LM4664.pdf

March 2004

LM4664

Filterless High Efficiency 1.1W Switching Audio

Amplifier

General Description

The LM4664 is a fully integrated single-supply high efficiency

switching audio amplifier. It features an innovative modulator

that eliminates the LC output filter used with typical switching

amplifiers. Eliminating the output filter reduces parts count,

simplifies circuit design, and reduces board area. The

LM4664 processes analog inputs with a delta-sigma modu-

lation technique that lowers output noise and THD when

compared to conventional pulse width modulators.

The LM4664 is designed to meet the demands of mobile

phones and other portable communication devices. Operat-

ing on a single 3V supply, it is capable of driving 8

Key Specifications

j Efficiency at 3V, 100mW into 8

Ω

transducer 74% (typ)

j Efficiency at 3V, 425mW into 8

Ω

transducer 84% (typ)

j Efficiency at 5V, 1W into 8

Ω

transducer

86% (typ)

j Total quiescent power supply current

3.5mA (typ)

j Total shutdown power supply current

0.4µA (typ)

j Single supply range

2.7V to 5.5V

trans-

ducer loads at a continuous average output of 425mW with

less than 1%THD+N. Its flexible power supply requirements

allow operation from 2.7V to 5.5V.

The LM4664 has high efficiency with an 8 Ω transducer load

compared to a typical Class AB amplifier. With a 3V supply,

the IC’s efficiency for a 100mW power level is 74%, reaching

84% at 425mW output power.

The LM4664 features a low-power consumption shutdown

mode. Shutdown may be enabled by driving the Shutdown

pin to a logic low (GND).

The LM4664 has fixed selectable gain of either 6dB or 12dB.

The LM4664 has short circuit protection against a short from

the outputs to V DD , GND, or across the outputs.

Ω

Features

n No output filter required for inductive transducers

n Selectable gain of 6dB or 12dB

n Very fast turn on time: 7ms (typ)

n Minimum external components

n "Click and pop" suppression circuitry

n Micro-power shutdown mode

n Short circuit protection

n Available in space-saving micro SMD package

Applications

n Mobile phones

n PDAs

n Portable electronic devices

Typical Application

200960G5

FIGURE 1. Typical Audio Amplifier Application Circuit

Boomer ® is a registered trademark of National Semiconductor Corporation.

DS200960

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Connection Diagrams

9 Bump micro SMD Package

micro SMD Marking

200960K1

Top View

X— Date Code

T— Die Traceability

G — Boomer Family

E4– LM4664ITL

20096036

Top View

Order Number LM4664ITL, LM4664ITLX

See NS Package Number TLA09AAA

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Absolute Maximum Ratings (Notes 1, 2)

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

Supply Voltage (Note1)

Thermal Resistance

θ JA (micro SMD)

220˚C/W

6.0V

Soldering Information

See AN-1112 "microSMD Wafers Level Chip Scale

Package."

Storage Temperature

−65˚C to +150˚C

Voltage at Any Input Pin

V DD + 0.3V

≥

GND - 0.3V

Operating Ratings (Note 2)

Temperature Range

T MIN ≤

Power Dissipation (Note 3)

Internally Limited

ESD Susceptibility (Note 4)

7.0kV

T A ≤

T MAX

−40˚C

≤

T A ≤

85˚C

ESD Susceptibility (Note 5)

250V

Supply Voltage

2.7V ≤ V DD ≤ 5.5V

Junction Temperature (T J )

150˚C

Electrical Characteristics V DD =3V (Notes 1, 2)

The following specifications apply for V DD = 3V and R L =15µH+8 Ω + 15µH unless otherwise specified. Limits apply for T A =

25˚C.

LM4664

Units

(Limits)

Symbol

Parameter

Conditions

Typical

Limit

(Note 6)

(Notes 7, 8)

I DD

Quiescent Power Supply Current

V IN = 0V, No Load

V IN = 0V, R L =15µH+8

3.50

3.75

mA (max)

Ω

+ 15µH

5.0

I SD

Shutdown Current

V SD = GND (Note 9)

0.4

2.0

µA (max)

V SDIH

Shutdown Voltage Input High

1.0

1.4

V (min)

V SDIL

Shutdown Voltage Input Low

0.8

0.4

V (max)

V GSIH

Gain Select Input High

1.0

1.4

V (min)

V GSIL

Gain Select Input Low

0.8

0.4

V (max)

A V

Closed Loop Gain

V Gain Select =V DD

A V

Closed Loop Gain

V Gain Select = GND

V OS

Output Offset Voltage

mV (max)

T WU

Wake-up Time

P o

Output Power

THD = 1% (max), f = 1kHz

425

THD+N

Total Harmonic Distortion+Noise

P O = 100mW RMS ;f IN = 1kHz

0.35

R IN

Differential Input Resistance

V Gain Select =V DD

Ω

V Gain Select = GND

Ω

V Ripple = 100mV RMS sine wave

Inputs terminated to GND

(f = 217Hz)

PSRR

Power Supply Rejection Ratio

V Ripple = 100mV RMS sine wave

P OUT = 10mW,1kHz

(f = 217Hz)

CMRR

Common Mode Rejection Ratio

V Ripple = 100mV RMS ,

f Ripple = 217Hz

SNR

Signal to Noise Ratio

P O = 400mW RMS ; A-Weighted Filter

e OUT

Output Noise

A-Weighted filter, V in = 0V

125

µV

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Electrical Characteristics V DD =5V (Notes 1, 2)

The following specifications apply for V DD = 5V and R L =15µH+8

Ω

+ 15µH unless otherwise specified. Limits apply for T A =

25˚C.

LM4664

Units

(Limits)

Symbol

Parameter

Conditions

Typical

Limit

(Note 6)

(Notes 7, 8)

I DD

Quiescent Power Supply Current

V IN = 0V, No Load

V IN = 0V, R L =15µH+8

Ω

+ 15µH

I SD

Shutdown Current

V SD = GND (Note 9)

0.4

µA

V SDIH

Shutdown Voltage Input High

1.2

V SDIL

Shutdown Voltage Input Low

1.1

V GSIH

Gain Select Input High

1.2

V GSIL

Gain Select Input Low

1.1

A V

Closed Loop Gain

V Gain Select =V DD

A V

Closed Loop Gain

V Gain Select = GND

V OS

Output Offset Voltage

T WU

Wake-up Time

P o

Output Power

THD = 2% (max); f = 1kHz

1.1

THD+N

Total Harmonic Distortion+Noise

P O = 100mW RMS ;f IN = 1kHz

0.8

R IN

Differential Input Resistance

V Gain Select =V DD

Ω

V Gain Select = GND

Ω

V ripple = 100mV RMS sine wave

Inputs terminated to GND

(f = 217Hz)

PSRR

Power Supply Rejection Ratio

V Ripple = 100mV RMS sine wave

P OUT = 10mW,1kHz

(f = 217Hz)

CMRR

Common Mode Rejection Ratio

V Ripple = 100mV RMS ,

f Ripple = 217Hz

SNR

Signal to Noise Ratio

P O =1W RMS , A-Weighted Filter

e OUT

Output Noise

A-Weighted filter, V in = 0V

200

µV

Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified.

Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is

functional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which

guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit

is given, however, the typical value is a good indication of device performance.

Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by T JMAX ,

θ JA , and the ambient temperature T A . The maximum

allowable power dissipation is P DMAX =(T JMAX –T A )/

JA or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4664, T JMAX = 150˚C.

θ JA is 220˚C/W for the microSMD package.

Note 4: Human body model, 100pF discharged through a 1.5k

resistor.

Note 5: Machine Model, 220pF–240pF discharged through all pins.

Note 6: Typical specifications are specified at 25˚C and represent the parametric norm.

Note 7: Tested limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).

Note 8: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.

Note 9: Shutdown current is measured in a normal room environment. Exposure to direct sunlight will increase I SD by a maximum of 2µA. The Shutdown pin should

be driven as close as possible to GND for minimal shutdown current and to V DD for the best THD performance in PLAY mode. See the Application Information

section under SHUTDOWN FUNCTION for more information.

Ω

External Components Description

( Figure 1 )

Components

Functional Description

C S

Supply bypass capacitor which provides power supply filtering. Refer to the Power Supply Bypassing

section for information concerning proper placement and selection of the supply bypass capacitor.

C I

Input AC coupling capacitor which blocks the DC voltage at the amplifier’s input terminals.

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The typical

Typical Performance Characteristics

+ 15µH

P OUT = 100mW, 30kHz BW

+ 15µH

P OUT = 100mW, 30kHz BW

200960D5

200960D6

THD+N vs Power Out

V DD = 5V, R L =15µH+8

THD+N vs Power Out

V DD = 3V, R L =15µH+8

+ 15µH

f = 1kHz, 22kHz BW

200960D8

200960E0

CMRR vs Frequency

V DD = 5V, R L =15µH+8 Ω + 15µH

V CM = 300V RMS Sine Wave, 30kHz BW

CMRR vs Frequency

V DD = 3V, R L =15µH+8 Ω + 15µH

V CM = 300V RMS Sine Wave, 30kHz BW

200960E1

200960E2

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THD+N vs Frequency

V DD = 5V, R L =15µH+8

Ω

THD+N vs Frequency

V DD = 3V, R L =15µH+8

Ω

+ 15µH

f = 1kHz, 22kHz BW

Ω

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