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ht318 d ? - 1 - 03 / 201 9 C v0.6 am ?? 75w pbtl / 4 0w btl d ? ? ? ? btl ?? 2 4 0 w (v dd =24v, r l =8?, thd+n= 1 0 %) 2 3 0 w (v dd =1 6 v, r l =4?, thd+n= 1 0%) ? pbtl ?? 75 w (v dd =24v, r l =4?, thd+n= 1 0%) ? ??? 4.5v - 26v ?? ? 90% ; bd 1 spw ???? ? ? p clp ? agc ? ????? am ? ; ? ??? ? ? / ?? / ? ? ? ? / / / ?? ? ?? ? ?? qfn36l ? ? ? ? ? ? ? ?? ? ? lcd / ? ht 318 ? d ??? 24v ( btl ) ?? ?? 2 * 4 0w/8 ? pbtl ???? 75w/4 ht 318 ????? ? ? p clp ????? ?????? agc ?????? ?? ht 318 ?? tfb ?? ?????????? ???1??? ???? ht 318 ???? am ??????? ? ht 318 ??? ? ? ? ? ? ???? ?? ? ? ? ? ?? ?? ? / ht 318sqer qfn36 l ht318 sq uvw x yz 1 - 40 85 t ape and reel 2500 p cs 1 uvw x yz ?? tel:0755-82863877 13242913995 e-mail:panxia168@126.com http://www.szczkjgs.com
ht318 d ? - 2 - 3 / 2019 C v0.6 ? ? ep gain / slv 1 ina + ina - sft _ clip gvdd lim ggnd inb - inb + 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 36 35 34 33 bsb + bsb - bsa - bsa + outb + outb - outa + outa - pgnd am 0 am 1 am 2 mute sync avdd pvddb pvddb pvddb pvdda pvdda pvdda avdd ggnd nc mode \ sd \ fault ? pin no. name i/o 2 d escription 1 ina+ i a ?? 2 ina - i a ?? 3 sft_clip i ?? 4 gvdd o ? 1uf ? 5 gain /slv i ? ??? . 6 lim i ?? agc 7 ggnd g ? 8 inb - i b ?? 9 inb+ i b ?? 10 am0 i d ?? 11 am1 i d ?? 1 2 a m2 i d ?? 13 mute i ??? 1 4 sy nc i o ???????? gain /slv 1 5 avdd p ?? 1 6 ,1 7 ,1 8 pvdd b p b ??? 1 9 bsb+ bst boot strap ? 220nf ? outb+ 2 i: ; o: ; g: ; p: ? ; bst: ? ep gain / slv 1 ina + ina - sft _ clip gvdd lim ggnd inb - inb + 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 36 35 34 33 bsb + bsb - bsa - bsa + outb + outb - outa + outa - pgnd am 0 am 1 am 2 mute sync avdd pvddb pvddb pvddb pvdda pvdda pvdda avdd ggnd nc mode \ sd \ fault
ht318 d ? - 3 - 3 / 2019 C v0.6 2 0 outb+ o b ? 2 1 outb - o b ? 2 2 bsb - bst boot strap ? 220nf ? outb - 2 3 pgnd g ? 2 4 bsa - bst boot strap ? 220nf ? outa - 2 5 outa - o a ? 2 6 outa+ o a ? 2 7 bsa+ bst boot strap ? 220nf ? outa+ 2 8 ,2 9 , 30 pvdd a p a ??? 3 1 avdd p ?? 32 ggnd g ? 33 nc - ?? 3 4 m ode i d ??????? bd ???? 1 spw ?? 3 5 \ sd i ????????????? 3 6 \ fault o ?????? e p p owerpad g ?????? ? ? mode lim ht 318 am [ 2 : 0 ] \ sd fault gain _ slv sft _ clip outa + outa - speaker a filter filter bstrpa + bstrpa - outb + outb - speaker b filter filter bstrpb + bstrpb - audio source and control mute pvdd avdd power supply 4 . 5 - 26 v gain select and master / slave setting power limit mode select limiter level select right left ina + ina - inb - inb + pbtl detect modulation mode select sync synchronization or not modulation frequency select mode lim ht 318 am [ 2 : 0 ] \ sd fault gain _ slv sft _ clip outa + outa - speaker a filter filter bstrpa + bstrpa - outb + outb - speaker b filter filter bstrpb + bstrpb - audio source and control mute pvdd avdd power supply 4 . 5 - 26 v gain select and master / slave setting power limit mode select limiter level select right left ina + ina - inb - inb + pbtl detect modulation mode select sync synchronization or not modulation frequency select
ht318 s tereo class d audio amplifier - 4 - 3 / 2019 C v0.6 75w pbtl / 4 0 w btl class d stereo amplifier with am avoidance ? feature ? o utput power ( btl ) 2 4 0 w (v dd =24v, r l =8?, thd+n=1%) 2 3 0 w (v dd =1 6 v, r l =4?, thd+n=10%) ? o utput power ( pbtl ) 75w (v dd =24v, r l =4?, thd+n=10%) ? s ingle wide voltage supply: 4.5v - 26v ? efficiency > 90% ; bd and 1spw modulation ? optional power limit functions: agc and power clipper (pclp) ? multiple switching frequency with am avoidance ? master and slave synchronization ? diff erential / single - ended analog input, btl or pbtl output ? i ntegrated self - protection circuits including thermal foldback (tfb) and overvoltage, undervoltage, overtemperature, dc - detect, overcurrent with error reporting ? l f and hf package of qfn36l ? application s ? s ound bars ? w ireless speakers ? c onsumer audio applications ? tvs/monitors ? general description h t 318 is a stereo efficient, class - d audio amplifier f or driving speakers up to 75w/4 ? in mono pbtl. it can also deliver 2 30w/8 power in stereo btl. h t 318 features 2 different power limit functions. one is power clipper (pclp), which can clip the output voltage under a preset level; another one is agc which can limit the output music under a preset level without clipping. thermal foldback (tfb) function is designed to protect ht 318 from excessive die temperature in case of the d evice being operated beyond the recommended temperature or power, or with a weak thermal system, without shutting the device down. multiple switching frequency is selectable for ht 318 to avoid am interferences. ht318 also can be worked in either master or slave, making it possible to synchronize multiple devices . h t 318 is fully protected against faults with overvoltage, undervoltage, overtemperature, dc - detect, and overcurrent protection. faults can be reported to the processor to prevent devices from being damaged ? ordering information part number package type marking o perating temperature range m oq/shipping package ht 318sqer qfn36 l ht318 sq uvw x yz 1 - 40 85 t ape and reel 2500 p cs 1 uvw x yz is production tracking code
ht318 class d stereo audio amplifier - 5 - 03 / 201 9 C v 0.6 ? terminal configuration ep gain / slv 1 ina + ina - sft _ clip gvdd lim ggnd inb - inb + 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 36 35 34 33 bsb + bsb - bsa - bsa + outb + outb - outa + outa - pgnd am 0 am 1 am 2 mute sync avdd pvddb pvddb pvddb pvdda pvdda pvdda avdd ggnd nc mode \ sd \ fault t op view pin no. name i/o 1 d escription 1 ina+ i positive input terminal for a channel 2 ina - i negative input terminal for a channel 3 sft_clip i s ets the maximum output voltage before clipping (limiter level) 4 gvdd o voltage regulator derived from pvdd supply , connect 1uf to gnd (note: this pin is provided as a connection point for filtering capacitors for this supply and must not be used to power any external circuitry) 5 gain /slv i selects gain and selects between m aster and slave mode depending on pin voltage divider. 6 lim i s elects the mode of power clipper or agc 7 ggnd g ground for gate drive circuitry (this terminal should be connected to the system ground) 8 inb - i negative input terminal for b channel 9 inb+ i positive input terminal for b channel 10 am0 i am avoidance frequency selection 11 am1 i am avoidance frequency selection 1 2 a m2 i am avoidance frequency selection 13 mute i m ute control terminal, the amplifier is muted when it is pulled high 1 4 sy nc i o clock input/output for synchronizing multiple class - d devices. direction determined by gain/slv terminal. 1 5 avdd p a nalog power supply 1 i: input; o: output; g: ground; p: power; bst: boot strap ep gain / slv 1 ina + ina - sft _ clip gvdd lim ggnd inb - inb + 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 36 35 34 33 bsb + bsb - bsa - bsa + outb + outb - outa + outa - pgnd am 0 am 1 am 2 mute sync avdd pvddb pvddb pvddb pvdda pvdda pvdda avdd ggnd nc mode \ sd \ fault
ht318 class d stereo audio amplifier - 6 - 03 / 201 9 C v 0.6 1 6 ,1 7 ,1 8 pvdd b p power supply for amplifier drivers of b channel 1 9 bsb+ bst connection point for the outb+ bootstrap capacitor, which is used to create a power supply for the high - side gate drive for outb+ 2 0 outb+ o positive pin for differential speaker amplifier output b 2 1 outb - o negative pin for differential speaker amplifier output b 2 2 bsb - bst connection point for the outb - bootstrap capacitor, which is used to create a power supply for the high - side gate drive for outb - 2 3 pgnd g p ower ground, make sure connect it to the system ground 2 4 bsa - bst connection point for the outa - bootstrap capacitor, which is used to create a power supply for the high - side gate drive for outa - 2 5 outa - o negative pin for differential speaker amplifier output a 2 6 outa+ o positive pin for differential speaker amplifier output a 2 7 bsa+ bst connection point for the outa+ bootstrap capacitor, which is used to create a power supply for the high - side gate drive for outa 2 8 ,2 9 , 30 pvdd a p power supply for amplifier driv ers of a channel 3 1 avdd p a nalog power supply 32 ggnd g ground for gate drive circuitry (this terminal should be connected to the system ground) 33 nc - not connected inside the device (all "no connect" pins should be connected to ground for best thermal performance, however they can be used as routing channels if required.) 3 4 m ode i mode selection logic input (low = bd mode, high = 1 spw mode). ttl logic levels with compliance to avcc 3 5 \ sd i place the speaker amplifier in shutdown mode while pulled down. 3 6 \ fault o speaker amplifier fault terminal, which is pulled low when an internal fault occurs e p p owerpad g connect to gnd for best system performance . ? typical application mode lim ht 318 am [ 2 : 0 ] \ sd fault gain _ slv sft _ clip outa + outa - speaker a filter filter bstrpa + bstrpa - outb + outb - speaker b filter filter bstrpb + bstrpb - audio source and control mute pvdd avdd power supply 4 . 5 - 26 v gain select and master / slave setting power limit mode select limiter level select right left ina + ina - inb - inb + pbtl detect modulation mode select sync synchronization or not modulation frequency select mode lim ht 318 am [ 2 : 0 ] \ sd fault gain _ slv sft _ clip outa + outa - speaker a filter filter bstrpa + bstrpa - outb + outb - speaker b filter filter bstrpb + bstrpb - audio source and control mute pvdd avdd power supply 4 . 5 - 26 v gain select and master / slave setting power limit mode select limiter level select right left ina + ina - inb - inb + pbtl detect modulation mode select sync synchronization or not modulation frequency select
ht318 class d stereo audio amplifier - 7 - 03 / 201 9 C v 0.6 ? specifications 1 ? a bsolute maximum ratings 2 para meter s ymbol m in m ax unit s upply voltage range ( pvdd, avdd) v dd - 0.3 30 v i nput voltage range ( in a +, in a - , inb+, inb - ) v i 0. 3 5.8 v i nput voltage range ( sft_clip , gain / slv , lim , sync ) v i 0.3 gvdd v i nput voltage range ( am0 , am1 , am2, mute , \ sd , mode ) v i 0.3 avdd v operating temperature range t a - 4 0 85 operating junction temperature range t j - 4 0 1 50 s torage temperature range t stg - 50 150 ? r ecommended operating conditions para meter s ymbol c ondition m in typ m ax unit s upply voltage range v dd pvdd, avdd 4.5 26 v operating temperature t a - 40 25 85 high - level input voltage v ih am x , mute, \ sd , sync, mode 2 v low - level input voltage v il am x , mute, \ sd , sync, mode 0.8 v l ow - level output voltage v ol \ fault 0 .8 v high - level input current i ih am x , mute, \ sd , mode (v i = 2v, v dd = 18v) 50 ua load impedance ( btl ) r l w ith output filter ( 1 0uh , 680nf ) 3 .2 4 load impedance ( pbtl ) r l w ith output filter ( 1 0uh, 1uf) 1 .6 2 ? dc e lectrical characteristics c onditions: t a = 25 , v dd = 4.5 - 26v , load = 4ohm , unless otherwise specified. para meter s ymbol c ondition m in typ m ax unit cl as s output offset voltage v os v i = 0v, gain = 36db 1.5 m v quiescent supply current i dd v dd = 12v, no load 20 ma v dd = 24v, no load 32 ma quiescent supply current in m ute mode i mute v dd = 12v, with load 13 ma v dd = 24v, with load 13 ma quiescent supply current in sd mode i sd v dd = 12v, with load 50 ua v dd = 24v, with load 50 ua system gain in master mode ( btl or pbtl ) gain rp = open, rd = 5.6k 35 36 37 db r p = 100k, rd = 20k 31 32 33 db r p = 100k, rd = 39k 25 26 27 db r p = 75 k, rd = 47k 19 20 21 db system gain in slave mode ( btl or pbtl ) gain rp = 51k , rd = 51 k 35 36 37 db r p = 47 k, rd = 75 k 31 32 33 db r p = 39 k, rd = 100 k 25 26 27 db r p = 16 k, rd = 100 k 19 20 21 db turn - on time t on pull \ sd high or power on 10 ms turn - off time t off pull \ sd low 2 us gate drive supply gvdd 5.5 v 1 d epending on parts and pcb layout, characteristics may be changed. 2 stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating co nditions is not implied. exposure to absolute C maximum C rated conditions for extended periods may affect device reliability .
ht318 class d stereo audio amplifier - 8 - 03 / 201 9 C v 0.6 ? ac e lectrical characteristics c onditions: t a = 25 , v dd = 4.5 - 26v , load = filter + r l , filter = 10uh + 680nf, r l = 4 + 22uh, f in = 1 khz , gain = 2 6 db, c in = 1uf, 20 - 20khz, power limit off, bd mode, unless otherwise specified. para meter s ymbol c ondition m in typ m ax unit continuous output power p o vdd = 12v, r l = 4 +22uh , btl thd +n = 1% 14 w thd+n = 10% 17 w vdd = 12v, r l = 8 +33uh , btl thd +n = 1% 8 w thd+n = 10% 10 w vdd = 1 6 v, r l = 4 +22uh , btl thd +n = 1% 26 w thd+n = 10% 30 w vdd = 16v, r l = 8 +33uh , btl thd +n = 1% 15 w thd+n = 10% 18 w vdd = 20v, r l = 8 +33uh , btl thd +n = 1% 23 w thd+n = 10% 28 w vdd = 24v, r l = 8 +33uh , btl thd +n = 1% 3 3 w thd+n = 10% 40 w vdd = 16v, r l = 3 +22uh , pbtl thd +n = 1% 36 w thd+n = 10% 45 w vdd = 16 v, r l = 4 +22uh , pbtl thd +n = 1% 28 w thd+n = 10% 35 w vdd = 2 0 v, r l = 4 +22uh , pbtl thd +n = 1% 45 w thd+n = 10% 55 w vdd = 24v, r l = 4 +22uh , pbtl thd +n = 1% 60 w thd+n = 10% 7 5 w total harmonic distortion + noise thd+n po = 1w, v dd = 18v, r l = 8 0.02 % efficiency vdd = 12v, thd+n = 10% r l = 4 , btl 92 % r l = 8 , btl 94 % vdd = 20v, thd+n = 10% r l = 8 , btl 94 % vdd = 16 v, thd+n = 10% r l = 4 , pbtl 95 % cross talk ct vo = 1vrms, gain = 20db - 95 db output integrated noise v n a - weighted, gain = 20 db 100 uv signal - to - noise ratio snr a - weighted, gain = 20 db , po = 1w 85 db power supply rejection ratio psrr 200mvpp 1khz, input grounded - 75 db oscillator frequency f osc am2=0, am1 = 0, am0 = 0 400 khz am2=0, am1 = 0 , am0 = 1 500 khz am2=0, am1 = 1 , am0 = 0 600 khz am2=0, am1 = 1, am0 = 1 reserved am2=1, am1 = 0, am0 = 0 am2=1, am1 = 0, am0 = 1 am2=1, am1 = 1, am0 = 0 am2=1, am1 = 1, am0 = 1 over temperature protection trigger point otp 160 thermal holdback trigger point tfb 150 over current trip point ocp 7.5 a
ht318 class d stereo audio amplifier - 9 - 03 / 201 9 C v 0.6 ? typical operating characteristics t a = 25c, btl mode , am1 = am2 = l, mode = l, f in = 1 khz, unless otherwise noted. output filter is used as 10 h and 0.68 f, unless otherwise noted. po vs thd+n (vdd = 12v, load = 4ohm)
ht318 class d stereo audio amplifier - 10 - 03 / 201 9 C v 0.6 p o vs thd+n (vdd = 24v, load = 8ohm) f in vs thd+n (vdd = 24v, load = 8ohm, po = 1w)
ht318 class d stereo audio amplifier - 11 - 03 / 201 9 C v 0.6 f in vs thd+n (vdd = 12v, load = 4ohm, po = 1w)
ht318 class d stereo audio amplifier - 12 - 03 / 201 9 C v 0.6 ? application information 1. p ower supply the power supply for the ht 318 only require one voltage from 4.5v to 26v, which supplies the analog circuitry (avdd) and the power stage (pvdd) the av dd supply feeds internal ldo including gvdd . this ldo output is connected to external pins for filtering purposes, but should not be connected to external circuits. the filtering c apacitor for gvdd is recommended to be 1uf. a filtering capacitor of 1uf for avdd is also needed. t he pvdd (pin1 6 , 1 7 , 1 8 ) feeds the power stage of b channel and the pvdd (pin2 8 , 2 9 , 30 ) feeds the power stage of a channel. filtering capacitors of 100nf//1 u f//220uf for pvdd of each channel should be place d close to the pvdd pin. 2. class d modulation (mode pin) h t318 can run in either bd modulation or 1spw modulation, which is determined by mode pin. 2 .1 bd modulation b d modulation is selected once mode pin is pulled low. this is a modulation scheme that allows operation without the classic lc reconstruction filter when the amp is drivin g an inductive load with short speaker wires. each output is switching from 0 volts to the supply voltage. the out + and out - are in phase with each other with no input so that there is little or no current in the speaker. the duty cycle of out + is greater than 50% and out - is less than 50% for positive output voltages. the duty cycle of out + is less than 50% and out - is greater than 50% for negative output voltages. the voltage across the load sits at 0v throughout most of the switching period, reducing the switching current, which reduces any i2r losses in the load. 2 .2 1spw modulation 1 spw modulation is selected once mode pin is pulled high. the 1spw mode alters the normal modulation scheme in order to achieve higher efficiency with a slight pe nalty in thd degradation and more attention required in the output filter selection. in 1spw mode the outputs operate at ~15% modulation during idle conditions. when an audio signal is applied one output will decrease and one will increase. the decreasing output signal will quickly rail to gnd at which point all the audio modulation takes place through the rising output. the result is that only one output is switching during a majority of the audio cycle. efficiency is improved in this mode due to the reduc tion of switching losses. the thd penalty in 1spw mode is minimized by the high - performance feedback loop. the resulting audio signal at each half output has a discontinuity each time the output rails to gnd. this can cause ringing in the audio reconstruct ion filter unless care is taken in the selection of the filter components and type of filter used. 3. power limit function there are two different power limit functions for ht 318 , one is automatic gain control (agc), the other is power clipper (pclp). the function can be selected by setting the lim pin. 3 .1 power limit mode (lim pin) the lim pin configuration is shown as figure 1 and t able. 1 .
ht318 class d stereo audio amplifier - 13 - 03 / 201 9 C v 0.6 lim ht 318 gvdd rp rd figure 1 lim termina l configuration t able. 1 lim terminal settings voltage of lim terminal p ower limit mode attack time t a ( u s /db ) r elease time t r ( m s /db ) gvdd agc fast 80 400 2/3 gvdd agc medium 160 800 1/3 gvdd agc slow 320 1600 gnd p clp / if the agc function is selected, the output music can be limited below the preset limiter level (see pin sft_clip ). if the output audio signal exceeds the limiter level, ht 318 decreases amplifier gain by the rate of attack time by 0.25db per step ( step pace ). ht 318 increases the gain by the rate release time by 0.25db/step ( step pace ) once the output audio is below the limiter level. figure 2 shows this relationship. the agc function dont clip the output wave while limiting the output power. it can remove the output clip ping noise and protect the speakers caused by a reduction of power supply voltage or a sudden large volume of input music . lim ht 318 gvdd rp rd
ht318 class d stereo audio amplifier - 14 - 03 / 201 9 C v 0.6 figure 2 agc function des cription the ht 318 also has a power clipper function (plcp) that can be used to clip the output voltage level below the supply rail. the plcp function can be selected by pulling lim pin down into system ground, shown as t able. 1 lim terminal settings . when plcp function is active, the amplifier operates as if it was powered by a lower supply voltage, and thereby enters into clipping sooner than if the circuit was not active. the result is clipping behavior very similar to that of clipping at the pvdd rail, in contrast to the digital clipper behavior which occurs in the oversampled domain of the digital path. the point at which clipping begins is called the limiter level (see pin sft_clip ) . to move the output stage into clipping, the pclp function limits the duty cycle of the output pwm pulses to a fixed maximum value. after filtering this limit applied to the duty cycle resembles a clipping event at a voltage below that of the pvdd level. figure 3 pclp function des cription 3 . 2 limiter level configuration ( sft_clip pin) the limiter level is controlled by a resistor divider from gvdd (around 5.5v) to ground, which sets the voltage at the sft_clip pin (v sft_clip ) . the limiter level is approximately 4 times the voltage at the sft_clip pin, noted as v sft_clip . l imiter level 4 v sft_clip
ht318 class d stereo audio amplifier - 15 - 03 / 201 9 C v 0.6 the precision of the threshold at which clipping occurs is dep endent upon the voltage level at the sft_clip pin. because of this, increasing the precision of the resistors used to create the voltage divider, or using an external reference will increase the precision of the point at which the device enters into clippi ng. to ensure stability, and soften the edges of the clipping event, a capacitor should be connected from pin sft_clip to ground . sft _ clip ht 318 gvdd rp rd 1 uf figure 4 sft_clip terminal configuration if lim pin is connected to gnd, and sft_clip pin is directly connected to gvdd, neither function of agc nor pclp is selected. 4. am avoidance emi reduction (am0, am1 pin) to reduce interference in the am radio band, the ht 318 has the ability to change the switching frequency via am 1 am0 pins. the recommended frequencies are listed in t able. 2 . t able. 2 switching freque ncy settings s witching frequency (khz) am2 : a m1:am0 400 0 00 ( default) 500 001 600 01 0 reserved 0 11 1 00 1 01 1 10 1 11 5. gain setting and master and slave (gain /slv pin) in order to select the amplifier gain setting, the designer must determine the maximum power target and the speaker impedance. once these parameters have been determined, calculate the required output voltage swing which delivers the maximum output power. choose the lowest analog gain setting that corresponds to produce an output voltage swing greater than the required output swing for maximum power. the analog gain can be set by selecting the voltage divider resistors (r p and r d ) on the gai n pin. m aster or slave mode is also controlled by this pin. n otice that a gain or mode changing by this pin will be not effective when the amplifier is working. sft _ clip ht 318 gvdd rp rd 1 uf
ht318 class d stereo audio amplifier - 16 - 03 / 201 9 C v 0.6 gain / slv ht 318 gvdd rp rd 1 uf figure 5 gain /slv terminal configuration t able. 3 gain /slv terminal settings rp () rd () gain (db) m aster or slave mode nc 5.6k 36 m aster 100k 20k 32 m aster 100k 39k 26 m aster 75k 47k 20 m aster 5 1k 5 1k 3 6 s lave 4 7k 7 5k 3 2 s lave 3 9k 1 00k 2 6 s lave 1 6k 1 00k 2 0 s lave 6. a mplifier input and output 6 .1 amplifier input configuration ht 318 is an amplifier with analog input (single - ended or differential) . for a differential operation, input signals into in+ and in - pins via dc - cut capacitors (c in ). t he high pass cut - off frequency of input signal can be calculated by 1 2 = c in in f rc . for a single - ended operation, input signals to in+ pin via a dc - cut capacitor (c in ). in - pin should be connected to ground via a dc - cut capacito r (with the same value of c in ). in + in - c in 1 uf ht 318 front circuit z out in + in - c in 1 u f ht 318 front circuit z out figure 6 (1) differential input; ( 2 ) single - ended input t he input impedance changes with the gain setting from 9kohm to 60kohm as table 4 . if a flat bass response is required down to 20 hz the recommended cut - off frequency is a tenth of that, 2 hz. table 4 l ists the recommended ac - couplings capacitors for each gain step. if a - 3 db is accepted at 20 hz 10 times lower capacitors can used C for exampl e, a 1 f can be used. gain / slv ht 318 gvdd rp rd 1 uf 1 2 ? c in in f rc in + in - c in 1 uf ht 318 front circuit z out in + in - c in 1 u f ht 318 front circuit z out
ht318 class d stereo audio amplifier - 17 - 03 / 201 9 C v 0.6 t able. 4 r in vs gain vs c in g ain (db) r in ( k ) c in (uf) f c (hz) 36 9 10 1.8 32 15 5.6 1.9 26 30 3.3 1.6 20 60 1.5 1.8 6 .2 a mplifier output configuration the ht 318 has been tested with a simple ferrite bead filter for a variety of applications including long speaker wires up to 20 cm and high power. one important aspect of the ferrite bead selection is the type of material used in the ferrite bead. not all ferrite material is alike, so it is important to select a material that is effective in the 10 to 100 mhz range which is key to the operation of the class - d amplifier. the impedance of the ferrite bead can be used along with a small capacitor with a value in the range of 1000 pf to reduce the frequency spectrum of the signal to an acceptable level. for best performance, the resonant frequency of the ferrite bead/ capacitor filter should be less than 10 mhz. also, the filter capacitor can be increased if nec essary, with some impact on efficiency. figure 7 out put filters with ferrite beads there may be a few circuit instances where it is necessary to add a complete lc reconstruction filter. these circumstances might occur if there ar e nearby circuits which are sensitive to noise. in these cases, a classic second order butterworth filter similar to those shown in the figures below can be used. some systems have little power supply decoupling from the ac line but are also subject to lin e conducted interference (lci) regulations. these include systems powered by "wall warts" and "power bricks." in these cases, lc reconstruction filters can be the lowest cost means to pass lci tests. common mode chokes using low frequency ferrite material can also be effective at preventing line conducted interference. figure 8 out put filters with lc 6 .3 pbtl mode configuration the ht 318 can be configured to drive a single speaker with the two output channels connected in parallel. this mode of operation is called parallel bridge tied load (pbtl) mode. this mode of operation effectively reduces the output impedance of the amplifier in hal f, which in turn reduces the power dissipated in the device due to conduction losses through the output fets. additionally, since the output channels are working in parallel, it also doubles the amount of
ht318 class d stereo audio amplifier - 18 - 03 / 201 9 C v 0.6 current the speaker amplifier can source before hit ting the over - current error threshold. to place the ht 318 into pbtl mode , the pbtl pin should be pulled high (that is, connected to the dvdd supply through a pull - up resistor). if the device is to operate in btl mode instead, the pbtl pin should be pulled low, that is connected to the system supply ground. when operated in pbtl mode, the output pins should be connected as shown in the typical application circuit diagrams. in pbtl mode, the amplifier selects its source signal from the a channel of the stereo signal . 7. s tartup, shutdown and mute operation the ht 318 employs a shutdown mode of operation designed to reduce supply current (i dd ) to the absolute minimum level during periods of nonuse for power conservation. the \ sd input terminal should be held high d uring normal operation when the amplifier is in use. pulling \ sd low will put the outputs to mute and the amplifier to enter a low - current state. it is not recommended to leave \ sd unconnected, because amplifier operation would be unpredictable. for a better power on and power - off pop performance, place the amplifier in the shutdown mode prior to delivering or removing the power supply. t he ht 318 also has a mute function in which the differential output is grounded through resistiv ity. the mute terminal should be held low in normal operation. pulling mute high will put ht 318 into mute mode. the noise of placing the amplifier in and out of mute mode will be lower than shutdown mode. 8. o ther functions and terminals 8 .1 gvdd supply the gvdd supply is used to power the gates of the output full bridge transistors. it can also be used to supply the sft_clip , lim and gain voltage dividers. decouple gvdd with a x5r ceramic 1 f capacitor to gnd. the gvdd supply is not intended to be used for external supply. it is recommended to limit the current consumption by using resistor voltage dividers for gain and sft_clip of 100 k or more. 8 . 2 bsa x bs bx capacitors the full h - bridge output stages use only nmos transistors. therefore, they require bootstrap capacitors for the high side of each output to turn on correctly. a 220nf ceramic capacitor of quality x5r or better, rated for at least 16 v, must be connected from each output to its corresponding bootstrap input. the bootstrap capacitors conne cted between the bsxx pins and corresponding output function as a floating power supply for the high - side n - channel power mosfet gate drive circuitry. during each high - side switching cycle, the bootstrap capacitors hold the gate - to - source voltage high enou gh to keep the high - side mosfets turned on. 9. p rotection functions the ht 318 contains a complete set of protection circuits carefully designed to make system design efficient as well as to protect the device against any kind of permanent failures due to short circuits, overload, over temperature, and under - voltage. 9 . 1 o ver temperature protection (o tp ) t his is the function to establish the over temperature protection mode when detecting excessive high temperature of ht 318 . when the on - die temperature of ht 318 is higher than top, the otp mode is activated, the differential output pin becomes weak low state (a state grounded though resistivity). 9 . 2 foldback (tfb) function the ht 318 thermal foldback, tfb, is designed to protect the ht 318 from excessive die temperature in case of the device being operated beyond the recommended temperature or power limit, or with a weaker thermal system than recommended , without shutting the device down . the tfb works by reducing the on - die power dissipat ion by reducing the ht 318 system gain by the rate of attack time (default value 1200ms/db) by 0.25db per step ( step pace ) if the tfb trig poi nt is exceeded. once the die temperature drops below the tfb trig point, the ht 318 gain is increased by a single or by the rate of release time (default value 2400ms/db ) by 0.25db per step ( step pace ) until the tfb trig point, or a maximum attenuation is reached, and the system gain will be decreased again, or the system gain is at its nominal gain level. the procedure shows as follows.
ht318 class d stereo audio amplifier - 19 - 03 / 201 9 C v 0.6 thermal foldback trip point die temperature gain attack tim e release time input singal output singal figure 9 tfb operation 9 .3 dc detect protection ( dcp ) the ht 318 has circuitry which will protect the speakers from dc current which might occur due to an internal amplifier error. a dce event occurs when the output differential duty - cycle of either channel exceeds 60% for more than 420 msec at the same polarity. the table below shows some examples of the typical dce protection threshold for several values of the supply voltage. this feature protects the speaker from large dc currents or ac currents less than 2 hz. the minimum output offset voltages required to trigger the dc detect are listed in t able. 2 . the outputs must remain at or above the voltage listed in the table for mo re than 420 msec to trigger the dc detect . t able. 5 dc detect threshold pvdd (v) | v os | (v) 4 .5 0 .96 6 1 .3 1 2 2 .6 1 8 3 .9 9 .4 short - circuit protection ( ocp ) the ht 318 has protection from over current conditions caused by a short circuit on the output stage. the amplifier outputs are switched to a high impedance state when the short circuit protection latch is engaged. 9 .5 u nder - voltage protection uvp t his is the func tion to establ ish the under - votage protection mode when power supply becomes lower than the detection voltage v uvll , and the protection mode is canceled when the power supply becomes higher than the threshold voltage v uvlh . in the under - voltage protection mode, the differentrial output pin becomes weak low state (a stage grounded through resistivity). ht 318 will start up within start - up time when the under - voltage protection mode is cancelled. thermal foldback trip point die temperature gain attack tim e release time input singal output singal
ht318 class d stereo audio amplifier - 20 - 03 / 201 9 C v 0.6 10. t ypical applications
ht318 class d stereo audio amplifier - 21 - 03 / 201 9 C v 0.6 11. pcb l a yout
ht318 class d stereo audio amplifier - 22 - 03 / 201 9 C v 0.6 ? package outline qfn 36l 6*6 with exposed thermal pad

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