Datasheet TPA032D01DCAR, TPA032D01DCA Datasheet (Texas Instruments)

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TPA032D01

10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – DECEMBER 1999 – REVISED MARCH 2000

Extremely Efficient Class-D Mono 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 PowerP AD 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.

SHUTDOWN

MUTE AGND

INN INP

COMP

AGND

OUTP OUTP PGND PGND OUTN OUTN

VCCREG

NC NC

AGND

VCP

CP1

NC – No internal connection

DCA PACKAGE

(TOP VIEW)

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 PV

NC NC PGND PGND NC NC PV

NC NC V2P5 PV

PGND NC CP2

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 TP A032D01 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 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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T l

R l

7 11

POST OFFICE BOX 655303 DALLAS, TEXAS 75265

•

INP INN

COMP

COSC

+ _

10 kΩ 10 kΩ

1.5 V

RAMP

GENERATOR

TPA032D01

10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – DECEMBER 1999 – REVISED MARCH 2000

schematic

FAULT0

OUTN

OUTP

VCP PV

+ _

GATE

DRIVE

GATE

DRIVE

THERMAL

DETECT

VCP-UVLO

DETECT

CONTROL and

5-V

REGULATOR

and BIASES

FAULT1

STARTUP

LOGIC

SHUTDOWN

MUTE

VCCREG

V2P5

emp ate

e ease

ate:

– –

AGND

PGND

NOTE A: VDD and PVDD are externally connected. AGND and PGND are externally connected.

DOUBLER

CHARGE PUMP

VCP

CP2

CP1

DESCRIPTION

TPA032D01

10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – DECEMBER 1999 – REVISED MARCH 2000

Terminal Functions

TERMINAL

NAME NO.

AGND 3, 7, 20,

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 INP 5 Class-D positive input OUTN 14, 15 Class-D amplifier negative output of H-bridge OUTP 10, 11 Class-D amplifier positive output of H-bridge PV

MUTE

NC 18, 19, 23,

PGND 12, 13 Power ground for H–bridge only PGND 27 Power ground for charge pump only PGND 36, 37 Power ground for right-channel H-bridge only PV

43, 44, 45,

46, 47

9, 16 Class-D amplifier power supply

26, 30, 31, 34, 35, 38,

21, 28, 33,40VDD supply for charge-pump and gate drive circuitry

Analog ground for headphone and Class-D analog circuitry

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. Not connected

SHUTDOWN

V2P5 29 2.5V internal reference bypass. This terminal requires a capacitor to ground. V

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. V

32 5V supply to circuitry. This terminal is typically connected to VCCREG.

8 VDD bias supply for analog circuitry. This terminal needs to be well filtered to prevent degrading the device

Active-low TTL logic-level shutdown input signal. When SHUTDOWN is held low, the device goes into shutdown mode. When SHUTDOWN

performance.

is held high, the device operates normally.

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

0 0 Thermal fault. All the low-side transistors are turned on, shorting the load to ground. Once the junction temperature

ground. Once the charge pump voltage is restored, normal operation resumes, but FAUL T1 is still active. This is not a latched fault, however. FAULT1 is cleared by cycling MUTE

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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TPA032D01 10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – DECEMBER 1999 – REVISED MARCH 2000

AVAILABLE OPTIONS

–40°C to 125°C TPA032D01DCA

†

The DCA package is available in left-ended tape and reel. T o order a taped and reeled part, add the suffix R to the part number (e.g., TPA032D01DCAR).

PACKAGED DEVICES

†

TSSOP

(DCA)

absolute maximum ratings over operating free-air temperature range, TC = 25°C (unless otherwise noted)

†

NOTE 1: Pulse duration = 10 ms, duty cycle v 2%

†

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, I

(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, I Continuous V

REG output current, IO (VCCREG) 150 mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(see Note 1) 7 A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

max

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, T

–65°C to 260°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

stg

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.

DISSIPATION RATING TABLE

PACKAGE

DCA 5.6 W 44.8 mW/°C 3.6 W 2.9 W

‡

Please see the Texas Instruments document,

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

Recommended Board for PowerPAD

TA ≤ 25°C

POWER RATING

‡

DERATING FACTOR

ABOVE TA = 25°C

PowerPAD Thermally Enhanced Package Application

on page 33 of the before mentioned document.

TA = 70°C

POWER RATING

TA = 85°C

POWER RATING

Texas Instruments

recommended operating conditions

MIN NOM MAX UNIT

Supply voltage, VDD, PVDD, LPVDD, RPV Logic supply voltage, V High-level input voltage, VIH (MUTE, SHUTDOWN) 2 VDD + 0.3 V V Low-level input voltage, VIL (MUTE, SHUTDOWN) –0.3 0.8 V Audio inputs, LINN, LINP, RINN, RINP, differential input voltage 1 V PWM frequency 100 250 500 kHZ

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8 14 V

4.5 5.5 V

RMS

TPA032D01

10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – DECEMBER 1999 – REVISED MARCH 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 MIN TYP MAX UNIT

Power supply rejection ratio VDD = PVDD = xPVDD = 11 V to 13 V –40 dB

DD(Mute)

DD(S/D)

|IIH| High-level input current (MUTE, MODE,

|IIL| Low-level input current (MUTE, MODE,

DS(on)

operating characteristics, Class-D amplifier, VDD = PVDD = 12 V, RL = 4 Ω, TA = 25°C, See Figure 1 (unless otherwise noted)

Supply current No output filter connected 25 35 mA Supply current, mute mode MUTE = 0 V 10 18 mA Supply current, shutdown mode SHUTDOWN = 0 V 20 30 µA

SHUTDOWN

SHUTDOWN Static drain-to-source on-state resistance

(high-side + low-side FETs) Matching, high-side to high-side, low-side to

low-side, same channel

)

VIH = 5.25 V 10 µA

VIL = –0.3 V 10 µA

IDD = 0.5 A 720 800 mΩ

95% 98%

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

Output power

Efficiency

Gain 25 dB

Noise floor –60 dB Dynamic range 80 dB Crosstalk f = 1 kHz –50 dB Frequency response bandwidth, post output filter, –3 dB 20 20000 Hz

Maximum output power bandwidth 20 kHz

Input impedance 10 kΩ

NOTE 2: Output power is thermally limited, TA = 23°C

f = 1 kHz, THD = 0.5% Device soldered on PCB, See Note 2

PO = 10 W, f = 1 kHz

10 W

77%

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TPA032D01 10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – DECEMBER 1999 – REVISED MARCH 2000

operating characteristics, Class-D amplifier, VDD = PVDD = 12 V, RL = 8 Ω,

= 25°C, See Figure 2 (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

THD = 0.5%

Output power,

Efficiency

Gain 25 dB

Noise floor –60 dB Dynamic range 80 dB Crosstalk f = 1 kHz –50 dB Frequency response bandwidth, post output filter, –3 dB 20 20000 Hz

Maximum output power bandwidth 20 kHz

Input impedance 10 kΩ

NOTE 2: Output power is thermally limited, TA = 85°C

operating characteristics, VCC 5-V regulator, TA = 25°C (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

†

Pulse width must be limited to prevent exceeding the maximum operating virtual junction temperature of 150°C.

Output voltage

Short-circuit output current VDD = PVDD = LPVDD = RPVDD = 8 V to 14 V

VDD = PVDD = LPVDD = RPVDD = 8 V to 14 V, IO = 0 to 90 mA

Device soldered on PCB, See Note 2

PO = 7.5 W, f = 1 kHz

7.5 W

85%

4.5 5.5 V

†

90 mA

thermal shutdown

Thermal shutdown temperature 165 °C Thermal shutdown hysteresis 30 °C

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

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TPA032D01

10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – DECEMBER 1999 – REVISED MARCH 2000

PARAMETER MEASUREMENT INFORMATION

Balanced

Differential

Input Signal

1000 pF

7,20,43, 44, 45, 46,47

VCCREG VCCREG

9,16

12 V

1 µF

12,13,27,36,37

1 2

SHUTDOWN MUTE

INP

INN

COMP

COSC

AGND PGND

FAULT0 FAULT1

OUTN

OUTP

V2P5

VCCREG

42 41

14,15

10,11

15 µH

0.22 µF

15 µH

12 V

1 µF

0.1 µF

1 µF

4 Ω

12 V

VCCREG

500 kΩ

100 kΩ

21, 28, 33, 34

Figure 1. 12-V, 4-Ω Test Circuit

CP1

CP2

VCP

47 nF

25 22

0.1 µF

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TPA032D01 10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – DECEMBER 1999 – REVISED MARCH 2000

PARAMETER MEASUREMENT INFORMATION

Balanced

Differential

Input Signal

1000 pF

7,20,43, 44, 45, 46,47

VCCREG VCCREG

9,16

12 V

1 µF

12,13,27,36,37

1 2

SHUTDOWN MUTE

INP

INN

COMP

COSC

AGND PGND

FAULT0 FAULT1

OUTN

OUTP

V2P5

VCCREG

42 41

14,15

10,11

0.1 µF

12 V

30 µH

1 µF

0.1 µF

1 µF

8 Ω

12 V

VCCREG

500 kΩ

100 kΩ

21, 28, 33, 34

Figure 2. 12-V, 8-Ω Test Circuit

CP1

CP2

VCP

47 nF

25 22

0.1 µF

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TPA032D01

10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – DECEMBER 1999 – REVISED MARCH 2000

APPLICATION INFORMATION

VCCREG

12 V

10 µF

Class-D Balanced

Differential Input

1000 pF

12 V

1 µF

500 kΩ

VCCREG

To System

Control

Signal

1000 pF

12,13,27,36,37

100 kΩ

9,16

1 µF1 µF

1 µF

7,20,46,47

21, 28

SHUTDOWN

MUTE

INP

INN

COMP

COSC

AGND PGND

FAULT0 FAULT1

OUTN

OUTP

V2P5

VCCREG

CP1

CP2

VCP

100 kΩ

42 41

14,15

10,11

29 8

1 µF

25 22

15 µH

0.22 µF

15 µH

12 V

47 nF

0.1 µF

100 kΩ

To System Control

1 µF

4 Ω

0.1 µF

NOTE A: = power ground and = analog ground

Figure 3. TPA032D01 Typical Configuration Application Circuit

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TPA032D01 10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – DECEMBER 1999 – REVISED MARCH 2000

APPLICATION INFORMATION

input capacitor, C

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

c(highpass)

2pZIC

ZI is nominally 10 kΩ

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.

2pZIf

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.

(8)

(9)

differential input

The TP A032D01 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 TP A032D01. If this is not feasible, it is still necessary to locally ground the unused input terminal through a dc-blocking capacitor.

power supply decoupling, C

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 V 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 TP A032D01 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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TPA032D01

10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – DECEMBER 1999 – REVISED MARCH 2000

APPLICATION INFORMATION

mute and shutdown modes

The TP A032D01 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 I

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.

to 10 mA.

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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TPA032D01 10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – 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 P

Efficiency+h

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.

is the supply power.

SUP

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 (r

) and the switching times of the output transistors are zero.

DS(on)

the ideal class-D amplifier

T o illustrate how the output transistors of a class-D amplifier operate, a half-bridge application is examined first (see Figure 4).

OUT

–

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 V

(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 V

, which makes V

equal to the supply voltage multiplied by the duty cycle.

OUT

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TPA032D01

10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – 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

Supply Current

Current

Voltage

M1 on M2 off

M1 off M2 on

M1 on M2 off

Time

Figure 5. Class-D Currents

M1 on M2 off

Time

Figure 6. Class-D Voltages

OUT

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TPA032D01 10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – 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 LINEAR

L(rms)

AverageǒI

PL+

SUP

Efficiency+h

VDD

AverageǒI

L(rms)

SUP

L(rms)

PL+

AverageǒI

SUP

Efficiency+h

Efficiency+h+VDD

Efficiency+h+1 Efficiency

L(rms)

VDD

+h+

AverageǒI

SUP

P L

V 2R

V R

VDDV

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.

OUT

–

Figure 7. H-Bridge Class-D Output Stage

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TPA032D01

10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – 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 r

The loss due to a nonzero r

is called conduction loss, and is the power lost in the output transistors at

DS(on)

nonswitching times, when the transistor is on (saturated). Any r 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.

, and rise and fall times that are greater than zero.

DS(on)

above 0 Ω causes conduction loss.

DS(on)

VDD = 12 V

DS(on)

DS(off)

0.36 Ω

4 Ω

5 MΩ

Figure 8. Output Transistor Simplification for Conduction Loss Calculation

The power supplied, P

, is determined to be the power output to the load plus the power lost in the transistors,

SUP

assuming that there are always two transistors on.

Efficiency+h

SUP

I22r

DS(on)

I2R

DS(on)

)

I2R

Efficiency+h+95%ǒat all output levels r

0.36 Ω

5 MΩ

DS(on)

DS(off)

DS(on)

0.1 Ω,RL+

4 Ω

Efficiency+h+85%ǒat all output levels r

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

DS(on)

0.36 Ω,RL+

4 Ω

TPA032D01 10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – 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.

SWon

SWoff

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 8 1.13

10 77.9 8.94

†

High peak voltages cause the THD to increase

†

1.42

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TPA032D01

10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – 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

rms

Power

Crest Factor

10 log

RMS

Time

Figure 10. Audio Signal Showing Peak and RMS Power

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TPA032D01 10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – 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 TPA032D01 data sheet, one can see that when the TP A032D01 is operating from a 12-V supply into a 4-Ω speaker that 20-W peaks are available. Converting watts to dB:

PdB+

Subtracting the crest factor restriction to obtain the average listening level without distortion yields:

6.0 dB*18 dB

6.0 dB*15 dB

6.0 dB*12 dB

6.0 dB*9dB

6.0 dB*6dB

6.0 dB*3dB+3dB(3 dB crest factor

Converting dB back into watts:

PW+

10Log

PdBń10

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)

ref

+* +*

+* +* +*

10Log

12 dB(15 dB crest factor 9dB(15 dB crest factor

6dB(12 dB crest factor 3dB(9 dB crest factor 0dB(6 dB crest factor

ref

6dB

) ) )

) )

)

(17)

(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 af fects 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.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

AVERAGE OUTPUT POWER

10-W MONO CLASS-D AUDIO POWER AMPLIFIER

APPLICATION INFORMATION

crest factor and thermal considerations (continued)

Table 3. TPA032D01 Power Rating, 12-V, 4-Ω, Stereo

TPA032D01

SLOS282A – DECEMBER 1999 – REVISED MARCH 2000

PEAK OUTPUT POWER

(W)

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

POWER DISSIPATION MAXIMUM AMBIENT

(W/Channel) TEMPERATURE

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:

Derating

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 TP A032D01 is 150 °C. The internal dissipation figures are taken from the Efficiency vs Output Power graphs.

TAMax

TJMax

150*22.3(0.35)+

150*22.3(1.42)+

JAPD

125°C(15 dB crest factor 118°C(3dB crest factor

)

(20)

)

(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.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TPA032D01 10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – 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 PowerP AD 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.

DIE

Side View (a)

DIE

End View (b)

Thermal

Pad

Bottom View (c)

Figure 11. Views of Thermally Enhanced DCA Package

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TPA032D01

10-W MONO CLASS-D AUDIO POWER AMPLIFIER

SLOS282A – DECEMBER 1999 – REVISED MARCH 2000

MECHANICAL DATA

DCA (R-PDSO-G**) PowerPAD PLASTIC SMALL-OUTLINE PACKAGE

48 PINS SHOWN

0,50

1,20 MAX

0,27 0,17

0,15 0,05

0,08

6,20

8,30

6,00

7,90

Seating Plane

0,10

Thermal Pad (See Note D)

0,15 NOM

Gage Plane

0°–8°

0,25

0,75 0,50

DIM

A MAX

A MIN

NOTES: A. All linear dimensions are in millimeters.

B. This drawing is subject to change without notice. C. Body dimensions do not include mold flash or protrusion not to exceed 0,15. D. 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.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

PINS **

12,60

12,40

14,10

17,10

16,9013,90

4073259/A 01/98

IMPORTANT NOTICE

T exas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold 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.

Datasheet TPA032D01DCAR, TPA032D01DCA Datasheet (Texas Instruments)

Specifications and Main Features

Frequently Asked Questions

User Manual