NJU8753 -1- ver.2003-09-26 analog signal input class d amplifier with dc-dc converter for piezo speaker general description the NJU8753 is an analog signal input class d power amplifier with dc-dc converter for piezo speaker. input part operates on 2.85v(typ) and a built-in dc-dc converter generates variable output voltage(up to 12v) with input voltage(2.6 to 4.2v). therefore, it drives piezo speaker with louder sound and high efficiency. the NJU8753 incorporates btl amplifier, which eliminate ac coupling capacitors, capable of driving monaural piezo speaker with simple external lc low-pass filters. class d operation achieves lower power operation for piezo speaker, thus the NJU8753 is suited for battery- powered applications. features piezo speaker driving output voltage: 8vrms(typ.) @v ddo =10.0v 1-channel analog signal input, 1-channel btl output standby(hi-z), built-in dc-dc converter built-in low voltage detector built-in short protector operating voltage :2.6~3.6v(v dd , v reg ) :2.6~4.2v(v bat ) cmos technology package outline :qfn28 pin configuration package outline NJU8753kn1 preliminary test1 test3 v reg fb v ss v ss1 v ss1 l x l x v out v r en2 nc v ddo v dd v ss iin com en1 test2 v ddo v ddo out p v ss nc v ss out n v ddo 28 1 qfn28
NJU8753 - 2 - ver.2003-09-26 block diagram pulse width modulator short protector v dd control logic low voltage detecto r soft start v ss + - + - in com en1 v ddo out p v ss v ddo out n v ss switching regulator en2 fb vr l x v out v reg v ss1 test1 test2 test3
nju3555 nju3555 NJU8753 -3- ver.2003-09-26 pin description no. symbol i/o function 1 test1 i maker test 1 this pin must be connected to gnd. 2 test3 i maker test 3 this pin must be connected to gnd. 3 v reg ? switching regulator power supply : v reg =2.85v 4 fb i switching regulator feedback resistor 5 v ss ? power gnd : v ss =0v 6,7 v ss1 ? switching regulator power gnd : v ss1 =0v 8,9 l x i switching regulator voltage input 10 v out ? switching regulator power supply : v out =10.0v 11 vr o switching regulator output voltage 12 en2 i switching regulator standby control high : step-up on low : standby on this pin must be connected to v reg when step-up on. 13 nc ? non connection 14, 15 v ddo ? output power supply 16 out n o negative output 17 v ss ? power gnd : v ss =0v 18 nc ? non connection 19 v ss ? power gnd : v ss =0v 20 out p o positive output 21, 22 v ddo ? output power supply 23 test2 i maker test 2 this pin must be connected to gnd. 24 en1 i power amplifier standby control high : standby off low : standby on this pin must be connected to v dd when standby off. 25 com ? analog common 26 in i audio signal input 27 v ss i power gnd : v ss =0v 28 v dd ? power supply : v dd =2.85v *pin no.5(v ss ), 6(v ss1 ), 7(v ss1 ), 17(v ss ), 19(v ss ), 27(v ss ) should be connected at the nearest point to the ic. *pin no.14(v ddo ) , 15(v ddo ), 21(v ddo ), 22(v ddo ) should be connected at the nearest point to the ic. *pin no.3(v reg ) and 28(v dd ) must be connected to v dd , when these pins are not used.
NJU8753 - 4 - ver.2003-09-26 functional description (1) signal output the out p and out n generate pwm output signals, which will be converted to analog signal via external 2nd-order or higher lc filter. a switching regulator with a high response against a voltage fluctuation is the best selection for the vddo, which are the power supply for output drivers. to obtain better thd performance, the stabilization of the power is required. (2) en1 by setting the en1 pin to ?l?, the standby mode is enabled. in the standby mode, the entire functions of the NJU8753 enter a low-power state, and the output pins (out p and out n ) are high impedance. (3) low voltage detector when the power supply voltage drops down to below v dd (min), the internal oscillation is halted for prevention to generate unwanted frequency, and the output pins (out p , out n ) become in high impedance. (4) step-up switching regulator the switching regulator is used as power supply(v ddo ) for power amplifier of class-d. the pfm controlled switching regulator works with external components, which are coil, capacitor, schottky-diode and resistor for step-up voltage. by setting the en2 pin to ?h?, the step-up operation is enabled, and in case of ?l?, standby mode is enabled. step-up voltage is set by internal reference voltage(v reg / 2) and external resistors. the step-up voltage can be calculated by the following methods: the step-up voltage is determined by internal reference voltage(v ref ), r 1 and r 2 . (see figure.2) ex. v dd =2.85v, internal reference voltage(v ref ) = v reg / 2=1.425[v], r 1 =2m ? , r 2 =330k ? ? step-up voltage[v] = v ref ((r 1 +r 2 )/r 2 ) = 1.425((2m + 330k)/330k) = 10.06[v] ? note 1) apply v reg first, next v bat . otherwise, the voltage stress may cause a permanent damage to the ic. (5) short circuit protection the short protector, which protects the NJU8753 against high short-circuit current, turns off the output driver. after about 5 seconds from the protection, the NJU8753 returns to normal operation. the short protector functions at the following accidents. -short between out p and out n -short between out p and v ss -short between out n and v ss note 1) the detectable current and the period for the protection depend on the power supply voltage and ambient temperature. note 2) the short protector is not effective for a long term short-circuit current but for an instantaneous accident. continuous high-current may cause permanent damage to the NJU8753 .
nju3555 nju3555 NJU8753 -5- ver.2003-09-26 absolute maximum ratings (ta=25 c) parameter symbol rating unit supply voltage v dd v reg v ddo -0.3 ~ +4.0 -0.3 ~ +4.0 -0.3 ~ +15.0 v v v l x input voltage v lx -0.3 ~ +15.0 v fb input voltage v fb -0.3 ~ +4.0 v input voltage vin -0.3 ~ v dd +0.3 v operating temperature topr -40 ~ +85 c storage temperature tstg -40 ~ +125 c power dissipation p d 640* mw * : mounted on a glass epoxy pcb(50mm x 50mm x 1.6mm). note 1) all voltage are relative to ?v ss = 0v? reference. note 2) the lsi must be used inside of the ?absolute maximum ratings?. otherwise, a stress may cause permanent damage to the lsi. note 3) de-coupling capacitors for v dd (pin 28)-v ss (pin 27), v reg (pin 3)-v ss (pin 5) and l x (pin 8,9)-vss(pin 17,18,19) should be connected for stable operation. electrical characteristic (ta=25 c, v dd =v reg =2.85v, v bat =3.7v, v ddo =10v, v ss =0v, v ss1 =0v, test1=test2=test3=0v, en1=en2=2.85v, input signal=1khz, input signal level=150mvrms, frequency band=20hz~20khz, load impedance=2.0 f 2nd-order 11.5khz lc filter(q=0.72)) parameter symbol conditions min typ max unit note v dd supply voltage v dd 2.6 2.85 3.6 v v reg supply voltage v reg 2.6 2.85 3.6 v v bat input voltage v bat 2.6 3.7 4.2 v v ddo supply voltage v ddo 8.0 10.0 12.0 v input impedance z in in pin - 20 - k ? voltage gain a v - 31 - db output thd thd input signal level =200mvrms - 0.05 0.08 % 4 maximum output vo output thd=10% - 8.0 - vrms s/n sn a weight - 80 - db 4 operating current(standby) i st en1=en2=0v - - 1 a operating current (no signal input) i ss no-load operating no signal input - 10 15 ma v ih en1, en2 pins 0.7v dd - v dd v input voltage v il en1, en2 pins 0 - 0.3v dd v input leakage current i lk en1, en2 pins - - 1.0 a switching regulator oscillating frequency f osc 220 300 380 khz switching regulator maximum load current i out step-up voltage =10.0v v out = 10.0v x 95% 50 - - ma switching regulator load stability ? v out step-up voltage =10.0v i out =10ma~50ma - 100 - mv
NJU8753 - 6 - ver.2003-09-26 note 4) test system of the output thd and s/n the output thd and s/n are tested in the system shown in figure 1, where a 2nd-order lc lpf and another filter incorporated in an audio analyzer are used. 2nd-order lc lpf : refer to ?typical application circuit? filters : 22hz hpf + 20khz lpf(aes17) (with the a-weight filter for s/n and dynamic-range tests) input signal thd measuring apparatus filte r 20khz (aes17) 2nd-order lc lpf NJU8753 test board audio analyzer figure 1. output thd and s/n test system NJU8753
nju3555 nju3555 NJU8753 -7- ver.2003-09-26 typical application circuit note 5) de-coupling capacitors must be connected between each power supply pin and gnd. the capacity value should be adjusted on the application circuit and the operation temperature. it may malfunction if capacity value is small. note 6) the power supply for v ddo require fast driving response performance such as a switching regulator for better thd. thd performance becomes worse by ripple if the capacity of de-coupling capacitors is small. note 7) the above circuit shows only application example and does not guarantee the any electrical characteristics. therefore, please test the circuit carefully to fit your application. the cutoff frequency of the lc filter influences the quality of sound. the q factor of the lc filter must be less than ?1?. otherwise, the operating current increase when the frequency of input signal is closed to the cutoff frequency. note 8) the transition time for en1 and en2 signals must be less than 100 s. otherwise, a malfunction may be occurred. note 9) (1)-(28) indicates pin number. piezo speaker figure 2. application circuit example NJU8753 outp(20) outn(16) v dd (28) v ss (27) 0.1f 10f v dd in(26) com(25) en1(24) 10f 47h 2f 47uh 4.7 ? 4.7 ? in 2.2f 22000pf 2.4k ? v ddo ( 14,15 ) v out ( 10 ) v bat v ss (17,19) fb(4) l x (8,9) test1 ( 1 ) test2 ( 23 ) v ddo ( 21,22 ) schottky diode (if=1a,vf=0.45v) r 1 r 2 2m ? 330k ? 0.1f 10f test3(2) en2(12) v reg (3) v ss (5) 0.1f 10f v dd 0.1f 0.1f 22h(dcr=0.5 ? ) 22f vr(11) v ss1 (6,7) 0.1f [caution] the specifications on this databook are only given for information , without any guarantee as regards either mistakes or omissions. the application circuits in this databook are described only to show representative usages of the product and not intended for the guarantee or permission of any right including the industrial rights.
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