AN3412 10 W +10 W dual BTL class-D audio amplifier demonstration board based on the TDA7491P Introduction The STEVAL-CCA028V1 is a demonstration board designed for the TDA7491P dual BTL class-D audio amplifier. This application note provides the board specifications and a quickstart 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 any heatsink. Jumpers on the board allow configuring the amplifier in order to verify all the features as single-ended or differential inputs, fixed gain settings. Microswitches are also provided to enable the standby and mute functions. The main features of the TDA7491P include: ■ 10 W +10 W continuous output power at THD =10%, RL = 6 Ω, VCC = 11 V ■ 9.5 W +9.5 W continuous output power at THD = 10%, RL = 8 Ω, VCC =12 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 ■ Standby and mute features ■ Short-circuit and thermal overload protections ■ Externally synchronizable Figure 1. June 2011 STEVAL-CCA028V1 Doc ID 018920 Rev 1 1/15 www.st.com Contents AN3412 Contents 1 2 3 2/15 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Doc ID 018920 Rev 1 AN3412 1 Operation Operation The TDA7491P demonstration board specifications are as follows: 1.1 ● Power supply voltage range: 5 V to 18 V ● Number of channels: 2 BTL (Bridge Tied Load) stereo ● 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 TDA7491P demonstration board via the connector J2 (see Figure 2). Connect the positive voltage of the 25 V/ 5 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 Section Figure 2.: Demonstration board connections on page 4. Doc ID 018920 Rev 1 3/15 Operation AN3412 Figure 2. Demonstration board connections STBY MUTE Dummy Load GND +VCC Analog Inputs Dummy Load 1.4 Powering up Before powering up the demonstration board, ensure that the TDA7491P 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 4/15 Doc ID 018920 Rev 1 AN3412 1.5 Operation Gain settings Table 3. Configuration of jumpers J5 and J6 Figure 4. 1.6 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 Jumpers J8 and J9 are used to modify the input signal configuration. Table 4. Configuration of jumpers J8 and J9 Input configuration Left (J9) Right (J8) Differential Open Open Single-ended Closed Closed Figure 5. Jumpers J8 and J9 Doc ID 018920 Rev 1 5/15 Operation AN3412 1.7 Board schematic and bill of material Figure 6. STEVAL-CCA028V1 schematic C3 1nF C4 1nF C1 470nF C2 470nF C5 100nF )RU6LQJOH(QGHG - C6 100nF ,15 ,15 4 3 R3 39K - VDDS 31 GAIN1 - )RU6LQJOH(QGHG,QSXW C10 100nF - C11 470nF C13 1nF C12 470nF 3V3 C14 6 087( 1 3 2 1 3 2 6 67%< OUT & 1 X) ,& IN L4931CZ33 3 2 GND 1nF R4 33k + R2 N + 5 VCC N & R13 Q) 9.1k 932:(56833/< 6/15 33 INNB 21 MUTE C15 2.2uF 16V 20 STBY C7 2.2uF 16V C27 330pF OUTNA 10 OUTNA 11 L3 2 287/ 287/ IC1 TDA7492P (TDA7491P/LP/HV) OUTPB 3 OUTPB 2 C24 100nF J2 C30 C31 C32 C33 C23 + 10uF 16V+ + + + 470uF OPTION 25V L1 PVCCB 7 PVCCB 6 C18 100nF R5 22R OUTNB 9 OUTNB 8 L2 9&& 2 *1' J4 C21 330pF 1 1 & Q) C19 100nF PGNDB 5 PGNDB 4 32 INPB J3 & Q) PVCCA 12 PVCCA 13 35 SVCC 36 VSS C28 100nF R6 22R 1 18 PGND 30 GAIN0 C25 100nF DIAG 24 ROSC C8 100nF L4 27 SGND 25 SYNCLK ,1/ ,1/ PGNDA 14 PGNDA 15 19 VDDPW J1 2 23 INNA R1 100k 28 SYNCLK 1 OUTPA 16 OUTPA 17 26 VDDS R7 22R Input 1 SUB_GND 22 INPA 2 2875 2875 C22 100nF VREF 34 + SVR 29 + 7'$3 &/$66'$03/,),(5 Doc ID 018920 Rev 1 C17 1uF 16V C16 1uF 16V LC FILTER COMPONENT Load L1,L2,L3,L4 C20,C26 4 ohm 15 uH 470 nF 6 ohm 22 uH 220 nF 8 ohm 33 uH 220 nF 16 ohm 68 uH 220 nF AN3412 Table 5. Package Operation Bill of material Description Qty Reference Manufacturer C0603 330 pF 50 V NPO ±5% 2 C21, C27 Murata C0603 1 nF 50 V ±10% 4 C3, C4, C13, C14 Murata C0603 100 nF 50 V ±10% 11 C5, C6, C8, C9, C10, C18, C19, C22, C24, C25, C28 Murata C0603 470 nF 50 V ±10% 4 C1, C2, C11, C12 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 8X20 470 µF, 25 V, ±10%, pitch = 5.0 mm 1 C23 C1206 10 µF, 25 V, ±20%, Y5V 4 C30, C31, C32, C33 Murata Mcap 7x5 220 nF, 50 V, ±10% 2 C20, C26 Murata R0603 22 ohm, ±10%, 1/16 W 3 R5, 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 TDA7491P (SSO36) slug-down 1 IC1 STMicroelectronics Coil 10X10 33 µh 2 A coil MSS1046-333ML(1) 4 L1, L2, L3, L4 RCA-2P RCA socket 2Px2, type AV2-8.4-12 1 J1 Songcheng TO92 L4931CZ33, 3V3 regulator 1 IC2 STMicroelectronics CNN-Terminal 2P, pitch = 5 mm connector terminal 3 J2, J3, J4 Any source 2-way jumper 2P, pitch = 2.5 mm jumper 4 J5, J6, J8, J9 Any source Slide switch 3P, pitch = 2.5 mm 2 S1, S2 Any source Panasonic Coilcraft 1. Alternate part MSS1246/MSS1260 Doc ID 018920 Rev 1 7/15 PCB layout AN3412 2 PCB layout 2.1 Layout views 8/15 Figure 7. Top view of PCB layout Figure 8. Bottom view of PCB layout Doc ID 018920 Rev 1 AN3412 PCB layout 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 Doc ID 018920 Rev 1 9/15 PCB layout 2.2.2 AN3412 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. 10/15 Recommended values RLOAD 8Ω 6Ω LLOAD 33 µH 22 µH CLOAD 220 nF 220 nF Doc ID 018920 Rev 1 AN3412 2.2.3 PCB layout Layout recommendations The following figures illustrate layout recommendations. Solder 100 nF bypass capacitors (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. Capacitors soldered as close as possible to VCC pins Ground pin and VCC pin of 100nF capacitor should be connected to IC related pin directly Solder the snubber networks as close as possible to the IC related 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 networks soldered as close as possible to relevant IC pin Doc ID 018920 Rev 1 11/15 PCB layout AN3412 Put the RC filter for the ROSC pin close to the IC. Figure 14. RC filter Put the filter capacitor for SVR, VREF, SVCC, VSS and VDDPW close to the IC. Figure 15. Filter capacitor 12/15 Doc ID 018920 Rev 1 AN3412 PCB layout Signal ground should be directly connected to the negative terminal of the bulk capacitor. Figure 16. Signal ground routing Signal gnd C23 gnd pin Doc ID 018920 Rev 1 13/15 Revision history 3 AN3412 Revision history Table 7. 14/15 Document revision history Date Revision 15-Jun-2011 1 Changes Initial release. Doc ID 018920 Rev 1 AN3412 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. 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