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Texas Instruments TPA721MSOPEVM - (Rev. A) User guides
TPA721 MSOP
Audio Power Amplifier
Evaluation Module
User’s Guide
2001
Mixed-Signal Products
SLOU033A
IMPORTANT NOTICE
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TI’s standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary
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those mandated by government requirements.
Customers are responsible for their applications using TI components.
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Mailing Address:
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Post Office Box 655303
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Copyright  2001, Texas Instruments Incorporated
Preface
Related Documentation From Texas Instruments
J
J
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.
TPA721 700-mW Low-Voltage Audio Power Amplifier (literature
number SLOS231) This is the data sheet for the TPA721 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.
Chapter Title—Attribute Reference
iii
iv
Running Title—Attribute Reference
Contents
1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1
Feature Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3
TPA721 EVM Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-1
1-2
1-3
1-3
2
Quick Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1
Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2
Quick Start List for Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3
Quick Start List for Stand-Alone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-1
2-2
2-3
2-4
3
Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.1
Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
3.2
The TPA721 MSOP Audio Amplifier Evaluation Module . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
3.2.1 TPA721 Audio Amplifier IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
3.2.2 BTL Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
3.2.3 Module Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
3.2.4 Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
3.2.5 Internal Depop Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
3.3
Using The TPA721 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 Mute/Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
3.3.4 Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9
3.3.5 Inputs and Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10
3.4
Using The TPA721 MSOP EVM Stand-ALone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
3.4.1 TPA721 MSOP EVM Connected for BTL Output . . . . . . . . . . . . . . . . . . . . . . . . 3-11
3.5
TPA721 MSOP Audio Amplifier Evaluation Module Parts List . . . . . . . . . . . . . . . . . . . . 3-12
Chapter Title—Attribute Reference
v
Running Title—Attribute Reference
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 TPA721 MSOP Audio Amplifier Evaluation Module . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Quick Start Platform Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
Quick Start Module Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
The TI Plug-N-Play Audio Amplifier Evaluation Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
TPA721 MSOP EVM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
TPA721 MSOP EVM Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
TPA721 Audio Amplifier IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
Platform Signal Routing and Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
Mute/Mode and Polarity Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8
Typical Headphone Plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10
TPA721 MSOP EVM Connected for Stereo BTL Output . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
Tables
2–1
2–2
3–1
vi
Typical TI Plug-N-Play Platform Jumper and Switch Settings for the
TPA721 MSOP EVM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Platform Jumper and Switch Settings for the TPA721 MSOP EVM . . . . . . . . . . . . . . . . . . . 2-3
TPA721 MSOP EVM Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12
Chapter 1
Introduction
This chapter provides an overview of the Texas Instruments (TI) TPA721
MSOP audio amplifier evaluation module (SLOP215). 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
Feature Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–2
1.2
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–3
1.3
TPA721 MSOP EVM Specifications . . . . . . . . . . . . . . . . . . . . . . . . . 1–3
Introduction
1-1
Feature Highlights
1.1 Feature Highlights
The TI TPA721 MSOP audio amplifier evaluation module and the TI
plug-n-play audio amplifier evaluation platform include the following features:
-
-
TPA721 Low-Voltage Audio Power Amplifier Evaluation Module
J
J
J
J
J
J
-
1-2
3.3-V and 5-V operation
700-mW output power into 8 Ω at 5 V, BTL
Internal depop circuitry
Internal thermal and short-circuit protection
Module gain is set at –4 V/V in BTL mode, –2 V/V in SE mode
Quick and Easy Configuration With the TI Plug-N-Play Audio Amplifier
Evaluation Platform
J
-
Single channel, bridge-tied load (BTL)
J
J
J
J
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
J
J
J
J
J
Onboard 9-V battery
External 5-V – 15-V (VCC) supply inputs
External regulated VDD supply input
Socket for onboard 5-V/3.3-V VDD voltage regulator EVM
Onboard overvoltage and reverse polarity power protection
Platform Audio Input and Output Connections
J
J
J
J
J
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
Introduction
Description
1.2 Description
The TPA721 MSOP audio power amplifier evaluation module is a complete,
low-power single-channel audio power amplifier. It consists of the TI TPA721
700-mW low-voltage 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 TPA721 Audio Amplifier Evaluation Module
Vdd GND
Shutdown
+
S1
C4
R1
C1
R2
R3
C2
R4
C3
U1 †
C5
R5
OUT–
GND
OUT+
C6
TEXAS
INSTRUMENTS
IN–
GND
SLOP215
TPA721 MSOP EVM
† Due to the very small size of the MSOP IC package, the standard part number TPA721 is replaced with the code TIABC.
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, with room for a pair of TPA721 MSOP evaluation modules, 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,
and connects them to a versatile array of standard audio input and output jacks
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 TPA721 EVM Specifications
Supply voltage range, VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 V to 5.5 V
Supply current, IDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450 mA, max
Continuous output power, PO: 8-Ω BTL, VDD = 5 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 700 mW
Audio input voltage, VI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Vpp, max
Minimum load impedance, RL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Ω
Introduction
1-3
1-4
Introduction
Chapter 2
Quick Start
Follow the steps in this chapter to quickly prepare the TPA721 MSOP audio
amplifier EVM for use. Using the TPA721 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
TPA721 MSOP EVM. They will cause the TPA721 amplifier IC on the EVM to
shut down when a plug is inserted into platform headphone jack J10.
Table 2–1. Typical TI Plug-N-Play Platform Jumper and Switch Settings for the TPA721
MSOP EVM
EVM
JP6
JP7
JP8
S2
S3
TPA721
Mute
X
Hi
Note 2
X
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
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–2
2.1
Precautions
2.2
Quick Start List for Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–3
2.3
Quick Start List for Stand-Alone
. . . . . . . . . . . . . . . . . . . . . . . . . . . 2–4
Quick Start
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 VCC power input connector J1, J2, and/or VDD power
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
6b
1 10
C1+
On
Off
6b
ICC
VR2
JP4
VR1
+
U2
9
Speaker
Output
– Left
Out
On
Conditioning
4
J9
Left
Out
+
Stereo
Headphone
Output
HP Out
J10
+
S3
HP
Source
Spk(U2-U4) C3 C2
JP8
U5
JP7
HP(U5)
U2-U4
R3
R4
5
+
JP6
U4
U5
GND
TP1
TEXAS
INSTRUMENTS
1997
2-2
+ Right –
Out
U3
Off
S2
U1
J5
Left
In
3
Mode
Mute
Polarity
Lo
Hi
****CAUTION****
Do not insert or remove
EVM boards with power
applied
Plug-N-Play Audio Amplifier
Evaluation Platform
SLOP097 Rev. C.1
J6
VDD
In/Out
LED2
VDD
Audio
Power
Amps
J4
Stereo
In
Audio
Input
J8
J7 Right
Out
JP5
IDD
LED1
VCC
J3
Right
In
8
DC
Power
In/Out
R2
R1
Signal Conditioning
6a
F2
B1
D1
D2
D3
D4 J2
AC/DC
In
Power
Input
U6
6b
POWER
SUPPLY
S1
Pwr
J1
VCC
In
+
JP3
Batt
JP2
AC/DC
JP1 (J2)
VCC(J1)
DC
SOURCE
F1
6b
9
R5
2
Quick Start
Quick Start List for Platform
2.2 Quick Start List for Platform
-
Follow these steps when using the TPA721 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) Ensure that all external power sources are set to OFF and that the platform
power switch S1 is set to OFF.
2) Install a TPA721 MSOP module in platform sockets U3 and U4 for stereo
operation (or a module in either U3 or U4 for single channel operation),
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 JP8 to Hi.
5) Set jumper JP6 to select the Mute control input (causes the TPA721 to
shut down if a plug is inserted into platform headphone jack J10).
Table 2–2. Platform Jumper and Switch Settings for the TPA721 MSOP EVM
EVM
JP6
JP7
JP8
S2
S3
TPA721
Mute
X
Hi
Note 2
X
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 VDD power input connector J6, taking care
to observe marked polarity,
or
-
b) Install a 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 VCC power input J1 or J2 and jumper the 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 8-Ω – 32-Ω speakers to left and right RCA jacks J7 and J9 or to
stripped wire connectors J8.
Power Up
10) Verify correct voltage and input polarity and set the external power supply
to ON. If VCC and an on-board regulator EVM are used to provide VDD,
set platform power switch S1 to ON.
Platform LED2 should light indicating the presence of VDD, and the evaluation
modules installed on the platform should begin operation.
11) Adjust the signal source level as needed.
Quick Start
2-3
Quick Start List for Stand-Alone
2.3 Quick Start List for Stand-Alone
Follow these steps to use the TPA721 MSOP EVM stand-alone or when
connecting it into existing circuits or equipment. Connections to the TPA721
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. Numbered callouts for selected steps are shown in
Figure 2–2 and details appear in Chapter 3.
Figure 2–2. Quick Start Module Map
2
Vdd GND
Shutdown
+
5
S1
C4
R1
C1
R2
R3
C2
R4
C3
U1 †
C5
R5
OUT–
GND
6
OUT+
C6
TEXAS
INSTRUMENTS
IN–
4
IN+
SLOP215
TPA721 MSOP EVM
† Due to the very small size of the MSOP IC package, the standard part number TPA721 is replaced with the code TIABC
-
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 positive lead from the audio source to the module IN– pin and
the negative lead to the In+ pin.
5) Connect the S1 pin to VDD through a normally open switch.
-
6) Connect an 8-Ω – 32-Ω speaker to the module OUT+ and OUT– pins.
Power Up
7) Verify correct voltage and input polarity and set the external power supply
to ON.
The EVM should begin operation.
8) Adjust the signal source level as needed.
2-4
Quick Start
Chapter 3
Details
This chapter provides details on the TPA721 IC, the evaluation module, the
steps in the Quick-Start List, additional application information, and a parts list
for the TPA721 MSOP evaluation module.
Topic
Page
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–2
3.1
Precautions
3.2
The TPA721 MSOP Audio Power Amplifier Evaluation Module
3.3
Using The TPA721 MSOP EVM With The Plug-N-Play
Evaluation Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–6
3.4
Using The TPA721 MSOP EVM Stand-Alone . . . . . . . . . . . . . . . . . . . . 3–11
3.5
TPA721 MSOP Audio Power Amplifier Evaluation
Module Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–12
Details
. . 3–3
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 VCC power input connector J1, J2, and/or VDD power
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
C1+
On
Off
ICC
VR2
JP4
VR1
F2
+
J6
VDD
In/Out
J8
J7 Right
Out
LED2
VDD
+ Right –
Out
U3
Off
S2
J4
Stereo
In
U2
U1
Speaker
Output
– Left
Out
On
Conditioning
J5
Left
In
J9
Left
Out
+
Stereo
Headphone
Output
HP Out
J10
+
S3
HP
Source
R4
Spk(U2-U4) C3 C2
JP8
U5
JP7
HP(U5)
U2-U4
U5
GND
TP1
TEXAS
INSTRUMENTS
1997
R3
+
JP6
U4
Mode
Mute
Polarity
Lo
Hi
****CAUTION****
Do not insert or remove
EVM boards with power
applied
3-2
U6
JP5
IDD
LED1
VCC
J3
Right
In
Audio
Power
Amps
Plug-N-Play Audio Amplifier
Evaluation Platform
SLOP097 Rev. C.1
DC
Power
In/Out
R2
R1
Signal Conditioning
Audio
Input
POWER
B1
D1
D2
D3
D4 J2
AC/DC
In
SUPPLY
S1
Pwr
J1
JP3
Batt
JP2
AC/DC
JP1 (J2)
VCC(J1)
DC
SOURCE
VCC
In
+
Power
Input
F1
R5
Details
The TPA721 MSOP Audio Power Amplifier Evaluation Module
3.2 The TPA721 MSOP Audio Power Amplifier Evaluation Module
The TPA721 MSOP audio power amplifier evaluation module is powered by
a TPA721 700-mW low-power audio amplifier IC. The EVM includes a
shutdown control signal input with an onboard switch for manual shutdown.
The 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, which
automatically makes all the signal input and output, 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. TPA721 MSOP EVM
Vdd GND
Shutdown
+
S1
C4
R1
C1
R2
R3
C2
R4
C3
U1 †
C5
OUT–
GND
OUT+
R5
C6
TEXAS
INSTRUMENTS
IN–
GND
SLOP215
TPA721 MSOP EVM
† Due to the very small size of the MSOP IC package, the standard part number TPA721 is replaced with the code TIABC
Figure 3–3. TPA721 MSOP EVM Schematic Diagram
S1
No
Shutdown
R1
20 kΩ
2
C1
C2 1 µF
NA
GND
R2
0Ω
3
4
Shutdown VO –
Bypass
GND
In+
VDD
In –
VO +
R3
NA
C3
1 µF
Audio Input–
R4
20 kΩ
Note:
1
VDD
2.5 V to 5.5 V C4 GND
10 µF
+
8
7
6
5
OUT–
C5
1 µF
GND
OUT+
R5
39 kΩ
C6
5 pF
NA is not assembled on PCB.
Details
3-3
The TPA721 MSOP Audio Power Amplifier Evaluation Module
3.2.1
TPA721 Audio Amplifier IC
The TPA721 audio amplifier IC is a CMOS device intended for bridge-tied load
(BTL) operation in battery-powered applications. Supplied in a very small
surface-mount package, the TPA721 has been designed to operate from low
supply voltages (between approximately 2.5 V and 5.5 V) and to deliver up to
approximately 700 mW into an 8-Ω, BTL (Figure 3 – 4). Typical applications
include portable phones, toys, games, and similar hand-held audio
applications.
Figure 3–4. TPA721 Amplifier IC
4
_
IN –
3
IN+
+
5
OUT+
6
VDD
2
VDD/2
BYPASS
7
+
GND
1
SHUTDOWN
_
8
OUT–
Bias Control
The IC includes two separate internal amplifiers, depop circuitry, and a
shutdown control. The two amplifiers operate as mirror images of each other
in the bridge-tied load (BTL) configuration for increased power. BTL operation
provides many benefits, including quadruple the output power of single-ended
operation and no need for bulky output coupling capacitors. For more
information, see the TPA721 amplifier IC data sheet, TI literature number
SLOS231.
3.2.2
BTL Operation
The TPA721 amplifier IC operates in the BTL mode, which means that the
output signal from OUT+ must go through the speaker load and be returned
directly to OUT–, and not to system ground. This requires that the OUT– line
be isolated not only from system ground, but also from the OUT– lines of any
other amplifiers in the system. The platform provides such isolated output lines
from the amplifier EVM sockets directly to separate left and right speaker
connectors.
3.2.3
Module Gain
The TPA721 MSOP evaluation module has a set gain of 2. However, the gain
can be adjusted to a maximum of 22 by changing the value of resistor R5
(Figure 3–3). Use the following equation to determine value of R4:
Gain
3-4
+ –R5
R4
2 for BTL
Details
The TPA721 MSOP Audio Power Amplifier Evaluation Module
The TPA721 amplifier IC, like most other amplifiers, exhibits its best distortion
and noise performance at lower gain levels (see the TPA721 data sheet). Even
so, the TPA721 at its highest gain setting has significantly less distortion than
most low-cost speakers.
Gain versus total harmonic distortion (THD) should be considered in each
application. Both the module input signal level and the TPA721 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 TPA721 input, and the TPA721 gain should be kept as low as
possible.
3.2.4
Shutdown
When the shutdown terminal of the TPA721 amplifier IC is taken high, the IC
ceases operation and enters a low-power state. This is accomplished by
applying a control signal to the module shutdown pin (S1) or by pressing the
shutdown switch 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 shutdown (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 (JP8).
3.2.5
Internal Depop Circuitry
Internal depop circuitry reduces or eliminates the various turn-on transients
that might appear at the output during the transition from power off or shutdown
mode to normal operation. These output transients are often heard as a pop
from the speaker and occur when the two amplifiers in the IC turn on or off at
different rates, causing a voltage spike to appear across the output. The depop
circuitry adds a delay with an RC network at the amplifier IC bypass pin to help
ensure that the amplifiers turn on and off at the same rate, thus eliminating the
pop. For best results, bypass capacitor C1 should have a value between
0.1 µF and 2.2 µF. A 1 µF unit was selected for the EVM.
Details
3-5
Using The TPA721 MSOP EVM With the Plug-N-Play Evaluation Platform
3.3 Using The TPA721 MSOP EVM With the Plug-N-Play Evaluation Platform
The TPA721 MSOP audio amplifier evaluation module was designed to be
used with the TI plug-n-play audio amplifier evaluation platform. It simply plugs
into socket U3 or U4.
The following paragraphs provide additional details for using the TPA721
MSOP EVM 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 U3 or U4 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 small amount.
3) Change to the opposite side of the module and use the tool to pry that side
up a small amount.
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 TPA721 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
Off
R
Audio
Input
U1
Signal
Conditioning
U3
TPA721
Amplifier EVM
R
U4
TPA721
Amplifier EVM
L
+
R
–
S2
L
On
–
J7, J8, J9
Speaker
Outputs
L
+
U2 – U4
R
U5
Stereo
Headphone
Amplifier
R
S3
+
–
J10
Headphone
Output
–
GND
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
audio input signal applied directly to the inputs of the TPA721 power amplifiers.
3.3.3
Switch S2 selects signal conditioning or bypasses it
Mute/Mode
The TPA721 MSOP EVM is equipped with a shutdown (mute) control input pin.
When this input is tied to VDD, the TPA721 amplifier IC on the module shuts
down and assumes a low-power mode. When the EVM 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 shut down (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 (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 VDD through a
240 Ω resistor (R3) depending on whether or not a plug is inserted in J10.
Details
3-7
Using The TPA721 MSOP EVM With the Plug-N-Play Evaluation Platform
Figure 3–6. Mute/Mode and Polarity Control
VDD
R3
240 Ω
Polarity
JP8
Lo
J10
Headphone
Jack
R4
1 kΩ
3.3.3.2
R5
1 kΩ
Hi
SPK
(U2–U4)
JP6
Mode
Mute
U3, U4
Power
Amplifiers
Mute/Mode Select (JP6)
A 3-pin jumper header (JP6) on the platform, functioning as a SPDT switch,
routes the control signal from the headphone jack to either the mute control
input pin or the mode control input pin of the evaluation module.
J
J
3.3.3.3
To mute the TPA721 MSOP amplifier module using the control signal
from the platform headphone jack, jumper JP6 to MUTE.
To not affect the TPA721 amplifier when a plug is inserted into the
headphone jack, jumper JP6 to Mode or leave JP6 unjumpered.
Mute/Mode Polarity Select (JP8)
A second 3-pin jumper header (JP8) on the platform selects the control signal
polarity by connecting either the active-high or the active-low line from the
headphone jack to jumper JP6.
-
When JP6 is set to mute, use the following JP8 settings for the TPA721:
J
J
-
3-8
To mute the TPA721 MSOP amplifier module when a plug is inserted
into the headphone jack, jumper JP8 to Hi (this is the typical setting).
To mute the TPA721 MSOP amplifier module until a plug is inserted
into the headphone jack, jumper JP8 to Lo.
When JP6 is set to mode, the TPA721 amplifier is unaffected by the insertion of the headphone plug.
Details
Power Requirements
3.3.4
Power Requirements
The TPA721 MSOP audio power amplifier evaluation module can operate
from any voltage between approximately 2.5 V and 5.5 V; however, the
TPA721 amplifier IC on the module is characterized for operation at 3.3 V and
5 V. For best performance (highest output power with lowest distortion), the
module should be operated at approximately 5 V, unless there is a specific
reason for operating it from a lower voltage.
The TI plug-n-play audio amplifier evaluation platform with a voltage regulator
EVM installed on it can provide a regulated VDD supply from a wide variety of
unregulated VCC voltage inputs between approximately 5.5 V and 12 V,
including an onboard 9 -V battery. Or, an external regulated power source can
be used to supply VDD voltage to the platform and the TPA721 MSOP
evaluation modules installed on it.
The platform is equipped with overvoltage and reverse-polarity supply voltage
input protection in the form of fused crowbar circuits.
-
-
VDD voltage applied to platform screw terminals J6 MUST NOT exceed
the absolute maximum rating for the TPA721 amplifier IC installed on the
evaluation module (6 V) or damage to the IC may result. In no case should
VDD voltage of the incorrect polarity or in excess of 6.1 V be applied to
screw terminals J6 of the platform, or the power protection circuit on the
VDD line will trip.
VCC voltage applied to the platform MUST NOT exceed the maximum
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 VCC voltage applied to the platform exceed
15 V, or the overvoltage protection circuit on the VCC bus will trip.
Details
3-9
Inputs and Outputs
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
Amplified audio output signals 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).
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 TPA721 power amplifier EVMs to operate in the highly-efficient
bridge-tied load configuration.
Figure 3–7. Typical Headphone Plug
Left
3-10
Right
GND
Details
Using The TPA721 MSOP EVM Stand-Alone
3.4 Using The TPA721 MSOP EVM Stand-Alone
Using the TPA721 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 range and the isolated OUT+ and OUT– lines for BTL
operation requirement exists.
Note that the mute signal applied to the EVM shutdown pins must be able to
supply enough current to overcome the pulldown resistors on the modules
(20 kΩ || 20 kΩ for two EVMs).
3.4.1
TPA721 MSOP EVM Connected for BTL Output
Figure 3–8. TPA721 MSOP EVM Connected for Stereo BTL Output
5 VDC
Vdd GND
Shutdown
+
S1
C4
R1
U1 †
C1
R2
R3
C2
R4
C3
C5
OUT–
GND
R5
C6
TEXAS
INSTRUMENTS
Audio Input
(Right)
IN–
GND
SLOP215
TPA721 MSOP EVM
5 VDC
GND
Vdd
External Mute
Control
(active high)
GND
Shutdown
+
S1
C4
R1
C1
R2
R3
C2
R4
C3
Audio Input
(Left)
Right
OUT+
U1 †
C5
R5
OUT–
GND
Left
OUT+
C6
TEXAS
INSTRUMENTS
IN–
GND
SLOP215
TPA721 MSOP EVM
† Due to the very small size of the MSOP IC package, the standard part number TPA721 is replaced with the code TIABC.
Details
3-11
TPA721 MSOP Audio Power Amplifier Evaluation Module Parts List
3.5 TPA721 MSOP Audio Power Amplifier Evaluation Module Parts List
Table 3–1. TPA721 MSOP EVM Parts List
Reference
Description
Size
EVM
Qty.
Manufacturer/
Part Number
Vendor
Number
A
1
Panasonic
ECS-TOJY106R
Digi-Key
PCS1106CT-ND
Murata
GRM39-Y5V105Z10PT
Newark
C4
Capacitor, 10 µF, 6.3 V
C1, C3, C5
Capacitor, 1 µF, 80%/–20%,
nonpolarized
0603
3
C2, C6
Capacitor, pad only
0603
0
R1, R4
Resistor, 20 kΩ, 1/16 W, 5%
0603
2
Panasonic
ERJ-3GSYJ203
Digi-Key
P20KGCT-ND
R5
Resistor, 39 kΩ, 1/16 W, 5%
0603
1
Panasonic
ERJ-3GSYJ393
Digi-Key
P39KGCT-ND
R2
Resistor, 0 Ω, 1/16 W
0603
1
Panasonic
ERJ-3GSY0R00V
Digi-Key
P0.0GCT-ND
R3
Resistor, pad only
0603
1
S1
Switch, momentary
1
Panasonic
P8048SCT-ND
Digi-Key
P8048SCT-ND
Terminal Post Headers
9
Sullins
PTC36SABN
Digi-Key
S1022-36-ND
1
TI
TPA721DGN
U1
IC, TPA721DGN†, audio
amplifier, 700 mW, mono
PCB1
PCB, TPA721 MSOP EVM
MSOP-8
1
† Due to the very small size of the MSOP IC package, the standard part number TPA721 is replaced with the code TIABC.
Note:
3-12
All items are SMD except as noted.
Details
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