ETC TPA032D02DCAR

TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
D
D
D
D
D
D
D
D
Extremely Efficient Class-D Stereo
Operation
Drives L and R Channels
10-W BTL Output Into 4 Ω From 12 V
32-W Peak Music Power
Fully Specified for 12-V Operation
Low Shutdown Current
Thermally-Enhanced PowerPAD SurfaceMount Packaging
Thermal and Under-Voltage Protection
description
The TPA032D02 is a monolithic power IC stereo
audio amplifier that operates in extremely efficient
Class-D operation, using the high switching speed
of power DMOS transistors to replicate the analog
input signal through high-frequency switching of
the output stage. This allows the TPA032D02 to
be configured as a bridge-tied load (BTL) amplifier
capable of delivering up to 10 W of continuous
average power into a 4-Ω load at 0.5% THD+N
from a 12-V power supply in the high-fidelity audio
frequency range (20 Hz to 20 kHz). A BTL
configuration eliminates the need for external
coupling capacitors on the output. A chip-level
shutdown control is provided to limit total supply
current to 20 µA, making the device ideal for
battery-powered applications.
DCA PACKAGE
(TOP VIEW)
SHUTDOWN
MUTE
AGND
LINN
LINP
LCOMP
AGND
VDD
LPVDD
LOUTP
LOUTP
PGND
PGND
LOUTN
LOUTN
LPVDD
VCCREG
NC
NC
AGND
PVDD
VCP
NC
CP1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
COSC
AGND
AGND
RINN
RINP
RCOMP
FAULT0
FAULT1
RPVDD
ROUTP
ROUTP
PGND
PGND
ROUTN
ROUTN
RPVDD
VCC
NC
NC
V2P5
PVDD
PGND
NC
CP2
NC – No internal connection
The output stage is compatible with a range of power supplies from 8 V to 14 V. Protection circuitry is included
to increase device reliability: thermal and under-voltage shutdown, with a status feedback terminal for use when
any error condition is encountered.
The high switching frequency of the TPA032D02 allows the output filter to consist of three small capacitors and
two small inductors per channel. The high switching frequency also allows for good THD+N performance.
The TPA032D02 is offered in the thermally enhanced 48-pin PowerPAD TSSOP surface-mount package
(designator DCA).
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 Incorporated.
Copyright  2000, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
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1
+
_
LINP
LINN
10 kΩ
CONTROL and
STARTUP
LOGIC
10 kΩ
1.5 V
VCP
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+
_
VDD
PVDD
GATE
DRIVE
5-V
REGULATOR
and BIASES
VCP
RAMP
GENERATOR
_
RCOMP
RINN
PVDD
VCP-UVLO
DETECT
GATE
DRIVE
RPVDD
10 kΩ
10 kΩ
VCP
DOUBLER
CHARGE PUMP
PVDD
1.5 V
RPVDD
AGND
RPVDD
GATE
DRIVE
CP1
CP2
NOTE A: LPVDD, RPVDD, and PVDD are externally connected. AGND and PGND are externally connected.
VCP
PVDD
ROUTN
ROUTP
PGND
VCCREG
VCC
V2P5
+
+
_
RINP
MUTE
PVDD
RPVDD
COSC
SHUTDOWN
LPVDD
LCOMP
VDD
THERMAL
DETECT
GATE
DRIVE
Template Release Date: 7–11–94
LPVDD
TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
LPVDD
PVDD
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
FAULT1
FAULT0
LOUTN
LOUTP
schematic
2
LPVDD
VCP
TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
Terminal Functions
TERMINAL
NAME
DESCRIPTION
NO.
AGND
3, 7, 20,
46, 47
Analog ground for Class-D analog circuitry
COSC
48
Connect a capacitor from analog ground to this terminal to set the frequency of the ramp reference signal.
CP1
24
First diode node for charge pump
CP2
25
First inverter switching node for charge pump
FAULT0
42
Logic level fault0 output signal. Lower order bit of the two fault signals with open drain output.
FAULT1
41
Logic level fault1 output signal. Higher order bit of the two fault signals with open drain output.
LCOMP
6
Compensation capacitor terminal for left-channel Class-D amplifier
LINN
4
Class-D left-channel negative input
LINP
5
Class-D left-channel positive input
LOUTN
14, 15
Class-D amplifier left-channel negative output of H-bridge
LOUTP
10, 11
Class-D amplifier left-channel positive output of H-bridge
LPVDD
9, 16
Class-D amplifier left-channel power supply
MUTE
2
Active-low TTL logic-level mute input signal. When MUTE is held low, the selected amplifier is muted. When MUTE
is held > high, the device operates normally. When the Class-D amplifier is muted, the low-side output transistors
are turned on, shorting the load to ground.
NC
18, 19,
23, 26,
30, 31
No connection
PGND
12, 13
Power ground for left-channel H–bridge only
PGND
27
PGND
36, 37
Power ground for right-channel H-bridge only
PVDD
RCOMP
21, 28
43
VDD supply for charge-pump and gate drive circuitry
Compensation capacitor terminal for right-channel Class-D amplifier
RINN
45
Class-D right-channel negative input
RINP
44
Class-D right-channel positive input
Power ground for charge pump only
RPVDD
ROUTN
33, 40
Class-D amplifier right-channel power supply
34, 35
Class-D amplifier right-channel negative output of H-bridge
ROUTP
38, 39
Class-D amplifier right-channel positive output of H-bridge
SHUTDOWN
1
Active-low TTL logic-level shutdown input signal. When SHUTDOWN is held low, the device goes into shutdown
mode. When SHUTDOWN is held high, the device operates normally.
VCC
VCCREG
32
5V supply to logic. This terminal is typically connected to VCCREG.
17
5-V regulator output. This terminal requires a 1-µF capacitor to ground for stability reasons.
V2P5
29
2.5V internal reference bypass. This terminal requires a capacitor to ground.
VCP
22
Connect a capacitor from this terminal to power ground to provide storage for the charge pump output voltage.
VDD
8
VDD bias supply for analog circuitry. This terminal needs to be well filtered to prevent degrading the device
performance.
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TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
Class-D amplifier faults
Table 1. Class-D Amplifier Fault Table
FAULT 0
FAULT 1
1
1
No fault. The device is operating normally.
DESCRIPTION
0
1
Charge pump under-voltage lock-out (VCP-UV) fault. All low-side transistors are turned on, shorting the load to
ground. Once the charge pump voltage is restored, normal operation resumes, but FAULT1 is still active. This is not
a latched fault, however. FAULT1 is cleared by cycling MUTE, SHUTDOWN, or the power supply.
0
0
Thermal fault. All the low-side transistors are turned on, shorting the load to ground. Once the junction temperature
drops 20°C, normal operation resumes (not a latched fault). But the FAULTx terminals are still set and are cleared
by cycling MUTE, SHUTDOWN, or the power supply.
AVAILABLE OPTIONS
TA
PACKAGED DEVICES
TSSOP†
(DCA)
– 40°C to 125°C
TPA032D02DCA
† The DCA package is available in left-ended tape and reel. To order
a taped and reeled part, add the suffix R to the part number (e.g.,
TPA032D02DCAR).
4
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TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
absolute maximum ratings over operating free-air temperature range, TC = 25°C (unless otherwise
noted)†
Supply voltage, (VDD, PVDD, LPVDD, RPVDD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 V
Logic supply voltage, (VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 V
Input voltage, VI (MUTE, MODE, SHUTDOWN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 0.3 V to 7 V
Output current, IO (FAULT0, FAULT1), open drain terminated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 mA
Supply/load voltage, (FAULT0, FAULT1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 V
Charge pump voltage, VCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PVDD + 20 V
Continuous H-bridge output current (1 H-bridge conducting) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 A
Pulsed H-Bridge output current, each output, Imax (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 A
Continuous VCCREG output current, IO (VCCREG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 mA
Continuous total power dissipation, TC = 25°C . . . . . . . . . . . . . . . . . . . . . . . . . . . See Dissipation Rating Table
Operating virtual junction temperature range, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 40°C to 150°C
Operating case temperature range, TC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 40°C to 125°C
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . – 65°C to 260°C
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260°C
† Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTE 1: Pulse duration = 10 ms, duty cycle
2%
v
DISSIPATION RATING TABLE
PACKAGE
TA ≤ 25°C‡
POWER RATING
DERATING FACTOR
ABOVE TA = 25°C
TA = 70°C
POWER RATING
TA = 85°C
POWER RATING
DCA
5.6 W
44.8 mW/°C
3.6 W
2.9 W
‡ Please see the Texas Instruments document, PowerPAD Thermally Enhanced Package Application
Report (literature number SLMA002), for more information on the PowerPAD package. The thermal data
was measured on a PCB layout based on the information in the section entitled Texas Instruments
Recommended Board for PowerPAD on page 33 of the before mentioned document.
recommended operating conditions
MIN
Supply voltage, VDD, PVDD, LPVDD, RPVDD
Logic supply voltage, VCC
High-level input voltage, VIH (MUTE, SHUTDOWN)
Low-level input voltage, VIL (MUTE, SHUTDOWN)
NOM
8
14
V
5.5
V
2
VDD + 0.3 V
0.8
V
– 0.3
1
PWM frequency
100
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UNIT
4.5
Audio inputs, LINN, LINP, RINN, RINP, differential input voltage
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MAX
250
500
V
VRMS
kHZ
5
TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
electrical characteristics Class-D amplifier, VDD = PVDD = LPVDD = RPVDD = 12 V, RL = 4 Ω to 8 Ω,
TA = 25°C, See Figure 1 (unless otherwise noted)
PARAMETER
Power supply rejection ratio
TEST CONDITIONS
IDD
IDD(Mute)
Supply current
VDD = PVDD = xPVDD = 11 V to 13 V
No output filter connected
Supply current, mute mode
IDD(S/D)
|IIH|
MIN
TYP
MAX
–40
UNIT
dB
25
35
mA
MUTE = 0 V
10
18
mA
Supply current, shutdown mode
SHUTDOWN = 0 V
20
30
µA
High-level input current (MUTE, MODE,
SHUTDOWN)
VIH = 5.25 V
10
µA
|IIL|
Low-level input current (MUTE, MODE,
SHUTDOWN)
VIL = – 0.3 V
10
µA
rDS(on)
Static drain-to-source on-state resistance
(high-side + low-side FETs)
IDD = 0.5 A
800
mΩ
rDS(on)
Matching, high-side to high-side, low-side to
low-side, same channel
720
95%
98%
operating characteristics, Class-D amplifier, VDD = PVDD = LPVDD = RPVDD = 12 V, RL = 4 Ω,
TA = 25°C, See Figure 1 (unless otherwise noted)
PARAMETER
PO
AV
TEST CONDITIONS
Output power
f = 1 kHz,
THD = 0.5%, per channel,
Device soldered on PCB,
See Note 2
Efficiency
PO = 10 W,
f = 1 kHz
MIN
77%
92%
Noise floor
Dynamic range
f = 1 kHz
Frequency response bandwidth, post output filter, – 3 dB
–60
dB
80
dB
–50
Maximum output power bandwidth
6
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dB
95%
20
ZI
Input impedance
NOTE 2: Output power is thermally limited, TA = 23°C
UNIT
W
25
Left/right channel gain matching
BOM
MAX
10
Gain
Crosstalk
TYP
dB
20 000
Hz
20
kHz
kΩ
TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
operating characteristics, Class-D amplifier, VDD = PVDD = LPVDD = RPVDD = 12 V, RL = 8 Ω,
TA = 25°C, See Figure 2 (unless otherwise noted)
PARAMETER
PO
AV
TEST CONDITIONS
Output power,
THD = 0.5%, per channel,
Device soldered on PCB,
See Note 2
Efficiency
PO = 7.5 W,
f = 1 kHz
MIN
TYP
7.5
W
25
92%
Noise floor
f = 1 kHz
Frequency response bandwidth, post output filter, – 3 dB
dB
95%
–60
dB
80
dB
Dynamic range
Crosstalk
UNIT
85%
Gain
Left/right channel gain matching
BOM
MAX
–50
20
Maximum output power bandwidth
ZI
Input impedance
NOTE 2: Output power is thermally limited, TA = 85°C
dB
20 000
Hz
20
kHz
10
kΩ
operating characteristics, VCC 5-V regulator, TA = 25°C (unless otherwise noted)
PARAMETER
VO
TEST CONDITIONS
VDD = PVDD = LPVDD = RPVDD = 8 V to 14 V,
IO = 0 to 90 mA
Output voltage
MIN
TYP
4.5
MAX
5.5
IOS
Short-circuit output current
VDD = PVDD = LPVDD = RPVDD = 8 V to 14 V†
90
† Pulse width must be limited to prevent exceeding the maximum operating virtual junction temperature of 150°C.
UNIT
V
mA
thermal shutdown
PARAMETER
TEST CONDITIONS
Thermal shutdown temperature
Thermal shutdown hysteresis
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MIN
TYP
MAX
UNIT
165
°C
30
°C
7
TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
PARAMETER MEASUREMENT INFORMATION
FAULT0
FAULT1
1
VCCREG
VCCREG
2
SHUTDOWN
LOUTN
MUTE
42
41
14,15
15 µH
0.22 µF
12 V
9,16
LOUTP
1 µF
5
Balanced
Differential
Input Signal
4
1 µF
43
1000 pF
LINN
1 µF
4Ω
10,11
15 µH
29
LCOMP
1 µF
RCOMP
1000 pF
VDD
48
4Ω
LINP
V2P5
6
1 µF
0.22 µF
LPVDD
8
12 V
COSC
1000 pF
VCCREG
17
To VCC
0.1 µF
1 µF
44
Balanced
Differential
Input Signal
45
RINP
CP1
RINN
47 nF
1 µF
33,34
12 V
3, 7,20,46,47
12,13,27,36,37
21, 28
12 V
24
CP2
RPVDD
AGND
VCP
25
22
0.1 µF
PGND
PVDD
ROUTN
34,35
500 kΩ
0.22 µF
32
To VCCREG
15 µH
0.22 µF
VCC
100 kΩ
ROUTP
38,39
Figure 1. 12-V, 4-Ω Test Circuit
8
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15 µH
TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
PARAMETER MEASUREMENT INFORMATION
FAULT0
FAULT1
1
VCCREG
VCCREG
2
SHUTDOWN
LOUTN
MUTE
42
41
14,15
30 µH
0.1 µF
12 V
9,16
LOUTP
1 µF
5
Balanced
Differential
Input Signal
4
1 µF
43
1000 pF
LINN
1 µF
8Ω
10,11
30 µH
29
LCOMP
1 µF
RCOMP
1000 pF
VDD
48
8Ω
LINP
V2P5
6
1 µF
0.1 µF
LPVDD
8
12 V
COSC
1000 pF
VCCREG
17
To VCC
0.1 µF
1 µF
44
Balanced
Differential
Input Signal
45
RINP
CP1
RINN
47 nF
1 µF
33,34
12 V
3, 7,20,46,47
12,13,27,36,37
21, 28
12 V
24
CP2
RPVDD
AGND
VCP
25
22
0.1 µF
PGND
PVDD
ROUTN
34,35
500 kΩ
0.1 µF
32
To
VCCREG
30 µH
0.1 µF
VCC
ROUTP
100 kΩ
38,39
30 µH
Figure 2. 12-V, 8-Ω Test Circuit
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TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
APPLICATION INFORMATION
1
To System
Control
12 V
MUTE
9,16
1 µF
1 µF
10 µF
SHUTDOWN
2
VCCREG
LPVDD
100 kΩ
FAULT0
1 µF
5
Left Class-D Balanced
Differential Input
Signal
4
LINP
FAULT1
LINN
LOUTN
1 µF
6
1 µF
RCOMP
COSC
V2P5
1000 pF
VDD
1 µF
44
12 V
1 µF
10 µF
3, 7,20,46,47
21, 28
1 µF
VCCREG
10,11
15 µH
29
8
12 V
1 µF
1 µF
17
VCC
RINN
1 µF
33,34
1 µF
12,13,27,36,37
12 V
RINP
45
4Ω
0.22 µF
LOUTP
48
15 µH
14,15
0.22 µF
1000 pF
Right Class-D Balanced
Differential Input
Signal
To System
Control
41
LCOMP
43
1000 pF
100 kΩ
42
RPVDD
AGND
PGND
CP1
PVDD
24
47 nF
CP2
VCP
ROUTN
25
22
0.1 µF
15 µH
34,35
0.22 µF
0.1 µF
VDD
32
1 µF
0.22 µF
VCC
ROUTP
500 kΩ
To
VCCREG
100 kΩ
38,39
15 µH
0.1 µF
NOTE A:
= power ground and
= analog ground
Figure 3. TPA032D02 Typical Configuration Application Circuit
10
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4Ω
TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
APPLICATION INFORMATION
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 ZI, the TPA032D02’s input resistance forms a
high-pass filter with the corner frequency determined in equation 8.
–3 dB
f
c(highpass)
+ 2 p Z1 C
(8)
I I
ZI is nominally 10 kΩ
fc
The value of CI is important to consider as it directly affects the bass (low frequency) performance of the circuit.
Consider the example where the specification calls for a flat bass response down to 40 Hz. Equation 8 is
reconfigured as equation 9.
CI
+ 2 p 1Z fc
(9)
I
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 low-leakage
tantalum or ceramic capacitor is the best choice for the input capacitors. When polarized capacitors are used,
the positive side of the capacitor should face the amplifier input, as the dc level there is held at 1.5 V, which is
likely higher than the source dc level. Please note that it is important to confirm the capacitor polarity in the
application.
differential input
The TPA032D02 has differential inputs to minimize distortion at the input to the IC. Since these inputs nominally
sit at 1.5 V, dc-blocking capacitors are required on each of the four input terminals. If the signal source is
single-ended, optimal performance is achieved by treating the signal ground as a signal. In other words,
reference the signal ground at the signal source, and run a trace to the dc-blocking capacitor, which should be
located physically close to the TPA032D02. If this is not feasible, it is still necessary to locally ground the unused
input terminal through a dc-blocking capacitor.
power supply decoupling, CS
The TPA032D02 is a high-performance Class-D 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-seriesresistance (ESR) ceramic capacitor, typically 0.1 µF placed as close as possible to the device’s various VDD
leads, 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.
The TPA032D02 has several different power supply terminals. This was done to isolate the noise resulting from
high-current switching from the sensitive analog circuitry inside the IC.
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TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
APPLICATION INFORMATION
mute and shutdown modes
The TPA032D02 employs both a mute and a shutdown mode of operation designed to reduce supply current,
IDD, to the absolute minimum level during periods of non-use for battery-power conservation. The SHUTDOWN
input terminal should be held high 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, IDD = 20 µA. Mute mode alone
reduces IDD to 10 mA.
using low-ESR capacitors
Low-ESR capacitors are recommended throughout this applications 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.
output filter components
The output inductors are key elements in the performance of the class-D audio amplifier system. It is important
that these inductors have a high enough current rating and a relatively constant inductance over frequency and
temperature. The current rating should be higher than the expected maximum current to avoid magnetically
saturating the inductor. When saturation occurs, the inductor loses its functionality and looks like a short circuit
to the PWM signal, which increases the harmonic distortion considerably.
A shielded inductor may be required if the class-D amplifier is placed in an EMI sensitive system; however, the
switching frequency is low for EMI considerations and should not be an issue in most systems. The dc series
resistance of the inductor should be low to minimize losses due to power dissipation in the inductor, which
reduces the efficiency of the circuit.
Capacitors are important in attenuating the switching frequency and high frequency noise, and in supplying
some of the current to the load. It is best to use capacitors with low equivalent-series-resistance (ESR). A low
ESR means that less power is dissipated in the capacitor as it shunts the high-frequency signals. Placing these
capacitors in parallel also parallels their ESR, effectively reducing the overall ESR value. The voltage rating is
also important, and, as a rule of thumb, should be 2 to 3 times the maximum rms voltage expected to allow for
high peak voltages and transient spikes. These output filter capacitors should be stable over temperature since
large currents flow through them.
12
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TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
APPLICATION INFORMATION
efficiency of class-D vs linear operation
Amplifier efficiency is defined as the ratio of output power delivered to the load to power drawn from the supply.
In the efficiency equation below, PL is power across the load and PSUP is the supply power.
Efficiency
+ h + PP L
SUP
A high-efficiency amplifier has a number of advantages over one with lower efficiency. One of these advantages
is a lower power requirement for a given output, which translates into less waste heat that must be removed
from the device, smaller power supply required, and increased battery life.
Audio power amplifier systems have traditionally used linear amplifiers, which are well known for being
inefficient. Class-D amplifiers were developed as a means to increase the efficiency of audio power amplifier
systems.
A linear amplifier is designed to act as a variable resistor network between the power supply and the load. The
transistors operate in their linear region and voltage that is dropped across the transistors (in their role as
variable resistors) is lost as heat, particularly in the output transistors.
The output transistors of a class-D amplifier switch from full OFF to full ON (saturated) and then back again,
spending very little time in the linear region in between. As a result, very little power is lost to heat because the
transistors are not operated in their linear region. If the transistors have a low on-resistance, little voltage is
dropped across them, further reducing losses. The ideal class-D amplifier is 100% efficient, which assumes that
both the on-resistance (rDS(on)) and the switching times of the output transistors are zero.
the ideal class-D amplifier
To illustrate how the output transistors of a class-D amplifier operate, a half-bridge application is examined first
(see Figure 4).
VDD
M1
VA
IL
IOUT
+
L
M2
RL
CL
C
VOUT
–
Figure 4. Half-Bridge Class-D Output Stage
Figures 5 and 6 show the currents and voltages of the half-bridge circuit. When transistor M1 is on and M2 is
off, the inductor current is approximately equal to the supply current. When M2 switches on and M1 switches
off, the supply current drops to zero, but the inductor keeps the inductor current from dropping. The additional
inductor current is flowing through M2 from ground. This means that VA (the voltage at the drain of M2, as shown
in Figure 4) transitions between the supply voltage and slightly below ground. The inductor and capacitor form
a low-pass filter, which makes the output current equal to the average of the inductor current. The low pass filter
averages VA, which makes VOUT equal to the supply voltage multiplied by the duty cycle.
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TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
APPLICATION INFORMATION
the ideal class-D amplifier (continued)
Control logic is used to adjust the output power, and both transistors are never on at the same time. If the output
voltage is rising, M1 is on for a longer period of time than M2.
Inductor Current
Output Current
Current
Supply Current
0
M1 on M1 off M1 on
M2 off M2 on M2 off
Time
Figure 5. Class-D Currents
VDD
Voltage
VA
VOUT
0
M1 on M1 off M1 on
M2 off M2 on M2 off
Time
Figure 6. Class-D Voltages
14
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TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
APPLICATION INFORMATION
the ideal class-D amplifier (continued)
Given these plots, the efficiency of the class-D device can be calculated and compared to an ideal linear
amplifier device. In the derivation below, a sine wave of peak voltage (VP) is the output from an ideal class-D
and linear amplifier and the efficiency is calculated.
CLASS-D
V L(rms)
+ Ǹ2
V L(rms)
ǒ Ǔ+
Average I DD
PL
LINEAR
VP
+ VL
+ VDD
P SUP
+
V DD
V L(rms)
V DD
IL
P SUP
Efficiency
I L(rms)
+
V L(rms)2
RL
+2 R
ǒ Ǔ+p
ǒ Ǔ
P SUP
V L(rms)
+ VDD
Efficiency
V DD
L
VP
2
RL
ǒ Ǔ+
Average I DD
V DD V P
RL
2
p
+ h + PP L
SUP
+ h + PP L
Efficiency
SUP
Efficiency
V P2
Average I DD
Average I DD
I L(rms)
PL
+ Ǹ2
VP
V P2
2R L
+ h + VDD
V
2
p
+ h +1
Efficiency
+ h + p4
V
V
P
RL
P
DD
In the ideal efficiency equations, assume that VP = VDD, which is the maximum sine wave magnitude without
clipping. Then, the highest efficiency that a linear amplifier can have without clipping is 78.5%. A class-D
amplifier, however, can ideally have an efficiency of 100% at all power levels.
The derivation above applies to an H-bridge as well as a half-bridge. An H-bridge requires approximately twice
the supply current but only requires half the supply voltage to achieve the same output power—factors that
cancel in the efficiency calculation. The H-bridge circuit is shown in Figure 7.
VDD
M1
VA
VDD
IL
IOUT
L
M4
+ VOUT –
M2
L
RL
CL
CL
M3
Figure 7. H-Bridge Class-D Output Stage
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15
TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
APPLICATION INFORMATION
losses in a real-world class-D amplifier
Losses make class-D amplifiers nonideal, and reduce the efficiency below 100%. These losses are due to the
output transistors having a nonzero rDS(on), and rise and fall times that are greater than zero.
The loss due to a nonzero rDS(on) is called conduction loss, and is the power lost in the output transistors at
nonswitching times, when the transistor is on (saturated). Any rDS(on) above 0 Ω causes conduction loss.
Figure 8 shows an H-bridge output circuit simplified for conduction loss analysis and can be used to determine
new efficiencies with conduction losses included.
VDD = 12 V
rDS(on)
0.36 Ω
5 MΩ
rDS(off)
0.36 Ω
rDS(on)
RL
4Ω
rDS(off)
5 MΩ
Figure 8. Output Transistor Simplification for Conduction Loss Calculation
The power supplied, PSUP, is determined to be the power output to the load plus the power lost in the transistors,
assuming that there are always two transistors on.
Efficiency
+ h + PP L
SUP
Efficiency
Efficiency
+ h + I2 2r
+ h + 2r
DS(on)
RL
ǒ
ǒ
DS(on)
+ h + 95%
Efficiency + h + 85%
Efficiency
I 2R L
) I2RL
) RL
Ǔ
+ 0.1 Ω, RL + 4 Ω
at all output levels r DS(on) + 0.36 Ω, R L + 4 Ω
at all output levels r DS(on)
16
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Ǔ
TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
APPLICATION INFORMATION
losses in a real-world class-D amplifier (continued)
Losses due to rise and fall times are called switching losses. A diagram of the output, showing switching losses,
is shown in Figure 9.
1
f
tSWon
SW
tSWoff
+
=
tSW
Figure 9. Output Switching Losses
Rise and fall times are greater than zero for several reasons. One is that the output transistors cannot switch
instantaneously because (assuming a MOSFET) the channel from drain to source requires a specific period
of time to form. Another is that transistor gate-source capacitance and parasitic resistance in traces form RC
time constants that also increase rise and fall times.
Switching losses are constant at all output power levels, which means that switching losses can be ignored at
high power levels in most cases. At low power levels, however, switching losses must be taken into account
when calculating efficiency. Switching losses are dominated by conduction losses at the high output powers,
but should be considered at low powers. The switching losses are automatically taken into account if you
consider the quiescent current with the output filter and load.
class-D effect on power supply
Efficiency calculations are an important factor for proper power supply design in amplifier systems. Table 2
shows Class-D efficiency at a range of output power levels (per channel) with a 1-kHz sine wave input. The
maximum power supply draw from a stereo 10-W per channel audio system with 4-Ω loads and a 12-V supply
is almost 26 W. A similar linear amplifier such as the TPA032D02 has a maximum draw of greater than 50 W
under the same circumstances.
Table 2. Efficiency vs Output Power in 12-V 4-Ω H-Bridge Systems
Output Power (W)
Efficiency (%)
Peak Voltage (V)
Internal Dissipation (W)
0.5
41.7
2
0.7
2
66.7
4
1.0
5
75.1
6.32
1.66
8
78
77.9
8
8.94†
2.26
10
2.84
† High peak voltages cause the THD to increase
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TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
APPLICATION INFORMATION
class-D effect on power supply (continued)
There is a minor power supply savings with a class-D amplifier versus a linear amplifier when amplifying sine
waves. The difference is much larger when the amplifier is used strictly for music. This is because music has
much lower RMS output power levels, given the same peak output power (see Figure 10); and although linear
devices are relatively efficient at high RMS output levels, they are very inefficient at mid-to-low RMS power
levels. The standard method of comparing the peak power to RMS power for a given signal is crest factor, whose
equation is shown below. The lower RMS power for a set peak power results in a higher crest factor
Crest Factor
+ 10 log PP
PK
rms
Power
PPK
PRMS
Time
Figure 10. Audio Signal Showing Peak and RMS Power
18
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TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
APPLICATION INFORMATION
crest factor and thermal considerations
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 TPA032D02 data sheet, one can see that when the
TPA032D02 is operating from a 12-V supply into a 4-Ω speaker that 20-W peaks are available. Converting watts
to dB:
P dB
+ 10 Log
ǒǓ
PW
P ref
+ 10Log
ǒ Ǔ+
20
1
6 dB
(17)
Subtracting the crest factor restriction to obtain the average listening level without distortion yields:
* 18 dB + * 12 dB (15 dB crest factor)
6.0 dB * 15 dB + * 9 dB (15 dB crest factor)
6.0 dB * 12 dB + * 6 dB (12 dB crest factor)
6.0 dB * 9 dB + * 3 dB (9 dB crest factor)
6.0 dB * 6 dB + * 0 dB (6 dB crest factor)
6.0 dB * 3 dB + 3 dB (3 dB crest factor)
6.0 dB
Converting dB back into watts:
PW
+ 10PdBń10 Pref
+ 315 mW (18 dB crest factor)
+ 630 mW (15 dB crest factor)
+ 1.25 W (12 dB crest factor)
+ 2.5 W (9 dB crest factor)
+ 5 W (6 dB crest factor)
+ 10 W (3 dB crest factor)
(18)
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 10 W of continuous power output with a 3 dB
crest factor, against 12 dB and 15 dB applications drastically affects maximum ambient temperature ratings for
the system. Using the power dissipation curves for a 12-V, 4-Ω system, the internal dissipation in the
TPA032D02 and maximum ambient temperatures are shown in Table 3.
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TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
APPLICATION INFORMATION
crest factor and thermal considerations (continued)
Table 3. TPA032D02 Power Rating, 12-V, 4-Ω, Stereo
PEAK OUTPUT POWER
(W)
AVERAGE OUTPUT POWER
POWER DISSIPATION
(W/Channel)
MAXIMUM AMBIENT
TEMPERATURE
20
10 W (3 dB)
2.84
23°C
20
5 W (6 dB)
1.66
75°C
20
2.5 W (9 dB)
1.12
100°C
20
1.25 W (12 dB)
0.87
111°C
20
630 mW (15 dB)
0.7
118°C
20
315 mW (18 dB)
0.6
123°C
The maximum ambient temperature depends on the heatsinking ability of the PCB system. Using the 0 CFM
data from the dissipation rating table, the derating factor for the DCA package with 6.9 in2 of copper area on
a multilayer PCB is 44.8 mW/°C. Converting this to ΘJA:
Θ JA
1
+ Derating
1
+ 0.0448
+ 22.3°CńW
(19)
To calculate maximum ambient temperatures, first consider that the numbers from the dissipation graphs are
per channel so the dissipated heat needs to be doubled for two channel operation. Given ΘJA, the maximum
allowable junction temperature, and the total internal dissipation, the maximum ambient temperature can be
calculated with the following equation. The maximum recommended junction temperature for the TPA032D02
is 150 °C. The internal dissipation figures are taken from the Efficiency vs Output Power graphs.
T A Max
+ TJ Max * ΘJA PD
+ 150 * 22.3 (0.7 2) + 118°C (15 dB crest factor)
+ 150 * 22.3 (2.84 2) + 23°C (3dB crest factor)
(20)
NOTE:
Internal dissipation of 1.4 W is estimated for a 10-W system with a 15 dB crest factor per channel.
The TPA032D02 is designed with thermal protection that turns the device off when the junction temperature
surpasses 150°C to prevent damage to the IC. Table 3 was calculated for maximum listening volume without
distortion. When the output level is reduced the numbers in the table change significantly. Also, using 8-Ω
speakers dramatically increases the thermal performance by increasing amplifier efficiency.
20
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TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
THERMAL INFORMATION
The thermally enhanced DCA package is based on the 56-pin TSSOP, but includes a thermal pad (see Figure 11)
to provide an effective thermal contact between the IC and the PWB.
Traditionally, surface-mount and power have been mutually exclusive terms. A variety of scaled-down TO-220-type
packages have leads formed as gull wings to make them applicable for surface-mount applications. These packages,
however, have only two shortcomings: they do not address the very low profile requirements (< 2 mm) of many of
today’s advanced systems, and they do not offer a terminal-count high enough to accommodate increasing
integration. On the other hand, traditional low-power surface-mount packages require power-dissipation derating that
severely limits the usable range of many high-performance analog circuits.
The PowerPAD package (thermally enhanced TSSOP) combines fine-pitch surface-mount technology with thermal
performance comparable to much larger power packages.
The PowerPAD package is designed to optimize the heat transfer to the PWB. Because of the very small size and
limited mass of a TSSOP package, thermal enhancement is achieved by improving the thermal conduction paths that
remove heat from the component. The thermal pad is formed using a patented lead-frame design and manufacturing
technique to provide a direct connection to the heat-generating IC. When this pad is soldered or otherwise thermally
coupled to an external heat dissipator, high power dissipation in the ultra-thin, fine-pitch, surface-mount package can
be reliably achieved.
Thermal
Pad
DIE
Side View (a)
DIE
End View (b)
Bottom View (c)
Figure 11. Views of Thermally Enhanced DCA Package
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TPA032D02
10-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS243A – DECEMBER 1999 – REVISED MARCH 2000
MECHANICAL DATA
DCA (R-PDSO-G**)
PowerPAD PLASTIC SMALL-OUTLINE PACKAGE
48 PINS SHOWN
0,27
0,17
0,50
48
0,08 M
25
Thermal Pad
(See Note D)
6,20
6,00
8,30
7,90
0,15 NOM
Gage Plane
1
24
0,25
A
0°– 8°
0,75
0,50
Seating Plane
0,15
0,05
1,20 MAX
PINS **
0,10
48
56
64
A MAX
12,60
14,10
17,10
A MIN
12,40
13,90
16,90
DIM
4073259/A 01/98
NOTES: A.
B.
C.
D.
All linear dimensions are in millimeters.
This drawing is subject to change without notice.
Body dimensions do not include mold flash or protrusion not to exceed 0,15.
The package thermal performance may be enhanced by bonding the thermal pad to an external thermal plane.
This pad is electrically and thermally connected to the backside of the die and possibly selected leads.
E. Falls within JEDEC MO-153
PowerPAD is a trademark of Texas Instruments.
22
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IMPORTANT NOTICE
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any product or service without notice, and advise customers to obtain the latest version of relevant information
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subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those
pertaining to warranty, patent infringement, and limitation of liability.
TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in
accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent
TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily
performed, except those mandated by government requirements.
Customers are responsible for their applications using TI components.
In order to minimize risks associated with the customer’s applications, adequate design and operating
safeguards must be provided by the customer to minimize inherent or procedural hazards.
TI assumes no liability for applications assistance or customer product design. TI does not warrant or represent
that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other
intellectual property right of TI covering or relating to any combination, machine, or process in which such
semiconductor products or services might be or are used. TI’s publication of information regarding any third
party’s products or services does not constitute TI’s approval, warranty or endorsement thereof.
Copyright  2000, Texas Instruments Incorporated
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