3718 low-voltage audio power amplifier discontinued product for reference only providing a low-cost, compact alternative to discrete transistor amplifiers, the uln3718m integrated circuit is ideal for application as a headphone driver in portable radios, tape players, and other battery-operated equipment. the low-power audio amplifiers wide frequency response and low noise ensure premium performance. the amplifier will operate (at reduced volume) with supply voltages as low as 1.8 v without a significant increase in distortion. this feature allows operation with a 3 v battery supply and minimizes concern about weak batteries. the class-ab audio amplifier has low quiescent current drain for maximum battery life. this device is rated for opera- tion with supply voltages up to 9 v. the uln3718m audio amplifier is supplied in an 8-pin mini-dip plastic package. a copper alloy lead frame gives the amplifier en- hanced power dissipation ratings. features n wide operating voltage range 1.8 - 9.0 v n low quiescent current n ac short-circuit protection n low external parts count n low distortion n 40 db voltage gain n low noise 3718 low-voltage audio power amplifier always order by complete part number: uln3718m . data sheet 27117.25 absolute maximum ratings supply voltage, v cc . . . . . . . . . . . . . . 10 v package power dissipation, p d . . . . . . . . . . . . . . . . . . . . see graph operating temperature range, t a . . . . . . . . . . . . . . . . -20 c to +85 c storage temperature range, t s . . . . . . . . . . . . . . . -65 c to +150 c
3718 low-voltage audio power amplifier 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 limits characteristic symbol test conditions min. typ. max. units supply voltage range v cc 1.8 3.0 9.0 v quiescent supply current i cc v cc = 3.0 v 6.0 10 ma v cc = 6.0 v 9.0 15 ma v cc = 9.0 v 12 20 ma voltage gain a v 36 40 44 db audio power output p out r l = 8 w , v cc = 3.0 v, thd = 10% 80 mw r l = 8 w , v cc = 6.0 v, thd = 10% 250 430 mw r l = 32 w , v cc = 3.0 v, thd = 10% 15 25 mw r l = 32 w , v cc = 6.0 v, thd = 10% 125 mw distortion thd p out = 10 mw 0.3 1.0 % p out = 1.0 mw, v cc = 1.8 v 1.5 3.0 % output noise v out input shorted, bw = 80 khz 200 500 m v input resistance r in pin 8 250 k w power supply rejection psrr c d (pin 1) = 500 m f, f = 120 hz 28 db electrical characteristics at t a = +25 c, v cc = 3 v, r l = 32 w , f in = 400 hz (unless otherwise noted). test circuit and typical application 50 75 100 125 150 0.5 0 allowable package power dissipation in watts temperature in c 2.0 1.5 1.0 25 dwg. gp-009-1b r = 55 c/w q jc free air, r = 80 c/w q ja w copyright ? 1985, 1995, allegro microsystems, inc.
3718 low-voltage audio power amplifier typical characteristics 1000 r = 32 w l r = 16 w l r = 8 w l 246810 200 0 800 600 400 0 dwg. gs-010 supply voltage, v in volts cc thd = 10% f = 400 hz in output power, p in mw out power supply rejection ratio as a function of frequency output power as a function of supply voltage quiescent supply current as a function of supply voltage 30 100 300 1k 30 40 0 10 20 10 dwg. gs-012 frequency in hertz power supply rejection ratio in db c = 100 m f d c = 500 m f d 246810 5 0 20 15 10 0 dwg. gs-011 supply voltage, v in volts cc quiescent supply current, i in ma cc
3718 low-voltage audio power amplifier 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 applications information selection of power-supply voltage and speaker impedance allows a designer to choose audio power levels within the allowable package power dissipation rating for any maximum operating temperature. no unique precautions are necessary when designing with this device. it is stable and ac short-circuit immune. external component selection for this low-power amplifier involves only two capacitors one for output coupling and one for feedback and ripple decoupling. the coupling capacitor value should be selected to provide the desired low-frequency cutoff with the chosen load impedance. the decoupling capacitor should be chosen for both low-frequency audio rolloff and supply-ripple rejection. ripple rejection is not practical to calculate due to the large number of mechanisms involved. a 500 m f capacitor achieves typi- cally 25 db rejection at 120 hz. the high gain and the high input impedance of the power amplifier recommend use of this device in many diverse applications. however, the input stage does have other characteristics that should be taken into account for best results. the input is referenced to ground for internal biasing and must be provided with a dc path to ground. a current of typically 1 m a flows from the input through the volume control. this produces an ir drop that is multiplied by the closed loop dc gain of the amplifier and appears as an error in output centering. this recommends a value of 200 k w or less for the volume control; values of less than 100 k w are preferred. the selection of amplifier load impedance involves more than just consideration of the desired power output. a low load impedance will produce the highest power output for any given supply voltage. higher impedances will furnish significant reduction in harmonic distortion and improvement in overall repeatability in power output capacity. special steps toward minimizing tendencies towards instabilities of all types were taken in the design of this device. however, as with all high-gain circuits, care should be given to printed wiring board layout to avoid undesirable effects. inputs and outputs should be well separated and should avoid common-mode impedances wherever possible. for best performance, connect low-level input-signal ground terminals and the decoupling capacitor ground terminal together at pin 3 (signal ground); connect the high-level speaker ground terminal and the power supply ground terminal together at pin 2 (power ground). the signal ground and the power ground should be interconnected at only one point.
3718 low-voltage audio power amplifier dimensions in inches dimensions in millimeters (based on 1 = 25.4 mm) 0.355 0.204 7.62 bsc dwg. ma-001-8a mm 10.92 max 4 10.16 9.02 2.54 bsc 0.13 min 3.81 2.93 5 8 1 7.11 6.10 5.33 max 1.77 1.15 0.39 min 0.558 0.356 0.014 0.008 0.300 bsc dwg. ma-001-8a in 0.430 max 4 0.100 bsc 5 8 1 0.022 0.014 0.400 0.355 0.005 min 0.150 0.115 0.280 0.240 0.210 max 0.070 0.045 0.015 min notes: 1. lead thickness is measured at seating plane or below. 2. lead spacing tolerance is non-cumulative. 3. exact body and lead configuration at vendors option within limits shown.
3718 low-voltage audio power amplifier 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 allegro microsystems, inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the design of its products. components made under military approvals will be in accordance with the approval requirements. the information included herein is believed to be accurate and reliable. however, allegro microsystems, inc. assumes no responsibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.
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