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mp7770 2 x 45w stereo single-ended or 90w mono btl class-d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 1 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. the future of analog ic technology description mp7770 is an analog class-d audio amplifier that can drive either stereo speakers in single- ended configuration or a mono speaker in a bridge-tied-load configuration. it is part of mps?s family of fully-integrated audio amplifiers that dramatically reduce footprint size by integrating: ? 100m ? power mosfets ? startup/shutdown pop elimination ? short-circuit protection circuits the mp7770 is capable of delivering 45w per channel into 4 ? speaker in single-ended output structure, or delivering 90w into 8 ? speaker in bridge-tied-load output structure under 36v vdd. mps?s class d audio amplifiers exhibit the high fidelity of a class a/b amplifier at higher efficiencies. the circuit is based on the mps?s proprietary variable-frequency topology, which delivers excellent linearity, fast response time and operates from a single power supply. features ? 9.5v-to-36v operation from a single supply ? 8.5a peak current output ? output power at 36v and 10%thd: - stereo single-ended: 2 x 45w into 4 ? load, - bridge-tied load: 90w into 8 ? load ? thd+n = 0.03% at 1w, 8 ? ? > 90% efficiency at 10%thd ? low noise ? switching frequency of up to 1mhz ? integrated startup and shutdown pop elimination circuit ? programmable uvp ? thermal and short-circuit protection ? output fault flag and thermal warning ? integrated power fets ? tssop28-ep package with exposed pad on bottom ? tssop28-epr package with exposed pad on top, please contact factory for the availability applications ? dvd receiver ? mini combo system ? home theater systems ? surround sound systems ? audio docking or high-power sound box a ll mps parts are lead-free and adhere to the rohs directive. for mps green status, please visit mps website under quality assurance ?mps? and ?the future of analog ic technology? are registered trademarks o f monolithic power systems, inc.
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 2 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical applications ch1 input ch1 output vdd ref1 in1 timer1 en in2 pgnd1 bst1 sw1 vdd1 pgnd2 sw2 bst2 vdd2 off on ch2 output agnd1 agnd2 timer2 ch2 input ref2 mp7770 uvp otw fault stereo se application circuit input+ vdd ref1 in1 pgnd1 bst1 sw1 vdd1 pgnd2 sw2 bst2 vdd2 output mp7770 timer1 en off on timer2 ref2 in2 input- agnd1 agnd2 uvp otw fault mono btl application circuit
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 3 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. ordering information part number* package top marking mp7770gf tssop28-ep mp7770 **MP7770GFR tssop28-epr mp7770r * for tape & reel, add suffix ?z (e.g. mp7770gf?z); ** contact factory for tssop28f-epr availability package reference tssop28-ep sw1 bst1 sw1 vdd1 pgnd2 vdd1 pgnd1 sw2 sw2 bst2 vdd2 vdd2 n/c ref1 in1 agnd1 timer1 fault otw ref2 agnd2 timer2 uvp in2 n/c en pgnd2 pgnd1 exposed pad on top tssop28-epr absolute maxi mum ratings (1) supply voltage v dd ...................................... 40v bs voltage .............. (v sw - 0.3v) to (v sw + 6.5v) v otw , v fault , v uvp , v timer , v en ....... ?0.3v to +6v v sw ....................................... ?0.3v to (v dd + 1v) v ref , v in ....................................... ?0.3v to +34v agnd to pgnd .......................... ?0.3v to +0.3v continuous power dissipation (t a = 25c) (2) ............................................................ 3.9 w junction temperature ............................... 150 c lead temperature .................................... 260c storage temperature .............. ?65c to +150c recommended operating conditions (3) supply voltage v dd .......................... 9.5v to 36v operating junction temp. (t j ). ........................... ........................................... -40c to +125c thermal resistance (4) ja jc tssop28f-ep ....................... 32 ....... 6 .... c/w tssop28f-epr ...................... .. ........ 6 .... c/w the tssop28f-epr is not intended to be used without a heatsink. therefore, r ja of tssop28f-epr is not specified. notes: 1) exceeding these ratings may damage the device. 2) the maximum allowable power dissipation is a function of the maximum junction temperature t j (max), the junction-to- ambient thermal resistance ja , and the ambient temperature t a . the maximum allowable continuous power dissipation at any ambient temperature is calculated by p d (max) = (t j (max)-t a )/ ja . exceeding the maximum allowable powe r dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. internal thermal shutdown circuitry protects the device from permanent damage. 3) the device is not guaranteed to function outside of its operating conditions. 4) measured on jesd51-7, 4-layer pcb.
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 4 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. electrical characteristics (5, 6) v dd = 24v, v en = 5v, t a = 25c, unless otherwise noted. parameters symbol condition min typ max units standby current v en = 0v,ref=in=float 120 140 a quiescent current i q sw=low 3 4 ma sw on resistance sourcing and sinking 0.1 0.15 ? short-circuit current sourcing and sinking 6.2 8.5 a en enable threshold voltage v en rising 1.4 2.0 v v en falling 0.4 1.0 v en enable input current v en = 5v 5 a external under-voltage detection v uvp 2 2.2 2.4 v external under-voltage detection hysteresis voltage v hys 0.3 v thermal shutdown trip point (7) t j rising 150 c thermal shutdown hysteresis (7) 20 c thermal warning trip point (7) 125 c thermal warning hysteresis (7) 10 c notes: 5) the device is not guaranteed to function outside its operating rating. 6) electrical characteristics are for the ic only wi th no external components except bypass capacitors. 7) not production tested.
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 5 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. operating specifications (8) circuit of figure 6, single-ended output configuration; v dd = 34v, gain=8.2v/v; v en = 5v, t a = 25c, unless otherwise noted. parameters symbol condition min typ max units standby current v en = 0v 120 a quiescent current switching, no load 29 ma power output f = 1khz, thd+n = 10%, 4 ? load 41 w f = 1khz, thd+n = 1%, 4 ? load 32 w f = 1khz, thd+n = 10%, 8 ? load 22 w f = 1khz, thd+n = 1%, 8 ? load 17 w thd + noise p out = 1w, f = 1khz, 4 ? load 0.05 % p out = 1w, f = 1khz, 8 ? load 0.03 % efficiency f = 1khz, p out = 41w, 4 ? load 91 % f = 1khz, p out = 22w, 8 ? load 95 % maximum power bandwi dth 20 khz dynamic range 102 db noise floor a-weighted 90 v power supply rejection v ripple =300mv pp c r =100 f f = 1k hz -60 db f = 217 hz -60 db circuit of figure 7, btl output configuration; v dd = 34v, gain=15v/v; v en = 5v, t a = 25c, unless otherwise noted. parameters symbol condition min typ max units standby current v en = 0v 120 a quiescent current switching, no load 32 ma power output f = 1khz, thd+n = 10%, 6 ? load 108 w f = 1khz, thd+n = 1%,6 ? load 83 w thd+ noise p out = 1w, f = 1khz, 6 ? load 0.06 % p out = 1w, f = 1khz, 8 ? load 0.04 % efficiency f = 1khz, p out = 108w, 6 ? load 91 % f = 1khz, p out = 84w, 8 ? load 95 % maximum power bandwi dth 20 khz dynamic range 105 db noise floor a-weighted 120 v power supply rejection v ripple =300mv pp f = 1k hz -60 db f = 217 hz -60 db note: 8) operating specifications are for the ic in ty pical application circuit (figure 6 and figure 7).
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 6 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. pin functions ep on bottom pin # ep on top pin # name description 1 14 otw over temperature warning. a low out put at otwb indicates that the die temperature rises above 125c. this output is open drain. 2 13 fault fault output. a low output at fault indicates that the ic has detected an over-temperature or over-current condition. this output is open drain. 3, 12 3, 12 n/c not connected. 4 4 timer1 internal timer input for amplifier 1. a capacitor from timer1 to agnd sets the internal timer which is used for start-up pop elimination. 5 5 in1 inverting input for amplifier 1 . 6 6 ref1 internal analog reference ( vdd/2 ) for amplifier 1. for se configuration, connect a bypass capacitor from ref1 to agnd (10 f ). 7 7 agnd1 analog ground for amplifier 1. connect agnd1 to agnd2. connect pgnd to agnd at a single point. 8 8 agnd2 analog ground for amplifier 2. connect agnd2 to agnd1. 9 9 ref2 internal analog reference ( vdd/2 ) for amplifier 2. for btl configuration, connect a bypass capacitor from ref2 to agnd (10 f ). 10 10 in2 inverting input for amplifier 2. 11 11 timer2 internal timer input for amplifier 2. use a capacitor from timer2 to agnd to set the internal timer for start-up pop elimination. 13 2 uvp under-voltage protection reference input. 14 1 en enable input for amplifier 1. drive en 1 high to turn on the amplifier 1, low to turn it off. 15 15 bst2 high-side mosfet bootstrap input for amplifier 2. connect a capacitor from bst2 to sw2 to supplies the gate drive to the internal high-side mosfet. 16, 17 16, 17 pgnd2 power ground for amplifier 2. connect pgnd2 to pgnd1. 18, 19 18, 19 sw2 switched power output for amplifier 2. 20, 21 20, 21 vdd2 power supply input for amplifier 2. bypass vdd2 to pgnd2 with a 1 f x7r capacitor (in addition to the main bulk capacitor), placed close to the vdd2 and pgnd2 pins. 22, 23 22, 23 vdd1 power supply input for amplifier 1. bypass vdd1 to pgnd1 with a 1 f x7r capacitor (in addition to the main bulk capacitor), placed close to the vdd1 and pgnd1 pins. 24, 25 24, 25 sw1 switched power output for amplifier 1. 26,27 26,27 pgnd1 power ground for amplifier 1. connect pgnd1 to pgnd2. connect pgnd to agnd at a single point. 28 28 bst1 high-side mosfet bootstrap input for amplifier 1. a capacitor from bst1 to sw1 supplies the gate drive current to the internal high-side mosfet.
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 7 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical performance curves circuit of figure 6, single-ended output configuration, v dd =34v, v en =5v, a v =8.2v/v, t a = +25 ? c, unless otherwise noted.
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 8 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical performance curves (continued) circuit of figure 6, single-ended output configuration, v dd =34v, v en =5v, a v =8.2v/v, t a = +25 ? c, unless otherwise noted.
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 9 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical performance curves (continued) circuit of figure 6, single-ended output configuration, v dd =34v, v en =5v, a v =8.2v/v, t a = +25 ? c, unless otherwise noted.
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 10 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical performance curves (continued) circuit of figure 7, bridge-tied-load output configuration, v dd =34v, v en =5v, a v =15v/v, t a = +25 ? c, unless otherwise noted.
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 11 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical performance curves (continued) circuit of figure 7, bridge-tied-load output configuration, v dd =34v, v en =5v, a v =15v/v, t a = +25 ? c, unless otherwise noted.
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 12 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. functional block diagram pgnd1 sw1 bst1 vdd1 pgnd2 sw2 bst2 vdd2 ref1 in1 timer1 in2 ref2 agnd1, 2 timer2 control & gate drive vdd control processor aam tm modulator otp ocp reference uvp control & gate drive vdd aam tm modulator reference otw fault otw en figure 1: functional block diagram
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 13 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. operation the mp7770 is a class d audio amplifier that drives stereo speakers in single-ended configuration or a mono speaker in bridge-tied- load configuration. it uses mps?s patented analog adaptive modulation tm technology to convert the audio input signal into pulses. these pulses drive an internal high-current output stage and?when filtered through an external inductor-capacitor filter?reproduce the input signal across the load. because of the switching class d output stage, power dissipation in the amplifier is drastically reduced when compared against class a, b or a/b amplifiers, and maintains high fidelity with low distortion. ref1 and ref2 are the positive inputs of the two amplifiers. they are set to half the dc power supply input voltage (v dd /2) by the internal circuit. the input capacitor c in decouples the ac signal at the input. the input resister r in and the feedback resistor r fb set the amplifier voltage gain as calculated by the equation: in fb r r av ? ? where: ? channel 1: r fb =r fb1 and r in =r in1 ? channel 2: r fb =r fb2 and r in =r in2 . the mp7770 includes four high-power mosfets; for each channel, the output driver stage uses two 100m ? n-channel mosfets to deliver pulses to the lc output filter to drive the load. to enhance the high-side mosfet (hs- fet), the gate is driven to a voltage higher than the source by the bootstrap capacitor between sw and bs. when the output is low, the bootstrap capacitor is charged from v dd through an internal circuit on the mp7770. the gate of the hs-fet is driven high by the bst voltage, forcing the mosfet gate to a voltage higher than v dd , thus allowing the mosfet to turn on and reducing amplifier power loss. pop elimination when used in a single-ended output configuration, the capacitors c out1 and c out2 block the dc signal and pass the ac signals to the load. to insure that the amplifier only passes low-frequency signals, the time constant of c out *r load is large. however, when en goes high, the capacitor charges over a long period and can result in turn-on/turn-off ?pop? in typical amplifiers. the mp7770 integrates a source-current function to charge the dc block capacitors c out1 and c out2 and c in1 and c in2 at start-up. two internally-generated currents flow to the sw pin (i initialization_sw ) and the in pin (i initialization_in ) during start-up, which helps to eliminate turn-on pop. the rising/falling slew rate of the sw node start-up current (i initialization_sw ) is out of audio band (means rise and falling gradually), can be adjusted from the timer capacitor c timer and the voltage of sw node; the larger the c timer capacitance, the smaller the slew rate of the i initialization_sw . after driving the en pin low, the output sw immediately switches to high impedance to eliminate turn-off pop. short circuit/overload protection and monitoring the mp7770 is fully-protected against over- current and thermal overload conditions as explained below and \shown in figure2. short circuit/overload protection the mp7770 has internal overload and short- circuit protection. the currents in both the high- side and low-side mosfets (ls-fets) are measured and if the current exceeds the short circuit current limit (typically 8a), both mosfets will be turned off for a fixed duration (around 1ms) before resuming normal operation. after the fixed duration and the short circuit condition is removed, the mp7770 will restart with the start-up sequence that is used for normal starting to prevent a pop from occurring.
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 14 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. over-temperature shutdown thermal monitoring is also integrated into the mp7770. if the die temperature rises above 150c, all switches turn off. the temperature must fall below 130c before normal operation resumes, with the same power-up sequence used to prevent popping noise. over-temperature warning output the mp7770 includes an open drain, active low fault indicator output to act as an over- temperature warning (otw). the otw pin is asserted when the die temperature reaches 125c and goes low until the temperature drops below 115c. do not apply more than 6v to the otw pin. fault output the mp7770 includes an open drain, active low fault indicator output on the faultb pin. a fault triggers if either the current limit or thermal shutdown is tripped. a fault on any channel will cause the faultb pin to pull low. a fault on either channel will cause the all outputs to go into high impedance. when the fault goes away, the mp7770 will resume normal operation. do not apply more than 6v to the faultb pin. normal operation overcurrent detected? no disable output, fault =l yes meet restart condition (start up sequence ) ? enable output , fault=h yes yes no temp>125 c no otw =l yes temp<115 c otw=h yes no temp>150 c no disable output , fault =l yes temp<130 c yes no meet restart condition (start up sequence ) ? yes no enable output , fault=h around 1ms time out finished? no figure 2: fault timing chart
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 15 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. enable function the mp7770 en input is an active-high?enable control. to enable the mp7770, drive en with a voltage 2.0v or higher; to disable the amplifier, drive it below 0.4v. while the mp7770 is disabled, the vdd operating current is around 250 a and the output driver mosfets are turned off. programmable uvp mp7770 integrate programmable uvp function, which can be used to shutdown the mp7770 to escape the pop, by controlling the uvp node voltage. the vdd shutdown voltage can be flexibly adjusted by the external resistor, as shown in the figure 3. vdd uvp agnd +2.2v + - r l r h r h_ internal r l _inter nal figure 3: uvp block diagram if external resistor r h and r l is low enough (e.g. r h , r l < 50k ? ) compared with internal resistor, the vdd shutdown voltage (rising threshold) can be calculated by the equation: hl vdd _ shutdown l (r r ) v2.2* r ? ? if the uvp pin is nc, the default vdd shutdown voltage (rising threshold) is 8.4v since there is internal voltage divided circuit. for example, please see the table 1 for recommended uvp setting for reduce the power off pop. table 1 vdd (v) vdd_shutdown (v) r h r l 12 8.6 15k 5.1k 24 19 39k 5.1k 36 26 56k 5.1k thermal information the mp7770 is available in a thermally- enhanced tssop28 package. the user can choose between two package options, with the exposed pad on top or bottom. the thermally-augmented tssop-epr package with the exposed pad on top is designed to interface directly with heat sinks using a thermal interface compound. the heat sink then absorbs heat from the ics and couples it to the local air. if louvers or fans are used, this process can reach equilibrium and heat can be continually removed from the ics. because of the efficiency of the mp7770, heat sinks can be smaller than those required for linear amplifiers. the tssop28-epr is not intended for use without a heatsink. for cases without a heatsink, please use the tssop28-ep with the exposed pad on the bottom.
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 16 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. application information component selection the mp7770 uses a minimal number of external components to complete a stereo se or mono btl class d audio amplifier. the circuit in figure 6 (stereo se application circuit) and figure 7 (mono blt application circuit) are optimized for a 24v power supply. this circuit should be suitable for most applications. use the following sections to design custom circuits. setting the voltage gain the maximum output-voltage swing is limited by the power supply. to achieve the maximum output power, set the gain such that the maximum input signal results in the maximum output voltage swing. for a single-ended (se) output configuration, the maximum output voltage v out(pk) is v dd /2. for a bridge-tied-load (btl) output configuration, the maximum output voltage v out(pk) is v dd . for a given input signal voltage, where v in(pk) is the peak input voltage, the maximum voltage gain is: out(pk ) v in(pk ) v a(max) v ? this voltage-gain setting results in the peak output voltage approaching its maximum for the maximum input signal. in some cases the amplifier is allowed to overdrive slightly, allowing the thd to increase at high power levels, and so a higher gain than a v (max) is required. setting the switching frequency the idle switching frequency (the switching frequency when no audio input is present) is a function of several variables: the supply voltage v dd , the integral capacitor c int and the feedback resistor r fb . lower switching frequencies result in greater inductor ripple, causing more quiescent output voltage ripple, and increasing the output noise and distortion. higher switching frequencies result in greater power loss. the optimum quiescent switching frequency is approximately 600khz. when used to drive stereo speakers in single-ended configuration, set right channel to an idle switching frequency greater than 50khz plus the left channel?s switching frequency by using a different timing capacitor c int . for details, refer to the table 2 for recommended se output configuration design, and table 3 for recommended btl output configuration design. table 2: switching frequency setting for se output configuration v dd (v) gain (v/v) r fb (k ? ) r in (k ? ) left channel right channel c int1 (nf) f sw1 (khz) c int2 (nf) f sw2 (khz) 12 10 100 10 2.2 635 1.8 705 12 20 100 4.99 2.2 635 1.8 705 24 10 75 7.5 5.6 700 4.7 740 24 20 150 7.5 2.2 780 2.7 665 30 10 51 5.1 8.2 780 10 680 30 20 150 7.5 3.3 710 2.7 780 30 30 150 4.99 3.3 710 2.7 780 34 10 51 5.1 10 785 12 610 34 20 100 4.99 4.7 780 5.6 740 34 30 150 4.99 3.9 700 3.3 775 table 3: switching frequency setting for btl output configuration v dd (v) gain (v/v) r fb (k ? ) r in (k ? ) c int1 (nf) f sw1 (khz) 12 10 100 10 2.2 435 12 20 100 4.99 2.2 435 12 30 150 4.99 1.0 440 24 10 100 10 3.3 490 24 20 100 4.99 2.2 570 24 30 150 4.99 1.5 480 30 10 100 10 2.2 465 30 20 100 4.99 3.3 535 30 30 150 4.99 2.2 450 34 10 100 10 3.3 560 34 20 100 4.99 3.3 560 34 30 150 4.99 2.2 470
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 17 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. choosing the output lc filter the inductor-capacitor (lc) filter converts the pulses at sw to the output voltage that drives the speaker. there are two kinds of lc filter structure depending on the output configuration. l f c f c out sw1/2 r load figure 4: se filter configuration l f1 l f2 c y1 c y2 c x sw1 sw2 r lo ad figure 5: btl filter configuration where: ff1f2 ll l ?? , y1 y2 fx y1 y2 cc cc cc ? ?? ? , f1 f2 ll ? ; y1 y2 cc ? the characteristic frequency of the lc filter needs to be high enough to allow high frequency audio to the output, yet needs to be low enough to filter out high frequency products of the pulses from the sw pin. the characteristic frequency of the lc filter is: 0 ff 1 f 2lc ? ??? ? the quality factor (q) of the lc filter is important: if this is too low, output noise will increase; if this is too high, then peaking may occur at high frequencies and reduce the passband flatness. the circuit q is set by the load resistance (speaker resistance, typically 4 ? or 8 ? ). q is calculated as: load load 0f 0f rr q l2fl ?? ?? ?? ? ? 0 is the characteristic frequency in radians/second and f 0 is in hz. use an lc filter with q between 0.7 and 1. the type of inductor and capacitor used in the lc filter.greatly affects the output ripple and noise. use a film capacitor and an inductor with sufficient power rating to supply the output current to the load. the inductor must exhibit soft saturation characteristics: if the inductor exhibits hard saturation, it should operate well below the saturation current. use toroidal cores made of gapped ferrite, mpp, powdered iron, or similar materials. if using either an open or shielded bobbin ferrite core for multi-channel designs, make sure that the start windings of each inductor align (all starting toward the sw pin, or all starting toward the output) to prevent crosstalk or other channel-to-channel interference. output coupling capacitor for se output the output ac coupling capacitor?c out ? serves to pass only the amplified ac signal from the lc filter to the load and to block dc signals. the combination of the coupling capacitor, c out and the load resistance results in a first-order high-pass filter. select c out so that the required minimum frequency passes. the output corner frequency (-3db point), f out , can be calculated as: out load out c r 2 1 f ? ? ? ? ? set the output corner frequency (f out ) at or below the minimum required frequency. the output coupling capacitor carries the full load current, so chose a capacitor such that its ripple current rating is greater than the maximum load current. use low-esr aluminum electrolytic capacitors for best results. input coupling capacitor the input coupling capacitors c in1 and c in2 pass only the ac signal at the input. for a typical system application, the source input signal centers around the circuit ground, while the mp7770 input is at half the power supply voltage (v dd /2). the input coupling capacitor transmits the ac signal from the source
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 18 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. to the mp7770 while blocking the dc voltage. choose an input coupling capacitor such that the corner frequency (f in ) is less than the passband frequency. the corner frequency is calculated as: in in in c r 2 1 f ? ? ? ? ? timer capacitor the start-up source current slew rate is adjusted from the timing capacitor, c timer : the larger the c timer capacitance is, the smaller the start-up current slew rate is. select a c timer value larger than 312nf, so the start-up current slew rate would be smaller than 20ma/50ms which helps eliminate the turn-on pop. the recommended 2.2 f capacitor c timer results in a start-up current slew rate of approximately 20ma/350ms. power source for maximum output power, the amplifier circuit requires a regulated external power source. a high power-supply voltage can deliver more power to a given load resistance, but a power- source voltage exceeding the maximum voltage of 36v can damage the mp7770. the mp7770?s power supply rejection is excellent, though power-supply noise can pass to the output, so care must be taken to minimize power supply noise within the pass-band frequencies. bypass the power supply with a large capacitor (typically aluminum electrolytic) along with a smaller 1 f ceramic capacitor at the mp7770 v dd supply pins. pcb layout circuit layout is critical for optimal performance, low output distortion, and noise. duplicate the evb layout for best results. for layout changes, follow these guidelines and use figure 8 as se layout references, use figure 9 as btl layout reference. 1) place the following components as close to the mp7770 as possible: bootstrap capacitors c bs1 and c bs2 supply the gate drive current to the internal hs-fet. place c bs1 as close to bst1/2 pin and sw1/2 pin as possible. likewise, place c bs2 as close to bst2 pin and sw2 pins as possible. power supply bypass capacitors c byp1 and c byp2 carry the transient current for the switching power stage. to avoid overstressing the mp7770 and excessive output noise, place c byp1 as close to the vdd1 pins and pgnd1 pins as possible, and place c byp2 as close to the vdd2 pins and pgnd2 pins as possible. integral capacitors c int sets the amplifier switching frequencies and are typically on the order of a few nf. place the integral capacitor c int as close to the corresponding input as possible to reduce distortion and noise. for example, place c int1 as close to pins 2 and 3 as possible at se output configuration. reference bypass capacitors for se output when used with se output, cr1 and cr2 filter the ? vdd reference voltages. place c r1 and c r2 as close to the ic as possible to improve power supply rejection and reduce distortion and noise at the output. 2) the inductor-capacitor (lc) filter converts the pulse train at sw to the output voltage that drives the speaker. please keep the filter capacitor close to the inductor. 3) keep the sensitive feedback signal trace on the input side and shield the trace with the agnd plane. make sure that any traces carrying the switch node (sw) voltages are routed far from any input signal traces. if the trace must run near the sw trace near the input, shield the input with a ground plane between the traces. physically separate each channel to
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 19 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. prevent crosstalk. make sure that all inductors used on a single circuit board have the same orientation. route each power supply from the source to each channel individually, not serially. this prevents channel-to-channel coupling through the power supply input. electro-magnetic interference (emi) considerations due to the switching nature of class d amplifiers, care must be taken to minimize the effects of electromagnetic interference from the amplifier. however, proper component selection and careful attention to circuit layout can minimize the effects of the emi due to the amplifier switching. the power inductors are a potential source of radiated emissions. for the best emi performance, use toroidal inductors, since the magnetic field is well-contained inside the core. however toroidal inductors can be expensive to wind. for a more economical solution, use shielded-gapped?ferrite or shielded-ferrite- bobbin-core inductors. these inductors typically do not contain the em field as well toroidal inductors, but can achieve a better balance between good emi performance with low cost. the size of high-current loops that carry rapidly changing currents must be minimized: make sure that the v dd bypass capacitors are as close to the mp7770 as possible. nodes that carry rapidly changing voltage, such as sw, need to be made as small as possible. if sensitive traces run near a trace connected to sw, place a ground shield between the traces.
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 20 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical application circuits mp7770 bst1 sw1 bst2 sw2 ref1 6 5 4 11 9 ch1 input 10 13 14 7,8 1 2 ch1 output ch2 output 18,19 22,23 26,27 20,21 16,17 15 24,25 28 in1 timer1 timer2 ref2 in2 otw fault agnd2 uvp en pgnd2 vdd2 v dd c byp2 c byp1 c vddbyp c f1 l f2 c out2 c f2 c c c fb1 r fb1 ch2 input en pgnd1 vdd1 c fb2 r fb2 c in2 r in2 c in1 r in1 c r2 c 1000 int2 c r1 c int1 otw fault figure 6: 24v vdd stereo se typical application circuit mp7770 bst1 sw1 bst2 sw2 ref1 6 5 4 9 10 78 1 13 2 14 11 sp- sp+ 15 18, 19 24, 25 26, 27 16, 17 28 22, 23 20, 21 in1 timer1 timer2 ref2 in2 otw en1 agnd2 fault uvp agnd1 pgnd2 vdd2 c int 2.2nf c sn2 390pf 50v c sn1 390pf 50v r sn1 10 r sn2 10 c fb2 22pf c fbx2 2pf pgnd1 vdd1 vcc sw2 u1 en vcc sw1 sw2 sw1 input+ c fbx1 2pf c fb1 22pf input- otw fault figure 7: 24v vdd mono btl typical application circuit
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 21 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. uvp timer1 en nc in1 ref1 agnd1 pgnd1 sw1 vdd1 sw2 vdd2 sw1 vdd1 1 7 6 5 4 3 2 8 24 26 19 20 21 22 23 25 vdd2 agnd2 ref2 in2 9 10 bst1 28 27 pgnd1 c byp1 c r1 c r2 r fb2 c fb2 c f2 agnd pgnd c f1 c fb1 r fb1 c vddbyp c int1 c int2 mp7770 timer2 11 nc 12 fault 13 otw 14 sw2 18 pgnd2 17 pgnd2 16 bst2 15 r in1 r in2 c byp2 fb1 fb2 l f2 l f1 c out1 c out2 c bs1 c bs2 agnd pgnd top bottom figure 8: stereo se reference pcb layout uvp timer1 en nc in1 ref1 agnd1 pgnd1 sw1 vdd1 sw2 vdd2 sw1 vdd1 1 7 6 5 4 3 2 8 24 26 19 20 21 22 23 25 vdd2 agnd2 ref2 in2 9 10 bst1 28 27 pgnd1 c byp1 c in1 c in2 r fb2 c fb2 c y2 agnd pgnd c fb1 r fb1 c vddbyp c int1 c int2 mp7770 timer2 11 nc 12 fault 13 otw 14 sw2 18 pgnd2 17 pgnd2 16 bst2 15 r in1 r in2 c byp2 fb1 fb2 l f2 l f1 c x c fbx2 c fbx1 c y1 c bs1 c bs2 c vddbyp top bottom figure 9: mono btl reference pcb layout
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier mp7770 rev.1.0 www.monolithicpower.com 22 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. package information tssop28-ep package outline drawing for 28-tssop w/ exposed paddle mf-po-d-0055 revision 2.0 side view note: 1) all dimensions are in millimeters . 2) package length does not include mold flash , protrusion or gate burr. 3) package width does not include interlead flash or protrusion. 4) lead coplanarity (bottom of leads after forming ) shall be 0.10 millimeters max. 5) drawing conforms to jedec mo-153, variation aet. 6) drawing is not to scale . 0.45 0.75 0 o -8 o 0.25 bsc gauge plane 9.60 9.80 pin 1 id 4.30 4.50 6.20 6.60 1 14 15 28 top view 0.09 0.20 see detail " " bottom view 2.60 3.10 5.40 5.90 0.19 0.30 seating plane 0.65 bsc 0.80 1.05 1.20 max 0.00 0.15 front view recommended land pattern 5.80 typ 1.60 typ 0.40 typ 0.65 bsc 3.20 typ 6.00 typ
mp7770 ?2 x 45w stereo se or 90w mono btl class d audio amplifier notice: the information in this document is subject to change wi thout notice. please contact m ps for current specifications. users should warrant and guarantee that third party intellectual property rights ar e not infringed upon when integrating mps products into any application. mps will not assume any legal responsibility for any said applications. mp7770 rev. 1.0 www.monolithicpower.com 23 12/4/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. tssop28-epr package outline drawing for 28-tssop w/ reverse exposed paddle mf-po-d-0xxx preliminary side view note: 1) all dimensions are in millimeters . 2) package length does not include mold flash , protrusion or gate burr. 3) package width does not include interlead flash or protrusion. 4) lead coplanarity (bottom of leads after forming ) shall be 0.10 millimeters max. 5) jedec reference is mo-153. 6) drawing is not to scale . 0.45 0.75 0 o -8 o 0.25 bsc gauge plane 9.60 9.80 pin 1 id 4.30 4.50 6.20 6.60 114 15 28 top view 0.09 0.20 see detail " " bottom view 2.60 3.10 5.40 5.90 0.19 0.30 seating plane 0.65 bsc 0.80 1.05 1.20 max 0.00 0.15 front view recommended land pattern 5.80 typ 1.60 typ 0.40 typ 0.65 bsc

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