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features description typical application circuit TPA4860 slos164b ? september 1996 ? revised june 2004 1-w mono audio power amplifier 1-w btl output (5 v, 0.2 % thd+n) 3.3-v and 5-v operation no output coupling capacitors required shutdown control (i dd = 0.6 a) headphone interface logic uncompensated gains of 2 to 20 (btl mode) surface-mount packaging thermal and short-circuit protection high power supply rejection(56-db at 1 khz) lm4860 drop-in compatible the TPA4860 is a bridge-tied load (btl) audio power amplifier capable of delivering 1 w of continuous average power into an 8-w load at 0.4 % thd+n from a 5-v power supply in voiceband frequencies (f < 5 khz). a btl configuration eliminates the need for external coupling capacitors on the output in most applications. gain is externally configured by means of two resistors and does not require compensation for settings of 2 to 20. features of this amplifier are a shutdown function for power-sensitive applications as well as headphone interface logic that mutes the output when the speaker drive is not required. internal thermal and short-circuit protection increases device reliability. it also includes headphone interface logic circuitry to facilitate headphone applications. the amplifier is available in a 16-pin soic surface-mount package that reduces board space and facilitates automated assembly. please be aware that an important notice concerning availability, standard warranty, and use in critical applications of texas instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. production data information is current as of publication date. copyright ? 1996?2004, texas instruments incorporated products conform to specifications per the terms of the texas instruments standard warranty. production processing does not necessarily include testing of all parameters. www .ti.com audio input bias control v d d 1 w 1210 15 1, 4, 8, 9, 16 v o 1 v o 2 v d d 2 3 7 6 5 14 13 1 1 gainin + in byp ass hp-in1hp-in2 hp-sense shutdown v d d /2 c i r i r f v d d r p u headphone plug nc c b c s 12 3 4 5 6 7 8 1615 14 13 12 1 1 10 9 gnd shutdown hp-sense gnd byp ass hp-in1hp-in2 gnd gndv o 2 in+in v d d gainv o 1 gnd d p ackage (t op view)
absolute maximum ratings dissipation rating table recommended operating conditions TPA4860 slos164b ? september 1996 ? revised june 2004 these devices have limited built-in esd protection. the leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the mos gates. available options packaged device t a small outline (d) ?40c to 85c TPA4860d over operating free-air temperature range (unless otherwise noted) (1) unit v dd supply voltage 6 v v i input voltage ?0.3 v to v dd +0.3 v continuous total power dissipation internally limited (see dissipation rating table) t a operating free-air temperature range ?40c to 85c t stg storage temperature range ?65c to 150c lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 260c (1) stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. package t a 25c derating factor t a = 70c t a = 85c d 1250 mw 10 mw/c 800 mw 650 mw min max unit v dd supply voltage 2.7 5.5 v v dd = 3.3 v 1.25 2.7 v v ic common-mode input voltage v dd = 5 v 1.25 4.5 v t a operating free-air temperature ?40 85 c 2 www .ti.com
electrical characteristics operating characteristics TPA4860 slos164b ? september 1996 ? revised june 2004 at specified free-air temperature range, v dd = 3.3 v (unless otherwise noted) TPA4860 parameter test conditions unit min typ max v oo output offset voltage (measured differentially) see (1) 5 20 mv supply ripple rejection ratio v dd = 3.2 v to 3.4 v 75 db i dd quiescent current 2.5 ma i dd(m) quiescent current, mute mode 750 a i dd(sd) quiescent current, shutdown mode 0.6 a v ih high-level input voltage (hp-in) 1.7 v v il low-level input voltage (hp-in) 1.7 v v oh high-level output voltage (hp-sense) i o = 100 a 2.5 2.8 v v ol low-level output voltage (hp-sense) i o = -100 a 0.2 0.8 v (1) at 3 v < v dd < 5 v the dc output voltage is approximately v dd /2. v dd = 3.3 v, t a = 25c, r l = 8 w TPA4860 parameter test conditions unit min typ max thd = 0.2%, f = 1 khz, a v = 2 350 mw p o output power (1) thd = 2%, f = 1 khz, a v = 2 500 mw b om maximum output power bandwidth gain = 10, thd = 2% 20 khz b 1 unity-gain bandwidth open loop 1.5 mhz btl f = 1 khz 56 db supply ripple rejection ratio se f = 1 khz 30 db v n noise output voltage (2) gain = 2 20 v (1) output power is measured at the output terminals of the device. (2) noise voltage is measured in a bandwidth of 20 hz to 20 khz. 3 www .ti.com
electrical characteristics operating characteristics TPA4860 slos164b ? september 1996 ? revised june 2004 at specified free-air temperature range, v dd = 5 v (unless otherwise noted) TPA4860 parameter test conditions unit min typ max v oo output offset voltage see (1) 5 20 mv supply ripple rejection ratio v dd = 4.9 v to 5.1 v 70 db i dd supply current 3.5 ma i dd(m) supply current, mute 750 a i dd(sd) supply current, shutdown 0.6 a v ih high-level input voltage (hp-in) 2.5 v v il low-level input voltage (hp-in) 2.5 v v oh high-level output voltage (hp-sense) i o = 500 a 2.5 2.8 v v ol low-level output voltage (hp-sense) i o = -500 a 0.2 0.8 v (1) at 3 v < v dd < 5 v the dc output voltage is approximately v dd /2. v dd = 5 v, t a = 25c, r l = 8 w TPA4860 parameter test conditions unit min typ max thd = 0.2%, f = 1 khz, a v = 2 1000 mw p o output power (1) thd = 2%, f = 1 khz, a v = 2 1100 mw b om maximum output power bandwidth gain = 10, thd = 2% 20 khz b 1 unity-gain bandwidth open loop 1.5 mhz btl f = 1 khz 56 db supply ripple rejection ratio se f = 1 khz 30 db v n noise output voltage (2) gain = 2 20 v (1) output power is measured at the output terminals of the device. (2) noise voltage is measured in a bandwidth of 20 hz to 20 khz. 4 www .ti.com
typical characteristics TPA4860 slos164b ? september 1996 ? revised june 2004 table of graphs figure v oo output offset voltage distribution 1,2 i dd supply current distribution vs free-air temperature 3,4 vs frequency 5, 6, 7, 8, 9, 10,11,15, 16,17,18 thd+n total harmonic distortion plus noise vs output power 12, 13, 14, 19,20,21 i dd supply current vs supply voltage 22 v n output noise voltage vs frequency 23, 24 maximum package power dissipation vs free-air temperature 25 power dissipation vs output power 26, 27 maximum output power vs free-air temperature 28 vs load resistance 29 output power vs supply voltage 30 open-loop frequency response vs frequency 31 supply ripple rejection ratio vs frequency 32, 33 distribution of TPA4860 distribution of TPA4860 output offset voltage output offset voltage figure 1. figure 2. 5 www .ti.com number of amplifiers 2010 0 v o o ? output offset v oltage ? mv 2515 5 ?3 ?2 ?1 0 1 2 3 4 5 6 7 v c c = 3.3 v number of amplifiers 2010 0 v o o ? output offset v oltage ? mv 2515 5 v c c = 5 v ?3 ?2 ?1 0 1 2 3 4 5 6 7
TPA4860 slos164b ? september 1996 ? revised june 2004 supply current distribution supply current distribution vs vs free-air temperature free-air temperature figure 3. figure 4. total harmonic distortion + noise total harmonic distortion + noise vs vs frequency frequency figure 5. figure 6. 6 www .ti.com ? supply current ? ma 3.5 21 0 t a ? free-air t emperature ? c ?20 25 2.51.5 0.5 v c c = 5 v i dd 3 85 4.5 4 t ypical ? supply current ? ma 3.5 21 0 t a ? free-air t emperature ? c ?20 25 2.51.5 0.5 v c c = 3.3 v i dd 3 85 t ypical 20 10 1 0.1 0.01 100 1 k 10 k 20 k f ? frequency ? hz v d d = 5 v p o = 1 w a v = ?2 v/v r l = 8 w c b = 0.1 m f c b = 1 m f thd+n ? t otal harmonic distortion plus noise ? % 20 10 1 0.1 0.01 100 1 k 10 k 20 k f ? frequency ? hz v d d = 5 v p o = 1 w a v = ?10 v/v r l = 8 w c b = 0.1 m f c b = 1 m f thd+n ? t otal harmonic distortion plus noise ? %
TPA4860 slos164b ? september 1996 ? revised june 2004 total harmonic distortion + noise total harmonic distortion + noise vs vs frequency frequency figure 7. figure 8. total harmonic distortion + noise total harmonic distortion + noise vs vs frequency frequency figure 9. figure 10. 7 www .ti.com 20 10 1 0.1 0.01 100 1 k 10 k 20 k f ? frequency ? hz v d d = 5 v p o = 1 w a v = ?20 v/v r l = 8 w c b = 0.1 m f c b = 1 m f thd+n ? t otal harmonic distortion plus noise ? % 20 10 1 0.1 0.01 100 1 k 10 k 20 k f ? frequency ? hz v d d = 5 v p o = 0.5 w a v = ?2 v/v r l = 8 w c b = 0.1 m f c b = 1 m f thd+n ? t otal harmonic distortion plus noise ? % 20 10 1 0.1 0.01 100 1 k 10 k 20 k f ? frequency ? hz v d d = 5 v p o = 0.5 w a v = ?10 v/v r l = 8 w c b = 0.1 m f c b = 1 m f thd+n ? t otal harmonic distortion plus noise ? % 20 10 1 0.1 0.01 100 1 k 10 k 20 k f ? frequency ? hz thd+n ? t otal harmonic distortion plus noise ? % v d d = 5 v p o = 0.5 w a v = ?20 v/v r l = 8 w c b = 0.1 m f c b = 1 m f
TPA4860 slos164b ? september 1996 ? revised june 2004 total harmonic distortion + noise total harmonic distortion + noise vs vs frequency output power figure 11. figure 12. total harmonic distortion + noise total harmonic distortion + noise vs vs output power output power figure 13. figure 14. 8 www .ti.com 0.02 10 1 0.1 0.01 0.1 1 p o ? output power ? w thd+n ? t otal harmonic distortion plus noise ? % v d d = 5 v a v = ?2 v/v r l = 8 w f = 20 hz c b = 0.1 m f 2 c b = 1 m f 20 10 1 0.1 0.01 100 1 k 10 k 20 k f ? frequency ? hz thd+n ? t otal harmonic distortion plus noise ? % v d d = 5 v a v = ?10 v/v single ended r l = 8 w p o = 250 mw r l = 32 w p o = 60 mw 0.02 10 1 0.1 0.01 0.1 1 p o ? output power ? w thd+n ? t otal harmonic distortion plus noise ? % v d d = 5 v a v = ?2 v/v r l = 8 w f = 1 khz 2 c b = 0.1 m f 0.02 10 1 0.1 0.01 0.1 1 p o ? output power ? w thd+n ? t otal harmonic distortion plus noise ? % v d d = 5 v a v = ?2 v/v r l = 8 w f = 20 khz c b = 0.1 m f 2
TPA4860 slos164b ? september 1996 ? revised june 2004 total harmonic distortion + noise total harmonic distortion + noise vs vs frequency frequency figure 15. figure 16. total harmonic distortion + noise total harmonic distortion + noise vs vs frequency frequency figure 17. figure 18. 9 www .ti.com 20 10 1 0.1 0.01 100 1 k 10 k 20 k f ? frequency ? hz thd+n ? t otal harmonic distortion plus noise ? % c b = 1 m f v d d = 3.3 v p o = 350 mw r l = 8 w a v = ?2 v/v c b = 0.1 m f 20 10 1 0.1 0.01 100 1 k 10 k 20 k f ? frequency ? hz thd+n ? t otal harmonic distortion plus noise ? % c b = 1 m f v d d = 3.3 v p o = 350 mw r l = 8 w a v = ?10 v/v c b = 0.1 m f 20 10 1 0.1 0.01 100 1 k 10 k 20 k f ? frequency ? hz thd+n ? t otal harmonic distortion plus noise ? % v d d = 3.3 v p o = 350 mw r l = 8 w a v = ?20 v/v c b = 1 m f c b = 0.1 m f 20 10 1 0.1 0.01 100 1 k 10 k 20 k f ? frequency ? hz thd+n ? t otal harmonic distortion plus noise ? % v d d = 3.3 v a v = ?10 v/v single ended r l = 32 w p o = 60 mw r l = 8 w p o = 250 mw
TPA4860 slos164b ? september 1996 ? revised june 2004 total harmonic distortion + noise total harmonic distortion + noise vs vs output power output power figure 19. figure 20. total harmonic distortion + noise supply current vs vs output power supply voltage figure 21. figure 22. 10 www .ti.com 0.02 10 1 0.1 0.01 0.1 1 p o ? output power ? w thd+n ? t otal harmonic distortion plus noise ? % v d d = 3.3 v a v = ?2 v/v r l = 8 w f = 20 hz c b = 0.1 m f 2 c b = 1.0 m f 0.02 10 1 0.1 0.01 0.1 1 p o ? output power ? w thd+n ? t otal harmonic distortion plus noise ? % v d d = 3.3 v a v = ?2 v/v r l = 8 w f = 1 khz c b = 0.1 m f 2 20 m 10 1 0.1 0.01 0.1 1 p o ? output power ? w thd+n ? t otal harmonic distortion plus noise ? % v d d = 3.3 v a v = ?2 v/v r l = 8 w f = 20 khz c b = 0.1 m f 2 ? supplu current ? ma i d d 2.5 52 1 0 3 3.5 v d d ? supply v oltage ? v 4 4.5 5 5.5 43 t a = 0 c t a = 85 c t a = 25 c t a = ?20 c
TPA4860 slos164b ? september 1996 ? revised june 2004 output noise voltage output noise voltage vs vs frequency frequency figure 23. figure 24. maximum package power dissipation power dissipation vs vs free-air temperature output power figure 25. figure 26. 11 www .ti.com 20 10 3 10 2 10 1 1 100 1 k 10 k 20 k f ? frequency ? hz v c c = 5 v v 0 1 +v 0 2 v 0 1 v 0 2 ? output noise v oltage ? v n v m maximum package power dissipation ? w ?25 1.5 1 0.5 0 0 75 175 t a ? free-air t emperature ? c 25 50 100 125 150 1.250.75 0.25 power dissipation ? w 1.5 1 0.5 0 0 0.75 1.75 p o ? output power ? w 0.25 0.5 1 1.25 1.5 v d d = 5 v r l = 4 w r l = 8 w r l = 16 w 20 10 3 10 2 10 1 1 100 1 k 10 k 20 k f ? frequency ? hz v c c = 3.3 v v 0 2 v 0 1 v 0 1 +v 0 2 ? output noise v oltage ? v n v m
TPA4860 slos164b ? september 1996 ? revised june 2004 power dissipation maximum output power vs vs output power free-air temperature figure 27. figure 28. output power output power vs vs load resistance supply voltage figure 29. figure 30. 12 www .ti.com ? power output ? w 4 1.40.8 0.4 0 8 20 36 load resistance ? w 12 16 24 28 32 1 0.60.2 v c c = 5 v v c c = 3.3 v p o a v = ?2 v/v f = 1 khzc b = 0.1 m f thd+n 1% 1.2 48 40 44 ? power output ? w 3 1.75 1 0.5 0 3.5 5 supply v oltage ? v 4 4.5 5.5 1.250.75 0.25 p o 1.5 a v = ?2 v/v f = 1 khzc b = 0.1 m f thd+n 1% 2.5 2 r l = 8 w r l = 4 w r l = 16 w 1 0.5 0.25 0 0 0.75 p o ? output power ? w 0.25 0.5 v d d = 3.3 v r l = 4 w r l = 8 w r l = 16 w 0.75 power dissipation ? w 160 4020 0 0 0.25 1.50 0.5 0.75 1 r l = 16 w ? free-air t emperature ? p o ? maximum output power ? w 1.25 r l = 8 w r l = 4 w c t a 8060 120100 140
TPA4860 slos164b ? september 1996 ? revised june 2004 supply ripple rejection ratio vs open-loop frequency response frequency figure 31. figure 32. supply ripple rejection ratio vs frequency figure 33. 13 www .ti.com 100 0 ?90 ?100 1 k 10 k 20 k f ? frequency ? hz v d d = 5 v r l = 8 w bridge-t ied load c b = 0.1 m f c b = 1 m f ?80 ?70 ?60 ?50 ?40 ?30 ?20 ?10 supply ripple rejection ratio ? db g ? gain ? db 10 100 6020 ?20 100 100 k f ? frequency ? hz v d d = 5 v r l = 8 w c b = 0.1 m f 1 k 10 k 1 m 10 m 8040 0 45 ?45 ?135 ?225 0 ?90 ?180 phase gain phase 100 0 ?90 ?100 1 k 10 k 20 k f ? frequency ? hz c b = 0.1 m f c b = 1 m f ?80 ?70 ?60 ?50 ?40 ?30 ?20 ?10 v d d = 5 v r l = 8 w single ended supply ripple rejection ratio ? db
application information bridged-tied load versus single-ended mode (1) (2) TPA4860 slos164b ? september 1996 ? revised june 2004 figure 34 shows a linear audio power amplifier (apa) in a bridge-tied load (btl) configuration. a btl amplifier actually consists of two linear amplifiers driving both ends of the load. there are several potential benefits to this differential drive configuration but initially let us consider power to the load. the differential drive to the speaker means that as one side is slewing up the other side is slewing down and vice versa. this, in effect, doubles the voltage swing on the load as compared to a ground-referenced load. plugging twice the voltage into the power equation, where voltage is squared, yields 4 times the output power from the same supply rail and load impedance (see equation 1 ). figure 34. bridge-tied load configuration in a typical computer sound channel operating at 5 v, bridging raises the power into an 8-w speaker from a singled-ended (se) limit of 250 mw to 1 w. in sound power, that is a 6-db improvement which is loudness that can be heard. in addition to increased power there are frequency response concerns; consider the single-supply se configuration shown in figure 35 . a coupling capacitor is required to block the dc offset voltage from reaching the load. these capacitors can be quite large (approximately 40 f to 1000 f); so, they tend to be expensive, occupy valuable pcb area, and have the additional drawback of limiting low-frequency performance of the system. this frequency-limiting effect is due to the high-pass filter network created with the speaker impedance and the coupling capacitance and is calculated with equation 2 . for example, a 68-f capacitor with an 8-w speaker would attenuate low frequencies below 293 hz. the btl configuration cancels the dc offsets, which eliminates the need for the blocking capacitors. low-frequency performance is then limited only by the input network and speaker response. cost and pcb space are also minimized by eliminating the bulky coupling capacitor. 14 www .ti.com p o w e r v ( r m s ) 2 r l v ( r m s ) v o ( p p ) 2 2 r l 2x v o ( p p ) v o ( p p ) v o ( p p ) v d d v d d f c 1 2 r l c c
btl amplifier efficiency TPA4860 slos164b ? september 1996 ? revised june 2004 application information (continued) figure 35. single-ended configuration increasing power to the load does carry a penalty of increased internal power dissipation. the increased dissipation is understandable considering that the btl configuration produces 4 times the output power of the se configuration. internal dissipation versus output power is discussed further in the thermal considerations section. linear amplifiers are notoriously inefficient. the primary cause of these inefficiencies is voltage drop across the output stage transistors. the internal voltage drop has two components. one is the headroom or dc voltage drop that varies inversely to output power. the second component is due to the sine-wave nature of the output. the total voltage drop can be calculated by subtracting the rms value of the output voltage from v dd . the internal voltage drop multiplied by the rms value of the supply current, i dd(rms) , determines the internal power dissipation of the amplifier. an easy-to-use equation to calculate efficiency starts out as being equal to the ratio of power from the power supply to the power delivered to the load. to accurately calculate the rms values of power in the load and in the amplifier, the current and voltage waveform shapes must first be understood (see figure 36 ). figure 36. voltage and current waveforms for btl amplifiers although the voltages and currents for se and btl are sinusoidal in the load, currents from the supply are different between se and btl configurations. in an se application the current waveform is a half-wave rectified shape, whereas in btl it is a full-wave rectified waveform. this means rms conversion factors are different. keep in mind that for most of the waveform both the push and pull transistor are not on at the same time, which supports the fact that each amplifier in the btl device only draws current from the supply for half the waveform. the following equations are the basis for calculating amplifier efficiency. 15 www .ti.com r l c c v o ( p p ) v o ( p p ) v d d v l ( r m s ) v o i d d i d d ( r m s )
(3) (4) TPA4860 slos164b ? september 1996 ? revised june 2004 application information (continued) table 1 employs equation 4 to calculate efficiencies for four different output power levels. note that the efficiency of the amplifier is quite low for lower power levels and rises sharply as power to the load is increased, resulting in a nearly flat internal power dissipation over the normal operating range. note that the internal dissipation at full output power is less than in the half power range. calculating the efficiency for a specific system is the key to proper power supply design. for a stereo 1-w audio system with 8-w loads and a 5-v supply, the maximum draw on the power supply is almost 3.25 w. table 1. efficiency vs output power in 5-v 8-w btl systems peak-to-peak internal output power efficiency voltage dissipation (w) (%) (v) (w) 0.25 31.4 2.00 0.55 0.50 44.4 2.83 0.62 1.00 62.8 4.00 0.59 1.25 70.2 4.47 (1) 0.53 (1) high peak voltages cause the thd to increase. a final point to remember about linear amplifiers whether they are se or btl configured is how to manipulate the terms in the efficiency equation to utmost advantage when possible. note that in equation 4 , v dd is in the denominator. this indicates that as v dd goes down, efficiency goes up. for example, if the 5-v supply is replaced with a 10-v supply (TPA4860 has a maximum recommended v dd of 5.5 v) in the calculations of table 1 , then efficiency at 1 w would fall to 31% and internal power dissipation would rise to 2.18 w from 0.59 w at 5 v. then, for a stereo 1-w system from a 10-v supply, the maximum draw would be almost 6.5 w. choose the correct supply voltage and speaker impedance for the application. 16 www .ti.com e f f i c i e n c y o f a b t l c o n f i g u r a t i o n v p 2 v d d p l r l 2 1 2 2 v d d v l ( r m s ) v p 2 i d d ( r m s ) 2 v p r l p s u p v d d i d d ( r m s ) v d d 2 v p r l e f f i c i e n c y p l p s u p p l v l ( r m s ) 2 r l v p 2 2 r l where:
selection of components gain setting resistors, r f and r i (5) (6) TPA4860 slos164b ? september 1996 ? revised june 2004 figure 37 is a schematic diagram of a typical notebook computer application circuit. figure 37. TPA4860 typical notebook computer application circuit the gain for the TPA4860 is set by resistors r f and r i according to equation 5 . btl mode operation brings about the factor of 2 in the gain equation due to the inverting amplifier mirroring the voltage swing across the load. given that the TPA4860 is a mos amplifier, the input impedance is high; consequently, input leakage currents are not generally a concern although noise in the circuit increases as the value of r f increases. in addition, a certain range of r f values is required for proper start-up operation of the amplifier. taken together, it is recommended that the effective impedance seen by the inverting node of the amplifier be set between 5 kw and 20 kw. the effective impedance is calculated in equation 6 . as an example, consider an input resistance of 10 kw and a feedback resistor of 50 kw. the gain of the amplifier would be ?10 and the effective impedance at the inverting terminal would be 8.3 kw, which is well within the recommended range. for high-performance applications metal film resistors are recommended because they tend to have lower noise levels than carbon resistors. for values of r f above 50 kw, the amplifier tends to become unstable due to a pole formed from r f and the inherent input capacitance of the mos input structure. for this reason, a small compensation capacitor of approximately 5 pf should be placed in parallel with r f . in effect, this creates a low-pass filter network with the cutoff frequency defined in equation 7 . 17 www .ti.com e f f e c t i v e i m p e d a n c e r f r i r f r i g a i n 2 r f r i audio input bias control v d d = 5 v 1-winternal speaker 1210 15 1, 4, 8, 9, 16 v o 1 v o 2 v d d 2 3 7 6 5 14 13 1 1 gainin + in ? byp ass hp-in1hp-in2 hp-sense shutdown v d d /2 c i r i r f v d d r p u headphone plug nc c f 50 k w 50 k w 46 k w 46 k w c b c s
(7) input capacitor, c i (8) (9) power supply decoupling c s midrail bypass capacitor, c b (10) TPA4860 slos164b ? september 1996 ? revised june 2004 for example, if r f is 100 kw and c f is 5 pf, then f c is 318 khz, which is well outside of the audio range. in the typical application, an input capacitor, c i is required to allow the amplifier to bias the input signal to the proper dc level for optimum operation. in this case, c i and r i form a high-pass filter with the corner frequency determined in equation 8 . the value of c i is important to consider as it directly affects the bass (low-frequency) performance of the circuit. consider the example where r i is 10 kw and the specification calls for a flat bass response down to 40 hz. equation 8 is reconfigured as equation 9 . in this example, c i is 0.40 f; so, one would likely choose a value in the range of 0.47 f to 1 f. a further consideration for this capacitor is the leakage path from the input source through the input network (r i , c i ) and the feedback resistor (r f ) to the load. this leakage current creates a dc-offset voltage at the input to the amplifier that reduces useful headroom, especially in high-gain applications. for this reason a low-leakage tantalum or ceramic capacitor is the best choice. when polarized capacitors are used, the positive side of the capacitor should face the amplifier input in most applications as the dc level there is held at v dd /2, which is likely higher that the source dc level. note that it is important to confirm the capacitor polarity in the application. the TPA4860 is a high-performance cmos audio amplifier that requires adequate power supply decoupling to ensure the output total harmonic distortion (thd) is as low as possible. power supply decoupling also prevents oscillations for long lead lengths between the amplifier and the speaker. the optimum decoupling is achieved by using two capacitors of different types that target different types of noise on the power supply leads. for higher frequency transients, spikes, or digital hash on the line, a good low equivalent-series-resistance (esr) ceramic capacitor, typically 0.1 f placed as close as possible to the device v dd lead, works best. for filtering lower-frequency noise signals, a larger aluminum electrolytic capacitor of 10 f or greater placed near the power amplifier is recommended. the midrail bypass capacitor, c b , serves several important functions. during start-up or recovery from shutdown mode, c b determines the rate at which the amplifier starts up. this helps to push the start-up pop noise into the subaudible range (so low it cannot be heard). the second function is to reduce noise produced by the power supply caused by coupling into the output drive signal. this noise is from the midrail generation circuit internal to the amplifier. the capacitor is fed from a 25-kw source inside the amplifier. to keep the start-up pop as low as possible, the relationship shown in equation 10 should be maintained. as an example, consider a circuit where c b is 0.1 f, c i is 0.22 f and r i is 10 kw. inserting these values into the equation 9 , we get: 400 454 which satisfies the rule. recommended value for bypass capacitor c b is 0.1-f to 1-f ceramic or tantalum low-esr for the best thd and noise performance. 18 www .ti.com f c ( l o w p a s s ) 1 2 r f c f f c ( h i g h p a s s ) 1 2 r i c i c i 1 2 r i f c 1 c b 2 5 k w 1 c i r i
single-ended operation (11) (12) output coupling capacitor, c c (13) TPA4860 slos164b ? september 1996 ? revised june 2004 figure 38 is a schematic diagram of the recommended se configuration. in se mode configurations, the load should be driven from the primary amplifier output (v o 1, terminal 10). figure 38. singled-ended mode gain is set by the r f and r i resistors and is shown in equation 11 . because the inverting amplifier is not used to mirror the voltage swing on the load, the factor of 2 is not included. the phase margin of the inverting amplifier into an open circuit is not adequate to ensure stability, so a termination load should be connected to v o 2. this consists of a 50-w resistor in series with a 0.1-f capacitor to ground. it is important to avoid oscillation of the inverting output to minimize noise and power dissipation. the output coupling capacitor required in single-supply se mode also places additional constraints on the selection of other components in the amplifier circuit. the rules described earlier still hold with the addition of the following relationship: in the typical single-supply se configuration, an output coupling capacitor (c c ) is required to block the dc bias at the output of the amplifier, thus preventing dc currents in the load. as with the input coupling capacitor, the output coupling capacitor and impedance of the load form a high-pass filter governed by equation 13 . the main disadvantage, from a performance standpoint, is that the load impedances are typically small, which drives the low-frequency corner higher. large values of c c are required to pass low frequencies into the load. consider the example where a c c of 68 f is chosen and loads vary from 8 w, 32 w, to 47 kw. table 2 summarizes the frequency response characteristics of each configuration. 19 www .ti.com audio input v d d = 5 v 250-mwexternal speaker 1210 15 v o 1 v o 2 v d d 5 14 13 1 1 gainin + in ? byp ass v d d /2 c i r i r f c s e = 0.1 m f r s e = 50 w c c c b c s g a i n r f r i 1 c b 2 5 k w 1 c i r i 1 r l c c f c h i g h 1 2 r l c c
headphone sense circuitry, r pu TPA4860 slos164b ? september 1996 ? revised june 2004 table 2. common load impedances vs low frequency output characteristics in se mode r l c c lowest frequency 8 w 68 f 293 hz 32 w 68 f 73 hz 47,000 w 68 f 0.05 hz as table 2 indicates, most of the bass response is attenuated into 8-w loads while headphone response is adequate and drive into line level inputs (a home stereo for example) is good. the TPA4860 is commonly used in systems where there is an internal speaker and a jack for driving external loads (i.e., headphones). in these applications, it is usually desirable to mute the internal speaker(s) when the external load is in use. the headphone inputs (hp-1, hp-2) and headphone output (hp-sense) of the TPA4860 were specifically designed for this purpose. many standard headphone jacks are available with an internal single-pole single-throw (spst) switch that makes or breaks a circuit when the headphone plug is inserted. asserting either or both hp-1 and/or hp-2 high mutes the output stage of the amplifier and causes hp-sense to go high. in battery-powered applications where power conservation is critical, hp-sense can be connected to the shutdown input as shown in figure 39 . this places the amplifier in a low current state for maximum power savings. pullup resistors in the range from 1 kw to 10 kw are recommended for 5-v and 3.3-v operation. figure 39. schematic diagram of typical headphone sense application table 3 details the logic for the mute function of the TPA4860. table 3. truth table for headphone sense and shutdown functions inputs (1) output amplifier state hp-1 hp-2 shutdown hp-sense low low low low active low high low high mute high low low high mute high high low high mute x (2) x (2) high x (2) shutdown (1) inputs should never be left unconnected. (2) x = do not care 20 www .ti.com bias control 2 3 7 6 hp-in1hp-in2 hp-sense shutdown v d d r p u headphone plug nc
shutdown mode using low-esr capacitors thermal considerations 5-v versus 3.3-v operation TPA4860 slos164b ? september 1996 ? revised june 2004 the TPA4860 employs a shutdown mode of operation designed to reduce quiescent supply current, i dd(q) , to the absolute minimum level during periods of nonuse for battery-power conservation. for example, during device sleep modes or when other audio-drive currents are used (i.e., headphone mode), the speaker drive is not required. the shutdown input terminal should be held low during normal operation when the amplifier is in use. pulling shutdown high causes the outputs to mute and the amplifier to enter a low-current state, i dd ~ 0.6 a. shutdown should never be left unconnected because amplifier operation would be unpredictable. low-esr capacitors are recommended throughout this applications section. a real capacitor can be modeled simply as a resistor in series with an ideal capacitor. the voltage drop across this resistor minimizes the beneficial effects of the capacitor in the circuit. the lower the equivalent value of this resistance, the more the real capacitor behaves like an ideal capacitor. a prime consideration when designing an audio amplifier circuit is internal power dissipation in the device. the curve in figure 40 provides an easy way to determine what output power can be expected out of the TPA4860 for a given system ambient temperature in designs using 5-v supplies. this curve assumes no forced airflow or additional heat sinking. figure 40. free-air temperature versus maximum continuous output power the TPA4860 was designed for operation over a supply range of 2.7 v to 5.5 v. this data sheet provides full specifications for 5-v and 3.3-v operation, as these are considered to be the two most common standard voltages. there are no special considerations for 3.3-v versus 5-v operation as far as supply bypassing, gain setting, or stability. supply current is slightly reduced from 3.5 ma (typical) to 2.5 ma (typical). the most important consideration is that of output power. each amplifier in TPA4860 can produce a maximum voltage swing of v dd ? 1 v. this means, for 3.3-v operation, clipping starts to occur when v o(pp) = 2.3 v as opposed to when v o(pp) = 4 v while operating at 5 v. the reduced voltage swing subsequently reduces maximum output power into an 8-w load to less than 0.33 w before distortion begins to become significant. operation at 3.3-v supplies, as can be shown from the efficiency formula in equation 4 , consumes approximately two-thirds the supply power for a given output-power level than operation from 5-v supplies. when the application demands less than 500 mw, 3.3-v operation should be strongly considered, especially in battery-powered applications. 21 www .ti.com 160 4020 0 0 0.25 1.50 0.5 0.75 1 r l = 16 w free-air t emperature maximum output power w 1.25 r l = 8 w r l = 4 w c t a 8060 120100 140 v d d = 5 v
packaging information orderable device status (1) package type package drawing pins package qty eco plan (2) lead/ball finish msl peak temp (3) TPA4860d active soic d 16 40 green (rohs & no sb/br) cu nipdau level-1-260c-unlim TPA4860dr active soic d 16 2500 green (rohs & no sb/br) cu nipdau level-1-260c-unlim TPA4860drg4 active soic d 16 2500 green (rohs & no sb/br) cu nipdau level-1-260c-unlim (1) the marketing status values are defined as follows: active: product device recommended for new designs. lifebuy: ti has announced that the device will be discontinued, and a lifetime-buy period is in effect. nrnd: not recommended for new designs. device is in production to support existing customers, but ti does not recommend using this part in a new design. preview: device has been announced but is not in production. samples may or may not be available. obsolete: ti has discontinued the production of the device. (2) eco plan - the planned eco-friendly classification: pb-free (rohs), pb-free (rohs exempt), or green (rohs & no sb/br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. tbd: the pb-free/green conversion plan has not been defined. pb-free (rohs): ti's terms "lead-free" or "pb-free" mean semiconductor products that are compatible with the current rohs requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. where designed to be soldered at high temperatures, ti pb-free products are suitable for use in specified lead-free processes. pb-free (rohs exempt): this component has a rohs exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. the component is otherwise considered pb-free (rohs compatible) as defined above. green (rohs & no sb/br): ti defines "green" to mean pb-free (rohs compatible), and free of bromine (br) and antimony (sb) based flame retardants (br or sb do not exceed 0.1% by weight in homogeneous material) (3) msl, peak temp. -- the moisture sensitivity level rating according to the jedec industry standard classifications, and peak solder temperature. important information and disclaimer: the information provided on this page represents ti's knowledge and belief as of the date that it is provided. ti bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. efforts are underway to better integrate information from third parties. ti has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. ti and ti suppliers consider certain information to be proprietary, and thus cas numbers and other limited information may not be available for release. in no event shall ti's liability arising out of such information exceed the total purchase price of the ti part(s) at issue in this document sold by ti to customer on an annual basis. package option addendum www.ti.com 18-apr-2006 addendum-page 1

important notice texas instruments incorporated and its subsidiaries (ti) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. all products are sold subject to ti?s terms and conditions of sale supplied at the time of order acknowledgment. ti warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with ti?s standard warranty. testing and other quality control techniques are used to the extent ti deems necessary to support this warranty. except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. ti assumes no liability for applications assistance or customer product design. customers are responsible for their products and applications using ti components. to minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. ti does not warrant or represent that any license, either express or implied, is granted under any ti patent right, copyright, mask work right, or other ti intellectual property right relating to any combination, machine, or process in which ti products or services are used. information published by ti regarding third-party products or services does not constitute a license from ti to use such products or services or a warranty or endorsement thereof. use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from ti under the patents or other intellectual property of ti. reproduction of information in ti data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. reproduction of this information with alteration is an unfair and deceptive business practice. ti is not responsible or liable for such altered documentation. resale of ti products or services with statements different from or beyond the parameters stated by ti for that product or service voids all express and any implied warranties for the associated ti product or service and is an unfair and deceptive business practice. ti is not responsible or liable for any such statements. following are urls where you can obtain information on other texas instruments products and application solutions: products applications amplifiers amplifier.ti.com audio www.ti.com/audio data converters dataconverter.ti.com automotive www.ti.com/automotive dsp dsp.ti.com broadband www.ti.com/broadband interface interface.ti.com digital control www.ti.com/digitalcontrol logic logic.ti.com military www.ti.com/military power mgmt power.ti.com optical networking www.ti.com/opticalnetwork microcontrollers microcontroller.ti.com security www.ti.com/security low power wireless www.ti.com/lpw telephony www.ti.com/telephony video & imaging www.ti.com/video wireless www.ti.com/wireless mailing address: texas instruments post office box 655303 dallas, texas 75265 copyright ? 2006, texas instruments incorporated

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