TPA4860EVM - Texas Instruments

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

1

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

D

1-W BTL Output (5 V, 0.2 % THD+N)

D

3.3-V and 5-V Operation

D

No Output Coupling Capacitors Required

D

Shutdown Control (IDD = 0.6 µA)

D

Headphone Interface Logic

D

Uncompensated Gains of 2 to 20 (BTL

Mode)

D

Surface-Mount Packaging

D

Thermal and Short-Circuit Protection

D

High Power Supply Rejection

(56-dB at 1 kHz)

D

LM4860 Drop-In Compatible

description

The TP A4860 is a bridge-tied load (BTL) audio power amplifier capable of delivering 1 W of continuous average

power into an 8-Ω load at 0.4 % THD+N from a 5-V power supply in voiceband frequencies (f < 5 kHz). A BTL

configuration eliminates the need for external coupling capacitors on the output in most applications. Gain is

externally configured by means of two resistors and does not require compensation for settings of 2 to 20.

Features of this amplifier are a shutdown function for power-sensitive applications as well as headphone

interface logic that mutes the output when the speaker drive is not required. Internal thermal and short-circuit

protection increases device reliability. It also includes headphone interface logic circuitry to facilitate headphone

applications. The amplifier is available in a 16-pin SOIC surface-mount package that reduces board space and

facilitates automated assembly.

typical application circuit

Audio

Input

Bias

Control

VDD

1 W

12

10

15

1, 4, 8, 9, 16

VO1

VO2

VDD

2

3

7

6

5

14

13

11 GAIN

IN+

IN–

BYPASS

HP-IN1

HP-IN2

HP-SENSE

SHUTDOWN

VDD/2

CI

RI

RF

VDD

RPU

Headphone

Plug

NC

CB

CS

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.

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

GND

SHUTDOWN

HP-SENSE

GND

BYPASS

HP-IN1

HP-IN2

GND

VO2

IN+

IN–

VDD

GAIN

VO1

GND

D PACKAGE

(TOP VIEW)

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.

Copyright  2000, Texas Instruments Incorporated

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

2POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

AVAILABLE OPTIONS

PACKAGED DEVICE

TASMALL OUTLINE

(D)

–40°C to 85°C TPA4860D

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 –40°C to 85°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

D1250 mW 10 mW/°C800 mW 650 mW

recommended operating conditions

MIN MAX UNIT

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Supply voltage, VDD

ÁÁÁ

2.7

ÁÁÁ

5.5

ÁÁÁ

V

ÁÁÁÁÁÁÁÁÁÁ

Common mode in

p

ut voltage VIC

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

VDD = 3.3 V

ÁÁÁ

1.25

ÁÁÁ

2.7

ÁÁÁ

V

ÁÁÁÁÁÁÁÁÁÁ

Common

-

mode

inp

u

t

v

oltage

,

V

IC

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

VDD = 5 V

ÁÁÁ

1.25

ÁÁÁ

4.5

ÁÁÁ

V

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Operating free-air temperature, TA

ÁÁÁ

–40

ÁÁÁ

85

ÁÁÁ

°C

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

3

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

electrical characteristics at specified free-air temperature range, VDD = 3.3 V (unless otherwise

noted)

PARAMETER

TEST CONDITIONS

TPA4860

UNIT

PARAMETER

TEST

CONDITIONS

MIN TYP MAX

UNIT

ÁÁÁ

VOO

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Output offset voltage (measured dif ferentially)

ÁÁÁÁÁÁ

See Note 1

ÁÁÁ

5

ÁÁÁ

20

ÁÁÁ

mV

ÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Supply ripple rejection ratio

ÁÁÁÁÁÁ

VDD = 3.2 V to 3.4 V

ÁÁÁ

75

ÁÁÁ

dB

ÁÁÁ

IDD

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Quiescent current

ÁÁÁÁÁÁ

ÁÁÁ

2.5

ÁÁÁ

mA

ÁÁÁ

IDD(M)

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Quiescent current, mute mode

ÁÁÁÁÁÁ

ÁÁÁ

750

ÁÁÁ

µA

ÁÁÁ

IDD(SD)

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Quiescent current, shutdown mode

ÁÁÁÁÁÁ

ÁÁÁ

0.6

ÁÁÁ

µA

ÁÁÁ

VIH

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

High-level input voltage (HP-IN)

ÁÁÁÁÁÁ

ÁÁÁ

1.7

ÁÁÁ

V

ÁÁÁ

VIL

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Low-level input voltage (HP-IN)

ÁÁÁÁÁÁ

ÁÁÁ

1.7

ÁÁÁ

V

ÁÁÁ

VOH

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

High-level output voltage (HP-SENSE)

ÁÁÁÁÁÁ

IO = 100 µA

ÁÁÁ

2.5

ÁÁÁ

2.8

ÁÁÁ

V

ÁÁÁ

VOL

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Low-level output voltage (HP-SENSE)

ÁÁÁÁÁÁ

IO = –100 µA

ÁÁÁ

0.2

ÁÁÁ

0.8

ÁÁÁ

V

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

TPA4860

UNIT

PARAMETER

TEST

CONDITIONS

MIN TYP MAX

UNIT

ÁÁÁ

Á

ÁÁÁ

PO

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Out

p

ut

p

ower see Note 2

ÁÁÁÁÁ

Á

ÁÁÁ

Á

ÁÁÁÁÁ

THD = 0.2%,

AV = 2

ÁÁÁÁ

Á

ÁÁ

Á

ÁÁÁÁ

f = 1 kHz,

ÁÁÁ

Á

ÁÁÁ

Á

ÁÁÁ

350

ÁÁÁ

Á

ÁÁÁ

Á

ÁÁÁ

mW

ÁÁÁ

Á

ÁÁÁ

P

O

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

O

u

tp

u

t

po

w

er

,

see

Note

2

ÁÁÁÁÁ

Á

ÁÁÁ

Á

ÁÁÁÁÁ

THD = 2%,

AV = 2

ÁÁÁÁ

Á

ÁÁ

Á

ÁÁÁÁ

f = 1 kHz,

ÁÁÁ

Á

ÁÁÁ

Á

ÁÁÁ

500

ÁÁÁ

Á

ÁÁÁ

Á

ÁÁÁ

mW

ÁÁÁ

BOM

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Maximum output power bandwidth

ÁÁÁÁÁ

Gain = 10,

ÁÁÁÁ

THD = 2%

ÁÁÁ

20

ÁÁÁ

kHz

ÁÁÁ

B1

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Unity-gain bandwidth

ÁÁÁÁÁÁÁÁ

Open Loop

ÁÁÁ

1.5

ÁÁÁ

MHz

ÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁ

Su

pp

ly ri

pp

le rejection ratio

ÁÁÁÁÁ

BTL

ÁÁÁÁÁÁÁÁ

f = 1 kHz

ÁÁÁ

56

ÁÁÁ

dB

ÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁ

S

u

ppl

y

ripple

rejection

ratio

ÁÁÁÁÁ

SE

ÁÁÁÁÁÁÁÁ

f = 1 kHz

ÁÁÁ

30

ÁÁÁ

dB

ÁÁÁ

Vn

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Noise output voltage, see Note 3

ÁÁÁÁÁÁÁÁ

Gain = 2

ÁÁÁ

20

ÁÁÁ

µV

NOTES: 2. Output power is measured at the output terminals of the device.

3. Noise voltage is measured in a bandwidth of 20 Hz to 20 kHz.

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

4POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

electrical characteristics at specified free-air temperature range, VDD = 5 V (unless otherwise

noted)

PARAMETER

TEST CONDITIONS

TPA4860

UNIT

PARAMETER

TEST

CONDITIONS

MIN TYP MAX

UNIT

ÁÁÁÁ

VOO

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Output offset voltage

ÁÁÁÁÁÁÁ

See Note 1

ÁÁÁ

5

ÁÁÁ

20

ÁÁÁ

mV

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Supply ripple rejection ratio

ÁÁÁÁÁÁÁ

VDD = 4.9 V to 5.1 V

ÁÁÁ

70

ÁÁÁ

dB

ÁÁÁÁ

IDD

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Supply current

ÁÁÁÁÁÁÁ

ÁÁÁ

3.5

ÁÁÁ

mA

ÁÁÁÁ

IDD(M)

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Supply current, mute

ÁÁÁÁÁÁÁ

ÁÁÁ

750

ÁÁÁ

µA

ÁÁÁÁ

IDD(SD)

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Supply current, shutdown

ÁÁÁÁÁÁÁ

ÁÁÁ

0.6

ÁÁÁ

µA

ÁÁÁÁ

VIH

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

High-level input voltage (HP-IN)

ÁÁÁÁÁÁÁ

ÁÁÁ

2.5

ÁÁÁ

V

ÁÁÁÁ

VIL

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Low-level input voltage (HP-IN)

ÁÁÁÁÁÁÁ

ÁÁÁ

2.5

ÁÁÁ

V

ÁÁÁÁ

VOH

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

High-level output voltage (HP-SENSE)

ÁÁÁÁÁÁÁ

IO = 500 µA

ÁÁÁ

2.5

ÁÁÁ

2.8

ÁÁÁ

V

ÁÁÁÁ

VOL

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Low-level output voltage (HP-SENSE)

ÁÁÁÁÁÁÁ

IO = –500 µA

ÁÁÁ

0.2

ÁÁÁ

0.8

ÁÁÁ

V

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

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

PARAMETER

TEST CONDITIONS

TPA4860

UNIT

PARAMETER

TEST

CONDITIONS

MIN TYP MAX

UNIT

ÁÁÁÁ

Á

ÁÁ

Á

ÁÁÁÁ

PO

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Out

p

ut

p

ower see Note 2

ÁÁÁÁ

Á

ÁÁ

Á

ÁÁÁÁ

THD = 0.2%,

AV = 2

ÁÁÁÁÁ

Á

ÁÁÁ

Á

ÁÁÁÁÁ

f = 1 kHz,

ÁÁÁ

Á

ÁÁÁ

Á

ÁÁÁ

1000

ÁÁÁ

Á

ÁÁÁ

Á

ÁÁÁ

mW

ÁÁÁÁ

Á

ÁÁ

Á

ÁÁÁÁ

P

O

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

O

u

tp

u

t

po

w

er

,

see

Note

2

ÁÁÁÁ

Á

ÁÁ

Á

ÁÁÁÁ

THD = 2%,

AV = 2

ÁÁÁÁÁ

Á

ÁÁÁ

Á

ÁÁÁÁÁ

f = 1 kHz,

ÁÁÁ

Á

ÁÁÁ

Á

ÁÁÁ

1100

ÁÁÁ

Á

ÁÁÁ

Á

ÁÁÁ

mW

ÁÁÁÁ

BOM

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Maximum output power bandwidth

ÁÁÁÁ

Gain = 10,

ÁÁÁÁÁ

THD = 2%

ÁÁÁ

20

ÁÁÁ

kHz

ÁÁÁÁ

B1

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Unity-gain bandwidth

ÁÁÁÁÁÁÁÁ

Open Loop

ÁÁÁ

1.5

ÁÁÁ

MHz

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁ

Su

pp

ly ri

pp

le rejection ratio

ÁÁÁÁÁ

BTL

ÁÁÁÁÁÁÁÁ

f = 1 kHz

ÁÁÁ

56

ÁÁÁ

dB

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁÁ

S

u

ppl

y

ripple

rejection

ratio

ÁÁÁÁÁ

SE

ÁÁÁÁÁÁÁÁ

f = 1 kHz

ÁÁÁ

30

ÁÁÁ

dB

ÁÁÁÁ

Vn

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

Noise output voltage, see Note 3

ÁÁÁÁÁÁÁÁ

Gain = 2

ÁÁÁ

20

ÁÁÁ

µV

NOTES: 2. Output power is measured at the output terminals of the device.

3. Noise voltage is measured in a bandwidth of 20 Hz to 20 kHz.

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

5

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Table of Graphs

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ

ÁÁÁÁ

FIGURE

ÁÁÁÁ

VOO

ÁÁÁÁÁÁÁÁÁÁÁ

Output of fset voltage

ÁÁÁÁÁÁÁ

Distribution

ÁÁÁÁ

1,2

ÁÁÁÁ

IDD

ÁÁÁÁÁÁÁÁÁÁÁ

Supply current distribution

ÁÁÁÁÁÁÁ

vs Free-air temperature

ÁÁÁÁ

3,4

ÁÁÁÁ

Á

ÁÁ

Á

ÁÁÁÁ

THD+N

ÁÁÁÁÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁÁÁÁÁ

Total harmonic distortion plus noise

ÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁ

vs Frequency

ÁÁÁÁ

Á

ÁÁ

Á

ÁÁÁÁ

5,6,7,8,9,

10,11,15,

16,17,18

ÁÁÁÁ

Á

ÁÁ

Á

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁ

Á

ÁÁÁÁÁ

Á

ÁÁÁÁÁÁÁ

vs Output power

ÁÁÁÁ

Á

ÁÁ

Á

ÁÁÁÁ

12,13,14,

19,20,21

ÁÁÁÁ

IDD

ÁÁÁÁÁÁÁÁÁÁÁ

Supply current

ÁÁÁÁÁÁÁ

vs Supply voltage

ÁÁÁÁ

22

ÁÁÁÁ

Vn

ÁÁÁÁÁÁÁÁÁÁÁ

Output noise voltage

ÁÁÁÁÁÁÁ

vs Frequency

ÁÁÁÁ

23,24

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁ

Maximum package power dissipation

ÁÁÁÁÁÁÁ

vs Free-air temperature

ÁÁÁÁ

25

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁ

Power dissipation

ÁÁÁÁÁÁÁ

vs Output power

ÁÁÁÁ

26,27

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁ

Maximum output power

ÁÁÁÁÁÁÁ

vs Free-air temperature

ÁÁÁÁ

28

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁ

Out

p

ut

p

ower

ÁÁÁÁÁÁÁ

vs Load Resistance

ÁÁÁÁ

29

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁ

O

u

tp

u

t

po

w

er

ÁÁÁÁÁÁÁ

vs Supply Voltage

ÁÁÁÁ

30

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁ

Open loop frequency response

ÁÁÁÁÁÁÁ

vs Frequency

ÁÁÁÁ

31

ÁÁÁÁ

ÁÁÁÁÁÁÁÁÁÁÁ

Supply ripple rejection ratio

ÁÁÁÁÁÁÁ

vs Frequency

ÁÁÁÁ

32,33

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

6POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 1

Number of Amplifiers

DISTRIBUTION OF TPA4860

OUTPUT OFFSET VOLTAGE

20

10

0

VOO – Output Offset Voltage – mV

25

15

5

VCC = 5 V

–3–2–101234567

Figure 2

Number of Amplifiers

DISTRIBUTION OF TPA4860

OUTPUT OFFSET VOLTAGE

20

10

0

VOO – Output Offset Voltage – mV

25

15

5

–3 –2 –1 0 1 2 3 4 5 6 7

VCC = 3.3 V

Figure 3

– Supply Current – mA

SUPPLY CURRENT DISTRIBUTION

vs

FREE-AIR TEMPERATURE

3.5

2

1

0

TA – Free-Air Temperature – °C

–20 25

2.5

1.5

0.5

VCC = 5 V

IDD

3

85

4.5

4

Typical

Figure 4

– Supply Current – mA

SUPPLY CURRENT DISTRIBUTION

vs

FREE-AIR TEMPERATURE

3.5

2

1

0

TA – Free-Air Temperature – °C

–20 25

2.5

1.5

0.5

VCC = 3.3 V

IDD

3

85

Typical

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

7

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 5

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

FREQUENCY

20

10

1

0.1

0.01 100 1 k 10 k 20 k

f – Frequency – Hz

VDD = 5 V

PO = 1 W

AV = –2 V/V

RL = 8 Ω

CB = 0.1 µF

CB = 1 µF

THD+N – Total Harmonic Distortion Plus Noise – %

Figure 6

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

FREQUENCY

20

10

1

0.1

0.01 100 1 k 10 k 20 k

f – Frequency – Hz

VDD = 5 V

PO = 1 W

AV = –10 V/V

RL = 8 Ω

CB = 0.1 µF

CB = 1 µF

THD+N – Total Harmonic Distortion Plus Noise – %

Figure 7

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

FREQUENCY

20

10

1

0.1

0.01 100 1 k 10 k 20 k

f – Frequency – Hz

VDD = 5 V

PO = 1 W

AV = –20 V/V

RL = 8 Ω

CB = 0.1 µF

CB = 1 µF

THD+N – Total Harmonic Distortion Plus Noise – %

Figure 8

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

FREQUENCY

20

10

1

0.1

0.01 100 1 k 10 k 20 k

f – Frequency – Hz

VDD = 5 V

PO = 0.5 W

AV = –2 V/V

RL = 8 Ω

CB = 0.1 µF

CB = 1 µF

THD+N – Total Harmonic Distortion Plus Noise – %

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

8POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 9

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

FREQUENCY

20

10

1

0.1

0.01 100 1 k 10 k 20 k

f – Frequency – Hz

VDD = 5 V

PO = 0.5 W

AV = –10 V/V

RL = 8 Ω

CB = 0.1 µF

CB = 1 µF

THD+N – Total Harmonic Distortion Plus Noise – %

Figure 10

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

FREQUENCY

20

10

1

0.1

0.01 100 1 k 10 k 20 k

f – Frequency – Hz

THD+N – Total Harmonic Distortion Plus Noise – %

VDD = 5 V

PO = 0.5 W

AV = –20 V/V

RL = 8 Ω

CB = 0.1 µF

CB = 1 µF

Figure 11

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

FREQUENCY

20

10

1

0.1

0.01 100 1 k 10 k 20 k

f – Frequency – Hz

THD+N – Total Harmonic Distortion Plus Noise – %

VDD = 5 V

AV = –10 V/V

Single Ended

RL = 8 Ω

PO = 250 mW

RL = 32 Ω

PO = 60 mW

Figure 12

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

OUTPUT POWER

0.02

10

1

0.1

0.01 0.1 1

PO – Output Power – W

THD+N – Total Harmonic Distortion Plus Noise – %

VDD = 5 V

AV = –2 V/V

RL = 8 Ω

f = 20 Hz

CB = 0.1 µF

2

CB = 1 µF

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

9

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 13

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

OUTPUT POWER

0.02

10

1

0.1

0.01 0.1 1

PO – Output Power – W

THD+N – Total Harmonic Distortion Plus Noise – %

VDD = 5 V

AV = –2 V/V

RL = 8 Ω

f = 1 kHz

2

CB = 0.1 µF

Figure 14

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

OUTPUT POWER

0.02

10

1

0.1

0.01 0.1 1

PO – Output Power – W

THD+N – Total Harmonic Distortion Plus Noise – %

VDD = 5 V

AV = –2 V/V

RL = 8 Ω

f = 20 kHz

CB = 0.1 µF

2

Figure 15

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

FREQUENCY

20

10

1

0.1

0.01 100 1 k 10 k 20 k

f – Frequency – Hz

THD+N – Total Harmonic Distortion Plus Noise – %

CB = 1 µF

VDD = 3.3 V

PO = 350 mW

RL = 8 Ω

AV = –2 V/V

CB = 0.1 µF

Figure 16

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

FREQUENCY

20

10

1

0.1

0.01 100 1 k 10 k 20 k

f – Frequency – Hz

THD+N – Total Harmonic Distortion Plus Noise – %

CB = 1 µF

VDD = 3.3 V

PO = 350 mW

RL = 8 Ω

AV = –10 V/V

CB = 0.1 µF

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

10 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 17

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

FREQUENCY

20

10

1

0.1

0.01 100 1 k 10 k 20 k

f – Frequency – Hz

THD+N – Total Harmonic Distortion Plus Noise – %

VDD = 3.3 V

PO = 350 mW

RL = 8 Ω

AV = –20 V/V

CB = 1 µF

CB = 0.1 µF

Figure 18

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

FREQUENCY

20

10

1

0.1

0.01 100 1 k 10 k 20 k

f – Frequency – Hz

THD+N – Total Harmonic Distortion Plus Noise – %

VDD = 3.3 V

AV = –10 V/V

Single Ended

RL = 32 Ω

PO = 60 mW

RL = 8 Ω

PO = 250 mW

Figure 19

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

OUTPUT POWER

0.02

10

1

0.1

0.01 0.1 1

PO – Output Power – W

THD+N – Total Harmonic Distortion Plus Noise – %

VDD = 3.3 V

AV = –2 V/V

RL = 8 Ω

f = 20 Hz

CB = 0.1 µF

2

CB = 1.0 µF

Figure 20

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

OUTPUT POWER

0.02

10

1

0.1

0.01 0.1 1

PO – Output Power – W

THD+N – Total Harmonic Distortion Plus Noise – %

VDD = 3.3 V

AV = –2 V/V

RL = 8 Ω

f = 1 kHz

CB = 0.1 µF

2

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

11

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 21

TOTAL HARMONIC DISTORTION PLUS NOISE

vs

OUTPUT POWER

20 m

10

1

0.1

0.01 0.1 1

PO – Output Power – W

THD+N – Total Harmonic Distortion Plus Noise – %

VDD = 3.3 V

AV = –2 V/V

RL = 8 Ω

f = 20 kHz

CB = 0.1 µF

2

Figure 22

– Supplu Current – mAIDD

SUPPLY CURRENT

vs

SUPPLY VOLTAGE

2.5

5

2

1

03 3.5

VDD – Supply Voltage – V

4 4.5 5 5.5

4

3

TA = 0°C

TA = 85°C

TA = 25°C

TA = –20°C

Figure 23

OUTPUT NOISE VOLTAGE

vs

FREQUENCY

20

103

102

101

1100 1 k 10 k 20 k

f – Frequency – Hz

VCC = 5 V

V01 +V02

V01

V02

– Output Noise Voltage – VnVµ

Figure 24

OUTPUT NOISE VOLTAGE

vs

FREQUENCY

20

103

102

101

1100 1 k 10 k 20 k

f – Frequency – Hz

VCC = 3.3 V

V02

V01

V01 +V02

– Output Noise Voltage – VnVµ

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

12 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 25

Maximum Package Power Dissipation – W

MAXIMUM PACKAGE POWER DISSIPATION

vs

FREE-AIR TEMPERATURE

–25

1.5

1

0.5

00 75 175

TA – Free-Air Temperature – °C

25 50 100 125 150

1.25

0.75

0.25

Figure 26

Power Dissipation – W

POWER DISSIPATION

vs

OUTPUT POWER

1.5

1

0.5

00 0.75 1.75

PO – Output Power – W

0.25 0.5 1 1.25 1.5

VDD = 5 V

RL = 4 Ω

RL = 8 Ω

RL = 16 Ω

Figure 27

POWER DISSIPATION

vs

OUTPUT POWER

1

0.5

0.25

00 0.75

PO – Output Power – W

0.25 0.5

VDD = 3.3 V

RL = 4 Ω

RL = 8 Ω

RL = 16 Ω

0.75

Power Dissipation – W

Figure 28

160

40

20

00 0.25 1.500.5 0.75 1

RL = 16 Ω

– Free-Air Temperature –

PO – Maximum Output Power – W

1.25

RL = 8 Ω

RL = 4 Ω

C

°

TA

80

60

120

100

140

MAXIMUM OUTPUT POWER

vs

FREE-AIR TEMPERATURE

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

13

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

Figure 29

– Power Output – W

OUTPUT POWER

vs

LOAD RESISTANCE

4

1.4

0.8

0.4

0820 36

Load Resistance – Ω

12 16 24 28 32

1

0.6

0.2

VCC = 5 V

VCC = 3.3 V

PO

AV = –2 V/V

f = 1 kHz

CB = 0.1 µF

THD+n ≤ 1%

1.2

4840 44

Figure 30

– Power Output – W

OUTPUT POWER

vs

SUPPLY VOLTAGE

3

1.75

1

0.5

03.5 5

Supply Voltage – V

4 4.5 5.5

1.25

0.75

0.25

PO

1.5

AV = –2 V/V

f = 1 kHz

CB = 0.1 µF

THD+n ≤ 1%

2.5

2

RL = 8 Ω

RL = 4 Ω

RL = 16 Ω

Figure 31

G – Gain – dB

OPEN LOOP FREQUENCY RESPONSE

10

100

60

20

–20 100 100 k

f – Frequency – Hz

VDD = 5 V

RL = 8 Ω

CB = 0.1 µF

1 k 10 k 1 M 10 M

80

40

0

45°

–45°

–135°

–225°

0°

–90°

–180°

Phase

Gain

Phase

Figure 32

SUPPLY RIPPLE REJECTION RATIO

vs

FREQUENCY

100

0

–90

–100 1 k 10 k 20 k

f – Frequency – Hz

VDD = 5 V

RL = 8 Ω

Bridge Tied

Load

CB = 0.1 µF

CB = 1 µF

–80

–70

–60

–50

–40

–30

–20

–10

Supply Ripple Rejection Ratio – dB

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

14 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

TYPICAL CHARACTERISTICS

SUPPLY RIPPLE REJECTION RATIO

vs

FREQUENCY

100

0

–90

–100 1 k 10 k 20 k

f – Frequency – Hz

CB = 0.1 µF

CB = 1 µF

–80

–70

–60

–50

–40

–30

–20

–10 VDD = 5 V

RL = 8 Ω

Single Ended

Figure 33

Supply Ripple Rejection Ratio – dB

APPLICATION INFORMATION

bridged-tied load versus single-ended mode

Figure 34 shows a linear audio power amplifier (AP A) in a bridge tied load (BTL) configuration. A BTL amplifier

actually consists of two linear amplifiers driving both ends of the load. There are several potential benefits to

this differential drive configuration but initially let us 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 twice the voltage

into the power equation, where voltage is squared, yields 4 times the output power from the same supply rail

and load impedance (see equation 1).

Power

+

V(rms)2

RL(1)

V(rms)

+

VO(PP)

22

Ǹ

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

15

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

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

RL2x VO(PP)

VO(PP)

–VO(PP)

VDD

Figure 34. Bridge-Tied Load Configuration

In a typical computer sound channel operating at 5 V, bridging raises the power into a 8-Ω speaker from a

singled-ended (SE) limit of 250 mW to 1 W . 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 35. A coupling capacitor is required to block the dc offset voltage from reaching

the load. These capacitors can be quite large (approximately 40 µF to 1000 µF) so they tend to be expensive,

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.

fc

+

1

2

p

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.

RL

CCVO(PP)

VO(PP)

VDD

Figure 35. Single-Ended Configuration

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

16 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

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

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 times 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 36).

V(LRMS)

VOIDD

IDD(RMS)

Figure 36. Voltage and Current Waveforms for BTL Amplifiers

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 transistor 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.

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

17

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

VLrms

+

VP

2

Ǹ

IDDrms

+

2VP

p

RL

PSUP

+

VDD IDDrms

+

VDD 2VP

p

RL

Efficiency

+

PL

PSUP

Efficiency of a BTL Configuration

+

p

VP

2VDD

+

p

ǒ

PLRL

2

Ǔ

1

ń

2

2VDD

(3)

PL

+

VLrms2

RL

+

Vp2

2RL

Where:

(4)

NO TAG employs equation 4 to calculate efficiencies for four different output power levels. Note that 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. Note that 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. For a stereo 1-W audio system with 8-Ω loads and a 5-V supply,

the maximum draw on the power supply is almost 3.25 W.

Table 1. Efficiency vs Output Power in 5-V 8-Ω BTL Systems

OUTPUT POWER

(W) EFFICIENCY

(%)

PEAK-TO-PEAK

VOLTAGE

(V)

INTERNAL

DISSIPATION

(W)

0.25 31.4 2.00 0.55

0.50 44.4 2.83 0.62

1.00 62.8 4.00 0.59

1.25 70.2 4.47†0.53

†High peak voltages cause the THD to increase.

A final point to remember about linear amplifiers whether they are SE or BTL configured is how to manipulate

the terms in the efficiency equation to utmost advantage when possible. Note that in equation 4, VDD is in the

denominator. This indicates that as VDD goes down, efficiency goes up.

For example, if the 5-V supply is replaced with a 10-V supply (TPA4860 has a maximum recommended VDD

of 5.5 V) in the calculations of NO TAG then efficiency at 1 W would fall to 31% and internal power dissipation

would rise to 2.18 W from 0.59 W at 5 V. Then for a stereo 1-W system from a 10-V supply, the maximum draw

would be almost 6.5 W. Choose the correct supply voltage and speaker impedance for the application.

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

18 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

selection of components

Figure 37 is a schematic diagram of a typical notebook computer application circuit.

Audio

Input

Bias

Control

VDD = 5 V

1 W

Internal

Speaker

12

10

15

1, 4, 8, 9, 16

VO1

VO2

VDD

2

3

7

6

5

14

13

11 GAIN

IN+

IN–

BYPASS

HP-IN1

HP-IN2

HP-SENSE

SHUTDOWN

VDD/2

CI

RI

RF

VDD

RPU

Headphone

Plug

NC

CF50 kΩ50 kΩ

46 kΩ

CB

CS

Figure 37. TPA4860 Typical Notebook Computer Application Circuit

gain setting resistors, RF and RI

The gain for the TPA4860 is set by resistors RF and RI according to equation 5.

(5)

Gain

+

*

2

ǒ

RF

RI

Ǔ

BTL mode operation brings about the factor of 2 in the gain equation due to the inverting amplifier mirroring the

voltage swing across the load. Given that the TPA4860 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 startup 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

RF

)

RI

As an example, consider an input resistance of 10 kΩ and a feedback resistor of 50 kΩ. The gain of the amplifier

would be –10 and the effective impedance at the inverting terminal would be 8.3 kΩ, which is well within the

recommended range.

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

19

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

gain setting resistors, RF and RI (continued)

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 of approximately 5 pF should be placed in parallel with RF. This, in effect, creates a low

pass filter network with the cutoff frequency defined in equation 7.

(7)

fc(lowpass)

+

1

2

p

RFCF

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)

+

1

2

p

RICI

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)

CI

+

1

2

p

RIfc

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

that the source dc level. Note that it is important to confirm the capacitor polarity in the application.

power supply decoupling, CS

The TPA4860 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 power amplifier is recommended.

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

20 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

midrail bypass capacitor, CB

The midrail bypass capacitor, CB, serves several important functions. During start-up or recovery from

shutdown mode, CB determines the rate at which the amplifier starts up. This helps to push the start-up pop

noise into the subaudible range (so low it can not be heard). 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. The capacitor is fed from a 25-kΩ source inside the amplifier . To keep the start-up

pop as low as possible, the relationship shown in equation 10 should be maintained.

(10)

1

ǒ

CB

25 kΩ

Ǔv

1

ǒ

CIRI

Ǔ

As an example, consider a circuit where CB is 0.1 µF, CI is 0.22 µF and RI is 10 kΩ. Inserting these values into

the equation 9 we get: 400 ≤ 454 which satisfies the rule. Bypass capacitor, CB, values of 0.1 µF to 1 µF ceramic

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

single-ended operation

Figure 38 is a schematic diagram of the recommended SE configuration. In SE mode configurations, the load

should be driven from the primary amplifier output (OUT1, terminal 10).

Audio

Input

VDD = 5 V

250-mW

External

Speaker

12

10

15

VO1

VO2

VDD

5

14

13

11 GAIN

IN+

IN–

BYPASS

VDD/2

CI

RI

RF

CSE = 0.1 µF

RSE = 50 Ω

CC

CB

CS

Figure 38. Singled-Ended Mode

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 is not included.

(11)

Gain

+*

ǒ

RF

RI

Ǔ

The phase margin of the inverting amplifier into an open circuit is not adequate to ensure stability, so a

termination load should be connected to VO2. This consists of a 50-Ω resistor in series with a 0.1-µF capacitor

to ground. It is important to avoid oscillation of the inverting output to minimize noise and power dissipation.

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

21

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

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)

1

ǒ

CB

25 kΩ

Ǔv

1

ǒ

CIRI

ǓƠ

1

RLCC

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)

fchigh

+

1

2

p

RLCC

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

drives the low-frequency corner higher . Large values of C C are required to pass low frequencies into the load.

Consider the example where a CC of 68 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 Ω68 µF293 Hz

32 Ω68 µF73 Hz

47,000 Ω68 µF0.05 Hz

As Table 2 indicates, most of the bass response is attenuated into 8-Ω loads while headphone response is

adequate and drive into line level inputs (a home stereo for example) is very good.

headphone sense circuitry, Rpu

The TPA4860 is commonly used in systems where there is an internal speaker and a jack for driving external

loads (i.e., headphones). In these applications, it is usually desirable to mute the internal speaker(s) when the

external load is in use. The headphone inputs (HP-1, HP-2) and headphone output (HP-SENSE) of the TPA4860

were specifically designed for this purpose. Many standard headphone jacks are available with an internal

single-pole single-throw (SPST) switch that makes or breaks a circuit when the headphone plug is inserted.

Asserting either or both HP-1 and/or HP-2 high mutes the output stage of the amplifier and causes HP-SENSE

to go high. In battery-powered applications where power conservation is critical HP-SENSE can be connected

to the shutdown input as shown in Figure 39. This places the amplifier in a very low current state for maximum

power savings. Pullup resistors in the range from 1 kΩ to 10 kΩ are recommended for 5-V and 3.3-V operation.

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

22 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

Bias

Control

2

3

7

6HP-IN1

HP-IN2

HP-SENSE

SHUTDOWN

VDD

RPU

Headphone

Plug

NC

Figure 39. Schematic Diagram of Typical Headphone Sense Application

Table 3 details the logic for the mute function of the TPA4860.

Table 3. Truth Table for Headphone Sense and Shutdown Functions

INPUTS†OUTPUT AMPLIFIER

HP-1 HP-2 SHUTDOWN HP-SENSE STATE

Low Low Low Low Active

Low High Low High Mute

High Low Low High Mute

High High Low High Mute

X X High X Shutdown

†Inputs should never be left unconnected.

X = do not care

shutdown mode

The TPA4860 employs a shutdown mode of operation designed to reduce quiescent supply current, IDD(q), to

the absolute minimum level during periods of nonuse for battery-power conservation. For example, during

device sleep modes or when other audio-drive currents are used (i.e., headphone mode), the speaker drive is

not required. The SHUTDOWN input terminal should be held low during normal operation when the amplifier

is in use. Pulling SHUTDOWN high causes the outputs to mute and the amplifier to enter a low-current state,

IDD <1 µA. SHUTDOWN should never be left unconnected because amplifier operation would be unpredictable.

using low-ESR capacitors

Low-ESR capacitors are recommended throughout this applications section. A real 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.

thermal considerations

A prime consideration when designing an audio amplifier circuit is internal power dissipation in the device. The

curve in Figure 40 provides an easy way to determine what output power can be expected out of the TPA4860

for a given system ambient temperature in designs using 5-V supplies. This curve assumes no forced airflow

or additional heat sinking.

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

23

POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

APPLICATION INFORMATION

160

40

20

00 0.25 1.500.5 0.75 1

RL = 16 Ω

– Free-Air Temperature –

Maximum Output Power – W 1.25

RL = 8 Ω

RL = 4 Ω

C

°

TA

80

60

120

100

140

VDD = 5 V

Figure 40. Free-Air Temperature Versus Maximum Continuous Output Power

5-V versus 3.3-V operation

The TPA4860 was designed for operation over a supply range of 2.7 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 as far as supply bypassing, gain

setting, or stability. Supply current is slightly reduced from 3.5 mA (typical) to 2.5 mA (typical). The most

important consideration is that of output power. Each amplifier in TPA4860 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 when VO(PP) = 4 V while operating at 5 V . The reduced voltage swing subsequently reduces maximum output

power into an 8-Ω load to less than 0.33 W before distortion begins to become significant.

Operation at 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 than operation from 5-V supplies.

When the application demands less than 500 mW, 3.3-V operation should be strongly considered, especially

in battery-powered applications.

TPA4860

1-W MONO AUDIO POWER AMPLIFIER

SLOS164A – SEPTEMBER 1996 – REVISED MARCH 2000

24 POST OFFICE BOX 655303 • DALLAS, TEXAS 75265

MECHANICAL INFORMATION

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)

1

14

0.014 (0,35)

0.020 (0,51)

A

0.157 (4,00)

0.150 (3,81)

7

8

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

(8,55)

(8,75)

0.337

14

0.344

(9,80)

16

0.394

(10,00)

0.386

0.004 (0,10)

M

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

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