TPA0242PWPR [TI]
STEREO 2.8-W AUDIO POWER AMPLIFIER WITH DC VOLUME CONTROL AND MUX CONTROL;
| 型号： | TPA0242PWPR |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | STEREO 2.8-W AUDIO POWER AMPLIFIER WITH DC VOLUME CONTROL AND MUX CONTROL 放大器 功率放大器 光电二极管 商用集成电路 |
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TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
PWP PACKAGE
(TOP VIEW)
Compatible With PC 99 Desktop Line-Out
Into 10-kΩ Load
Compatible With PC 99 Portable Into 8-Ω
Load
1
24
23
22
21
20
19
18
17
16
15
14
13
GND
HP/LINE
VOLUME
LOUT+
LLINEIN
LHPIN
GND
2
RLINEIN
SHUTDOWN
ROUT+
RHPIN
3
Internal Gain Control, Which Eliminates
External Gain-Setting Resistors
4
5
DC Volume Control From 20 dB to –40 dB
2-W/Ch Output Power Into 3-Ω Load
Input MUX Select Terminal
PC-Beep Input
6
V
DD
7
PV
PV
DD
DD
8
RIN
LOUT–
LIN
BYPASS
GND
CLK
9
ROUT–
SE/BTL
PC-BEEP
GND
10
11
12
Depop Circuitry
Stereo Input MUX
Fully Differential Input
Low Supply Current and Shutdown Current
Surface-Mount Power Packaging
24-Pin TSSOP PowerPAD
description
The TPA0242 is a stereo audio power amplifier in a 24-pin TSSOP thermally enhanced package capable of
delivering 2 W of continuous RMS power per channel into 3-Ω loads. This device minimizes the number of
external components needed, which simplifies the design and frees up board space for other features. When
driving 1 W into 8-Ω speakers, the TPA0242 has less than 0.22% THD+N across its specified frequency range.
Included within this device is integrated depop circuitry that virtually eliminates transients that cause noise in
the speakers.
Amplifier gain is controlled by a dc voltage input on the VOLUME terminal. There are 31 discrete steps covering
the range of 20 dB (maximum volume setting) to –40 dB (minimum volume setting) in 2 dB steps. When the
VOLUME terminal exceeds 3.54 V, the device is muted. An internal input MUX allows two sets of stereo inputs
to the amplifier. The HP/LINE terminal allows the user to select which MUX input is active regardless of whether
the amplifier is in SE or BTL mode. In notebook applications, where internal speakers are driven as BTL and
the line outputs (often headphone drive) are required to be SE, the TPA0242 automatically switches into SE
mode when the SE/BTL input is activated, and this effectively reduces the gain by 6 dB.
The TPA0242 consumes only 20 mA of supply current during normal operation. A miserly shutdown mode
reduces the supply current to less than 150 µA.
The PowerPAD package (PWP) delivers a level of thermal performance that was previously achievable only
in TO-220-type packages. Thermal impedances of approximately 35°C/W are truly realized in multilayer PCB
applications. This allows the TPA0242 to operate at full power into 8-Ω loads at ambient temperatures of 85°C.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PowerPAD is a trademark of Texas Instruments Incorporated.
Copyright 1999, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
functional block diagram
RHPIN
32-Step
Volume
Control
R
MUX
RLINEIN
–
+
ROUT+
VOLUME
RIN
–
+
ROUT–
PC
Beep
PC-BEEP
PV
DD
Power
Management
Depop
Circuitry
V
DD
BYPASS
SHUTDOWN
SE/BTL
MUX
Control
GND
HP/LINE
32-Step
Volume
Control
LHPIN
L
MUX
LLINEIN
–
+
LOUT+
LIN
–
+
LOUT–
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
AVAILABLE OPTIONS
PACKAGED DEVICE
†
T
A
TSSOP
(PWP)
–40°C to 85°C
TPA0242PWP
†
The PWP package is available taped and reeled. To order a taped and reeled part,
add the suffix R to the part number (e.g., TPA0242PWPR).
Terminal Functions
TERMINAL
NAME
BYPASS
I/O
DESCRIPTION
NO.
11
Tap to voltage divider for internal mid-supply bias generator
If a 47-nF capacitor is attached, the TPA0242 generates an internal clock. An external clock can override
the internal clock input to this terminal.
CLK
17
I
1, 12
13, 24
GND
Ground connection for circuitry. Connected to thermal pad
LHPIN
LIN
6
10
5
I
I
Left channel headphone input, selected when SE/BTL is held high
Common left input for fully differential input. AC ground for single-ended inputs
Left channel line negative input, selected when SE/BTL is held low
Left channel positive output in BTL mode and positive output in SE mode
Left channel negative output in BTL mode and high-impedance in SE mode
LLINEIN
LOUT+
LOUT–
I
4
O
O
9
HP/LINE is the input MUX control input. When the HP/LINE terminal is held high, the headphone inputs
(LHPIN or RHPIN [6, 20]) are active. When the HP/LINE terminal is held low, the line BTL inputs (LLINEIN
or RLINEIN [5, 23]) are active.
HP/LINE
2
I
The input for PC Beep mode. PC-BEEP is enabled when a > 1-V (peak-to-peak) square wave is input to
PC-BEEP.
PC-BEEP
14
I
PV
DD
7, 18
20
8
I
I
Power supply for output stage
RHPIN
Right channel headphone input, selected when SE/BTL is held high
Common right input for fully differential input. AC ground for single-ended inputs
Right channel line input, selected when SE/BTL is held low
RIN
I
RLINEIN
ROUT+
ROUT–
SE/BTL
SHUTDOWN
23
21
16
15
22
19
I
O
O
I
Right channel positive output in BTL mode and positive output in SE mode
Right channel negative output in BTL mode and high-impedance in SE mode
Hold SE/BTL low for BTL mode and hold high for SE mode.
I
When held low, this terminal places the entire device, except PC-BEEP detect circuitry, in shutdown mode.
V
I
Analog V
DD
input supply. This terminal needs to be isolated from PV to achieve highest performance.
DD
DD
VOLUME
VOLUME detects the dc level at the terminal and sets the gain for 31 discrete steps covering a range of
20 dB to –40 dB for dc levels of 0.15 V to 3.54. When the dc level is over 3.54 V, the device is muted.
3
I
3
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
†
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
Supply voltage, V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 V
DD
Input voltage, V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to V +0.3 V
I
DD
Continuous total power dissipation . . . . . . . . . . . . . . . . . . . . . internally limited (see Dissipation Rating Table)
Operating free-air temperature range, T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to 85°C
Operating junction temperature range, T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to 150°C
A
J
Storage temperature range, T
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to 150°C
stg
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C
†
Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
DISSIPATION RATING TABLE
PACKAGE
T
A
≤ 25°C
DERATING FACTOR
T
A
= 70°C
T = 85°C
A
‡
PWP
2.7 W
21.8 mW/°C
1.7 W
1.4 W
‡
Please see the Texas Instruments document, PowerPAD Thermally Enhanced Package Application Report
(literature number SLMA002), for more information on the PowerPAD package. The thermal data was
measured on a PCB layout based on the information in the section entitled Texas InstrumentsRecommended
Board for PowerPAD on page 33 of the before mentioned document.
recommended operating conditions
MIN
4.5
4
MAX
UNIT
Supply voltage, V
DD
5.5
V
SE/BTL, HP/LINE
SHUTDOWN
High-level input voltage, V
V
IH
2
SE/BTL, HP/LINE
SHUTDOWN
3
0.8
85
Low-level input voltage, V
V
IL
Operating free-air temperature, T
–40
°C
A
electrical characteristics at specified free-air temperature, V
noted)
= 5 V, T = 25°C (unless otherwise
A
DD
PARAMETER
Output offset voltage (measured differentially)
Supply ripple rejection ratio
TEST CONDITIONS
MIN
TYP
MAX
25
UNIT
mV
dB
|V
|
V = 0, A = 2 V/V
OS
I
v
V
V
V
= 4.9 V to 5.1 V
67
DD
DD
|I
|I
|
High-level input current
= 5.5 V, V = V
900
900
nA
IH
I
DD
|
Low-level input current
Supply current
= 5.5 V, V = 0 V
nA
mA
µA
IL
DD
I
BTL mode
SE mode
20
10
I
DD
DD(SD)
I
Supply current, shutdown mode
150
300
4
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
operating characteristics, V
noted)
= 5 V, T = 25°C, R = 4 Ω, Gain = 2 V/V, BTL mode (unless otherwise
DD
A
L
PARAMETER
TEST CONDITIONS
f = 1 kHz
MIN
TYP
2
MAX
UNIT
P
O
Output power
THD = 1%,
W
THD + N Total harmonic distortion plus noise
P
= 1 W,
f = 20 Hz to 15 kHz
0.22%
>15
65
O
B
OM
Maximum output power bandwidth
Supply ripple rejection ratio
THD = 5%
kHz
dB
BTL mode
SE mode
BTL mode
SE mode
f = 1 kHz, C = 0.47 µF
B
60
34
C
= 0.47 µF,
B
V
n
Noise output voltage
µV
RMS
f = 20 Hz to 20 kHz
44
TYPICAL CHARACTERISTICS
Table of Graphs
FIGURE
vs Output power
vs Voltage gain
vs Frequency
vs Output voltage
vs Bandwidth
vs Frequency
vs Frequency
vs Frequency
vs Bandwidth
1, 4, 6, 8, 10
2
3, 5, 7, 9, 11
12
THD+N
Total harmonic distortion plus noise
V
n
Output noise voltage
Supply ripple rejection ratio
Crosstalk
13
14, 15
16, 17, 18
19
Shutdown attenuation
Signal-to-noise ratio
Closed loop response
Output power
SNR
20
21, 22
23, 24
25, 26
27
P
P
vs Load resistance
vs Output power
vs Ambient temperature
vs Gain
O
D
I
Power dissipation
Input impedance
Z
28
5
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
TYPICAL CHARACTERISTICS
TOTAL HARMONIC DISTORTION PLUS NOISE
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
vs
OUTPUT POWER
VOLTAGE GAIN
10%
1%
P
V
R
= 1 W for A ≥6dB
V
O
O
L
= 1 V
for A ≤4 dB
RMS
= 8 Ω
V
BTL
R
= 4 Ω
L
1%
R
= 8 Ω
L
R
= 3 Ω
L
0.1%
0.1%
A
= +20 to 4 dB
V
f = 1 kHz
BTL
0.01%
0.01%
0.5 0.75
1
1.25 1.5 1.75
2
2.25 2.5 2.75
3
–40
–30
–20
–10
0
10
20
P
O
– Output Power – W
A
- Voltage Gain - dB
V
Figure 1
Figure 2
TOTAL HARMONIC DISTORTION PLUS NOISE
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
vs
FREQUENCY
OUTPUT POWER
10%
10%
R
= 3 Ω
= +20 to 0 dB
L
R
= 3 Ω
= +20 to +4 dB
L
A
V
A
V
BTL
BTL
1%
f = 20 kHz
1%
P
O
= 0.5 W
P
O
= 1 W
f = 1 kHz
0.1%
0.01%
0.1%
f = 20 Hz
P
O
= 1.75 W
0.01%
20
100
1k
10k 20k
0.01
0.1
1
10
f – Frequency – Hz
P
O
– Output Power – W
Figure 3
Figure 4
6
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
TYPICAL CHARACTERISTICS
TOTAL HARMONIC DISTORTION PLUS NOISE
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
vs
FREQUENCY
OUTPUT POWER
10%
10%
1%
R
= 4 Ω
= +20 to +4 dB
L
R
= 4 Ω
= +20 to +4 dB
L
A
V
A
V
BTL
BTL
1%
f = 20 kHz
f = 1 kHz
P
O
= 0.25 W
0.1%
0.1%
f = 20 Hz
P
O
=1.5 W
P
O
= 1 W
0.01%
0.01%
20
100
1k
10k 20k
0.01
0.1
1
10
f – Frequency – Hz
P
O
– Output Power – W
Figure 5
Figure 6
TOTAL HARMONIC DISTORTION PLUS NOISE
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
vs
FREQUENCY
OUTPUT POWER
10%
10%
R
= 8 Ω
= +20 to +4 dB
L
R
= 8 Ω
= +20 to +4 dB
L
A
V
A
V
BTL
BTL
1%
1%
f = 20 kHz
P
O
= 0.25 W
0.1%
0.01%
0.1%
P
O
= 0.5 W
f = 1 kHz
f = 20 Hz
P
= 1 W
O
0.01%
20
100
1k
10k 20k
0.01
0.1
1
10
f – Frequency – Hz
P
O
– Output Power – W
Figure 7
Figure 8
7
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
TYPICAL CHARACTERISTICS
TOTAL HARMONIC DISTORTION PLUS NOISE
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
vs
FREQUENCY
OUTPUT POWER
10%
1%
10%
1%
R
A
SE
= 32 Ω
= +14 to +4 dB
R
A
SE
= 32 Ω
= +14 to +4 dB
L
V
L
V
f = 20 kHz
0.1%
P
O
= 25 mW
0.1%
0.01%
f = 1 kHz
P
O
= 75 mW
1k
P
O
= 50 mW
100
f = 20 Hz
0.001%
0.01%
20
10k 20k
0.01
0.1
1
f – Frequency – Hz
P
O
– Output Power – W
Figure 9
Figure 10
TOTAL HARMONIC DISTORTION PLUS NOISE
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
vs
FREQUENCY
OUTPUT VOLTAGE
10%
10%
R
= 10 kΩ
= +14 to 0 dB
L
A
V
SE
1%
1%
f = 20 kHz
0.1%
0.1%
V
O
= 1 V
RMS
f = 1 kHz
0.01%
0.01%
R
= 10 kΩ
= +14 to +4 dB
L
A
V
f = 20 Hz
SE
0.001%
0.001%
20
100
1k
10k 20k
0.2 0.4 0.6 0.8
1
1.2 1.4 1.6 1.8
2
f – Frequency – Hz
V
O
– Output Voltage – V
RMS
Figure 11
Figure 12
8
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
TYPICAL CHARACTERISTICS
OUTPUT NOISE VOLTAGE
SUPPLY RIPPLE REJECTION RATIO
vs
vs
BANDWIDTH
FREQUENCY
160
140
120
0
–20
–40
–60
–80
V
R
= 5 V
R
C
BTL
= 8 Ω
= 0.47 µF
DD
= 4 Ω
L
B
L
A
V
= +20 dB
100
80
60
A
V
= +20 dB
40
A
V
= +6 dB
A
V
= +6 dB
–100
–120
20
0
0
100
1k
10k 20k
20
100
1k
10k 20k
BW – Bandwidth – Hz
f – Frequency – Hz
Figure 13
Figure 14
SUPPLY RIPPLE REJECTION RATIO
CROSSTALK
vs
FREQUENCY
vs
FREQUENCY
0
–20
–40
–60
–80
–40
–50
–60
–70
R
C
SE
= 32 Ω
= 0.47 µF
P
R
= 1 W
= 8 Ω
L
= +20 dB
L
B
O
A
V
BTL
A
= 0 dB
V
LEFT TO RIGHT
RIGHT TO LEFT
–80
–90
A
V
= +14 dB
–100
–110
–120
–100
–120
20
100
1k
10k 20k
20
100
1k
10k 20k
f – Frequency – Hz
f – Frequency – Hz
Figure 15
Figure 16
9
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
TYPICAL CHARACTERISTICS
CROSSTALK
vs
FREQUENCY
CROSSTALK
vs
FREQUENCY
–40
–50
–60
–40
–50
P
= 1 W
= 8 Ω
= +6 dB
V
= 1 V
RMS
O
L
O
L
R
A
R
A
= 10 kΩ
= +6 dB
V
V
BTL
SE
–60
–70
–70
–80
LEFT TO RIGHT
LEFT TO RIGHT
–80
–90
–90
RIGHT TO LEFT
RIGHT TO LEFT
–100
–100
–110
–120
–110
–120
20
100
1k
10k 20k
20
100
1k
10k 20k
f – Frequency – Hz
f – Frequency – Hz
Figure 17
Figure 18
SHUTDOWN ATTENUATION
SIGNAL-TO-NOISE RATIO
vs
vs
FREQUENCY
BANDWIDTH
0
–20
–40
–60
–80
120
115
V = 1 V
I
P
R
BTL
= 1 W
= 8 Ω
RMS
O
L
R
= 10 kΩ, SE
L
L
110
105
A
= +20 dB
V
100
95
R
= 32 Ω, SE
= 8 Ω, BTL
A
V
= +6 dB
90
–100
–120
R
85
80
L
20
100
1k
10k 20k
0
100
1k
10k 20k
f – Frequency – Hz
BW – Bandwidth – Hz
Figure 19
Figure 20
10
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
TYPICAL CHARACTERISTICS
CLOSED LOOP RESPONSE
180°
90°
30
25
R
= 8 Ω
= +20 dB
L
A
V
BTL
Gain
20
15
Phase
0°
10
5
0
–90°
–180°
–5
–10
10
100
1k
10k
100k
1M
f – Frequency – Hz
Figure 21
CLOSED LOOP RESPONSE
180°
90°
30
25
R
= 8 Ω
= +6 dB
L
A
V
BTL
Phase
20
15
0°
10
5
Gain
0
–90°
–180°
–5
–10
10
100
1k
10k
100k
1M
f – Frequency – Hz
Figure 22
11
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
TYPICAL CHARACTERISTICS
OUTPUT POWER
vs
LOAD RESISTANCE
OUTPUT POWER
vs
LOAD RESISTANCE
3.5
3
1500
1250
1000
750
A
BTL
= +20 to 0 dB
V
A = +14 to 0 dB
V
SE
2.5
2
10% THD+N
1.5
1
500
10% THD+N
250
0
0.5
0
1% THD+N
1% THD+N
0
8
16
24
32
40
48
56
64
0
8
16
24
32
40
48
56
64
R
– Load Resistance – Ω
L
R
– Load Resistance – Ω
L
Figure 23
Figure 24
POWER DISSIPATION
vs
OUTPUT POWER
POWER DISSIPATION
vs
OUTPUT POWER
1.8
1.6
0.4
0.35
0.3
3 Ω
4 Ω
1.4
1.2
1
4 Ω
0.25
0.2
0.8
0.6
8 Ω
0.15
0.1
8 Ω
0.4
32 Ω
f = 1 kHz
BTL
Each Channel
f = 1 kHz
BTL
Each Channel
0.05
0
0.2
0
0
0.5
1
1.5
2 2.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7 0.8
P
O
– Output Power – W
P
O
– Output Power – W
Figure 25
Figure 26
12
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
TYPICAL CHARACTERISTICS
POWER DISSIPATION
vs
AMBIENT TEMPERATURE
7
6
Θ
Θ
Θ
Θ
= 45.9°C/W
= 45.2°C/W
= 31.2°C/W
= 18.6°C/W
JA1
JA2
JA3
JA4
Θ
JA4
5
4
Θ
Θ
JA3
3
2
JA1,2
1
0
–40 –20
0
20 40 60 80 100 120 140 160
T
A
– Ambient Temperature – °C
Figure 27
INPUT IMPEDANCE
vs
GAIN
90
80
70
60
50
40
30
20
10
–40
–30
–20
–10
0
10
20
A
V
– Gain – dB
Figure 28
13
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
THERMAL INFORMATION
The thermally enhanced PWP package is based on the 24-pin TSSOP, but includes a thermal pad (see Figure 29)
to provide an effective thermal contact between the IC and the PWB.
Traditionally, surface mount and power have been mutually exclusive terms. A variety of scaled-down TO-220-type
packages have leads formed as gull wings to make them applicable for surface-mount applications. These packages,
however, have only two shortcomings: they do not address the very low profile requirements (<2 mm) of many of
today’s advanced systems, and they do not offer a terminal-count high enough to accommodate increasing
integration. Ontheotherhand, traditionallow-powersurface-mountpackagesrequirepower-dissipationderatingthat
severely limits the usable range of many high-performance analog circuits.
The PowerPAD package (thermally enhanced TSSOP) combines fine-pitch surface-mount technology with thermal
performance comparable to much larger power packages.
The PowerPAD package is designed to optimize the heat transfer to the PWB. Because of the very small size and
limited mass of a TSSOP package, thermal enhancement is achieved by improving the thermal conduction paths that
remove heat from the component. The thermal pad is formed using a patented lead-frame design and manufacturing
technique to provide a direct connection to the heat-generating IC. When this pad is soldered or otherwise thermally
coupled to an external heat dissipator, high power dissipation in the ultra-thin, fine-pitch, surface-mount package can
be reliably achieved.
DIE
Side View (a)
Thermal
Pad
DIE
End View (b)
Bottom View (c)
Figure 29. Views of Thermally Enhanced PWP Package
14
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
APPLICATION INFORMATION
Table 1. DC Volume Control
VOLUME (Terminal 3)
GAIN of AMPLIFIER
FROM
(V)
TO
(V)
(dB)
0
0.15
0.28
0.39
0.5
20
18
0.15
0.28
0.39
0.5
16
14
0.61
0.73
0.84
0.95
1.06
1.17
1.28
1.39
1.5
12
0.61
0.73
0.84
0.95
1.06
1.17
1.28
1.39
1.5
10
8
6
4
2
0
–2
–4
1.62
1.73
1.84
1.95
2.07
2.18
2.29
2.41
2.52
2.63
2.74
2.86
2.97
3.08
3.2
–6
1.62
1.73
1.84
1.95
2.07
2.18
2.29
2.41
2.52
2.63
2.74
2.86
2.97
3.08
3.2
–8
–10
–12
–14
–16
–18
–20
–22
–24
–26
–28
–30
–32
–34
–36
–38
–40
–85
3.31
3.42
3.54
5
3.31
3.42
3.54
selection of components
Figure 30 and Figure 31 are schematic diagrams of typical notebook computer application circuits.
15
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
APPLICATION INFORMATION
Right
C
IRHP
Head– 0.47 µF
phone
Input
Signal
RHPIN
20
R
MUX
23 RLINEIN
C
IRLINE
0.47 µF
Right
Line
–
ROUT+ 21
+
Input
Signal
8
RIN
C
RIN
0.47 µF
C
OUTR
PC BEEP
Input
Signal
330 µF
14
PC–BEEP
–
ROUT– 16
PC–
Beep
V
DD
C
PCB
0.47 µF
1 kΩ
+
V
DD
50 kΩ
100 kΩ
See Note A
VOLUME
CLK
3
PVDD 18
VDD 19
V
DD
Gain/
MUX
Control
17
C
SR
Depop
Circuitry
0.1 µF
C
CLK
47 nF
SE/BTL
15
V
DD
Power
Management
C
0.1 µF
BYPASS 11
SHUT–
SR
HP/LINE
LHPIN
2
6
5
C
ILHP
0.47 µF
Left
DOWN
22
Head–
phone
Input
C
BYP
0.47 µF
GND
To
L
MUX
System
Control
Signal
1 kΩ
LLINEIN
C
ILLINE
1,12,
13,24
0.47 µF
Left
Line
Input
Signal
–
+
LOUT+
4
C
OUTL
330 µF
10
LIN
C
LIN
0.47 µF
–
+
LOUT–
9
100 kΩ
NOTE A: A 0.1 µF ceramic capacitor should be placed as close as possible to the IC. For filtering lower–frequency noise signals, a larger
electrolytic capacitor of 10 µF or greater should be placed near the audio power amplifier.
Figure 30. Typical TPA0242 Application Circuit Using Single-Ended Inputs and Input MUX
16
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
APPLICATION INFORMATION
N/C
RHPIN
20
C
IRIN–
0.47 µF
Right
R
Negative
Differential
Input
MUX
23 RLINEIN
–
ROUT+ 21
Signal
+
C
IRIN+
0.47 µF
Right
Positive
Differential
Input
8
RIN
Signal
C
OUTR
330 µF
PC BEEP
Input
Signal
PC–
Beep
14
PC–BEEP
–
ROUT– 16
V
DD
1 kΩ
+
C
PCB
0.47 µF
V
DD
100 kΩ
50 kΩ
See Note A
VOLUME
CLK
3
PVDD 18
VDD 19
V
Gain/
MUX
Control
DD
17
C
SR
Depop
Circuitry
0.1 µF
C
CLK
47 nF
SE/BTL
15
V
DD
Power
Management
C
0.1 µF
BYPASS 11
SHUT–
SR
HP/LINE
LHPIN
2
6
5
N/C
DOWN
22
C
BYP
0.47 µF
GND
To
Left
L
MUX
System
Control
Negative
Differential
Input
1 kΩ
LLINEIN
1,12,
13,24
C
ILIN–
0.47 µF
–
+
LOUT+
4
Signal
C
OUTL
330 µF
C
ILIN+
0.47 µF
Left
Positive
Differential
Input
10
LIN
Signal
–
+
LOUT–
9
100 kΩ
NOTE A: A 0.1 µF ceramic capacitor should be placed as close as possible to the IC. For filtering lower–frequency noise signals, a larger
electrolytic capacitor of 10 µF or greater should be placed near the audio power amplifier.
Figure 31. Typical TPA0242 Application Circuit Using Differential Inputs
17
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
APPLICATION INFORMATION
input resistance
Each gain setting is achieved by varying the input resistance of the amplifier, which can range from its smallest
value to over 6 times that value. As a result, if a single capacitor is used in the input high pass filter, the –3 dB
or cut-off frequency will also change by over 6 times. If an additional resistor is connected from the input pin
of the amplifier to ground, as shown in the figure below, the variation of the cut-off frequency will be much
reduced.
R
f
C
R
I
IN
Input Signal
R
Figure 32. Resistor on Input for Cut-Off Frequency
The input resistance at each gain setting is given in Figure 28:
The –3 dB frequency can be calculated using the following formula:
1
ƒ
–3 dB
(1)
2
C R R
I
If the filter must be more accurate, the value of the capacitor should be increased while the value of the resistor
to ground should be decreased. In addition, the order of the filter could be increased.
input capacitor, C
I
In the typical application an input capacitor, C , is required to allow the amplifier to bias the input signal to the
I
proper dc level for optimum operation. In this case, C and the input impedance of the amplifier, Z , form a
I
I
high-pass filter with the corner frequency determined in equation 2.
–3 dB
(2)
1
f
c(highpass)
2 Z
C
I
IN
f
c
18
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
APPLICATION INFORMATION
The value of C is important to consider as it directly affects the bass (low frequency) performance of the circuit.
I
Consider the example where Z is 710 kΩ and the specification calls for a flat bass response down to 40 Hz.
I
Equation 2 is reconfigured as equation 3.
1
C
I
2 Z f
(3)
c
I
In this example, C is 5.6 nF so one would likely choose a value in the range of 5.6 nF to 1 µF. A further
I
consideration for this capacitor is the leakage path from the input source through the input network (C ) and the
I
feedback network to the load. This leakage current creates a dc offset voltage at the input to the amplifier that
reduces useful headroom, especially in high gain applications. For this reason a low-leakage tantalum or
ceramic capacitor is the best choice. When polarized capacitors are used, the positive side of the capacitor
should face the amplifier input in most applications as the dc level there is held at V /2, which is likely higher
DD
than the source dc level. Note that it is important to confirm the capacitor polarity in the application.
power supply decoupling, C
S
The TPA0242 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling
to ensure the output total harmonic distortion (THD) is as low as possible. Power supply decoupling also
prevents oscillations for long lead lengths between the amplifier and the speaker. The optimum decoupling is
achieved by using two capacitors of different types that target different types of noise on the power supply leads.
For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-series-resistance
(ESR) ceramic capacitor, typically 0.1 µF placed as close as possible to the device V
filtering lower-frequency noise signals, a larger aluminum electrolytic capacitor of 10 µF or greater placed near
lead, works best. For
DD
the audio power amplifier is recommended.
midrail bypass capacitor, C
BYP
The midrail bypass capacitor, C
startup or recovery from shutdown mode, C
, is the most critical capacitor and serves several important functions. During
BYP
determines the rate at which the amplifier starts up. The second
BYP
function is to reduce noise produced by the power supply caused by coupling into the output drive signal. This
noise is from the midrail generation circuit internal to the amplifier, which appears as degraded PSRR and
THD+N.
Bypass capacitor, C
for the best THD and noise performance.
, values of 0.47 µF to 1 µF ceramic or tantalum low-ESR capacitors are recommended
BYP
19
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
APPLICATION INFORMATION
output coupling capacitor, C
C
In the typical single-supply SE configuration, an output coupling capacitor (C ) is required to block the dc bias
C
at the output of the amplifier thus preventing dc currents in the load. As with the input coupling capacitor, the
output coupling capacitor and impedance of the load form a high-pass filter governed by equation 4.
–3 dB
1
fc(high)
(4)
2 R C
L
C
f
c
Themaindisadvantage, fromaperformancestandpoint, istheloadimpedancesaretypicallysmall, whichdrives
the low-frequency corner higher, degrading the bass response. Large values of C are required to pass low
C
frequencies into the load. Consider the example where a C of 330 µF is chosen and loads vary from 3 Ω,
C
4 Ω, 8 Ω, 32 Ω, 10 kΩ, and 47 kΩ. Table 2 summarizes the frequency response characteristics of each
configuration.
Table 2. Common Load Impedances Vs Low Frequency Output Characteristics in SE Mode
R
C
Lowest Frequency
161 Hz
L
C
3 Ω
330 µF
330 µF
330 µF
330 µF
330 µF
330 µF
4 Ω
8 Ω
120 Hz
60 Hz
32 Ω
10,000 Ω
47,000 Ω
15 Hz
0.05 Hz
0.01 Hz
As Table 2 indicates, most of the bass response is attenuated into a 4-Ω load, an 8-Ω load is adequate,
headphone response is good, and drive into line level inputs (a home stereo for example) is exceptional.
using low-ESR capacitors
Low-ESR capacitors are recommended throughout this applications section. A real (as opposed to ideal)
capacitor can be modeled simply as a resistor in series with an ideal capacitor. The voltage drop across this
resistor minimizes the beneficial effects of the capacitor in the circuit. The lower the equivalent value of this
resistance the more the real capacitor behaves like an ideal capacitor.
20
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
APPLICATION INFORMATION
bridged-tied load versus single-ended mode
Figure 33 shows a Class-AB audio power amplifier (APA) in a BTL configuration. The TPA0242 BTL amplifier
consists of two Class-AB amplifiers driving both ends of the load. There are several potential benefits to this
differential drive configuration, but, initially consider power to the load. The differential drive to the speaker
means that as one side is slewing up, the other side is slewing down, and vice versa. This in effect doubles the
voltage swing on the load as compared to a ground referenced load. Plugging 2 × V
equation, where voltage is squared, yields 4× the output power from the same supply rail and load impedance
into the power
O(PP)
(see equation 5).
V
O(PP)
(5)
V
(rms)
2 2
2
V
(rms)
Power
R
L
V
DD
V
O(PP)
2x V
R
O(PP)
L
V
DD
–V
O(PP)
Figure 33. Bridge-Tied Load Configuration
In a typical computer sound channel operating at 5 V, bridging raises the power into an 8-Ω speaker from a
singled-ended (SE, ground reference) limit of 250 mW to 1 W. In sound power that is a 6-dB improvement —
which is loudness that can be heard. In addition to increased power there are frequency response concerns.
Consider the single-supply SE configuration shown in Figure 34. A coupling capacitor is required to block the
dc offset voltage from reaching the load. These capacitors can be quite large (approximately 33 µF to 1000 µF)
so they tend to be expensive, heavy, occupy valuable PCB area, and have the additional drawback of limiting
low-frequency performance of the system. This frequency limiting effect is due to the high pass filter network
created with the speaker impedance and the coupling capacitance and is calculated with equation 6.
1
(6)
f
(c)
2 R C
L
C
21
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
APPLICATION INFORMATION
For example, a 68-µF capacitor with an 8-Ω speaker would attenuate low frequencies below 293 Hz. The BTL
configuration cancels the dc offsets, which eliminates the need for the blocking capacitors. Low-frequency
performance is then limited only by the input network and speaker response. Cost and PCB space are also
minimized by eliminating the bulky coupling capacitor.
V
DD
–3 dB
V
O(PP)
C
C
V
O(PP)
R
L
f
c
Figure 34. Single-Ended Configuration and Frequency Response
Increasing power to the load does carry a penalty of increased internal power dissipation. The increased
dissipation is understandable considering that the BTL configuration produces 4× the output power of the SE
configuration. Internal dissipation versus output power is discussed further in the crest factor and thermal
considerations section.
single-ended operation
In SE mode (see Figure 33 and Figure 34), the load is driven from the primary amplifier output for each channel
(OUT+, terminals 21 and 4).
The amplifier switches single-ended operation when the SE/BTL terminal is held high. This puts the negative
outputs in a high-impedance state, and reduces the amplifier’s gain by 6 dB.
input MUX operation
The input MUX allows two separate inputs to be applied to the amplifier. This allows the designer to choose
which input is active independent of the state of the SE/BTL terminal. When the HP/LINE terminal is held high,
the headphone inputs are active. When the HP/LINE terminal is held low, the line BTL inputs are active.
BTL amplifier efficiency
Class-AB amplifiers are notoriously inefficient. The primary cause of these inefficiencies is voltage drop across
the output stage transistors. There are two components of the internal voltage drop. One is the headroom or
dc voltage drop that varies inversely to output power. The second component is due to the sinewave nature of
the output. The total voltage drop can be calculated by subtracting the RMS value of the output voltage from
V
.TheinternalvoltagedropmultipliedbytheRMSvalueofthesupplycurrent,I rms,determinestheinternal
DD
DD
power dissipation of the amplifier.
An easy-to-use equation to calculate efficiency starts out as being equal to the ratio of power from the power
supply to the power delivered to the load. To accurately calculate the RMS and average values of power in the
load and in the amplifier, the current and voltage waveform shapes must first be understood (see Figure 35).
22
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
APPLICATION INFORMATION
I
V
O
DD
I
DD(avg)
V
(LRMS)
Figure 35. Voltage and Current Waveforms for BTL Amplifiers
Although the voltages and currents for SE and BTL are sinusoidal in the load, currents from the supply are very
different between SE and BTL configurations. In an SE application the current waveform is a half-wave rectified
shape, whereas in BTL it is a full-wave rectified waveform. This means RMS conversion factors are different.
Keep in mind that for most of the waveform both the push and pull transistors are not on at the same time, which
supports the fact that each amplifier in the BTL device only draws current from the supply for half the waveform.
The following equations are the basis for calculating amplifier efficiency.
P
L
Efficiency of a BTL amplifier
(7)
P
SUP
Where:
P
2
L
2
V rms
L
V
V
P
2R
P
, andV
, therefore, P
L
L
LRMS
R
2
L
2V
V
V
P
1
P
1
P
[cos(t)]
P
V
I
avg
P
I
avg
DD
sin(t) dt
and
and
0
SUP
DD DD
R
L
R
R
L
L
0
Therefore,
2 V
V
DD
R
P
SUP
L
substituting P and P
into equation 7,
L
SUP
2
V
P
P = Power delivered to load
L
SUP
LRMS
P
V
= Power drawn from power supply
= RMS voltage on BTL load
2 R
V
L
P
Efficiency of a BTL amplifier
Where:
4 V
2 V
V
P
DD
DD
R
R = Load resistance
L
V = Peak voltage on BTL load
P
L
I
avg = Average current drawn from
the power supply
DD
V
2 P R
L L
V
= Power supply voltage
= Efficiency of a BTL amplifier
P
DD
η
BTL
Therefore,
2 P
R
L
L
(8)
BTL
4 V
DD
23
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
APPLICATION INFORMATION
Table 3 employs equation 8 to calculate efficiencies for four different output power levels. Note that the efficiency
of the amplifier is quite low for lower power levels and rises sharply as power to the load is increased resulting
in a nearly flat internal power dissipation over the normal operating range. Note that the internal dissipation at
full output power is less than in the half power range. Calculating the efficiency for a specific system is the key
to proper power supply design. For a stereo 1-W audio system with 8-Ω loads and a 5-V supply, the maximum
draw on the power supply is almost 3.25 W.
Table 3. Efficiency Vs Output Power in 5-V 8-Ω BTL Systems
Output Power
(W)
Efficiency
(%)
Peak Voltage
(V)
Internal Dissipation
(W)
0.25
0.50
1.00
1.25
31.4
44.4
62.8
70.2
2.00
2.83
4.00
0.55
0.62
0.59
0.53
†
4.47
†
High peak voltages cause the THD to increase.
A final point to remember about Class-AB amplifiers (either SE or BTL) is how to manipulate the terms in the
efficiency equation to utmost advantage when possible. Note that in equation 8, V is in the denominator. This
DD
indicates that as V
goes down, efficiency goes up.
DD
crest factor and thermal considerations
Class-AB power amplifiers dissipate a significant amount of heat in the package under normal operating
conditions. AtypicalmusicCDrequires12dBto15dBofdynamicrange, orheadroomabovetheaveragepower
output, to pass the loudest portions of the signal without distortion. In other words, music typically has a crest
factor between 12 dB and 15 dB. When determining the optimal ambient operating temperature, the internal
dissipated power at the average output power level must be used. From the TPA0242 data sheet, one can see
that when the TPA0242 is operating from a 5-V supply into a 3-Ω speaker that 4 W peaks are available.
Converting watts to dB:
P
W
4 W
1 W
P
10Log
10Log
6 dB
(9)
dB
P
ref
Subtracting the headroom restriction to obtain the average listening level without distortion yields:
6 dB – 15 dB = –9 dB (15 dB crest factor)
6 dB – 12 dB = –6 dB (12 dB crest factor)
6 dB – 9 dB = –3 dB (9 dB crest factor)
6 dB – 6 dB = 0 dB (6 dB crest factor)
6 dB – 3 dB = 3 dB (3 dB crest factor)
Converting dB back into watts:
PdB 10
P
10
P
W
ref
(10)
63 mW (18 dB crest factor)
125 mW (15 dB crest factor)
250 mW (9 dB crest factor)
500 mW (6 dB crest factor)
1000 mW (3 dB crest factor)
2000 mW (15 dB crest factor)
24
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
APPLICATION INFORMATION
This is valuable information to consider when attempting to estimate the heat dissipation requirements for the
amplifier system. Comparing the absolute worst case, which is 2 W of continuous power output with a 3 dB crest
factor, against 12 dB and 15 dB applications drastically affects maximum ambient temperature ratings for the
system. Using the power dissipation curves for a 5-V, 3-Ω system, the internal dissipation in the TPA0242 and
maximum ambient temperatures is shown in Table 4.
Table 4. TPA0242 Power Rating, 5-V, 3-Ω, Stereo
PEAK OUTPUT POWER
(W)
POWER DISSIPATION
(W/Channel)
MAXIMUM AMBIENT
TEMPERATURE
AVERAGE OUTPUT POWER
4
4
4
4
4
4
2 W (3 dB)
1.7
1.6
1.4
1.1
0.8
0.6
–3°C
6°C
1000 mW (6 dB)
500 mW (9 dB)
250 mW (12 dB)
125 mW (15 dB)
63 mW (18 dB)
24°C
51°C
78°C
96°C
Table 5. TPA0242 Power Rating, 5-V, 8-Ω, Stereo
POWER DISSIPATION
AVERAGE OUTPUT POWER
MAXIMUM AMBIENT
TEMPERATURE
PEAK OUTPUT POWER
(W/Channel)
2.5 W
2.5 W
2.5 W
2.5 W
1250 mW (3 dB crest factor)
1000 mW (4 dB crest factor)
500 mW (7 dB crest factor)
250 mW (10 dB crest factor)
0.55
0.62
0.59
0.53
100°C
94°C
97°C
102°C
The maximum dissipated power, P
a 3 Ω load. As a result, this simple formula for calculating P
, is reached at a much lower output power level for an 8 Ω load than for
Dmax
may be used for an 8 Ω application:
Dmax
2
2V
DD
(11)
P
Dmax
2
R
L
However, in the case of a 3 Ω load, the P
The amplifier may therefore be operated at a higher ambient temperature than required by the P
for a 3 Ω load.
occurs at a point well above the normal operating power level.
Dmax
formula
Dmax
The maximum ambient temperature depends on the heat sinking ability of the PCB system. The derating factor
for the PWP package is shown in the dissipation rating table (see page 4). Converting this to Θ
:
JA
1
1
Θ
45°C W
(12)
JA
0.022
Derating Factor
25
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
APPLICATION INFORMATION
To calculate maximum ambient temperatures, first consider that the numbers from the dissipation graphs are
per channel so the dissipated heat needs to be doubled for two channel operation. Given Θ , the maximum
JA
allowable junction temperature, and the total internal dissipation, the maximum ambient temperature can be
calculated with the following equation. The maximum recommended junction temperature for the TPA0242 is
150°C. The internal dissipation figures are taken from the Power Dissipation vs Output Power graphs.
T
Max
T Max
Θ
P
(13)
A
J
JA
D
(
)
2
(
)
150 45 0.6
96°C 15 dB crest factor
NOTE:
Internal dissipation of 0.6 W is estimated for a 2-W system with 15 dB crest factor per channel.
Tables 4 and 5 show that for some applications no airflow is required to keep junction temperatures in the
specified range. The TPA0242 is designed with thermal protection that turns the device off when the junction
temperature surpasses 150°C to prevent damage to the IC. Tables 4 and 5 were calculated for maximum
listening volume without distortion. When the output level is reduced the numbers in the table change
significantly. Also, using 8-Ω speakers dramatically increases the thermal performance by increasing amplifier
efficiency.
SE/BTL operation
The ability of the TPA0242 to easily switch between BTL and SE modes is one of its most important cost saving
features. This feature eliminates the requirement for an additional headphone amplifier in applications where
internal stereo speakers are driven in BTL mode but external headphone or speakers must be accommodated.
Internal to the TPA0242, two separate amplifiers drive OUT+ and OUT–. The SE/BTL input (terminal 15)
controls the operation of the follower amplifier that drives LOUT– and ROUT– (terminals 9 and 16). When
SE/BTLisheldlow, theamplifierisonandtheTPA0242isintheBTLmode. WhenSE/BTLisheldhigh, theOUT–
amplifiers are in a high output impedance state, which configures the TPA0242 as an SE driver from LOUT+
and ROUT+ (terminals 4 and 21). I
is reduced by approximately one-half in SE mode. Control of the SE/BTL
DD
input can be from a logic-level CMOS source or, more typically, from a resistor divider network as shown in
Figure 36.
RHPIN
20
R
MUX
23 RLINEIN
–
ROUT+ 21
+
8
RIN
C
OUTR
V
DD
330 µF
–
ROUT– 16
SE/BTL 15
1 kΩ
+
100 kΩ
100 kΩ
Figure 36. TPA0242 Resistor Divider Network Circuit
26
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
APPLICATION INFORMATION
Using a readily available 1/8-in. (3.5 mm) stereo headphone jack, the control switch is closed when no plug is
inserted. When closed the 100-kΩ/1-kΩ divider pulls the SE/BTL input low. When a plug is inserted, the 1-kΩ
resistor is disconnected and the SE/BTL input is pulled high. When the input goes high, the OUT– amplifier is
shut down causing the speaker to mute (virtually open-circuits the speaker). The OUT+ amplifier then drives
through the output capacitor (C ) into the headphone jack.
O
PC BEEP operation
The PC BEEP input allows a system beep to be sent directly from a computer through the amplifier to the
speakerswithfewexternalcomponents. Theinputisactivatedautomatically. WhenthePCBEEPinputisactive,
both of the LINEIN and HPIN inputs are deselected and both the left and right channels are driven in BTL mode
with the signal from PC BEEP. The gain from the PC BEEP input to the speakers is fixed at 0.3 V/V and is
independent of the volume setting. When the PC BEEP input is deselected, the amplifier will return to the
previous operating mode and volume setting. Furthermore, if the amplifier is in shutdown mode, activating PC
BEEPwill take the device out of shutdown and output the PC BEEP signal, then return the amplifier to shutdown
mode.
When PCB ENABLE is held low, the amplifier will automatically switch to PC BEEP mode after detecting a valid
signal at the PC BEEP input. The preferred input signal is a square wave or pulse train with an amplitude of 1
V
or greater. To be accurately detected, the signal must have a minimum of 1 V amplitude, rise and fall times
pp
pp
of less than 0.1 µs and a minimum of 8 rising edges. When the signal is no longer detected, the amplifier will
return to its previous operating mode and volume setting.
If it is desired to ac-couple the PC BEEP input, the value of the coupling capacitor should be chosen to satisfy
the following equation:
1
C
(14)
PCB
2 ƒ
(100 k )
PCB
ThePCBEEPinputcanalsobedc-coupledtoavoidusingthiscouplingcapacitor. Thepinnormallysitsatmidrail
when no signal is present.
shutdown modes
The TPA0242 employs a shutdown mode of operation designed to reduce supply current, I , to the absolute
DD
minimum level during periods of nonuse for battery-power conservation. The SHUTDOWN input terminal
should be held high during normal operation when the amplifier is in use. Pulling SHUTDOWN low causes the
outputs to mute and the amplifier to enter a low-current state, I
unconnected because amplifier operation would be unpredictable.
= 150 µA. SHUTDOWN should never be left
DD
Table 6. HP/LINE, SE/BTL, and Shutdown Functions
†
AMPLIFIER STATE
INPUT OUTPUT
Mute
INPUTS
HP/LINE
X
SE/BTL
X
SHUTDOWN
Low
X
Low
Low
High
Line
Line
BTL
SE
Low
High
High
High
High
Low
High
High
HP
HP
BTL
SE
High
†
Inputs should never be left unconnected.
X = do not care
27
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TPA0242
STEREO 2-W AUDIO POWER AMPLIFIER
WITH DC VOLUME CONTROL AND MUX CONTROL
SLOS287 – NOVEMBER 1999
MECHANICAL DATA
PWP (R-PDSO-G**)
PowerPAD PLASTIC SMALL-OUTLINE PACKAGE
20-PIN SHOWN
0,30
0,19
0,65
20
M
0,10
11
Thermal Pad
(See Note D)
0,15 NOM
4,50
4,30
6,60
6,20
Gage Plane
1
10
0,25
A
0°–8°
0,75
0,50
Seating Plane
0,10
0,15
0,05
1,20 MAX
PINS **
14
16
20
24
28
DIM
5,10
4,90
5,10
4,90
6,60
6,40
7,90
7,70
9,80
9,60
A MAX
A MIN
4073225/E 03/97
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
C. Body dimensions do not include mold flash or protrusions.
D. Thepackagethermalperformancemaybeenhancedbybondingthethermalpadtoanexternalthermalplane.Thispadiselectrically
and thermally connected to the backside of the die and terminals 1, 12, 13, and 24. The dimensions of the thermal pad are
2.40 mm × 4.70 mm (maximum). The pad is centered on the bottom of the package.
E. Falls within JEDEC MO-153
PowerPAD is a trademark of Texas Instruments Incorporated.
28
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
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Copyright 1999, Texas Instruments Incorporated
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