NSC LM48511 Datasheet

September 2007

LM48511
3W, Ultra-Low EMI, Filterless, Mono, Class D Audio Power
Amplifier with Spread Spectrum

General Description

The LM48511 integrates a boost converter with a high effi­ciency Class D audio power amplifier to provide 3W continu­ous power into an 8Ω speaker when operating from a 5V
power supply. When operating from a 3V to 4V power supply,
the LM48511 can be configured to drive 1 to 2.5W into an
8Ω load with less than 1% distortion (THD+N). The Class D
amplifier features a low noise PWM architecture that elimi­nates the output filter, reducing external component count,
board area consumption, system cost, and simplifying design.
A selectable spread spectrum modulation scheme suppress­es RF emissions, further reducing the need for output filters.

The LM48511’s switching regulator is a current-mode boost
converter operating at a fixed frequency of 1MHz. Two se­lectable feedback networks allow the LM48511 regulator to
dynamically switch between two different output voltages, im­proving efficiency by optimizing the amplifier’s supply voltage
based on battery voltage and output power requirements.

The LM48511 is designed for use in portable devices, such
as GPS, mobile phones, and MP3 players. The high, 80%
efficiency at 5V, extends battery life when compared to Boost­ed Class AB amplifiers. Independent regulator and amplifier
shutdown controls optimize power savings by disabling the
regulator when high output power is not required.

The gain of the LM48511 is set by external resistors, which
allows independent gain control from multiple sources by
summing the signals. Output short circuit and thermal over­load protection prevent the device from damage during fault
conditions. Superior click and pop suppression eliminates au­dible transients during power-up and shutdown.

Key Specifications

■ Quiescent Power Supply Current

VDD = 3V
VDD = 5V

9mA (typ)

13.5mA (typ)

■ P

O

at VDD = 5V, PV1 = 7.8V

RL = 8Ω, THD+N = 1%

3.0W (typ)

■ P

O

at VDD = 3V, PV1 = 4.8V

RL = 8Ω, THD+N = 1%

1W (typ)

■ Shutdown Current at V

DD

= 3V

0.01μA (typ)

Features

■

3W Output into 8Ω at 5V with THD+N = 1%

■

Selectable spread spectrum mode reduces EMI

■

80% Efficiency

■

Independent Regulator and Amplifier Shutdown Controls

■

Dynamically Selectable Regulator Output Voltages

■

Filterless Class D

■

3.0V – 5.5V operation

■

Low Shutdown Current

■

Click and Pop Suppression

Applications

■

GPS

■

Portable media

■

Cameras

■

Mobile Phones

■

Handheld games

EMI Graph

300222h5

FIGURE 1. LM48511 RF Emissions — 3 inch cable

Boomer® is a registered trademark of National Semiconductor Corporation.

© 2007 National Semiconductor Corporation 300222 www.national.com

LM48511 3W, Ultra-Low EMI, Filterless, Mono, Class D Audio Power Amplifier

with Spread Spectrum

Typical Application

300222i3

FIGURE 2. Typical LM48511 Audio Amplifier Application Circuit

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LM48511

Connection Diagrams

SQ Package

300222d4

Top View

Order Number LM48511SQ

See NS Package Number SQA24B

SQ Package Marking

300222d5

Top View
U — Wafer fab code
Z — Assembly plant

XY — 2 Digit date code

TT — Lot traceability

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LM48511

Pin Descriptions

LLP-24 Pin Name Function

1 FB_SEL

Regulator Feedback Select. Connect to VDD to select feedback
network connected to FB_GND1. Connect to GND to select
feedback network connected to FB_GND0.

2,3 SW Drain of the Internal FET Switch

4 SOFTSTART Soft Start Capacitor

5 SD_AMP

Amplifier Active Low Shutdown. Connect to VDD for normal
operation. Connect to GND to disable amplifier.

6 SS/FF

Modulation Mode Select. Connect to VDD for spread spectrum
mode (SS). Connect to GND for fixed frequency mode (FF).

7 GND Signal Ground

8 LS+ Amplifier Non-Inverting Output

9, 11 LSGND Amplifier H-Bridge Ground

10 PV1 Amplifier H-Bridge Power Supply. Connect to V1.

12 LS- Amplifier Inverting Output

13 V1 Amplifier Supply Voltage. Connect to PV1

14 VG0+ Amplifier Non-Inverting Gain Output

15 IN- Amplifier Inverting Input

16 IN+ Amplifier Non-Inverting Input

17 VG0– Amplifier Inverting Gain Output

18 VDD Power Supply

19 FB

Regulator Feedback Input. Connect FB to an external resistive
voltage divider to set the boost output voltage.

20 FB_GND1 Ground return for R3, R1 resistor divider

21 FB_GND0 Ground return for R3, R2 resistor divider

22,23 REGGND Power Ground (Booster)

24 SD_BOOST

Regulator Active Low Shutdown. Connect to VDD for normal
operation. Connect to GND to disable regulator.

DAP

To be soldered to board for enhanced thermal dissipation. Connect

to GND plane.

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LM48511

Absolute Maximum Ratings (Notes 2, 2)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

Supply Voltage (VDD, PV1, V1)

9V
Storage Temperature −65°C to +150°C

Input Voltage

−0.3V to VDD + 0.3V

Power Dissipation (Note 3) Internally limited
ESD Susceptibility (Note 4) 2000V
ESD Susceptibility (Note 5) 200V
Junction Temperature 150°C

Thermal Resistance

 θJC (SQ)

3.8°C/W

 θJA (SQ)

32.8°C/W

Operating Ratings

Temperature Range

T

MIN

≤ TA ≤ T

MAX

−40°C ≤ TA ≤ +85°C

Supply Voltage (VDD) 3.0V ≤ VDD ≤ 5.5V

Amplifier Voltage (PV1, V1) 4.8V ≤ PV1 ≤ 8.0V

Electrical Characteristics VDD = 5.0V (Notes 1, 2, 11)

The following specifications apply for VDD = 5.0V, PV1 = 7.8V (continuos mode), AV = 2V/V, R3 = 25.5kΩ, RLS = 4.87kΩ, RL =
8Ω, f = 1kHz, SS/FF = GND, unless otherwise specified. Limits apply for TA = 25°C.

Symbol Parameter Conditions

LM48511 Units

(Limits)

Typical

(Note 6)

Limit

(Notes 7, 8)

I

DD

Quiescent Power Supply Current

VIN = 0, R

LOAD

= ∞

Fixed Frequency Mode (FF) 13.5 mA (max)

Spread Spectrum Mode (SS) 14.5 22 mA (max)

I

SD

Shutdown Current

V

SD_BOOST

= V

SD_AMP

= SS =

FB_SEL = GND

0.11 1

μA (max)

V

IH

Logic Voltage Input High

1.03 1.4 V (min)

V

IL

Logic Voltage Input Low

0.92 0.4 V (min)

T

WU

Wake-up Time

CSS = 0.1μF

49 ms

V

OS

Output Offset Voltage Note 12 0.01 3 mV

P

O

Output Power

RL = 8Ω
f = 1kHz, BW = 22kHz

THD+N = 1%
FF
SS

3.0

3.0

2.6 W (min)
W

THD+N = 10%
FF
SS

3.8

3.8

W
W

RL = 4Ω
f = 1kHz, BW = 22kHz

THD+N = 1%
FF
SS

5.4

5.4

W

W

THD+N = 10%
FF
SS

6.7

6.7

W

W

THD+N Total Harmonic Distortion + Noise

PO = 2W, f = 1kHz, RL = 8Ω

FF
SS

0.03

0.03

%

%

PO = 3W, f = 1kHz, RL = 4Ω

FF
SS

0.04

0.05

%

%

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LM48511

Symbol Parameter Conditions

LM48511 Units

(Limits)

Typical

(Note 6)

Limit

(Notes 7, 8)

ε

OS

Output Noise

f = 20Hz to 20kHz
Inputs to AC GND, No weighting

FF
SS

32
32

µV

RMS

µV

RMS

f = 20Hz to 20kHz
Inputs to AC GND, A weighted

FF
SS

22
22

µV

RMS

µV

RMS

PSRR

Power Supply Rejection Ratio
(Input Referred)

V

RIPPLE

= 200mV

P-P

Sine,

f

RIPPLE =

= 217Hz,
FF
SS

88
87

dB
dB

V

RIPPLE

= 200mV

P-P

Sine,

f

RIPPLE =

= 1kHz,
FF
SS

88
85

dB
dB

V

RIPPLE

= 200mV

P-P

Sine,

f

RIPPLE =

= 10kHz,
FF
SS

77
76

dB
dB

CMRR

Common Mode Rejection Ratio
(Input Referred)

V

RIPPLE

= 1V

P-P

, f

RIPPLE

= 217Hz

73

dB

η

Efficiency

f = 1kHz, RL = 8Ω, PO = 1W

80

%

V

FB

Feedback Pin Reference Voltage 1.23

V

Electrical Characteristics VDD = 3.6V (Notes 1, 2, 11)

The following specifications apply for VDD = 3.6V, PV1 = 7V (continuous mode), AV = 2V/V, R3 = 25.5kΩ, RLS = 5.36kΩ, RL = 8Ω,
f = 1kHz, SS/FF

= GND, unless otherwise specified. Limits apply for TA = 25°C.

Symbol Parameter Conditions

LM48511 Units

(Limits)

Typical

(Note 6)

Limit

(Notes 7, 8)

I

DD

Quiescent Power Supply Current

VIN = 0, R

LOAD

= ∞

Fixed Frequency Mode (FF) 16 mA (max)

Spread Spectrum Mode (SS) 17.5 26.6 mA (max)

I

SD

Shutdown Current

V

SD_BOOST

= V

SD_AMP

= SS =

FB_SEL = GND

0.03 1

μA (max)

V

IH

Logic Voltage Input High

0.96 1.4 V (min)

V

IL

Logic Voltage Input Low

0.84 0.4 V (min)

T

WU

Wake-up Time

CSS = 0.1μF

50 ms

V

OS

Output Offset Voltage Note 12 0.04 mV

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LM48511

Symbol Parameter Conditions

LM48511 Units

(Limits)

Typical

(Note 6)

Limit

(Notes 7, 8)

P

O

Output Power

RL = 8Ω, f = 1kHz, BW = 22kHz

THD+N = 1%
FF
SS

2.5

2.5

W
W

THD+N = 10%
FF
SS

3.0

3.0

W
W

RL = 4Ω, f = 1kHz, BW = 22kHz

THD+N = 1%
FF
SS

4.3

4.2

W
W

THD+N = 10%
FF
SS

5.4

5.3

W

W

THD+N Total Harmonic Distortion + Noise

PO = 1.5W, f = 1kHz, RL = 8Ω

FF
SS

0.03

0.03

%
%

PO = 3W, f = 1kHz, RL = 4Ω

FF
SS

0.04

0.05

%
%

ε

OS

Output Noise

f = 20Hz to 20kHz
Inputs to AC GND, No weighting

FF
SS

35
36

µV

RMS

µV

RMS

f = 20Hz to 20kHz
Inputs to AC GND, A weighted

FF
SS

25
26

µV

RMS

µV

RMS

PSRR

Power Supply Rejection Ratio
(Input Referred)

V

RIPPLE

= 200mV

P-P

Sine,

f

RIPPLE =

= 217Hz
FF
SS

85
86

dB
dB

V

RIPPLE

= 200mV

P-P

Sine,

f

RIPPLE =

= 1kHz
FF
SS

87
86

dB
dB

V

RIPPLE

= 200mV

P-P

Sine,

f

RIPPLE =

= 10kHz
FF
SS

78
77

dB
dB

CMRR

Common Mode Rejection Ratio
(Input Referred)

V

RIPPLE

= 1V

P-P

, f

RIPPLE

= 217Hz

73

dB

η

Efficiency

f = 1kHz, RL = 8Ω, PO = 1W

77

%

V

FB

Feedback Pin Reference Voltage 1.23

V

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LM48511