Datasheet LM4841MTX, LM4841MHX, LM4841LQX, LM4841LQ, LM4841MT Datasheet (NSC)

LM4841

Stereo 2W Amplifiers with DC Volume Control,
Transient Free Outputs, and Cap-less Headphone Drive

General Description

The LM4841 is a monolithic integrated circuit that provides
DC volume control and stereo bridged audio power amplifi­ers capable of producing 2W into 4Ω (Note 1) or 2.2W into
3Ω (Note 2) with less than 1.0% THD.

The LM4841 uses advanced, latest generation circuitry to
eliminate all traces of clicks and pops when the supply
voltages is first applied. The amplifier has a headphone­amplifier-select input pin that is used to switch the amplifiers
from bridge to single-ended mode for driving headphones. A
new circuit topology eliminates headphone output coupling
capacitors (patent pending).

Boomer

®

audio integrated circuits are designed specifically
to provide high quality audio while requiring a minimum
amount of external components. The LM4841 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 LM4841 features an externally controlled, low-power
consumption shutdown mode (Shutdown Low), and both a
power amplifier and headphone mute for maximum system
flexibility and performance.

Note 1: When properly mounted to the circuit board, LM4841MH and
LM4841LQ will deliver 2W into 4Ω. The LM4841MT will deliver 1.1W into 8Ω.
See the Application Information section for LM4841MH usage information.

Note 2: An LM4841MH that has been properly mounted to the circuit board
and forced-air cooled will deliver 2.2W into 3Ω.

Key Specifications

n POat 1% THD+N
n into 3Ω (MH and LQ) 2.2W (typ)
n into 4Ω ( MH and LQ) 2.0W (typ)
n into 8Ω (MT, MH, and LQ) 1.1W (typ)
n Single-ended THD+N at 85mW into 32Ω 1.0%(typ)
n Shutdown current 0.7µA (typ)

Features

n Stereo headphone amplifier mode that eliminates the

Output Coupling Capacitors (patent pending)

n Acoustically Enhanced DC Volume Control Taper
n System Beep Detect
n Stereo switchable bridged/single-ended power amplifiers
n Selectable internal/external gain and bass boost
n Advanced “click and pop” suppression circuitry
n Thermal shutdown protection circuitry

Applications

n Portable and Desktop Computers
n Multimedia Monitors
n Portable Radios, PDAs, and Portable TVs

Connection Diagrams

TSSOP Package

20028002

Top View

Order Number LM4841MT or LM4841MH

See NS Package Number MTC28 for TSSOP and MXA28A for Exposed-DAP TSSOP

Boomer®is a registered trademark of National Semiconductor Corporation.

August 2002

LM4841 Stereo 2W Amplifiers with DC Volume Control,Transient Free Outputs, and Cap-less

Headphone Drive

© 2002 National Semiconductor Corporation DS200280 www.national.com

Connection Diagrams (Continued)

LLP Package

20028097

Top View

Order Number LM4841LQ

See NS Package Number LQA028AA for Exposed-DAP LLP

Block Diagram

20028001

FIGURE 1. LM4841 Block Diagram

LM4841

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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

DD

+0.3V

Power Dissipation (Note 11) Internally limited

ESD Susceptibility (Note 12)

All pins except Pin 28 2500V

Pin 28 6500V

ESD Susceptibility (Note 13) 200V

Junction Temperature 150˚C

Soldering Information

Small Outline Package

Vapor Phase (60 sec.) 215˚C

Infrared (15 sec.) 220˚C

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

θ

JC

(typ) — LQA028A 3˚C/W

θ

JA

(typ) — LQA028A 42˚C/W

θ

JC

(typ) — MTC28 20˚C/W

θ

JA

(typ) — MTC28 80˚C/W

θ

JC

(typ) — MXA28A 2˚C/W

θ

JA

(typ) — MXA28A (exposed

DAP) (Note 4)

41˚C/W

θ

JA

(typ) — MXA28A (exposed

DAP) (Note 3)

54˚C/W

θ

JA

(typ) — MXA28A (exposed

DAP) (Note 5)

59˚C/W

θ

JA

(typ) — MXA28A (exposed

DAP) (Note 6)

93˚C/W

Operating Ratings

Temperature Range

T

MIN

≤ TA≤T

MAX

−40˚C ≤TA ≤ 85˚C

Supply Voltage 2.7V≤ V

DD

≤ 5.5V

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

LM4841

Units

(Limits)

Typical

(Note 14)

Limit

(Note 15)

V

DD

Supply Voltage 2.7 V (min)

5.5 V (max)

I

DD

Quiescent Power Supply Current VIN= 0V, IO= 0A 15 30 mA (max)

I

SD

Shutdown Current V

shutdown

= GND 0.7 2.0 µA (max)

V

IH

Headphone Sense High Input Voltage 4 V (min)

V

IL

Headphone Sense Low Input Voltage 0.8 V (max)

TH

um

Un-Mute Threshold Voltage Gain 1st Stage = 1

V

shutdown

=V

DD

VINapplied to A or B input

22

10
40

mV

rms

mV

rms

Electrical Characteristics for Volume Attenuators (Notes 7, 10)

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

Symbol Parameter Conditions

LM4841

Units

(Limits)

Typical

(Note 14)

Limit

(Note 15)

C

RANGE

Attenuator Range Gain with V

DCVol

= 5V, No Load

±

0.75 dB (max)

Attenuation with V

DCVol

= 0V (BM &

SE)

-75 dB (min)

A

M

Mute Attenuation V

mute

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

V

mute

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

LM4841

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

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

Symbol Parameter Conditions

LM4841

Units

(Limits)

Typical

(Note 14)

Limit

(Note 15)

P

O

Output Power THD = 1.0%; f = 1kHz; RL=32Ω 85 mW

THD=10%;f=1kHz; R

L

=32Ω 95 mW

THD+N Total Harmonic Distortion+Noise V

OUT

=1V

RMS

, f=1kHz, RL= 10kΩ,

A

VD

=1

0.065 %

PSRR Power Supply Rejection Ratio C

B

= 1.0 µF, f =120 Hz,

V

RIPPLE

= 200 mVrms

58 dB

SNR Signal to Noise Ratio P

OUT

=75 mW, RL=32Ω, A-Wtd

Filter

102 dB

X

talk

Channel Separation f=1kHz, CB= 1.0 µF 65 dB

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.

Symbol Parameter Conditions

LM4841

Units

(Limits)

Typical

(Note 14)

Limit

(Note 15)

V

OS

Output Offset Voltage VIN= 0V, No Load 5

±

50 mV (max)

P

O

Output Power THD+N=1.0%; f=1kHz; RL=3Ω

(Note 8)

2.2 W

THD+N=1.0%; f=1kHz; R

L

=4Ω

(Note 9)

2W

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

L

=8Ω

1.1 1.0 W (min)

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

L

=8Ω 1.5 W

THD+N Total Harmonic Distortion+Noise P

O

= 1W, 20 Hz<f<20 kHz,

R

L

=8Ω,AVD=2

0.3 %

P

O

= 340 mW, RL=32Ω 1.0 %

PSRR Power Supply Rejection Ratio C

B

= 1.0 µF, f = 120 Hz,

V

RIPPLE

= 200 mVrms; RL=8Ω

74 dB

SNR Signal to Noise Ratio V

DD

= 5V, P

OUT

= 1.1W, RL=8Ω,

A-Wtd Filter

93 dB

X

talk

Channel Separation f=1kHz, CB= 1.0 µF 70 dB

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

JA

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

through 21 8mil vias.

Note 5: The θ

JA

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

Note 6: The θ

JA

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

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, LM4841MH and LM4841LQ must be mounted to the circuit board and forced-air cooled.

Note 9: When driving 4Ω loads from a 5V supply, the LM4841MH and LM4841LQ 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

JMAX

, θJA, and the ambient temperature TA. The maximum

allowable power dissipation is P

DMAX

=(T

JMAX−TA

)/θJA. For the LM4841MT and LM4841LQ, T

JMAX

= 150˚C. See Power Dissipation for further information.

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

Note 13: Machine Model, 220 pF–240 pF 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.

LM4841

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Typical Application

Truth Table for Logic Inputs

(Note 16)

Headphone

Sense

Gain Select Mode Mute Output Stage Set

To

Volume Control

X 0 0 0 Internal Gain On

X 0 0 0 Internal Gain On

X 1 0 0 External Gain On

X 1 0 0 External Gain On

On 0 1 0 Internal Gain On

Off 0 1 0 External Gain On

On 1 1 0 External Gain On

Off 1 1 0 Internal Gain On

X X X 1 X Muted

Note 16: If system beep is detected on the Beep In pin (pin 11), the system beep will be passed through the bridged amplifier regardless of the logic of the Mute
and HP sense pins.

20028003

FIGURE 2. Typical Application Circuit ( MT / MH Package Pinout )

LM4841

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Typical Performance Characteristics
MH/LQ Specific Characteristics

LM4841MH/LQ

THD+N vs Output Power

LM4841MH/LQ

THD+N vs Frequency

20028070

20028071

LM4841MH/LQ

THD+N vs Output Power

LM4841MH/LQ

THD+N vs Frequency

20028072

20028073

LM4841MH/LQ

Power Dissipation vs Output Power

LM4841MH/LQ (Note 17)

Power Derating Curve

20028065

20028064

Note 17: These curves show the thermal dissipation ability of the LM4841MH/LQ at different ambient temperatures given these conditions:

500LFPM + 2in

2

: The part is soldered to a 2in2, 1 oz. copper plane with 500 linear feet per minute of forced-air flow across it.

2in

2

on bottom: The part is soldered to a 2in2, 1oz. copper plane that is on the bottom side of the PC board through 21 8 mil vias.

2in

2

: The part is soldered to a 2in2, 1oz. copper plane.

1in

2

: The part is soldered to a 1in2, 1oz. copper plane.

Not Attached: The part is not soldered down and is not forced-air cooled.

LM4841

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Non-MH/LQ Specific Characteristics

THD+N vs Frequency THD+N vs Frequency

20028057

20028058

THD+N vs Frequency THD+N vs Frequency

20028014

20028015

THD+N vs Frequency THD+N vs Frequency

20028016

20028017

LM4841

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Non-MH/LQ Specific Characteristics (Continued)

THD+N vs Frequency THD+N vs Frequency

20028018 20028019

THD+N vs Frequency THD+N vs Frequency

20028020

20028021

THD+N vs Frequency THD+N vs Output Power

20028022

20028024

LM4841

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Non-MH/LQ Specific Characteristics (Continued)

THD+N vs Output Power THD+N vs Output Power

20028025

20028026

THD+N vs Output Power THD+N vs Output Power

20028027

20028028

THD+N vs Output Power THD+N vs Output Power

20028029

20028030

LM4841

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Non-MH/LQ Specific Characteristics (Continued)

THD+N vs Output Power THD+N vs Output Power

20028031

20028032

THD+N vs Output Power THD+N vs Output Power

20028033

20028034

THD+N vs Output Voltage

Docking Station Pins

THD+N vs Output Voltage

Docking Station Pins

20028059

20028060

LM4841

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Typical Performance Characteristics

Output Power vs
Load Resistance

Output Power vs
Load Resistance

20028062

20028006

Output Power vs

Load Resistance

Power Supply

Rejection Ratio

20028007

20028039

Dropout Voltage

Output Power vs

Load Resistance

20028053

20028008

LM4841

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Typical Performance Characteristics (Continued)

Volume Control

Characteristics

Power Dissipation vs

Output Power

20028040

20028051

Power Dissipation vs

Output Power

External Gain/

Bass Boost Characteristics

20028052

20028061

Power Derating Curve Crosstalk

20028063

20028049

LM4841

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Typical Performance Characteristics (Continued)

Output Power

vs Supply voltage

Output Power

vs Supply Voltage

20028054 20028056

Supply Current

vs Supply Voltage

20028009

LM4841

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Application Information

ELIMINATING OUTPUT COUPLING CAPACITORS

Typical single-supply audio amplifiers that can switch be­tween driving bridge-tied-load (BTL) speakers and
single-ended (SE) headphones use a coupling capacitor on
each SE output. This capacitor blocks the half-supply volt­age to which the output amplifiers are typically biased and
couples the audio signal to the headphones. The signal
return to circuit ground is through the headphone jack’s
sleeve.

The LM4841 eliminates these coupling capacitors. Amplifi­erA+ (pin 28 on MT/MH) is internally configured to apply
V

DD

/2 to a stereo headphone jack’s sleeve. This voltage
matches the quiescent voltage present on the AmpAout- and
AmpBout- outputs that drive the headphones. The head­phones operate in a manner very similar to a
bridge-tied-load (BTL). The same DC voltage is applied to
both headphone speaker terminals. This results in no net DC
current flow through the speaker. AC current flows through a
headphone speaker as an audio signal’s output amplitude
increases on the speaker’s terminal.

When operating as a headphone amplifier, the headphone
jack sleeve is not connected to circuit ground. Using the
headphone output jack as a line-level output will place the

LM4841’s one-half supply voltage on a plug’s sleeve con­nection. Driving a portable notebook computer or
audio-visual display equipment is possible. This presents no
difficulty when the external equipment uses capacitively
coupled inputs. For the very small minority of equipment that
is DC-coupled, the LM4841 monitors the current supplied by
the amplifier that drives the headphone jack’s sleeve. If this
current exceeds 500mA

PK

, the amplifier is shutdown, pro-

tecting the LM4841 and the external equipment.

OUTPUT TRANSIENT (’POPS AND CLICKS’)
ELIMINATED

The LM4841 contains advanced circuitry that eliminates out­put transients (’pop and click’). This circuitry prevents all
traces of transients when the supply voltage is first applied,
when the part resumes operation after shutdown, or when
switching between BTL speakers and SE headphones. Two
circuits combine to eliminate pop and click. One circuit
mutes the output when switching between speaker loads.
Another circuit monitors the input signal. It maintains the
muted condition until there is sufficient input signal magni­tude (

>

22mV

RMS

, typ) to mask any remaining transient that

may occur. (See Turn On Characteristics).

Figure 3 shows the LM4841’s lack of transients in the differ­ential signal (Trace B) across a BTL 8Ω load. The LM4841’s
active-high SHUTDOWN pin is driven by the logic signal
shown in Trace A. Trace C is the VOUT- output signal and
trace D is the VOUT+ output signal. The shutdown signal

frequency is 1Hz with a 50% duty cycle. Figure 4 is gener­ated with the same conditions except that the output drives a
32Ω single-ended (SE) load. Again, no trace of output tran­sients on Trace B can be observed.

20028095

FIGURE 3. Differential output signal (Trace B) is devoid of transients. The SHUTDOWN pin is driven by a shutdown

signal (Trace A). The inverting output (Trace C) and the non-inverting output (Trace D) are applied across an 8Ω BTL

load.

LM4841

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Application Information (Continued)

EXPOSED-DAP PACKAGE PCB MOUNTING
CONSIDERATIONS

The LM4841’s exposed-DAP (die attach paddle) packages
(MH,LQ) provide a low thermal resistance between the die
and the PCB to which the part is mounted and soldered. This
allows rapid heat transfer from the die to the surrounding
PCB copper traces, ground plane and, finally, surrounding
air. The result is a low voltage audio power amplifier that
produces 2.1W at ≤ 1% THD with a 4Ω load. This high power
is achieved through careful consideration of necessary ther­mal design. Failing to optimize thermal design may compro­mise the LM4841’s high power performance and activate
unwanted, though necessary, thermal shutdown protection.

The MH and LQ packages must have their exposed DAPs
soldered to a grounded copper pad on the PCB. The DAP’s
PCB copper pad is connected to a large grounded plane of
continuous unbroken copper. This plane forms a thermal
mass heat sink and radiation area. Place the heat sink area
on either outside plane in the case of a two-sided PCB, or on
an inner layer of a board with more than two layers. Connect
the DAP copper pad to the inner layer or backside copper
heat sink area with 32(4x8) (MH) vias or 6(3x2) LQ. The via
diameter should be 0.012in–0.013in with a 1.27mm pitch.
Ensure efficient thermal conductivity by plating-through and
solder-filling the vias.

Best thermal performance is achieved with the largest prac­tical copper heat sink area. If the heatsink and amplifier
share the same PCB layer, a nominal 2.5in

2

(min) area is
necessary for 5V operation with a 4Ω load. Heatsink areas
not placed on the same PCB layer as the LM4841MH and
LQ packages should be 5in

2

(min) for the same supply
voltage and load resistance. The last two area recommen­dations apply for 25˚C ambient temperature. Increase the
area to compensate for ambient temperatures above 25˚C.
The junction temperature must be held below 150˚C to pre­vent activating the LM4841’s thermal shutdown protection.
The LM4841’s power de-rating curve in the Typical Perfor-
mance Characteristics shows the maximum power dissipa­tion versus temperature. Example PCB layouts for the
exposed-DAP TSSOP and LQ packages are shown in the
Demonstration Board Layout section. Further detailed and
specific information concerning PCB layout and fabrication is
available in National Semiconductor’s AN1187.

PCB LAYOUT AND SUPPLY REGULATION
CONSIDERATIONS FOR DRIVING 3Ω AND 4Ω LOADS

Power dissipated by a load is a function of the voltage swing
across the load and the load’s impedance. As load imped­ance decreases, load dissipation becomes increasingly de­pendent on the interconnect (PCB trace and wire) resistance
between the amplifier output pins and the load’s connec­tions. Residual trace resistance causes a voltage drop,
which results in power dissipated in the trace and not in the
load as desired. For example, 0.1Ω trace resistance reduces
the output power dissipated by a 4Ω load from 2.1W to 2.0W.
This problem of decreased load dissipation is exacerbated
as load impedance decreases. Therefore, to maintain the
highest load dissipation and widest output voltage swing,
PCB traces that connect the output pins to a load must be as
wide as possible.

Poor power supply regulation adversely affects maximum
output power. A poorly regulated supply’s output voltage
decreases with increasing load current. Reduced supply
voltage causes decreased headroom, output signal clipping,
and reduced output power. Even with tightly regulated sup­plies, trace resistance creates the same effects as poor
supply regulation. Therefore, making the power supply
traces as wide as possible helps maintain full output voltage
swing.

BRIDGE CONFIGURATION EXPLANATION

As shown in Figure 2, the LM4841 output stage consists of
two pairs of operational amplifiers, forming a two-channel
(channel A and channel B) stereo amplifier. (Though the
following discusses channel A, it applies equally to channel
B.)

Figure 2 shows that the first amplifier’s negative (-) output
serves as the second amplifier’s input. This results in both
amplifiers producing signals identical in magnitude, but 180˚
out of phase. Taking advantage of this phase difference, a
load is placed between −OUTA and +OUTA and driven dif­ferentially (commonly referred to as “bridge mode”). This
results in a differential gain of

A

VD

=2*(R

GFA/RGIA

) (1)

20028096

FIGURE 4. Single-ended output signal (Trace B) is devoid of transients. The SHUTDOWN pin is driven by a shutdown

signal (Trace A). The inverting output (Trace C) and the V

BYPASS

output (Trace D) are applied across a 32Ω BTL load.

LM4841

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Application Information (Continued)

Bridge mode amplifiers are different from single-ended am­plifiers that drive loads connected between a single amplifi­er’s output and ground. For a given supply voltage, bridge
mode has a distinct advantage over the single-ended con­figuration: its differential output doubles the voltage
swing across the load. This produces four times the output
power when compared to a single-ended amplifier under the
same conditions. This increase in attainable output power
assumes that the amplifier is not current limited or that the
output signal is not clipped. To ensure minimum output sig­nal clipping when choosing an amplifier’s closed-loop gain,
refer to the Audio Power Amplifier Design section.

Another advantage of the differential bridge output is no net
DC voltage across the load. This is accomplished by biasing
channel A’s and channel B’s outputs at half-supply. This
eliminates the coupling capacitor that single supply, single­ended amplifiers require. Eliminating an output coupling ca­pacitor in a single-ended configuration forces a single-supply
amplifier’s half-supply bias voltage across the load. This
increases internal IC power dissipation and may perma­nently damage loads such as speakers.

POWER DISSIPATION

Power dissipation is a major concern when designing a
successful single-ended or bridged amplifier. Equation (2)
states the maximum power dissipation point for a single­ended amplifier operating at a given supply voltage and
driving a specified output load.

P

DMAX

=(VDD)2/(2π2RL) Single-Ended (2)

However, a direct consequence of the increased power de­livered to the load by a bridge amplifier is higher internal
power dissipation for the same conditions.

The LM4841 has two operational amplifiers per channel. The
maximum internal power dissipation per channel operating in
the bridge mode is four times that of a single-ended ampli­fier. From Equation (3), assuming a 5V power supply and a
4Ω load, the maximum single channel power dissipation is

1.27W or 2.54W for stereo operation.

P

DMAX

=4*(VDD)2/(2π2RL) Bridge Mode (3)

The LM4841’s power dissipation is twice that given by Equa­tion (2) or Equation (3) when operating in the single-ended
mode or bridge mode, respectively. Twice the maximum
power dissipation point given by Equation (3) must not ex­ceed the power dissipation given by Equation (4):

P

DMAX

'=(T

JMAX−TA

)/θ

JA

(4)

The LM4841’s T

JMAX

= 150˚C. In the LQ package soldered

to a DAP pad that expands to a copper area of 5in

2

on a

PCB, the LM4841’s θ

JA

is 20˚C/W. In the MH and LQ pack­ages soldered to a DAP pad that expands to a copper area
of 2in

2

on a PCB, the LM4841MH’s and LQ’s θJAis 41˚C/W.

For the LM4841MT package, θ

JA

= 80˚C/W. At any given

ambient temperature T

A

, use Equation (4) to find the maxi­mum internal power dissipation supported by the IC packag­ing. Rearranging Equation (4) and substituting P

DMAX

for

P

DMAX

' results in Equation (5). This equation gives the maxi-

mum ambient temperature that still allows maximum stereo
power dissipation without violating the LM4841’s maximum
junction temperature.

T

A=TJMAX

– 2*P

DMAXθJA

(5)

For a typical application with a 5V power supply and an 4Ω
load, the maximum ambient temperature that allows maxi­mum stereo power dissipation without exceeding the maxi­mum junction temperature is approximately 45˚C for the MH
package.

T

JMAX=PDMAXθJA+TA

(6)

Equation (6) gives the maximum junction temperature
T

JMAX

. If the result violates the LM4841’s 150˚C T

JMAX

,
reduce the maximum junction temperature by reducing the
power supply voltage or increasing the load resistance. Fur­ther allowance should be made for increased ambient tem­peratures.

The above examples assume that a device is a surface
mount part operating around the maximum power dissipation
point. Since internal power dissipation is a function of output
power, higher ambient temperatures are allowed as output
power or duty cycle decreases.

If the result of Equation (2) is greater than that of Equation
(3), then decrease the supply voltage, increase the load
impedance, or reduce the ambient temperature. If these
measures are insufficient, a heat sink can be added to
reduce θ

JA

. The heat sink can be created using additional
copper area around the package, with connections to the
ground pin(s), supply pin and amplifier output pins. External,
solder attached SMT heatsinks such as the Thermalloy
7106D can also improve power dissipation. When adding a
heat sink, the θ

JA

is the sum of θJC, θCS, and θSA.(θJCis the

junction-to-case thermal impedance, θ

CS

is the case-to-sink

thermal impedance, and θ

SA

is the sink-to-ambient thermal
impedance.) Refer to the Typical Performance Character-
istics curves for power dissipation information at lower out­put power levels.

POWER SUPPLY BYPASSING

As with any power amplifier, proper supply bypassing is
critical for low noise performance and high power supply
rejection. Applications that employ a 5V regulator typically
use a 10 µF in parallel with a 0.1 µF filter capacitor to
stabilize the regulator’s output, reduce noise on the supply
line, and improve the supply’s transient response. However,
their presence does not eliminate the need for a local 1.0 µF
tantalum bypass capacitance connected between the
LM4841’s supply pins and ground. Do not substitute a ce­ramic capacitor for the tantalum. Doing so may cause oscil­lation. Keep the length of leads and traces that connect
capacitors between the LM4841’s power supply pin and
ground as short as possible. Connecting a 1µF capacitor,
C

B

, between the BYPASS pin and ground improves the
internal bias voltage’s stability and the amplifier’s PSRR. The
PSRR improvements increase as the bypass pin capacitor
value increases. Too large a capacitor, however, increases
turn-on time and can compromise the amplifier’s click and
pop performance. The selection of bypass capacitor values,
especially C

B

, depends on desired PSRR requirements,
click and pop performance (as explained in the following
section, Selecting Proper External Components), system
cost, and size constraints.

LM4841

www.national.com 16

Application Information (Continued)

SELECTING PROPER EXTERNAL COMPONENTS

Optimizing the LM4841’s performance requires properly se­lecting external components. Though the LM4841 operates
well when using external components with wide tolerances,
best performance is achieved by optimizing component val­ues.

The LM4841 is unity-gain stable, giving a designer maximum
design flexibility. The gain should be set to no more than a
given application requires. This allows the amplifier to
achieve minimum THD+N and maximum signal-to-noise ra­tio. These parameters are compromised as the closed-loop
gain increases. However, low gain circuits demand input
signals with greater voltage swings to achieve maximum
output power. Fortunately, many signal sources such as
audio CODECs have outputs of 1V

RMS

(2.83V

P-P

). Please
refer to the Audio Power Amplifier Design section for more
information on selecting the proper gain.

Input Capacitor Value Selection

Amplifying the lowest audio frequencies requires a high
value input coupling capacitor (0.33µF in Figure 2), but high
value capacitors can be expensive and may compromise
space efficiency in portable designs. In many cases, how­ever, the speakers used in portable systems, whether inter­nal or external, have little ability to reproduce signals below
150 Hz. Applications using speakers with this limited fre­quency response reap little improvement by using a large
input capacitor.

Besides effecting system cost and size, the input coupling
capacitor has an affect on the LM4841’s click and pop per­formance. When the supply voltage is first applied, a tran­sient (pop) is created as the charge on the input capacitor
changes from zero to a quiescent state. The magnitude of
the pop is directly proportional to the input capacitor’s size.
Higher value capacitors need more time to reach a quiescent
DC voltage (usually V

DD

/2) when charged with a fixed cur­rent. The amplifier’s output charges the input capacitor
through the feedback resistor, R

f

. Thus, pops can be mini­mized by selecting an input capacitor value that is no higher
than necessary to meet the desired −6dB frequency.

As shown in Figure 2, the input resistor (R

IA,RIB

= 20k) ( and

the input capacitor (C

IA,CIB

= 0.33µF) produce a −6dB high

pass filter cutoff frequency that is found using Equation (7).

(7)

As an example when using a speaker with a low frequency
limit of 150Hz, the input coupling capacitor, using Equation
(7), is 0.063µF. The 0.33µF input coupling capacitor shown
in Figure 2 allows the LM4841 to drive a high efficiency, full
range speaker whose response extends below 30Hz.

TURN ON Characteristics

The LM4841 contains advanced circuitry that minimizes
turn-on and shutdown transients or “clicks and pops”. For
this discussion, turn-on refers to either applying the power
supply voltage or when the shutdown mode is deactivated.
While the power supply is ramping to its final value, the
LM4841’s internal amplifiers are configured as unity gain
buffers. An internal current source changes the voltage of

the BYPASS pin in a controlled, linear manner. Ideally, the
input and outputs track the voltage applied to the BYPASS
pin. The gain of the internal amplifiers remains unity until the
voltage on the BYPASS pin reaches 1/2 V

DD

. As soon as the
voltage on the BYPASS pin is stable, the LM4841 is ready to
be fully turned on. To turn the device on, the input signal
must exceed 22mV

rms

. This is accomplished through a
threshold detect circuit that enables all appropriate output
amplifiers after the 22mVrms limit is reached. Until this
threshold is reached, some of the amplifiers remain in a
tri-state mode. This insures that there is no current flowing
through to the speakers or headphones during power up.
Without current flow, the speakers or headphones remain
silent. During headphone mode, A+, B-, and B+ are in tri­state mode during power up. During speaker mode, A+ and
B+ are in tri-state mode during power up.

Although the BYPASS pin current cannot be modified,
changing the size of C

BYP

alters the device’s turn-on time.As

the size of C

BYP

increases, the turn-on time increases. There

is a linear relationship between the size of C

BYP

and the
turn-on time. Here are some typical turn-on times for various
values of C

BYP

:

C

BYP

T

ON

0.01µF 2ms

0.1µF 20ms

0.22µF 44ms

0.47µF 94ms

1.0µF 200ms

DOCKING STATION INTERFACE

Applications such as notebook computers can take advan­tage of a docking station to connect to external devices such
as monitors or audio/visual equipment that sends or receives
line level signals. The LM4841 has two outputs, Dock A and
Dock B, which connect to outputs of the internal input am­plifiers that drive the volume control inputs. These input
amplifiers can drive loads of

>

1kΩ (such as powered speak­ers) with a rail-to-rail signal. Since the output signal present
on the Dock A and Dock B pins are biased to V

DD

/2, coupling
capacitors should be connected in series with the load when
using these outputs. Typical values for the output coupling
capacitors are 0.33µF to 1.0µF. If polarized coupling capaci­tors are used, connect their ’+’ terminals to the respective
output pin.

Since the Dock outputs precede the internal volume control,
the signal amplitude will be equal to the input signal’s mag­nitude and cannot be adjusted. However, the input amplifi­er’s closed-loop gain can be adjusted using external resis­tors. These 20k resistors (R

FA

and RFB) are shown in Figure
2 and they set each input amplifier’s gain to -1. Use Equation
7 to determine the input and feedback resistor values for a
desired gain.

-A

v=RF/RIN

(8)

Adjusting the input amplifier’s gain sets the minimum gain for
that channel. Although the single ended output of the Bridge
Output Amplifiers can be used to drive line level outputs, it is
recommended that the A & B Dock Outputs simpler signal
path be used for better performance.

LM4841

www.national.com17

Application Information (Continued)

BEEP DETECT FUNCTION

Computers and notebooks produce a system “beep“ signal
that drives a small speaker. The speaker’s auditory output
signifies that the system requires user attention or input. To
accommodate this system alert signal, the LM4841’s beep
input pin is a mono input that accepts the beep signal.
Internal level detection circuitry at this input monitors the
beep signal’s magnitude. When a signal level greater than
V

DD

/2 is detected on the BEEP IN pin, the bridge output
amplifiers are enabled. The beep signal is amplified and
applied to the load connected to the output amplifiers. A valid
beep signal will be applied to the load even when MUTE is
active. Use the input resistors connected between the BEEP
IN pin and the stereo input pins to accommodate different
beep signal amplitudes. These resistors are shown as
200kΩ devices in Figure 2. Use higher value resistors to
reduce the gain applied to the beep signal. The resistors
must be used to pass the beep signal to the stereo inputs.
The BEEP IN pin is used only to detect the beep signal’s
magnitude: it does not pass the signal to the output amplifi­ers. The LM4841’s shutdown mode must be deactivated
before a system alert signal is applied to BEEP IN pin.

MICRO-POWER SHUTDOWN

The voltage applied to the SHUTDOWN pin controls the
LM4841’s shutdown function. Activate micro-power shut­down by applying ground (logic low) to the SHUTDOWN pin.

When activated, the LM4841’s micro-power shutdown fea­ture turns off the amplifier’s bias circuitry, reducing the sup­ply current. On the demo board, the micro-power shutdown
feature is controlled by a single pole switch that connects the
shutdown pin to either V

DD

, for normal operation, or directly
to ground to enable shutdown. In a system with a micropro­cessor or a microcontroller, use a digital output to apply the
control voltage to the SHUTDOWN pin.

MODE FUNCTION

The LM4841’s MODE function has 2 states controlled by the
voltage applied to the MODE pin. In Mode 0 (mode pin at
GND), the HP Sense has no effect on the gain setting (only
the Gain Select Input Controls either internal or external
gain). In Mode 1 (mode pin tied high), the HP Sense and
Gain Select both can toggle between Internal and External
Gain. See ’Truth Table for Logic Inputs’ on page 5.

MUTE FUNCTION

The LM4841 mutes the amplifier and DOCK outputs when
V

DD

is applied to the MUTE pin. Even while muted, the
LM4841 will amplify a system alert (beep) signal whose
magnitude satisfies the BEEP DETECT circuitry. Applying
0V to the MUTE pin returns the LM4841 to normal, unmuted
operation. Prevent unanticipated mute behavior by connect­ing the MUTE pin to V

DD

or ground. Do not let the mute pin

float.

20028087

FIGURE 5. Headphone Sensing Circuit (MT & MH Packages)

LM4841

www.national.com 18

Application Information (Continued)

CAP-LESS HEADPHONE (SINGLE-ENDED) AMPLIFIER
OPERATION

An internal pull−up circuit is connected to the HP Sense (Pin
21 HP-IN) headphone amplifier control pin. When this pin is
left unconnected, V

DD

is applied to the HP−IN. This turns off
Amp B +OUT (not seen in Fig 5, see Fig 2 Pin 15) and
switches Amp A +OUT’s input signal from an audio signal to
the V

DD

/2 voltage present on pin 28 (Amp A + OUT). The
result is muted bridge-connected loads. Quiescent current
consumption is reduced when the IC is in this single−ended
mode.

Figure 5 above shows the implementation of the LM4841’s
headphone control function. An internal comparator with a
nominal 400mV offset monitors the signal present at the

−OUT B output. It compares this signal against the signal
applied to the HP−IN pin (Notice in Figure 5, Pin 21 is
shorted to Pin 17 without a headphone plugged in). When
these signals are equal, as in the case when a BTL is
connected to the amplifier, an internal comparator forces the
LM4841 to maintain bridged−amplifier operation. When the
HP−IN pin is externally floated, such as when headphones
are connected to the jack shown in Figure 5, an internal
pull−up forces V

DD

on the internal comparator’s HP−IN in­puts. This changes the comparator’s output state and en­ables the headphone function: it turns off Amp B +OUT (not
seen in Fig 5, see Fig 2 Pin 15), switches the Amp A +OUT

input signal from an audio signal to the V

DD

/2 DC voltage
present on pin 28, and mutes the bridge-connected loads.
Amp A -OUT and Amp B -OUT drive the headphones.

Figures 2 and 6 also show suggested headphone jack elec­trical connections. The jack is designed to mate with a
three−wire plug. The plug’s tip and ring should each carry
one of the two stereo output signals, whereas the sleeve
provides the return to Amp A +OUT. A headphone jack with
one control pin contact is sufficient to drive the HP−IN pin
when connecting headphones

A switch can replace the headphone jack contact pin. When
a switch shorts the HP−IN pin to V

DD

(An open switch
contact will accomplish this because there is an internal
pull-up resistor), the bridge−connected speakers are muted
and Amp A -OUT and Amp B -OUT drive the stereo head­phones. When a switch shorts the HP−IN pin to GND (pulling
down the internal pull-up resistor), the LM4841 operates in
bridge mode. If headphone drive is not needed, short the
HP−IN pin to the −OUTB pin.

ESD Protection

As stated in the Absolute Maximum Ratings, pin 28 on the
MT/MH packages and pin 25 on the LQ package, have a
maximum ESD susceptibility rating of 6500V. For higher
ESD voltages, the addition of a PCDN042 dual transil (from
California Micro Devices), as shown in Figure 6, will provide
additional protection.

GAIN SELECT FUNCTION (Bass Boost)

The LM4841 features selectable gain, using either internal or
external feedback resistors. Either set of feedback resistors
set the gain of the output amplifiers. The voltage applied to
the GAIN SELECT pin controls which gain is selected. Ap­plying V

DD

to the GAIN SELECT pin selects the external gain
mode. Applying 0V to the GAIN SELECT pin selects the
internally set unity gain.

In some cases a designer may want to improve the low
frequency response of the bridged amplifier or incorporate a
bass boost feature. This bass boost can be useful in systems
where speakers are housed in small enclosures. A resistor,
R

BA

, and a capacitor, CBA, in parallel, can be placed in series
with the feedback resistor of the bridged amplifier as seen in
Figure 7.

20028094

FIGURE 6. The PCDN042 provides additional ESD protection beyond the 6500V shown in the

Absolute Maximum Ratings for the AMP2A output

LM4841

www.national.com19

Application Information (Continued)

At low, frequencies C

BA

is a virtual open circuit and at high

frequencies, its nearly zero ohm impedance shorts R

BA

. The
result is increased bridge-amplifier gain at low frequencies.
The combination of R

BA

and CBAform a -6dB corner fre-

quency at

f

C

= 1/(2πRBACBA) (9)

The bridged-amplifier low frequency differential gain is:

A

VD

= 2(R

GFA+RBA

)/R

GIA

(10)

Using the component values shown in Figure 2 (R

GFA

=

20kΩ,R

BA

= 20kΩ, and CBA= 0.068µF), a first-order, -6dB

pole is created at 120Hz. Assuming R

GIA

= 20kΩ, the low

frequency differential gain is 4. The input (C

in A and B

) capaci­tor values must be selected for a low frequency response
that covers the range of frequencies affected by the desired
bass-boost operation.

DC VOLUME CONTROL

The LM4841 has an internal stereo volume control whose
setting is a function of the DC voltage applied to the DC VOL
CONTROL pin.

The LM4841 volume control consists of 31 steps that are
individually selected by a variable DC voltage level on the
volume control pin. The range of the steps, controlled by the
DC voltage, are from 0dB - 78dB. Each gain step corre­sponds to a specific input voltage range, as shown in table 2,
(on the following page.)

To minimize the effect of noise on the volume control pin,
which can affect the selected gain level, hysteresis has been
implemented. The amount of hysteresis corresponds to half
of the step width, as shown in Volume Control Characteriza­tion Graph (DS200133-40).

For highest accuracy, the voltage shown in the ’recom­mended voltage’ column of the table is used to select a
desired gain. This recommended voltage is exactly halfway
between the two nearest transitions to the next highest or
next lowest gain levels.

The gain levels are 1dB/step from 0dB to -6dB, 2dB/step
from -6dB to -36dB, 3dB/step from -36dB to -47dB, 4dB/step
from -47db to -51dB, 5dB/step from -51dB to -66dB, and
12dB to the last step at -78dB.

20028011

FIGURE 7. Low Frequency Enhancement ( MT/MH PINOUT )

LM4841

www.national.com 20

Application Information (Continued)

VOLUME CONTROL TABLE ( Table 2 )

Gain
(dB)

Voltage Range (% of Vdd) Voltage Range (Vdd = 5) Voltage Range (Vdd = 3)

Low High Recommended Low High Recommended Low High Recommended

0 77.5% 100.00% 100.000% 3.875 5.000 5.000 2.325 3.000 3.000

-1 75.0% 78.5% 76.875% 3.750 3.938 3.844 2.250 2.363 2.306

-2 72.5% 76.25% 74.375% 3.625 3.813 3.719 2.175 2.288 2.231

-3 70.0% 73.75% 71.875% 3.500 3.688 3.594 2.100 2.213 2.156

-4 67.5% 71.25% 69.375% 3.375 3.563 3.469 2.025 2.138 2.081

-5 65.0% 68.75% 66.875% 3.250 3.438 3.344 1.950 2.063 2.006

-6 62.5% 66.25% 64.375% 3.125 3.313 3.219 1.875 1.988 1.931

-8 60.0% 63.75% 61.875% 3.000 3.188 3.094 1.800 1.913 1.856

-10 57.5% 61.25% 59.375% 2.875 3.063 2.969 1.725 1.838 1.781

-12 55.0% 58.75% 56.875% 2.750 2.938 2.844 1.650 1.763 1.706

-14 52.5% 56.25% 54.375% 2.625 2.813 2.719 1.575 1.688 1.631

-16 50.0% 53.75% 51.875% 2.500 2.688 2.594 1.500 1.613 1.556

-18 47.5% 51.25% 49.375% 2.375 2.563 2.469 1.425 1.538 1.481

-20 45.0% 48.75% 46.875% 2.250 2.438 2.344 1.350 1.463 1.406

-22 42.5% 46.25% 44.375% 2.125 2.313 2.219 1.275 1.388 1.331

-24 40.0% 43.75% 41.875% 2.000 2.188 2.094 1.200 1.313 1.256

-26 37.5% 41.25% 39.375% 1.875 2.063 1.969 1.125 1.238 1.181

-28 35.0% 38.75% 36.875% 1.750 1.938 1.844 1.050 1.163 1.106

-30 32.5% 36.25% 34.375% 1.625 1.813 1.719 0.975 1.088 1.031

-32 30.0% 33.75% 31.875% 1.500 1.688 1.594 0.900 1.013 0.956

-34 27.5% 31.25% 29.375% 1.375 1.563 1.469 0.825 0.937 0.881

-36 25.0% 28.75% 26.875% 1.250 1.438 1.344 0.750 0.862 0.806

-39 22.5% 26.25% 24.375% 1.125 1.313 1.219 0.675 0.787 0.731

-42 20.0% 23.75% 21.875% 1.000 1.188 1.094 0.600 0.712 0.656

-45 17.5% 21.25% 19.375% 0.875 1.063 0.969 0.525 0.637 0.581

-47 15.0% 18.75% 16.875% 0.750 0.937 0.844 0.450 0.562 0.506

-51 12.5% 16.25% 14.375% 0.625 0.812 0.719 0.375 0.487 0.431

-56 10.0% 13.75% 11.875% 0.500 0.687 0.594 0.300 0.412 0.356

-61 7.5% 11.25% 9.375% 0.375 0.562 0.469 0.225 0.337 0.281

-66 5.0% 8.75% 6.875% 0.250 0.437 0.344 0.150 0.262 0.206

-78 0.0% 6.25% 0.000% 0.000 0.312 0.000 0.000 0.187 0.000

LM4841

www.national.com21

Application Information (Continued)

AUDIO POWER AMPLIFIER DESIGN

Audio Amplifier Design: Driving 1W into an 8Ω Load

The following are the desired operational parameters:

Power Output: 1 W

RMS

Load Impedance: 8Ω

Input Level: 1 V

RMS

Input Impedance: 20 kΩ

Bandwidth: 100 Hz−20 kHz

±

0.25 dB

The design begins by specifying the minimum supply voltage
necessary to obtain the specified output power. One way to
find the minimum supply voltage is to use the Output Power
vs Supply Voltage curve in the Typical Performance Char-
acteristics section. Another way, using Equation (10), is to
calculate the peak output voltage necessary to achieve the
desired output power for a given load impedance. To ac­count for the amplifier’s dropout voltage, two additional volt­ages, based on the Dropout Voltage vs Supply Voltage in the
Typical Performance Characteristics curves, must be
added to the result obtained by Equation (10). The result is
Equation (11).

(11)

VDD≥ (V

OUTPEAK

+(V

OD

TOP

+V

OD

BOT

)) (12)

The Output Power vs Supply Voltage graph for an 8Ω load
indicates a minimum supply voltage of 4.6V. This is easily
met by the commonly used 5V supply voltage. The additional
voltage creates the benefit of headroom, allowing the
LM4841 to produce peak output power in excess of 1W
without clipping or other audible distortion. The choice of
supply voltage must also not create a situation that violates
of maximum power dissipation as explained above in the
Power Dissipation section.

After satisfying the LM4841’s power dissipation require­ments, the minimum differential gain needed to achieve 1W
dissipation in an 8Ω load is found using Equation (12).

(13)

Thus, a minimum overall gain of 2.83 allows the LM4841’s to
reach full output swing and maintain low noise and THD+N
performance.

The last step in this design example is setting the amplifier’s

−6dB frequency bandwidth. To achieve the desired

±

0.25dB
pass band magnitude variation limit, the low frequency re­sponse must extend to at least one-fifth the lower bandwidth
limit and the high frequency response must extend to at least
five times the upper bandwidth limit. The gain variation for
both response limits is 0.17dB, well within the

±

0.25dB
desired limit. The results are an

f

L

= 100Hz/5 = 20Hz (14)

and an

f

H

= 20kHz x 5 = 100kHz (15)

As mentioned in the Selecting Proper External Compo-
nents section, R

in A and B

and C

in A and B

create a highpass
filter that sets the amplifier’s lower bandpass frequency limit.
Find the input coupling capacitor’s value using Equation
(14).

C

in A and B

≥ 1/(2πR

in A and BfL

) (16)

The result is

1/(2π

*

20kΩ*20Hz) = 0.397µF (17)

Use a 0.39µF capacitor, the closest standard value.

The product of the desired high frequency cutoff (100kHz in
this example) and the differential gain A

VD

, determines the

upper passband response limit. With A

VD

= 3 and fH=
100kHz, the closed-loop gain bandwidth product (GBWP) is
300kHz. This is less than the LM4841’s 3.5MHz GBWP. With
this margin, the amplifier can be used in designs that require
more differential gain while avoiding performance,restricting
bandwidth limitations.

Recommended Printed Circuit
Board Layout

Figures 8 through 14 show the recommended PC board
layout that is optimized for the LM4841 and associated
external components. This circuit is designed for use with an
external 5V supply and 8Ω speakers.

This circuit board is easy to use. Apply 5V and ground to the
board’s V

DD

and GND pads, respectively. Connect 8Ω

speakers between the board’s −OUTA and +OUTA and

-OUTB and +OUTB pads.

LM4841

www.national.com 22

LM4841LQ Demo Board Artworks

20028098

FIGURE 8. Top Layer SilkScreen

20028099

FIGURE 9. Top Layer LQ

LM4841

www.national.com23

LM4841LQ Demo Board Artworks (Continued)

200280A0

FIGURE 10. Bottom Layer LQ

LM4841

www.national.com 24

Analog Audio LM4841LQ Eval Board

Assembly Part Number: 5510118313-001

Revision: A

Bill of Material

Item Part Number Part Description Qty Ref Designator Remark

1 551011373-001 LM4841 Eval Board PCB

etch 001

1

10 482911373-001 LM4841LQ 1

20 151911368-001 Cer Cap 0.068µF 50V

10% 1206

2 CBA, CBB

25 152911368-001 Tant Cap 0.1µF 10V 10%

Size = A 3216

3 C2, C3, C4

26 152911368-002 Tant Cap 0.33µF 10V

10% Size = A 3216

3 CinA, CinB, Cinbeep

27 152911368-003 Tant Cap 1µF 16V 10%

Size = A 3216

3C

BYP

, CoutA, CoutB

28 152911368-004 Tant Cap 10µF 10V 10%

Size = C 6032

1C1

31 472911368-002 Res 20K Ohm 1/8W 1%

1206

10 R

INAandB,RGFAandB

, RBA,

RBB, R

GIAandB,RFAandB

33 472911368-004 Res 200K Ohm 1/16W

1% 0603

2R

BeepAandB

40 131911368-001 Stereo Headphone Jack

W/ Switch

1 Switchcraft 35RAPC4BH3

41 131911368-002 Slide Switch 4 mute, mode, Gain, SD Mouser # 10SP003

42 131911368-003 Potentiometer 1 Volume Control Mouser # 317-2090-100K

43 131911368-004 RCA Jack 3 InA, InB, BeepIn Mouser # 16PJ097

44 131911368-005 Banana Jack, Black 3 GND, AOUT-, BOUT- Mouser # ME164-6219

45 131911368-006 Banana Jack, Red 3 VDD, AOUT+, BOUT+ Mouser # ME164-6218

LM4841

www.national.com25

LM4841 MT & MH Demo Board Artworks

20028088

FIGURE 11. Top Layer SilkScreen

20028089

FIGURE 12. Top Layer TSSOP

LM4841

www.national.com 26

LM4841 MT & MH Demo Board Artworks (Continued)

20028090

FIGURE 13. Bottom Layer TSSOP

20028091

FIGURE 14. Drill Drawing

LM4841

www.national.com27

Analog Audio LM4841 MSOP Eval Board

Assembly Part Number: 980011373-100

Revision: A

Bill of Material

Item Part Number Part Description Qty Ref Designator Remark

1 551011373-001 LM4841 Eval Board PCB

etch 001

1

10 482911373-001 LM4841 MSOP 1

20 151911368-001 Cer Cap 0.068µF 50V

10% 1206

2 CBA, CBB

25 152911368-001 Tant Cap 0.1µF 10V 10%

Size = A 3216

3 C2, C3, C4

26 152911368-002 Tant Cap 0.33µF 10V

10% Size = A 3216

3 CinA, CinB, Cinbeep

27 152911368-003 Tant Cap 1µF 16V 10%

Size = A 3216

3C

BYP

, CoutA, CoutB

28 152911368-004 Tant Cap 10µF 10V 10%

Size = C 6032

1C1

31 472911368-002 Res 20K Ohm 1/8W 1%

1206

10 R

INAandB,RGFAandB

, RBA,

RBB, R

GIAandB,RFAandB

33 472911368-004 Res 200K Ohm 1/16W

1% 0603

2R

BeepAandB

40 131911368-001 Stereo Headphone Jack

W/ Switch

1 Switchcraft 35RAPC4BH3

41 131911368-002 Slide Switch 4 mute, mode, Gain, SD Mouser # 10SP003

42 131911368-003 Potentiometer 1 Volume Control Mouser # 317-2090-100K

43 131911368-004 RCA Jack 3 InA, InB, BeepIn Mouser # 16PJ097

44 131911368-005 Banana Jack, Black 3 GND, AOUT-, BOUT- Mouser # ME164-6219

45 131911368-006 Banana Jack, Red 3 VDD, AOUT+, BOUT+ Mouser # ME164-6218

LM4841

www.national.com 28

Physical Dimensions inches (millimeters) unless otherwise noted

LLP Package

Order Number LM4841LQ

NS Package Number LQA028A for Exposed-DAP LLP

LM4841

www.national.com29

Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

TSSOP Package

Order Number LM4841MT

NS Package Number MTC28 for TSSOP

LM4841

www.national.com 30

Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

Exposed-DAP TSSOP Package

Order Number LM4841MH

NS Package Number MXA28A for Exposed-DAP TSSOP

LIFE SUPPORT POLICY

NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.

2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.

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Corporation

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www.national.com

LM4841 Stereo 2W Amplifiers with DC Volume Control,Transient Free Outputs, and Cap-less

Headphone Drive

National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.