Texas Instruments Stereo Amplifier SLOU025 User Manual

User’s Guide  
1998  
Mixed-Signal Products  
SLOU025  
 
Preface  
Related Documentation From Texas Instruments  
TI Plug-N-Play Audio Amplifier Evaluation Platform (literature  
number SLOU011) provides detailed information on the evaluation  
platform and its use with TI audio evaluation modules.  
TPA122 150-mW STEREO AUDIO POWER AMPLIFIER  
(literature number SLOS211) This is the data sheet for the TPA122  
audio amplifier integrated circuit.  
FCC Warning  
This equipment is intended for use in a laboratory test environment only. It  
generates, uses, and can radiate radio frequency energy and has not been  
tested for compliance with the limits of computing devices pursuant to subpart  
J of part 15 of FCC rules, which are designed to provide reasonable protection  
against radio frequency interference. Operation of this equipment in other  
environments may cause interference with radio communications, in which  
case the user at his own expense will be required to take whatever measures  
may be required to correct this interference.  
Trademarks  
TI is a trademark of Texas Instruments Incorporated.  
iii  
 
iv  
 
Contents  
1
2
3
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1  
1.1  
1.2  
1.3  
Feature Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2  
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3  
TPA122 MSOP EVM Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3  
Quick Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1  
2.1  
2.2  
2.3  
Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2  
Quick Start List for Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3  
Quick Start List for Stand-Alone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4  
Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1  
3.1  
3.2  
Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2  
The TPA122 MSOP Audio Amplifier Evaluation Module . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3  
3.2.1 TPA122 Audio Amplifier IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4  
3.2.2 Module Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5  
3.2.3 Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5  
Using The TPA122 MSOP EVM With The Plug-N-Play Evaluation Platform . . . . . . . . . 3-6  
3.3.1 Installing and Removing EVM Boards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6  
3.3.2 Signal Routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7  
3.3.3 Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8  
3.3.4 Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9  
3.3.5 Inputs and Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10  
Using The TPA122 MSOP EVM Stand-Alone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11  
3.4.1 TPA122 MSOP EVM Connected as a Stereo Headphone Amplifier . . . . . . . 3-11  
TPA122 MSOP Audio Amplifier Evaluation Module Parts List . . . . . . . . . . . . . . . . . . . . 3-12  
3.3  
3.4  
3.5  
v
 
Figures  
1–1  
2–1  
2–2  
3–1  
3–2  
3–3  
3–4  
3–5  
3–6  
3–7  
3–8  
The TI TPA122 MSOP Audio Amplifier Evaluation Module . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4  
Quick Start Platform Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2  
Quick Start Module Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4  
The TI Plug-N-Play Audio Amplifier Evaluation Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2  
TPA122 MSOP EVM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3  
TPA122 MSOP EVM Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3  
TPA122 Audio Amplifier IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4  
Platform Signal Routing and Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7  
Mute Polarity Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8  
Typical Headphone Plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10  
TPA122 MSOP EVM Connected as a Stereo Headphone Amplifier . . . . . . . . . . . . . . . . . 3-11  
Tables  
2–1  
Typical TI Plug-N-Play Platform Jumper and Switch Settings for the  
TPA122 MSOP EVM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1  
Platform Jumper and Switch Settings for the TPA122 MSOP EVM . . . . . . . . . . . . . . . . . . . 2-3  
TPA122 MSOP EVM Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12  
2–2  
3–1  
vi  
 
Chapter 1  
Introduction  
This chapter provides an overview of the Texas Instruments (TI ) TPA122  
MSOPAudio Amplifier Evaluation Module (SLOP125). It includes a list of EVM  
features, a brief description of the module illustrated with a pictorial diagram,  
and a list of EVM specifications.  
Topic  
Page  
1.1 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–2  
1.2 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–3  
1.3 TPA122 MSOP EVM Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–3  
1-1  
 
Features  
1.1 Features  
The TI TPA122 MSOP Audio Amplifier Evaluation Module and the TI  
Plug-N-Play Audio Amplifier Evaluation Platform include the following  
features:  
TPA122 MSOP Stereo Audio Power Amplifier Evaluation Module  
Dual channel, single-ended operation  
150-mW output power into 8 at 5 V  
2.5-V to 5.5-V operation  
Very low distortion — THD+N is less than 0.006% @ 1 kHz and less  
than 0.07% from 20 Hz to 20 kHz into 10-kloads; less than 0.02% @  
1 kHz and less than 0.4% from 20 Hz to 20 kHz into 32-loads; and  
less than 0.05% @ 1 kHz and less than 0.8% from 20 Hz to 20 kHz into  
8-loads  
Extremely low current consumption in shutdown mode  
Internal thermal and short-circuit protection  
Internal pop reduction circuitry  
Quick and Easy Configuration with the TI Plug-N-Play Audio Amplifier  
Evaluation Platform  
Evaluation module is designed to simply plug into the platform,  
automatically making all signal, control, and power connections  
Platform provides flexible power options  
Jumpers on the platform select power and module control options  
Switches on the platform route signals  
Platform provides quick and easy audio input and output connections  
Platform Power Options  
Onboard 9-V battery  
External 5-V – 15-V (V ) supply inputs  
CC  
External regulated V  
supply input  
DD  
Socket for on-board 5-V V  
voltage regulator EVM  
DD  
On-board overvoltage and reverse polarity power protection  
Platform Audio Input and Output Connections  
Left and right RCA phono jack inputs  
Miniature stereo phone jack input  
Left and right RCA phono jack outputs  
Left and right compression speaker terminal outputs  
Miniature stereo headphone jack output  
1-2  
Introduction  
 
Description  
1.2 Description  
The TPA122 MSOP Audio Power Amplifier Evaluation Module is a complete,  
low-power stereo audio power amplifier for high-fidelity line-level output,  
headphone, and small speaker applications. It consists of the TI TPA122  
150-mW Stereo Audio Power Amplifier IC in a very small MSOP package,  
along with a small number of other parts mounted on a circuit board that is  
approximately one and a quarter inches square (Figure 1–1).  
Figure 1–1. The TI TPA122 Audio Amplifier Evaluation Module  
Shutdown  
VDD  
GND  
+
S1  
R1  
C5  
R3  
IN1  
R2  
GND  
C1  
Vo1  
GND  
U1  
C2  
TEXAS  
INSTRUMENTS  
C4  
C3  
R5  
R4  
GND  
Vo2  
IN2  
SLOP127  
GND  
TPA122 MSOP EVM  
Due to the very small size of the MSOP IC package, the standard part number TPA122 is replaced with the code TIAAE  
Single in-line header pins are mounted to the underside of the module circuit  
board to allow the EVM to be plugged into the TI Plug-N-Play Audio Amplifier  
Evaluation Platform, or to be wired directly into existing circuits and equipment  
when used stand-alone.  
The platform has room for a single TPA122 evaluation module. It is a  
convenient vehicle for demonstrating TI’s audio power amplifier and related  
evaluation modules. The EVMs simply plug into the platform, which  
automatically provides power to the modules, interconnects them correctly,  
andconnectsthemtoaversatilearrayofstandardaudioinputandoutputjacks  
and connectors. Easy-to-use configuration controls allow the platform and  
EVMs to quickly model many possible end-equipment configurations.  
There is nothing to build, nothing to solder, and nothing but the speakers  
included with the platform to “hook up.”  
1.3 TPA122 MSOP EVM Specifications  
Supply voltage range, V  
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 V to 5.5 V  
DD  
Supply current, I  
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 mA, max  
DD  
Continuous output power, P : 8 , V =5 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 mW  
O
DD  
Audio input voltage, V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V  
+ 0.3 Vpp, max  
I
DD  
Minimum load impedance, R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Ω  
L
1-3  
Introduction  
 
1-4  
Introduction  
 
Chapter 2  
Quick Start  
ThestepsinthischaptercanbefollowedtoquicklypreparetheTPA122MSOP  
audio amplifier EVM for use. Using the TPA122 MSOP EVM with the TI  
Plug-N-Play Audio Amplifier Evaluation Platform is a quick and easy way to  
connect power, signal and control inputs, and signal outputs to the EVM using  
standard connectors. However, the audio amplifier evaluation module can be  
used stand-alone by making connections directly to the module pins, and can  
be wired directly into existing circuits or equipment.  
The platform switch and jumper settings shown in Table 2–1 are typical for the  
TPA122 MSOP EVM and will cause the TPA122 IC to shut down/mute when  
a plug is removed from platform headphone jack J10.  
Table 2–1. Typical TI Plug-N-Play Platform Jumper and Switch Settings for the  
TPA122 MSOP EVM  
EVM  
JP6  
JP7  
JP8  
S2  
S3  
TPA122  
X
Hi  
X
Note 2  
U5  
Notes: 1) X = Don’t care  
2) Set S2 to ON when signal conditioning board is installed in U1; set S2  
to OFF when no signal conditioning board is installed.  
Topic  
Page  
2.1 Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–2  
2.2 Quick Start List for Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–3  
2.3 Quick Start List for Stand-Alone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–4  
2-1  
 
Precautions  
2.1 Precautions  
Power Supply Input Polarity and Maximum Voltage  
Always ensure that the polarity and voltage of the external power  
connected to V  
power input connector J1, J2, and/or V  
power  
CC  
DD  
input connector J6 are correct. Overvoltage or reverse-polarity  
power applied to these terminals can open onboard soldered-in  
fuses and cause other damage to the platform, installed evaluation  
modules, and/or the power source.  
Inserting or Removing EVM Boards  
Do not insert or remove EVM boards with power applied — damage  
to the EVM board, the platform, or both may result.  
Figure 2–1. Quick Start Platform Map  
7b  
6b  
1
10  
6b  
ICC  
JP4  
C1+  
F1  
VR1  
DC  
Power  
In/Out  
6a  
Power  
Input  
6b  
R2  
R1  
Audio  
Power  
Amps  
Signal Conditioning  
Audio  
Input  
8
Speaker  
Output  
Mode  
Mute  
Polarity  
Lo  
****CAUTION****  
Do not insert or remove  
EVM boards with power  
applied  
Hi  
Stereo  
Headphone  
Output  
9
Plug-N-Play Audio Amplifier  
Evaluation Platform  
SLOP097 Rev. C.1  
HP Out  
R3  
R4  
R5  
3
2
4
5
2-2  
Quick Start  
 
Quick Start List for Platform  
2.2 Quick Start List for Platform  
Follow these steps when using the TPA122 MSOP EVM with the TI  
Plug-N-Play Audio Amplifier Evaluation Platform (see the platform user’s  
guide, SLOU011, for additional details). Numbered callouts for selected steps  
are shown in Figure 2–1 and details appear in Chapter 3.  
Platform preparations  
1) EnsurethatallexternalpowersourcesaresettoOFF andthattheplatform  
power switch S1 is set to OFF.  
2) Install a TPA122 MSOP module in platform socket U5, taking care to align  
the module pins correctly.  
3) Use switch S2 to select or bypass the signal conditioning EVM (U1).  
4) Set control signal Polarity jumper JP7 to Hi.  
5) Set Hp source switch S3 to U5 to route the output signal to the headphone  
Jack (J10).  
Table 2–2. Platform Jumper and Switch Settings for the TPA122 MSOP EVM  
EVM  
JP6  
JP7  
JP8  
S2  
S3  
TPA122  
X
Hi  
X
Note 2  
U5  
Notes: 1) X = Don’t care  
2) Set S2 to ON when signal conditioning board is installed in U1; set S2  
to OFF when no signal conditioning board is installed.  
Power supply  
6) Select and connect the power supply:  
a) Connect an external regulated power supply set to a voltage between  
2.5 V and 5.5 V to platform V power input connector J6, taking care  
DD  
to observe marked polarity,  
or  
b) Install a 3-V to 5-V voltage regulator EVM (SLVP097 or equiv.) in  
platform socket U6. Install a 9-V battery in B1 or connect a 7 V – 12  
V power source to a platform V power input J1 or J2 and jumper the  
CC  
appropriate power input (see platform user’s guide).  
Inputs and outputs  
7) Ensure that signal source level is set to minimum.  
8) Connect the audio source to left and right RCA phono jacks J3 and J5 or  
stereo miniature phone jack J4.  
9) Connect 32-headphones to headphone jack J10.  
Power up  
10) Verify correct voltage and input polarity and set the external power supply  
to ON. If V and an onboard regulator EVM are used to provide V , set  
CC  
DD  
platform power switch S1 to ON.  
Platform LED2 should light indicating the presence of V , and the evaluation  
DD  
modules installed on the platform should begin operation.  
11) Adjust the signal source level as needed.  
2-3  
Quick Start  
 
Quick Start List for Stand-Alone  
2.3 Quick Start List for Stand-Alone  
Follow these steps to use the TPA122 MSOP EVM stand-alone or when  
connecting it into existing circuits or equipment. Connections to the TPA122  
MSOP module header pins can be made via individual sockets,  
wire-wrapping, or soldering to the pins, either on the top or the bottom of the  
module circuit board (Figure 2–2). Details appear in Chapter 3.  
Figure 2–2. Quick Start Module Map  
Shutdown  
VDD  
GND  
+
S1  
R1  
C5  
R3  
IN1  
GND  
R2  
C1  
Vo1  
GND  
U1  
C2  
TEXAS  
INSTRUMENTS  
C4  
C3  
R5  
R4  
GND  
Vo2  
IN2  
SLOP127  
GND  
TPA122 MSOP EVM  
Due to the very small size of the MSOP IC package, the standard part number TPA122 is replaced with the code TIAAE  
Power supply  
1) Ensure that all external power sources are set to OFF.  
2) Connect an external regulated power supply set to 5 V to the module VDD  
and GND pins, taking care to observe marked polarity.  
Inputs and outputs  
3) Ensure that the signal source level is set to minimum.  
4) Connect the audio source to the module IN1, IN2, and GND pins, taking  
care to observe marked polarity.  
5) Connect the Shutdown pin to V  
through a Normally Open switch.  
DD  
6) Connect 32-headphones to the module V 1, V 2 pins through 33 µF  
O
O
to 1000 µF output-coupling capacitors (figure 38) and return to the GND  
pin, or  
7) For line output, connections to the V 1 and V 2 pins must be made  
O
O
through 33 µF to 1000 µF output-coupling capacitors and returned to  
GND.  
Power-up  
8) Verify correct voltage and input polarity and set the external power supply  
to ON.  
The EVM should begin operation.  
9) Adjust the signal source level as needed.  
2-4  
Quick Start  
 
Chapter 3  
Details  
This chapter provides details on the TPA122 IC, the evaluation module, the  
steps in the Quick-Start List, additional application information, and a parts list  
for the TPA122 MSOP evaluation module.  
Topic  
Page  
3.1 Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–2  
3.2 The TPA122 MSOP Audio Power Amplifier Evaluation Module . . . . 3–3  
3.3 Using The TPA122 MSOP EVM With The Plug-N-Play  
Evaluation Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–6  
3.4 Using The TPA122 MSOP EVM Stand-Alone . . . . . . . . . . . . . . . . . . . . 3–11  
3.5 TPA122 MSOP Audio Power Amplifier EVM Parts List . . . . . . . . . . 3–12  
3-1  
 
Precautions  
3.1 Precautions  
Power Supply Input Polarity and Maximum Voltage  
Always ensure that the polarity and voltage of the external power  
connected to V  
power input connector J1, J2, and/or V  
power  
CC  
DD  
input connector J6 are correct. Overvoltage or reverse-polarity  
power applied to these terminals can open onboard soldered-in  
fuses and cause other damage to the platform, installed evaluation  
modules, and/or the power source.  
Inserting or Removing EVM Boards  
Do not insert or remove EVM boards with power applied — damage  
to the EVM board, the platform, or both may result.  
Figure 3–1. The TI Plug-N-Play Audio Amplifier Evaluation Platform  
ICC  
JP4  
C1+  
F1  
VR1  
DC  
Power  
In/Out  
Power  
Input  
R2  
R1  
Audio  
Power  
Amps  
Signal Conditioning  
Audio  
Input  
Speaker  
Output  
Mode  
Mute  
Polarity  
Lo  
****CAUTION****  
Do not insert or remove  
EVM boards with power  
applied  
Hi  
Stereo  
Headphone  
Output  
Plug-N-Play Audio Amplifier  
Evaluation Platform  
SLOP097 Rev. C.1  
HP Out  
R3  
R4  
R5  
3-2  
Details  
 
The TPA122 MSOP Audio Power Amplifier Evaluation Module  
3.2 The TPA122 MSOP Audio Power Amplifier Evaluation Module  
The TPA122 MSOP Audio Power Amplifier Evaluation Module is powered by  
a TPA122 150-mW Stereo Audio Amplifier IC. It includes a shutdown control  
signal input with onboard switch and can drive either line-level outputs, 32-Ω  
headphones, or 8-speakers.  
The evaluation module can be used with the TI Plug-N-Play Audio Amplifier  
Evaluation Platform (Figure 31) or wired directly into circuits or equipment.  
The module has single in-line header connector pins mounted to the under  
side of the board. These pins allow the module to be plugged into the TI  
platform, whichautomaticallymakesallthesignalinputandoutput, power, and  
control connections to the module.  
The module connection pins are on 0.1-inch centers to allow easy use with  
standard perf board and plug board-based prototyping systems. Or, the EVM  
can be wired directly into existing circuits and equipment when used  
stand-alone.  
The module appears in Figure 3–2 and its schematic is shown in Figure 33.  
Figure 3–2. TPA122 MSOP EVM  
Shutdown  
VDD  
GND  
+
S1  
R1  
C5  
R3  
IN1  
GND  
R2  
C1  
Vo1  
GND  
U1  
C2  
TEXAS  
INSTRUMENTS  
C4  
C3  
R5  
R4  
GND  
Vo2  
IN2  
SLOP127  
GND  
TPA122 MSOP EVM  
Due to the very small size of the MSOP IC package, the standard part number TPA122 is replaced with the code TIAAE  
Figure 3–3. TPA122 MSOP EVM Schematic Diagram  
Shutdown  
(V  
to  
DD  
Vo1  
R1  
20 k  
Shutdown)  
8
7
1
NO  
V
DD  
Vo1  
V
DD  
S1  
2.5 to 5.5 V  
C4  
1 µF  
+
C5  
10 µF  
R3  
80 kΩ  
V
TPA122  
MSOP  
DD  
2
3
GND  
Audio Input 1  
IN 1  
Vo2  
R2  
20 kΩ  
C1  
1 µF  
Bypass  
6
5
C2  
1 µF  
Vo2  
IN 2  
R5  
80 kΩ  
4
Shutdown  
GND  
C3  
1 µF  
R4  
20 kΩ  
Audio Input 2  
3-3  
Details  
 
The TPA122 MSOP Audio Power Amplifier Evaluation Module  
3.2.1 TPA122 Audio Amplifier IC  
The TPA122 audio amplifier IC is a CMOS device intended primarily for  
high-performance line-level output, headphone driver, and small speaker  
applications. It is supplied in a very small surface-mount MSOP package and  
has been designed to operate from low supply voltages (between  
approximately 2.5 V and 5.5 V) and to deliver up to approximately 150 mW into  
8-speakers with low distortion. As a line-level driver, distortion levels  
(THD+N) are below 0.07% into 10-kloads across the audio band (20 Hz to  
20 kHz). As a headphone driver, distortion levels are below 0.4% into 32-Ω  
loads across the audio band. And as a speaker driver, distortion levels are  
below 0.8% into 8-loads across the audio band. Typical applications include  
portable computers, desktop computers, personal audio, toys, games, and  
similar audio applications.  
The IC includes two separate internal amplifiers, depop circuitry, and a  
common shutdown control (Figure 34). The load for each channel is  
connected between the V pin and GND through a coupling capacitor. For  
O
more information, see the TPA122 amplifier IC data sheet, TI Literature  
Number SLOS211.  
Figure 3–4. TPA122 Amplifier IC  
8
V
DD  
R
F
C
Stereo Audio  
Input  
S
R
I
C
IN1  
2
3
C
V
O
1
R
1
4
Bypass  
C
+
I
C
B
R
R
L
From System  
Control  
Shutdown  
IN2  
Bias  
Control  
5
6
L
Stereo  
R
I
C
C
V 2  
O
L
7
C
I
+
R
F
3-4  
Details  
 
The TPA122 MSOP Audio Power Amplifier Evaluation Module  
3.2.2 Module Gain  
The TPA122 MSOP evaluation module has a set gain of 4 (inverting) for each  
channel. However, the gain can be adjusted to a maximum of approximately  
10 (inverting) by changing the value of feedback resistors (R2 and R4, Figure  
3–3). Use the following equation to determine the value of R  
F:  
RF  
RI  
Gain  
The TPA122 amplifier IC, like most other amplifiers, exhibits its best distortion  
and noise performance at lower gain levels. In addition, higher gain levels  
require a small compensation capacitor to ensure stability (see the TPA122  
data sheet).  
Gain versus total harmonic distortion (THD) and gain versus signal-to-noise  
ratio (SNR) should be considered in each application. Both the module input  
signal level and the TPA122 MSOP module gain should be adjusted to obtain  
the lowest overall distortion level for a particular overall gain. A quick rule of  
thumb (everything else being equal): the module input signal level should be  
as high as possible without clipping or overloading the TPA122 input, and the  
TPA122 gain should be kept as low as possible.  
3.2.3 Shutdown  
When the shutdown terminal of the TPA122 amplifier IC is taken high, the IC  
ceases operation and enters a very low power state (65 µA at V  
= 5 V and  
DD  
10 µA at V  
= 3.3 V Typ). This is accomplished by applying a control signal  
DD  
to the module SD pin or by pressing the Shutdown switch, S1, on the module.  
When the control signal goes low or is removed (or the switch is released),  
amplifier operation resumes.  
The Plug-N-Play platform can generate the mute signal for the module either  
when a plug is inserted into the platform headphone output jack or when the  
plug is removed, as selected by a platform jumper (JP7).  
3-5  
Details  
 
Using The TPA122 MSOP EVM With the Plug-N-Play Evaluation Platform  
3.3 Using The TPA122 MSOP EVM With the Plug-N-Play Evaluation Platform  
The TPA122 MSOP Audio Amplifier Evaluation Module is designed for use  
with the TI Plug-N-Play Audio Amplifier Evaluation Platform. It simply plugs  
into socket U5.  
The following paragraphs provide additional details for using the TPA122EVM  
with the platform.  
3.3.1 Installing and Removing EVM Boards  
TI Plug-N-Play evaluation modules use single-in-line header pins installed on  
the underside of the module circuit board to plug into sockets on the platform.  
The EVM pins and the platform sockets are keyed such that only the correct  
type of EVM can be installed in a particular socket, and then only with the  
proper orientation.  
Evaluation modules are easily removed from the platform by simply prying  
them up and lifting them out of their sockets. Care must be taken, however, to  
prevent bending the pins.  
3.3.1.1 EVM Insertion  
1) Remove all power from the evaluation platform.  
2) Locate socket U5 on the platform.  
3) Orient the module correctly.  
4) Carefully align the pins of the module with the socket pin receptacles.  
5) Gently press the module into place.  
6) Check to be sure that all pins are seated properly and that none are bent  
over.  
3.3.1.2 EVM Removal  
1) Remove all power from the evaluation platform.  
2) Using an appropriate tool as a lever, gently pry up one side of the module  
a short distance.  
3) Change to the opposite side of the module and use the tool to pry that side  
up a short distance.  
4) Alternate between sides, prying the module up a little more each time to  
avoid bending the pins, until it comes loose from the socket.  
5) Lift the EVM off the platform.  
3-6  
Details  
 
Using The TPA122 MSOP EVM With the Plug-N-Play Evaluation Platform  
3.3.2 Signal Routing  
Signal flow on the platform is controlled by two signal routing switches, as  
shown in Figure 35.  
Figure 3–5. Platform Signal Routing and Outputs  
U2 Stereo Power  
Amplifier EVM  
Off  
U3  
+
Mono Power  
Amplifier EVM  
R
R
L
R
J7, J8, J9  
Speaker  
Outputs  
U1  
Signal  
Conditioning  
Audio  
Input  
S2  
U4  
+
L
Mono Power  
Amplifier EVM  
L
On  
U2U4  
R
+
R
U5  
TPA122 MSOP  
Headphone  
Amplifier EVM  
J10  
Headphone  
Output  
GND  
S3  
L
+
L
U5  
3.3.2.1 Signal Conditioning  
The audio signal from the input jacks can be applied to the signal conditioning  
socket (U1) if an EVM is installed there, or socket U1 can be bypassed and the  
audioinputsignalapplieddirectlytotheinputsoftheTPA122poweramplifiers.  
Switch S2 selects or bypasses signal conditioning.  
3.3.2.2 Headphone Output Jack  
Switch S3 is the source select for the stereo headphone output jack, J10. The  
headphone jack is capacitively coupled (via 470 µF electrolytics). It can output  
either the signal from the the TPA122 MSOP headphone amplifier in socket  
U5 or the signal from power amplifiers installed in socket U2 or in sockets U3  
and U4, as determined by the setting of headphone source select switch S3.  
When S3 is set to the headphone amplifier position (U5), the headphone jack  
is connected to the headphone amplifier EVM output lines. When a plug is  
inserted into the jack, signals output through J10 are returned to platform  
ground. A switch inside the headphone jack produces a control signal that can  
be routed to the headphone amplifier socket to shutdown the TPA122 MSOP  
EVM when the headphone plug is removed.  
Switch S3 connects the headphone jack to either the headphone amplifier  
platform socket (U5) or to the platform power amplifier sockets (U2 U4).  
3-7  
Details  
 
Using The TPA122 MSOP EVM With the Plug-N-Play Evaluation Platform  
3.3.3 Shutdown  
The TPA122 MSOP EVM is equipped with a shutdown control input pin. When  
this input is tied to V , the TPA122 amplifier IC on the module ceases  
DD  
operation and enters an ultra-low-power state. When the EVM shutdown  
control input is tied to GND or allowed to float, amplifier operation resumes.  
In typical applications, as often found in notebook computers, portable audio  
products, and such, the internal speakers mute when headphones are  
plugged into the headphone jack, or internal speakers mute when external  
speakers are connected. In applications using separate speaker and  
headphone amplifiers, the one not being used can be muted to conserve  
power.  
3.3.3.1 Headphone Jack Control Signals  
The platform headphone output jack (J10) contains an internal switch that  
changes the state of a pair of control lines when a plug is inserted or removed  
(Figure 36). Each control line is pulled down by a 1-kresistor to ground (R4  
and R5). The switch in the headphone jack pulls one line or the other up to V  
DD  
through a 240 resistor (R3), depending on whether or not a plug is inserted  
in J10.  
Figure 3–6. Shutdown Polarity Control  
V
DD  
R3  
240 Ω  
Polarity  
JP7  
Lo  
U5  
J10  
Headphone  
Jack  
Shutdown  
Headphone  
Amplifier  
Hi  
R4  
R5  
HP  
1 kΩ  
1 kΩ  
(U5)  
3.3.3.2 Shutdown Polarity Select (JP7)  
A 3-pin jumper header (JP7) on the platform selects the shutdown control  
signal polarity by connecting either the active-high or the active-low line from  
the headphone jack to platform socket U5. The TPA122 MSOP EVM shuts  
down when V  
is applied to the module SD pin.  
DD  
To shut down the TPA122 MSOP amplifier module when a plug is  
inserted into the headphone jack, jumper JP7 to Hi.  
To shut down the TPA122 MSOP amplifier module until a plug is  
inserted into the headphone jack, jumper JP7 to Lo (this is the typical  
setting).  
3-8  
Details  
 
Using The TPA122 MSOP EVM With the Plug-N-Play Evaluation Platform  
3.3.4 Power Requirements  
The TPA122 MSOP Audio Power Amplifier Evaluation Module can operate  
from a V voltage between approximately 2.5 V and 5.5 V.  
DD  
The TI Plug-N-Play Audio Amplifier Evaluation Platform with a voltage  
regulator EVM installed on it can provide a regulated 3.3-V or 5-V V supply  
DD  
from a wide variety of unregulated V  
voltage inputs between approximately  
CC  
5.5 V and 12 V, including an onboard 9-V battery. Or, an external regulated  
power source can be used to supply V voltage to the platform and the  
DD  
TPA122 evaluation module installed on it.  
The platform is equipped with overvoltage and reverse-polarity supply voltage  
input protection in the form of fused crowbar circuits.  
V
voltage applied to platform screw terminals J6 MUST NOT exceed  
DD  
the absolute maximum rating for the TPA122 amplifier IC installed on the  
evaluation module (5.5 V), or damage to the IC may result. In no case  
shouldV voltageoftheincorrectpolarityorinexcessof6.1Vbeapplied  
DD  
to screw terminals J6 of the platform, or the power protection circuit on the  
V
line will trip.  
DD  
V
voltage applied to the platform MUST NOT exceed the maximum  
CC  
voltage input specified for the voltage regulator module installed in socket  
U6 (12 V for the SLVP097), or damage to the voltage regulator module  
may result. In no case should V  
voltage applied to the platform exceed  
CC  
15 V, or the overvoltage protection circuit on the V  
bus will trip.  
CC  
3-9  
Details  
 
Using The TPA122 MSOP EVM With the Plug-N-Play Evaluation Platform  
3.3.5 Inputs and Outputs  
The TI Plug-N-Play Audio Amplifier Evaluation Platform is equipped with  
several standard conectors for audio inputs and outputs.  
3.3.5.1 Inputs  
In most cases, audio signals enter the platform through either a pair of RCA  
phono jacks (J3 and J5) or a miniature (1/8) stereo phone jack (J4). Certain  
signal conditioning and amplifier EVMs, however, may have additional signal  
input connectors mounted on the module circuit board.  
The platform audio signal input jacks (J3, J4, and J5) are of the closed-circuit  
type, grounding the signal input lines when no plugs are inserted.  
3.3.5.2 Outputs  
Output signals from the headphone amplifier (U5) leave the platform through  
a miniature (1/8) stereo headphone jack (J10). Amplified audio output signals  
from the power amplifiers (U2 – U4) leave the platform through left and right  
RCA phono jacks (J7 and J9), left and right pairs of compression connectors  
for stripped speaker wires (J8), and optionally, through the headphone jack.  
The audio output lines from the power amplifiers are separate all the way to  
the edge of the platform (output jacks J7, J8, and J9) — the OUT– lines from  
the power amplifier sockets are not tied to each other or to platform ground.  
This allows the power amplifier EVMs to operate in the highly-efficient  
bridge-tied load configuration.  
The headphone jack (J10) is capacitively coupled to source select switch S3,  
which connects J10 to the output lines of either the headphone amplifier  
socket or the power amplifier sockets (Figure 35). When the TPA122 MSOP  
EVM output signal is routed to J10 by S3, signals output via J10 are returned  
to platform ground when a plug is inserted (Figure 37).  
Figure 3–7. Typical Headphone Plug  
Left  
Right  
GND  
3-10  
Details  
 
Using The TPA122 MSOP EVM Stand-Alone  
3.4 Using The TPA122 MSOP EVM Stand-Alone  
Using the TPA122 MSOP Audio Power Amplifier Evaluation Module  
stand-alone is much the same as using it with the platform. The same 2.5-V  
to 5.5-V power supply requirement exists.  
Note that the shutdown signal applied to the EVM SD pin must be able to  
supply enough current to overcome the pulldown resistor on the module  
(20 k).  
3.4.1 TPA122 MSOP EVM Connected as a Stereo Headphone Amplifier  
Figure 3–8. TPA122 MSOP EVM Connected as a Stereo Headphone Amplifier  
5 VDC  
Shutdown  
VDD  
GND  
Shutdown  
NO  
+
S1  
R1  
Audio  
Input  
(Right)  
C5  
IN1  
GND  
R2  
R3  
C1  
Vo1  
+
+
33 µF –  
U1  
GND  
C2  
1000 µF  
TEXAS  
C4  
INSTRUMENTS  
C3  
R5  
33 µF –  
1000 µF  
R4  
GND  
Vo2  
Audio  
Input  
(Left)  
IN2  
SLOP127  
TPA122 MSOP EVM  
GND  
Due to the very small size of the MSOP IC package, the standard part number TPA122 is replaced with the code TIAAE  
3-11  
Details  
 
TPA122 MSOP Audio Power Amplifier Evaluation Module Parts List  
3.5 TPA122 MSOP Audio Power Amplifier Evaluation Module Parts List  
Table 3–1. TPA122 MSOP EVM Parts List  
EVM  
Qty.  
Manufacturer/  
Part Number  
Ref.  
Description  
Size  
Vendor/Number  
Newark  
C1, C2,  
C3, C4  
Capacitor, 1 µF,  
80%/–20%, nonpolarized,  
SMD  
0603  
4
Murata  
GRM39-Y5V105Z10PT  
C5  
Capacitor, 10 µF, 6.3 V,  
A
1
3
2
1
1
Panasonic  
ECS-TOJY106R  
Digi-Key  
PCS1106CT-ND  
SMD  
R1, R2,  
R4  
Resistor, 20 k, 1/16 W,  
5%, SMD  
0603  
Panasonic  
ERJ-3GSYJ203  
Digi-Key  
R3, R5  
Resistor, 80 k, 1/16 W,  
5%, SMD  
0603  
Panasonic  
ERJ-3GSYJ803  
Digi-Key  
S1  
Switch, momentary  
SMD  
Panasonic  
P8048SCT-ND  
Digi-Key  
P8048SCT-ND  
U1  
IC, TPA122, audio  
amplifier, 150 mW,  
2-channel, SMD  
MSOP-8  
TI  
TPA122DGN  
Terminal post headers  
11  
1
Sullins  
Digi-Key  
S1022-36-ND  
PCB1  
PCB, TPA122 MSOP EVM  
SLOP127  
Due to the very small size of the MSOP IC package, the standard part number TPA122 is replaced with the code TIAAE  
3-12  
Details  
 

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