AN4015
Application note
Dual-BTL class-D audio amplifier demonstration board
based on the TDA7498E
Introduction
The purpose of this application note is to describe:
■
■
■
how to connect the TDA7498 demonstration board
how to evaluate the performance of the demonstration board using the electrical curves
how to avoid critical issues in the PCB schematic and layout of the TDA7498E
The TDA7498E represents a new generation of analog input class-D devices from
STMicroelectronics and is housed in a PSSO36 package. It is able to deliver 160 W +160 W
in stereo configuration with V
CC
= 36 V and a 4
Ω
load
(a)
.
Figure 1.
TDA7498E demonstration board
a. All of the results and graphs included in this document are measured using Audio Precision equipment.
January 2012
Doc ID 022507 Rev 1
1/22
www.st.com
Contents
AN4015
Contents
1
2
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Test conditions and connections of the demonstration board . . . . . . . 5
2.1
2.2
2.3
Power supply and interface connection . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Output configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3
4
5
6
Schematic diagram and PCB layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Test curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Design guidelines for PCB schematic and layout . . . . . . . . . . . . . . . . 14
6.1
Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.1.1
6.1.2
6.1.3
Main driver for the selection of components . . . . . . . . . . . . . . . . . . . . . 14
Decoupling capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Output filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.2
Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2/22
Doc ID 022507 Rev 1
AN4015
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
TDA7498E demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
TDA7498E demonstration board connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
TDA7498E schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
PCB layout - top side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
PCB layout - bottom side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
PCB layout - top and bottom sides plus components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
THD+N vs. power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
THD+N vs. frequency (ref = 1 W at 1 kHz) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
DNR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
FFT (0 dBr at 1 W) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Crosstalk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Linearity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Pout vs. V
CC
and THD level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Snubber filter - solution 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Snubber filter - solution 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Dumping network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Frequency shift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Decoupling capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Snubber network. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
V
CC
decoupling electrolytic capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
ROSC - component placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Filter capacitors for SVR, VREF, SVCC, VSS and VDDPW. . . . . . . . . . . . . . . . . . . . . . . . 19
Input signal routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Signal ground and power ground routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Doc ID 022507 Rev 1
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Overview
AN4015
1
Overview
The following terms used in this application note are defined as follows:
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THD+N vs. Pout: Total Harmonic Distortion (THD) plus noise versus output power
THD+N vs. Freq: Total Harmonic Distortion plus noise versus frequency curve
S/N Ratio: Signal-to-noise ratio
DNR: Dynamic range
FFT: Fast Fourier Transform Algorithm (method)
XTalk: Channel separation L to R, or R to L channel crosstalk
Audio Precision 2722A + AES-17 filter + DCX+ AUX-0025 filter
DC power supply
Digital oscilloscope (Tektronix TDS5054B)
Differential voltage probe (LeCroy AP031)
Current probe (Tektronix TCP300)
TDA7498E datasheet
Schematic diagram
PCB layout
Test curves
The equipment used includes the following:
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Reference documents include:
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Doc ID 022507 Rev 1
AN4015
Test conditions and connections of the demonstration board
2
Test conditions and connections of the
demonstration board
Power supply and interface connection
1.
2.
Connect PSU to the V
CC
terminal block
Connect the analog input cable to the RCA connectors on the demonstration board, the
other side must be connected to a signal source such as the Audio Precision analog
outputs or a DVD player
2.1
2.2
Output configuration
The TDA7498E demonstration board has been configured in 2-channel BTL output.
2.3
Connections
The board terminals (top view of demonstration board) are visible in
Figure 2.
Figure 2.
TDA7498E demonstration board connections
Left Load
Right Load
Gain selection
Single-ended
input/differential
input mode
selection
Analog input
Standby and mute
controls
Doc ID 022507 Rev 1
5/22
PCB设计
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