ST AN3383 APPLICATION NOTE

STA350BW 2.0-channel demonstration board

)

Introduction

The purpose of this application note is to describe:

■ how to connect the STA350BW 2.0-channel demonstration board

■ how to evaluate the demonstration board performance with all the electrical curves

■ how to avoid critical issues in the PCB schematic and layout of the the STA350BW

The STA350BW demonstration board is specifically configured for 2.0 BTL channels,
releasing up to 2 x 50 W into 6 ohm of power output at 25 V of supply voltage using reduced
components. It is a complete solution for the digital audio power amplifier.

Figure 1. STA350BW 2.0-channel demonstration board

AN3383

Application note

Connected with AP
WLink boa rd (I2C
& I2S

VCC
DC 4.5-26V

Speaker Output
L CH

Speaker Output
R CH

AM045230v1

April 2011 Doc ID 018691 Rev 1 1/29

www.st.com

Contents AN3383

Contents

1 Functional description of the demonstration board . . . . . . . . . . . . . . . 4

1.1 Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.2 Output configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.3 Schematic and block diagrams, PCB layout, bill of material . . . . . . . . . . . . 5

2 Test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3 Thermal test results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4 Design guidelines for schematic and PCB layout . . . . . . . . . . . . . . . . 16

4.1 Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4.1.1 Main driver for selection of components . . . . . . . . . . . . . . . . . . . . . . . . 16

4.1.2 Decoupling capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4.1.3 Output filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4.2 PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

5 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2/29 Doc ID 018691 Rev 1

AN3383 List of figures

List of figures

Figure 1. STA350BW 2.0-channel demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Figure 2. Schematic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 3. Block diagram of test connections with equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 4. Top view of PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 5. Bottom view of PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 6. Efficiency (2 channels, BTL configuration), V
Figure 7. Efficiency (2 channels, BTL configuration), V
Figure 8. Output power vs. supply voltage, R
Figure 9. Output power vs. supply voltage, R
Figure 10. Frequency response, V
Figure 11. Crosstalk, V
Figure 12. SNR, V

CC

= 24 V, RL = 6 ohm, 0 dB (Pout = 1 W) . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

CC

= 24 V, RL = 6 ohm, 0 dB (Pout = 1 W) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Figure 13. THD vs. frequency, V
Figure 14. FFT (0 dBFS), V
Figure 15. FFT (-60 dBFS), V

= 24 V, RL = 6 ohm, 0 dBFS (Pout = 1 W) . . . . . . . . . . . . . . . . . . . . . 13

CC

CC

Figure 16. THD vs. output power, V
Figure 17. Output power = 2 x 5 W, V
Figure 18. Output power = 2 x 10 W, V
Figure 19. Output power = 2 x 15 W, V
Figure 20. Output power = 2 x 38 W, V

= 24 V, RL = 6 ohm, 0 dB (Pout = 1 W) . . . . . . . . . . . . . . . . . . 11

CC

= 24 V, RL = 6 ohm, Pout = 1 W . . . . . . . . . . . . . . . . . . . . . . . . . 12

CC

= 24 V, RL = 6 ohm, 0 dBFS (Pout = 1 W) . . . . . . . . . . . . . . . . . . . . 13

= 24 V, RL = 6 ohm, f = 1 kHz . . . . . . . . . . . . . . . . . . . . . . . . 13

CC

CC

CC

CC

CC

= 6 ohm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

L

= 8 ohm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

L

= 26 V, load = 6 ohm, frequency = 1 kHz . . . . . . . . . . . . . . 14

= 26 V, load = 6 ohm, frequency = 1 kHz . . . . . . . . . . . . . 14

= 26 V, load = 6 ohm, frequency = 1 kHz . . . . . . . . . . . . . 15

= 26 V, load = 8 ohm, frequency = 1 kHz . . . . . . . . . . . . . 15

Figure 21. Output filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 22. Power dissipated over the series resistance [P = C*f*(2*V)
Figure 23. Power dissipated over the series resistance [P = C*f*2(V

Figure 24. Damping network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 25. Main filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 26. Recommended power-up and power-down sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 27. Snubber network soldered as close as possible to the related IC pin . . . . . . . . . . . . . . . . 19

Figure 28. Electrolytic capacitor used first to separate the V
Figure 29. Path between V

and ground pin minimized in order to avoid inductive paths . . . . . . . . 20

CC

Figure 30. Large ground planes on the top and bottom sides of the PCB . . . . . . . . . . . . . . . . . . . . . . 21

Figure 31. PLL filter soldered as close as possible to the FILT pin . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 32. Symmetrical paths created for output stage (for differential applications) . . . . . . . . . . . . . 22

Figure 33. Coils separated in order to avoid crosstalk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 34. V

filter for high frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

CC

Figure 35. Decoupling capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 36. Snubber filter for spike high frequency in PWM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 37. Correct common-mode and differential snubber placement . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 38. Correct output routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 39. Comparison of output routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Figure 40. Thermal layout with large ground (1/3 for top and bottom layers) . . . . . . . . . . . . . . . . . . . 26

Figure 41. Thermal layout with large ground (2/3 for thermal and soldering holes). . . . . . . . . . . . . . . 26

Figure 42. Comparison of thermal layout (top layer) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 43. Comparison of thermal layout (bottom layer) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

= 26 V, RL = 6 ohm . . . . . . . . . . . . . . . . . . 9

CC

= 26 V, RL = 8 ohm . . . . . . . . . . . . . . . . . 10

CC

2

]. . . . . . . . . . . . . . . . . . . . . . . 17

2

)] . . . . . . . . . . . . . . . . . . . . . . . 17

branches . . . . . . . . . . . . . . . . . . . . . . 20

CC

Doc ID 018691 Rev 1 3/29

Functional description of the demonstration board AN3383

1 Functional description of the demonstration board

The following terms used in this application note are defined as follows:

● THD+N vs. Freq: Total harmonic distortion plus noise versus frequency curve

● THD+N vs. Pout: Total Harmonic Distortion (THD) plus noise versus output power

● S/N ratio: Signal-to-noise ratio

● FFT: Fast Fourier Transform Algorithm (method)

● CT: Channel separation L to R, or R to L channel crosstalk

The equipment used includes the following:

● Audio Precision (System 2700) by AP Co., USA)

● DC power supply (4.5 V to 26 V)

● Digital oscilloscope (TDS3034B by Tektronix)

● PC (with APWorkbench GUI control software installed)

1.1 Connections

Power supply signal and interface connection

1. Connect the positive voltage of 24V DC power supply to the +Vcc pin and negative to
GND.

2. Connect the APWorkbench board to the J1 connector of the STA350BW demonstration
board.

3. Connect the S/PDIF signal cable to the RCA jack on the APWLink board, connecting to
the signal source such as Audio precision or DVD player.

Note: The voltage range of the DC power supply for V

1.2 Output configuration

The STA350BW demo board is specifically configured in 2 BTL channels. For the software
setup, please refer to the APWUserManualR1.0.pdf.

is 4.5 V to 26 V.

CC

4/29 Doc ID 018691 Rev 1

AN3383 Functional description of the demonstration board

1.3 Schematic and block diagrams, PCB layout, bill of material

Figure 2. Schematic diagram

AM045231v1

Doc ID 018691 Rev 1 5/29

Functional description of the demonstration board AN3383

g

(

)

(

)

Figure 3. Block diagram of test connections with equipment

Audio Precision Equipment

Monitor

Output
to AP

S/PDIF

nal

Si

Digital Oscilloscope

TDS3034B Tektronix

STA350BW

Demo B’D

From 4.5V to26V

I2S Input

DC3V3

DC Power Supply

APWLink Board

DC7V

PC with GUI to control the
chipset

AM045232v1

6/29 Doc ID 018691 Rev 1

AN3383 Functional description of the demonstration board

Figure 4. Top view of PCB layout

Figure 5. Bottom view of PCB layout

AM045233v1

AM045234v1

Doc ID 018691 Rev 1 7/29

Functional description of the demonstration board AN3383

Table 1. Bill of material

No. Type Footprint Description Qty Reference Manufacturer

1 Jack Through-hole 4P Speaker Jack 1 J7 Any source

2 MCAP Through-hole 680NF-M(63V) Capacitor 2 C415SL, C416S Any source

3 Terminal Through-hole 2P Pitch: 5 mm Connector Terminal 1 CN2

4 CNN Through-hole 16P (8 x 2 row) 2.5 mm male CNN 1 J1 Any source

5 CCAP CAP0603 50 volt NPO 330 pF +/- 10% 2 C418A, C425 Murata

6 CCAP CAP0603 50 volt NPO 680 pF +/- 10% 1 C9 Murata

7 CCAP CAP0603 50 volt 1 nF +/- 10% 1 C3 Murata

8 CCAP CAP0603 50 volt 4.7 nF +/- 10% 1 C7 Murata

C2, C4, C5, C11,

C15, C421A,

C421B, C422A,

9 CCAP CAP0603 50 volt 100 nF +/- 10% 15

10 CCAP CAP1206 50 volt 1 µF +/-10% 2 C426A, C426B Murata

11 RES R1206 4R7, +/-5% 1/4W 4

12 RES R1206 20 +/-5% 1/4W 2 R422A, R423 Murata

13 RES R0603 0 ohm 1/16W 1 R31 Murata

C422B, C423A,
C423B, C424A,
C424B, C427A,

C427B

R424A, R424B,

R425A, R425B

Phoenix

Contact

Murata

Murata

14 RES R0603 2R2 +/-5% 1/16W 1 R32 Murata

15 RES R0603 10K +/-5% 1/16W 1 R1 Murata

16 RES R0603 2.2K +/-5% 1/16W 1 R6 Murata

17 RES R0603 NS 2 R4, R5

18 ECAP Through-hole 22 µF/ 16 V 1 C12

19 ECAP Through-hole 1000 µF / 35 V 105 Centigrade 1 C428

20 Plastic rod

21 Plastic rod

22 IC PSSO36 STA350BW 1 IC1 ST

23 Coil Through-hole 15 µH Choke Coil (1014P-01-150L) 4

24 PCB STA350BW 2.0 CH VER1.0 1 Fastprint

Hexagonal rod 15 mm length,
male type

Hexagonal rod 8 mm length,
female type

4 Four Corner

4 Four Corner

L421A, L421B,

L422A, L422B

Rubycon/

Panasonic

Rubycon/

Panasonic

KwangSung

8/29 Doc ID 018691 Rev 1

AN3383 Test results

2 Test results

All the results and graphs are from measures using equipment from Audio Precision.

Figure 6. Efficiency (2 channels, BTL configuration), V

+1

+0.9

+0.8

+0.7

+0.6

+0.5

+0.4

+0.3

+0.2

+0.1

+0

5 5510 15 20 25 30 35 40 45 50

W

= 26 V, RL = 6 ohm

CC

AM045235v1

Doc ID 018691 Rev 1 9/29