View TDA7350A_4404380.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

TDA7350A 22w bridge-stereo amplifier for car radio very few external components no boucherot cells no boostrap capacitors high output power no switch on/off noise very low stand-by current fixed gain (30db stereo) programmable turn-on delay protections: output ac-dc short circuit to ground and to supply voltage very inductive loads loudspeaker protection overrating chip temperature load dump voltage fortuitous open ground esd description the TDA7350A is a new technology class ab audio power amplifier in the multiwatt ? package designed for car radio applications. thanks to the fully complementary pnp/npn out- put configuration the high power performance of the TDA7350A is obtained without bootstrap ca- pacitors. a delayed turn-on mute circuit eliminates audible on/off noise, and a novel short circuit protection system prevents spurious intervention with highly inductive loads. april 1995 application circuit bridge multiwatt11 ordering number: TDA7350A 1/22
pin connection (top view) absolute maximum ratings symbol parameter test conditions unit v s operating supply voltage 18 v v s dc supply voltage 28 v v s peak supply voltage (for t = 50ms) 40 v i o output peak current (non rep. for t = 100 m s) 5 a i o output peak current (rep. freq. > 10hz) 4 a p tot power dissipation at t case = 85c 36 w t stg,tj storage and junction temperature -40 to 150 c thermal data symbol description value unit r thj-case thermal resistance junction-case max 1.8 c/w TDA7350A 2/22
electrical characteristics (refer to the test circuits, t amb = 25c, v s = 14.4v, f = 1khz unless otherwise specified) symbol parameter test condition min. typ. max. unit v s supply voltage range 8 18 v i d total quiescent drain current stereo configuration 120 ma a sb stand-by attenuation 60 80 db i sb stand-by current 100 m a t sd thermal shut-down junction temperature 150 c stereo p o output power (each channel) d = 10% r l = 2 w r l = 3.2 w r l = 4 w d = 10%; v s = 13.2v r l = 2 w r l = 3.2 w r l = 4 w 7 11 8 6.5 9 6.5 5.5 w w w w w w d distortion p o = 0.1 to 4w; r l = 3.2 w 0.5 % svr supply voltage rejection r g = 10k w c3 = 22 m f f = 100hz c3 = 100 m f 45 50 57 db ct crosstalk f = 1khz f = 10khz 45 55 50 db db r i input resistance 30 50 k w g v voltage gain 27 29 31 db g v voltage gain match 1 db e in input noise voltage r g = 50 w (*) r g = 10k w (*) r g = 50 w (**) r g = 10k w (**) 1.5 2 2 2.7 7 m v m v m v m v bridge p o output power d = 10%; r l = 4 w d = 10%; r l = 3.2 w d = 10%; v s = 13.2v r l = 4 w r l = 3.2 w 16 20 22 17.5 19 w w w w d distortion p o = 0.1 to 10w; r l = 4 w 1% v os output offset voltage 250 mv svr supply voltage rejection r g = 10k w c3 = 22 m f f = 100hz c3 = 100 m f 45 50 57 db r i input resistance 50 k w g v voltage gain 33 35 37 db e in input noise voltage r g = 50 w (*) r g = 10k w (*) r g = 50 w (**) r g = 10k w (**) 2 2.5 2.7 3.2 m v m v m v m v (*) curve a (**) 22hz to 22khz TDA7350A 3/22
figure 1: stereo test and appication circuit figure 2: p.c. board and layout (stereo) of the circuit of fig. 1 (1:1 scale) 1000 m f 220 m f 1000 m f 220 m f TDA7350A 4/22
figure 3: bridge test and appication circuit figure 4: p.c. board and layout (bridge) of the circuit of fig. 3 (1:1 scale) TDA7350A 5/22
recommended values of the external components (ref to the stereo test and applica- tion circuit) component recommended value purpose larger than the recomm. value smaller than the recomm. value c1 0.22 m f input decoupling (ch1) c2 0.22 m f input decoupling (ch2) c3 100 m f supply voltage rejection filtering capacitor longer turn-on delay time worse supply voltage rejection. shorter turn-on delay time danger of noise (pop) c4 22 m f stand-by on/off delay delayed turn-off by stand-by switch danger of noise (pop) c5 220 m f (min) supply by-pass danger of oscillations c6 100nf (min) supply by-pass danger of oscillations c7 2200 m f output decoupling ch2 - decrease of low frequency cut off - longer turn on delay - increase of low frequency cut off - shorter turn on delay figure 5: output power vs. s upply voltage (stereo) figure 6: output power vs. supply voltage (stereo) figure 8: output power vs. supply voltage (bridge) figure 7: output power vs. supply voltage (stereo) TDA7350A 6/22
figure 11: distortion vs output power (stereo) figure 12: distortion vs output power (stereo) figure 9: output power vs. supply voltage (bridge) figure 10: drain current vs supply voltage (stereo) figure 13: distortion vs output power (stereo) figure 14: distortion vs output power (bridge) TDA7350A 7/22
figure 17: svr vs. frequency & c svr ; (bridge) figure 18: svr vs. frequency & c svr ; (bridge) figure 15: svr vs. frequency & c svr (stereo) figure 16: svr vs. frequency & c svr ; (stereo) figure 19: crosstalk vs. frequency (stereo) figure 20: power dissipation & efficiency vs. output power (stereo) r g r g r g r g r g TDA7350A 8/22
amplifier organization the TDA7350A has been developed taking care of the key concepts of the modern power audio amplifier for car radio such as: space and costs saving due to the minimized external count, ex- cellent electrical performances, flexibility in use, superior reliability thanks to a built-in array of pro- tections. as a result the following performances has been achieved: no need of bootstrap capacitors even at the highest output power levels absolute stability without exter- nal compensation thanks to the in- novative out stage configuration, also allowing internally fixed closed loop lower than competi- tors low gain (30db stereo fixed without any external components) in order to minimize the output noise and op- timize svr silent mute/st-by function featur- ing absence of pop on/off noise high svr stereo/bridge operation without addition of external component ac/dc short circuit protection (to gnd, to v s , across the load) loudspeaker protection dump protection esd protection block description polarization the device is organized with the gain resistors di- rectly connected to the signal ground pin i.e. with- out gain capacitors (fig. 24). the non inverting inputs of the amplifiers are con- nected to the svr pin by means of resistor divid- ers, equal to the feedback networks. this allows the outputs to track the svr pin which is suffi- ciently slow to avoid audible turn-on and turn-off transients. svr the voltage ripple on the outputs is equal to the one on svr pin: with appropriate selection of c svr , more than 55db of ripple rejection can be obtained. delayed turn-on (muting) the c svr sets a signal turn-on delay too. a circuit is included which mutes the device until the volt- age on svr pin reaches ~2.5v typ (fig. 25). the mute function is obtained by duplicating the input differential pair (fig. 26): it can be switched to the signal source or to an internal mute input. this feature is necessary to prevent transients at the inputs reaching the loudspeaker(s) immediately figure 21: power dissipation & efficiency vs. output power (stereo) figure 22: power dissipation & efficiency vs. output power (bridge) figure 23: power dissipation & efficiency vs. output power (bridge) TDA7350A 9/22
after power-on). fig. 25 represents the detailed turn-on transient with reference to the stereo configuration. at the power-on the output dec oupling capacitors are charged through an internal path but the de- vice itself remains switched off (phase 1 of the represented diagram). when the outputs reach the voltage level of about 1v (this means that there is no presence of short circuits) the device switches on, the svr capaci- tor starts charging itself and the output tracks ex- actly the svr pin. during this phase the device is muted until the svr reaches the "play" threshold (~2.5v typ.), af- ter that the music signal starts being played. stereo/bridge switching there is also no need for external components for changing from stereo to bridge configuration (figg. 24-27). a simple short circuit between two pins allows phase reversal at one output, yet maintaining the quiescent output voltage. stand-by the device is also equipped with a stand-by func- tion, so that a low current, and hence low cost switch, can be used for turn on/off. stability the device is provided with an internal compen- sation wich allows to reach low values of closed loop gain. in this way better performances on s/n ratio and svr can be obtained. figure 24: block diagram; stereo configuration TDA7350A 10/22
figure 25: turn-on delay circuit TDA7350A 11/22
figure 26: mute function diagram figure 27: block diagram; bridge configuration TDA7350A 12/22
output stage poor current capability and low cutoff frequency are well known limits of the standard lateral pnp. composite pnp-npn power output stages have been widely used, regardless their high saturation drop. this drop can be overcome only at the ex- pense of external components, namely, the boot- strap capacitors. the availability of 4a isolated collector pnp (icv pnp) adds versatility to the design. the performance of this component, in terms of gain, v cesat and cut-off frequency, is shown in fig. 28, 29, 30 respectively. it is realized in a new bipolar technology, characterized by top- bottom isolation techniques, allowing the imple- mentation of low leakage diodes, too. it guaran- tees bv ceo > 20v and bv cbo > 50v both for npn and pnp transistors. basically, the connec- tion shown in fig. 31 has been chosen. first of all because its voltage swing is rail-to-rail, limited only by the vcesat of the output transistors, which are in the range of 0.3 w each. then, the gain vout/vin is greater than unity, approxi- mately 1+r2/r1. (vcc/2 is fixed by an auxiliary amplifier common to both channel). it is possible, controlling the amount of this local feedback, to force the loop gain (a . b ) to less than unity at fre- quencies for which the phase shift is 180. this means that the output buffer is intrinsically stable and not prone to oscillation. in contrast, with the circuit of fig. 32, the solution adopted to reduce the gain at high frequencies is the use of an external rc network. amplifier block diagram the block diagram of each voltage amplifier is shown in fig. 33. regardless of production spread, the current in each final stage is kept low, with enough margin on the minimum, below which cross-over distortion would appear. figure 28: icv - pnp gain vs. i c figure 29: icv - pnp v ce(sat ) vs. i c figure 30: icv - pnp cut-off frequency vs. i c figure 31: the new output stage TDA7350A 13/22
built-in protection systems short circuit protection the maximum current the device can deliver can be calculated by considering the voltage that may be present at the terminals of a car radio amplifier and the minimum load impedance. apart from consideration concerning the area of the power transistors it is not difficult to achieve peak currents of this magnitude (5a peak). however, it becomes more complicated if ac and dc short circuit protection is also required.in par- ticular,with a protection circuit which limits the output current following the soa curve of the out- put transistors it is possible that in some condi- tions (highly reactive loads, for example) the pro- tection circuit may intervene during normal operation. for this reason each amplifier has been equipped with a protection circuit that inter- venes when the output current exceeds 4a. fig 34 shows the protection circuit for an npn power transistor (a symmetrical circuit applies to pnp).the vbe of the power is monitored and gives out a signal,available through a cascode. this cascode is used to avoid the intervention of the short circuit protection when the saturation is below a given limit. the signal sets a flip-flop which forces the amplifier outputs into a high impedance state. in case of dc short circuit when the short circuit is removed the flip-flop is reset and restarts the circuit (fig. 38). in case of ac short circuit or load shorted in bridge configuration, the device is con- tinuously switched in on/off conditions and the current is limited. figure 33: amplifier block diagram figure 32: a classical output stage figure 34: circuitry for short circuit detection TDA7350A 14/22
load dump voltage surge the tda 7350a has a circuit which enables it to withstand a voltage pulse train on pin 9, of the type shown in fig. 36. if the supply voltage peaks to more than 40v, then an lc filter must be inserted between the supply and pin 9, in order to assure that the pulses at pin 9 will be held within the limits shown. a suggested lc network is shown in fig. 35. with this network, a train of pulses with amplitude up to 120v and width of 2ms can be applied at point a. this type of protection is on when the supply voltage (pulse or dc) exceeds 18v. for this reason the maximum operating supply volt- age is 18v. polarity inversion high current (up to 10a) can be handled by the device with no damage for a longer period than the blow-out time of a quick 2a fuse (normally connected in series with the supply). this fea- tures is added to avoid destruction, if during fitting to the car, a mistake on the connection of the supply is made. open ground when the radio is in the on condition and the ground is accidentally opened, a standard audio amplifier will be damaged. on the TDA7350A pro- tection diodes are included to avoid any damage. dc voltage the maximum operating dc voltage for the TDA7350A is 18v. however the device can with- stand a dc voltage up to 28v with no damage. this could occur during winter if two batteries are series connected to crank the engine. thermal shut-down the presence of a thermal limiting circuit offers the following advantages: 1)an overload on the output (even if it is perma- nent), or an excessive ambient temperature can be easily withstood. 2)the heatsink can have a smaller factor of safety compared with that of a conventional circuit. there is no device damage in the case of excessive junction temperature: all hap- pens is that p o (and therefore p tot ) and i d are reduced. the maximum allowable power dissipation de- pends upon the size of the external heatsink (i.e. its thermal resistance); fig. 37 shows the dissipa- ble power as a function of ambient temperature for different thermal resistance. loudspeaker prot ection the TDA7350A guarantees safe operations even for the loudspeaker in case of accidental shortcir- cuit. whenever a single out to gnd, out to v s short circuit occurs both the outputs are switched off so limiting dangerous dc current flowing through the loudspeaker. figure 35 figure 36 figure 37: maximum allowable power dissipation vs. ambient temperature figure 38: restart circuit TDA7350A 15/22
application hints this section explains briefly how to get the best from the TDA7350A and presents some applica- tion circuits with suggestions for the value of the components.these values can change depending on the characteristics that the designer of the car radio wants to obtain,or other parts of the car ra- dio that are connected to the audio block. to optimize the performance of the audio part it is useful (or indispensable) to analyze also the parts outside this block that can have an interconnec- tion with the amplifier. this method can provide components and system cost saving. reducing turn on-off pop the TDA7350A has been designed in a way that the turn on(off) transients are controlled through the charge(discharge) of the csvr capacitor. as a result of it, the turn on(off) transient spec- trum contents is limited only to the subsonic range.the following section gives some brief notes to get the best from this design feature(it will refer mainly to the stereo application which appears to be in most cases the more critical from the pop viewpoint.the bridge connection in fact,due to the common mode waveform at the outputs,does not give pop effect). turn-on fig. 39 shows the output waveform (before and after the "a" weighting filter) compared to the value of csvr. better pop-on performance is obtained with higher csvr values (the recommended range is from 22uf to 220uf). the turn-on delay (during which the amplifier is in mute condition) is a function essentially of : c out , c svr . being: t1 ? 120 c out t2 ? 1200 c svr the turn-on delay is given by: t1+t2 stereo t2 bridge the best performance is obtained by driving the st-by pin with a ramp having a slope slower than 2v/ms figure 39: a) c svr = 22 m f b) c svr = 47 m f c) c svr = 100 m f TDA7350A 16/22
turn-off a turn-off pop can occur if the st-by pin goes low with a short time constant (this can occur if other car radio sections, preamplifiers,radio.. are sup- plied through the same st-by switch). this pop is due to the fast switch-off of the inter- nal current generator of the amplifier. if the voltage present across the load becomes rapidly zero (due to the fast switch off) a small pop occurs, depending also on cout,rload. the parameters that set the switch off time con- stant of the st-by pin are: the st-by capacitor (cst-by) the svr capacitor (csvr) resistors connected from st-by pin to ground (rext) the time constant is given by : t ? csvr 2000 w // rext + cst-by 2500 w // rext the suggested time constants are : t > 120ms with c out =1000 m f,r l = 4ohm,stereo t > 170ms with c out =2200 m f,r l = 4ohm,stereo if rext is too low the csvr can become too high and a different approach may be useful (see next section). figg 40, 41 show some types of electronic switches ( m p compatible) suitable for supplying the st-by pin (it is important that qsw is able to saturate with v ce 150mv). also for turn off pop the bridge configuration is su- perior, in particular the st-by pin can go low faster. global approach to solving pop problem by using the muting/turn on delay function in the real case turn-on and turn-off pop problems are generated not only by the power amplifier,but also (very often) by preamplifiers,tone controls,ra- dios etc. and transmitted by the power amplifier to the loudspeaker. a simple approach to solving these problems is to use the mute characteristics of the tda7350. if the svr pin is at a voltage below 1.5 v, the mute attenuation (typ)is 30db .the amplifier is in play mode when vsvr overcomes 3.5 v. with the circuit of fig 42 we can mute the amplifier for a time ton after switch-on and for a time toff after switch-off.during this period the circuitry that precedes the power amplifier can produce spuri- ous spikes that are not transmitted to the loud- speaker. this can give back a very simple design of this circuitry from the pop point of view. a timing diagram of this circuit is illustrated in fig 43. other advantages of this circuit are: - a reduced time constant allowance of stand-by pin turn off.consequently it is possible to drive all the car-radio with the signal that drives this pin. -a better turn-off noise with signal on the output. to drive two stereo amplifiers with this circuit it is possible to use the circuit of fig 44. figure 40 figure 41 TDA7350A 17/22
figure 42 figure 43 TDA7350A 18/22
balance input in bridge configuration a helpful characteristic of the TDA7350A is that,in bridge configuration, a signal present on both the input capacitors is amplified by the same amount and it is present in phase at the outputs,so this signal does not produce effects on the load.the typical value of cmrr is 46 db. looking at fig 45, we can see that a noise signal from the ground of the power amplifier to the ground of the hypothetical preamplifier is ampli- fied of a factor equal to the gain of the amplifier (2 gv). using a configuration of fig. 46 the same ground noise is present at the output multiplied by the factor 2 gv/200. this means less distortion,less noise (e.g. motor cassette noise ) and/or a simplification of the lay- out of pc board. the only limitation of this balanced input is the maximum amplitude of common mode signals (few tens of millivolt) to avoid a loss of output power due to the common mode signal on the output, but in a large number of cases this signal is within this range. high gain ,low noise application the following section describes a flexible pream- plifier having the purpose to increase the gain of the TDA7350A. figure 45 figure 46 figure 44 TDA7350A 19/22
a two transistor network (fig. 47) has been adopted whose components can be changed in order to achieve the desired gain without affecting the good performances of the audio amplifier itself. the recommended values for 40 db overall gain are : resistance stereo bridge r1 r2 r3 r4 10k w 4.3k w 10k w 50k w 10kw 16k w 24k w 50k w figure 47 TDA7350A 20/22
multiwatt11 package mechanical data 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 0.88 0.95 0.035 0.037 g 1.45 1.7 1.95 0.057 0.067 0.077 g1 16.75 17 17.25 0.659 0.669 0.679 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 0.87 0.886 l2 17.4 18.1 0.685 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 4.73 5.08 5.43 0.186 0.200 0.214 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 TDA7350A 21/22
information furnished is believed to be accurate and reliable. however, sgs-thomson microelectronics assumes no responsibility for the consequences 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 sgs-thomson microelectronics. specifications men- tioned in this publi cation are subject to change without not ice. this publication sup ersedes and replaces all information previously supplied. sgs-thomson microelectronics products are not authorized for use as critical components in life support dev ices or systems without ex- press written approval of sgs-thomson microelectronics. ? 1995 sgs-thomson microelectronics - all rights reserved multiwatt? is a registered trademrk of the sgs-thomson microelectronics sgs-thomson microelectronics group of companies aust ralia - brazil - france - germany - hong kong - italy - japan - korea - malaysia - malta - morocco - the netherlands - singapore - spain - sweden - switzerland - taiwan - thaliand - united k ingdom - u.s.a. TDA7350A 22/22

▲Up To Search▲

Price & Availability of TDA7350A

	To Download TDA7350A Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .