TI TPA3120D2PWP

TPA3120D2
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SLOS507 – MARCH 2007
25-W STEREO CLASS-D AUDIO POWER AMPLIFIER
FEATURES
•
•
•
•
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DESCRIPTION
25-W/ch into a 4-Ω Load from a 27-V Supply
20-W/ch into a 4-Ω Load from a 24-V Supply
Operates from 10 V to 30 V
Efficient Class-D Operation Eliminates Need
for Heat Sinks
Four Selectable, Fixed Gain Settings
Internal Oscillator (No External Components
Required)
Single Ended Analog Inputs
Thermal and Short-Circuit Protection with
Auto Recovery
Space-Saving Surface Mount 24-pin TSSOP
Package
The TPA3120D2 is a 25-W (per channel) efficient,
Class-D audio power amplifier for driving stereo
speakers in a single-ended configuration or a mono
bridge-tied speaker. The TPA3120D2 can drive
stereo speakers as low as 4 Ω. The efficiency of the
TPA3120D2 eliminates the need for an external heat
sink when playing music.
The gain of the amplifier is controlled by two gain
select pins. The gain selections are 20, 26, 32,
36 dB.
The patented start-up and shut-down sequences
minimize "pop" noise in the speakers without
additional circuitry.
TPA3120D2
APPLICATIONS
•
Televisions
SIMPLIFIED APPLICATION CIRCUIT
TPA3120D2
1 mF
0.22 mF
Left Channel
LIN
BSR
Right Channel
RIN
ROUT
1 mF
PGNDR
PGNDL
1 mF
BYPASS
AGND
22 mH
470 mF
1 mF
1 mF
LOUT
22 mH
BSL
470 mF
0.22 mF
10 V to 30 V
AVCC
10 V to 30 V
PVCCL
PVCCR
VCLAMP
Shutdown
Control
Mute Control
SD
1 mF
MUTE
GAIN0
GAIN1
}
4-Step Gain
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.
PRODUCT PREVIEW information concerns products in the
formative or design phase of development. Characteristic data and
other specifications are design goals. Texas Instruments reserves
the right to change or discontinue these products without notice.
Copyright © 2007, Texas Instruments Incorporated
PRODUCT PREVIEW
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•
•
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TPA3120D2
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SLOS507 – MARCH 2007
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.
PWP (TSSOP) PACKAGE
(TOP VIEW)
PVCCL
SD
PVCCL
MUTE
LIN
RIN
BYPASS
AGND
AGND
PVCCR
VCLAMP
PVCCR
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
PGNDL
PGNDL
LOUT
BSL
AVCC
AVCC
GAIN0
GAIN1
BSR
ROUT
PGNDR
PGNDR
PRODUCT PREVIEW
TERMINAL FUNCTIONS
TERMINAL
24-PIN
(PWP)
I/O/P
DESCRIPTION
SD
2
I
Shutdown signal for IC (low = disabled, high = operational). TTL logic levels with compliance to
AVCC.
RIN
6
I
Audio input for right channel.
LIN
5
I
Audio input for left channel.
GAIN0
18
I
Gain select least significant bit. TTL logic levels with compliance to AVCC.
GAIN1
17
I
Gain select most significant bit. TTL logic levels with compliance to AVCC.
MUTE
4
I
Mute signal for quick disable/enable of outputs (high = outputs switch at 50% duty cycle, low =
outputs enabled). TTL logic levels with compliance to AVCC.
BSL
21
I/O
PVCCL
1, 3
P
Power supply for left channel H-bridge, not internally connected to PVCCR or AVCC.
LOUT
22
O
Class-D 1/2-H-bridge positive output for left channel.
23, 24
P
Power ground for left channel H-bridge.
Internally generated voltage supply for bootstrap capacitors.
NAME
PGNDL
VCLAMP
11
P
BSR
16
I/O
Bootstrap I/O for right channel.
ROUT
15
O
Class-D 1/2-H-bridge negative output for right channel.
PGNDR
13, 14
P
Power ground for right channel H-bridge.
PVCCR
10, 12
P
Power supply for right channel H-bridge, not connected to PVCCL or AVCC.
AGND
9
P
Analog ground for digital/analog cells in core.
AGND
8
P
Analog Ground for analog cells in core.
O
Reference for pre-amplifier inputs. Nominally equal to AVCC/8. Also controls start-up time via
7
external capacitor sizing.
19, 20
P
High-voltage analog power supply. Not internally connected to PVCCR or PVCCL
Die Pad
P
Connect to ground. Thermal Pad should be soldered down on all applications to properly
secure device to printed wiring board.
BYPASS
AVCC
Thermal Pad
2
Bootstrap I/O for left channel.
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TPA3120D2
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SLOS507 – MARCH 2007
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range (unless otherwise noted) (1)
VCC
Supply voltage, AVCC, PVCC
VI
Logic input voltage
SD, MUTE, GAIN0, GAIN1
VIN
Analog input voltage
RIN, LIN
Continuous total power dissipation
VALUE
UNIT
–0.3 to 36
V
–0.3 to VCC +0.3 –0.3 to VCC +0.3
V
-0.3 to 7
V
See Dissipation Rating Table
TA
Operating free-air temperature range
–40 to 85
°C
TJ
Operating junction temperature range
–40 to 150
°C
Tstg
Storage temperature range
-65 to 150
°C
RL
Load resistance (Minimum value)
3.2
Ω
ESD
Electrostatic Discharge
(1)
±2
Human body model (all pins)
kV
± 500
Charged-device model (all pins)
Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings
only, and functional operations 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.
(1)
PACKAGE (1)
TA ≤ 25°C
DERATING FACTOR
TA = 70°C
TA = 85°C
24-pin TSSOP
4.16 W
33.3 mW/°C
2.67 W
2.16 W
PRODUCT PREVIEW
DISSIPATION RATINGS
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
Web site at www.ti.com.
RECOMMENDED OPERATING CONDITIONS
MIN
MAX
10
30
VCC
Supply voltage
PVCC, AVCC
VIH
High-level input voltage
SD, MUTE, GAIN0, GAIN1
VIL
Low-level input voltage
SD, MUTE, GAIN0, GAIN1
0.8
SD, VI = VCC, VCC = 30 V
125
IIH
High-level input current
MUTE, VI = VCC, VCC = 30 V
125
GAIN0, GAIN1, VI = VCC, VCC = 24 V
125
IIL
TA
Low-level input current
2
1
MUTE, VI = 0 V, VCC = 30 V
1
GAIN0, GAIN1, VI = 0 V, VCC = 24 V
1
–40
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V
V
SD, VI = 0, VCC = 30 V
Operating free-air temperature
UNIT
85
V
µA
µA
°C
3
TPA3120D2
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SLOS507 – MARCH 2007
DC CHARACTERISTICS
TA = 25°C, VCC = 24 V, RL = 4 Ω (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
7.5
50
| VOS |
Class-D output offset voltage
VI = 0 V, AV = 36 dB
(measured differentially)
V(BYPASS)
Bypass output voltage
No load
PSRR
Power supply rejection ratio
VCC = 10 V to 30 V, Inputs ac coupled to AGND,
Gain = 36 dB
ICC(q)
Quiescent supply current
SD = 2 V, MUTE = 0 V, No load
23
ICC(q)
Quiescent supply current in
mute mode
MUTE = 0.8 V, No load
23
ICC(q)
Quiescent supply current in
shutdown mode
SD = 0.8 V , No load
rDS(on)
Drain-source on-state
resistance
G
Gain
GAIN = 2 V
mV
AVCC/8
V
-70
dB
390
37
mA
mA
825
250
GAIN1 = 0.8 V
UNIT
µA
mΩ
GAIN0 = 0.8 V
18
20
22
GAIN0 = 2 V
24
26
28
GAIN0 = 0.8 V
30
32
34
GAIN0 = 2 V
34
36
38
dB
PRODUCT PREVIEW
AC CHARACTERISTICS
TA = 25°C, VCC = 24 V, RL = 4Ω (unless otherwise noted)
PARAMETER
KSVR
Supply ripple rejection
Output Power at 1% THD+N
PO
Output Power at 10% THD+N
TEST CONDITIONS
VCC = 19.5 V to 20.5 V from 10 Hz to 1 kHz,
Gain = 20 dB
16
8
VCC = 24 V, RL = 4 Ω, f = 1 kHz
20
VCC = 24 V, RL = 8 Ω, f = 1 kHz
10
RL = 4 Ω, f = 1 kHz, Po = 10 W
0.08%
RL = 8 Ω, f = 1 kHz, Po = 5 W
0.15%
Vn
Output integrated noise floor
20 Hz to 22 kHz, A-weighted filter, Gain = 20 dB
Crosstalk
PO = 1 W, f = 1kHz; Gain = 20 dB
Signal-to-noise ratio
Max Output at THD+N < 1%, f = 1 kHz, Gain = 20 dB
Thermal trip point
Thermal hysteresis
4
Oscillator frequency
230
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MAX
-60
VCC = 24 V, RL = 8 Ω, f = 1 kHz
Total harmonic distortion + noise
fOSC
TYP
VCC = 24 V, RL = 4 Ω, f = 1 kHz
THD+N
SNR
MIN
UNIT
dB
W
85
µV
-80
dB
-60
dB
99
dB
150
°C
30
°C
250
270
kHz
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SLOS507 – MARCH 2007
TYPICAL CHARACTERISTICS
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
1
PO = 5 W
PO = 2.5 W
0.1
PO = 1 W
1k
100
RL = 4 W (SE)
Gain = 20 dB
1
PO = 10 W
PO = 5 W
0.1
PO = 1 W
0.01
20
10k 20k
100
1k
10k 20k
f − Frequency − Hz
f − Frequency − Hz
Figure 1.
Figure 2.
TOTAL HARMONIC DISTORTION + NOISE
vs
FREQUENCY
TOTAL HARMONIC DISTORTION + NOISE
vs
OUTPUT POWER
10
VCC = 24 V
RL = 8 W (BTL)
Gain = 26 dB
PO = 20 W
1
0.1
PO = 5 W
PO = 1 W
0.01
0.001
20
VCC = 24 V
100
1k
10k 20k
PRODUCT PREVIEW
THD+N - Total Harmonic Distortion + Noise - %
RL = 4 W (SE)
Gain = 20 dB
0.01
20
THD+N - Total Harmonic Distortion + Noise - %
10
VCC = 18 V
THD+N - Total Harmonic Distortion + Noise - %
THD+N - Total Harmonic Distortion + Noise - %
10
100
RL = 4 W (SE)
Gain = 20 dB
10
VCC = 24 V
VCC = 18 V
1
VCC = 12 V
0.1
0.01
10 m
100 m
1
f − Frequency − Hz
PO − Output Power − W
Figure 3.
Figure 4.
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10
40
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TYPICAL CHARACTERISTICS (continued)
TOTAL HARMONIC DISTORTION + NOISE
vs
OUTPUT POWER
THD+N - Total Harmonic Distortion + Noise - %
PRODUCT PREVIEW
THD+N - Total Harmonic Distortion + Noise - %
TOTAL HARMONIC DISTORTION + NOISE
vs
OUTPUT POWER
RL = 8 W (SE)
Gain = 20 dB
VCC = 12 V
VCC = 18 V
VCC = 24 V
100
RL = 8 W (BTL)
Gain = 26 dB
10
VCC = 24 V
VCC = 18 V
1
VCC = 12 V
0.1
0.01
10 m
100 m
1
10
40
PO − Output Power − W
Figure 5.
Figure 6.
CROSSTALK
vs
FREQUENCY
CROSSTALK
vs
FREQUENCY
0
0
-10
VCC = 18 V
VO = 1 Vrms
-10
VCC = 18 V
VO = 1 Vrms
-20
RL = 4 W (SE)
Gain = 20 dB
-20
RL = 8 W
Gain = 20 dB
-30
Crosstalk - dB
Crosstalk - dB
-30
-40
-50
L to R
-60
-70
-60
-80
R to L
-90
L to R
-90
100
1k
10k 20k
-100
20
f − Frequency − Hz
100
1k
f − Frequency − Hz
Figure 7.
6
R to L
-50
-70
-80
-100
20
-40
Figure 8.
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10k 20k
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TYPICAL CHARACTERISTICS (continued)
OUTPUT POWER
vs
SUPPLY VOLTAGE
26
14
24
13
12
11
10
22
THD = 10%
20
18
16
14
12
THD = 1%
10
8
6
12
14
16
18
20
22
24
26
28
55
30
THD = 1%
12
14
16
18
20
22
Figure 9.
Figure 10.
OUTPUT POWER
vs
SUPPLY VOLTAGE
EFFICIENCY
vs
OUTPUT POWER
26
28
30
100
RL = 8 W (BTL)
Gain = 26 dB
90
80
70
Efficiency - %
45
THD = 10%
40
35
30
THD = 1%
25
20
24 V
18 V
60
12 V
50
40
30
15
20
10
RL = 4 W (SE)
Gain = 20 dB
10
5
0
24
VSS - Supply Voltage - V
50
PO - Output Power - W
9
8
7
6
5
4
VSS − Supply Voltage − V
65
60
THD = 10%
3
2
1
10
4
2
10
RL = 8 W (SE)
Gain = 20 dB
15
PO - Output Power - W
PO - Output Power - W
28
17
16
RL = 4 W (SE)
Gain = 20 dB
PRODUCT PREVIEW
32
30
OUTPUT POWER
vs
SUPPLY VOLTAGE
0
10
12
14
16
18
20
22
24
26
28
30
0
2
4
6
8
10
12
14
VSS − Supply Voltage − V
PO − Output Power − W
Figure 11.
Figure 12.
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18
20
7
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TYPICAL CHARACTERISTICS (continued)
EFFICIENCY
vs
OUTPUT POWER
SUPPLY CURRENT
vs
OUTPUT POWER
2
90
1.8
80
1.6
ICC − Supply Current − A
100
Efficiency - %
70
12 V
60
24 V
18 V
50
40
30
PRODUCT PREVIEW
0
4
8
12
16
20
24
28
32
36
24 V
0.8
0.6
0
40
18 V
12
16
20
24
28
Figure 14.
SUPPLY CURRENT
vs
OUTPUT POWER
POWER DISSIPATION
vs
OUTPUT POWER
Power Dissipation − W
1.2
1
24 V
0.8
0.6
18 V
0.4
12 V
0.2
8
8
Figure 13.
1.4
4
4
PO − Output Power − W
1.6
0
0
PO − Output Power − W
RL = 8 W (BTL)
Gain = 26 dB
1.8
ICC − Supply Current − A
1
0.2
2
8
1.2
12 V
RL = 8 W (BTL)
Gain = 26 dB
10
0
1.4
0.4
20
0
RL = 4 W (SE)
Gain = 20 dB
12
16
20
24
28
32
36
40
4
3.8
3.6
3.4
3.2
3
2.8
36
40
36
40
RL = 8 W (BTL)
Gain = 26 dB
2.6
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
32
24 V
18 V
12 V
0
4
8
12
16
20
24
28
PO − Output Power − W
PO − Output Power − W
Figure 15.
Figure 16.
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TPA3120D2
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APPLICATION INFORMATION
CLASS-D OPERATION
This section focuses on the class-D operation of the TPA3120D2.
Traditional Class-D Modulation Scheme
The TPA3120D2 operates in AD mode. There are two main configurations that may be used. For stereo
operation, the TPA3120D2 should be configured in a single-ended (SE) half bridge amplifier. For mono
applications, TPA3120D2 may be used as a bridge tied load (BTL) amplifier. The traditional class-D modulation
scheme, which is used in the TPA3120D2 BTL configuration, has a differential output where each output is 180
degrees out of phase and changes from ground to the supply voltage, VCC. Therefore, the differential prefiltered
output varies between positive and negative VCC, where filtered 50% duty cycle yields
0 V across the load. The traditional class-D modulation scheme with voltage and current waveforms is shown in
Figure 17.
+12 V
OUTP
0V
PRODUCT PREVIEW
-12 V
OUTN
0V
+12 V
Differential Voltage
Across Load
0V
-12 V
Current
Figure 17. Traditional Class-D Modulation Scheme's Output Voltage and Current Waveforms into an
Inductive Load With No Input
Supply Pumping
One issue often encountered in single ended (SE) class D amplifier designs is supply pumping. Power supply
pumping is a rise in the local supply voltage due to energy being driven back to the supply by operation of the
Class D amplifier. This phenomenon is most evident at low audio frequencies and when both channels are
operating at the same frequency and phase. At low levels, power supply pumping results in distortion in the
audio output due to fluctuations in supply voltage. At higher levels, pumping can cause the over-voltage
protection to operate, which temporarily shuts down the audio output.
There are several things which can be done to relieve the power supply pumping. The lowest impact is to
operate the two inputs out of phase 180 degrees. Since most audio is highly correlated, this causes the supply
pumping to be out of phase and not as severe. If this is not enough, the amount of bulk capacitance on the
supply will need to be increased. Also, some improvement can be realized by hooking other supplies this node
which can sink some of the excess current. Power supply should pumping should be tested by operating the
amplifier at low frequencies and high output levels.
Gain setting via GAIN0 and GAIN1 inputs
The gain of the TPA3120D2 is set by two input terminals, GAIN0 and GAIN1.
The gains listed in Table 1 are realized by changing the taps on the input resistors and feedback resistors inside
the amplifier. This causes the input impedance (ZI) to be dependent on the gain setting. The actual gain settings
are controlled by ratios of resistors, so the gain variation from part-to-part is small. However, the input
impedance from part-to-part at the same gain may shift by ±20% due to shifts in the actual resistance of the
input resistors.
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APPLICATION INFORMATION (continued)
For design purposes, the input network (discussed in the next section) should be designed assuming an input
impedance of 8 kΩ, which is the absolute minimum input impedance of the TPA3120D2. At the higher gain
settings, the input impedance could increase as high as 72 kΩ
Table 1. Gain Setting
GAIN1
GAIN0
AMPLIFIER GAIN (dB)
INPUT IMPEDANCE
(kΩ)
TYPICAL
TYPICAL
0
0
20
10
0
1
26
15
1
0
32
30
1
1
36
60
INPUT RESISTANCE
Changing the gain setting can vary the input resistance of the amplifier from its smallest value, 10 kΩ± 20%, to
the largest value, 60 kΩ± 20%. As a result, if a single capacitor is used in the input high-pass filter, the -3 dB or
cutoff frequency may change when changing gain steps.
PRODUCT PREVIEW
Zf
Ci
Input
Signal
IN
Zi
The -3-dB frequency can be calculated using Equation 1. Use the ZI values given in Table 1.
f =
10
1
2p Zi Ci
(1)
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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 the input impedance of the amplifier (ZI) form a
high-pass filter with the corner frequency determined in Equation 2.
-3 dB
fc =
1
2p Zi Ci
fc
(2)
Ci =
1
2p Zi fc
(3)
In this example, CI is 0.4 µF; so, one would likely choose a value of 0.47 µF as this value is commonly used. If
the gain is known and is constant, use ZI from Table 1 to calculate CI. A further consideration for this capacitor is
the leakage path from the input source through the input network (CI) and the feedback network to the load. This
leakage current creates a dc offset voltage at the input to the amplifier that reduces useful headroom, especially
in high gain applications. For this reason, a low-leakage tantalum or ceramic capacitor is the best choice. When
polarized capacitors are used, the positive side of the capacitor should face the amplifier input in most
applications as the dc level there is held at 2 V, which is likely higher than the source dc level. Note that it is
important to confirm the capacitor polarity in the application. Additionally, lead-free solder can create dc offset
voltages and it is important to ensure that boards are cleaned properly.
Single Ended Output Capacitor, Co
In single ended (SE) applications, the DC blocking capacitor forms a high pass filter with speaker impedance.
The frequency response rolls of with decreasing frequency at a rate of 20 dB/decade. The cutoff frequency is
determined by
fc = 1/2πCoZL
Table 2 shows some common component values and the associated cutoff frequencies:
Table 2. Common Filter Responses
Speaker Impedance (Ω)
CSE - DC Blocking Capacitor (µF)
fc = 60 Hz (-3 dB)
fc = 40 Hz(-3 dB)
fc = 20 Hz(-3 dB)
4
680
1000
2200
8
330
470
1000
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PRODUCT PREVIEW
The value of CI is important, as it directly affects the bass (low-frequency) performance of the circuit. Consider
the example where ZI is 20 kΩ and the specification calls for a flat bass response down to 20 Hz. Equation 2 is
reconfigured as Equation 3.
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Output Filter and Frequency Response
For the best frequency response, a flat passband output filter (second order Butterworth) may be used. The
output filter components consist of the series inductor and capacitor to ground at the LOUT and ROUT pins.
There are several possible configurations depending on the speaker impedance and whether the output
configuration is Single Ended (SE) or Bridge Tied Load (BTL). Table 3 list several possible recommended values
for the filter components.
Table 3. Recommended Filter Output Components
Output Configuration
Speaker Impedance (Ω)
Filter Inductor (µH)
Filter Capacitor (nF)
4
22
680
8
47
390
4
10
1500
8
22
680
Single Ended (SE)
Bridge Tied Load
LOUT
Lfilter
PWMOut
Cfilter
Cfilter
PRODUCT PREVIEW
ROUT
Lfilter
Lfilter
Cfilter
Figure 18. BTL Filter Configuration
Figure 19. SE Filter Configuration
Power Supply Decoupling, CS
The TPA3120D2 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling
to ensure that the output total harmonic distortion (THD) is as low as possible. Power supply decoupling also
prevents oscillations for long lead lengths between the amplifier and the speaker. The optimum decoupling is
achieved by using two capacitors of different types that target different types of noise on the power supply leads.
For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-series-resistance
(ESR) ceramic capacitor, typically 0.1 µF to 1 µF placed as close as possible to the device VCC lead works best.
For filtering lower frequency noise signals, a larger aluminum electrolytic capacitor of 220 µF or greater placed
near the audio power amplifier is recommended. The 220-µF capacitor also serves as local storage capacitor for
supplying current during large signal transients on the amplifier outputs. The PVCC terminals provide the power
to the output transistors, so a 220-µF or larger capacitor should be placed on each PVCC terminal. A 10-µF
capacitor on the AVCC terminal is adequate.
BSN and BSP Capacitors
The half H-bridge output stages use only NMOS transistors. Therefore, they require bootstrap capacitors for the
high side of each output to turn on correctly. A 220-nF ceramic capacitor, rated for at least 25 V, must be
connected from each output to its corresponding bootstrap input. Specifically, one 220-nF capacitor must be
connected from LOUT to BSL, and one 220-nF capacitor must be connected from ROUT to BSR.
The bootstrap capacitors connected between the BSx pins and corresponding output function as a floating
power supply for the high-side N-channel power MOSFET gate drive circuitry. During each high-side switching
cycle, the bootstrap capacitors hold the gate-to-source voltage high enough to keep the high-side MOSFETs
turned on.
12
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TPA3120D2
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SLOS507 – MARCH 2007
VCLAMP Capacitor
To ensure that the maximum gate-to-source voltage for the NMOS output transistors is not exceeded, one
internal regulator clamps the gate voltage. One 1-µF capacitor must be connected from VCLAMP (pin 11) to
ground and must be rated for at least 16 V. The voltages at the VCLAMP terminal may vary with VCC and may
not be used for powering any other circuitry.
VBYP Capacitor Selection
The scaled supply reference (VBYP) nominally provides an AVCC/8 internal bias for the preamplifier stages. The
external capacitor for this reference (CBYP) is a critical component and serves several important functions. During
start-up or recovery from shutdown mode, CBYP determines the rate at which the amplifier starts. The start up
time is proportional to 0.5 sec per µ. Thus, the recommended 1µF cap results in a start-up time of 500 msec.
The second function is to reduce noise produced by the power supply caused by coupling with the output drive
signal. This noise could result in degraded PSRR and THD + N.
The circuit is designed for a CBYP value of 1 µF for best pop performance. The inputs caps should be the same
value. A ceramic or tantalum low-ESR capacitor is recommended.
The TPA3120D2 employs a shutdown mode of operation designed to reduce supply current (ICC) to the absolute
minimum level during periods of nonuse for power conservation. The SHUTDOWN input terminal should be held
high (see specification table for trip point) during normal operation when the amplifier is in use. Pulling
SHUTDOWN low causes the outputs to mute and the amplifier to enter a low-current state. Never leave
SHUTDOWN unconnected, because amplifier operation would be unpredictable.
For the best power-up pop performance, place the amplifier in the shutdown or mute mode prior to applying the
power supply voltage.
MUTE Operation
The MUTE pin is an input for controlling the output state of the TPA3120D2. A logic high on this terminal causes
the outputs to run at a constant 50% duty cycle. A logic low on this pin enables the outputs. This terminal may
be used as a quick disable/enable of outputs when changing channels on a television or transitioning between
different audio sources.
The MUTE terminal should never be left floating. For power conservation, the SHUTDOWN terminal should be
used to reduce the quiescent current to the absolute minimum level.
USING LOW-ESR CAPACITORS
Low-ESR capacitors are recommended throughout this application section. A real (as opposed to ideal)
capacitor can be modeled simply as a resistor in series with an ideal capacitor. The voltage drop across this
resistor minimizes the beneficial effects of the capacitor in the circuit. The lower the equivalent value of this
resistance, the more the real capacitor behaves like an ideal capacitor.
SHORT-CIRCUIT PROTECTION
The TPA3120D2 has short-circuit protection circuitry on the outputs that prevents damage to the device during
output-to-output shorts and output-to-GND shorts after the filter and output capacitor (at the speaker terminal.)
Directly at the device terminals, the protection circuitry prevents damage to device during output-to-output,
output-ground, and output to supply. When a short circuit is detected on the outputs, the part immediately
disables the output drive. This is an unlatched fault. Normal operation is restored when the fault is removed.
THERMAL PROTECTION
Thermal protection on the TPA3120D2 prevents damage to the device when the internal die temperature
exceeds 150°C. There is a ±15°C tolerance on this trip point from device to device. Once the die temperature
exceeds the thermal set point, the device enters into the shutdown state and the outputs are disabled. This is
not a latched fault. The thermal fault is cleared once the temperature of the die is reduced by 30°C. The device
begins normal operation at this point with no external system interaction.
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PRODUCT PREVIEW
SHUTDOWN OPERATION
TPA3120D2
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SLOS507 – MARCH 2007
PRINTED-CIRCUIT BOARD (PCB) LAYOUT
Because the TPA3120D2 is a class-D amplifier that switches at a high frequency, the layout of the printed-circuit
board (PCB) should be optimized according to the following guidelines for the best possible performance.
• Decoupling capacitors—The high-frequency 0.1µF decoupling capacitors should be placed as close to the
PVCC (pins 1, 3, 10, and 12) and AVCC (pins 19 and 20) terminals as possible. The VBYP (pin 7) capacitor
and VCLAMP (pin 11) capacitor should also be placed as close to the device as possible. Large (220 µF or
greater) bulk power supply decoupling capacitors should be placed near the TPA3120D2 on the PVCCL and
PVCCR terminals.
• Grounding—The AVCC (pins 19 and 20) decoupling capacitor and VBYP (pin 7) capacitor should each be
grounded to analog ground (AGND, pins 8 and 9). The PVCCx decoupling capacitors and VCLAMP
capacitors should each be grounded to power ground (PGND, pins 13, 14, 23, and 24). Analog ground and
power ground should be connected at the thermal pad, which should be used as a central ground connection
or star ground for the TPA3120D2.
• Output filter—The reconstruction filter (L1, L2, C9, and C16) should be placed as close to the output
terminals as possible for the best EMI performance. The capacitors should be grounded to power ground.
• Thermal Pad—The thermal pad must be soldered to the PCB for proper thermal performance and optimal
reliability. The dimensions of the thermal pad and thermal land are described in the mechanical section at the
back of the data sheet. See TI Technical Briefs SLMA002 and SLOA120 for more information about using
the thermal pad. For recommended PCB footprints, see figures at the end of this data sheet.
PRODUCT PREVIEW
For an example layout, see the TPA3120D2 Evaluation Module (TPA3120D2EVM) User Manual, (SLOU189).
Both the EVM user manual and the thermal pad application note are available on the TI Web site at
http://www.ti.com.
14
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TPA3120D2
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SLOS507 – MARCH 2007
BASIC MEASUREMENT SYSTEM
This application note focuses on methods that use the basic equipment listed below:
• Audio analyzer or spectrum analyzer
• Digital multimeter (DMM)
• Oscilloscope
• Twisted-pair wires
• Signal generator
• Power resistor(s)
• Linear regulated power supply
• Filter components
• EVM or other complete audio circuit
The generator output and amplifier input must be ac-coupled. However, the EVMs already have the ac-coupling
capacitors, (CIN), so no additional coupling is required. The generator output impedance should be low to avoid
attenuating the test signal, and is important because the input resistance of APAs is not high. Conversely, the
analyzer-input impedance should be high. The output resistance, ROUT, of the APA is normally in the hundreds
of milliohms and can be ignored for all but the power-related calculations.
Figure 20(a) shows a class-AB amplifier system. It takes an analog signal input and produces an analog signal
output. This amplifier circuit can be directly connected to the AP-II or other analyzer input.
This is not true of the class-D amplifier system shown in Figure 20(b), which requires low-pass filters in most
cases in order to measure the audio output waveforms. This is because it takes an analog input signal and
converts it into a pulse-width modulated (PWM) output signal that is not accurately processed by some
analyzers.
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PRODUCT PREVIEW
Figure 20 shows the block diagrams of basic measurement systems for class-AB and class-D amplifiers. A sine
wave is normally used as the input signal because it consists of the fundamental frequency only (no other
harmonics are present). An analyzer is then connected to the APA output to measure the voltage output. The
analyzer must be capable of measuring the entire audio bandwidth. A regulated dc power supply is used to
reduce the noise and distortion injected into the APA through the power pins. A System Two audio
measurement system (AP-II) (Reference 1) by Audio Precision includes the signal generator and analyzer in one
package.
TPA3120D2
www.ti.com
SLOS507 – MARCH 2007
Power Supply
Signal
Generator
APA
RL
Analyzer
20 Hz - 20 kHz
(a) Basic Class-AB
Power Supply
PRODUCT PREVIEW
Lfilt
Signal
Generator
Class-D APA
Cfilt
RL
(b) Traditional Class-D
Figure 20. Audio Measurement Systems
16
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Analyzer
20 Hz - 20 kHz
TPA3120D2
www.ti.com
SLOS507 – MARCH 2007
SE Input and SE Output (TPA312002 Stereo Configuration)
The SE input and output configuration is used with class-AB amplifiers. A block diagram of a fully SE
measurement circuit is shown in Figure 21. SE inputs normally have one input pin per channel. In some cases,
two pins are present; one is the signal and the other is ground. SE outputs have one pin driving a load through
an output ac coupling capacitor and the other end of the load is tied to ground. SE inputs and outputs are
considered to be unbalanced, meaning one end is tied to ground and the other to an amplifier input/output.
The generator should have unbalanced outputs, and the signal should be referenced to the generator ground for
best results. Unbalanced or balanced outputs can be used when floating, but they may create a ground loop that
will effect the measurement accuracy. The analyzer should have balanced inputs to cancel out any
common-mode noise in the measurement.
Evaluation Module
Audio Power
Amplifier
Generator
Analyzer
CIN
RGEN
RIN
Lfilt
CL
Cfilt
Twisted-Pair Wire
RL
RANA
CANA
RANA
CANA
Twisted-Pair Wire
Figure 21. SE Input—SE Output Measurement Circuit
The following general rules should be followed when connecting to APAs with SE inputs and outputs:
• Use an unbalanced source to supply the input signal.
• Use an analyzer with balanced inputs.
• Use twisted pair wire for all connections.
• Use shielding when the system environment is noisy.
• Ensure the cables from the power supply to the APA, and from the APA to the load, can handle the large
currents (see Table 4)
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PRODUCT PREVIEW
VGEN
TPA3120D2
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SLOS507 – MARCH 2007
DIFFERENTIAL INPUT AND BTL OUTPUT (TPA3120D2 Mono Configuration)
Many of the class-D APAs and many class-AB APAs have differential inputs and bridge-tied load (BTL) outputs.
Differential inputs have two input pins per channel and amplify the difference in voltage between the pins.
Differential inputs reduce the common-mode noise and distortion of the input circuit. BTL is a term commonly
used in audio to describe differential outputs. BTL outputs have two output pins providing voltages that are 180
degrees out of phase. The load is connected between these pins. This has the added benefits of quadrupling
the output power to the load and eliminating a dc blocking capacitor.
A block diagram of the measurement circuit is shown in Figure 22. The differential input is a balanced input,
meaning the positive (+) and negative (-) pins have the same impedance to ground. Similarly, the SE output
equates to a balanced output.
Evaluation Module
Audio Power
Amplifier
Generator
CIN
VGEN
Analyzer
Lfilt
RGEN
RIN
Cfilt
CIN
Lfilt
RGEN
RIN
RL
Cfilt
PRODUCT PREVIEW
Twisted-Pair Wire
RANA
CANA
RANA
CANA
Twisted-Pair Wire
Figure 22. Differential Input, BTL Output Measurement Circuit
The generator should have balanced outputs, and the signal should be balanced for best results. An unbalanced
output can be used, but it may create a ground loop that affects the measurement accuracy. The analyzer must
also have balanced inputs for the system to be fully balanced, thereby cancelling out any common-mode noise
in the circuit and providing the most accurate measurement.
The following general rules should be followed when connecting to APAs with differential inputs and BTL
outputs:
• Use a balanced source to supply the input signal.
• Use an analyzer with balanced inputs.
• Use twisted-pair wire for all connections.
• Use shielding when the system environment is noisy.
• Ensure that the cables from the power supply to the APA, and from the APA to the load, can handle the large
currents (see Table 4).
Table 4 shows the recommended wire size for the power supply and load cables of the APA system. The real
concern is the dc or ac power loss that occurs as the current flows through the cable. These recommendations
are based on 12-inch long wire with a 20-kHz sine-wave signal at 25°C.
Table 4. Recommended Minimum Wire Size for Power Cables
18
DC POWER LOSS
(MW)
AWG Size
AC POWER LOSS
(MW)
POUT (W)
RL(Ω)
10
4
18
22
16
40
18
42
2
4
18
22
3.2
8
3.7
8.5
1
8
22
28
2
8
2.1
8.1
< 0.75
8
22
28
1.5
6.1
1.6
6.2
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PACKAGE OPTION ADDENDUM
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20-Mar-2007
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
TPA3120D2PWP
PREVIEW
HTSSOP
PWP
24
60
TBD
Call TI
Call TI
TPA3120D2PWPR
PREVIEW
HTSSOP
PWP
24
2000
TBD
Call TI
Call TI
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.
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Addendum-Page 1
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