National Semiconductor LM48511 Technical data

February 25, 2008

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

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

■ P

at VDD = 5V, PV1 = 7.8V

O

RL = 8Ω, THD+N = 1%

■ P

at VDD = 3V, PV1 = 4.8V

O

RL = 8Ω, THD+N = 1%

■ P

at VDD = 5V, PV1 = 7.8V

O

RL = 4Ω, THD+N = 1%

■ Shutdown Current at V

DD

= 3V

9mA (typ)

13.5mA (typ)

3.0W (typ)

1W (typ)

5.4W (typ)

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

Boomer® is a registered trademark of National Semiconductor Corporation.

© 2008 National Semiconductor Corporation 300222 www.national.com

FIGURE 1. LM48511 RF Emissions — 3 inch cable

Typical Application

LM48511

FIGURE 2. Typical LM48511 Audio Amplifier Application Circuit

www.national.com 2

300222i3

Connection Diagrams

LM48511

SQ Package

Order Number LM48511SQ

Top View

See NS Package Number SQA24B

SQ Package Marking

Top View
U — Wafer fab code
Z — Assembly plant

XY — 2 Digit date code

TT — Lot traceability

300222d4

300222d5

3 www.national.com

Pin Descriptions

LM48511

LLP-24 Pin Name Function

Regulator Feedback Select. Connect to VDD to select feedback

1 FB_SEL

2,3 SW Drain of the Internal FET Switch

4 SOFTSTART Soft Start Capacitor

5 SD_AMP

6 SS/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

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

DAP

To be soldered to board for enhanced thermal dissipation. Connect

network connected to FB_GND1. Connect to GND to select
feedback network connected to FB_GND0.

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

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

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

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

to GND plane.

www.national.com 4

LM48511

Absolute Maximum Ratings (Notes 2, 2)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/

Thermal Resistance

 θJC (SQ)

 θJA (SQ)

32.8°C/W

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

Operating Ratings

Temperature Range

T

≤ TA ≤ T

MIN

MAX

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

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

−40°C ≤ TA ≤ +85°C

Junction Temperature 150°C

Electrical Characteristics VDD = 5.0V (Notes 1, 2, 10)

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.

LM48511 Units

Symbol Parameter Conditions

VIN = 0, R

I

DD

Quiescent Power Supply Current

Fixed Frequency Mode (FF) 13.5 mA (max)

LOAD

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

V

I

SD

V

IH

V

IL

T

WU

V

OS

Shutdown Current

Logic Voltage Input High

Logic Voltage Input Low

Wake-up Time

Output Offset Voltage Note 12 0.01 3 mV

SD_BOOST

FB_SEL = GND

1.03 1.4 V (min)

0.92 0.4 V (min)

CSS = 0.1μF

= V

RL = 8Ω
f = 1kHz, BW = 22kHz

THD+N = 1%
FF
SS

THD+N = 10%
FF

P

O

Output Power

SS

RL = 4Ω
f = 1kHz, BW = 22kHz

THD+N = 1%
FF
SS

THD+N = 10%
FF
SS

PO = 2W, f = 1kHz, RL = 8Ω

FF

THD+N Total Harmonic Distortion + Noise

SS

PO = 3W, f = 1kHz, RL = 4Ω

FF
SS

= ∞

SD_AMP

= SS =

Typical

(Note 6)

Limit

(Note 7)

0.11 1

49 ms

3.0

2.6 W (min)

3.0

3.8

3.8

5.4

W

5.4

6.7

W

6.7

0.03

%

0.03

0.04

%

0.05

3.8°C/W

(Limits)

μA (max)

W

W
W

W

W

%

%

5 www.national.com

Symbol Parameter Conditions

LM48511

ε

OS

PSRR

CMRR

η

V

FB

Typical

(Note 6)

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

Output Noise

FF
SS

f = 20Hz to 20kHz

32
32

Inputs to AC GND, A weighted

Power Supply Rejection Ratio
(Input Referred)

Common Mode Rejection Ratio
(Input Referred)

Efficiency

FF
SS

V

RIPPLE

f

RIPPLE =

= 200mV

= 217Hz,

P-P

Sine,

FF
SS

V

RIPPLE

f

RIPPLE =

= 200mV

= 1kHz,

P-P

Sine,

FF
SS

V

RIPPLE

f

RIPPLE =

= 200mV

= 10kHz,

P-P

Sine,

FF
SS

V

= 1V

RIPPLE

P-P

, f

RIPPLE

= 217Hz

f = 1kHz, RL = 8Ω, PO = 1W

22
22

88
87

88
85

77
76

73

80

Feedback Pin Reference Voltage 1.23

LM48511 Units

Limit

(Limits)

(Note 7)

µV

µV

µV

µV

RMS

RMS

RMS

RMS

dB
dB

dB
dB

dB
dB

dB

%

V

Electrical Characteristics VDD = 3.6V (Notes 1, 2, 10)

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

Symbol Parameter Conditions

I

DD

I

SD

V

IH

V

IL

T

WU

V

OS

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

LM48511 Units

Quiescent Power Supply Current

Typical

(Note 6)

VIN = 0, R

LOAD

= ∞

Fixed Frequency Mode (FF) 16 mA (max)

Limit

(Note 7)

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

Shutdown Current

Logic Voltage Input High

Logic Voltage Input Low

Wake-up Time

V

SD_BOOST

FB_SEL = GND

CSS = 0.1μF

= V

SD_AMP

= SS =

0.03 1

μA (max)

0.96 1.4 V (min)

0.84 0.4 V (min)

50 ms

Output Offset Voltage Note 12 0.04 mV

(Limits)

www.national.com 6

Symbol Parameter Conditions

RL = 8Ω, f = 1kHz, BW = 22kHz

THD+N = 1%
FF
SS

THD+N = 10%
FF

P

O

Output Power

SS

RL = 4Ω, f = 1kHz, BW = 22kHz

THD+N = 1%
FF
SS

THD+N = 10%
FF
SS

PO = 1.5W, f = 1kHz, RL = 8Ω

FF

THD+N Total Harmonic Distortion + Noise

SS

PO = 3W, f = 1kHz, RL = 4Ω

FF
SS

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

FF

ε

OS

Output Noise

SS

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

FF
SS

V

= 200mV

RIPPLE

f

= 217Hz

RIPPLE =

FF
SS

V

= 200mV

RIPPLE

f

RIPPLE =

FF

= 1kHz

PSRR

Power Supply Rejection Ratio
(Input Referred)

SS

V

= 200mV

RIPPLE

f

= 10kHz

RIPPLE =

FF
SS

CMRR

η

V

FB

Common Mode Rejection Ratio
(Input Referred)

Efficiency

Feedback Pin Reference Voltage 1.23

V

= 1V

RIPPLE

f = 1kHz, RL = 8Ω, PO = 1W

P-P

P-P

P-P

P-P

, f

Sine,

Sine,

Sine,

RIPPLE

= 217Hz

LM48511 Units

Typical

(Note 6)

Limit

(Note 7)

2.5

2.5

3.0

3.0

4.3

4.2

5.4

W

5.3

0.03

0.03

0.04

0.05

35

µV

36

25

µV

26

85
86

87
86

78
77

73

77

(Limits)

W
W

W
W

W
W

W

%
%

%
%

RMS

µV

RMS

RMS

µV

RMS

dB
dB

dB
dB

dB
dB

dB

%

V

LM48511

7 www.national.com