AN2465 Application note
TS4956 stereo audio amplifier system with I2C bus interface evaluation board user guidelines
Introduction
This application note describes the DEMO TS4956 evaluation board, designed for evaluation of the TS4956 stereo audio amplifier. The evaluation board allows the TS4956 amplifier to be driven directly via the I2C bus or by a PC connected to the evaluation board over an RS232 interface. In this document, you will find:
A brief description of the TS4956 stereo audio amplifier system, A description of the evaluation board, A list of the evaluation board components, The layout of the evaluation board, Information on how to configure the evaluation board using the software. You can download the software TS4956.exe from www.st.com/audioamps.
About the TS4956
The TS4956 is a complete audio system device with three dedicated outputs, one stereo headphone, one loudspeaker drive and one mono line for a hands-free set. The stereo headphone is capable of delivering more than 25 mW per channel of continuous average power into 16 single-ended loads with 0.3% THD+N from a 5 V power supply. The device functions are controlled via an I²C bus, which minimizes the number of external components needed. The overall gain and the various output modes of the TS4956 are controlled digitally by the control registers which are programmed via the I²C interface. It also features an internal thermal shutdown. The TS4956 key features are:
Stereo audio amplifier system with I2C bus interface Operating range from VCC = 2.7 V to 5.5 V I2C bus control interface 38 mW output power @ VCC = 3.3 V, THD = 1%, F = 1 kHz, with 16 load Ultra-low consumption in standby mode: 0.5 A 32-step digital volume control ranging from +12 dB to -34.5 dB Stereo loudspeaker option by I2C 8 different output mode selections Pop & click reduction circuitry Lead-free flip-chip package, 18 bumps with 300 m diameter Output power limitation on headphone for eardrum damage consideration
November 2006
Rev 2
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www.st.com
Contents
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Contents
1 2 3 4 5 Typical application schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Description of the evaluation board . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Evaluation board connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Evaluation board layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 TS4956 command software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Connecting the hardware, and starting the software . . . . . . . . . . . . . . . . . . . . . . 12 Configuring the evaluation board using the software interface . . . . . . . . . . . . . . . 13
6
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
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Typical application schematics
1
Typical application schematics
Figure 1 on page 4 and Figure 2. on page 5 show typical application schematics for the TS4956 amplifier with different configurations and different modes. The eight possible output modes are defined in Table 1. Table 1. Output mode selection: Gain from -34.5 dB to + 12 dB (by steps of 1.5 dB)
RHP SD SD SD GX (MIP + MIN) G x RIN SD SD BTL: G x RIN LHP SD SD SD GX (MIP + MIN) G x LIN SD SD BTL: G x RIN Speaker P/N SD GX (MIP + MIN) GX (RIN + LIN) SD SD SD SD G x LIN Mono L/O SD SD SD SD SD GX (MIP + MIN) GX (RIN + LIN) SD
Output mode # 0 1 2 3 4 5 6 7
Where: SD = shutdown mode G = audio gain MIP = mono input positive MIN = mono input negative RIN = stereo input right LIN = stereo input left For complete information about the TS4956, refer to the datasheet.
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Typical application schematics Figure 1. Typical application for the TS4956 (mode 1, 2, 3, 4, 5, 6)
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Vcc
Cs 1 1 F
Cs 2 100nF
C5
T S4956
D iff. input +
Cin1 A1 + 330nF
Vcc
Vcc
C3
+
LHP Amplifier
MO DE 3: Gx(MIP+MIN) MO DE 4: GxLIN
M IP
Stereo Input Left
PHG Amplifier
LHP
B6
16 /3 2 Ohms
Cin2 A2
M IN
D iff. input -
+ 330nF
Stereo Input Right
RH P Amplifier
PHG
A7
MO DE 3: Gx(MIP+MIN) MO DE 4: GxRIN
SE input left
M ode
Cin3 + 330nF B4
R HP
Speaker Amplifier
D6
16 /3 2 Ohms
Select L IN Stereo Input Left
B2
M ODE1: Gx(MIP+MIN) M ODE2: Gx(LIN+RIN)
8 Ohms
SRP+ SRN MLO Amplifier D2
SE input right
Cin4 + 330nF
A5
R IN
Stereo Input Right
M ODE5: Gx(MIP+MIN) M ODE6: Gx(LIN + RIN)
E7 Cout+ 220F
MLO
R1 1k
16 /3 2 Ohms
Bias
I2 C SDA SCL
D igital volume control GN D GN D
3 C7
B YP AS S
D4
Vcc - I2C
E3
E1
E5
+
Cb
Vcc - I2C SCL
1F SDA
I2C BUS
1
2
C1
4
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AN2465 Figure 2.
Typical application schematics Typical application for the TS4956 (mode 7)
V cc
Cs 1 1 F
Cs 2 100nF
C5
T S4956
Stereo Input Left
Vcc
Vcc
C3
LHP Amplifier A1
M IP
+
LHP
B6
PHG Amplifier A2
MODE7: BTL - GxRIN PHG
A7
M IN
Stereo Input Right
RH P Amplifier
8 Ohms
SE input left
Mode
Cin3 + 330nF B4
R HP
Speaker Amplifier
D6
Select L IN Stereo Input Left
B2
MODE7: GxLIN
SRP+ SRN MLO Amplifier D2
SE input right
Cin4 + 330nF
A5
R IN
Stereo Input Right
8 Ohms
M LO
E7
Bias
I2 C SDA SCL
D igital volume con trol GN D GN D
3 C7
BY P AS S
D4
Vcc - I2C
E3
E1
E5
+
Cb
Vcc - I2C SCL
1F SDA
I2C BUS
1
2
C1
4
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Description of the evaluation board
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2
Description of the evaluation board
The evaluation board is divided into two parts. One part includes a typical application for the TS4956 and provides connectors for stereo headphones with a load of 16/32. The other part allows you to evaluate I2C bus control of the TS4956 using a PC. These two parts are opto-separated in order to obtain better suppression of noise caused by the PC power supply. With this evaluation board you can use the TS4956 amplifier in most typical applications with typical external components. You can also use the on-board I2C circuit or external I2C controller to control the TS4956 amplifier (see Section 3: Evaluation board connectors on page 9). For I2C control, the VCC-I2C voltage needs to be applied to the I2C VCC pin of the TS4956 and to the on-board I2C circuit. There are two ways of supplying this input:
One solution is to use the VCC voltage of the amplifier by shorting pins 1 and 2 of connector Cn4 using a jumper. Note that in this case the supply current is higher than the TS4956 supply current itself due to additional current flowing through the on-board I2C circuit. The second solution is to use an external power supply connected to connector Cn4 to supply the I2C VCC input. In this case, the current that supplies the analog part of the evaluation board is equal to the supply current of the TTS4956 itself. (See Section 3: Evaluation board connectors on page 9).
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AN2465 Figure 3.
Description of the evaluation board Schematic diagram of the evaluation board
V cc-I 2C
Vcc Cn4
Vcc
I2C SUPPLY
1 2 3
Cn1
TS4956 POWER SUPPLY
Cs 1 1 F Cs 2 1 00nF +
U1
17
TS4956
D iff. input +
Cin1 JP 1 4 3 2 1 + 330nF 7
Vcc
Vcc
LHP Ampli fier
M IP
Ste reo Input Left
PHG Amplifier
8
L HP
1 P HONE JACK STEREO 1 JP6
Cin2 5
M IN
D iff. input -
+ 330nF
Ste reo Input Right
RH P Amplifier
PH G
2
1 2 3
2 3 J2
M ode SE input left
Cin3 1 2 JP 2 Cin4 1 2 JP 3 3 + 330nF 4 + 330nF
R HP
Spe aker Amplifier
15
Se lect L IN Ste reo Input Left
6 JP4 1 2 10 Cou t + 220 F R7 1K
SR P+ SR NML O Amplifier
R IN
Ste reo Input Right
JP5 1 2
M LO
16
SE input right
Bia s
I2 C SD A SC L
D igital volume con trol GN D GN D
Vcc-I 2C 18 V cc-I 2C R5 10K
B YPAS S
13
Vcc - I2C
12
11
+
Cbypas s 1F
V cc-I 2C
Cn2
14
Cn3
9
R6 10 K
V cc-I 2C
SCL R4 18 0R SDA 16 15 J1 5 9 4 8 3 7 2 6 1 DB9 R1 2k2 R3 1K D2 5 1 N4148 6 K P1040 G ND2 G ND2 U2C G ND DT R TX D RT S DSR GND2 R2 1K D1 3 1 N4148 4 K P1040 U2B KP1040 U2A 1 T1 2 SCL
SDA
S CL
SDA
I2C BUS
SDA
14 13
12 11
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Description of the evaluation board Table 2. Evaluation board bill of materials
Quantity 1 1 2 1 4 1 1 3 1 2 1 1 3 2 1 3 1 1 4 1 Description TS4956 flip-chip to DIP16 adapter KP1040 photo coupler 1F/50V, electrolytic capacitor 100nF/63V, ceramic capacitor 330nF/63V, ceramic capacitors 220F/10V, electrolytic capacitor 2k2, 0.6W 1% resistor 1k, 0.6W 1% resistor 180R, 0.6W 1% resistor 10k, 0.6W 1% resistor Dsub 9 pins socket (female) 3.5mm stereo headphone jack Jumper, 2.54mm pitch Diode 1N4148 N-channel MOSFET transistor, BS170 2 pins header 2.54mm pitch 3 pins header 2.54mm pitch 4 pins header 2.54mm pitch 2 pins header 2.54mm pitch 3 pins header 2.54mm pitch
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Designation U1 U2 Cbypass, Cs1 Cs2 Cin1, Cin2, Cin3, Cin4 Cout R1 R2, R3, R7 R4 R5, R6 J1 J2 --D1, D2 T1 Cn1, Cn2, Cn3 Cn4 JP1 JP2, JP3, JP4, JP5 JP6
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Evaluation board connectors
3
Evaluation board connectors
Caution: When you apply the power supply through Cn1 and Cn4, DO NOT invert the polarity because it would destroy the amplifier at U1.
Connectors Cn1 Description Power connector for analog part of VCC. Power supply voltage from 2.7 V to 5.5 V. When pins of Cn2 and Cn3 are shorted by jumpers, the TS4956 can be driven by onboard I2C circuits or from a PC. When pins of Cn2 and Cn3 are disconnected, the TS4956 can be driven by an external I2C interface over Cn2 and Cn3 pins. The Cn4 connector must be supplied by VCC-I2C voltage in both cases. Connector for VCC-I2C power supply. Possible configuration settings: 1 2 3 pins 2 and 3 are shorted, VCC-I2C is grounded and the TS4956 is in total
`
Cn2, Cn3
shutdown with ultra low current consumption. Cn4
`
1
2
3
pins 1 and 2 are shorted, VCC-I2C is supplied by VCC of the TS4956.
After removing a jumper, the VCC-I2C can be supplied by an external voltage: Pin 2 of Cn4 is connected to an external VCC-I2C supply (positive node) And pin 3 of Cn4 is connected to the ground pin (negative node) of the VCC-I2C supply. In this case, ensure the condition 2.7 V VCC-I2C VCC is respected for proper operation. RS232 connector (DSR, TRS, TXD, DTR, GND2). Stereo jack for connecting stereo headphones 16/32 (LHP, RHP, PHG) Input signal connector (MIP, MIN, GND). Input signal connector (LIN, GND). Input signal connector (RIN, GND). Output signal connector (SRP, SRN). Output signal connector (MLO, GND). Output signal connector (LHP, RHP, PHG).
J1 J2 JP1 JP2 JP3 JP4 JP5 JP6
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Evaluation board connectors Figure 4. TS4956 flip-chip adapter pinout
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Figure 5.
TS4956 DEMO BOARD top view
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Evaluation board layout
4
Evaluation board layout
The following schematics show the various layers and the top view of the evaluation board.
Figure 6.
PCB top layer
Figure 7.
PCB bottom layer
Figure 8.
Top view of evaluation board
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TS4956 command software
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5
TS4956 command software
The TS4956 command software provides a quick and easy way of driving the TS4956 audio system from a PC, and in particular of configuring the output mode and the volume. The software is available for download from the www.st.com/audioamps web site. It runs under MS Windows 95/98/ME/2000/XP.
Connecting the hardware, and starting the software
To drive the TS4956 from a PC, follow these steps: 1. 2. 3. Connect the PC to the TS4956 evaluation board with the RS232 cord. Connect the power supply VCC to Cn1, set jumper on Cn4 to short pins 1 and 2 or connect the external VCC-I2C supply to Cn4 to supply the I2C part externally. Launch the TS4956.exe program downloaded from the st.com web site. The software dialog box shown in Figure 9 is displayed. Figure 9. Command software view
4.
Choose the appropriate COM port from the pop-up menu in the COM Port box or click Auto Select for the program to select the COM port automatically. When the green LED diode in the COM Port box lights up, the program is ready to send commands to the TS4956.
Note:
The COM port where the device is connected must be in the range from COM1 to COM4. If this is not the case, change the COM port number in Windows by selecting Start>Control Panel>System>Hardware>Device Manager.
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TS4956 command software
Configuring the evaluation board using the software interface
There are two options that can be configured using the software interface:
Volume: Changes the gain in the range from -34.5dB to +12 dB by steps of 1.5dB. Mode select: Allows you to select the TS4956 output mode. The schema in the Mode Select box summarizes the mode currently selected and shows which inputs and outputs are active.
These options are illustrated in the command software view in Figure 9. Note: Occasionally, problems may arise when trying to drive the evaluation board using certain notebook or laptop PCs and the RS232 output.
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Revision history
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6
Revision history
Table 3.
Date 14-Nov-2006
Document revision history
Revision 2 First public release. Changes
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