Datasheet TPA701 Datasheet (TEXAS INSTRUMENTS)

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Page 1

TPA701

700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MA Y 2003

D Fully Specified for 3.3-V and 5-V Operation D Wide Power Supply Compatibility

2.5 V – 5.5 V

D Output Power for R

– 700 mW at V – 250 mW at V

= 8 Ω

= 5 V, BTL

= 3.3 V, BTL

SHUTDOWN

BYPASS

D OR DGN PACKAGE

(TOP VIEW)

1 2

IN+ IN–

3 4

8 7 6 5

GND V

VO+

–

D Ultralow Quiescent Current in Shutdown

Mode . . . 1.5 nA

D Thermal and Short-Circuit Protection D Surface-Mount Packaging

– SOIC – PowerPAD MSOP

description

The TP A701 is a bridge-tied load (BTL) audio power amplifier developed especially for low-voltage applications where internal speakers are required. Operating with a 3.3-V supply, the TPA701 can deliver 250-mW of continuous power into a BTL 8-Ω load at less than 0.6% THD+N throughout voice band frequencies. Although this device is characterized out to 20 kHz, its operation was optimized for narrower band applications such as wireless communications. The BTL configuration eliminates the need for external coupling capacitors on the output in most applications, which is particularly important for small battery-powered equipment. This device features a shutdown mode for power-sensitive applications with a supply current of 1.5 nA during shutdown. The TP A701 is available in an 8-pin SOIC surface-mount package and the surface-mount PowerPAD MSOP, which reduces board space by 50% and height by 40%.

Audio

Input

From System Control

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

IN –

3 IN+

24BYPASS

SHUTDOWN

VDD/2

–

Bias

Control

VO+

VO–8

GND

700 mW

PowerPAD is a trademark of Texas Instruments.

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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Page 2

TPA701 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

AVAILABLE OPTIONS

PACKAGED DEVICES

–40°C to 85°C TPA701D TPA701DGN ABA

†

In the SOIC package, the maximum RMS output power is thermally limited to 350 mW; 700 mW peaks can be driven, as long as the RMS value is less than 350 mW.

‡

The D and DGN packages are available taped and reeled. T o order a taped and reeled part, add the suffix R to the part number (e.g., TPA701DR).

SMALL OUTLINE

(D)

†

Terminal Functions

MSOP

(DGN)

‡

MSOP

SYMBOLIZATION

TERMINAL

NAME NO.

BYPASS 2 I GND 7 GND is the ground connection.

IN– 4 I IN– is the inverting input. IN– is typically used as the audio input terminal. IN+ 3 I IN+ is the noninverting input. IN+ is typically tied to the BYPASS terminal. SHUTDOWN 1 I SHUTDOWN places the entire device in shutdown mode when held high (IDD = 1.5 nA). V

VO+ 5 O VO+ is the positive BTL output. VO– 8 O VO– is the negative BTL output.

I/O

BYPASS is the tap to the voltage divider for internal mid-supply bias. This terminal should be connected to a 0.1-µF to 2.2-µF capacitor when used as an audio amplifier.

6 VDD is the supply voltage terminal.

DESCRIPTION

absolute maximum ratings over operating free-air temperature range (unless otherwise noted)

Supply voltage, V Input voltage, V

Continuous total power dissipation internally limited (see Dissipation Rating Table). . . . . . . . . . . . . . . . . . . . .

Operating free-air temperature range, T Operating junction temperature range, T Storage temperature range, T

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.

6 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

–0.3 V to VDD +0.3 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

–40°C to 85°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

–40°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

–65°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

stg

DISSIPATION RATING TABLE

PACKAGE

D 725 mW 5.8 mW/°C 464 mW 377 mW

DGN 2.14 W

Please see the Texas Instruments document, PowerP AD 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 T exas Instruments Recommended Board for PowerPAD on page 33 of the before mentioned document.

TA ≤ 25°C DERATING FACTOR TA = 70°C TA = 85°C

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17.1 mW/°C 1.37 W 1.11 W

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TPA701

ББББББББББББ

БББББББББ

ББББББББББББ

700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

recommended operating conditions

MIN MAX UNIT

Supply voltage, V High-level voltage, V

Low-level voltage, V Operating free-air temperature, T

SHUTDOWN SHUTDOWN

electrical characteristics at specified free-air temperature, VDD = 3.3 V , TA = 25°C (unless otherwise noted)

PARAMETER TEST CONDITIONS

|VOO| PSRR I

DD(SD)

|IIH| |IIL|

Output offset voltage (measured differentially) Power supply rejection ratio Supply current Supply current, shutdown mode (see Figure 4)

High-level input current Low-level input current

SHUTDOWN = 0 V, RL = 8 Ω, RF = 10 kΩ VDD = 3.2 V to 3.4 V SHUTDOWN = 0 V, RF = 10 kΩ SHUTDOWN = VDD, RF = 10 kΩ

SHUTDOWN, VDD = 3.3 V, VI = 3.3 V SHUTDOWN, VDD = 3.3 V, VI = 0 V

0.9 V

2.5 DD

–40

0.1 V

5.5

V V

°C

MIN TYP MAX UNIT

1.25

1.5

1000

2.5

µA

operating characteristics, VDD = 3.3 V, T

PARAMETER TEST CONDITIONS

THD + N

ÁÁ

Output power, see Note 1 T otal harmonic distortion plus noise

БББББББ

Maximum output power bandwidth Unity-gain bandwidth Supply ripple rejection ratio Noise output voltage

THD = 0.2%, AV = – 2 V/V,

ÁÁÁ

PO = 250 mW AV = – 2 V/V, Open loop, f = 1 kHz, AV = –1 V/V,

= 25°C, R

See Figure 9 f = 200 Hz to 4 kHz,

THD = 2%, See Figure 15 CB = 1 µF, CB = 0.1 µF,

= 8 Ω

ÁÁÁÁ

See Figure 7,

ÁÁÁ

See Figure 7

See Figure 2 See Figure 19

MIN TYP MAX UNIT

250

0.55%

ÁÁÁ

1.4

ÁÁÁ

kHz

MHz 79 17

µV(rms)

NOTE 1: Output power is measured at the output terminals of the device at f = 1 kHz.

electrical characteristics at specified free-air temperature, VDD = 5 V , TA = 25°C (unless otherwise noted)

|VOO| PSRR I

DD(SD)

|IIH| |IIL|

PARAMETER TEST CONDITIONS

Output offset voltage (measured differentially) Power supply rejection ratio Supply current Supply current, shutdown mode (see Figure 4)

High-level input current Low-level input current

SHUTDOWN = 0 V, RL = 8 Ω, RF = 10 kΩ VDD = 4.9 V to 5.1 V SHUTDOWN = 0 V, RF = 10 kΩ SHUTDOWN = VDD, RF = 10 kΩ

SHUTDOWN, VDD = 5.5 V, VI = V

SHUTDOWN, VDD = 5.5 V, VI = 0 V

MIN TYP MAX UNIT

1.25 5

1500

2.5

µA

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TPA701

700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

operating characteristics, VDD = 5 V, T

PARAMETER TEST CONDITIONS

THD + N

ÁÁ

†

The DGN package, properly mounted, can conduct 700 mW RMS power continuously. The D package, can only conduct 350 mW RMS power

Output power T otal harmonic distortion plus noise

ББББББББ

Maximum output power bandwidth Unity-gain bandwidth Supply ripple rejection ratio Noise output voltage

THD = 0.5%, AV = – 2 V/V,

PO = 700 mW AV = – 2 V/V, Open loop, f = 1 kHz, AV = – 1 V/V,

= 25°C, R

ÁÁÁ

= 8 Ω

See Figure 13 f = 200 Hz to 4 kHz,

ÁÁÁÁ

THD = 2%, See Figure 16 CB = 1 µF, CB = 0.1 µF,

See Figure 11,

ÁÁÁ

See Figure 11

See Figure 2 See Figure 20

MIN TYP MAX UNIT

†

700

0.5%

ÁÁÁ

1.4 80 17

ÁÁÁ

kHz

MHz

µV(rms)

continuously , with peaks to 700 mW.

PARAMETER MEASUREMENT INFORMATION

Audio

Input

IN –

3 IN+

VDD/2

VO+

–

24BYPASS

–

VO– 8

RL = 8

Ω

GND

SHUTDOWN

Bias

Control

Figure 1. BTL Mode Test Circuit

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Page 5

700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

TYPICAL CHARACTERISTICS

Table of Graphs

Supply ripple rejection ratio vs Frequency 2

THD+N Total harmonic distortion plus noise

Supply current vs Supply voltage 3, 4

Output power

Open loop gain and phase vs Frequency 15, 16 Closed loop gain and phase vs Frequency 17, 18 Output noise voltage vs Frequency 19, 20 Power dissipation vs Output power 21, 22

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

FIGURE

vs Supply voltage 5 vs Load resistance vs Frequency 7, 8, 11, 12 vs Output power

9, 10, 13, 14

TPA701

SUPPLY RIPPLE REJECTION RATIO

RL = 8 Ω

–10

CB = 1 µF BTL

–20

–30

–40 –50

–60 –70

Supply Ripple Rejection Ratio – dB

–80

–90

–100

20 100 1k

VDD = 3.3 V

FREQUENCY

VDD = 5 V

f – Frequency – Hz

Figure 2

10k 20k

SUPPLY CURRENT

SUPPLY VOLTAGE

1.8 SHUTDOWN = 0 V RF = 10 kΩ

1.6

1.4

1.2

– Supply Current – mA

0.8

0.6

2.5 3.5 4.5

VDD – Supply Voltage – V

Figure 3

5.5

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TPA701 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

TYPICAL CHARACTERISTICS

– Supply Current – nA I

SHUTDOWN = V

RF = 10 kΩ

7 6

5 4

3 2

1 0

SUPPLY CURRENT

SUPPLY VOLTAGE

3.52.5 4.5

VDD – Supply Voltage – V

435

Figure 4

800

700

1000

800

600

400

– Output Power – mW

200

5.5

OUTPUT POWER

LOAD RESISTANCE

THD+N = 1% f = 1 kHz BTL

OUTPUT POWER

SUPPLY VOLTAGE

THD+N 1% f = 1 kHz BTL

RL = 8 Ω

RL = 32 Ω

2.5 3.53 4 5.5 VDD – Supply Voltage – V

4.5 5

Figure 5

600

VDD = 5 V

500

400

– Output Power – mW

300

200

100

VDD = 3.3 V

16 3224 40 64

RL – Load Resistance – Ω

48 56

Figure 6

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Page 7

TPA701

700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

TYPICAL CHARACTERISTICS

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

VDD = 3.3 V PO = 250 mW RL = 8 Ω BTL

0.1

THD+N –Total Harmonic Distortion + Noise – %

0.01 20 1k 10k

AV = –20 V/V

AV =– 10 V/V

AV = –2 V/V

f – Frequency – Hz

Figure 7

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

VDD = 3.3 V f = 1 kHz AV = –2 V/V BTL

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

VDD = 3.3 V RL = 8 Ω AV = –2 V/V BTL

0.1

THD+N –Total Harmonic Distortion + Noise – %

20k100

0.01 20 1k 10k

PO = 250 mW

f – Frequency – Hz

PO = 50 mW

PO = 125 mW

20k100

Figure 8

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

f = 20 kHz

RL = 8 Ω

0.1

THD+N –Total Harmonic Distortion + Noise – %

0.01 0 0.15 0.4

0.05 0.1 PO – Output Power – W

0.2 0.25 0.3 0.35

Figure 9

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0.1

THD+N –Total Harmonic Distortion + Noise – %

0.01

0.01 0.1 1

f = 10 kHz

f = 1 kHz

f = 20 Hz

PO – Output Power – W

VDD = 3.3 V RL = 8 Ω CB = 1 µF AV = –2 V/V BTL

Figure 10

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TPA701 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

TYPICAL CHARACTERISTICS

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

VDD = 5 V PO = 700 mW RL = 8 Ω BTL

AV = –10 V/V

0.1

THD+N –Total Harmonic Distortion + Noise – %

0.01 20 1k 10k

AV = –20 V/V

AV = –2 V/V

f – Frequency – Hz

Figure 11

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

VDD = 5 V f = 1 kHz AV = –2 V/V BTL

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

VDD = 5 V RL = 8 Ω AV = –2 V/V BTL

0.1

THD+N –Total Harmonic Distortion + Noise – %

20k100

0.01 20 1k 10k

PO = 700 mW

f – Frequency – Hz

PO = 50 mW

PO = 350 mW

20k100

Figure 12

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

f = 10 kHz

f = 20 kHz

RL = 8 Ω

0.1

THD+N –Total Harmonic Distortion + Noise – %

0.01

0.1 0.2 10.4 0.5 0.7 0.8

0.3 0.6 0.9 PO – Output Power – W

0.1 VDD = 5 V

RL = 8 Ω CB = 1 µF

THD+N –Total Harmonic Distortion + Noise – %

AV = –2 V/V BTL

0.01

0.01 0.1 1

Figure 13

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f = 1 kHz

f = 20 Hz

PO – Output Power – W

Figure 14

Page 9

Open-Loop Gain – dB

80 70

60 50 40

30 20

–10 –20

–30

700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

TYPICAL CHARACTERISTICS

OPEN-LOOP GAIN AND PHASE

FREQUENCY

Phase

Gain

f – Frequency – kHz

VDD = 3.3 V RL = Open BTL

TPA701

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

180°

140°

100°

60°

20°

Phase

–20°

–60°

–100°

–140°

–180°

Open-Loop Gain – dB

80 70 60 50 40 30 20 10

–10 –20

–30

Figure 15

OPEN-LOOP GAIN AND PHASE

FREQUENCY

180°

140°

100°

60°

20°

–20°

–60°

–100°

–140°

–180°

Phase

VDD = 5 V RL = Open BTL

Phase

Gain

f – Frequency – kHz

Figure 16

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Page 10

TPA701 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

TYPICAL CHARACTERISTICS

CLOSED-LOOP GAIN AND PHASE

FREQUENCY

Closed-Loop Gain – dB

0.75

0.5

0.25

–0.25

–0.5

–0.75

–1

–1.25

–1.5

–1.75

–2

VDD = 3.3 V RL = 8 Ω PO = 250 mW BTL

Phase

Gain

f – Frequency – Hz

180°

170°

160°

150°

Phase

140°

130°

120°

Closed-Loop Gain – dB

0.75

0.5

0.25

–0.25

–0.5

–0.75

–1

–1.25

–1.5

–1.75

–2

Figure 17

CLOSED-LOOP GAIN AND PHASE

FREQUENCY

VDD = 5 V RL = 8 Ω PO = 700 m W BTL

Phase

Gain

f – Frequency – Hz

Figure 18

180°

170°

160°

150°

Phase

140°

130°

120°

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Page 11

TPA701

700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

TYPICAL CHARACTERISTICS

OUTPUT NOISE VOLTAGE

FREQUENCY

100

VDD = 3.3 V BW = 22 Hz to 22 kHz RL = 8 Ω or 32 Ω AV = –1 V/V

VO BTL

– Output Noise Voltage – VµV

20 1k 10k

f – Frequency – Hz

Figure 19

POWER DISSIPATION

OUTPUT POWER

350

BTL Mode VDD = 3.3 V

300

RL = 8 Ω

OUTPUT NOISE VOLTAGE

FREQUENCY

100

VDD = 5 V BW = 22 Hz to 22 kHz RL = 8 Ω or 32 Ω AV = –1 V/V

VO BTL

– Output Noise Voltage – VµV

20k100

20 1k 10k

f – Frequency – Hz

20k100

Figure 20

POWER DISSIPATION

OUTPUT POWER

800

BTL Mode

700

VDD = 5 V

RL = 8 Ω

– Power Dissipation – mW

250

200

150

100

600

500

400

300

RL = 32 Ω

200 400

PD – Output Power – mW

6000

Figure 21

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– Power Dissipation – mW

200

100

RL = 32 Ω

200 800

400 6000 1000

PD – Output Power – mW

Figure 22

Page 12

TPA701 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

APPLICATION INFORMATION

bridged-tied load

Figure 23 shows a linear audio power amplifier (AP A) in a BTL configuration. The TPA701 BTL amplifier consists of two linear amplifiers driving both ends of the load. There are several potential benefits to this differential drive configuration but initially consider power to the load. The differential drive to the speaker means that as one side is slewing up, the other side is slewing down, and vice versa. This, in effect, doubles the voltage swing on the load as compared to a ground referenced load. Plugging 2 × V squared, yields 4× the output power from the same supply rail and load impedance (see equation 1).

(rms)

O(PP)

into the power equation, where voltage is

O(PP)

Power +

(rms)

O(PP)

2x V

–V

O(PP)

(1)

Figure 23. Bridge-Tied Load Configuration

In a typical portable handheld equipment sound channel operating at 3.3 V, bridging raises the power into an 8-Ω speaker from a singled-ended (SE, ground reference) limit of 62.5 mW to 250 mW. In sound power that is a 6-dB improvement, which is loudness that can be heard. In addition to increased power, there are frequency response concerns. Consider the single-supply SE configuration shown in Figure 24. A coupling capacitor is required to block the dc offset voltage from reaching the load. These capacitors can be quite large (approximately 33 µF to 1000 µF) so they tend to be expensive, heavy, occupy valuable PCB area, and have the additional drawback of limiting low-frequency performance of the system. This frequency-limiting effect is due to the high pass filter network created with the speaker impedance and the coupling capacitance and is calculated with equation 2.

2p RLC

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(2)

Page 13

700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

APPLICATION INFORMATION

bridged-tied load (continued)

For example, a 68-µF capacitor with an 8-Ω speaker would attenuate low frequencies below 293 Hz. The BTL configuration cancels the dc offsets, which eliminates the need for the blocking capacitors. Low-frequency performance is then limited only by the input network and speaker response. Cost and PCB space are also minimized by eliminating the bulky coupling capacitor.

TPA701

O(PP)

–3 dB

Figure 24. Single-Ended Configuration and Frequency Response

Increasing power to the load does carry a penalty of increased internal power dissipation. The increased dissipation is understandable considering that the BTL configuration produces 4× the output power of a SE configuration. Internal dissipation versus output power is discussed further in the thermal considerations section.

BTL amplifier efficiency

Linear amplifiers are inefficient. The primary cause of these inefficiencies is voltage drop across the output stage transistors. There are two components of the internal voltage drop. One is the headroom or dc voltage drop that varies inversely to output power. The second component is due to the sinewave nature of the output. The total voltage drop can be calculated by subtracting the RMS value of the output voltage from V drop multiplied by the RMS value of the supply current, I

rms, determines the internal power dissipation of

the amplifier.

. The internal voltage

An easy-to-use equation to calculate efficiency starts out being equal to the ratio of power from the power supply to the power delivered to the load. To accurately calculate the RMS values of power in the load and in the amplifier, the current and voltage waveform shapes must first be understood (see Figure 25).

DD(RMS)

(LRMS)

Figure 25. Voltage and Current Waveforms for BTL Amplifiers

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TPA701 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

APPLICATION INFORMATION

BTL amplifier efficiency (continued)

Although the voltages and currents for SE and BTL are sinusoidal in the load, currents from the supply are very different between SE and BTL configurations. In an SE application the current waveform is a half-wave rectified shape, whereas in BTL it is a full-wave rectified waveform. This means RMS conversion factors are different. Keep in mind that for most of the waveform both the push and pull transistors are not on at the same time, which supports the fact that each amplifier in the BTL device only draws current from the supply for half the waveform. The following equations are the basis for calculating amplifier efficiency.

Efficiency +

where

IDDrms +

SUP

VLrms

VLrms +

+ VDDIDDrms +

SUP

p R

VDD2V

p R

(3)

1ń2

Efficiency of a BTL configuration

p V

2PLR

(4)

T able 1 employs equation 4 to calculate efficiencies for three dif ferent output power levels. The efficiency of the amplifier is quite low for lower power levels and rises sharply as power to the load is increased, resulting in a nearly flat internal power dissipation over the normal operating range. The internal dissipation at full output power is less than in the half-power range. Calculating the efficiency for a specific system is the key to proper power supply design.

Table 1. Efficiency Vs Output Power in 3.3-V 8-Ω BTL Systems

OUTPUT POWER

(W)

0.125 33.6 1.41 0.26

0.25 47.6 2.00 0.29

0.375 58.3 2.45

†

High-peak voltage values cause the THD to increase.

EFFICIENCY

(%)

PEAK VOLTAGE

(V)

†

INTERNAL

DISSIPATION

(W)

0.28

A final point to remember about linear amplifiers (either SE or BTL) is how to manipulate the terms in the efficiency equation to utmost advantage when possible. In equation 4, V that as V

goes down, efficiency goes up.

is in the denominator. This indicates

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Page 15

700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

APPLICATION INFORMATION

application schematic

Figure 26 is a schematic diagram of a typical handheld audio application circuit, configured for a gain of –10 V/V.

VO+

VO– 8

1 µF

700 mW

Audio

Input

50 kΩ

10 kΩ

2.2 µF

IN –

3 IN+

24BYPASS

VDD/2

–

TPA701

From System Control

SHUTDOWN

Bias

Control

GND

Figure 26. TPA701 Application Circuit

The following sections discuss the selection of the components used in Figure 26.

component selection

gain setting resistors, RF and R

The gain for each audio input of the TP A701 is set by resistors RF and RI according to equation 5 for BTL mode.

BTL gain +*2

BTL mode operation brings about the factor 2 in the gain equation due to the inverting amplifier mirroring the voltage swing across the load. Given that the TPA701 is a MOS amplifier, the input impedance is very high; consequently input leakage currents are not generally a concern, although noise in the circuit increases as the value of R

increases. In addition, a certain range of RF values is required for proper start-up operation of the

amplifier. Taken together, it is recommended that the effective impedance seen by the inverting node of the amplifier be set between 5 kΩ and 20 kΩ. The effective impedance is calculated in equation 6.

(5)

Effective impedance +

RFR

RF) R

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(6)

Page 16

TPA701 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

APPLICATION INFORMATION

component selection (continued)

As an example consider an input resistance of 10 kΩ and a feedback resistor of 50 kΩ. The BTL gain of the amplifier would be –10 V/V and the effective impedance at the inverting terminal would be 8.3 kΩ, which is well within the recommended range.

For high performance applications, metal film resistors are recommended because they tend to have lower noise levels than carbon resistors. For values of R to a pole formed from R

and the inherent input capacitance of the MOS input structure. For this reason, a small

compensation capacitor of approximately 5 pF should be placed in parallel with R 50 kΩ. This, in effect, creates a low pass filter network with the cutoff frequency defined in equation 7.

–3 dB

above 50 kΩ, the amplifier tends to become unstable due

when RF is greater than

c(lowpass)

2p RFC

For example, if RF is 100 kΩ and CF is 5 pF, then fco is 318 kHz, which is well outside of audio range.

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, C

and RI form a high-pass filter with the corner frequency

determined in equation 8.

–3 dB

c(highpass)

2p RIC

(7)

(8)

The value of CI is important to consider as it directly affects the bass (low frequency) performance of the circuit. Consider the example where R

is 10 kΩ and the specification calls for a flat bass response down to 40 Hz.

Equation 8 is reconfigured as equation 9.

2p RIf

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

(9)

Page 17

700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

APPLICATION INFORMATION

component selection (continued)

In this example, CI is 0.40 µF, so one would likely choose a value in the range of 0.47 µF to 1 µF. A further consideration for this capacitor is the leakage path from the input source through the input network (R the feedback resistor (R that reduces useful headroom, especially in high gain applications. For this reason a low-leakage tantalum or ceramic capacitor is the best choice. When polarized capacitors are used, the positive side of the capacitor should face the amplifier input in most applications, as the dc level there is held at V than the source dc level. It is important to confirm the capacitor polarity in the application.

) to the load. This leakage current creates a dc offset voltage at the input to the amplifier

/2, which is likely higher

TPA701

, CI) and

power supply decoupling, C

The TP A701 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling to ensure the output total harmonic distortion (THD) is as low as possible. Power supply decoupling also prevents oscillations for long lead lengths between the amplifier and the speaker. The optimum decoupling is achieved by using two capacitors of different types that target different types of noise on the power supply leads. For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-series-resistance (ESR) ceramic capacitor, typically 0.1 µF placed as close as possible to the device V lower-frequency noise signals, a larger aluminum electrolytic capacitor of 10 µF or greater placed near the audio power amplifier is recommended.

midrail bypass capacitor, C

The midrail bypass capacitor, CB, is the most critical capacitor and serves several important functions. During start-up or recovery from shutdown mode, C function is to reduce noise produced by the power supply caused by coupling into the output drive signal. This noise is from the midrail generation circuit internal to the amplifier, which appears as degraded PSRR and THD + N. The capacitor is fed from a 250-kΩ source inside the amplifier. To keep the start-up pop as low as possible, the relationship shown in equation 10 should be maintained. This insures the input capacitor is fully charged before the bypass capacitor is fully charged and the amplifier starts up.

CB 250 kΩ

As an example, consider a circuit where CB is 2.2 µF, CI is 0.47 µF, RF is 50 kΩ, and RI is 10 kΩ. Inserting these values into the equation 10 we get:

RF) R

lead works best. For filtering

determines the rate at which the amplifier starts up. The second

(10)

18.2 v 35.5

which satisfies the rule. Bypass capacitor, C are recommended for the best THD and noise performance.

, values of 0.1 µF to 2.2 µF ceramic or tantalum low-ESR capacitors

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.

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Page 18

TPA701 700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

APPLICATION INFORMATION

5-V versus 3.3-V operation

The TP A701 operates over a supply range of 2.5 V to 5.5 V. This data sheet provides full specifications for 5-V and 3.3-V operation, as these are considered to be the two most common standard voltages. There are no special considerations for 3.3-V versus 5-V operation with respect to supply bypassing, gain setting, or stability . The most important consideration is that of output power. Each amplifier in TPA701 can produce a maximum voltage swing of V opposed to V

O(PP)

an 8-Ω load before distortion becomes significant. Operation from 3.3-V supplies, as can be shown from the efficiency formula in equation 4, consumes

approximately two-thirds the supply power of operation from 5-V supplies for a given output-power level.

headroom and thermal considerations

Linear power amplifiers dissipate a significant amount of heat in the package under normal operating conditions. A typical music CD requires 12 dB to 15 dB of dynamic headroom to pass the loudest portions without distortion as compared with the average power output. From the TP A701 data sheet, one can see that when the TP A701 is operating from a 5-V supply into a 8-Ω speaker that 700 mW peaks are available. Converting watts to dB:

– 1 V. This means, for 3.3-V operation, clipping starts to occur when V

O(PP)

= 4 V at 5 V . The reduced voltage swing subsequently reduces maximum output power into

= 2.3 V as

PdB+ 10Log

ref

+ 10Log

700 mW

+ –1.5 dB

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

–1.5 dB – 15 dB = –16.5 (15 dB headroom) –1.5 dB – 12 dB = –13.5 (12 dB headroom) –1.5 dB – 9 dB = –10.5 (9 dB headroom) –1.5 dB – 6 dB = –7.5 (6 dB headroom) –1.5 dB – 3 dB = –4.5 (3 dB headroom)

Converting dB back into watts:

PW+ 10

PdBń10

ref

+ 22 mW (15 dB headroom) + 44 mW (12 dB headroom) + 88 mW (9 dB headroom) + 175 mW (6 dB headroom) + 350 mW (3 dB headroom)

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Page 19

700-mW MONO LOW-VOLTAGE AUDIO POWER AMPLIFIER

AVERAGE OUTPUT

SLOS229D – NOVEMBER1998 – REVISED MAY 2003

APPLICATION INFORMATION

headroom and thermal considerations (continued)

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 700 mW of continuous power output with 0 dB of headroom, against 12 dB and 15 dB applications drastically affects maximum ambient temperature ratings for the system. Using the power dissipation curves for a 5-V , 8-Ω system, the internal dissipation in the TP A701 and maximum ambient temperatures is shown in Table 2.

Table 2. TPA701 Power Rating, 5-V, 8-Ω, BTL

TPA701

PEAK OUTPUT

POWER

(mW)

700 700 mW 675 700 350 mW (3 dB) 595 700 176 mW (6 dB) 475 700 88 mW (9 dB) 350 700 44 mW (12 dB) 225

AVERAGE OUTPUT

POWER

DISSIPATION

(mW)

D PACKAGE

(SOIC)

MAXIMUM AMBIENT

TEMPERATURE

34°C 110°C 47°C 115°C 68°C 122°C 89°C 125°C

111°C 125°C

DGN PACKAGE

(MSOP)

MAXIMUM AMBIENT

TEMPERATURE

Table 2 shows that the TPA701 can be used to its full 700-mW rating without any heat sinking in still air up to 110°C and 34°C for the DGN package (MSOP) and D package (SOIC) respectively.

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

Page 20

PACKAGE OPTION ADDENDUM

www.ti.com

18-Apr-2006

PACKAGING INFORMATION

Orderable Device Status

(1)

Package

Type

Package Drawing

Pins Package

Qty

Eco Plan

TPA701D ACTIVE SOIC D 8 75 Green(RoHS &

no Sb/Br)

TPA701DG4 ACTIVE SOIC D 8 75 Green (RoHS &

no Sb/Br)

TPA701DGN ACTIVE MSOP-

Power

DGN 8 80 Green (RoHS &

no Sb/Br)

PAD

TPA701DGNG4 ACTIVE MSOP-

Power

DGN 8 80 Green (RoHS &

no Sb/Br)

PAD

TPA701DGNR ACTIVE MSOP-

Power

DGN 8 2500 Green (RoHS &

no Sb/Br)

PAD

TPA701DGNRG4 ACTIVE MSOP-

Power

DGN 8 2500 Green (RoHS &

no Sb/Br)

PAD

TPA701DR ACTIVE SOIC D 8 2500 Green (RoHS &

no Sb/Br)

TPA701DRG4 ACTIVE SOIC D 8 2500 Green (RoHS &

no Sb/Br)

TPA701EVM OBSOLETE 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)

Lead/Ball Finish MSL Peak Temp

CU NIPDAU Level-1-260C-UNLIM

(3)

(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

Page 21

PACKAGE MATERIALS INFORMATION

www.ti.com

TAPE AND REEL INFORMATION

11-Mar-2008

*All dimensions are nominal

Device Package

Type

TPA701DGNR MSOP-

Power

TPA701DR SOIC D 8 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1

PAD

Package Drawing

DGN 8 2500 330.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1

Pins SPQ Reel

Diameter

(mm)

Reel

Width

W1 (mm)

A0 (mm) B0 (mm) K0 (mm) P1

(mm)W(mm)

Pin1

Quadrant

Pack Materials-Page 1

Page 22

PACKAGE MATERIALS INFORMATION

www.ti.com

11-Mar-2008

*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

TPA701DGNR MSOP-PowerPAD DGN 8 2500 358.0 335.0 35.0

TPA701DR SOIC D 8 2500 346.0 346.0 29.0

Pack Materials-Page 2

Page 23

Page 24

Page 25

Page 26

Page 27

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