AN4171 Application note 25 W mono BTL class-D audio amplifier 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, assembled 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%, RL = 6 Ω, VCC = 16 V ■ 20 W continuous output power at THD = 10%, RL = 8 Ω, VCC = 18 V ■ Wide-range, single-supply operation (5 V - 18 V) ■ High efficiency (η = 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, RL = 8 Ω, VCC =18 V ■ Standby and mute features ■ Short-circuit and thermal overload protections ■ Externally synchronizable Figure 1. November 2012 STEVAL-CCA043V1 Doc ID 023710 Rev 1 1/14 www.st.com Contents AN4171 Contents 1 2 3 2/14 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 PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.1 Layout views . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2 Design guidelines for PCB schematic and layout . . . . . . . . . . . . . . . . . . . . 9 2.2.1 Dumping network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2.2 Main filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.2.3 Layout recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Doc ID 023710 Rev 1 AN4171 1 Operation Operation The TDA7491MV demonstration board specifications are as follows: 1.1 ● Power supply voltage range: 5 V to 18 V ● Number of channels: 1 BTL (Bridge-Tied Load) ● Load impedance: 4 Ω to 8 Ω ● Gain settings: 20 dB, 26 dB, 30 dB, 32 dB ● Undervoltage protection (UVP): 4.5 V 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 1.3 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). Inputs and outputs 1. Connect the loads across the connectors J3 (LEFT) and J4 (RIGHT), the specified impedance ranges from 6 to 8 Ω. 2. Connect the analog audio inputs, either differential or single-ended, to the L-input and R-input RCA plugs (J1). Table 1. Input configuration Input configuration Jumper J8 (right) Jumper J9 (left) Differential Open Open Single-ended Closed Closed Refer to Figure 2: Demonstration board connections on page 4. Doc ID 023710 Rev 1 3/14 Operation Figure 2. AN4171 Demonstration board connections Dummy load STBY MUTE Analog Input 1.4 GND Vcc 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. Table 2. Figure 3. Standby and mute settings STBY (S1) MUTE (S2) Status L L STBY L H STBY H L MUTE H H PLAY Standby and mute switches S1= STBY L H L H S2= MUTE 4/14 Doc ID 023710 Rev 1 AN4171 1.5 Operation Gain settings Table 3. Figure 4. 1.6 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 Jumpers J5 and J6 Single-ended or differential input Jumper J9 is used to modify the input signal configuration. Table 4. Figure 5. Configuration of jumper J9 Input configuration Jumper (J9) Differential Open Single-ended Closed Jumper J9 Jumper J9 Doc ID 023710 Rev 1 5/14 Operation AN4171 1.7 Board schematic and bill of material Figure 6. STEVAL-CCA043V1 schematic 6/14 Doc ID 023710 Rev 1 AN4171 Table 5. Package Operation Bill of material 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 µF, 16 V ±10% 3 C7, C15, C29 Murata C0603 1 µF, 16 V, ±10% 2 C16, C17 Murata E-cap 1000 µF, 25 V, ±10%, pitch = 5.0 mm 1 C23 C1206 10 µF, 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 µh 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 Rubycon 1. Alternate part MSS1246/MSS1260 Doc ID 023710 Rev 1 7/14 PCB layout AN4171 2 PCB layout 2.1 Layout views 8/14 Figure 7. Top view of PCB layout Figure 8. Bottom view of PCB layout Doc ID 023710 Rev 1 AN4171 PCB layout Figure 9. Top view of PCB layout - with dimensions 65.0mm R1.2mm x 3 40.0mm R1.5mm x 4 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 C28 100nF C24 100nF Doc ID 023710 Rev 1 9/14 PCB layout 2.2.2 AN4171 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. 10/14 Recommended values RLOAD 8Ω 6Ω LLOAD 33 µH 22 µH CLOAD 220 nF 220 nF Doc ID 023710 Rev 1 AN4171 2.2.3 PCB layout Layout recommendations The following figures illustrate layout recommendations. Solder the 100 nF bypass capacitor (X7R) as close as possible to the IC VCC 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 VCC pins Ground pin and Vcc pin of 100nF capacitor should be directly connected to the related IC pin 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 Snubber Doc ID 023710 Rev 1 11/14 PCB layout AN4171 Place the RC filter for the ROSC pin close to the IC. Figure 14. RC filter RC filter : C8,R3 Place the filter capacitor for SVR, VREF, SVCC, VSS and VDDPW close to the IC. Figure 15. Filter capacitor VDDS-C5 SVR-C16 SVCC/Vss-C10 Vref-C17 12/14 Doc ID 023710 Rev 1 AN4171 3 Revision history Revision history Table 7. Document revision history Date Revision 13-Nov-2012 1 Changes Initial release. Doc ID 023710 Rev 1 13/14 AN4171 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 herein 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 assumes no liability whatsoever relating to the choice, selection or use of the ST products and services described herein. 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