4 thermal shutdown with the thermal shutdown feature, the diagnostics output (pin 10) signals the closeness of the junction temperature to the shutdown threshold. typically, current sinking at pin 10 starts approximately 10 c before the shutdown temperature is reached. figure 25. output fault waveforms (see figure 26 ) figure 26. fault waveforms soft short out to vs short fault detection correct turn-on out to gnd short t t t st-by pin voltage 2v output waveform vpin 10 check at turn-on (test phase) short to gnd or to vs d05au1603mod
sta540 practical information doc id 13907 rev 6 21/25 6.8 handling the diagnostic information as different diagnostic information (clipping detection, output fault, approaching thermal shutdown) becomes available at pin 10 so the behavior of the signal at this pin changes. in order to discriminate the event, signal diagnosticd, pin 10, must be interpreted correctly. figure 27 shows a combination of events on the output waveform and the corresponding output on pin 10. this events could be diagnosed based on the timing of the output signal on pin 10. for example, the clip-detector sign alling under fault conditions c ould produce a low level for a short time. on the other hand, an output short circuit would probably produce a low level for a much longer time. with these assumptions, an interface circuit based on the one shown in figure 28 could differentiate the information and flag the appropriate circuits. figure 27. waveforms figure 28. interface circuit diagram t t t st-by pin voltage vs output waveform vpin 10 waveform short to gnd or to vs d05au1604mod clipping thermal proximity
practical information sta540 22/25 doc id 13907 rev 6 6.9 pcb ground layout the device has two distinct ground pins, p-gnd (power ground) and s-gnd (signal ground) which are disconnected from each other at chip level. for superior performance the pins p-gnd and s-gnd must be connected together on the pcb by low-resistance tracks. for the pcb-ground configuration, a star-like arrangement, where the center is represented by the supply-filtering electrolytic capacitor ground, is recommended. in an arrangement such as this, at least two separate paths must be provided, one for p-gnd and one for s-gnd. the correct ground assignments are as follows: on s-gnd: ? standby capacitor (pin 7, or any other standby driving networks), ? svr capacitor (pin 6), to be placed as close as possible to the device, ? input signal ground (from active/p assive signal processor stages) on p-gnd: ? power supply filtering capacitors for pins 3 and 13. the negative terminal of the electrolytic capacitor(s) must be directly tied to the battery negative line and this should represent the starting point for all the ground paths. 6.10 mute function if the mute function is desired, it can be implemented on pin 6, svr, as shown in figure 29 . figure 29. optional mute function circuit using a different value for r1 than the suggested 3.3 k , results in two different situations: r1 > 3.3 k : ? pop noise improvement, ? lower mute attenuation; r1 < 3.3 k : ? pop noise degradation, ? higher mute attenuation. 0.22 f 1 diagnostics 4 7 d06au1632 10 f 10k st-by in l 0.47 f 5 in bridge 12 470 f 6 13 1000 f 100nf 3 v s 2 15 14 out l 8 9 10 out bridge 11 0.22 f in r out r 2200 f 2200 f r1 3.3k r2 10k mute 5v 0 play v s = 10 to 16 v, mute off: v svr 0.6 to 0.8 v, mute on: v svr 0.2 v
sta540 package information doc id 13907 rev 6 23/25 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. mechanical data and pa ckage dimensions (multiwatt15) outline and mechanical data 00160 3 6 j dim. mm inch min. typ. max. min. typ. max. a0.197 b 2.65 0.104 c 1.6 0.06 3 d1 0.0 3 9 e 0.49 0.55 0.019 0.022 f 0.66 0.75 0.026 0.0 3 0 g 1.02 1.27 1.52 0.040 0.050 0.060 g1 17.5 3 17.7 8 1 8 .0 3 0.690 0.700 0.710 h1 19.6 0.772 h2 20.2 0.795 l 21.9 22.2 22.5 0. 8 62 0. 8 74 0. 88 6 l1 21.7 22.1 22.5 0. 8 54 0. 8 70. 88 6 l2 17.65 1 8 .1 0.695 0.71 3 l 3 17.25 17.5 17.75 0.679 0.6 8 9 0.699 l4 10. 3 10.7 10.9 0.406 0.421 0.429 l7 2.65 2.9 0.104 0.114 m 4.25 4.55 4. 8 5 0.167 0.179 0.191 m1 4.7 3 5.0 8 5.4 3 0.1 8 6 0.200 0.214 s 1.9 2.6 0.075 0.102 s 1 1.9 2.6 0.075 0.102 di a 1 3 .65 3 . 8 5 0.144 0.152 multiwatt15 (vertical) 5
revision history sta540 24/25 doc id 13907 rev 6 8 revision history table 6. document revision history date revision changes may-2006 1 initial release sep-2006 2 minor non-technical edits oct-2007 3 updated description on page 1 updated pin naming, numbering in all relevant figures minor non-technical edits 21-jan-2008 4 updated power specifications on pages 1, 6 and 8 updated short-circuit output current in table 5 02-apr-2012 5 modified v st-by to v sb and updated parameters in table 5: electrical characteristics updated ecopack ? text in section 7: package information 24-apr-2012 6 updated dimension a in figure 30: mechanical data and package dimensions (multiwatt15)
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