National Semiconductor LM4938 Technical data

LM4938
Stereo 2W Audio Power Amplifiers
with DC Volume Control and Selectable Gain

LM4938 Stereo 2W Audio Power Amplifiers with DC Volume Control and Selectable Gain

July 2005

General Description

The LM4938 is a monolithic integrated circuit that provides
DC volume control, and stereo bridged audio power amplifi­ers capable of producing 2W into 4Ω (Note 1) with less than

1.0% THD or 2.2W into 3Ω (Note 2) with less than 1.0%
THD.

®

Boomer
to provide high quality audio while requiring a minimum
amount of external components. The LM4938 incorporates a
DC volume control, stereo bridged audio power amplifiers
and a selectable gain or bass boost, making it optimally
suited for multimedia monitors, portable radios, desktop, and
portable computer applications.

The LM4938 features an externally controlled, low-power
consumption shutdown mode, and both a power amplifier
and headphone mute for maximum system flexibility and
performance.

Note 1: When properly mounted to the circuit board, LM4938MH will deliver
2W into 4Ω. See Application Information section Exposed-DAP package

PCB Mounting Considerations for more information.

Note 2: An LM4938MH that has been properly mounted to the circuit board

and forced-air cooled will deliver 2.2W into 3Ω.

audio integrated circuits were designed specifically

Key Specifications

n POat 1% THD+N
n into 3Ω 2.2W (typ)
n into 4Ω 2.0W (typ)
n into 8Ω 1.3W (typ)
n Single-ended mode - THD+N at 92mW into

32Ω 1.0%(typ)

n Shutdown current 0.5µA (typ)

Features

n Improved click and pop circuitry virtually eliminates

noise during turn on/off transitions

n DC Volume Control Interface
n System Beep Detect
n Stereo switchable bridged/single-ended power amplifiers
n Selectable internal/external gain and bass boost
n Thermal shutdown protection circuitry
n Unity gain stable

Applications

n Flat Panel Displays
n Portable and Desktop Computers
n Multimedia Monitors
n Portable Radios, PDAs, and Portable TVs

Block Diagram

20095601

FIGURE 1. LM4938 Block Diagram

Boomer®is a registered trademark of NationalSemiconductor Corporation.

© 2005 National Semiconductor Corporation DS200956 www.national.com

Connection Diagram

LM4938

TSSOP Package

Top View

Order Number LM4938MH

See NS Package Number MXA28A for Exposed-DAP TSSOP

20095602

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LM4938

Absolute Maximum Ratings (Note 10)

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

Supply Voltage 6.0V

Storage Temperature -65˚C to +150˚C

Input Voltage −0.3V to V

Power Dissipation (Note 11) Internally limited

DD

+0.3V

See AN-450 “Surface Mounting and their Effects on
Product Reliability” for other methods of soldering surface
mount devices.

θ

(typ) - MXA28A 2˚C/W

JC

θ

(typ) - MXA28A (exposed DAP) (Note 3) 41˚C/W

JA

θ

(typ) - MXA28A (exposed DAP) (Note 4) 54˚C/W

JA

θ

(typ) - MXA28A (exposed DAP) (Note 5) 59˚C/W

JA

θ

(typ) - MXA28A (exposed DAP) (Note 6) 93˚C/W

JA

ESD Susceptibility (Note 12) 2000V

ESD Susceptibility (Note 13) 200V

Junction Temperature 150˚C

Soldering Information

Small Outline Package

Vapor Phase (60 sec.) 215˚C

Operating Ratings

Temperature Range

≤ TA≤T

T

MIN

Supply Voltage 2.7V≤ V

MAX

Infrared (15 sec.) 220˚C

Electrical Characteristics for Entire IC (Notes 7, 10)

The following specifications apply for VDD= 5V unless otherwise noted. Limits apply for TA= 25˚C.

Symbol Parameter Conditions

V

DD

I

DD

I

SD

V

IH

V

IL

Supply Voltage 2.7 V (min)

Quiescent Power Supply Current VIN= 0V, IO= 0A 11 30 mA (max)

Shutdown Current V

shutdown

=V

DD

Headphone Sense High Input Voltage 4 V (min)

Headphone Sense Low Input Voltage 0.8 V (max)

−20˚C ≤TA ≤ 85˚C

≤ 5.5V

DD

LM4938

Typical

(Note 14)

Limit

(Note 15)

(Limits)

5.5 V (max)

0.5 2.0 µA (max)

Units

Electrical Characteristics for Volume Attenuators (Notes 7, 10)

The following specifications apply for VDD= 5V. Limits apply for TA= 25˚C.

Symbol Parameter Conditions

Typical

(Note 14)

C

A

RANGE

M

Attenuator Range

Mute Attenuation V

Gain accuracy with V
No Load

Gain accuracy with V
No Load

Attenuation with V

DCVol

(BM & SE)

= 5V, Bridged Mode (BM) 89 78 dB (min)

mute

V

= 5V, Single-Ended Mode (SE) 78 dB (min)

mute

DCVol

DCVol

= 5V,

<

=0V

0.5V,

±

0.5

±

2 dB (max)

89 75

Electrical Characteristics for Bridged Mode Operation (Notes 7, 10)

The following specifications apply for VDD= 5V, unless otherwise noted. Limits apply for TA= 25˚C.

LM4938

Symbol Parameter Conditions

V

OS

Output Offset Voltage VIN= 0V, No Load 5

Typical

(Note 14)

LM4938

(Note 15)

(Note 15)

Limit

±

0.75 dB (max)

Units

(Limits)

dB (min)

Limit

±

50 mV (max)

Units

(Limits)

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Electrical Characteristics for Bridged Mode Operation (Notes 7, 10) (Continued)

The following specifications apply for VDD= 5V, unless otherwise noted. Limits apply for TA= 25˚C.

LM4938

Symbol Parameter Conditions

P

O

THD+N Total Harmonic Distortion + Noise P

PSRR Power Supply Rejection Ratio

SNR Signal to Noise Ratio VDD= 5V, P

X

talk

Output Power THD+N=1.0%; f = 1kHz

=3Ω (Note 8)

R

L

THD+N=1.0%; f = 1kHz

=4Ω (Note 9)

R

L

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

=8Ω

R

L

THD+N = 10%;f=1kHz; R

= 0.4W, f = 1kHz,

O

=8Ω,AVD=2

R

L

= 1.0 µF, f = 120 Hz,

C

B

V

= 200 mVrms; RL=8Ω,

RIPPLE

Floating

CB= 1.0 µF, f = 120 Hz,
V

= 200 mVrms; RL=8Ω,

RIPPLE

Terminated

A-Wtd Filter, 1kHz

Channel Separation f = 1kHz, CB= 1.0µF, 1W 76 dB

= 1.2W, RL=8Ω,

OUT

=8Ω 1.5 W

L

LM4938

Typical

(Note 14)

(Note 15)

2.2 W

2W

1.3 1.0 W (min)

0.05 %

78 dB

60 dB

100 dB

Limit

Units

(Limits)

Electrical Characteristics for Single-Ended Mode Operation (Notes 7, 10)

The following specifications apply for VDD= 5V. Limits apply for TA= 25˚C.

LM4938

Symbol Parameter Conditions

P

O

THD+N Total Harmonic Distortion + Noise V

PSRR Power Supply Rejection Ratio

SNR Signal to Noise Ratio P

Output Power THD = 1.0%; f = 1kHz; RL=32Ω 92 mW

=1V

OUT

= 10kΩ,AVD=1

R

L

C

= 1.0 µF, f = 120 Hz,

B

V

RIPPLE

C

= 1.0 µF, f = 120 Hz,

B

V

RIPPLE

= 75mW, RL=32Ω,

OUT

, f = 1kHz,

RMS

= 200 mVrms, Floating

= 200 mVrms, Terminated

A-Wtd Filter

X

talk

Channel Separation f = 1kHz, CB= 1.0 µF 73 dB

Typical

(Note 14)

Limit

(Note 15)

0.065 %

63 dB

59 dB

100 dB

Units

(Limits)

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Electrical Characteristics for Single-Ended Mode Operation (Notes 7,

10) (Continued)

Note 3: The θJAgiven is for an MXA28A package whose exposed-DAP is soldered to an exposed 2in2piece of 1 ounce printed circuit board copper.

Note 4: The θ

through 21 8mil vias.

Note 5: The θ

Note 6: The θ

Note 7: All voltages are measured with respect to the ground pins, unless otherwise specified. All specifications are tested using the typical application as shown

in Figure 1.

Note 8: When driving 3Ω loads from a 5V supply the LM4938MH must be mounted to the circuit board and forced-air cooled.

Note 9: When driving 4Ω loads from a 5V supply the LM4938MH must be mounted to the circuit board.

Note 10: 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 11: The maximum power dissipation must be derated at elevated temperatures and is dictated by T
allowable power dissipation is P
can be found in the Absolute Maximum Ratings section above.

Note 12: Human body model, 100pF discharged through a 1.5kΩ resistor.

Note 13: Machine Model, 200pF – 220pF discharged through all pins.

Note 14: Typicals are measured at 25˚C and represent the parametric norm.

Note 15: Limits are guaranteed to National’s AOQL ( Average Outgoing Quality Level). Datasheet min/max specification limits are guaranteed by design, test, or

statistical analysis.

given is for an MXA28A package whose exposed-DAP is soldered to a 2in2piece of 1 ounce printed circuit board copper on a bottom side layer

JA

given is for an MXA28A package whose exposed-DAP is soldered to an exposed 1in2piece of 1 ounce printed circuit board copper.

JA

given is for an MXA28A package whose exposed-DAP is not soldered to any copper.

JA

, θJA, and the ambient temperature TA. The maximum

DMAX

=(T

JMAX−TA

)/θJA. For the LM4938, T

= 150˚C, and the typical junction-to-ambient thermal resistance for each package

JMAX

JMAX

LM4938

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Typical Application

LM4938

20095603

FIGURE 2. Typical Application Circuit

Truth Table for Logic Inputs

Gain

Sel

0 0 0 0 0 Internal Gain Fixed BTL

0 0 1 0 0 Internal Gain Fixed SE

0 1 0 0 0 Internal Gain Adjustable BTL

0 1 1 0 0 Internal Gain Adjustable SE

1 0 0 0 0 External Gain Fixed BTL

1 0 1 0 0 External Gain Fixed SE

1 1 0 0 0 External Gain Adjustable BTL

1 1 1 0 0 External Gain Adjustable SE

X X X 1 0 Muted X Muted

X X X X 1 Shutdown X X

Note 16: If system beep is detected on the Beep In pin, the system beep will be passed through the bridged amplifier regardless of the logic of the Mute and HP
sense pins.

Mode Headphone

Sense

Mute Shutdown Output Stage Set To DC Volume Output Stage

(Note 16)

Configuration

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Typical Performance Characteristics

LM4938

THD+N vs Output Power

= 3V, RL=4Ω, f = 1kHz

V

DD

THD+N vs Output Power

= 3V, RL=32Ω, SE, f = 1kHz

V

DD

THD+N vs Output Power

VDD= 3V, RL=8Ω, f = 1kHz

200956A2 200956A3

THD+N vs Output Power

VDD= 5V, RL=3Ω, f = 1kHz

THD+N vs Output Power

= 5V, RL=4Ω, f = 1kHz

V

DD

200956A4 200956A5

THD+N vs Output Power

VDD= 5V, RL=8Ω, BTL, f = 1kHz

200956A6 200956A7

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Typical Performance Characteristics (Continued)

LM4938

THD+N vs Output Power

V

= 5V, RL=32Ω, SE, f = 1kHz

DD

THD+N vs Frequency

= 3V, RL=4Ω,PO= 170mW

V

DD

THD+N vs Frequency

VDD= 5V, RL=8Ω,PO= 1W, BTL

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THD+N vs Frequency

VDD= 3V, RL=8Ω,PO= 160mW

20095696 20095697

THD+N vs Frequency

= 3V, RL=32Ω,PO= 20mW, SE

V

DD

20095698 20095699

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THD+N vs Frequency

VDD= 5V, RL=3Ω,PO= 600mW

Typical Performance Characteristics (Continued)

LM4938

THD+N vs Frequency

V

= 5V, RL=4Ω,PO= 600mW

DD

Frequency Response

= 3V, RL=4Ω,PO= 1.8W

V

DD

THD+N vs Frequency

VDD= 5V, RL=32Ω,PO= 70mW, SE

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Frequency Response

VDD= 3V, RL=8Ω,PO= 570mW

Frequency Response

= 3V, RL=32Ω,PO= 30mW, SE

V

DD

20095636 20095637

Frequency Response

VDD= 5V, RL=3Ω,PO= 1.8W

20095638 20095643

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