AN2514 Application note
TS4997 2x1W stereo fully differential audio power amplifier with 3D effect enhancement- Evaluation board user guidelines
Introduction
This application note concerns the evaluation board DEMO TS4997, designed to evaluate the TS4997 stereo differential audio amplifier with 3D effect enhancement. In this document, you will find:
a brief description of the TS4997 differential stereo audio amplifier, a description of evaluation board and all of its components, the layout of the evaluation board.
About the TS4997
The TS4997 is designed for top-class stereo audio applications. Thanks to its compact and power-dissipation efficient QFN16 package with exposed pad, it suits a variety of applications. With a BTL configuration, this audio power amplifier is capable of delivering 1W per channel of continuous RMS output power into an 8 load @ 5V. 3D effects enhancement is programmed through a two digital input pin interface that allows more flexibility on each output audio sound channel. Each output channel (left and right), also has its own external controlled standby mode pin to reduce the supply current to less than 10nA per channel. The device also features an internal thermal shutdown protection. The gain of each channel can be configured by external gain setting resistors. Key features of the TS4997 include:
Operating range from VCC= 2.7V to 5.5V 1W output power per channel @ VCC=5V, THD+N=1%, RL=8 Ultra low standby consumption: 10nA typ. 80dB PSRR @ 217Hz with grounded inputs High SNR: 106dB(A) typ. Fast startup time: 45ms typ. Pop&click-free circuit Dedicated standby pin per channel Lead-free QFN16 4x4mm package
Figure 1 on page 2 shows a typical application for the TS4997 amplifier. For complete information about the TS4997, refer to the datasheet.
March 2007
Rev 1
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www.st.com
Description of the evaluation board
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Description of the evaluation board
You can evaluate the amplifier in a typical application configuration. Using the board, you can:
put each channel of the amplifier in standby/operating mode, set the level of 3D effect.
Figure 1.
Typical application of the TS4997 audio amplifier with gain of +6dB set by input resistors
VCC
3D0 Control
3D1 Control
Cs 1uF
16
15
TS4997 - QFN16
Dif f. input LP1 330nF 25k 1 Cin2 P2 2 Dif f. input L+ 330nF 25k
LI N+ LI N-
Cin1
Rin1
3D 0 3D 1
13
Vcc
Opt ional
LEFT
LOU T -
12
Left Speaker
Rin2
3D EFF EC T
RI GH T
+ +
LOU T +
11
8 Ohms
Dif f. input RP3
Cin3
Rin3
4
R IN -
R OUT-
9
Right Speaker
330nF
25k 3
R IN +
R OUT+
10
8 Ohms
Cin4 P4
Rin4
Bypa ss
Dif f. input R+
330nF
25k 14 BIAS
STBYL
STB Y
STBYR
GN D
GN D
5
6
8
1uF Cb
STB YL Control
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S TB Y R Control
7
AN2514 Table 1. External component descriptions
Description of the evaluation board
Components RIN
Functional description Input resistors that set the closed loop gain in conjunction with a fixed internal feedback resistor (Gain = Rfeed/RIN, where Rfeed = 50k). Input coupling capacitors that block the DC voltage at the amplifier input terminal. Thanks to common mode feedback, these input capacitors are optional. However, if they are added, they form with RIN a 1st order high pass filter with -3dB cut-off frequency (fcut-off = 1 / (2 x x RIN x CIN)). Supply bypass capacitors that provide power supply filtering. Bypass pin capacitor that provides half supply filtering.
CIN
CS CB
3D effect enhancement
The TS4997 features 3D audio effects that can be programmed at three discrete levels (LOW, MEDIUM, HIGH) through input pins 3D1 and 3D0 which provide a digital interface. The correspondence between the logic levels of this interface and 3D effect levels are shown in Table 2. The 3D audio effect applied to stereo audio signals evokes perception of spatial hearing and improves this effect in cases where the stereo speakers are too close to each other, such as in small handheld devices, or mobile equipment. The perceived amount of 3D effect is also dependent on many factors such as speaker position, distance between speakers and listener, frequency spectrum of audio signal, or difference of signal between left and right channel. In some cases, the volume can increase when switching on the 3D effect. This factor is dependent on the composition of the stereo audio signal and its frequency spectrum. Table 2. 3D effect settings
3D effect level OFF LOW MEDIUM HIGH 3D0 0 0 1 1 3D1 0 1 0 1
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Description of the evaluation board Figure 2. Evaluation board schematic diagram and components
AN2514
V CC
VCC
VCC
Cn1
1 2 3
Cn8
1 2 3
Cn10
Cs 1 1u F
Cs 2 100nF Cn5
JP1 4 3 2 1
Cin1
16
15
3D 0
Rin2 24 k 1
LI N-
3D 1
330nF Cin2
24 k
TS4997 - QFN16
13
Vcc
Rin1
330nF
LEFT
LOU T-
12
2 Cn2 Cn3 4
LI N+
3D EFF EC T
RI GH T
+ +
LOU T+
11
Cn6
R IN -
R OUT -
9
3 JP2 4 3 2 1 Cin3 Rin3 24 k Rin4 24 k 14
R IN +
R OUT +
10 Cn7
330nF Cin4
Bypa ss
BIA S
ST BYL
STBY
ST BYR
330nF
GN D
GN D
5
6
8
Cn4
1 uF Cbypass1
VCC
7 VCC
3 2 1
Cn9
3 2 1
Cn11
Table 3.
Evaluation board bill of materials
Quantity 1 4 2 1 4 4 7 4 2 Description TS4997 differential stereo audio amplifier (QFN16 package) R330nF/10V, ceramic capacitor 0603 1F/50V, electrolytic capacitor 100nF/10V, ceramic capacitor Jumper, 2.54mm pitch (placed on Cn8, Cn9, Cn10 and Cn11 connectors) Resistor 24k, 1/4W, 1%, 0603 2 pins header, 2.54mm pitch 3 pins header, 2.54mm pitch 3 pins header, 2.54mm pitch
Designation U1 Cin1 to Cin4 Cb, Cs1 Cs2 --R1 to R4 Cn1 to Cn7 Cn8 to Cn11 JP1, JP2
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Evaluation board connectors
2
Evaluation board connectors
Table 4.
.
Evaluation board connectors
Description Connector used to short-circuit input capacitor Cin1 by placing a jumper on it when the amplifier is used with common mode feedback input. Connector used to short-circuit input capacitor Cin2 by placing a jumper on it when the amplifier is used with common mode feedback input. Connector used to short-circuit input capacitor Cin3 by placing a jumper on it when the amplifier is used with common mode feedback input. Connector used to short-circuit input capacitor Cin4 by placing a jumper on it when the amplifier is used with common mode feedback input. Power connector (VCC, GND). Power supply voltage from 2.7V to 5.5V. Left channel output signal connector (Lout+, Lout-). Right channel output signal connector (Rout+, Rout-). 3D0 pin control connector (VCC, 3D0, GND). Together with connector Cn10, allows you to select the level of 3D effect. Left channel standby control connector (VCC, STBYL, GND). 3D1 pin control connector (VCC, 3D1, GND). Together with connector Cn8, allows you to select the level of 3D effect. Right channel standby control connector (VCC, STBYR, GND). Left channel input signal connector (GND, Lin-, Lin+, GND). Right channel input signal connector (GND, Rin-, Rin+, GND).
Connectors Cn1 Cn2 Cn3 Cn4 Cn5 Cn6 Cn7 Cn8 Cn9 Cn10 Cn11 JP1 JP2
Caution:
When you apply the power supply through Cn5, do not invert the polarity because it would destroy the amplifier at U1.
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Configuring the evaluation board characteristics
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Configuring the evaluation board characteristics
Differential gain
The value of the differential gain of each amplifier is dependent on the values of external input resistors RIN1 to RIN4 and of integrated feedback resistors with fixed value.
AV
diff
Rf e e d = ------------- = 5------------0 k RI N RI N
where RIN = RIN1 = RIN2 = RIN3 = RIN4 expressed in k and Rfeed = 50k (value of internal feedback resistors). Because the input resistors values on the evaluation board are RIN1=RIN =RIN3=RIN4=24k, the differential gain is set to ~6dB. If necessary, the differential gain can be adapted by modifying the values of resistors RIN1 to RIN4.
Input configuration
On the demo board, by placing or removing jumpers on connectors Cn1, Cn2, Cn3 and Cn4 you can elasily change the input configuration. You can select either capacitor-coupled or common-mode feedback. In the capacitor-coupled configuration, the -3dB cut-off frequency in Hz is:
1 F C L = ---------------------------------------------- ( H z ) 2 × × RI N × CI N
with RIN = RIN1 = RIN2 = RIN3 = RIN4 expressed in and CIN = CIN1 = CIN2 = CIN3 = CIN4 expressed in F. More information about component calculations is available in the TS4997 datasheet.
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Evaluation board layout
4
Evaluation board layout
The following schematics show the layers and the top view of the evaluation board.
Figure 3.
PCB top layer
Figure 4.
PCB bottom layer
Figure 5.
Top view of evaluation board
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