TI TPA6110A2DGN

TPA6110A2
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SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
150-mW STEREO AUDIO POWER AMPLIFIER
FEATURES
•
•
•
•
•
•
•
DGN PACKAGE
(TOP VIEW)
150 mW Stereo Output
PC Power Supply Compatible
– Fully Specified for 3.3 V and 5 V
Operation
– Operation to 2.5 V
Pop Reduction Circuitry
Internal Mid-Rail Generation
Thermal and Short-Circuit Protection
Surface-Mount Packaging
– PowerPAD™ MSOP
Pin Compatible With LM4881
BYPASS
GND
SHUTDOWN
IN2–
1
8
2
7
3
6
4
5
IN1–
VO1
VDD
VO2
DESCRIPTION
The TPA6110A2 is a stereo audio power amplifier packaged in an 8-pin PowerPAD™ MSOP package capable of
delivering 150 mW of continuous RMS power per channel into 16-Ω loads. Amplifier gain is externally configured
by means of two resistors per input channel and does not require external compensation for settings of 1 to 10.
THD+N when driving a 16-Ω load from 5 V is 0.03% at 1 kHz, and less than 1% across the audio band of 20 Hz
to 20 kHz. For 32-Ω loads, the THD+N is reduced to less than 0.02% at 1 kHz, and is less than 1% across the
audio band of 20 Hz to 20 kHz. For 10-kΩ loads, the THD+N performance is 0.005% at 1 kHz, and less than
0.5% across the audio band of 20 Hz to 20 kHz.
TYPICAL APPLICATION CIRCUIT
325 kΩ
325 kΩ
VDD 6
VDD
Rf
Audio
Input
C(S)
VDD/2
Ri
Ci
8
IN 1−
1
BYPASS
4
IN 2−
−
+
VO1 7
−
+
VO2 5
C(C)
C(B)
Audio
Input
Ri
Ci
3
From Shutdown
Control Circuit
SHUTDOWN
C(C)
Bias
Control
2
Rf
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.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2000–2004, Texas Instruments Incorporated
TPA6110A2
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SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
These devices have limited built-in ESD protection. The leads should be shorted together or the device
placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
AVAILABLE OPTIONS
PACKAGED DEVICE
TA
-40°C to 85°C
(1)
MSOP SYMBOLIZATION
MSOP (1)
TPA6110A2DGN
TI AIZ
The DGN package is available inleft-ended tape and reel only (e.g., TPA6110A2DGNR).
Terminal Functions
TERMINAL
NAME
NO.
I/O
DESCRIPTION
BYPASS
1
I
Tap to voltage divider for internal mid-supply bias supply. Connect to a 0.1 µF to 1 µF low ESR capacitor
for best performance.
GND
2
I
GND is the ground connection.
IN1–
8
I
IN1– is the inverting input for channel 1.
IN2–
4
I
IN2– is the inverting input for channel 2.
SHUTDOWN
3
I
Puts the device in a low quiescent current mode when held high.
VDD
6
I
VDD is the supply voltage terminal.
VO1
7
O
VO1 is the audio output for channel 1.
VO2
5
O
VO2 is the audio output for channel 2.
ABSOLUTE MAXIMUM RATINGS (1)
over operating free-air temperature range (unless otherwise noted)
UNIT
VDD
Supply voltage
VI
Input voltage
6V
–0.3 V to VDD + 0.3 V
Continuous total power dissipation
Internally limited
TJ
Operating junction temperature range
-40°C to 150°C
Tstg
Storage temperature range
-65°C to 150°C
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds
(1)
260°C
Stresses beyond those listedunder "absolute maximum ratings” may cause permanent damage to thedevice. These are stress ratings
only, and functional operation of the deviceat these or any other conditions beyond those indicated under "recommendedoperating
conditions” is not implied. Exposure to absolute-maximum-ratedconditions for extended periods may affect devicereliability.
DISSIPATION RATING TABLE
(1)
2
PACKAGE
TA ≤ 25°C
POWER RATING
DERATING FACTOR
ABOVE TA = 25°C
TA = 70°C
POWER RATING
TA = 85°C
POWER RATING
DGN
2.14 W (1)
17.1 mW/°C
1.37 W
1.11 W
See the Texas Instrumentsdocument, PowerPAD Thermally EnhancedPackage Application Report (SLMA002), for more information on
thePowerPAD™ package. The thermal data was measured on a PCB layout based onthe information in the section entitled Texas
Instruments Recommended Board for PowerPAD onpage 33 of the before mentioned document.
TPA6110A2
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SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
RECOMMENDED OPERATING CONDITIONS
MIN
MAX
VDD
Supply voltage
2.5
5.5
V
TA
Operating free-air temperature
-40
85
°C
VIH
High-level input voltage (SHUTDOWN)
VIL
Low-level input voltage (SHUTDOWN)
60% x VDD
UNIT
V
25% x VDD
V
DC ELECTRICAL CHARACTERISTICS
at TA = 25°C, VDD = 2.5 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP MAX
VOO
Output offset voltage
Av = 2 V/V
PSRR
Power supply rejection ratio
VDD = 3.2 V to 3.4 V
83
IDD
Supply current
SHUTDOWN = 0 V
IDD(SD)
Supply current in shutdown mode
SHUTDOWN = VDD
UNIT
15
mV
1.5
3
mA
10
50
µA
dB
AC OPERATING CHARACTERISTICS
VDD = 3.3 V, TA = 25°C, RL = 16 Ω
PARAMETER
TEST CONDITIONS
MIN
TYP MAX
60
UNIT
PO
Output power (each channel)
THD≤ 0.1%, f = 1 kHz
mW
THD+N
Total harmonic distortion + noise
PO = 40 mW, 20 - 20 kHz
0.4%
BOM
Maximum output power BW
G = 10, THD < 5%
> 20
Phase margin
Open loop
96°
Supply ripple rejection ratio
f = 1 kHz
71
dB
Channel/channel output separation
f = 1 kHz, PO = 40 mW
89
dB
SNR
Signal-to-noise ratio
PO = 50 mW, AV = 1
Vn
Noise output voltage
AV = 1
kHz
100
dB
11
µV(rms)
DC ELECTRICAL CHARACTERISTICS
at TA = 25°C, VDD = 5.5 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP MAX
VOO
Output offset voltage
AV = 2 V/V
PSRR
Power supply rejection ratio
VDD = 4.9 V to 5.1 V
76
IDD
Supply current
SHUTDOWN = 0 V
IDD(SD)
Supply current in shutdown mode
SHUTDOWN = VDD
| IIH |
High-level input current (SHUTDOWN)
VDD = 5.5 V, VI = VDD
| IIL |
Low-level input current (SHUTDOWN)
VDD = 5.5 V, VI = 0 V
1
Zi
Input impedance
UNIT
15
mV
1.5
3
mA
60
100
µA
1
µA
>1
dB
µA
MΩ
3
TPA6110A2
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SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
AC OPERATING CHARACTERISTICS
VDD = 5 V, TA = 25°C, RL = 16 Ω
PARAMETER
TEST CONDITIONS
MIN
TYP MAX
UNIT
150
mW
PO
Output power (each channel)
THD≤ 0.1%, f = 1 kHz
THD+N
Total harmonic distortion + noise
PO = 100 mW, 20 - 20 kHz
0.6%
BOM
Maximum output power BW
G = 10, THD < 5%
> 20
Phase margin
Open loop
96°
Supply ripple rejection ratio
f = 1 kHz
61
dB
Channel/Channel output separation
f = 1 kHz, PO = 100 mW
90
dB
SNR
Signal-to-noise ratio
PO = 100 mW, AV = 1
100
dB
Vn
Noise output voltage
AV = 1
11.7
µV(rms)
kHz
AC OPERATING CHARACTERISTICS
VDD = 3.3 V, TA = 25°C, RL = 32 Ω
PARAMETER
TEST CONDITIONS
PO
Output power (each channel)
THD≤ 0.1%, f = 1 kHz
MIN
TYP MAX
THD+N
Total harmonic distortion + noise
PO = 30 mW, 20 - 20 kHz
0.4%
BOM
Maximum output power BW
AV = 10, THD < 2%
> 20
Phase margin
Open loop
96°
Supply ripple rejection ratio
f = 1 kHz
71
dB
Channel/channel output separation
f = 1 kHz
95
dB
SNR
Signal-to-noise ratio
PO = 40 mW, AV = 1
Vn
Noise output voltage
AV = 1
40
UNIT
mW
kHz
100
dB
11
µV(rms)
AC OPERATING CHARACTERISTICS
VDD = 5 V, TA = 25°C, RL = 32 Ω
PARAMETER
TEST CONDITIONS
PO
Output power (each channel)
THD≤ 0.1%, f = 1 kHz
MIN
TYP MAX
THD+N
Total harmonic distortion + noise
PO = 60 mW, 20 - 20 kHz
0.4%
BOM
Maximum output power BW
AV = 10, THD < 2%
> 20
Phase margin
Open loop
97°
Supply ripple rejection ratio
f = 1 kHz
61
dB
98
dB
90
UNIT
mW
kHz
Channel/channel output separation
f = 1 kHz
SNR
Signal-to-noise ratio
PO = 90 mW, AV = 1
100
dB
Vn
Noise output voltage
AV = 1
11.7
µV(rms)
4
TPA6110A2
www.ti.com
SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
TYPICAL CHARACTERISTICS
Table of Graphs
FIGURE
THD+N
Vn
vs Frequency
Total harmonic distortion plus noise
1, 3, 5, 6, 7, 9, 11, 13
vs Output power
2, 4, 8, 10, 12, 14
Supply ripple rejection ratio
vs Frequency
15, 16
Output noise voltage
vs Frequency
17, 18
Crosstalk
vs Frequency
19–24
Shutdown attenuation
vs Frequency
25, 26
Open-loop gain and phase margin
vs Frequency
27, 28
Output power
vs Load resistance
29, 30
IDD
Supply current
vs Supply voltage
31
SNR
Signal-to-noise ratio
vs Voltage gain
32
Power dissipation/amplifier
vs Load power
33, 34
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION + NOISE
vs
OUTPUT POWER
10
1
VDD = 3.3 V,
PO = 25 mW,
CB = 1 µF,
RL = 32 Ω,
AV = −1 V/V
THD+N − Total Harmonic Distortion + Noise − %
THD+N − Total Harmonic Distortion + Noise − %
10
0.1
0.01
0.001
20
100
1k
10k 20k
1
VDD = 3.3 V,
RL = 32 Ω,
AV = −1 V/V,
CB = 1 µF
20 kHz
20 Hz
0.1
1 kHz
0.01
0.001
10
50
f − Frequency − Hz
PO − Output Power − mW
Figure 1.
Figure 2.
100
5
TPA6110A2
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SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
1
10
VDD = 5 V,
PO = 60 mW,
CB = 1 µF,
RL = 32 Ω,
THD+N − Total Harmonic Distortion + Noise − %
THD+N − Total Harmonic Distortion + Noise − %
10
AV = −5 V/V
AV = −1 V/V
AV = −10 V/V
0.1
0.05
0.01
0.001
20
100
TOTAL HARMONIC DISTORTION + NOISE
vs
OUTPUT POWER
1k
f − Frequency − Hz
1 kHz
0.01
100
500
Figure 4.
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
10
THD+N − Total Harmonic Distortion + Noise − %
THD+N − Total Harmonic Distortion + Noise − %
0.1
Figure 3.
VDD = 3.3 V,
PO = 100 mW,
CB = 1 µF,
RL = 10 kΩ,
AV = −1 V/V
0.01
100
1k
f − Frequency − Hz
Figure 5.
6
20 kHz
PO − Output Power − mW
0.1
0.001
20
20 Hz
0.001
10
10k 20k
10
1
1
VDD = 5 V,
RL = 32 Ω,
AV = −1 V/V,
CB = 1 µF
10k 20k
1
VDD = 5 V,
PO = 100 mW,
CB = 1 µF,
RL = 10 kΩ
AV = −5 V/V
AV = −1 V/V
0.1
AV = −10 V/V
0.01
0.001
20
100
1k
f − Frequency − Hz
Figure 6.
10k 20k
TPA6110A2
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SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION + NOISE
vs
OUTPUT POWER
1
10
THD+N − Total Harmonic Distortion + Noise − %
THD+N − Total Harmonic Distortion + Noise − %
10
VDD = 3.3 V,
PO = 60 mW,
CB = 1 µF,
RL = 8 Ω,
AV = −1 V/V
0.1
0.01
0.001
20
100
1k
f − Frequency − Hz
0.01
100
Figure 8.
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION + NOISE
vs
OUTPUT POWER
500
10
VDD = 5 V,
PO = 150 mW,
CB = 1 µF,
RL = 8 Ω
THD+N − Total Harmonic Distortion + Noise − %
THD+N − Total Harmonic Distortion + Noise − %
1 kHz
Figure 7.
AV = −5 V/V
0.1
0.001
20
20 kHz
0.1
PO − Output Power − mW
AV = −1 V/V
0.01
20 Hz
0.001
10
10k 20k
10
1
1
VDD = 3.3 V,
RL = 8 Ω,
AV = −1 V/V,
CB = 1 µF
AV = −10 V/V
100
1k
f − Frequency − Hz
Figure 9.
10k 20k
1
VDD = 5 V,
RL = 8 Ω,
AV = −1 V/V,
CB = 1 µF
1 kHz
20 kHz
0.1
0.01
0.001
10
20 Hz
100
PO − Output Power − mW
500
Figure 10.
7
TPA6110A2
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SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION + NOISE
vs
OUTPUT POWER
1
10
THD+N − Total Harmonic Distortion + Noise − %
THD+N − Total Harmonic Distortion + Noise − %
10
VDD = 3.3 V,
PO = 40 mW,
CB = 1 µF,
RL = 16 Ω,
AV = −1 V/V
0.1
0.01
0.001
20
100
1k
f − Frequency − Hz
500
TOTAL HARMONIC DISTORTION + NOISE
vs
OUTPUT POWER
10
THD+N − Total Harmonic Distortion + Noise − %
THD+N − Total Harmonic Distortion + Noise − %
100
PO − Output Power − mW
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
VDD = 5 V,
PO = 100 mW,
CB = 1 µF,
RL = 16 Ω
AV = −5 V/V
AV = −10 V/V
100
1k
f − Frequency − Hz
Figure 13.
8
0.01
Figure 12.
0.1
0.001
20
1 kHz
0.1
Figure 11.
AV = −1 V/V
0.01
20 Hz
20 kHz
0.001
10
10k 20k
10
1
1
VDD = 3.3 V,
RL =16 Ω,
AV = −1 V/V,
CB = 1 µF
10k
20k
1
VDD = 5 V,
RL = 16 Ω,
AV = −1 V/V,
CB = 1 µF
20 Hz
20 kHz
1 kHz
0.1
0.01
0.001
10
100
PO − Output Power − mW
Figure 14.
500
TPA6110A2
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SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
SUPPLY RIPPLE REJECTION RATIO
vs
FREQUENCY
SUPPLY RIPPLE REJECTION RATIO
vs
FREQUENCY
0
0.1 µF
−10
VDD = 3.3 V,
RL = 16 Ω,
AV = −1 V/V
0.47 µF
−20
1 µF
−30
−40
−50
−60
−70
−80
Bypass = 1.65 V
−90
−100
−110
K SVR − Supply Ripple Rejection Ratio − dB
K SVR − Supply Ripple Rejection Ratio − dB
0
−120
VDD = 5 V,
RL = 16 Ω,
AV = −1 V/V
0.47 µF
−20
1 µF
−30
−40
−50
−60
−70
−80
Bypass = 2.5 V
−90
−100
−110
−120
20
100
1k
f − Frequency − Hz
10k 20k
20
100
1k
f − Frequency − Hz
Figure 15.
Figure 16.
OUTPUT NOISE VOLTAGE
vs
FREQUENCY
OUTPUT NOISE VOLTAGE
vs
FREQUENCY
10k
20k
100
VDD = 3.3 V,
BW = 10 Hz to 22 kHz
RL = 16 Ω
AV = −10 V/V
AV = −1 V/V
10
1
V n − Output Noise Voltage − µ V(RMS)
100
V n − Output Noise Voltage − µ V(RMS)
0.1 µF
−10
AV = −10 V/V
AV = −1 V/V
10
VDD = 5 V,
BW = 10 Hz to 22 kHz
RL = 16 Ω
1
20
100
1k
f − Frequency − Hz
Figure 17.
10k 20k
20
100
1k
f − Frequency − Hz
10k 20k
Figure 18.
9
TPA6110A2
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SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
CROSSTALK
vs
FREQUENCY
CROSSTALK
vs
FREQUENCY
0
0
VDD = 3.3 V,
PO = 25 mW,
CB = 1 µF,
RL = 32 Ω,
AV = −1 V/V
−10
−20
−20
−30
−40
Crosstalk − dB
Crosstalk − dB
−30
−50
−60
−70
−80
−70
IN2− to VO1
20
100
1k
f − Frequency − Hz
IN1− to VO2
−110
IN1− to VO2
−120
10k 20k
20
100
1k
f − Frequency − Hz
Figure 19.
Figure 20.
CROSSTALK
vs
FREQUENCY
CROSSTALK
vs
FREQUENCY
0
10k 20k
0
VDD = 3.3 V,
PO = 60 mW,
CB = 1 µF,
RL = 8 Ω,
AV = −1 V/V
−10
−20
−30
−20
−30
−40
−50
−60
−70
IN2− to VO1
−80
VDD = 5 V,
PO = 60 mW,
CB = 1 µF,
RL = 32 Ω,
AV = −1 V/V
−10
Crosstalk − dB
Crosstalk − dB
−60
−100
−110
−40
−50
−60
−70
−80
−90
IN2− to VO1
−90
−100
−100
IN1− to VO2
−110
IN1− to VO2
−110
20
100
1k
f − Frequency − Hz
Figure 21.
10
−50
−90
−100
−120
−40
−80
IN2− to VO1
−90
−120
VDD = 3.3 V,
PO = 40 mW,
CB = 1 µF,
RL = 16 Ω,
AV = −1 V/V
−10
10k 20k
−120
20
100
1k
f − Frequency − Hz
Figure 22.
10k 20k
TPA6110A2
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SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
CROSSTALK
vs
FREQUENCY
CROSSTALK
vs
FREQUENCY
0
0
VDD = 5 V,
PO = 100 mW,
CB = 1 µF,
RL = 16 Ω,
AV = −1 V/V
−10
−20
−20
−30
−40
Crosstalk − dB
Crosstalk − dB
−30
−50
−60
−70
−80
−50
−60
−70
IN2− to VO1
−90
−100
−100
IN1− to VO2
−110
20
100
−10
1k
f − Frequency − Hz
−120
10k 20k
20
100
1k
f − Frequency − Hz
Figure 23.
Figure 24.
SHUTDOWN ATTENUATION
vs
FREQUENCY
SHUTDOWN ATTENUATION
vs
FREQUENCY
10k 20k
0
VDD = 3.3 V,
RL = 16 Ω,
CB = 1 µF
−10
−20
Shutdown Attenuation − dB
−20
−30
−40
−50
−60
−70
−40
−50
−60
−70
−80
−90
−90
100
1k
f − Frequency − Hz
Figure 25.
10 k 20 k
VDD = 5 V,
RL = 16 Ω,
CB = 1 µF
−30
−80
−100
10
IN1− to VO2
−110
0
Shutdown Attenuation − dB
−40
−80
IN2− to VO1
−90
−120
VDD = 5 V,
PO = 150 mW,
CB = 1 µF,
RL = 8 Ω,
AV = −1 V/V
−10
−100
10
100
1k
10 k 20 k
f − Frequency − Hz
Figure 26.
11
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SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
OPEN-LOOP GAIN AND PHASE MARGIN
vs
FREQUENCY
VDD = 3.3 V
RL = 10 kΩ
100
180
120
150
100
Gain
120
Phase
90
30
Gain
0
40
−30
20
−60
−90
0
Open-Loop Gain − dB
60
60
150
120
90
80
Φ m − Phase Margin − Deg
80
VDD = 5 V
RL = 10 kΩ
60
60
30
Phase
0
40
−30
20
−60
−90
0
−120
−20
−150
−40
1k
10 k
100 k
1M
−180
10 M
Φm − Phase Margin − Deg
180
120
Open-Loop Gain − dB
OPEN-LOOP GAIN AND PHASE MARGIN
vs
FREQUENCY
−120
−20
−150
−40
1k
10 k
f − Frequency − Hz
100 k
1M
−180
10 M
f − Frequency − Hz
Figure 27.
Figure 28.
OUTPUT POWER
vs
LOAD RESISTANCE
OUTPUT POWER
vs
LOAD RESISTANCE
100
250
VDD = 3.3 V,
THD+N = 1%,
AV = −1 V/V
VDD = 5 V,
THD+N = 1%,
AV = −1 V/V
200
P − Output Power − mW
O
P − Output Power − mW
O
75
50
25
0
100
50
0
8 12 16 20 24 28 32 36 40 44 45 52 56 60 64
8 12 16 20 24 28 32 36 40 44 48 52 56 60 64
RL − Load Resistance − Ω
RL − Load Resistance − Ω
Figure 29.
12
150
Figure 30.
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SUPPLY CURRENT
vs
SUPPLY VOLTAGE
SIGNAL-TO-NOISE RATIO
vs
VOLTAGE GAIN
120
2.5
SNR − Signal-to-Noise Ratio − dB
VDD = 5 V
I DD − Supply Current − mA
2
1.5
1
0.5
100
80
60
40
20
0
0
0.5
1
1.5 2 2.5 3 3.5 4
VDD − Supply Voltage − V
4.5
5
0
5.5
2
3
4
5
6
7
8
9
10
AV − Voltage Gain − V/V
Figure 31.
Figure 32.
POWER DISSIPATION/AMPLIFIER
vs
LOAD POWER
POWER DISSIPATION/AMPLIFIER
vs
LOAD POWER
180
80
VDD = 3.3 V
VDD = 5 V
Power Dissipation/Amplifier − mW
8Ω
70
Power Dissipation/Amplifier − mW
1
60
50
40
16 Ω
30
32 Ω
20
140
120
100
16 Ω
80
60
32 Ω
40
64 Ω
10
8Ω
160
64 Ω
20
0
0
0
20
40
60
80 100 120 140 160 180
Load Power − mW
Figure 33.
200
0
20
40
60
80 100 120 140 160 180
200
Load Power − mW
Figure 34.
13
TPA6110A2
www.ti.com
SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
APPLICATION INFORMATION
f c(highpass) GAIN SETTING RESISTORS, Rf and Ri
The gain for the TPA6110A2 is set by resistors Rf
and Ri according to Equation 1.
Gain Rf
Ri
(1)
Given that the TPA6110A2 is a MOS amplifier, the
input impedance is very high. Consequently input
leakage currents are not generally a concern. However, 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.
Considering these factors, 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 using Equation 2.
Effective Impedance R fR i
Rf Ri
(2)
For example, if the input resistance is 20 kΩ and the
feedback resistor is 20 kΩ, the gain of the amplifier is
-1, and the effective impedance at the inverting
terminal is 10 kΩ, a value 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 by
Equation 3.
f c(lowpass) 1
2 R f CF
(3)
For example, if Rf is 100 kΩ and CF is 5 pF then
fc(lowpass) is 318 kHz, which is well outside 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 4.
14
1
2 R i Ci
(4)
The value of Ci directly affects the bass (low frequency) performance of the circuit. Consider the
example where Ri is 20 kΩ and the specification calls
for a flat bass response down to 20 Hz. Equation 4 is
reconfigured as Equation 5.
Ci 1
2 R i f c(highpass)
(5)
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
formed by 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 (gain
>10). For this reason a low-leakage tantalum or
ceramic capacitor is the best choice. When polarized
capacitors are used, connect the positive side of the
capacitor to the amplifier input in most applications.
The dc level there is held at VDD/2—likely higher than
the source dc level. It is important to confirm the
capacitor polarity in the application.
POWER SUPPLY DECOUPLING, C(S)
The TPA6110A2 is a high-performance CMOS audio
amplifier that requires adequate power-supply decoupling to minimize the output total harmonic distortion (THD). Power-supply decoupling also prevents
oscillations when long lead lengths are used 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 power amplifier is recommended.
TPA6110A2
www.ti.com
SLOS314A – DECEMBER 2000 – REVISED SEPTEMBER 2004
MIDRAIL BYPASS CAPACITOR, C(B)
The midrail bypass capacitor, C(B), serves several
important functions. During start up, C(B) 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 230-kΩ source
inside the amplifier. To keep the start-up pop as low
as possible, maintain the relationship shown in
Equation 6.
1
C(B) 230 kΩ
1
C i R i
(6)
Consider an example circuit where C(B) is 1 µF, Ci is
1 µF, and Ri is 20 kΩ. Subsitituting these values into
the equation 9 results in: 6.25 ≤ 50 which satisfies the
rule. Bypass capacitor, C(B), 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 a typical single-supply, single-ended (SE) configuration, an output coupling capacitor (C(C)) 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.
fc 1
2 R L C(C)
(7)
The main disadvantage, from a performance standpoint, is that the typically-small load impedance 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 C(C) of 68 µF is
chosen and loads vary from 32 Ω to 47 kΩ. Table 1
summarizes the frequency response characteristics
of each configuration.
Table 1. Common Load Impedances vs LowFrequency Output Characteristics in SE Mode
RL
C(C)
LOWEST FREQUENCY
32 Ω
68 µF
73 Hz
10,000 Ω
68 µF
0.23 Hz
47,000 Ω
68 µF
0.05 Hz
As Table 1 indicates, 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. With the rules described earlier still
valid, add the following relationship:
1
C(B) 230 kΩ
1
C i R i
1
RLC (C)
(8)
USING LOW-ESR CAPACITORS
Low-ESR capacitors are recommended throughout
this application. 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.
5-V VERSUS 3.3-V OPERATION
The TPA6110A2 was designed for operation 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, since these are considered to be the two most
common supply voltages. There are no special considerations for 3.3-V versus 5-V operation as far as
supply bypassing, gain setting, or stability. The most
important consideration is that of output power. Each
amplifier in theTPA6110A2 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 when VO(PP) = 4 V while operating at 5 V.
The reduced voltage swing subsequently reduces
maximum output power into the load before distortion
becomes significant.
15
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