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MP7740 15w class d mono single ended audio amplifer MP7740 rev. 0.9 www.monolithicpower.com 1 9/22/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. the future of analog ic technology description the MP7740 is a mono 15w class d audio amplifier. it is one of mps? products of fully integrated audio amplifiers which dramatically reduces solution size by integrating the following: 250m ? power mosfets startup / shutdown pop elimination short circuit protection circuits the MP7740 utilizes a single ended output structure capable of delivering 15w into 4 ? speakers. mps class d audio amplifiers exhibit the high fidelity of a class a/b amplifier at high efficiencies. the circuit is based on the mps? proprietary variable frequency topology that delivers excellent linearity, fast response time and operates on a single power supply. features ? 15w output at v dd = 24v into a 4 ? load ? thd+n = 0.05% at 1w, 8 ? ? 90% efficiency at 15w & v dd =24v ? low noise (103v typical) ? switching frequency up to 1mhz ? 9.5v to 36v operation from a single supply ? integrated startup and shutdown pop elimination circuit ? thermal and short circuit protection ? integrated power fets ? pin compatible with mp7720 ? available in tiny 8-pin soic package applications ? portable docking stations ? surround sound dvd systems ? televisions ? flat panel monitors ? multimedia computers ? home stereo systems ?mps? and ?the future of analog ic technology? are registered trademarks of monolithic power systems, inc. aam (analog adaptive modulation) is a trademark of monolithic power systems, inc. typical application + audio input off on v dd MP7740 sw bs pgnd vdd pin en nin agnd 8 6 5 7 1 4 2 3 thd+n vs. p out v dd =24v , freq=1khz,a-wtd thd+n (%) 0.01 20 0.02 0.05 0.1 0.2 0.5 1 2 5 10 60m 200m 1 5 20 p out (w)
MP7740 ? 15w class d mono single ended audio amplifier MP7740 rev. 0.9 www.monolithicpower.com 2 9/22/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. ordering information *for tape & reel, add suffix ?z (eg. MP7740dn?z); for rohs compliant packaging, add suffix ?lf (eg. MP7740dn?lf?z) package reference pin nin agnd en pgnd sw vdd bs 1 2 3 4 8 7 6 5 top view exposed pad on backside absolute maxi mum ratings (1) supply voltage v dd ...................................... 40v bs voltage .................. v sw ? 0.3v to v sw + 6.5v enable voltage v en ........................?0.3v to +6v v sw ................... ?1v (-5v for <10ns) to v dd + 1v v pin , v nin ................................... ?1v to v dd + 1v agnd to pgnd ..........................?0.3v to +0.3v continuous power dissipation (t a = +25c) (2) ??????????????????...2.5w junction temperature ............................... 150 c lead temperature ....................................260 c storage temperature.............. ?65 c to +150 c recommended operating conditions (3) supply voltage v dd ..........................9.5v to 36v operating temperature t a ........ ?40 c to +85 c thermal resistance (4) ja jc soic8e .................................. 50 ....... 8......... c 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. part number* package top marking temperature MP7740dn soic8e MP7740dn ?40 c to +85 c
MP7740 ? 15w class d mono single ended audio amplifier MP7740 rev. 0.9 www.monolithicpower.com 3 9/22/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. electrical characteristics (5, 6) v dd = 24v, v en = 5v, t a = +25 c, unless otherwise noted. parameters symbol condition min typ max units supply current standby current v en = 0v 20 50 a quiescent current sw=0v 1.5 3.0 ma output drivers sw on resistance sourcing and sinking 0.25 ? short circuit current sourcing and sinking 4.5 a inputs pin, nin input common mode voltage range 0 v dd 2 v dd ? 1.5 v pin, nin input current v pin = v nin = 12v 1 5 a v en rising 1.8 2.5 v en enable threshold voltage v en falling 0.8 1.2 v en enable input current v en = 5v 1 a thermal shutdown thermal shutdown trip point t j rising 150 c thermal shutdown hysteresis 30 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. operating specifications (7) circuit of figure 1, v dd = 24v, v en = 5v, t a = +25 c, unless otherwise noted. parameters symbol condition min typ max units standby current v en = 0v 130 a quiescent current 13 ma f = 1khz, thd+n = 10%, 4 ? load 15 w power output f = 1khz, thd+n = 10%, 8 ? load 8 w p out = 1w, f = 1khz, 4 ? load 0.05 % thd+ noise p out = 1w, f = 1khz, 8 ? load 0.018 % f = 1khz, p out = 15w, 4 ? load 90 % efficiency f = 1khz, p out = 8w, 8 ? load 90 % maximum power bandwidth 20 khz dynamic range 97 db noise floor a-weighted 103 v f = 1khz -60 db power supply rejection v cc =24v, gain=8.25v/v, v ripple =200mv pp c r =100f f = 100hz -60 db notes: 7) operating specifications are for the ic in typical application circuit (figure 1).
MP7740 ? 15w class d mono single ended audio amplifier MP7740 rev. 0.9 www.monolithicpower.com 4 9/22/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. pin functions pin # name description 1 pin amplifier positive input. pin is the positive side of the differential input to the amplifier. use a resistive voltage divider to set the voltage at pin to v dd /2. see figure 1. 2 nin amplifier negative input. nin is the negative side of the differential input to the amplifier. drive the input signal and close the feedbac k loop at nin. see figure 1. 3 agnd analog ground. connect agnd to pgnd at a single point. 4 en enable input. drive en high to turn on the amplifier, low to turn it off. 5 bs high-side mosfet bootstrap input. a capaci tor from bs to sw supplies the gate drive current to the internal high-side mosfet. 6 vdd power supply input. vdd is the drain of t he high-side mosfet switch, and supplies the power to the output stage and the MP7740 internal control circuitry. in addition to the main bulk capacitor, bypass vdd to pgnd with a 1f x7r capacitor placed close to pins 6 and 8. 7 sw switched power output. sw is the output of the MP7740. connect the lc filter between sw and the output coupling capacitor. see figure 1. 8 pgnd power ground. connect pgnd to agnd at a single point. exposed pad connect exposed pad to gnd plane for proper thermal performance.
MP7740 ? 15w class d mono single ended audio amplifier MP7740 rev. 0.9 www.monolithicpower.com 5 9/22/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. typical performance curves circuit of figure 1, v dd =24v, v en =5v, a v =8.25v/v, t a = +25 c, unless otherwise noted. amplitude (dbr) amplitude (dbv) frequency (hz) frequency (khz) 2 -120 -100 -80 -60 -40 -20 0 4 6 8 101214161820 frequency (hz) amplitude (db) amplitude (dbv) -120 -100 -80 -60 -40 -20 0 frequency (khz) 2 4 6 8 10 12 14 16 18 20 -10 +4 -8 -6 -4 -2 +0 +2 40k 20 100 1k 10k 40k 20 100 1k 10k -10 -8 -6 -4 -2 0 +2 +4 thd+n (%) thd+n (%) thd+n (%) frequency (hz) frequency (hz) 0.01 20 0.02 0.05 0.1 0.2 0.5 1 2 5 10 60m 200m 1 5 20 0.01 20 0.02 0.05 0.1 0.2 0.5 1 2 5 10 60m 200m 1 5 20 freq=1khz freq=100hz freq=10khz freq=10khz freq=1khz 20 100 500 2k 10k 0.01 20 0.02 0.05 0.1 0.2 0.5 1 2 5 10 20 100 500 2k 10k 0.01 20 0.02 0.05 0.1 0.2 0.5 1 2 5 10 thd+n (%) p out (w) p out (w) freq=100hz -80 +0 -7 0 -6 0 -5 0 -4 0 -30 -20 -10 20 100 500 2k 10k frequency (hz) amplitude (db)
MP7740 ? 15w class d mono single ended audio amplifier MP7740 rev. 0.9 www.monolithicpower.com 6 9/22/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. typical performance curves (continued) circuit of figure 1, v dd =24v, v en =5v, t a = +25 c, unless otherwise noted. 100 500 50 20 1k 2k 5k 10k 20k p out (w) p out (w) v dd (v) amplitude (dbv) -120 -100 -80 -60 -40 -20 0 amplitude (dbv) efficiency (%) -120 0 10 20 30 40 50 60 70 80 90 100 -100 -80 -60 -40 -20 0 amplitude (db) -120 -100 -80 -60 -40 -20 0 efficiency vs. p out v dd =24v,input signal freq=1khz frequency (hz) frequency (hz) 2 0 4 6 8 10 12 14 16 18 p out vs. v dd input signal freq=1khz 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 40 100 500 50 20 1k 2k 5k 10k 20k amplitude (db) -120 -100 -80 -60 -40 -20 0 frequency (hz) 60 20k 100 200 500 1k 2k 5k 10k 60 30k 100 200 500 1k 2k 5k 10k 20k 10 30 50 70 90 110 130 150 0 5 10 15 output power (w) frequency (hz) thermal rise vs. output power v dd =24v right to left right to left left to right left to right
MP7740 ? 15w class d mono single ended audio amplifier MP7740 rev. 0.9 www.monolithicpower.com 7 9/22/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. operation the MP7740 is a single-ended class d audio amplifier. it uses the monolithic power systems patented analog adaptive modulation tm 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 to class a, b or a/b amplifiers while maintaining high fidelity and low distortion. the amplifier uses differential input to the modulator. pin is the positive input and nin is the negative input. the common mode voltage of the input is set to half the dc power supply input voltage (v dd /2) through the resistive voltage divider. the input capacitor c in couple the ac signal at the input. the amplifier voltage gain is set by the combination of the input resister r in and the feedback resistor r fb and is calculated by the equation: in fb r r av ? = the output driver stage uses two 250m ? n-channel mosfets to deliver the pulses to the lc output filter which in turn drives the load. to fully enhance the high-side mosfet, the gate is driven to a voltage higher than the source by the bootstrap capacitor between sw and bs. while the output is driven low, the bootstrap capacitor is charged from v dd through an internal circuit on the MP7740. the gate of the high-side mosfet is driven high from the voltage at bs, forcing the mosfet gate to a voltage higher than v dd and allowing the mosfet to fully turn on, reducing power loss in the amplifier. pop elimination the capacitor c out blocks the dc signal and pass only ac signals to the load. to insure that the amplifier passes low frequency signals, the time constant of c out *r load needs to be long. however, when en is asserted, the capacitor charges over a long period and in a normal amplifier can result in a turn on and/or turn off ?pop.? the MP7740 includes integrated circuitry that eliminates the turn on and turn off pop associated with the charging of the ac coupling capacitor. short circuit/overload protection the MP7740 has internal overload and short circuit protection. the currents in both the high- side and low-side mosfets are measured and if the current exceeds the 4.5a short circuit current limit, both mosfets are turned off. the MP7740 then restarts with the same power up sequence that is used for normal starting to prevent a pop from occurring after a short circuit condition is removed. a schottky diode (for example, b340la manufactured by diodes inc) is required for short-circuit protection, with the cathode connected to sw and the anode connected to pgnd. please place the diode as close to the MP7740 as possible. if short-circuit protection is not needed, the schottky diode can be omitted. mute/enable function the MP7740 en input is an active high enable control. to enable the MP7740, drive en with a 2.5v or greater voltage. to disable the amplifier, drive it below 1v. while the MP7740 is disabled, the vdd operating current is less than 5a and the output driver mosfets are turned off.
MP7740 ? 15w class d mono single ended audio amplifier MP7740 rev. 0.9 www.monolithicpower.com 8 9/22/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. application information component selection the MP7740 uses a minimum number of external components to complete a stereo class d audio amplifier. the circuit of figure 1 should be suitable for most applications, and use the following sections to determine how to customize the amplifier for a particular application. setting the voltage gain the maximum output voltage swing is limited by the power supply. to achieve the maximum power out of the MP7740 amplifier, set the gain such that the maximum input signal results in the maximum output voltage swing. the maximum output voltage swing is v dd /2. for a given input signal voltage, where v in (pk) is the peak input voltage, the maximum voltage gain is: ) pk ( v 2 v ) max ( a in dd v = this voltage gain setting results in the peak output voltage approaching it?s 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 timing capacitor c int and the feedback resistor r fb . lower switching frequencies result in more inductor ripple, causing more quiescent output voltage ripple and increasing the output noise and distortion. higher switching frequencies result in more power loss. the optimum quiescent switching frequency is approximately 600khz to 700khz. refer to the operating specifications for recommended values. table 1?switching frequency vs. v dd , timing capacitor and feedback resistor (see figure 1) gain (v/v) gain (db) r fb (k ? ) r in (k ? ) c int f sw v dd (v) 3.9 11.8 39 10 6.8nf 660khz 12 8.2 18.3 82 10 3.3nf 660khz 12 8.3 18.4 39 4.7 6.8nf 660khz 12 12.0 21.6 120 10 2.2nf 610khz 12 17.4 24.8 82 4.7 3.3nf 660khz 12 25.5 28.1 120 4.7 2.2nf 610khz 12 5.6 15.0 56 10 8.2nf 670khz 24 8.2 18.3 82 10 5.6nf 720khz 24 11.9 21.5 56 4.7 8.2nf 670khz 24 12.0 21.6 120 10 4.7nf 620khz 24 17.4 24.8 82 4.7 5.6nf 720khz 24 25.5 28.1 120 4.7 4.7nf 620khz 24 33.0 30.4 330 10 1.8nf 700khz 24 choosing the lc filter the inductor-capacitor (lc) filter converts the pulse train at sw to the output voltage that drives the speaker. 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 sw. the characteristic frequency of the lc filter is: lc 2 1 f 0 = the voltage ripple at the output is approximated by the equation: ? ? ? ? ? ? ? ? ? sw 0 dd ripple f f v v 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 signal frequencies reducing the passband flatness. the circuit q is set by the load resistance (speaker resistance, typically 4 ? or 8 ? ). the q is calculated as:
MP7740 ? 15w class d mono single ended audio amplifier MP7740 rev. 0.9 www.monolithicpower.com 9 9/22/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. = = 00 load load ll q2f rr 0 is the characteristic frequency in radians per second and f 0 is in hz. use an lc filter with q between 0.7 and 1. the actual output ripple and noise is greatly affected by the type of inductor and capacitor used in the lc filter. use a film capacitor and an inductor with sufficient power handling capability to supply the output current to the load. the inductor should exhibit soft saturation characteristics. if the inductor exhibits hard saturation, it should operate well below the saturation current. gapped ferrite, mpp, powdered iron, or similar type toroidal cores are recommended. if open or shielded bobbin ferrite cores are used for multi-channel designs, make sure that the start windings of each inductor line up (all starts going toward sw pin, or all starts going toward the output) to prevent crosstalk or other channel-to-channel interference. output coupling capacitor the output ac coupling capacitor c out serves to block dc voltages and thus passes only the amplified ac signal from the lc filter to the load. the combination of the coupling capacitor, c out and the load resistance results in a first-order high-pass filter. the value of c out should be selected such that the required minimum frequency is still allowed to pass. 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 a capacitor should be chosen such that its ripple current rating is greater than the maximum load current. low esr aluminum electrolytic capacitors are recommended. input coupling capacitor the input coupling capacitor c in is used to pass only the ac signal at the input. in a typical system application, the source input signal is typically centered around the circuit ground, while the MP7740 input is at half the power supply voltage (v dd /2). the input coupling capacitor transmits the ac signal from the source to the MP7740 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 = power source for maximum output power, the amplifier circuit requires a regulated external power source to supply the power to the amplifier. the higher the power supply voltage, the more power can be delivered to a given load resistance, however if the power source voltage exceeds the maximum voltage of 36v, the MP7740 may sustain damage. the power supply rejection of the MP7740 is excellent (typically -60db), however noise at the power supply can get 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 1f ceramic capacitor at the MP7740 v dd supply pins. pcb layout the circuit layout is critical for optimum performance and low output distortion and noise. it is highly recommended to duplicate evb layout for optimum performance. if change is necessary, please follow these guidelines and take figure 2 for references. 1) place the following components as close to the MP7740 as possible: bootstrap cap c bs is used to supply the gate drive current to the internal high-side mosfet. place c bs as close to pins 5 and 7 as possible. power supply bypass c byp carries the transient current for the switching power stage. to prevent overstressing of the MP7740 and excessive noise at the output, place c byp as close to pins 6 (vdd) and 8 (pgnd) as possible.
MP7740 ? 15w class d mono single ended audio amplifier MP7740 rev. 0.9 www.monolithicpower.com 10 9/22/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. output catch diodes d sh and d sl carry the current over the dead-time while the mosfet switches are off. place the diodes as close to the MP7740 as possible. timing capacitors c int is used to set the amplifier switching frequencies and are typically on the order of a few nf. place c int as close to pins 1 and 2 as possible to reduce distortion and noise. reference bypass capacitors c r filters the ? v dd reference voltages. place c r 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) when laying out the pcb, use two separate ground planes, analog ground (agnd) and power ground (pgnd), and connect the two grounds together at a single point (usually around the bulk bypass capacitor) to prevent noise injection into the amplifier input to reduce distortion. 4) 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 separated far from any input signal traces. if it is required to run the sw trace near the input, shield the input with a ground plane between the traces. if multiple amplifiers are used on a single board, make sure that each channel is physically separated to prevent crosstalk. make sure that all inductors used on a single circuit board have the same orientation. if multiple amplifiers are used on a single board, make sure that the power supply is routed 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 the class d amplifier, care must be taken to minimize the effects of electromagnetic interference from the amplifier. however, with proper component selection and careful attention to circuit layout, the effects of the emi due to the amplifier switching can be minimized. 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 field as well toroidal inductors, but usually can achieve a better balance of good emi performance with low cost. the size of high-current loops that carry rapidly changing currents needs to be minimized. to do this, make sure that the v dd bypass capacitors are as close to the MP7740 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.
MP7740 ? 15w class d mono single ended audio amplifier MP7740 rev. 0.9 www.monolithicpower.com 11 9/22/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. typical application circuit audio input off on v dd MP7740 sw bs pgnd vdd pin en nin agnd c r c fb c f l f c byp c bs c vddbyp c out d sl (optional) (8) c int c in r in r fb r rh r rl 8 6 5 7 1 4 2 3 output 22pf 5.6nf figure 1? mono typical application circuit nin en agnd pin vdd bs 1 3 2 6 5 pgnd 8 7 sw r rh c byp r rl c r c bs agnd pgnd c fb r fb c vddbyp c int MP7740 feedback signal c f 4 l f agnd pgnd d sl (optional) (8) top bottom figure 2?reference pcb layout notes: 8) schottky diode d sl only be required for short circuit pr otection. detailed see short circuit/overload protection section in operation information.
MP7740 ? 15w class d mono single ended 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. MP7740 rev. 0.9 www.monolithicpower.com 12 9/22/2009 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2009 mps. all rights reserved. package information soic8e (exposed pad) see detail "a" 0.0075(0.19) 0.0098(0.25) 0.050(1.27) bsc 0.013(0.33) 0.020(0.51) seating plane 0.000(0.00) 0.006(0.15) 0.051(1.30) 0.067(1.70) top view front view side view bottom view note: 1) control dimension is in inches. dimension in bracket is in millimeters. 2) package length does not include mold flash, protrusions or gate burrs. 3) package width does not include interlead flash or protrusions. 4) lead coplanarity (bottom of leads after forming) shall be 0.004" inches max. 5) drawing conforms to jedec ms-012, variation ba. 6) drawing is not to scale. 0.089(2.26) 0.101(2.56) 0.124(3.15) 0.136(3.45) recommended land pattern 0.213(5.40) 0.063(1.60) 0.050(1.27) 0.024(0.61) 0.103(2.62) 0.138(3.51) 0.150(3.80) 0.157(4.00) pin 1 id 0.189(4.80) 0.197(5.00) 0.228(5.80) 0.244(6.20) 14 85 0.016(0.41) 0.050(1.27) 0 o -8 o detail "a" 0.010(0.25) 0.020(0.50) x 45 o 0.010(0.25) bsc gauge plane

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