TI TPA032D01DCAR

SLOS282B − DECEMBER 1999 − REVISED JUNE 2000
D Extremely Efficient Class-D Mono
D
D
D
D
D
D
D
Operation
Drives Mono Speaker
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 TPA032D01 is a monolithic power IC mono
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 TPA032D01 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
INN
INP
COMP
AGND
VDD
PVDD
OUTP
OUTP
PGND
PGND
OUTN
OUTN
PVDD
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
AGND
AGND
AGND
FAULT0
FAULT1
PVDD
NC
NC
PGND
PGND
NC
NC
PVDD
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 TPA032D01 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 TPA032D01 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.
Copyright  2000, Texas Instruments Incorporated
!" #!$% &"'
&! #" #" (" " ") !"
&& *+' &! #", &" ""%+ %!&"
", %% #""'
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• DALLAS, TEXAS 75265
1
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PGND
RAMP
GENERATOR
+
_
PVDD
GATE
DRIVE
VCP
GATE
DRIVE
PVDD
OUTN
OUTP
NOTE A: VDD and PVDD are externally connected. AGND and PGND are externally connected.
AGND
COSC
VDD
1.5 V
10 kΩ
+
_
PVDD
VCP-UVLO
DETECT
CONTROL and
STARTUP
LOGIC
5-V
REGULATOR
and BIASES
PVDD
DOUBLER
CHARGE PUMP
THERMAL
DETECT
FAULT0
VDD
10 kΩ
PVDD
PVDD
FAULT1
COMP
INN
INP
PVDD
VCP
VCC
V2P5
VCCREG
MUTE
SHUTDOWN
----
-
SLOS282B − DECEMBER 1999 − REVISED JUNE 2000
schematic
CP1
CP2
VCP
PVDD
SLOS282B − DECEMBER 1999 − REVISED JUNE 2000
Terminal Functions
TERMINAL
NAME
DESCRIPTION
NO.
AGND
3, 7, 20,
43, 44, 45,
46, 47
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.
COMP
6
Compensation capacitor terminal for Class-D amplifier
INN
4
Class-D negative input
5
Class-D positive input
INP
Analog ground for headphone and Class-D analog circuitry
OUTN
14, 15
Class-D amplifier negative output of H-bridge
OUTP
10, 11
Class-D amplifier positive output of H-bridge
PVDD
9, 16
Class-D amplifier power supply
MUTE
2
NC
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.
18, 19, 23,
26, 30, 31,
34, 35, 38,
39
PGND
12, 13
PGND
27
PGND
36, 37
PVDD
21, 28, 33,
40
Not connected
Power ground for H-bridge only
Power ground for charge pump only
Power ground for right-channel H-bridge only
VDD supply for charge-pump and gate drive circuitry
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.
V2P5
29
2.5V internal reference bypass. This terminal requires a capacitor to ground.
VCC
VCCREG
32
5V supply to circuitry. This terminal is typically connected to VCCREG.
17
5-V regulator output. This terminal requires a 1-µF capacitor to ground for stability reasons.
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.
Class-D amplifier faults
Table 1. Class-D Amplifier Fault Table
FAULT 0
FAULT 1
DESCRIPTION
1
1
No fault. The device is operating normally.
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.
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SLOS282B − DECEMBER 1999 − REVISED JUNE 2000
AVAILABLE OPTIONS
PACKAGED DEVICES
TSSOP†
(DCA)
TA
−40°C to 125°C
TPA032D01DCA
† 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.,
TPA032D01DCAR).
absolute maximum ratings over operating free-air temperature range, TC = 25°C (unless otherwise
noted)†
Supply voltage, (VDD, PVDD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 v 2%
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
NOM
8
Logic supply voltage, VCC
High-level input voltage, VIH (MUTE, SHUTDOWN)
Low-level input voltage, VIL (MUTE, SHUTDOWN)
V
4.5
5.5
V
2
VDD + 0.3 V
0.8
V
−0.3
1
PWM frequency
100
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UNIT
14
Audio inputs, LINN, LINP, RINN, RINP, differential input voltage
4
MAX
250
500
V
VRMS
kHZ
SLOS282B − DECEMBER 1999 − REVISED JUNE 2000
electrical characteristics Class-D amplifier, VDD = PVDD = 12 V, RL = 4 Ω to 8 Ω, TA = 25°C,
See Figure 1 (unless otherwise noted)
PARAMETER
TEST CONDITIONS
IDD
IDD(Mute)
Power supply rejection ratio
Supply current
VDD = PVDD = xPVDD = 11 V to 13 V
No output filter connected
Supply current, mute mode
IDD(S/D)
Supply current, shutdown mode
|IIH|
High-level input current (MUTE, MODE,
SHUTDOWN)
|IIL|
MIN
TYP
MAX
−40
UNIT
dB
25
35
mA
MUTE = 0 V
10
18
mA
SHUTDOWN = 0 V
20
30
µA
VIH = 5.25 V
10
µA
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 = 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%
Device soldered on PCB,
See Note 2
Efficiency
PO = 10 W,
MIN
f = 1 kHz
Dynamic range
BOM
f = 1 kHz
25
dB
dB
80
dB
−50
Maximum output power bandwidth
POST OFFICE BOX 655303
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• DALLAS, TEXAS 75265
W
−60
20
ZI
Input impedance
NOTE 2: Output power is thermally limited, TA = 23°C
UNIT
77%
Noise floor
Frequency response bandwidth, post output filter, − 3 dB
MAX
10
Gain
Crosstalk
TYP
dB
20 000
Hz
20
kHz
kΩ
5
SLOS282B − DECEMBER 1999 − REVISED JUNE 2000
operating characteristics, Class-D amplifier,
TA = 25°C, See Figure 2 (unless otherwise noted)
PARAMETER
PO
AV
VDD
=
PVDD
=
TEST CONDITIONS
Output power,
THD = 0.5%
Device soldered on PCB,
See Note 2
Efficiency
PO = 7.5 W,
12
V,
MIN
RL
TYP
f = 1 kHz
UNIT
W
25
dB
−60
dB
80
dB
Dynamic range
BOM
MAX
Ω,
85%
Noise floor
f = 1 kHz
Frequency response bandwidth, post output filter, − 3 dB
8
7.5
Gain
Crosstalk
=
−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
Output voltage
TEST CONDITIONS
VDD = PVDD = LPVDD = RPVDD = 8 V to 14 V,
IO = 0 to 90 mA
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
6
POST OFFICE BOX 655303
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MIN
TYP
MAX
UNIT
165
°C
30
°C
SLOS282B − DECEMBER 1999 − REVISED JUNE 2000
PARAMETER MEASUREMENT INFORMATION
FAULT0
FAULT1
1
VCCREG
VCCREG
2
SHUTDOWN
OUTN
MUTE
42
41
14,15
15 µH
0.22 µF
12 V
9,16
1 µF
PVDD
OUTP
1 µF
5
Balanced
Differential
Input Signal
4
1 µF
10,11
15 µH
INP
INN
V2P5
6
4Ω
0.22 µF
29
COMP
1 µF
1000 pF
48
COSC
VDD
8
12 V
1000 pF
7,20,43, 44, 45, 46,47
12,13,27,36,37
VCCREG
AGND
17
PGND
VCC
0.1 µF
21, 28, 33, 40
PVDD
12 V
CP1
24
47 nF
500 kΩ
CP2
To
VCCREG
32
VCP
VCC
25
22
0.1 µF
100 kΩ
Figure 1. 12-V, 4-Ω Test Circuit
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7
SLOS282B − DECEMBER 1999 − REVISED JUNE 2000
PARAMETER MEASUREMENT INFORMATION
FAULT0
FAULT1
1
VCCREG
VCCREG
2
SHUTDOWN
OUTN
MUTE
42
41
14,15
30 µH
0.1 µF
12 V
9,16
1 µF
PVDD
0.1 µF
OUTP
1 µF
5
Balanced
Differential
Input Signal
4
1 µF
30 µH
INP
INN
V2P5
6
10,11
29
COMP
1 µF
1000 pF
48
COSC
VDD
8
12 V
1000 pF
7,20,43, 44, 45, 46,47
12,13,27,36,37
VCCREG
AGND
17
PGND
VCC
0.1 µF
21, 28, 33, 40
PVDD
12 V
CP1
24
47 nF
500 kΩ
CP2
32
To
VCCREG
VCP
VCC
25
22
0.1 µF
100 kΩ
Figure 2. 12-V, 8-Ω Test Circuit
8
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• DALLAS, TEXAS 75265
8Ω
SLOS282B − DECEMBER 1999 − REVISED JUNE 2000
APPLICATION INFORMATION
VCCREG
1
To System
Control
SHUTDOWN
2
100 kΩ
MUTE
FAULT0
12 V
10 µF
1 µF
9,16
1 µF
FAULT1
PVDD
1 µF
OUTN
5
Class-D Balanced
Differential Input
Signal
4
To System
Control
41
14,15
INP
1 µF
INN
4Ω
0.22 µF
6
OUTP
COMP
1000 pF
48
V2P5
COSC
VDD
1000 pF
7,20,46,47
12,13,27,36,37
21, 28,33,40
1 µF
VCCREG
AGND
PGND
CP1
PVDD
10,11
29
15 µH
8
12 V
1 µF
1 µF
17
VCC
24
47 nF
CP2
32
VDD
15 µH
0.22 µF
1 µF
12 V
100 kΩ
42
VCP
VCC
25
22
0.1 µF
500 kΩ
To
VCCREG
100 kΩ
0.1 µF
NOTE A:
= power ground and
= analog ground
Figure 3. TPA032D01 Typical Configuration Application Circuit
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9
SLOS282B − DECEMBER 1999 − REVISED JUNE 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 TPA032D01’s input resistance forms a
high-pass filter with the corner frequency determined in equation 8.
−3 dB
f
c(highpass)
+
1
2pZ C
I I
(8)
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 +
1
2p Z f c
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 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 TPA032D01 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 TPA032D01. 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 TPA032D01 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 TPA032D01 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.
10
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SLOS282B − DECEMBER 1999 − REVISED JUNE 2000
APPLICATION INFORMATION
mute and shutdown modes
The TPA032D01 employs both a mute and a shutdown mode of operation designed to reduce supply current,
IDD, to the absolute minimum level during periods of nonuse 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.
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11
SLOS282B − DECEMBER 1999 − REVISED JUNE 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 +
PL
P 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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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
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SLOS282B − DECEMBER 1999 − REVISED JUNE 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
LINEAR
V
V L(rms) + P
Ǹ2
V
V L(rms) + P
Ǹ2
I L(rms)
Average ǒI DDǓ +
PL + VL
PL +
V DD
V DD
V L(rms)2
RL
+
V P2
2 RL
VP
2
Average ǒI DDǓ + p
IL
P SUP + V DD
P SUP +
V L(rms)
AverageǒI DDǓ
I L(rms)
Efficiency + h +
V DD
Efficiency + h +
V
V
AverageǒI DDǓ + DD P
RL
P SUP + V DD
V L(rms)
PL
RL
PL
P SUP
V P2
2R L
Efficiency + h + V DD
P SUP
V
2
p
V
Efficiency + h + p
4
Efficiency + h + 1
2
p
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
M4
+ VOUT −
L
M2
L
RL
CL
CL
Figure 7. H-Bridge Class-D Output Stage
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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 +
Efficiency + h +
Efficiency + h +
PL
P SUP
I 2R L
I 2 2r DS(on) ) I 2R L
RL
2r DS(on) ) R L
ǒ
Ǔ
+ 85% ǒat all output levels r DS(on) + 0.36 Ω, R L + 4 ΩǓ
Efficiency + h + 95% at all output levels r DS(on) + 0.1 Ω, R L + 4 Ω
Efficiency + h
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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 TPA032D01 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
0.35
2
66.7
4
0.5
5
75.1
6.32
0.83
8
78
77.9
8
8.94†
1.13
10
† High peak voltages cause the THD to increase
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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
P PK
P rms
Power
PPK
PRMS
Time
Figure 10. Audio Signal Showing Peak and RMS Power
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APPLICATION INFORMATION
class-D EVM power supply decoupling data
The decoupling capacitance required will depend upon the application. Pads and through-holes have been
provided on the EVM for the addition of bulk capacitance (see the schematic). A plot showing the impact of
various levels of bulk capacitance on the voltage ripple on the power supply line is shown in Figure 11. This ripple
is maximum at higher frequency. The figure shows worst-case voltage ripple for a 20-kHz, 10-W output into a
4-Ω load. In all cases, two 10-µF and one 1-µF ceramic chip capacitors were decoupling the power supply signal
from the EVM. The 1-µF unit was placed immediately adjacent to the IC power pins, and the 10-µF units were
placed adjacent to each other a little farther out.
The upper trace shows the ripple when only these capacitors are used. The middle trace shows the impact of
an additional 330-µF aluminum electrolytic capacitor rated at 25 V, 90 mΩ, and for 755 mA at 100 kHz. In the
bottom trace, the 330-µF capacitor was replaced by a 390-µF aluminum electrolytic capacitor rated at 35 V, 65
mΩ, and for 1.2 A of 100 kHz ripple current.
The results indicate that for sensitive circuits where minimum voltage ripple is required, a larger bulk
capacitance with low ESR should be used. For systems that are contained and EMI is controlled, less
capacitance may be used. The difference in the level of distortion in the output signal was very small between
each level of decoupling, with the 20-µF bulk capacitance providing the least distortion. This is attributed to the
low ESR of the capacitor, which is only a few milliohms at the switching frequency of 250 kHz. The distortion
is made lower still by the parallel combination. Distortion of the output signal when only one 10-µF capacitor
is used is the same as for 20 µF. The difference is more noticeable on the power supply line, though the distortion
is increased only slightly more than with the 20-µF capacitor.
Vcc Ripple Voltage (2 V per division)
RIPPLE VOLTAGE
Time (10 µsec per division)
Figure 11. Power Supply Decoupling
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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 TPA032D01 data sheet, one can see that when the
TPA032D01 is operating from a 12-V supply into a 4-Ω speaker that 20-W peaks are available. Converting watts
to dB:
P dB + 10Log
ǒ Ǔ
PW
P ref
ǒ Ǔ
+ 10Log 20 + 6 dB
1
(17)
Subtracting the crest factor restriction to obtain the average listening level without distortion yields:
6.0 dB * 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)
Converting dB back into watts:
P W + 10 PdBń10
P ref
(18)
+ 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)
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
TPA032D01 and maximum ambient temperatures are shown in Table 3.
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APPLICATION INFORMATION
crest factor and thermal considerations (continued)
Table 3. TPA032D01 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
87°C
20
5 W (6 dB)
1.66
113°C
20
2.5 W (9 dB)
1.12
125°C
20
1.25 W (12 dB)
0.87
125°C
20
630 mW (15 dB)
0.7
125°C
20
315 mW (18 dB)
0.6
125°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
(19)
1
0.0448
+ 22.3°CńW
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 TPA032D01
is 150 °C. The internal dissipation figures are taken from the Efficiency vs Output Power graphs.
T A Max + T J Max * Θ JA P D
+ 150 * 22.3 (0.35) + 125°C (15 dB crest factor)
(20)
+ 150 * 22.3 (1.42) + 118°C (3dB crest factor)
(Maximum recommended case temperature is 125°C)
NOTE:
Internal dissipation of 0.7 W is estimated for a 10-W system with a 15 dB crest factor per channel.
The TPA032D01 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.
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THERMAL INFORMATION
The thermally enhanced DCA package is based on the 56-pin TSSOP, but includes a thermal pad (see Figure 12)
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 ultrathin, fine-pitch, surface-mount package can
be reliably achieved.
Thermal
Pad
DIE
Side View (a)
DIE
End View (b)
Bottom View (c)
Figure 12. Views of Thermally Enhanced DCA Package
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PACKAGE OPTION ADDENDUM
www.ti.com
6-Dec-2006
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
Lead/Ball Finish
MSL Peak Temp (3)
TPA032D01DCA
ACTIVE
HTSSOP
DCA
48
40
TBD
CU NIPDAU
Level-3-220C-168 HR
TPA032D01DCAR
ACTIVE
HTSSOP
DCA
48
2000
TBD
CU NIPDAU
Level-3-220C-168 HR
TPA032D01DCARG4
ACTIVE
HTSSOP
DCA
48
TBD
Call TI
Call TI
(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
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