TPA311EVM - Texas Instruments

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

Fully Specified for 3.3-V and 5-V Operation

Wide Power Supply Compatibility

2.5 V – 5.5 V

Output Power for RL = 8 Ω

– 350 mW at VDD = 5 V, BTL

– 250 mW at VDD = 5 V, SE

– 250 mW at VDD = 3.3 V, BTL

– 75 mW at VDD = 3.3 V, SE

Shutdown Control

– IDD = 7 µA at 3.3 V

– IDD = 60 µA at 5 V

BTL to SE Mode Control

Integrated Depop Circuitry

Thermal and Short-Circuit Protection

Surface Mount Packaging

– SOIC

– PowerPAD MSOP

description

The TPA311 is a bridge-tied load (BTL) or

single-ended (SE) audio power amplifier devel-

oped especially for low-voltage applications

where internal speakers and external earphone

operation are required. Operating with a 3.3-V

supply, the TPA311 can deliver 250-mW of

continuous power into a BTL 8-Ω load at less than 1% 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

cellular 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. A unique

feature of the TPA31 1 is that it allows the amplifier to switch from BTL to SE

on the fly

when an earphone drive

is required. This eliminates complicated mechanical switching or auxiliary devices just to drive the external load.

This device features a shutdown mode for power-sensitive applications with special depop circuitry to virtually

eliminate speaker noise when exiting shutdown mode and during power cycling. The TP A311 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

Bias

Control

350 mW

VO+

VDD

BYPASS

SE/BTL

VDD/2

CBF

SHUTDOWN

From HP Jack

VO–8

GND

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.

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.

SHUTDOWN

BYPASS

SE/BTL

VO–

GND

VDD

VO+

D OR DGN PACKAGE

(TOP VIEW)

PowerPAD is a trademark of Texas Instruments.

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

2POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

AVAILABLE OPTIONS

PACKAGED DEVICES

MSOP

TASMALL OUTLINE†

(D) MSOP†

(DGN)

MSOP

Symbolization

–40°C to 85°C TPA311D TPA311DGN AAB

†The D and DGN packages are available taped and reeled. To order a taped and reeled part, add

the suffix R to the part number (e.g., TPA311DR).

Terminal Functions

TERMINAL

I/O

DESCRIPTION

NAME NO.

I/O

DESCRIPTION

BYPASS 2 I BYP ASS is the tap to the voltage divider for internal mid-supply bias. This terminal should be connected

to a 0.1-µF to 1-µF capacitor when used as an audio amplifier.

GND 7GND is the ground connection.

IN 4 I IN is the audio input terminal.

SE/BTL 3 I When SE/BTL is held low, the TPA311 is in BTL mode. When SE/BTL is held high, the TPA311 is in SE

mode.

SHUTDOWN 1 I SHUTDOWN places the entire device in shutdown mode when held high (IDD = 60 µA, VDD = 5 V).

VDD 6 VDD is the supply voltage terminal.

VO+ 5 O VO+ is the positive output for BTL and SE modes.

VO– 8 O VO– is the negative output in BTL mode and a high-impedance output in SE mode.

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

Supply voltage, VDD 6 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Input voltage, VI –0.3 V to VDD +0.3 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

Operating free-air temperature range, TA (see Table 3) –40°C to 85°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Operating junction temperature range, TJ –40°C to 150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Storage temperature range, Tstg –65°C to 150°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 af fect device reliability.

DISSIPATION RATING TABLE

PACKAGE TA ≤ 25°CDERATING FACTOR TA = 70°C TA = 85°C

D725 mW 5.8 mW/°C464 mW 377 mW

DGN 2.14 W§17.1 mW/°C1.37 W 1.11 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

T exas Instruments Recommended

Board for PowerPAD

on page 33 of the before mentioned document.

recommended operating conditions

MIN MAX UNIT

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Supply voltage, VDD

ÁÁÁ

2.5

ÁÁÁ

5.5

ÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Operating free-air temperature, TA (see Table 3)

ÁÁÁ

–40

ÁÁÁ

°C

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

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

noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

ÁÁÁ

VOO

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Output offset voltage (measured dif ferentially)

ÁÁÁÁÁÁÁÁÁ

See Note 1

ÁÁÁ

PSRR

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Power su

ly rejection ratio

ÁÁÁÁÁÁ

VDD =32Vto34V

ÁÁÁÁ

BTL mode

ÁÁÁ

PSRR

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

ppl

rejection

ratio

ÁÁÁÁÁÁ

DD =

ÁÁÁÁ

SE mode

ÁÁÁ

IDD

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

ly current (see Figure 6)

ÁÁÁÁÁÁÁÁÁ

BTL mode

ÁÁÁ

0.7

ÁÁÁ

1.5

ÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

ppl

rrent

(see

Fig

ÁÁÁÁÁÁÁÁÁ

SE mode

ÁÁÁ

0.35

ÁÁÁ

0.75

ÁÁÁ

IDD(SD)

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Supply current, shutdown mode (see Figure 7)

ÁÁÁÁÁÁÁÁÁ

ÁÁÁ

µA

NOTE 1: At 3 V < VDD < 5 V the dc output voltage is approximately VDD/2.

operating characteristics, VDD = 3.3 V, TA = 25°C, RL = 8 Ω

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁ

Out

ower see Note 2

ÁÁÁÁÁ

THD = 0.5%,

ÁÁÁÁÁÁ

BTL mode,

ÁÁÁÁÁ

See Figure 14

ÁÁÁ

250

ÁÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁ

see

Note

ÁÁÁÁÁ

THD = 0.5%,

ÁÁÁÁÁÁ

SE mode

ÁÁÁÁÁ

ÁÁÁ

110

ÁÁÁ

ÁÁÁÁ

THD + N

ÁÁÁÁÁÁÁÁÁ

Total harmonic distortion plus

noise

ÁÁÁÁÁ

PO = 250 mW,

See Figure 12

ÁÁÁÁÁÁ

f = 20 Hz to 4 kHz,

ÁÁÁÁÁ

Gain = 2,

ÁÁÁ

1.3%

ÁÁÁ

ÁÁÁÁ

BOM

ÁÁÁÁÁÁÁÁÁ

Maximum output power bandwidth

ÁÁÁÁÁ

Gain = 2,

ÁÁÁÁÁÁ

THD = 3%,

ÁÁÁÁÁ

See Figure 12

ÁÁÁ

kHz

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁ

Unity-gain bandwidth

ÁÁÁÁÁ

Open Loop,

ÁÁÁÁÁÁ

See Figure 36

ÁÁÁÁÁ

ÁÁÁ

1.4

ÁÁÁ

MHz

ÁÁÁÁ

ÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁÁÁ

ly ri

le rejection ratio

ÁÁÁÁÁ

ÁÁÁ

ÁÁÁÁÁ

f = 1 kHz,

See Figure 5

ÁÁÁÁÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁ

CB = 1 µF,

ÁÁÁÁÁ

ÁÁÁ

ÁÁÁÁÁ

BTL mode,

ÁÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁ

ppl

ripple

rejection

ratio

ÁÁÁÁÁ

f = 1 kHz,

See Figure 3

ÁÁÁÁÁÁ

CB = 1 µF,

ÁÁÁÁÁ

SE mode,

ÁÁÁ

ÁÁÁÁ

ÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁÁÁ

Noise output voltage

ÁÁÁÁÁ

ÁÁÁ

ÁÁÁÁÁ

Gain = 1,

BTL,

ÁÁÁÁÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁ

CB = 0.1 µF,

See Figure 42

ÁÁÁÁÁ

ÁÁÁ

ÁÁÁÁÁ

RL = 32 Ω,

ÁÁÁ

µV(rms)

NOTE 2: Output power is measured at the output terminals of the device at f = 1 kHz.

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

4POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

electrical characteristics at specified free-air temperature, VDD = 5 V, T A = 25°C (unless otherwise

noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

ÁÁÁÁ

VOO

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Output offset voltage (measured dif ferentially)

ÁÁÁÁÁÁÁÁÁÁ

ÁÁÁ

ÁÁÁÁ

PSRR

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Power su

ly rejection ratio

ÁÁÁÁÁÁÁ

VDD =49Vto51V

ÁÁÁÁ

BTL mode

ÁÁÁ

ÁÁÁÁ

PSRR

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

ppl

rejection

ratio

ÁÁÁÁÁÁÁ

DD =

ÁÁÁÁ

SE mode

ÁÁÁ

ÁÁÁÁ

IDD

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

ly current (see Figure 6)

ÁÁÁÁÁÁÁÁÁÁ

BTL mode

ÁÁÁ

0.7

ÁÁÁ

1.5

ÁÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

ppl

rrent

(see

Fig

ÁÁÁÁÁÁÁÁÁÁ

SE mode

ÁÁÁ

0.35

ÁÁÁ

0.75

ÁÁÁ

ÁÁÁÁ

IDD(SD)

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Supply current, shutdown mode (see Figure 7)

ÁÁÁÁÁÁÁÁÁÁ

ÁÁÁ

100

ÁÁÁ

µA

operating characteristics, VDD = 5 V, TA = 25°C, RL = 8 Ω

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁ

Out

ower see Note 2

ÁÁÁÁÁ

THD = 0.5%,

ÁÁÁÁÁÁ

BTL mode,

ÁÁÁÁÁ

See Figure 18

ÁÁÁ

700

ÁÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁ

see

Note

ÁÁÁÁÁ

THD = 0.5%,

ÁÁÁÁÁÁ

SE mode

ÁÁÁÁÁ

ÁÁÁ

300

ÁÁÁ

ÁÁÁÁ

ÁÁ

ÁÁÁÁ

THD + N

ÁÁÁÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁ

Total harmonic distortion plus

noise

ÁÁÁÁÁ

ÁÁÁ

ÁÁÁÁÁ

PO = 350 mW,

See Figure 16

ÁÁÁÁÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁ

f = 20 Hz to 4 kHz,

ÁÁÁÁÁ

ÁÁÁ

ÁÁÁÁÁ

Gain = 2,

ÁÁÁ

ÁÁÁÁ

BOM

ÁÁÁÁÁÁÁÁÁÁ

Maximum output power bandwidth

ÁÁÁÁÁ

Gain = 2,

ÁÁÁÁÁÁ

THD = 2%,

ÁÁÁÁÁ

See Figure 16

ÁÁÁ

kHz

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁ

Unity-gain bandwidth

ÁÁÁÁÁ

Open Loop,

ÁÁÁÁÁÁ

See Figure 37

ÁÁÁÁÁ

ÁÁÁ

1.4

ÁÁÁ

MHz

ÁÁÁÁ

ÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁ

ly ri

le rejection ratio

ÁÁÁÁÁ

ÁÁÁ

ÁÁÁÁÁ

f = 1 kHz,

See Figure 5

ÁÁÁÁÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁ

CB = 1 µF,

ÁÁÁÁÁ

ÁÁÁ

ÁÁÁÁÁ

BTL mode,

ÁÁÁ

ÁÁÁÁ

ÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁ

ppl

ripple

rejection

ratio

ÁÁÁÁÁ

ÁÁÁ

ÁÁÁÁÁ

f = 1 kHz,

See Figure 4

ÁÁÁÁÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁ

CB = 1 µF,

ÁÁÁÁÁ

ÁÁÁ

ÁÁÁÁÁ

SE mode,

ÁÁÁ

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁ

Noise output voltage

ÁÁÁÁÁ

Gain = 1,

BTL,

ÁÁÁÁÁÁ

CB = 0.1 µF,

See Figure 43

ÁÁÁÁÁ

RL = 32 Ω,

ÁÁÁ

µV(rms)

NOTE 2: Output power is measured at the output terminals of the device at f = 1 kHz.

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

PARAMETER MEASUREMENT INFORMATION

Audio

Input

Bias

Control

VDD

VO+

VDD

BYPASS

SE/BTL

VDD/2

1 µF

0.1 µF

SHUTDOWN

VO–8

RL = 8 Ω

GND

–

Figure 1. BTL Mode Test Circuit

Audio

Input

Bias

Control

VDD

VO+

VDD

BYPASS

SE/BTL

VDD/2

1 µF

0.1 µF

SHUTDOWN

VO–8

RL = 32 Ω

GND

330 µF

VDD

–

Figure 2. SE Mode Test Circuit

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

6POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Table of Graphs

FIGURE

Supply voltage rejection ratio vs Frequency 3, 4, 5

IDD Supply current vs Supply voltage 6, 7

Out

ower

vs Supply voltage 8, 9

vs Load resistance 10, 11

THD+N

Total harmonic distortion

lus noise

vs Frequency 12, 13, 16, 17, 20,

21, 24, 25, 28, 29,

32, 33

THD

Total

harmonic

distortion

noise

vs Output power 14, 15, 18, 19, 22,

23, 26, 27, 30, 31,

34, 35

Open loop gain and phase vs Frequency 36, 37

Closed loop gain and phase vs Frequency 38, 39, 40, 41

VnOutput noise voltage vs Frequency 42, 43

PDPower dissipation vs Output power 44, 45, 46, 47

TYPICAL CHARACTERISTICS

Figure 3

–50

–60

–80

–10020 100 1 k

–30

–20

f – Frequency – Hz

SUPPLY VOLTAGE REJECTION RATIO

FREQUENCY

10 k 20 k

–10

–40

–70

–90 BYPASS = 1/2 VDD

CB = 0.1 µF

VDD = 3.3 V

RL = 8 Ω

CB = 1 µF

Supply Voltage Rejection Ratio – dB

Figure 4

–50

–60

–80

–10020 100 1 k

–30

–20

f – Frequency – Hz

SUPPLY VOLTAGE REJECTION RATIO

FREQUENCY

10 k 20 k

–10

–40

–70

–90

BYPASS = 1/2 VDD

CB = 0.1 µF

VDD = 5 V

RL = 8 Ω

CB = 1 µF

Supply Voltage Rejection Ratio – dB

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 5

–50

–60

–80

–10020 100 1 k

–30

–20

f – Frequency – Hz

SUPPLY VOLTAGE REJECTION RATIO

FREQUENCY

10 k 20 k

–10

–40

–70

–90

VDD = 5 V

VDD = 3.3 V

RL = 8 Ω

CB = 1 µF

BTL

Supply Voltage Rejection Ratio – dB

Figure 6

VDD – Supply Voltage – V

SUPPLY CURRENT

SUPPLY VOLTAGE

1.1

0.7

0.3

–0.1

0.9

0.5

0.1

34 625

BTL

IDD– Supply Current – mA

VDD – Supply Voltage – V

SUPPLY CURRENT (SHUTDOWN)

SUPPLY VOLTAGE

0343.5 4.5

SHUTDOWN = High

5.52.5

IDD(SD)– Supply Current – Aµ

Figure 7

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

8POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 8

VDD – Supply Voltage – V

OUTPUT POWER

SUPPLY VOLTAGE

600

400

200

02.5 3.53 4 5.5

1000

4.5 5

O– Output Power – mW

800

THD+N 1%

BTL

RL = 32 Ω

RL = 8 Ω

Figure 9

VDD – Supply Voltage – V

OUTPUT POWER

SUPPLY VOLTAGE

150

100

0343.5 4.5

350

O– Output Power – mW

200

THD+N 1%

RL = 32 Ω

RL = 8 Ω

250

300

5.52.5

Figure 10

RL – Load Resistance – Ω

OUTPUT POWER

LOAD RESISTANCE

300

200

100

016 3224 40 64

800

48 56

O– Output Power – mW

400

THD+N = 1%

BTL

VDD = 5 V

500

600

VDD = 3.3 V

700

Figure 11

RL – Load Resistance – Ω

OUTPUT POWER

LOAD RESISTANCE

14 2620 32 5083844

THD+N = 1%

VDD = 5 V

VDD = 3.3 V

56 62

150

100

350

PO– Output Power – mW

200

250

300

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 12

f – Frequency – Hz

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

AV = –2 V/V

VDD = 3.3 V

PO = 250 mW

RL = 8 Ω

BTL

20 1k 10k

0.01

0.1

20k100

AV = –20 V/V

AV = –10 V/V

Figure 13

f – Frequency – Hz

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

PO = 125 mW

VDD = 3.3 V

RL = 8 Ω

AV = –2 V/V

BTL

20 1k 10k

0.01

0.1

20k100

PO = 50 mW

PO = 250 mW

Figure 14

PO – Output Power – W

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

RL = 8 Ω

0.04 0.1 0.4

0.01

0.1

0.16 0.22 0.28 0.34

VDD = 3.3 V

f = 1 kHz

AV = –2 V/V

BTL

Figure 15

PO – Output Power – W

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

f = 20 Hz VDD = 3.3 V

RL = 8 Ω

AV = –2 V/V

BTL

0.01 0.1 1

0.01

0.1

f = 1 kHz

f = 10 kHz

f = 20 kHz

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

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TYPICAL CHARACTERISTICS

Figure 16

f – Frequency – Hz

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

AV = –2 V/V

VDD = 5 V

PO = 350 mW

RL = 8 Ω

BTL

20 1k 10k

0.01

0.1

20k100

AV = –20 V/V

AV = –10 V/V

Figure 17

f – Frequency – Hz

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

PO = 175 mW

VDD = 5 V

RL = 8 Ω

AV = –2 V/V

BTL

20 1k 10k

0.01

0.1

20k100

PO = 50 mW

PO = 350 mW

Figure 18

PO – Output Power – W

0.1 0.25 10.40 0.55 0.70 0.85

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

RL = 8 Ω

VDD = 5 V

f = 1 kHz

AV = –2 V/V

BTL

0.01

0.1

Figure 19

PO – Output Power – W

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

f = 20 Hz

VDD = 5 V

RL = 8 Ω

AV = –2 V/V

BTL

0.01 0.1 1

0.01

0.1

f = 1 kHz

f = 10 kHz

f = 20 kHz

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 20

f – Frequency – Hz

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

AV = –10 V/V

VDD = 3.3 V

PO = 30 mW

RL = 32 Ω

20 1k 10k

0.1

0.001

0.01

20k100

AV = –1 V/V

AV = –5 V/V

Figure 21

f – Frequency – Hz

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

VDD = 3.3 V

RL = 32 Ω

AV = –1 V/V

20 1k 10k

0.1

0.001

0.01

20k100

PO = 10 mW

PO = 15 mW

PO = 30 mW

Figure 22

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

VDD = 3.3 V

f = 1 kHz

RL = 32 Ω

AV = –1 V/V

0.01

0.1

PO – Output Power – W

0.02 0.025 0.050.03 0.035 0.04 0.045

Figure 23

PO – Output Power – W

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

f = 20 Hz

VDD = 3.3 V

RL = 32 Ω

AV = –1 V/V

0.01

0.1 f = 1 kHz

f = 10 kHz

f = 20 kHz

0.002 0.03 0.050.01 0.02

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

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TYPICAL CHARACTERISTICS

Figure 24

f – Frequency – Hz

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

AV = –10 V/V

VDD = 5 V

PO = 60 mW

RL = 32 Ω

20 1k 10k

0.1

0.001

0.01

20k100

AV = –1 V/V

AV = –5 V/V

Figure 25

f – Frequency – Hz

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

VDD = 5 V

RL = 32 Ω

AV = –1 V/V

20 1k 10k

0.1

0.001

0.01

20k100

PO = 15 mW

PO = 60 mW

PO = 30 mW

Figure 26

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

VDD = 5 V

f = 1 kHz

RL = 32 Ω

AV = –1 V/V

0.01

0.1

PO – Output Power – W

0.02 0.04 0.140.06 0.08 0.1 0.12

Figure 27

PO – Output Power – W

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

f = 20 Hz VDD = 5 V

RL = 32 Ω

AV = –1 V/V

0.01

0.1 f = 1 kHz

f = 10 kHz

f = 20 kHz

0.002 0.1 0.20.01

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 28

f – Frequency – Hz

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

VDD = 3.3 V

PO = 0.1 mW

RL = 10 kΩ

20 1k 10k

0.1

0.01

20k100

AV = –1 V/V

AV = –2 V/V

AV = –5 V/V

Figure 29

f – Frequency – Hz

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

VDD = 3.3 V

RL = 10 kΩ

AV = –1 V/V

20 1 k 10 k

0.1

0.01

20 k100

PO = 0.13 mW

PO = 0.1 mW

PO = 0.05 mW

Figure 30

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

VDD = 3.3 V

f = 1 kHz

RL = 10 kΩ

AV = –1 V/V

0.1

0.001

0.01

PO – Output Power – µW

50 75 200100 125 150 175

Figure 31

PO – Output Power – µW

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

f = 20 Hz

VDD = 3.3 V

RL = 10 kΩ

AV = –1 V/V

f = 1 kHz

f = 10 kHz

f = 20 kHz

5 100 500

0.1

0.001

0.01

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

14 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 32

f – Frequency – Hz

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

VDD = 5 V

PO = 0.3 mW

RL = 10 kΩ

20 1k 10k

0.1

0.01

20k100

AV = –1 V/V

AV = –2 V/V

AV = –5 V/V

Figure 33

f – Frequency – Hz

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

FREQUENCY

VDD = 5 V

RL = 10 kΩ

AV = –1 V/V

20 1k 10k

0.1

0.01

20k100

PO = 0.3 mW

PO = 0.1 mW

PO = 0.2 mW

Figure 34

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

VDD = 5 V

f = 1 kHz

RL = 10 kΩ

AV = –1 V/V

0.1

0.001

0.01

PO – Output Power – µW

50 125 500200 275 350 425

Figure 35

PO – Output Power – µW

THD+N –Total Harmonic Distortion + Noise – %

TOTAL HARMONIC DISTORTION PLUS NOISE

OUTPUT POWER

f = 20 Hz

VDD = 5 V

RL = 10 kΩ

AV = –1 V/V

f = 1 kHz

f = 10 kHz

f = 20 kHz

5 100 500

0.1

0.001

0.01

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

–20

–30

f – Frequency – kHz

–10

180

120

–120

–180

VDD = 3.3 V

RL = Open

BTL

Gain

Phase

–60

OPEN-LOOP GAIN AND PHASE

FREQUENCY

Open-Loop Gain – dB

Phase – °

1101102103104

Figure 36

–20

–30 1

f – Frequency – kHz

–10

180

120

–120

–180

VDD = 5 V

RL = Open

BTL

Gain

Phase

–60

OPEN-LOOP GAIN AND PHASE

FREQUENCY

Open-Loop Gain – dB

Phase – °

101102103104

Figure 37

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

16 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

CLOSED-LOOP GAIN AND PHASE

FREQUENCY

–0.5

–1

–1.5

–2

f – Frequency – Hz

–0.25

–0.75

–1.25

–1.75

0.5

Closed-Loop Gain – dB

0.25

0.75

130

120

140

Phase – °

150

160

VDD = 3.3 V

RL = 8 Ω

PO = 0.25 W

CI =1 µF

BTL

170

180

Gain

Phase

101102103104105106

Figure 38

CLOSED-LOOP GAIN AND PHASE

FREQUENCY

–0.5

–1

–1.5

–2

f – Frequency – Hz

–0.25

–0.75

–1.25

–1.75

0.5

Closed-Loop Gain – dB

0.25

0.75

130

120

140

Phase – °

150

160

VDD = 5 V

RL = 8 Ω

PO = 0.35 W

CI =1 µF

BTL

170

180

Gain

Phase

101102103104105106

Figure 39

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

CLOSED-LOOP GAIN AND PHASE

FREQUENCY

–1

–3

f – Frequency – Hz

–2

Closed-Loop Gain – dB

VDD = 3.3 V

RL = 32 Ω

AV = –2 V/V

PO = 30 mW

CI =1 µF

CC =470 µF

Gain

Phase

110

100

120

Phase – °

130

140

150

180

160

170

101102103104105106

Figure 40

CLOSED-LOOP GAIN AND PHASE

FREQUENCY

–2

f – Frequency – Hz

–1

Closed-Loop Gain – dB

110

100

120

Phase – °

130

140

VDD = 5 V

RL = 32 Ω

AV = –2 V/V

PO = 60 mW

CI =1 µF

CC =470 µF

150

180

Gain

Phase

160

170

101102103104105106

Figure 41

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

18 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 42

– Output Noise Voltage –µVn

f – Frequency – Hz

OUTPUT NOISE VOLTAGE

FREQUENCY

20 1 k 10 k

100

20 k100

VO BTL

VDD = 3.3 V

BW = 22 Hz to 22 kHz

RL = 32 Ω

CB =0.1 µF

AV = –1 V/V

VO+

V(rms)

Figure 43

– Output Noise Voltage –µVn

f – Frequency – Hz

OUTPUT NOISE VOLTAGE

FREQUENCY

20 1 k 10 k

100

20 k100

VDD = 5 V

BW = 22 Hz to 22 kHz

RL = 32 Ω

CB =0.1 µF

AV = –1 V/V

VO BTL

VO+

V(rms)

Figure 44

PO – Output Power – mW

POWER DISSIPATION

OUTPUT POWER

200 4000

180

150

120

300

PD– Power Dissipation – mW

210

240

270

VDD = 3.3 V

RL = 8 Ω

BTL

100 300

Figure 45

PO – Output Power – mW

POWER DISSIPATION

OUTPUT POWER

60 1200

VDD = 3.3 V

PD– Power Dissipation – mW

RL = 8 Ω

RL = 32 Ω

30 90

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 46

PO – Output Power – mW

POWER DISSIPATION

OUTPUT POWER

200 600400 8000 1000 1200

VDD = 5 V

RL = 8 Ω

BTL

400

320

240

160

720

PD– Power Dissipation – mW

480

560

640

Figure 47

PO – Output Power – mW

POWER DISSIPATION

OUTPUT POWER

50 150100 2000 250 300

VDD = 5 V

100

180

PD– Power Dissipation – mW

120

140

160 RL = 8 Ω

RL = 32 Ω

APPLICATION INFORMATION

bridge-tied load versus single-ended mode

Figure 48 shows a linear audio power amplifier (APA) in a BTL configuration. The TPA311 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 × VO(PP) into the power equation, where voltage is

squared, yields 4× the output power from the same supply rail and load impedance (see equation 1).

Power

V(rms)2

RL(1)

V(rms)

VO(PP)

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

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APPLICATION INFORMATION

bridge-tied load versus single-ended mode (continued)

RL2x VO(PP)

VO(PP)

–VO(PP)

VDD

Figure 48. Bridge-Tied Load Configuration

In typical portable handheld equipment, a sound channel operating at 3.3 V and using bridging raises the power

into an 8-Ω speaker from a single-ended (SE, ground reference) limit of 62.5 mW to 250 mW . In terms of 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 49. 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), tend to be expensive, heavy, and occupy valuable PCB area. These

capacitors also 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.

RLCC(2)

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.

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

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APPLICATION INFORMATION

bridge-tied load versus single-ended mode (continued)

CCVO(PP)

VO(PP)

VDD

–3 dB

Figure 49. 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 the SE

configuration. Internal dissipation versus output power is discussed further in the

thermal considerations

section.

BTL amplifier efficiency

Linear amplifiers are notoriously 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 VDD.

The internal voltage drop multiplied by the RMS value of the supply current, IDDrms, determines the internal

power dissipation of the amplifier.

An easy-to-use equation to calculate efficiency starts out as 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 50).

V(LRMS)

VOIDD

IDD(RMS)

Figure 50. Voltage and Current Waveforms for BTL Amplifiers

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

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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.

IDDrms

2VP

PSUP

VDD IDDrms

VDD 2VP

Efficiency

PSUP

Efficiency of a BTL Configuration

2VDD

PLRL

2VDD

(3)

Where:

(4)

VLrms2

Vp2

2RL

VLrms

Table 1 employs equation 4 to calculate efficiencies for three different 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) EFFICIENCY

(%)

PEAK-TO-PEAK

VOLTAGE

(V)

INTERNAL

DISSIPATION

(W)

0.125 33.6 1.41 0.26

0.25 47.6 2.00 0.29

0.375 58.3 2.45†0.28

†High-peak voltage values cause the THD to increase.

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, VDD is in the denominator. This indicates

that as VDD goes down, efficiency goes up.

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

application schematic

Figure 51 is a schematic diagram of a typical handheld audio application circuit, configured for a gain of

–10 V/V.

Audio

Input

Bias

Control

VDD

VO+

VDD

BYPASS

SE/BTL

VDD/2

0.47 µF

10 kΩ

1 µF

2.2 µF

50 kΩ

SHUTDOWN

VO–8

GND

From System Control

5 pF

330 µF

1 kΩ

100 kΩ

VDD 100 kΩ

–

0.1 µF

Figure 51. TPA311 Application Circuit

The following sections discuss the selection of the components used in Figure 51.

component selection

gain setting resistors, RF and RI

The gain for each audio input of the TP A31 1 is set by resistors RF and RI according to equation 5 for BTL mode.

(5)

BTL Gain

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 TPA311 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 RF 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.

(6)

Effective Impedance

RFRI

)

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

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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 RF above 50 kΩ the amplifier tends to become unstable due

to a pole formed from RF and the inherent input capacitance of the MOS input structure. For this reason, a small

compensation capacitor , CF, of approximately 5 pF should be placed in parallel with RF when RF is greater than

50 kΩ. This, in effect, creates a low pass filter network with the cutoff frequency defined in equation 7.

(7)

fc(lowpass)

RFCF

–3 dB

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

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 RI form a high-pass filter with the corner frequency

determined in equation 8.

(8)

fc(highpass)

RICI

–3 dB

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

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

Equation 8 is reconfigured as equation 9.

(9)

RIfc

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

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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 (RI, CI) and

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

that reduces useful headroom, especially in high gain applications. For this reason a low-leakage tantalum or

ceramic capacitor is the best choice. When polarized capacitors are used, the positive side of the capacitor

should face the amplifier input in most applications as the dc level there is held at VDD/2, which is likely higher

than the source dc level. It is important to confirm the capacitor polarity in the application.

power supply decoupling, CS

The TPA311 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 VDD lead, 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.

midrail bypass capacitor, CB

The midrail bypass capacitor , CB, is the most critical capacitor and serves several important functions. During

start-up or recovery from shutdown mode, CB determines the rate at which the amplifier starts up. The second

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, which insures the input capacitor is fully

charged before the bypass capacitor is fuly charged and the amplifier starts up.

(10)

250 kΩ

Ǔv

)

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: 18.2 ≤ 35.5 which satisfies the rule. Bypass capacitor , CB, values of 0.1 µF

to 2.2 µF ceramic or tantalum low-ESR capacitors are recommended for the best THD and noise performance.

single-ended operation

In SE mode (see Figure 51), the load is driven from the primary amplifier output (VO+, terminal 5).

In SE mode the gain is set by the RF and RI resistors and is shown in equation 11. Since the inverting amplifier

is not used to mirror the voltage swing on the load, the factor of 2, from equation 5, is not included.

(11)

SE Gain

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

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APPLICATION INFORMATION

single-ended operation (continued)

The output coupling capacitor required in single-supply SE mode also places additional constraints on the

selection of other components in the amplifier circuit. The rules described earlier still hold with the addition of

the following relationship:

(12)

250 kΩ

Ǔv

)

RLCC

As an example, consider a circuit where CB is 0.2.2 µF, CI is 0.47 µF, CC is 330 µF, RF is 50 kΩRL is 32 Ω, and

RI is 10 kΩ. Inserting these values into the equation 12 we get:

18.2

35.5

94.7 which satisfies the rule.

output coupling capacitor, CC

In the typical single-supply SE configuration, an output coupling capacitor (CC) is required to block the dc bias

at the output of the amplifier, thus preventing dc currents in the load. As with the input coupling capacitor, the

output coupling capacitor and impedance of the load form a high-pass filter governed by equation 13.

(13)

fc(high pass)

RLCC

–3 dB

The main disadvantage, from a performance standpoint, is that the typically small load impedances drive the

low-frequency corner higher degrading the bass response. Large values of CC are required to pass low

frequencies into the load. Consider the example where a CC of 330 µF is chosen and loads vary from 8 Ω,

32 Ω, to 47 kΩ. Table 2 summarizes the frequency response characteristics of each configuration.

Table 2. Common Load Impedances vs Low Frequency Output Characteristics in SE Mode

RLCCLOWEST FREQUENCY

8 Ω330 µF60 Hz

32 Ω330 µF15 Hz

47,000 Ω330 µF0.01 Hz

As T able 2 indicates an 8-Ω load is adequate, earphone response is good, and drive into line level inputs (a home

stereo for example) is exceptional.

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

SE/BTL operation

The ability of the TPA311 to easily switch between BTL and SE modes is one of its most important cost saving

features. This feature eliminates the requirement for an additional earphone amplifier in applications where

internal speakers are driven in BTL mode but external earphone or speaker must be accommodated. Internal

to the TPA311, two separate amplifiers drive VO+ and VO–. The SE/BTL input (terminal 3) controls the operation

of the follower amplifier that drives VO– (terminal 8). When SE/BTL is held low, the amplifier is on and the TPA311

is in the BTL mode. When SE/BTL is held high, the VO– amplifier is in a high output impedance state, which

configures the TPA311 as an SE driver from VO+ (terminal 5). IDD is reduced by approximately one-half in SE

mode. Control of the SE/BTL input can be from a logic-level TTL source or, more typically , from a resistor divider

network as shown in Figure 52.

Bias

Control

VO+

BYPASS

SE/BTL

SHUTDOWN

VO–8

GND

330 µF

1 kΩ

100 kΩ

VDD 100 kΩ

–

0.1 µF

Figure 52. TPA311 Resistor Divider Network Circuit

Using a readily available 1/8-in. (3.5 mm) mono earphone jack, the control switch is closed when no plug is

inserted. When closed the 100-kΩ/1-kΩ divider pulls the SE/BTL input low. When a plug is inserted, the 1-kΩ

resistor is disconnected and the SE/BTL input is pulled high. When the input goes high, the VO– amplifier is

shutdown causing the BTL speaker to mute (virtually open-circuits the speaker). The VO+ amplifier then drives

through the output capacitor (CC) into the earphone jack.

using low-ESR capacitors

Low-ESR capacitors are recommended throughout this application. 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.

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

28 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

5-V versus 3.3-V operation

The TPA311 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 TPA311 can produce a maximum

voltage swing of VDD – 1 V. This means, for 3.3-V operation, clipping starts to occur when VO(PP) = 2.3 V as

opposed to VO(PP) = 4 V at 5 V. The reduced voltage swing subsequently reduces maximum output power into

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 for a given output-power level of operation from 5-V supplies.

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 A311 data sheet, one can see that when the TPA311

is operating from a 5-V supply into a 8-Ω speaker that 350 mW peaks are available. Converting watts to dB:

PdB

10Log

Pref

10Log

350 mW

–4.6 dB

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

–4.6 dB

15 dB

19.6 dB (15 dB headroom)

–4.6 dB

12 dB

16.6 dB (12 dB headroom)

–4.6 dB

9dB

13.6 dB (9 dB headroom)

–4.6 dB

6dB

10.6 dB (6 dB headroom)

–4.6 dB

3dB

7.6 dB (3 dB headroom)

Converting dB back into watts:

10PdB

Pref

11 mW (15 dB headroom)

22 mW (12 dB headroom)

44 mW (9 dB headroom)

88 mW (6 dB headroom)

175 mW (3 dB headroom)

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

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 350 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 A311

and maximum ambient temperatures is shown in Table 3.

Table 3. TPA311 Power Rating, 5-V, 8-Ω, BTL

PEAK OUTPUT POWER

(mW)

AVERAGE OUTPUT

POWER

DISSIPATION MAXIMUM AMBIENT

TEMPERATURE

(mW)

POWER

(mW) 0 CFM SOIC 0 CFM DGN

350 350 mW 600 46°C114°C

350 175 mW (3 dB) 500 64°C 120°C

350 88 mW (6 dB) 380 85°C 125°C

350 44 mW (9 dB) 300 98°C 125°C

350 22 mW (12 dB) 200 115°C 125°C

350 11 mW (15 dB) 180 119°C 125°C

Table 3 shows that the TPA311 can be used to its full 350-mW rating without any heat sinking in still air up to

46°C.

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

30 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

MECHANICAL DATA

D (R-PDSO-G**) PLASTIC SMALL-OUTLINE PACKAGE

14 PINS SHOWN

4040047/D 10/96

0.228 (5,80)

0.244 (6,20)

0.069 (1,75) MAX 0.010 (0,25)

0.004 (0,10)

0.014 (0,35)

0.020 (0,51)

0.157 (4,00)

0.150 (3,81)

0.044 (1,12)

0.016 (0,40)

Seating Plane

0.010 (0,25)

PINS **

0.008 (0,20) NOM

A MIN

A MAX

DIM

Gage Plane

0.189

(4,80)

(5,00)

0.197

(8,55)

(8,75)

0.337

0.344

(9,80)

0.394

(10,00)

0.386

0.004 (0,10)

0.010 (0,25)

0.050 (1,27)

0°–8°

NOTES: A. All linear dimensions are in inches (millimeters).

B. This drawing is subject to change without notice.

C. Body dimensions do not include mold flash or protrusion, not to exceed 0.006 (0,15).

D. Falls within JEDEC MS-012

TPA311

350-mW MONO AUDIO POWER AMPLIFIER

SLOS207B – JANUARY 1998 – REVISED MARCH 2000

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

MECHANICAL DATA

DGN (S-PDSO-G8) PowerPAD PLASTIC SMALL-OUTLINE PACKAGE

0,69

0,41

0,25

Thermal Pad

(See Note D)

0,15 NOM

Gage Plane

4073271/A 04/98

4,98

0,25

3,05 4,78

2,95

3,05

2,95

0,38

0,15

0,05

1,07 MAX

Seating Plane

0,10

0,65 M

0,25

0°–6°

NOTES: A. All linear dimensions are in millimeters.

B. This drawing is subject to change without notice.

C. Body dimensions include mold flash or protrusions.

D. The package thermal performance may be enhanced by attaching an external heat sink to the thermal pad.

This pad is electrically and thermally connected to the backside of the die and possibly selected leads.

E. Falls within JEDEC MO-187

PowerPAD is a trademark of Texas Instruments.

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pertaining to warranty, patent infringement, and limitation of liability.

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accordance with TI’s standard warranty. Testing and other quality control techniques are utilized to the extent

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