User’s Guide
1998
Mixed-Signal Products
SLOU025
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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
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iv
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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
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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
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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
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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 Ω 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-kΩ loads; less than 0.02% @
1 kHz and less than 0.4% from 20 Hz to 20 kHz into 32-Ω loads; and
less than 0.05% @ 1 kHz and less than 0.8% from 20 Hz to 20 kHz into
8-Ω 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
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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 Ω, 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
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1-4
Introduction
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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
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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
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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-Ω 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
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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-Ω headphones to the module V 1, V 2 pins through 33 µF
O
O
to 1000 µF output-coupling capacitors (figure 3–8) 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
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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
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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
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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-Ω speakers.
The evaluation module can be used with the TI Plug-N-Play Audio Amplifier
Evaluation Platform (Figure 3–1) 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 3–3.
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 kΩ
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
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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-Ω speakers with low distortion. As a line-level driver, distortion levels
(THD+N) are below 0.07% into 10-kΩ loads 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-Ω 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 3–4). 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
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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
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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
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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 3–5.
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
U2–U4
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).
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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 3–6). Each control line is pulled down by a 1-kΩ resistor to ground (R4
and R5). The switch in the headphone jack pulls one line or the other up to V
DD
through a 240 Ω 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
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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
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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 3–5). 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 3–7).
Figure 3–7. Typical Headphone Plug
Left
Right
GND
3-10
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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 kΩ).
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
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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 kΩ, 1/16 W,
5%, SMD
0603
Panasonic
ERJ-3GSYJ203
Digi-Key
R3, R5
Resistor, 80 kΩ, 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
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