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november 2012 doc id 023710 rev 1 1/14 AN4171 application note 25 w mono btl class-d audio amp lifier demonstration board based on the tda7491mv introduction the steval-cca043v1 is a demonstration board designed for the evaluation of the tda7491mv mono btl class-d audio amplifier. this application note provides the board specifications and a quick-start list for standalone operation. also included are the schematic, printed circuit board layout and bill of material. due to its high efficiency, the device, assemb led in the psso36 (slug-down) package, is capable of dissipating heat without a heatsink. jumpers on the board allow the configuration of the amplifier in order to verify the input signal as single-ended or differential and choose the fixed gain settings. microswitches are also provided to enable the standby and mute functions. the main features of the tda7491mv include: 25 w continuous output power at thd = 10%, r l = 6 , v cc = 16 v 20 w continuous output power at thd = 10%, r l = 8 , v cc = 18 v wide-range, single-supply operation (5 v - 18 v) high efficiency ( = 90%) four selectable, fixed gain settings (20 db, 26 db, 30 db and 32 db) differential inputs to minimize common-mode noise filterless operation up to 15 w, r l = 8 , v cc =18 v standby and mute features short-circuit and thermal overload protections externally synchronizable figure 1. steval-cca043v1 www.st.com
contents AN4171 2/14 doc id 023710 rev 1 contents 1 operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 demonstration board preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3 inputs and outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.4 powering up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.5 gain settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.6 single-ended or differential input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.7 board schematic and bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2 pcb layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.1 layout views . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2 design guidelines for pcb schematic and lay out . . . . . . . . . . . . . . . . . . . . 9 2.2.1 dumping network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2.2 main filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.2.3 layout recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
AN4171 operation doc id 023710 rev 1 3/14 1 operation the tda7491mv demonstration board specifications are as follows: power supply voltage range: 5 v to 18 v number of channels: 1 btl (bridge-tied load) load impedance: 4 to 8 gain settings: 20 db, 26 db, 30 db, 32 db undervoltage protection (uvp): 4.5 v 1.1 power supply a single power supply is required to feed the tda7491mv demonstration board via the connector j2 (see figure 2 ). connect the positive voltage of the 25 v/3 a dc power supply to the +vcc pin and the negative to gnd. note: voltage range 5 v to 18 v = 3 a current capability 1.2 demonstration board preparation 1. ensure that the power supply is switched off. 2. connect the regulated power supply, adjusted in the device operating range, to the connector j2 (observe the polarity). 1.3 inputs and outputs 1. connect the loads across the connectors j3 (lef t) and j4 (right), the specified impedance ranges from 6 to 8 . 2. connect the analog audio inputs, either differential or single-ended, to the l-input and r-input rca plugs (j1). refer to figure 2: demonstration board connections on page 4 . table 1. input configuration input configuration jumper j8 (right) jumper j9 (left) differential open open single-ended closed closed
operation AN4171 4/14 doc id 023710 rev 1 figure 2. demonstration board connections 1.4 powering up before powering up the demonstration board, ensure that the tda7491mv is in standby and mute conditions and the gain is set to the desired value (default 20 db). verify also the dedicated switches and jumpers. figure 3. standby and mute switches stby mute analog input dummy load gnd vcc table 2. standby and mute settings stby (s1) mute (s2) status l l stby l h stby hlmute hhplay l l h h s1= stby s2= mute
AN4171 operation doc id 023710 rev 1 5/14 1.5 gain settings figure 4. jumpers j5 and j6 1.6 single-ended or differential input jumper j9 is used to modify the input signal configuration. figure 5. jumper j9 table 3. configuration of jumpers j5 and j6 gain 0 (j5) gain 1 (j6) gain (db) open (l) open (l) 20 open (l) closed (h) 26 closed (h) open (l) 30 closed (h) closed (h) 32 table 4. configuration of jumper j9 input configuration jumper (j9) differential open single-ended closed jumper j 9
operation AN4171 6/14 doc id 023710 rev 1 1.7 board schematic and bill of material figure 6. steval-cca043v1 schematic
AN4171 operation doc id 023710 rev 1 7/14 table 5. bill of material package description qty reference manufacturer c0603 330 pf 50 v npo 5% 1 c27 murata c0603 1 nf 50 v 10% 2 c3, c4 murata c0603 100 nf 50 v 10% 8 c5, c6, c8, c9, c10, c24, c25, c28 murata c0603 470 nf 50 v 10% 2 c1, c2 murata c0603 2.2 f, 16 v 10% 3 c7, c15, c29 murata c0603 1 f, 16 v, 10% 2 c16, c17 murata e-cap 1000 f, 25 v, 10%, pitch = 5.0 mm 1 c23 rubycon c1206 10 f, 25 v, 20%, y5v 4 c30, c31, c32, c33 murata mcap 220 nf, 50 v, 10% pitch=5.0mm 1 c26 murata r0603 22 ohm, 10%, 1/16 w 2 r6, r7 murata r0603 2.2k ohm, 10%, 1/16 w 1 r8 murata r0603 9.1k ohm, 10%, 1/16 w 1 r13 murata r0603 33k ohm, 10%, 1/16 w 2 r2, r4 murata r0603 39k ohm, 10%, 1/16 w 1 r3 murata r0603 100k ohm, 10%, 1/16 w 1 r1 murata psso36 slug-down tda7491mv (sso36) slug-down 1 ic1 stmicroelectronics coil 10x10 33 h 2 a type:7075p-330m (1) 2 l1, l2 kwan sung rca-2p rca socket 1x2p, type av2-8.4-4 1 j1 songcheng to92 l4931cz33, 3v3 regulator 1 ic2 stmicroelectronics cnn-terminal 2p, pitch = 5 mm connector terminal 3 j2, j3 any source 2-way jumper 2p, pitch = 2.5 mm jumper 4 j5, j6, j9 any source slide switch 3p, pitch = 2.5 mm 2 s1, s2 any source 1. alternate part mss1246/mss1260
pcb layout AN4171 8/14 doc id 023710 rev 1 2 pcb layout 2.1 layout views figure 7. top view of pcb layout figure 8. bottom view of pcb layout
AN4171 pcb layout doc id 023710 rev 1 9/14 figure 9. top view of pcb layout - with dimensions 2.2 design guidelines for pcb schematic and layout 2.2.1 dumping network the capacitor is mainly intended for high inductive loads and for common-mode noise attenuation. figure 10. dumping network 65.0mm 40.0mm r1.5mm x 4 r1.2mm x 3 c28 100nf c24 100nf
pcb layout AN4171 10/14 doc id 023710 rev 1 2.2.2 main filter the main filter is an lc butterworth based filter. the cutoff frequency must be chosen between the upper limit of the audio band (~20 khz) and the carrier frequency (310 khz). figure 11. main filter table 6. recommended values r load 8 6 l load 33 h 22 h c load 220 nf 220 nf
AN4171 pcb layout doc id 023710 rev 1 11/14 2.2.3 layout recommendations the following figures illustrate layout recommendations. solder the 100 nf bypass capacitor (x7r) as close as possible to the ic v cc pins (recommended distance to be within 3 mm) in order to avoid spikes generated by the stray inductance caused by the copper supply lines. figure 12. capacitor soldered as close as possible to v cc pins solder the snubber network as close as possible to the related ic pin. a voltage spike dangerous for device operation could occur if the snubber network is far from the output pins. it is recommended that the distance between the snubber network and the output pins be within 5 mm. figure 13. snubber network soldered as close as possible to relevant ic pin ground pin and vcc pin of 100nf capacitor should be directly connected to the related ic pin snubber
pcb layout AN4171 12/14 doc id 023710 rev 1 place the rc filter for the rosc pin close to the ic. figure 14. rc filter place the filter capacitor for svr, vr ef, svcc, vss and vddpw close to the ic. figure 15. filter capacitor rc filter : c8,r 3 vdds-c5 svr-c16 vref-c17 svcc/vss-c1 0
AN4171 revision history doc id 023710 rev 1 13/14 3 revision history table 7. document revision history date revision changes 13-nov-2012 1 initial release.
AN4171 14/14 doc id 023710 rev 1 please read carefully: information in this document is provided solely in connection with st products. stmicroelectronics nv and its subsidiaries (?st ?) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described he rein at any time, without notice. all st products are sold pursuant to st?s terms and conditions of sale. purchasers are solely responsible for the choice, selection and use of the st products and services described herein, and st as sumes no liability whatsoever relating to the choice, selection or use of the st products and services described herein. no license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. i f any part of this document refers to any third party products or services it shall not be deemed a license grant by st for the use of such third party products or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoev er of such third party products or services or any intellectual property contained therein. unless otherwise set forth in st?s terms and conditions of sale st disclaims any express or implied warranty with respect to the use and/or sale of st products including without limitation implied warranties of merchantability, fitness for a parti cular purpose (and their equivalents under the laws of any jurisdiction), or infringement of any patent, copyright or other intellectual property right. unless expressly approved in writing by two authorized st representatives, st products are not recommended, authorized or warranted for use in milita ry, air craft, space, life saving, or life sustaining applications, nor in products or systems where failure or malfunction may result in personal injury, death, or severe property or environmental damage. st products which are not specified as "automotive grade" may only be used in automotive applications at user?s own risk. resale of st products with provisions different from the statements and/or technical features set forth in this document shall immediately void any warranty granted by st for the st product or service described herein and shall not create or extend in any manner whatsoev er, any liability of st. st and the st logo are trademarks or registered trademarks of st in various countries. information in this document supersedes and replaces all information previously supplied. the st logo is a registered trademark of stmicroelectronics. all other names are the property of their respective owners. ? 2012 stmicroelectronics - all rights reserved stmicroelectronics group of companies australia - belgium - brazil - canada - china - czech republic - finland - france - germany - hong kong - india - israel - ital y - japan - malaysia - malta - morocco - philippines - singapore - spain - sweden - switzerland - united kingdom - united states of america www.st.com

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