TI TPA301DGN

TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
350-mW MONO AUDIO POWER AMPLIFIER
FEATURES
•
•
•
•
•
•
D OR DGN PACKAGE
(TOP VIEW)
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 = 3.3 V, BTL
Ultra-Low Quiescent Current in Shutdown
Mode . . . 0.15 µA
Thermal and Short-Circuit Protection
Surface-Mount Packaging
– SOIC
– PowerPAD™ MSOP
SHUTDOWN
BYPASS
IN+
IN-
1
8
2
7
3
6
4
5
VOGND
VDD
VO+
DESCRIPTION
The TPA301 is a bridge-tied load (BTL) audio power amplifier developed especially for low-voltage applications
where internal speakers are required. Operating with a 3.3-V supply, the TPA301 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. This device features a
shutdown mode for power-sensitive applications with a quiescent current of 0.15 µA during shutdown. The
TPA301 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
VDD
RF
CS
VDD/2
Audio
Input
RI
CI
4
IN -
3
IN+
2
BYPASS
1 µF
-
VO+ 5
+
CB
0.1 µF
-
VO-
+
8
350 mW
7
GND
From System Control
1
SHUTDOWN
Bias
Control
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 © –2004, Texas Instruments Incorporated
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated
circuits be handled with appropriate precautions. Failure to observe proper handling and installation
procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision
integrated circuits may be more susceptible to damage because very small parametric changes could
cause the device not to meet its published specifications.
AVAILABLE OPTIONS
PACKAGED DEVICES
(1)
MSOP
SYMBOLIZATION
TA
SMALL OUTLINE (1)
(D)
MSOP (1)
(DGN)
–40°C to 85°C
TPA301D
TPA301DGN
AAA
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., TPA301DR).
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range (unless otherwise noted)
(1)
UNIT
VDD
Supply voltage
VI
Input voltage
6V
–0.3 V to VDD +0.3 V
Continuous total power dissipation
Internally limited (see Dissipation Rating Table)
TA
Operating free-air temperature range
–40°C to 85°C
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 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
DERATING FACTOR
TA = 70°C
TA = 85°C
D
725 mW
5.8 mW/°C
464 mW
377 mW
W (1)
17.1 mW/°C
1.37 W
1.11 W
DGN
(1)
2.14
See the Texas Instruments document, PowerPAD Thermally Enhanced Package Application Report
(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
VDD
Supply voltage
VIH
High-level voltage
SHUTDOWN
VIL
Low-level voltage
SHUTDOWN
TA
Operating free-air temperature
2
MIN
MAX
2.5
5.5
0.9 VDD
–40
UNIT
V
V
0.1 VDD
V
85
°C
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
ELECTRICAL CHARACTERISTICS
at specified free-air temperature, VDD = 3.3 V, TA = 25°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP MAX
|VOD|
Differential output voltage
SHUTDOWN = 0 V, RL = 8 Ω, RF = 10 kΩ
PSRR
Power supply rejection ratio
VDD = 3.2 V to 3.4 V
85
IDD
Supply current (see Figure 3)
SHUTDOWN = 0 V, RF = 10 kΩ
IDD(SD)
Supply current, shutdown mode (see Figure 4)
SHUTDOWN = VDD, RF = 10 kΩ
|IIH|
High-level input current
SHUTDOWN, VDD = 3.3 V, VI = 3.3 V
|IIL|
Low-level input current
SHUTDOWN, VDD = 3.3 V, VI = 0 V
5
UNIT
20
mV
0.7
1.5
mA
0.15
5
µA
1
µA
1
µA
dB
OPERATING CHARACTERISTICS
VDD = 3.3 V, TA = 25°C, RL = 8 Ω
PARAMETER
TEST CONDITIONS
MIN
TYP MAX
UNIT
250
mW
PO
Output power (1)
THD = 0.5%,
See Figure 9
THD + N
Total harmonic distortion plus noise
PO = 250 mW,
AV = 2 V/V,
f = 20 Hz to 4 kHz,
See Figure 7
Maximum output power bandwidth
AV = 2 V/V, THD = 3%,
See Figure 7
10
kHz
Unity-gain bandwidth
Open loop,
See Figure 15
1.4
MHz
Supply ripple rejection ratio
f = 1 kHz, CB = 1 µF,
See Figure 2
71
dB
Noise output voltage
AV = 1 V/V,
RL = 32 Ω,
CB = 0.1 µF,
See Figure 19
15
µV(rms)
B1
Vn
(1)
1.3%
Output power is measured at the output terminals of the device at f = 1 kHz.
ELECTRICAL CHARACTERISTICS
at specified free-air temperature, VDD = 5 V, TA = 25°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP MAX
|VOD|
Differential output voltage
SHUTDOWN = 0 V, RL = 8 Ω, RF = 10 kΩ
PSRR
Power supply rejection ratio
VDD = 4.9 V to 5.1 V
78
IDD
Supply current (see Figure 3)
SHUTDOWN = 0 V, RF = 10 kΩ
IDD(SD)
Supply current, shutdown mode (see Figure 4)
SHUTDOWN = VDD, RF = 10 kΩ
|IIH|
High-level input current
|IIL|
Low-level input current
5
UNIT
20
mV
0.7
1.5
mA
0.15
5
µA
SHUTDOWN, VDD = 5.5 V, VI = VDD
1
µA
SHUTDOWN, VDD = 5.5 V, VI = 0 V
1
µA
dB
OPERATING CHARACTERISTICS
VDD = 5 V, TA = 25°C, RL = 8 Ω
TYP MAX
UNIT
PO
Output power
PARAMETER
THD = 0.5%,
See Figure 13
700
mW
THD + N
Total harmonic distortion plus noise
PO = 350 mW,
AV = 2 V/V,
f = 20 Hz to 4 kHz,
See Figure 11
1%
Maximum output power bandwidth
AV = 2 V/V, THD = 2%,
See Figure 11
10
kHz
Unity-gain bandwidth
Open loop,
See Figure 16
1.4
MHz
Supply ripple rejection ratio
f = 1 kHz, CB = 1 µF,
See Figure 2
65
dB
Noise output voltage
AV = 1 V/V,
RL = 32 Ω ,
CB = 0.1 µF,
See Figure 20
15
µV(rms)
B1
Vn
TEST CONDITIONS
MIN
3
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
Terminal Functions
TERMINAL
NAME
NO.
I/O
I
DESCRIPTION
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 inverting input. IN- is typically used as the audio input terminal.
IN+
3
I
IN+ is the noninverting input. IN+ is typically tied to the BYPASS terminal.
SHUTDOWN
1
I
SHUTDOWN places the entire device in shutdown mode when held high (IDD~ 0.15 µA).
VDD
6
VO+
5
O
VO+ is the positive BTL output.
VO-
8
O
VO- is the negative BTL output.
GND is the ground connection.
VDD is the supply voltage terminal.
PARAMETER MEASUREMENT INFORMATION
VDD 6
RF
Audio
Input
RI
CI
4
IN -
3
IN+
2
BYPASS
1 µF
-
VO+ 5
+
RL = 8 Ω
CB
0.1 µF
-
VO-
+
SHUTDOWN
Bias
Control
Figure 1. Test Circuit
4
8
7
GND
1
VDD
CS
VDD/2
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
TYPICAL CHARACTERISTICS
Table of Graphs
FIGURE
kSVR
Supply voltage rejection ratio
vs Frequency
IDD
Supply current
vs Supply voltage
3, 4
PO
Output power
vs Supply voltage
5
THD+N
2
vs Load resistance
Total harmonic distortion plus noise
6
vs Frequency
7, 8, 11, 12
vs Output power
9, 10, 13, 14
Open-loop gain and phase
vs Frequency
15, 16
Closed-loop gain and phase
vs Frequency
17, 18
Vn
Output noise voltage
vs Frequency
19, 20
PD
Power dissipation
vs Output power
21, 22
SUPPLY VOLTAGE REJECTION RATIO
vs
FREQUENCY
SUPPLY CURRENT
vs
SUPPLY VOLTAGE
−10
1.1
RL = 8 Ω
CB = 1 µF
SHUTDOWN = 0 V
RF = 10 kΩ
0.9
−20
I DD(q) − Supply Current − mA
kSVR − Supply Voltage Rejection Ratio − dB
0
−30
−40
−50
VDD = 5 V
−60
−70
VDD = 3.3 V
−80
0.7
0.5
0.3
0.1
−90
−100
20
100
1k
f − Frequency − Hz
Figure 2.
10 k 20 k
−0.1
2
3
4
5
6
VDD − Supply Voltage − V
Figure 3.
5
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
SUPPLY CURRENT (SHUTDOWN)
vs
SUPPLY VOLTAGE
0.5
SHUTDOWN = VDD
RF = 10 kΩ
I DD(SD)− Supply Current − µ A
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
2
2.5
3
3.5
4
4.5
5
5.5
5
5.5
VDD − Supply Voltage − V
Figure 4.
OUTPUT POWER
vs
SUPPLY VOLTAGE
1000
THD+N 1%
PO − Output Power − mW
800
600
RL = 8 Ω
400
RL = 32 Ω
200
0
2
2.5
3
3.5
4
4.5
VDD − Supply Voltage − V
Figure 5.
6
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
OUTPUT POWER
vs
LOAD RESISTANCE
800
THD+N = 1%
700
PO − Output Power − mW
600
VDD = 5 V
500
400
300
VDD = 3.3 V
200
100
0
8
16
24
32
40
48
56
64
RL − Load Resistance − Ω
Figure 6.
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
10
VDD = 3.3 V
PO = 250 mW
RL = 8 Ω
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
VDD = 3.3 V
RL = 8 Ω
AV = −2 V/V
PO = 50 mW
1
PO = 125 mW
0.1
PO = 250 mW
0.01
20
100
1k
f − Frequency − Hz
f − Frequency − Hz
Figure 7.
Figure 8.
10k
20k
7
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
TOTAL HARMONIC DISTORTION + NOISE
vs
OUTPUT POWER
TOTAL HARMONIC DISTORTION + NOISE
vs
OUTPUT POWER
10
THD+N −Total Harmonic Distortion + Noise − %
THD+N −Total Harmonic Distortion + Noise − %
10
VDD = 3.3 V
f = 1 kHz
AV = −2 V/V
1
RL = 8 Ω
0.1
0.01
0.04
0.1
0.16
0.22
0.28
0.34
f = 20 kHz
f = 10 kHz
1
f = 1 kHz
0.1
f = 20 Hz
0.01
0.01
0.4
0.1
Figure 9.
Figure 10.
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
10
VDD = 5 V
PO = 350 mW
RL = 8 Ω
THD+N −Total Harmonic Distortion + Noise − %
THD+N −Total Harmonic Distortion + Noise − %
10
8
1
PO − Output Power − W
PO − Output Power − W
AV = −20 V/V
1
AV =− 10 V/V
AV = −2 V/V
0.1
0.01
20
VDD = 3.3 V
RL = 8 Ω
AV = −2 V/V
100
1k
10k
20k
VDD = 5 V
RL = 8 Ω
AV = −2 V/V
PO = 50 mW
1
PO = 175 mW
0.1
PO = 350 mW
0.01
20
100
1k
f − Frequency − Hz
f − Frequency − Hz
Figure 11.
Figure 12.
10k
20k
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
TOTAL HARMONIC DISTORTION + NOISE
vs
OUTPUT POWER
TOTAL HARMONIC DISTORTION + NOISE
vs
OUTPUT POWER
10
THD+N −Total Harmonic Distortion + Noise − %
VDD = 5 V
f = 1 kHz
AV = −2 V/V
1
RL = 8 Ω
0.1
0.25
0.40
0.55
0.70
0.85
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
0.01
0.01
1
0.1
1
PO − Output Power − W
PO − Output Power − W
Figure 13.
Figure 14.
OPEN-LOOP GAIN AND PHASE
vs
FREQUENCY
40
180
Phase
30
VDD = 3.3 V
RL = Open
120
Gain
20
60
10
0
0
Phase − °
0.01
0.1
Open-Loop Gain − dB
THD+N −Total Harmonic Distortion + Noise − %
10
−60
−10
−120
−20
−30
−180
1
101
102
103
104
f − Frequency − kHz
Figure 15.
9
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
OPEN-LOOP GAIN AND PHASE
vs
FREQUENCY
40
180
VDD = 5 V
RL = Open
Phase
30
120
20
60
10
0
0
Phase − °
Open-Loop Gain − dB
Gain
−60
−10
−120
−20
−30
−180
1
101
102
103
104
f − Frequency − kHz
Figure 16.
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 = 3.3 V
RL = 8 Ω
PO = 0.25 W
CI =1 µF
130
120
102
103
104
f − Frequency − Hz
Figure 17.
10
105
106
Phase − °
Closed-Loop Gain − dB
0.5
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
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
Phase − °
Closed-Loop Gain − dB
0.5
140
−1
VDD = 5 V
RL = 8 Ω
PO = 0.35 W
CI =1 µF
−1.25
−1.5
−1.75
−2
101
102
130
103
104
105
120
106
f − Frequency − Hz
Figure 18.
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
f − Frequency − Hz
Figure 19.
10 k
20 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
100
1k
10 k
20 k
f − Frequency − Hz
Figure 20.
11
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
POWER DISSIPATION
vs
OUTPUT POWER
300
720
270
640
PD − Power Dissipation − mW
PD − Power Dissipation − mW
POWER DISSIPATION
vs
OUTPUT POWER
240
210
180
150
VDD = 3.3 V
RL = 8 Ω
120
480
400
320
VDD = 5 V
RL = 8 Ω
240
90
160
0
100
200
300
PO − Output Power − mW
Figure 21.
12
560
400
0
200
400
600
800
PO − Output Power − mW
Figure 22.
1000
1200
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
APPLICATION INFORMATION
BRIDGE-TIED LOAD
Figure 23 shows a linear audio power amplifier (APA) in a BTL configuration. The TPA301 BTL amplifier consists
of two linear amplifiers driving both ends of the load. There are several potential benefits to this differential drive
configuration but power to the load should be initially considered. 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).
VO(PP)
V (RMS) 2 2
Power V (RMS)
2
RL
(1)
VDD
VO(PP)
RL
2x VO(PP)
VDD
-VO(PP)
Figure 23. Bridge-Tied Load Configuration
In a typical portable handheld equipment sound channel operating at 3.3 V, 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 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 24. A coupling capacitor is
required to block the dc offset voltage from reaching the load. These capacitors can be quite large
(approximately 33 µF to 1000 µF) so they tend to be expensive, heavy, occupy valuable PCB area, and have the
additional drawback of limiting low-frequency performance of the system. This frequency limiting effect is due to
the high pass filter network created with the speaker impedance and the coupling capacitance and is calculated
with Equation 2.
1
f (corner) 2 R L CC
(2)
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, eliminating 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.
13
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
APPLICATION INFORMATION (continued)
VDD
-3 dB
VO(PP)
CC
RL
VO(PP)
fc
Figure 24. 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 a 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 sine-wave 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, IDD(RMS), 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 25).
VO
IDD
IDD(RMS)
VL(RMS)
Figure 25. Voltage and Current Waveforms for BTL Amplifiers
Although the voltages and currents for SE and BTL are sinusoidal in the load, currents from the supply are
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.
14
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
APPLICATION INFORMATION (continued)
P
Efficiency where
PL P
V L RMS
R
L
L
SUP
2
Vp
2
2R
L
V
V P
L RMS
2
P SUP VDD I DD RMS
I
DDRMS V DD 2VP
RL
2V P
RL
(3)
Efficiency of a BTL Configuration VP
2V DD
P LR L
2
12
2V DD
(4)
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
(1)
OUTPUT POWER
(W)
EFFICIENCY
(%)
PEAK-to-PEAK
VOLTAGE
(V)
INTERNAL
DISSIPATION
(W)
0.125
33.6
1.41
0.26
0.25
47.6
2.00
0.29
0.375
58.3
2.45 (1)
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. Note that in Equation 4, VDD is in the denominator. This
indicates that as VDD goes down, efficiency goes up.
APPLICATION SCHEMATIC
Figure 26 is a schematic diagram of a typical handheld audio application circuit, configured for a gain of –10 V/V.
15
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
VDD 6
RF
50 kΩ
CF
5 pF
Audio
Input
CI
RI
0.47 µF 10 kΩ
4
IN -
3
IN+
2
BYPASS
VDD
CS
VDD/2
1 µF
-
VO+ 5
+
CB
2.2 µF
-
VO-
+
8
350 mW
7
GND
From System Control
1
SHUTDOWN
Bias
Control
Figure 26. TPA301 Application Circuit
The following sections discuss the selection of the components used in Figure 26.
COMPONENT SELECTION
Gain Setting Resistors, RF and RI
The gain for each audio input of the TPA301 is set by resistors RF and RI according to Equation 5 for BTL mode.
R
F
BTL Gain A V 2
R
I
(5)
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 TPA301 is a MOS amplifier, the input impedance is 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 are 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.
R R
F I
Effective Impedance R R
F
I
(6)
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.
16
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
−3 dB
f
co(lowpass)
1
2 R C
F F
fco
(7)
For example, if RF is 100 kΩ and CF is 5 pF then fco 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 8.
−3 dB
f
co(highpass)
1
2 R C
I I
fco
(8)
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.
1
C I
2 R f co
I
(9)
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 TPA301 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.
17
TPA301
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
www.ti.com
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, appearing 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 ensures the input capacitor is fully charged
before the bypass capacitor is fully charged and the amplifier starts up.
10
1
CB 250 kΩ RF RI CI
(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. Recommended values for bypass
capacitor CB are 2.2 µF to 1 µF, ceramic or tantalum low-ESR, for the best THD and noise performance.
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.
5-V VERSUS 3.3-V OPERATION
The TPA301 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 TPA301 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 than 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 TPA301 data sheet, one can see that when the TPA301
is operating from a 5-V supply into a 8-Ω speaker, 350-mW peaks are available. Converting watts to dB:
P
10LogP 10Log 3500 mW –4.6 dB
dB
W
Subtracting the headroom restriction to obtain the average listening level without distortion yields:
–4.6 dB – 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)
18
TPA301
www.ti.com
SLOS208E – JANUARY 1998 – REVISED JUNE 2004
Converting dB back into watts:
PW = 10PdB/10
= 11 mW (15 dB headroom)
= 22 mW (12 dB headroom)
= 44 mW (9 dB headroom)
= 88 mW (6 dB headroom)
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 TPA301 and
maximum ambient temperatures is shown in Table 2.
Table 2. TPA301 Power Rating, 5-V, 8-Ω, BTL
PEAK OUTPUT
POWER
(mW)
MAXIMUM AMBIENT
TEMPERATURE
AVERAGE OUTPUT
POWER
POWER DISSIPATION
(mW)
350
350 mW
600
46°C
350
175 mW (3 dB)
500
64°C
350
88 mW (6 dB)
380
85°C
350
44 mW (9 dB)
300
98°C
350
22 mW (12 dB)
200
115°C
350
11 mW (15 dB)
180
119°C
0 CFM
Table 2 shows that the TPA301 can be used to its full 350-mW rating without any heat sinking in still air up to
46°C.
19
PACKAGE OPTION ADDENDUM
www.ti.com
18-Apr-2006
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
TPA301D
ACTIVE
SOIC
D
8
75
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
TPA301DG4
ACTIVE
SOIC
D
8
75
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
TPA301DGN
ACTIVE
MSOPPower
PAD
DGN
8
80
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
TPA301DGNG4
ACTIVE
MSOPPower
PAD
DGN
8
80
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
TPA301DGNR
ACTIVE
MSOPPower
PAD
DGN
8
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
TPA301DGNRG4
ACTIVE
MSOPPower
PAD
DGN
8
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
TPA301DR
ACTIVE
SOIC
D
8
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
TPA301DRG4
ACTIVE
SOIC
D
8
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
Lead/Ball Finish
MSL Peak Temp (3)
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 1
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,
enhancements, improvements, and other changes to its products and services at any time and to
discontinue any product or service without notice. Customers should obtain the latest relevant information
before placing orders and should verify that such information is current and complete. All products are sold
subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent
TI deems necessary to support this warranty. Except where mandated by government requirements, testing
of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible
for their products and applications using TI components. To minimize the risks associated with customer
products and applications, customers should provide adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent
right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine,
or process in which TI products or services are used. Information published by TI regarding third-party
products or services does not constitute a license from TI to use such products or services or a warranty or
endorsement thereof. Use of such information may require a license from a third party under the patents or
other intellectual property of the third party, or a license from TI under the patents or other intellectual
property of TI.
Reproduction of information in TI data books or data sheets is permissible only if reproduction is without
alteration and is accompanied by all associated warranties, conditions, limitations, and notices.
Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not
responsible or liable for such altered documentation.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for
that product or service voids all express and any implied warranties for the associated TI product or service
and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements.
Following are URLs where you can obtain information on other Texas Instruments products and application
solutions:
Products
Applications
Amplifiers
amplifier.ti.com
Audio
www.ti.com/audio
Data Converters
dataconverter.ti.com
Automotive
www.ti.com/automotive
DSP
dsp.ti.com
Broadband
www.ti.com/broadband
Interface
interface.ti.com
Digital Control
www.ti.com/digitalcontrol
Logic
logic.ti.com
Military
www.ti.com/military
Power Mgmt
power.ti.com
Optical Networking
www.ti.com/opticalnetwork
Microcontrollers
microcontroller.ti.com
Security
www.ti.com/security
Low Power Wireless
www.ti.com/lpw
Telephony
www.ti.com/telephony
Mailing Address:
Video & Imaging
www.ti.com/video
Wireless
www.ti.com/wireless
Texas Instruments
Post Office Box 655303 Dallas, Texas 75265
Copyright © 2007, Texas Instruments Incorporated