National Semiconductor LM4674 Technical data

July 2, 2008

LM4674 Filterless 2.5W Stereo Class D Audio Power Amplifier

General Description

The LM4674 is a single supply, high efficiency, 2.5W/channel, filterless switching audio amplifier. A low noise PWM architecture eliminates the output filter, reducing external component count, board area consumption, system cost, and simplifying design.

The LM4674 is designed to meet the demands of mobile phones and other portable communication devices. Operating from a single 5V supply, the device is capable of delivering

2.5W/channel of continuous output power to a 4Ω load with less than 10% THD+N. Flexible power supply requirements allow operation from 2.4V to 5.5V.

The LM4674 features high efficiency compared to conventional Class AB amplifiers. When driving an 8Ω speaker from a 3.6V supply, the device features 85% efficiency at PO = 500mW. Four gain options are pin selectable through the G0 and G1 pins.

Output short circuit protection prevents the device from being damaged during fault conditions. Superior click and pop suppression eliminates audible transients on power-up/down and during shutdown. Independent left/right shutdown control maximizes power savings in mixed mono/stereo applications.

Key Specifications

■ Efficiency at 3.6V, 100mW into 8Ω 80% (typ)

■ Efficiency at 3.6V, 500mW into 8Ω 85% (typ)

■ Efficiency at 5V, 1W into 8Ω 85% (typ)

■ Quiescent Power Supply Current

at 3.6V supply 4mA

■ Power Output at V

RL = 4Ω, THD ≤ 10%

■ Power Output at V

RL = 8Ω, THD ≤ 10%

■ Shutdown current

= 5V,

2.5W (typ)

1.5W (typ)

0.03μA (typ)

Features

Output Short Circuit Protection

■

Stereo Class D operation

■

No output filter required

■

Logic selectable gain

■

Independent shutdown control

■

Minimum external components

■

Click and Pop suppression

■

Micro-power shutdown

■

Available in space-saving 2mm x 2mm x 0.6mm micro

■

SMD, and 4mm x 4mm x 0.8mm LLP packages

Applications

Mobile phones

■

PDAs

■

Laptops

■

Boomer® is a registered trademark of National Semiconductor Corporation.

Typical Application

LM4674

20167463

Ci = 1 μF CS1 = 1 μF CS2 = 0.1 μF

FIGURE 1. Typical Audio Amplifier Application Circuit

External Components Description

(Figure 1)

Components Functional Description

1. CSSupply 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.

2. CiInput AC coupling capacitor which blocks the DC voltage at the amplifier's input terminals.

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Connection Diagrams

LM4674

TL Package (2mm x 2mm x 0.6mm)

Top View

20167461

Order Number LM4674TL

See NS Package Number TL1611A

LLP Package (4mm x 4mm x 0.8mm)

LM4674TL Markings

Top View

XY = 2 Digit date code

TT = Lot traceability

G = Boomer Family

G2 = LM4674TL

LM4674SQ Markings

20167462

Order Number LM4674SQ

Top View

See NS Package Number SQA16A

20167466

Top View

20167465

U = Wafer Fab Code

Z = Assembly Plant

XY = 2 Digit date code

TT = Lot traceability

L4674SQ = LM4674SQ

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LM4674

BUMP PIN NAME FUNCTION

A1 4 INL+ Non-inverting left channel input

A2 6 PV

Power V

A3 7 OUTLA Left channel output A

A4 8 OUTLB Left channel output B

B1 3 INL- Inverting left channel input

B2 5 G1 Gain setting input 1

B3 10 SDR Right channel shutdown input

B4 9 SDL Left channel shutdown input

C1 2 INR- Inverting right channel input

C2 16 G0 Gain setting input 0

C3 12 GND Ground

C4 11 PGND Power Ground

D1 1 INR+ Non-inverting right channel input

D2 15 V

Power Supply

D3 14 OUTRA Right channel output A

D4 13 OUTRB Right channel output B

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LM4674

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.

Junction Temperature (T

Thermal Resistance

θJA (μSMD)

θJA (LLP)

JMAX

)

45.7°C/W

38.9°C/W

Supply Voltage (Note 1) 6.0V Storage Temperature −65°C to +150°C Input Voltage –0.3V to VDD +0.3V

Power Dissipation (Note 3) Internally Limited ESD Susceptibility, all other pins (Note 4) 2000V ESD Susceptibility (Note 5) 200V

Operating Ratings (Notes 1, 2)

Temperature Range

≤ TA ≤ T

MIN

Supply Voltage

MAX

−40°C ≤ TA ≤ 85°C

2.4V ≤ VDD ≤ 5.5V

Electrical Characteristics VDD = 3.6V (Notes 1, 2)

The following specifications apply for AV = 6dB, RL = 15µH + 8Ω + 15µH, f = 1kHz unless otherwise specified. Limits apply for T = 25°C.

Symbol Parameter Conditions

Differential Output Offset Voltage

VIN = 0, VDD = 2.4V to 5.0V

VIN = 0, RL = ∞,

Quiescent Power Supply Current

Both channels active, VDD = 3.6V

VIN = 0, RL = ∞, Both channels active, VDD = 5V

SDIH

SDIL

Shutdown Current

Shutdown Voltage Input High 1.4 V (min)

Shutdown Voltage Input Low 0.4 V (max)

Wake Up Time V

SDR

SDR/SDL

= V

= GND

SDL

= 0.4V 0.5 ms

G0, G1 = GND

RL = ∞

G0 = VDD, G1 = GND

Gain

RL = ∞

G0 = GND, G1 = V

RL = ∞

G0, G1 = V

RL = ∞

AV = 6dB

Input Resistance

AV = 12dB

AV = 18dB

AV = 24dB

LM4674

Typical Limit

(Note 6) (Notes 7, 8)

5 mV

4 6 mA

5 7.5 mA

0.03 1

6 6 ± 0.5 dB

12 12 ± 0.5 dB

18 18 ± 0.5 dB

24 24 ± 0.5 dB

18.75

11.25

6.25

Units

(Limits)

150°C

μA

kΩ

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LM4674

Symbol Parameter Conditions

LM4674

Typical Limit

(Note 6) (Notes 7, 8)

RL = 15μH + 4Ω + 15μH, THD ≤ 10% f = 1kHz, 22kHz BW

VDD = 5V 2.5

VDD = 3.6V 1.2 W

VDD = 2.5V 0.530 W

RL = 15μH + 8Ω + 15μH, THD ≤ 10% f = 1kHz, 22kHz BW

VDD = 5V

1.5 W

VDD = 3.6V 0.78 0.6 W

Output Power

VDD = 2.5V

RL = 15μH + 4Ω + 15μH, THD ≤ 1%

0.350

f = 1kHz, 22kHz BW

VDD = 5V

VDD = 3.6V

1.9 W

VDD = 2.5V 0.430 W

RL = 15μH + 8Ω + 15μH, THD = 1% f = 1kHz, 22kHz BW

THD+N Total Harmonic Distortion

PSRR Power Supply Rejection Ratio

VDD = 5V 1.25

VDD = 3.6V

0.63

VDD = 2.5V 0.285

PO = 500mW, f = 1kHz, RL = 8Ω

PO = 300mW, f = 1kHz, RL = 8Ω

= 200mV

RIPPLE

= 217Hz, Inputs AC GND,

RIPPLE

P-P

Sine,

0.07 %

0.05 %

Ci = 1μF, input referred

= 1V

RIPPLE

= 1kHz, Inputs AC GND,

RIPPLE

P-P

Sine,

Ci = 1μF, input referred

= 1V

CMRR Common Mode Rejection Ratio

Efficiency

Xtalk Crosstalk

SNR Signal to Noise Ratio

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 allowable power dissipation is P derating currents for more information.

Note 4: Human body model, 100pF discharged through a 1.5kΩ resistor.

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

Note 6: Typicals are measured at 25°C and represent the parametric norm.

Note 7: 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.

Output Noise

DMAX

= (T

– TA)/ θJA or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4674 see power

JMAX

RIPPLE

PO = 1W, f = 1kHz,

RL = 8Ω, VDD = 5V

PO = 500mW, f = 1kHz

VDD = 5V, PO = 1W

Input referred, A-Weighted Filter

P-P

= 217Hz

, θJA, and the ambient temperature, TA. The maximum

JMAX

Units

(Limits)

μV

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Block Diagrams

LM4674

FIGURE 2. Differential Input Configuration

20167426

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LM4674

20167464

FIGURE 3. Single-Ended Input Configuration

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