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TDA7295 80v - 80w dmos audio amplifier with mute/st-by very high operating voltage range ( 40v) dmos power stage high output power (up to 80w music power) muting/stand-by functions no switch on/off noise no boucherot cells very low distortion very low noise short circuit protection thermal shutdown description the TDA7295 is a monolithic integrated circuit in multiwatt15 package, intended for use as audio class ab amplifier in hi-fi field applications (home stereo, self powered loudspeakers, top- class tv). thanks to the wide voltage range and to the high out current capability it is able to sup- ply the highest power into both 4 w and 8 w loads even in presence of poor supply regulation, with high supply voltage rejection. the built in muting function with turn on delay simplifies the remote operation avoiding switching on-off noises. april 2003 ? in- 2 r2 680 w c2 22 m f c1 470nf in+ r1 22k r6 2.7 w c10 100nf 3 r3 22k - + mute stby 4 vm vstby 10 9 in+mute mute stby r4 22k thermal shutdown s/c protection r5 10k c3 10 m f c4 10 m f 1 stby-gnd c5 22 m f 713 14 6 15 8 -vs -pwvs boot- strap out +pwvs +vs c9 100nf c8 1000 m f -vs d93au011 +vs c7 100nf c6 1000 m f note: the boucherot cell r6, c10, normally not necessary for a stable operation it could be needed in presence of particular load impedances at v s <25v. figure 1: typical application and test circuit multiwatt 15 ordering number: TDA7295 multipower bcd technology 1/13
block diagram absolute maximum ratings symbol parameter value unit v s supply voltage 40 v i o output peak current 6 a p tot power dissipation t case = 70 c50w t op operating ambient temperature range 0 to 70 c t stg , t j storage and junction temperature 150 c pin connection (top view) TDA7295 2/13
thermal data symbol description value unit r th j-case thermal resistance junction-case max 1.5 c/w electrical characteristics (refer to the test circuit v s = 30v, r l = 8 w , g v = 30db; r g = 50 w ; t amb = 25c, f = 1 khz; unless otherwise specified. symbol parameter test condition min. typ. max. unit v s operating supply range 10 40 v i q quiescent current 20 30 65 ma i b input bias current 500 na v os input offset voltage +10 mv i os input offset current +100 na p o rms continuous output power d = 0.5%: v s = 30v, r l = 8 w v s = 26v, r l = 6 w v s = 22v, r l = 4 w 45 45 45 50 50 50 w w w music power (rms) (*) d t = 1s d = 10%; r l = 8 w ; v s = 34v (***) r l = 4 w ; v s = 26v 80 80 w w d total harmonic distortion (**) p o = 5w; f = 1khz p o = 0.1 to 30w; f = 20hz to 20khz 0.005 0.1 % % v s = 22v, r l = 4 w: p o = 5w; f = 1khz p o = 0.1 to 30w; f = 20hz to 20khz 0.01 0.1 % % sr slew rate 7 10 v/ m s g v open loop voltage gain 80 db g v closed loop voltage gain 24 30 40 db e n total input noise a = curve f = 20hz to 20khz 1 25 m v m v f l , f h frequency response (-3db) p o = 1w 20hz to 20khz r i input resistance 100 k w svr supply voltage rejection f = 100hz; v ripple = 0.5vrms 60 75 db t s thermal shutdown 145 c stand-by function (ref: -v s or gnd) v st on stand-by on threshold 1.5 v v st off stand-by off threshold 3.5 v att st-by stand-by attenuation 70 90 db i q st-by quiescent current @ stand-by 1 3 ma mute function (ref: -v s or gnd) v mon mute on threshold 1.5 v v moff mute off threshold 3.5 v att mute mute attenuation 60 80 db note (*): music power is the maximal power which the amplifier is capable of producing across the rated load resistance (regardless of n on linearity) 1 sec after the application of a sinusoidal input signal of frequency 1khz. note (**): tested with optimized application board (see fig. 2) note (***): limited by the max. allowable out current TDA7295 3/13
figure 2: p.c.b. and components layout of the circuit of figure 1. (1:1 scale) note: the stand-by and mute functions can be referred either to gnd or -vs. on the p.c.b. is possible to set both the configuration through the jumper j1. TDA7295 4/13
application suggestions (see test and application circuits of the fig. 1) the recommended values of the external components are those shown on the application circuit of fig- ure 1. different values can be used; the following table can help the designer. components suggested value purpose larger than suggested smaller than suggested r1 (*) 22k input resistance increase input imprdance decrease input impedance r2 680 w closed loop gain set to 30db (**) decrease of gain increase of gain r3 (*) 22k increase of gain decrease of gain r4 22k st-by time constant larger st-by on/off time smaller st-by on/off time; pop noise r5 10k mute time constant larger mute on/off time smaller mute on/off time c1 0.47 m f input dc decoupling higher low frequency cutoff c2 22 m f feedback dc decoupling higher low frequency cutoff c3 10 m f mute time constant larger mute on/off time smaller mute on/off time c4 10 m f st-by time constant larger st-by on/off time smaller st-by on/off time; pop noise c5 22 m f bootstrapping signal degradation at low frequency c6, c8 1000 m f supply voltage bypass danger of oscillation c7, c9 0.1 m f supply voltage bypass danger of oscillation (*) r1 = r3 for pop optimization (**) closed loop gain has to be 3 24db TDA7295 5/13
figure 3: output power vs. supply voltage. figure 5: output power vs. supply voltage figure 4: distortion vs. output power figure 8: distortion vs. frequency typical characteristics (application circuit of fig 1 unless otherwise specified) figure 6: distortion vs. output power figure 7: distortion vs. frequency TDA7295 6/13
figure 14: power dissipation vs. output power figure 13: power dissipation vs. output power figure 11: mute attenuation vs. v pin10 figure 12: st-by attenuation vs. v pin9 figure 10: supply voltage rejection vs. frequency typical characteristics (continued) figure 9: quiescent current vs. supply voltage TDA7295 7/13
introduction in consumer electronics, an increasing demand has arisen for very high power monolithic audio amplifiers able to match, with a low cost the per- formance obtained from the best discrete de- signs. the task of realizing this linear integrated circuit in conventional bipolar technology is made ex- tremely difficult by the occurence of 2nd break- down phenomenon. it limits the safe operating area (soa) of the power devices, and as a con- sequence, the maximum attainable output power, especially in presence of highly reactive loads. moreover, full exploitation of the soa translates into a substantial increase in circuit and layout complexity due to the need for sophisticated pro- tection circuits. to overcome these substantial drawbacks, the use of power mos devices, which are immune from secondary breakdown is highly desirable. the device described has therefore been devel- oped in a mixed bipolar-mos high voltage tech- nology called bcd 100. 1) output stage the main design task one is confronted with while developing an integrated circuit as a power op- erational amplifier, independently of the technol- ogy used, is that of realising the output stage. the solution shown as a principle schematic by fig 15 represents the dmos unity-gain output buffer of the TDA7295. this large-signal, high-power buffer must be ca- pable of handling extremely high current and volt- age levels while maintaining acceptably low har- monic distortion and good behaviour over fre- quency response; moreover, an accurate control of quiescent current is required. a local linearizing feedback, provided by differen- tial amplifier a, is used to fullfil the above require- ments, allowing a simple and effective quiescent current setting. proper biasing of the power output transistors alone is however not enough to guarantee the ab- sence of crossover distortion. while a linearization of the dc transfer charac- teristic of the stage is obtained, the dynamic be- haviour of the system must be taken into account. a significant aid in keeping the distortion contrib- uted by the final stage as low as possible is pro- vided by the compensation scheme, which ex- ploits the direct connection of the miller capacitor at the amplifiers output to introduce a local ac feedback path enclosing the output stage itself. 2) protections in designing a power ic, particular attention must be reserved to the circuits devoted to protection of the device from short circuit or overload condi- tions. due to the absence of the 2nd breakdown phe- nomenon, the soa of the power dmos transis- tors is delimited only by a maximum dissipation curve dependent on the duration of the applied stimulus. in order to fully exploit the capabilities of the power transistors, the protection scheme imple- mented in this device combines a conventional soa protection circuit with a novel local tempera- ture sensing technique which " dynamically" con- trols the maximum dissipation. figure 15: principle schematic of a dmos unity-gain buffer. TDA7295 8/13
in addition to the overload protection described above, the device features a thermal shutdown circuit which initially puts the device into a muting state (@ tj = 145 o c) and then into stand-by (@ tj = 150 o c). full protection against electrostatic discharges on every pin is included. 3) other features the device is provided with both stand-by and mute functions, independently driven by two cmos logic compatible input pins. the circuits dedicated to the switching on and off of the amplifier have been carefully optimized to avoid any kind of uncontrolled audible transient at the output. the sequence that we recommend during the on/off transients is shown by figure 16. the application of figure 17 shows the possibility of using only one command for both st-by and mute functions. on both the pins, the maximum applicable range corresponds to the operating supply voltage. 1n4148 10k 30k 20k 10 m f 10 m f mute stby d93au014 mute/ st-by figure 17: single signal st-by/mute control circuit play off st-by mute mute st-by off d93au013 5v 5v +vs (v) +35 -35 v mute pin #10 (v) v st-by pin #9 (v) -vs v in (mv) i p (ma) v out (v) figure 16: turn on/off suggested sequence TDA7295 9/13
bridge application another application suggestion is the bridge configuration, where two TDA7295 are used, as shown by the schematic diagram of figure 25. in this application, the value of the load must not be lower than 8 ohm for dissipation and current capability reasons. a suitable field of application includes hi-fi/tv subwoofers realisations. the main advantages offered by this solution are: - high power performances with limited supply voltage level. - considerably high output power even with high load values (i.e. 16 ohm). the characteristics shown by figures 20 and 21, measured with loads respectively 8 ohm and 16 ohm. with rl= 8 ohm, vs = 22v the maximum output power obtainable is 100w, while with rl=16 ohm, vs = 30v the maximum pout is 100w. 22k 0.56 m f 2200 m f 0.22 m f + - 22 m f 22k 680 22k 3 1 4 13 7 +vs vi 8 15 2 14 6 10 9 + - 3 0.56 m f 22k 1 4 2 14 6 22 m f 22k 680 10 9 22 m f 15 8 -vs 2200 m f 0.22 m f 22 m f 20k 10k 30k 1n4148 st-by/mute 13 7 d93au015a figure 18: bridge application circuit TDA7295 10/13
figure 20: distortion vs. output power figure 19: frequency response of the bridge application figure 21: distortion vs. output power TDA7295 11/13
multiwatt15 v dim. mm inch min. typ. max. min. typ. max. a 5 0.197 b 2.65 0.104 c 1.6 0.063 d 1 0.039 e 0.49 0.55 0.019 0.022 f 0.66 0.75 0.026 0.030 g 1.02 1.27 1.52 0.040 0.050 0.060 g1 17.53 17.78 18.03 0.690 0.700 0.710 h1 19.6 0.772 h2 20.2 0.795 l 21.9 22.2 22.5 0.862 0.874 0.886 l1 21.7 22.1 22.5 0.854 0.870 0.886 l2 17.65 18.1 0.695 0.713 l3 17.25 17.5 17.75 0.679 0.689 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 4.85 0.167 0.179 0.191 m1 4.63 5.08 5.53 0.182 0.200 0.218 s 1.9 2.6 0.075 0.102 s1 1.9 2.6 0.075 0.102 dia1 3.65 3.85 0.144 0.152 outline and mechanical data TDA7295 12/13
information furnished is believed to be accurate and reliable. however, stmicroelectronics assumes no responsib ility for the cons equences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of stmicroelectronics. specification mentioned in this pu blication are subject to change without notice. this publication supersedes and replaces all information previously supplied. stmicroelectron ics products are not authorized for use as critical components in life support devices or systems without express written approval of stmicr oelectronics. the st logo is a registered trademark of stmicroelectronics ? 2003 stmicroelectronics C printed in italy C all rights reserved stmicroelectronics group of companies australia - brazil - canada - china - finland - france - germany - hong kong - india - israel - italy - japan - malaysia - malt a - morocco - singapore - spain - sweden - switzerland - united kingdom - united states. http://www.st.com TDA7295 13/13

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