TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
D
300-mW Stereo Output
D
PC Power Supply Compatibility 5-V and
3.3-V Specified Operation
D
Shutdown Control
D
Internal Mid-Rail Generation
D
Thermal and Short-Circuit Protection
D
Surface-Mount Packaging
D
Functional Equivalent of the LM4880
description
The TP A302 is a stereo audio power amplifier capable of delivering 250 mW of continuous average power into
an 8-Ω load at less than 0.06% THD+N from a 5-V power supply or up to 300 mW at 1% THD+N. The TPA302
has high current outputs for driving small unpowered speakers at 8 Ω or headphones at 32 Ω. For headphone
applications driving 32-Ω loads, the TP A302 delivers 60 mW of continuous average power at less than 0.06%
THD+N. The amplifier features a shutdown function for power-sensitive applications as well as internal thermal
and short-circuit protection. The amplifier is available in an 8-pin SOIC (D) package that reduces board space
and facilitates automated assembly.
typical application circuit
Audio
Input
Bias
Control
6
1
5
7
VO1
VO2
V
DD
2
8
3
4
IN1
BYPASS
SHUTDOWN
VDD/2
C
I
R
I
R
F
C
B
C
S
Audio
Input
C
I
R
I
IN2
V
DD
–
+
–
+
C
C
C
C
Copyright 2000, 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.
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.
1
2
3
4
8
7
6
5
VO1
SHUTDOWN
BYPASS
IN2
IN1
GND
V
DD
VO2
D PACKAGE
(TOP VIEW)
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
AVAILABLE OPTIONS
PACKAGED DEVICES
T
A
SMALL OUTLINE
†
(D)
–40°C to 85°C TPA302D
†
The D packages are available taped and reeled. To order a taped
and reeled part, add the suffix R (e.g., TPA302DR)
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
‡
Supply voltage, VDD 6 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input voltage , VI –0.3 V to VDD + 0.3 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continuous total power dissipation Internally Limited (See Dissipation Rating Table). . . . . . . . . . . . . . . . . . . .
Operating junction temperature range, T
J
–40°C to 150° C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage temperature range, T
stg
–65°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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
TA ≤ 25°C
POWER RATING
DERATING FACTOR
ABOVE TA = 25°C
TA = 70°C
POWER RATING
TA = 85°C
POWER RATING
D 731 mW 5.8 mW/°C 460 mW 380 mW
recommended operating conditions
MIN MAX UNIT
Supply voltage, V
DD
2.7 5.5 V
Operating free-air temperature, T
A
–40 85 °C
dc electrical characteristics at specified free-air temperature, VDD = 3.3 V (unless otherwise noted)
PARAMETER TEST CONDITION MIN TYP MAX UNIT
I
DD
Supply current 2.25 5 mA
V
IO
Input offset voltage 5 20 mV
PSRR Power supply rejection ratio VDD = 3.2 V to 3.4 V 55 dB
I
DD(SD)
Quiescent current in shutdown 0.6 20 µA
ac operating characteristics, VDD = 3.3 V, TA = 25°C, RL = 8 Ω (unless otherwise noted)
PARAMETER TEST CONDITION MIN TYP MAX UNIT
THD < 0.08% 100
p
p
Gain = –1,
THD < 1% 125
POOutput power
,
f = 1 kHz
THD < 0.08%, RL = 32 Ω 25
mW
THD < 1%, RL = 32 Ω 35
B
OM
Maximum output power bandwidth Gain = 10, 1% THD 20 kHz
B
1
Unity gain bandwidth Open loop 1.5 MHz
Channel separation f = 1 kHz 75 dB
Supply ripple rejection ratio f = 1 kHz 45 dB
V
n
Noise output voltage Gain = –1 10 µVrms
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
3
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
dc electrical characteristics at specified free-air temperature, VDD = 5 V (unless otherwise noted)
PARAMETER TEST CONDITION MIN TYP MAX UNIT
I
DD
Supply current 4 10 mA
V
OO
Output offset voltage See Note 1 5 20 mV
PSRR Power supply rejection ratio VDD = 4.9 V to 5.1 V 65 dB
I
DD(SD)
Quiescent current in shutdown 0.6 µA
ac operating characteristics, VDD = 5 V, TA = 25°C, RL = 8 Ω (unless otherwise noted)
PARAMETER TEST CONDITION MIN TYP MAX UNIT
THD < 0.06% 250
p
p
Gain = –1,
THD < 1% 300
POOutput power
,
f = 1 kHz
THD < 0.06%, RL = 32 Ω 60
mW
THD < 1%, RL = 32 Ω 80
B
OM
Maximum output power bandwidth Gain = 10, 1% THD 20 kHz
B
1
Unity gain bandwidth Open loop 1.5 MHz
Channel separation f = 1 kHz 75 dB
Supply ripple rejection ratio f = 1 kHz 45 dB
V
n
Noise output voltage Gain = –1 10 µVrms
typical application
250 mW per Channel at RL = 8 Ω
60 mW per Channel at RL = 32 Ω
Stereo
RLR
L
C
C
C
C
VO1
VO2
BYPASS
IN2–
IN1–
C
B
R
F
R
F
R
I
R
I
C
I
C
I
R
L
Stereo Audio
Input
Bias
Control
From Shutdown
Control Circuit (TPA4860)
C
B
V
DD
4
3
2
1
8
6
5
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
4
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Table of Graphs
FIGURE
p
vs Frequency
1–3, 7–9,
13–15, 19–21
THD+N
Total harmonic distortion plus noise
vs Output power
4–6, 10–12
16–18, 22–24
pp
vs Supply voltage 25
IDDSupply current
yg
vs Free-air temperature 26
V
n
Output noise voltage vs Frequency 27, 28
Maximum package power dissipation vs Free-air temperature 29
Power dissipation vs Output power 30, 31
P
Omax
Maximum output power vs Free-air temperature 32, 33
p
p
vs Load resistance 34
POOutput power
vs Supply voltage 35
Open loop response 36
Closed loop response 37
Crosstalk vs Frequency 38, 39
Supply ripple rejection ratio vs Frequency 40, 41
Figure 1
1
0.1
0.010
10
20 100 1 k 10 k 20 k
THD + N – Total Harmonic Distortion Plus Noise – %
f – Frequency – Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VCC = 5 V
PO = 250 mW
RL = 8 Ω
AV = –1 V/V
VO1
VO2
Figure 2
1
0.1
0.010
10
20 100 1 k 10 k 20 k
f – Frequency – Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VCC = 5 V
PO = 250 mW
RL = 8 Ω
AV = –5 V/V
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
5
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Figure 3
1
0.1
0.010
10
20 100 1 k 10 k 20 k
f – Frequency – Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VCC = 5 V
PO = 250 mW
RL = 8 Ω
AV = –10 V/V
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 4
1
0.1
0.010
10
0.01 0.1 1
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VCC = 5 V
f = 20 Hz
RL = 8 Ω
AV = –1 V/V
PO – Output Power – W
THD + N – Total Harmonic Distortion Plus Noise – %
VO2
VO1
Figure 5
1
0.1
0.010
10
0.01 0.1 1
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VCC = 5 V
f = 1 kHz
RL = 8 Ω
AV = –1 V/V
PO – Output Power – W
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 6
1
0.1
0.010
10
0.01 0.1 1
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VCC = 5 V
f = 20 kHz
RL = 8 Ω
AV = –1 V/V
PO – Output Power – W
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
6
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Figure 7
1
0.1
0.010
10
20 100 1 k 10 k 20 k
f – Frequency – Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VCC = 5 V
PO = 60 mW
RL = 32 Ω
AV = –1 V/V
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 8
1
0.1
0.010
10
20 100 1 k 10 k 20 k
f – Frequency – Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VCC = 5 V
PO = 60 mW
RL = 32 Ω
AV = –5 V/V
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 9
1
0.1
0.010
10
20 100 1 k 10 k 20 k
f – Frequency – Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VCC = 5 V
PO = 60 mW
RL = 32 Ω
AV = –10 V/V
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 10
1
0.1
0.010
10
0.01 0.1 1
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VCC = 5 V
f = 20 Hz
RL = 32 Ω
AV = –1 V/V
PO – Output Power – W
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
7
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Figure 11
1
0.1
0.010
10
0.01 0.1 1
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VCC = 5 V
f = 1 kHz
RL = 32 Ω
AV = –1 V/V
PO – Output Power – W
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 12
1
0.1
0.010
10
0.01 0.1 1
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VCC = 5 V
f = 20 kHz
RL = 32 Ω
AV = –1 V/V
PO – Output Power – W
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 13
1
0.1
0.010
10
20 100 1 k 10 k 20 k
f – Frequency – Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VCC = 3.3 V
PO = 100 mW
RL = 8 Ω
AV = –1 V/V
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 14
1
0.1
0.010
10
20 100 1 k 10 k 20 k
f – Frequency – Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VCC = 3.3 V
PO = 100 mW
RL = 8 Ω
AV = –5 V/V
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
8
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Figure 15
1
0.1
0.010
10
20 100 1 k 10 k 20 k
f – Frequency – Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VCC = 3.3 V
PO = 100 mW
RL = 8 Ω
AV = –10 V/V
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 16
1
0.1
0.010
10
0.01 0.1 1
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VCC = 3.3 V
f = 20 Hz
RL = 8 Ω
AV = –1 V/V
PO – Output Power – W
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 17
1
0.1
0.010
10
0.01 0.1 1
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VCC = 3.3 V
f = 1 kHz
RL = 8 Ω
AV = –1 V/V
PO – Output Power – W
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 18
1
0.1
0.010
10
0.01 0.1 1
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VCC = 3.3 V
f = 20 kHz
RL = 8 Ω
AV = –1 V/V
PO – Output Power – W
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
9
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Figure 19
1
0.1
0.010
10
20 100 1 k 10 k 20 k
f – Frequency – Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VCC = 3.3 V
PO = 25 mW
RL = 32 Ω
AV = –1 V/V
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 20
1
0.1
0.010
10
20 100 1 k 10 k 20 k
f – Frequency – Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VCC = 3.3 V
PO = 25 mW
RL = 32 Ω
AV = –5 V/V
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 21
1
0.1
0.010
10
20 100 1 k 10 k 20 k
f – Frequency – Hz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
VCC = 3.3 V
PO = 25 mW
RL = 32 Ω
AV = –10 V/V
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 22
1
0.1
0.010
10
0.01 0.1 1
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VCC = 3.3 V
f = 20 Hz
RL = 32 Ω
AV = –1 V/V
PO – Output Power – W
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
10
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Figure 23
1
0.1
0.010
10
0.01 0.1 1
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VCC = 3.3 V
f = 1 kHz
RL = 32 Ω
AV = –1 V/V
PO – Output Power – W
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 24
1
0.1
0.010
10
0.01 0.1 1
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VCC = 3.3 V
f = 20 kHz
RL = 32 Ω
AV = –1 V/V
PO – Output Power – W
THD + N – Total Harmonic Distortion Plus Noise – %
VO1
VO2
Figure 25
3
2.5
1.5
1
2.5 3 3.5 4
– Supply Current – mA
3.5
4.5
SUPPLY CURRENT
vs
SUPPLY VOLTAGE
5
4.5 5 5.5
4
2
TA = 25°C
I
DD
VDD – Supply Voltage – V
Figure 26
4
3
1
0
–50 –25 0 25
– Supply Current – mA
5
SUPPLY CURRENT DISTRIBUTION
vs
FREE-AIR TEMPERATURE
50 75 100
6
2
I
DD
TA – Free-Air Temperature – °C
Min
Min
Min
MinMin Min
Max
Max
Max
Typ
Typ
Typ
TypTyp
Typ
3.3 V 3.3 V
3.3 V
5 V
5 V
5 V
Max
Max
Max
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
11
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Figure 27
VO1
VO2
100
10
1
1000
20 100 1 k 10 k 20 k
– Output Noise Voltage –
f – Frequency – Hz
OUTPUT NOISE VOLTAGE
vs
FREQUENCY
Vµ
VCC = 5 V
V
n
Figure 28
100
10
1
1000
20 100 1 k 10 k 20 k
f – Frequency – Hz
OUTPUT NOISE VOLTAGE
vs
FREQUENCY
VCC = 3.3 V
– Output Noise Voltage –
Vµ
V
n
Figure 29
0.5
0.25
0
–25 0 25 50 75 100
Maximum Package Power Dissipation – W
0.75
MAXIMUM PACKAGE POWER DISSIPATION
vs
FREE-AIR TEMPERATURE
1
125 150 175
TA – Free-Air Temperature – °C
Figure 30
0.25
0
0 0.25
Power Dissipation – W
0.5
POWER DISSIPATION
vs
OUTPUT POWER
0.75
0.5 0.75
VDD = 5 V
RL = 8 Ω
RL = 16 Ω
PO – Output Power – W
Two Channels Active
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
12
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Figure 31
0.1
0
0 0.1
Power Dissipation – W
0.2
POWER DISSIPATION
vs
OUTPUT POWER
0.3
0.2 0.35
RL = 8 Ω
RL = 16 Ω
PO – Output Power – W
VDD = 3.3 V
Two Channels Active
0.25
0.15
0.05
0.05 0.15 0.25 0.3
Figure 32
RL = 8 Ω
RL = 16 Ω
VDD = 5 V
Two Channels Active
80
60
40
20
0 0.25
120
140
160
0.5 0.75
100
POmax – Maximum Output Power – W
– Free-Air Temperature –
T
A
°C
MAXIMUM OUTPUT POWER
vs
FREE-AIR TEMPERATURE
Figure 33
RL = 8Ω
RL = 16Ω
VDD = 3.3 V
Two Channels Active
120
110
100
130
140
150
0.075 0.2250
0.15
MAXIMUM OUTPUT POWER
vs
FREE-AIR TEMPERATURE
P
Omax
– Maximum Output Power – W
– Free-Air Temperature –
T
A
°C
Figure 34
200
150
50
0
51015202530
– Output Power – mW
300
350
OUTPUT POWER
vs
LOAD RESISTANCE
400
35 40 45 50
VDD = 5 V
VDD = 3.3 V
250
100
RL – Load Resistance – Ω
P
O
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
13
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Figure 35
VDD – Supply Voltage – V
THD = 1%
250
150
100
50
2.5 3 3.5 4
300
350
OUTPUT POWER
vs
SUPPLY VOLTAGE
450
4.5 5 5.5
400
200
– Output Power – mW
P
O
0
RL = 8 Ω
RL = 32 Ω
Figure 36
30
10
0
–10
10 100 1 k 10 k 100 k
Gain – dB
40
50
f – Frequency – Hz
OPEN LOOP RESPONSE
70
1 M 10 M 100 M
60
20
20°
0°
–20°
–40°
–60°
–80°
–100°
Phase
Gain
Phase
Figure 37
–60
10
Gain – dB
f – Frequency – Hz
CLOSED LOOP RESPONSE
20
100 M
200°
–200°
Phase
0
–20
–40
100°
0°
–100°
100 1 k 10 k 100 k 1 M 10 M
Phase
Gain
Figure 38
–50
–60
–80
–90
–100
0
–70
10 100 1 k 10 k 100 k
Crosstalk – dB
–30
–40
–10
f – Frequency – Hz
CROSSTALK
vs
FREQUENCY
–20
VDD = 5 V
V02 to V01
(b to a)
V01 to V02
(a to b)
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
14
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TYPICAL CHARACTERISTICS
Figure 39
– 50
– 60
– 80
– 90
– 100
0
– 70
10 100 1 k 10 k 100 k
Crosstalk – dB
– 30
– 40
– 10
f – Frequency – Hz
CROSSTALK
vs
FREQUENCY
– 20
VDD = 3.3 V
V02 to V01
(b to a)
V01 to VO2
(a to b)
Figure 40
– 50
– 60
– 80
– 90
– 100
0
– 70
100 1 k 10 k 20 k
Supply Ripple Rejection Ratio – dB
– 30
– 40
– 10
f – Frequency – Hz
SUPPLY RIPPLE REJECTION RATIO
vs
FREQUENCY
– 20
VDD = 5 V
VO2
VO1
Figure 41
– 50
– 60
– 80
– 90
– 100
0
– 70
100 1 k 10 k 20 k
– 30
– 40
– 10
f – Frequency – Hz
SUPPLY RIPPLE REJECTION RATIO
vs
FREQUENCY
– 20
VDD = 3.3 V
VO2
VO1
Supply Ripple Rejection Ratio – dB
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
15
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
selection of components
Figure 42 is a schematic diagram of a typical application circuit.
Audio
Input
Bias
Control
VDD = 5 V
6
1
5
7
VO1
VO2
V
DD
2
8
3
4
IN1
BYPASS
SHUTDOWN (see Note A)
VDD/2
C
I
R
I
R
F
C
F
50 kΩ 50 kΩ
C
B
C
S
NOTE A: SHUTDOWN must be held low for normal operation and asserted high for shutdown mode.
Audio
Input
C
I
R
I
IN2
R
F
C
F
R
L
R
L
C
C
C
C
Figure 42. TPA302 Typical Notebook Computer Application Circuit
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
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POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
gain setting resistors, RF and R
I
The gain for the TPA302 is set by resistors RF and RI according to equation 1.
(1)
Gain
+*
ǒ
R
F
R
I
Ǔ
Given that the TPA302 is a MOS amplifier, the input impedance is very high, consequently input leakage
currents are not generally a concern although noise in the circuit increases as the value of RF increases. In
addition, a certain range of RF values is required for proper start-up operation of the amplifier. Taken together
it is recommended that the effective impedance seen by the inverting node of the amplifier be set between 5
kΩ and 20 kΩ. The effective impedance is calculated in equation 2.
(2)
Effective Impedance
+
R
FRI
RF)
R
I
As an example, consider an input resistance of 10 kΩ and a feedback resistor of 50 kΩ. The gain of the amplifier
would be – 5 and the effective impedance at the inverting terminal would be 8.3 kΩ, which is within the
recommended range.
For high performance applications metal film resistors are recommended because they tend to have lower noise
levels than carbon resistors. For values of RF above 50 kΩ the amplifier tends to become unstable due to a pole
formed from RF and the inherent input capacitance of the MOS input structure. For this reason, a small
compensation capacitor of approximately 5 pF should be placed in parallel with RF. This, in effect, creates a
low-pass filter network with the cutoff frequency defined in equation 3.
(3)
f
c(lowpass)
+
1
2pRFC
F
For example if RF is 100 kΩ and CF is 5 pF then f
c(lowpass)
is 318 kHz, which is well outside of the audio range.
input capacitor, C
I
In the typical application an input capacitor, CI, is required to allow the amplifier to bias the input signal to the
proper dc level for optimum operation. In this case, C
I
and RI form a high-pass filter with the corner frequency
determined in equation 4.
(4)
f
c(highpass)
+
1
2pR
I
C
I
The value of CI is important to consider as it directly affects the bass (low frequency) performance of the circuit.
Consider the example where RI is 10 kΩ and the specification calls for a flat bass response down to 40 Hz.
Equation 4 is reconfigured as equation 5.
(5)
C
I
+
1
2pR
I
f
c(highpass)
In this example, CI is 0.40 µF so one would likely choose a value in the range of 0.47 µF to 1 µF. A further
consideration for this capacitor is the leakage path from the input source through the input network (RI, CI) and
the feedback resistor (RF) 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 (> 10). 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
DD
/2, which is likely
higher than the source dc level. Please note that it is important to confirm the capacitor polarity in the application.
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
17
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
power supply decoupling, C
S
The TP A302 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling to
ensure that 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
DD
lead, works best. For
filtering lower-frequency noise signals, a larger aluminum electrolytic capacitor of 10 µF or greater placed near
the power amplifier is recommended.
midrail bypass capacitor, C
B
The midrail bypass capacitor, CB, serves several important functions. During startup or recovery from shutdown
mode, CB determines the rate at which the amplifier starts up. This helps to push the start-up pop noise into
the subaudible range (so low it can not be heard). The second 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. The capacitor is fed from a 25-kΩ source inside the amplifier. To keep the start-up pop as low
as possible, the relationship shown in equation 6 should be maintained.
(6)
1
ǒ
CB
25 kΩ
Ǔ
v
1
ǒ
CIR
I
Ǔ
As an example, consider a circuit where CB is 0.1 µF, CI is 0.22 µF and RI is 10 kΩ. Inserting these values into
the equation 9 results in: 400 ≤ 454 which satisfies the rule. Bypass capacitor, CB, values of 0.1 µF to 1 µF
ceramic or tantalum low-ESR capacitors are recommended for the best THD and noise performance.
output coupling capacitor, C
C
In the typical single-supply single-ended (SE) configuration, an output coupling capacitor (CC) is required to
block the dc bias 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 7.
(7)
f
c
+
1
2pR
L
C
C
The main disadvantage, from a performance standpoint, is that the load impedances are typically small, which
drives the low-frequency corner higher. Large values of C
C
are required to pass low frequencies into the load.
Consider the example where a CC of 68 µF is chosen and loads vary from 8 Ω, 32 Ω, and 47 kΩ. Table 1
summarizes the frequency response characteristics of each configuration.
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
18
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
Table 1. Common Load Impedances vs Low Frequency Output Characteristics in SE Mode
R
L
C
C
LOWEST FREQUENCY
8 Ω 68 µF 293 Hz
32 Ω 68 µF
73 Hz
47,000 Ω 68 µF 0.05 Hz
As Table 1 indicates, most of the bass response is attenuated into 8-Ω loads while headphone response is
adequate and drive into line level inputs (a home stereo for example) is very good.
The output coupling capacitor required in single-supply SE mode also places additional constraints on the
selection of other components in the amplifier circuit. The rules described earlier still hold with the addition of
the following relationship:
(8)
1
ǒ
CB
25 kΩ
Ǔ
v
1
ǒ
CIR
I
Ǔ
Ơ
1
RLC
C
shutdown mode
The TPA302 employs a shutdown mode of operation designed to reduce quiescent supply current, I
DD(q)
, to
the absolute minimum level during periods of nonuse for battery-power conservation. For example, during
device sleep modes or when other audio-drive currents are used (i.e., headphone mode), the speaker drive is
not required. The SHUTDOWN input terminal should be held low during normal operation when the amplifier
is in use. Pulling SHUTDOWN high causes the outputs to mute and the amplifier to enter a low-current state,
I
DD
< 1 µA. SHUTDOWN should never be left unconnected because amplifier operation would be unpredictable.
using low-ESR capacitors
Low-ESR capacitors are recommended throughout this applications section. A real 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.
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
19
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
thermal considerations
A prime consideration when designing an audio amplifier circuit is internal power dissipation in the device. The
curve in Figure 43 provides an easy way to determine what output power can be expected out of the TP A302
for a given system ambient temperature in designs using 5-V supplies. This curve assumes no forced airflow
or additional heat sinking.
RL = 8 Ω
RL = 16 Ω
VDD = 5 V
Two Channels Active
80
60
40
20
0 0.25
– Free-Air Temperature –
120
140
160
0.5 0.75
100
POmax – Maximum Output Power – W
C
°T
A
Figure 43. Free-Air Temperature Versus Maximum Output Power
5-V versus 3.3-V operation
The TPA302 was designed for operation over a supply range of 2.7 V to 5.5 V. This data sheet provides full
specifications for 5-V and 3.3-V operation since are considered to be the two most common standard voltages.
There are no special considerations for 3.3-V versus 5-V operation as far as supply bypassing, gain setting, or
stability. Supply current is slightly reduced from 3.5 mA (typical) to 2.5 mA (typical). The most important
consideration is that of output power. Each amplifier in the TPA302 can produce a maximum voltage swing of
V
DD
– 1 V. This means, for 3.3-V operation, clipping starts to occur when V
O(PP)
= 2.3 V as opposed when
V
O(PP)
= 4 V while operating at 5 V . The reduced voltage swing subsequently reduces maximum output power
into the load before distortion begins to become significant.
TPA302
300-mW STEREO AUDIO POWER AMPLIFIER
SLOS174B – JANUARY 1997 – REVISE MARCH 2000
20
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
MECHANICAL INFORMATION
D (R-PDSO-G**) PLASTIC SMALL-OUTLINE PACKAGE
14 PINS SHOWN
4040047/D 10/96
0.228 (5,80)
0.244 (6,20)
0.069 (1,75) MAX
0.010 (0,25)
0.004 (0,10)
1
14
0.014 (0,35)
0.020 (0,51)
A
0.157 (4,00)
0.150 (3,81)
7
8
0.044 (1,12)
0.016 (0,40)
Seating Plane
0.010 (0,25)
PINS **
0.008 (0,20) NOM
A MIN
A MAX
DIM
Gage Plane
0.189
(4,80)
(5,00)
0.197
8
(8,55)
(8,75)
0.337
14
0.344
(9,80)
16
0.394
(10,00)
0.386
0.004 (0,10)
M
0.010 (0,25)
0.050 (1,27)
0°–8°
NOTES: B. All linear dimensions are in inches (millimeters).
C. This drawing is subject to change without notice.
D. Body dimensions do not include mold flash or protrusion, not to exceed 0.006 (0,15).
E. Falls within JEDEC MS-012
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