TI TPA311DR

TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
D
D
Fully Specified for 3.3-V and 5-V Operation
Wide Power Supply Compatibility
2.5 V – 5.5 V
Output Power for RL = 8 Ω
– 350 mW at VDD = 5 V, BTL
– 250 mW at VDD = 5 V, SE
– 250 mW at VDD = 3.3 V, BTL
– 75 mW at VDD = 3.3 V, SE
D
D
D
D
D
D
Shutdown Control
– IDD = 7 µA at 3.3 V
– IDD = 60 µA at 5 V
BTL to SE Mode Control
Integrated Depop Circuitry
Thermal and Short-Circuit Protection
Surface Mount Packaging
– SOIC
– PowerPAD MSOP
D OR DGN PACKAGE
(TOP VIEW)
description
The TPA311 is a bridge-tied load (BTL) or
SHUTDOWN
VO –
1
8
single-ended (SE) audio power amplifier develBYPASS
GND
2
7
oped especially for low-voltage applications
SE/BTL
VDD
3
6
where internal speakers and external earphone
4
5
IN
V
O+
operation are required. Operating with a 3.3-V
supply, the TPA311 can deliver 250-mW of
continuous power into a BTL 8-Ω load at less than 1% THD+N throughout voice band frequencies. Although
this device is characterized out to 20 kHz, its operation was optimized for narrower band applications such as
cellular communications. The BTL configuration eliminates the need for external coupling capacitors on the
output in most applications, which is particularly important for small battery-powered equipment. A unique
feature of the TPA311 is that it allows the amplifier to switch from BTL to SE on the fly when an earphone drive
is required. This eliminates complicated mechanical switching or auxiliary devices just to drive the external load.
This device features a shutdown mode for power-sensitive applications with special depop circuitry to virtually
eliminate speaker noise when exiting shutdown mode and during power cycling. The TPA311 is available in an
8-pin SOIC surface-mount package and the surface-mount PowerPAD MSOP, which reduces board space by
50% and height by 40%.
VDD 6
RF
VDD/2
Audio
Input
RI
4
IN
2
BYPASS
1
SHUTDOWN
CS
–
CI
VO+ 5
CC
+
CBF
From System Control
From HP Jack
3
SE/BTL
–
Bias
Control
VO– 8
+
350 mW
7
GND
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.
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.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
1
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
AVAILABLE OPTIONS
PACKAGED DEVICES
TA
SMALL OUTLINE†
(D)
MSOP
Symbolization
MSOP†
(DGN)
– 40°C to 85°C
TPA311D
TPA311DGN
AAB
† The D and DGN packages are available taped and reeled. To order a taped and reeled part, add
the suffix R to the part number (e.g., TPA311DR).
Terminal Functions
TERMINAL
NAME
NO.
I/O
DESCRIPTION
I
BYPASS is the tap to the voltage divider for internal mid-supply bias. This terminal should be connected
to a 0.1-µF to 1-µF capacitor when used as an audio amplifier.
BYPASS
2
GND
7
IN
4
I
IN is the audio input terminal.
SE/BTL
3
I
When SE/BTL is held low, the TPA311 is in BTL mode. When SE/BTL is held high, the TPA311 is in SE
mode.
SHUTDOWN
1
I
SHUTDOWN places the entire device in shutdown mode when held high (IDD = 60 µA, VDD = 5 V).
VDD
VO+
6
5
O
VDD is the supply voltage terminal.
VO+ is the positive output for BTL and SE modes.
VO–
8
O
VO– is the negative output in BTL mode and a high-impedance output in SE mode.
GND is the ground connection.
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 free-air temperature range, TA (see Table 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 40°C to 85°C
Operating junction temperature range, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 40°C to 150°C
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –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
D
TA ≤ 25°C
725 mW
DGN
2.14 W§
PACKAGE
DERATING FACTOR
5.8 mW/°C
TA = 70°C
464 mW
TA = 85°C
377 mW
17.1 mW/°C
1.37 W
1.11 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 Instruments Recommended
Board for PowerPAD on page 33 of the before mentioned document.
recommended operating conditions
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Supply voltage, VDD
Operating free-air temperature, TA (see Table 3)
2
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
MIN
MAX
2.5
5.5
UNIT
V
– 40
85
°C
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
electrical characteristics at specified free-air temperature, VDD = 3.3 V, TA = 25°C (unless otherwise
noted)
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PARAMETER
TEST CONDITIONS
VOO
Output offset voltage (measured differentially)
See Note 1
PSRR
Power supply rejection ratio
VDD = 3
3.2
2 V to 3
3.4
4V
IDD
Supply current (see Figure 6)
IDD(SD)
Supply current, shutdown mode (see Figure 7)
MIN
TYP
MAX
5
20
BTL mode
85
SE mode
83
UNIT
mV
dB
BTL mode
0.7
1.5
SE mode
0.35
0.75
7
50
mA
µA
NOTE 1: At 3 V < VDD < 5 V the dc output voltage is approximately VDD/2.
operating characteristics, VDD = 3.3 V, TA = 25°C, RL = 8 Ω
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PARAMETER
TEST CONDITIONS
THD = 0.5%,
BTL mode,
THD = 0.5%,
SE mode
MIN
See Figure 14
PO
Output power,
power see Note 2
THD + N
Total harmonic distortion plus
noise
PO = 250 mW,
See Figure 12
f = 20 Hz to 4 kHz,
Gain = 2,
Maximum output power bandwidth
Gain = 2,
THD = 3%,
See Figure 12
Unity-gain bandwidth
Open Loop,
See Figure 36
f = 1 kHz,
See Figure 5
CB = 1 µF,
BTL mode,
f = 1 kHz,
See Figure 3
CB = 1 µF,
SE mode,
Gain = 1,
BTL,
CB = 0.1 µF,
See Figure 42
RL = 32 Ω,
BOM
B1
Supply ripple rejection ratio
Vn
Noise output voltage
TYP
250
110
MAX
UNIT
mW
1.3%
10
kHz
1.4
MHz
71
dB
86
15
µV(rms)
NOTE 2: Output power is measured at the output terminals of the device at f = 1 kHz.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
3
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
electrical characteristics at specified free-air temperature, VDD = 5 V, TA = 25°C (unless otherwise
noted)
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PARAMETER
TEST CONDITIONS
VOO
Output offset voltage (measured differentially)
PSRR
Power supply rejection ratio
IDD
Supply current (see Figure 6)
IDD(SD)
Supply current, shutdown mode (see Figure 7)
VDD = 4
4.9
9 V to 5.1
51V
MIN
TYP
MAX
5
20
BTL mode
78
SE mode
76
UNIT
mV
dB
BTL mode
0.7
1.5
SE mode
0.35
0.75
60
100
mA
µA
operating characteristics, VDD = 5 V, TA = 25°C, RL = 8 Ω
PARAMETER
BTL mode,
THD = 0.5%,
SE mode
Total harmonic distortion plus
noise
PO = 350 mW,
See Figure 16
f = 20 Hz to 4 kHz,
Gain = 2,
Maximum output power bandwidth
Gain = 2,
THD = 2%,
See Figure 16
Unity-gain bandwidth
Open Loop,
See Figure 37
f = 1 kHz,
See Figure 5
CB = 1 µF,
BTL mode,
f = 1 kHz,
See Figure 4
CB = 1 µF,
SE mode,
Gain = 1,
BTL,
CB = 0.1 µF,
See Figure 43
RL = 32 Ω,
Output power,
power see Note 2
THD + N
Supply ripple rejection ratio
Vn
MIN
THD = 0.5%,
PO
BOM
B1
TEST CONDITIONS
Noise output voltage
See Figure 18
POST OFFICE BOX 655303
700
300
NOTE 2: Output power is measured at the output terminals of the device at f = 1 kHz.
4
TYP
• DALLAS, TEXAS 75265
MAX
UNIT
mW
1%
10
kHz
1.4
MHz
65
dB
75
15
µV(rms)
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
PARAMETER MEASUREMENT INFORMATION
VDD 6
RF
VDD/2
Audio
Input
RI
VDD
CS
1 µF
4
IN
2
BYPASS
–
CI
VO+ 5
+
CB
0.1 µF
RL = 8 Ω
–
VO– 8
+
7
1
SHUTDOWN
3
SE/BTL
GND
Bias
Control
Figure 1. BTL Mode Test Circuit
VDD 6
RF
Audio
Input
RI
VDD
CS
1 µF
VDD/2
4
IN
2
BYPASS
–
CI
VO+ 5
+
CC
330 µF
CB
0.1 µF
RL = 32 Ω
–
VO– 8
+
7
VDD
1
SHUTDOWN
3
SE/BTL
GND
Bias
Control
Figure 2. SE Mode Test Circuit
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
5
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
Table of Graphs
FIGURE
IDD
PO
Supply voltage rejection ratio
vs Frequency
Supply current
vs Supply voltage
Output power
THD + N
Vn
PD
3, 4, 5
6, 7
vs Supply voltage
8, 9
vs Load resistance
10, 11
vs Frequency
12, 13, 16, 17, 20,
21, 24, 25, 28, 29,
32, 33
vs Output power
14, 15, 18, 19, 22,
23, 26, 27, 30, 31,
34, 35
Total harmonic distortion plus noise
Open loop gain and phase
vs Frequency
36, 37
Closed loop gain and phase
vs Frequency
38, 39, 40, 41
Output noise voltage
vs Frequency
42, 43
Power dissipation
vs Output power
44, 45, 46, 47
TYPICAL CHARACTERISTICS
SUPPLY VOLTAGE REJECTION RATIO
vs
FREQUENCY
VDD = 3.3 V
RL = 8 Ω
SE
–10
–20
CB = 0.1 µF
–30
–40
–50
CB = 1 µF
–60
–70
–80
BYPASS = 1/2 VDD
–90
100
VDD = 5 V
RL = 8 Ω
SE
–10
–20
CB = 0.1 µF
–30
–40
–50
CB = 1 µF
–60
–70
BYPASS = 1/2 VDD
–80
–90
–100
20
0
Supply Voltage Rejection Ratio – dB
Supply Voltage Rejection Ratio – dB
0
SUPPLY VOLTAGE REJECTION RATIO
vs
FREQUENCY
1k
10 k 20 k
–100
20
f – Frequency – Hz
1k
f – Frequency – Hz
Figure 3
6
100
Figure 4
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
10 k 20 k
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
SUPPLY CURRENT
vs
SUPPLY VOLTAGE
SUPPLY VOLTAGE REJECTION RATIO
vs
FREQUENCY
1.1
0
RL = 8 Ω
CB = 1 µF
BTL
0.9
I DD– Supply Current – mA
–20
–30
–40
–50
VDD = 5 V
–60
–70
VDD = 3.3 V
–80
BTL
0.7
0.5
SE
0.3
0.1
–90
–0.1
–100
20
100
1k
2
10 k 20 k
3
4
5
6
VDD – Supply Voltage – V
f – Frequency – Hz
Figure 5
Figure 6
SUPPLY CURRENT (SHUTDOWN)
vs
SUPPLY VOLTAGE
90
SHUTDOWN = High
80
I DD(SD) – Supply Current – µ A
Supply Voltage Rejection Ratio – dB
–10
70
60
50
40
30
20
10
0
2
2.5
3
3.5
4
4.5
5
5.5
VDD – Supply Voltage – V
Figure 7
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
7
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
OUTPUT POWER
vs
SUPPLY VOLTAGE
OUTPUT POWER
vs
SUPPLY VOLTAGE
1000
350
THD+N 1%
BTL
THD+N 1%
SE
300
PO – Output Power – mW
PO – Output Power – mW
800
600
RL = 8 Ω
400
RL = 32 Ω
250
200
RL = 8 Ω
150
100
RL = 32 Ω
200
50
0
2
2.5
3
3.5
4
4.5
5
0
5.5
2.5
2
3
VDD – Supply Voltage – V
Figure 8
5
4.5
5.5
OUTPUT POWER
vs
LOAD RESISTANCE
800
350
THD+N = 1%
BTL
700
THD+N = 1%
SE
300
600
PO – Output Power – mW
PO – Output Power – mW
4
Figure 9
OUTPUT POWER
vs
LOAD RESISTANCE
VDD = 5 V
500
400
300
VDD = 3.3 V
200
250
200
VDD = 5 V
150
100
50
100
VDD = 3.3 V
0
8
16
24
32
40
48
56
64
0
8
14
RL – Load Resistance – Ω
20
26
32
Figure 11
POST OFFICE BOX 655303
38
44
50
RL – Load Resistance – Ω
Figure 10
8
3.5
VDD – Supply Voltage – V
• DALLAS, TEXAS 75265
56
62
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
10
VDD = 3.3 V
PO = 250 mW
RL = 8 Ω
BTL
THD+N –Total Harmonic Distortion + Noise – %
THD+N –Total Harmonic Distortion + Noise – %
10
AV = –20 V/V
1
AV = –10 V/V
AV = –2 V/V
0.1
0.01
20
100
1k
10k
20k
PO = 125 mW
0.1
PO = 250 mW
100
1k
f – Frequency – Hz
f – Frequency – Hz
Figure 12
Figure 13
10k
20k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
10
10
THD+N –Total Harmonic Distortion + Noise – %
THD+N –Total Harmonic Distortion + Noise – %
PO = 50 mW
1
0.01
20
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VDD = 3.3 V
f = 1 kHz
AV = –2 V/V
BTL
1
RL = 8 Ω
0.1
0.01
0.04
VDD = 3.3 V
RL = 8 Ω
AV = –2 V/V
BTL
0.1
0.16
0.22
0.28
0.34
0.4
f = 20 kHz
f = 10 kHz
1
f = 1 kHz
0.1
f = 20 Hz
0.01
0.01
PO – Output Power – W
VDD = 3.3 V
RL = 8 Ω
AV = –2 V/V
BTL
0.1
1
PO – Output Power – W
Figure 14
Figure 15
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
9
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
10
VDD = 5 V
PO = 350 mW
RL = 8 Ω
BTL
THD+N –Total Harmonic Distortion + Noise – %
THD+N –Total Harmonic Distortion + Noise – %
10
AV = –20 V/V
1
AV = –10 V/V
AV = –2 V/V
0.1
0.01
20
100
1k
10k
VDD = 5 V
RL = 8 Ω
AV = –2 V/V
BTL
1
PO = 175 mW
0.1
PO = 350 mW
0.01
20
20k
100
f – Frequency – Hz
20k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
10
10
THD+N –Total Harmonic Distortion + Noise – %
THD+N –Total Harmonic Distortion + Noise – %
10k
Figure 17
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VDD = 5 V
f = 1 kHz
AV = –2 V/V
BTL
1
RL = 8 Ω
0.1
0.25
0.40
0.55
0.70
0.85
1
f = 20 kHz
f = 10 kHz
1
f = 1 kHz
0.1
f = 20 Hz
VDD = 5 V
RL = 8 Ω
AV = –2 V/V
BTL
0.01
0.01
PO – Output Power – W
0.1
PO – Output Power – W
Figure 18
10
1k
f – Frequency – Hz
Figure 16
0.01
0.1
PO = 50 mW
Figure 19
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
1
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
10
THD+N –Total Harmonic Distortion + Noise – %
THD+N –Total Harmonic Distortion + Noise – %
10
VDD = 3.3 V
PO = 30 mW
RL = 32 Ω
SE
1
0.1
AV = –1 V/V
AV = –10 V/V
0.01
AV = –5 V/V
0.001
20
100
1k
10k
VDD = 3.3 V
RL = 32 Ω
AV = –1 V/V
SE
1
PO = 10 mW
0.1
0.01
PO = 15 mW
PO = 30 mW
0.001
20
20k
100
f – Frequency – Hz
Figure 20
20k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
10
10
THD+N –Total Harmonic Distortion + Noise – %
THD+N –Total Harmonic Distortion + Noise – %
10k
Figure 21
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VDD = 3.3 V
f = 1 kHz
RL = 32 Ω
AV = –1 V/V
SE
1
0.1
0.01
0.02
1k
f – Frequency – Hz
0.025
0.03
0.035
0.04
0.045
0.05
VDD = 3.3 V
RL = 32 Ω
AV = –1 V/V
SE
f = 20 kHz
1
f = 10 kHz
0.1
f = 1 kHz
f = 20 Hz
0.01
0.002
PO – Output Power – W
0.01
0.02 0.03
0.05
PO – Output Power – W
Figure 22
Figure 23
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
11
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
10
THD+N –Total Harmonic Distortion + Noise – %
THD+N –Total Harmonic Distortion + Noise – %
10
VDD = 5 V
PO = 60 mW
RL = 32 Ω
SE
1
AV = –10 V/V
0.1
AV = –5 V/V
0.01
AV = –1 V/V
0.001
20
100
1k
1
PO = 15 mW
0.1
PO = 30 mW
0.01
PO = 60 mW
0.001
20
20k
10k
VDD = 5 V
RL = 32 Ω
AV = –1 V/V
SE
100
f – Frequency – Hz
Figure 24
10
THD+N –Total Harmonic Distortion + Noise – %
THD+N –Total Harmonic Distortion + Noise – %
20k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
10
VDD = 5 V
f = 1 kHz
RL = 32 Ω
AV = –1 V/V
SE
1
0.1
0.04
0.06
0.08
0.1
0.12
0.14
f = 20 kHz
1
f = 10 kHz
f = 1 kHz
0.1
f = 20 Hz
0.01
0.002
PO – Output Power – W
VDD = 5 V
RL = 32 Ω
AV = –1 V/V
SE
0.01
PO – Output Power – W
Figure 26
12
10k
Figure 25
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
0.01
0.02
1k
f – Frequency – Hz
Figure 27
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
0.1
0.2
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
1
THD+N –Total Harmonic Distortion + Noise – %
THD+N –Total Harmonic Distortion + Noise – %
1
VDD = 3.3 V
PO = 0.1 mW
RL = 10 kΩ
SE
0.1
AV = –1 V/V
AV = –2 V/V
AV = –5 V/V
0.01
20
100
1k
10k
VDD = 3.3 V
RL = 10 kΩ
AV = –1 V/V
SE
PO = 0.05 mW
0.1
PO = 0.1 mW
0.01
20
20k
PO = 0.13 mW
100
1k
f – Frequency – Hz
Figure 28
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
VDD = 3.3 V
f = 1 kHz
RL = 10 kΩ
AV = –1 V/V
SE
THD+N –Total Harmonic Distortion + Noise – %
THD+N –Total Harmonic Distortion + Noise – %
10
0.1
0.01
0.001
50
75
100
125
20 k
Figure 29
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
1
10 k
f – Frequency – Hz
150
175
200
10
VDD = 3.3 V
RL = 10 kΩ
AV = –1 V/V
SE
1
f = 20 Hz
0.1
f = 20 kHz
0.01
f = 1 kHz
f = 10 kHz
0.001
5
PO – Output Power – µW
10
100
500
PO – Output Power – µW
Figure 30
Figure 31
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
13
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
FREQUENCY
1
THD+N –Total Harmonic Distortion + Noise – %
THD+N –Total Harmonic Distortion + Noise – %
1
VDD = 5 V
PO = 0.3 mW
RL = 10 kΩ
SE
0.1
AV = –1 V/V
AV = –2 V/V
AV = –5 V/V
0.01
20
100
1k
10k
VDD = 5 V
RL = 10 kΩ
AV = –1 V/V
SE
PO = 0.3 mW
0.1
PO = 0.2 mW
PO = 0.1 mW
0.01
20
20k
100
f – Frequency – Hz
Figure 32
THD+N –Total Harmonic Distortion + Noise – %
THD+N –Total Harmonic Distortion + Noise – %
VDD = 5 V
f = 1 kHz
RL = 10 kΩ
AV = –1 V/V
SE
0.1
0.01
125
200
275
350
425
500
10
VDD = 5 V
RL = 10 kΩ
AV = –1 V/V
SE
1
f = 20 kHz
f = 20 Hz
0.1
0.01
f = 1 kHz
f = 10 kHz
0.001
5
PO – Output Power – µW
10
100
PO – Output Power – µW
Figure 34
14
20k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
10
0.001
50
10k
Figure 33
TOTAL HARMONIC DISTORTION PLUS NOISE
vs
OUTPUT POWER
1
1k
f – Frequency – Hz
Figure 35
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
500
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
OPEN-LOOP GAIN AND PHASE
vs
FREQUENCY
40
180
VDD = 3.3 V
RL = Open
BTL
Phase
30
120
20
60
10
0
0
Phase – °
Open-Loop Gain – dB
Gain
–60
–10
–120
–20
–30
1
101
102
103
104
–180
f – Frequency – kHz
Figure 36
OPEN-LOOP GAIN AND PHASE
vs
FREQUENCY
40
180
VDD = 5 V
RL = Open
BTL
Phase
30
120
20
60
10
0
0
Phase – °
Open-Loop Gain – dB
Gain
–60
–10
–120
–20
–30
1
101
102
103
104
–180
f – Frequency – kHz
Figure 37
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
15
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
CLOSED-LOOP GAIN AND PHASE
vs
FREQUENCY
1
180
Phase
0.75
170
0.25
0
160
Gain
–0.25
150
–0.5
–0.75
140
–1
–1.25
–1.5
–1.75
–2
101
Phase – °
Closed-Loop Gain – dB
0.5
VDD = 3.3 V
RL = 8 Ω
PO = 0.25 W
CI =1 µF
BTL
102
130
103
104
105
106
120
f – Frequency – Hz
Figure 38
CLOSED-LOOP GAIN AND PHASE
vs
FREQUENCY
1
180
Phase
0.75
170
0.25
0
160
Gain
–0.25
150
–0.5
–0.75
140
–1
–1.25
–1.5
–1.75
–2
101
VDD = 5 V
RL = 8 Ω
PO = 0.35 W
CI =1 µF
BTL
102
130
103
104
105
f – Frequency – Hz
Figure 39
16
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
120
106
Phase – °
Closed-Loop Gain – dB
0.5
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
CLOSED-LOOP GAIN AND PHASE
vs
FREQUENCY
7
180
Phase
6
170
Gain
160
4
150
3
140
2
1
0
–1
–2
–3
101
VDD = 3.3 V
RL = 32 Ω
AV = –2 V/V
PO = 30 mW
CI =1 µF
CC =470 µF
SE
102
Phase – °
Closed-Loop Gain – dB
5
130
120
110
103
104
105
106
100
f – Frequency – Hz
Figure 40
CLOSED-LOOP GAIN AND PHASE
vs
FREQUENCY
7
180
Phase
6
170
Gain
160
4
150
3
140
2
1
0
–1
–2
101
VDD = 5 V
RL = 32 Ω
AV = –2 V/V
PO = 60 mW
CI =1 µF
CC =470 µF
SE
102
Phase – °
Closed-Loop Gain – dB
5
130
120
110
103
104
105
106
100
f – Frequency – Hz
Figure 41
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
17
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
OUTPUT NOISE VOLTAGE
vs
FREQUENCY
100
VDD = 3.3 V
BW = 22 Hz to 22 kHz
RL = 32 Ω
CB =0.1 µF
AV = –1 V/V
Vn – Output Noise Voltage – µ V(rms)
Vn – Output Noise Voltage – µ V(rms)
100
OUTPUT NOISE VOLTAGE
vs
FREQUENCY
VO BTL
10
VO+
1
20
100
1k
10 k
VDD = 5 V
BW = 22 Hz to 22 kHz
RL = 32 Ω
CB =0.1 µF
AV = –1 V/V
VO BTL
10
VO+
1
20
20 k
100
1k
f – Frequency – Hz
Figure 42
POWER DISSIPATION
vs
OUTPUT POWER
300
80
72
PD – Power Dissipation – mW
270
PD – Power Dissipation – mW
20 k
Figure 43
POWER DISSIPATION
vs
OUTPUT POWER
240
210
180
150
VDD = 3.3 V
RL = 8 Ω
BTL
120
0
100
200
300
RL = 8 Ω
64
56
48
40
32
24
RL = 32 Ω
16
VDD = 3.3 V
SE
8
90
400
0
0
PO – Output Power – mW
30
60
Figure 45
POST OFFICE BOX 655303
90
PO – Output Power – mW
Figure 44
18
10 k
f – Frequency – Hz
• DALLAS, TEXAS 75265
120
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
TYPICAL CHARACTERISTICS
POWER DISSIPATION
vs
OUTPUT POWER
720
180
640
160
PD – Power Dissipation – mW
PD – Power Dissipation – mW
POWER DISSIPATION
vs
OUTPUT POWER
560
480
400
320
VDD = 5 V
RL = 8 Ω
BTL
240
200
400
600
800
1000
140
120
100
80
RL = 32 Ω
VDD = 5 V
SE
60
160
0
RL = 8 Ω
1200
40
0
50
PO – Output Power – mW
100
150
200
250
300
PO – Output Power – mW
Figure 46
Figure 47
APPLICATION INFORMATION
bridge-tied load versus single-ended mode
Figure 48 shows a linear audio power amplifier (APA) in a BTL configuration. The TPA311 BTL amplifier consists
of two linear 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 × VO(PP) into the power equation, where voltage is
squared, yields 4× the output power from the same supply rail and load impedance (see equation 1).
V (rms)
+ O(PP)
2 Ǹ2
Power
+
V
V (rms)
2
(1)
RL
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
19
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
APPLICATION INFORMATION
bridge-tied load versus single-ended mode (continued)
VDD
VO(PP)
RL
2x VO(PP)
VDD
–VO(PP)
Figure 48. Bridge-Tied Load Configuration
In typical portable handheld equipment, a sound channel operating at 3.3 V and using bridging raises the power
into an 8-Ω speaker from a single-ended (SE, ground reference) limit of 62.5 mW to 250 mW. In terms of 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 49. 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), tend to be expensive, heavy, and occupy valuable PCB area. These
capacitors also 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 2.
fc
+ 2 p R1 C
(2)
L C
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.
20
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
APPLICATION INFORMATION
bridge-tied load versus single-ended mode (continued)
VDD
–3 dB
VO(PP)
CC
RL
VO(PP)
fc
Figure 49. 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 thermal considerations
section.
BTL amplifier efficiency
Linear 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 VDD.
The internal voltage drop multiplied by the RMS value of the supply current, IDDrms, determines the internal
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 values of power in the load and in
the amplifier, the current and voltage waveform shapes must first be understood (see Figure 50).
IDD
VO
IDD(RMS)
V(LRMS)
Figure 50. Voltage and Current Waveforms for BTL Amplifiers
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
21
TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
APPLICATION INFORMATION
BTL amplifier efficiency (continued)
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.
Efficiency
+ PP L
(3)
SUP
Where:
PL
V Lrms
+
V Lrms 2
RL
2
+ 2R
Vp
L
+ VǸ2P
+ VDD IDDrms + VDDp R2VP
L
2V P
I DDrms +
pR
P SUP
L
Efficiency of a BTL Configuration
p VP
+ 2V
DD
+
p
ǒ Ǔ
P LR L
2
ń
1 2
(4)
2V DD
Table 1 employs equation 4 to calculate efficiencies for three different output power levels. 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. 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.
Table 1. Efficiency Vs Output Power in 3.3-V 8-Ω BTL Systems
OUTPUT POWER
(W)
EFFICIENCY
(%)
PEAK-TO-PEAK
VOLTAGE
(V)
INTERNAL
DISSIPATION
(W)
0.125
33.6
1.41
0.26
0.25
47.6
58.3
2.00
2.45†
0.29
0.375
0.28
† High-peak voltage values cause the THD to increase.
A final point to remember about linear amplifiers (either SE or BTL) is how to manipulate the terms in the
efficiency equation to utmost advantage when possible. In equation 4, VDD is in the denominator. This indicates
that as VDD goes down, efficiency goes up.
22
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TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
APPLICATION INFORMATION
application schematic
Figure 51 is a schematic diagram of a typical handheld audio application circuit, configured for a gain of
–10 V/V.
CF
5 pF
Audio
Input
RF
50 kΩ
VDD 6
VDD
VDD/2
RI
10 kΩ
CI
0.47 µF
4
IN
2
BYPASS
–
VO+ 5
CC
330 µF
CS
1 µF
+
1 kΩ
CB
2.2 µF
–
VO– 8
+
From System Control
0.1 µF
1
SHUTDOWN
3
SE/BTL
7
GND
Bias
Control
100 kΩ
VDD
100 kΩ
Figure 51. TPA311 Application Circuit
The following sections discuss the selection of the components used in Figure 51.
component selection
gain setting resistors, RF and RI
ǒǓ
The gain for each audio input of the TPA311 is set by resistors RF and RI according to equation 5 for BTL mode.
BTL Gain
+ AV + * 2
RF
(5)
RI
BTL mode operation brings about the factor 2 in the gain equation due to the inverting amplifier mirroring the
voltage swing across the load. Given that the TPA311 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 6.
Effective Impedance
+ RRF)RRI
F
(6)
I
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TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
APPLICATION INFORMATION
component selection (continued)
As an example consider an input resistance of 10 kΩ and a feedback resistor of 50 kΩ. The BTL gain of the
amplifier would be –10 V/V and the effective impedance at the inverting terminal would be 8.3 kΩ, which is well
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, CF, of approximately 5 pF should be placed in parallel with RF when RF is greater than
50 kΩ. This, in effect, creates a low pass filter network with the cutoff frequency defined in equation 7.
–3 dB
f c(lowpass)
+ 2 p R1 C
(7)
F F
fc
For example, if RF is 100 kΩ and CF is 5 pF then fc is 318 kHz, which is well outside of the audio range.
input capacitor, CI
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, CI and RI form a high-pass filter with the corner frequency
determined in equation 8.
–3 dB
+ 2 p R1 C
f c(highpass)
(8)
I I
fc
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 8 is reconfigured as equation 9.
CI
24
+ 2 p 1R fc
(9)
I
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TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
APPLICATION INFORMATION
component selection (continued)
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. 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 VDD/2, which is likely higher
than the source dc level. It is important to confirm the capacitor polarity in the application.
power supply decoupling, CS
The TPA311 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 VDD lead, works best. For filtering
lower-frequency noise signals, a larger aluminum electrolytic capacitor of 10 µF or greater placed near the audio
power amplifier is recommended.
midrail bypass capacitor, CB
The midrail bypass capacitor, CB, is the most critical capacitor and serves several important functions. During
start-up or recovery from shutdown mode, CB determines the rate at which the amplifier starts up. 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, which appears as degraded PSRR and
THD + N. The capacitor is fed from a 250-kΩ source inside the amplifier. To keep the start-up pop as low as
possible, the relationship shown in equation 10 should be maintained, which insures the input capacitor is fully
charged before the bypass capacitor is fuly charged and the amplifier starts up.
ǒ
CB
10
250 kΩ
Ǔvǒ
RF
) RIǓ CI
1
(10)
As an example, consider a circuit where CB is 2.2 µF, CI is 0.47 µF, RF is 50 kΩ and RI is 10 kΩ. Inserting these
values into the equation 10 we get: 18.2 ≤ 35.5 which satisfies the rule. Bypass capacitor, CB, values of 0.1 µF
to 2.2 µF ceramic or tantalum low-ESR capacitors are recommended for the best THD and noise performance.
single-ended operation
In SE mode (see Figure 51), the load is driven from the primary amplifier output (VO+, terminal 5).
ǒǓ
In SE mode the gain is set by the RF and RI resistors and is shown in equation 11. Since the inverting amplifier
is not used to mirror the voltage swing on the load, the factor of 2, from equation 5, is not included.
SE Gain
+ AV + *
RF
(11)
RI
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TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
APPLICATION INFORMATION
single-ended operation (continued)
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:
ǒ
CB
10
250 kΩ
Ǔvǒ
) RIǓ CI Ơ RLCC
1
RF
1
(12)
As an example, consider a circuit where CB is 0.2.2 µF, CI is 0.47 µF, CC is 330 µF, RF is 50 kΩRL is 32 Ω, and
RI is 10 kΩ. Inserting these values into the equation 12 we get:
18.2
t 35.5 Ơ 94.7 which satisfies the rule.
output coupling capacitor, CC
In the typical single-supply 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 13.
–3 dB
f c(high pass)
+ 2 p R1 C
(13)
L C
fc
The main disadvantage, from a performance standpoint, is that the typically small load impedances drive the
low-frequency corner higher degrading the bass response. Large values of CC are required to pass low
frequencies into the load. Consider the example where a CC of 330 µF is chosen and loads vary from 8 Ω,
32 Ω, to 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
RL
8Ω
CC
330 µF
LOWEST FREQUENCY
32 Ω
330 µF
15 Hz
47,000 Ω
330 µF
0.01 Hz
60 Hz
As Table 2 indicates an 8-Ω load is adequate, earphone response is good, and drive into line level inputs (a home
stereo for example) is exceptional.
26
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TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
APPLICATION INFORMATION
SE/BTL operation
The ability of the TPA311 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 earphone amplifier in applications where
internal speakers are driven in BTL mode but external earphone or speaker must be accommodated. Internal
to the TPA311, two separate amplifiers drive VO+ and VO–. The SE/BTL input (terminal 3) controls the operation
of the follower amplifier that drives VO– (terminal 8). When SE/BTL is held low, the amplifier is on and the TPA311
is in the BTL mode. When SE/BTL is held high, the VO– amplifier is in a high output impedance state, which
configures the TPA311 as an SE driver from VO+ (terminal 5). IDD is reduced by approximately one-half in SE
mode. Control of the SE/BTL input can be from a logic-level TTL source or, more typically, from a resistor divider
network as shown in Figure 52.
4
IN
2
BYPASS
–
VO+ 5
+
1 kΩ
–
VO– 8
+
0.1 µF
1
SHUTDOWN
3
SE/BTL
CC
330 µF
7
GND
Bias
Control
100 kΩ
VDD
100 kΩ
Figure 52. TPA311 Resistor Divider Network Circuit
Using a readily available 1/8-in. (3.5 mm) mono earphone 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 VO– amplifier is
shutdown causing the BTL speaker to mute (virtually open-circuits the speaker). The VO+ amplifier then drives
through the output capacitor (CC ) into the earphone jack.
using low-ESR capacitors
Low-ESR capacitors are recommended throughout this application. 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.
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TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
APPLICATION INFORMATION
5-V versus 3.3-V operation
The TPA311 operates over a supply range of 2.5 V to 5.5 V. This data sheet provides full specifications for 5-V
and 3.3-V operation, as these are considered to be the two most common standard voltages. There are no
special considerations for 3.3-V versus 5-V operation with respect to supply bypassing, gain setting, or stability.
The most important consideration is that of output power. Each amplifier in TPA311 can produce a maximum
voltage swing of VDD – 1 V. This means, for 3.3-V operation, clipping starts to occur when VO(PP) = 2.3 V as
opposed to VO(PP) = 4 V at 5 V. The reduced voltage swing subsequently reduces maximum output power into
an 8-Ω load before distortion becomes significant.
Operation from 3.3-V supplies, as can be shown from the efficiency formula in equation 4, consumes
approximately two-thirds the supply power for a given output-power level of operation from 5-V supplies.
headroom and thermal considerations
Linear power amplifiers dissipate a significant amount of heat in the package under normal operating conditions.
A typical music CD requires 12 dB to 15 dB of dynamic headroom to pass the loudest portions without distortion
as compared with the average power output. From the TPA311 data sheet, one can see that when the TPA311
is operating from a 5-V supply into a 8-Ω speaker that 350 mW peaks are available. Converting watts to dB:
P dB
+ 10 Log
ǒǓ
ǒ
PW
P ref
Ǔ
+ 10 Log 3501 WmW
+ – 4.6 dB
Subtracting the headroom restriction to obtain the average listening level without distortion yields:
* 15 dB + * 19.6 dB (15 dB headroom)
– 4.6 dB * 12 dB + * 16.6 dB (12 dB headroom)
– 4.6 dB * 9 dB + * 13.6 dB (9 dB headroom)
– 4.6 dB * 6 dB + * 10.6 dB (6 dB headroom)
– 4.6 dB * 3 dB + * 7.6 dB (3 dB headroom)
– 4.6 dB
Converting dB back into watts:
PW
28
+ 10PdBń10 Pref
+ 11 mW (15 dB headroom)
+ 22 mW (12 dB headroom)
+ 44 mW (9 dB headroom)
+ 88 mW (6 dB headroom)
+ 175 mW (3 dB headroom)
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TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
APPLICATION INFORMATION
headroom and thermal considerations (continued)
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 350 mW of continuous power output with 0 dB
of headroom, 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, 8-Ω system, the internal dissipation in the TPA311
and maximum ambient temperatures is shown in Table 3.
Table 3. TPA311 Power Rating, 5-V, 8-Ω, BTL
MAXIMUM AMBIENT
TEMPERATURE
AVERAGE OUTPUT
POWER
POWER
DISSIPATION
(mW)
0 CFM SOIC
350
350 mW
600
46°C
114°C
350
175 mW (3 dB)
500
64°C
120°C
350
88 mW (6 dB)
380
85°C
125°C
350
44 mW (9 dB)
300
98°C
125°C
350
22 mW (12 dB)
200
115°C
125°C
350
11 mW (15 dB)
180
119°C
125°C
PEAK OUTPUT POWER
(mW)
0 CFM DGN
Table 3 shows that the TPA311 can be used to its full 350-mW rating without any heat sinking in still air up to
46°C.
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TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
MECHANICAL DATA
D (R-PDSO-G**)
PLASTIC SMALL-OUTLINE PACKAGE
14 PINS SHOWN
0.050 (1,27)
0.020 (0,51)
0.014 (0,35)
14
0.010 (0,25) M
8
0.008 (0,20) NOM
0.244 (6,20)
0.228 (5,80)
0.157 (4,00)
0.150 (3,81)
Gage Plane
0.010 (0,25)
1
7
0°– 8°
A
0.044 (1,12)
0.016 (0,40)
Seating Plane
0.069 (1,75) MAX
0.010 (0,25)
0.004 (0,10)
PINS **
0.004 (0,10)
8
14
16
A MAX
0.197
(5,00)
0.344
(8,75)
0.394
(10,00)
A MIN
0.189
(4,80)
0.337
(8,55)
0.386
(9,80)
DIM
4040047 / D 10/96
NOTES: A.
B.
C.
D.
30
All linear dimensions are in inches (millimeters).
This drawing is subject to change without notice.
Body dimensions do not include mold flash or protrusion, not to exceed 0.006 (0,15).
Falls within JEDEC MS-012
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TPA311
350-mW MONO AUDIO POWER AMPLIFIER
SLOS207B – JANUARY 1998 – REVISED MARCH 2000
MECHANICAL DATA
DGN (S-PDSO-G8)
PowerPAD PLASTIC SMALL-OUTLINE PACKAGE
0,38
0,25
0,65
8
0,25 M
5
Thermal Pad
(See Note D)
0,15 NOM
3,05
2,95
4,98
4,78
Gage Plane
0,25
1
0°– 6°
4
3,05
2,95
0,69
0,41
Seating Plane
1,07 MAX
0,15
0,05
0,10
4073271/A 04/98
NOTES: A.
B.
C.
D.
All linear dimensions are in millimeters.
This drawing is subject to change without notice.
Body dimensions include mold flash or protrusions.
The package thermal performance may be enhanced by attaching an external heat sink to the thermal pad.
This pad is electrically and thermally connected to the backside of the die and possibly selected leads.
E. Falls within JEDEC MO-187
PowerPAD is a trademark of Texas Instruments.
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31
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