MUB08A [NSC]

1W, Bypass-Capacitor-less Audio Amplifier with Internal Selectable Gain; 1W ，旁路电容无音频放大器，具有内部可选增益


型号：	MUB08A
厂家：	National Semiconductor
描述：	1W, Bypass-Capacitor-less Audio Amplifier with Internal Selectable Gain 1W ，旁路电容无音频放大器，具有内部可选增益音频放大器
文件：	总15页 (文件大小：466K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

May 2003

LM4906

1W, Bypass-Capacitor-less Audio Amplifier with Internal

Selectable Gain

General Description

Key Specifications

The LM4906 is an audio power amplifier primarily designed

for demanding applications in mobile phones and other por-

table communication device applications. It is capable of

delivering 1W of continuous average power to an 8Ω BTL

load with less than 1% distortion (THD+N) from a +5V power

supply.

Improved PSRR at 217Hz for +3V

71dB

Power Output at +5V, THD+N = 1%, 8Ω

1.0W (typ)

Power Output at +3V, THD+N = 1%, 8Ω 390mW (typ)

Total shutdown power supply current 0.1µA (typ)

The LM4906 is the first National Semiconductor Boomer

Power Amplifier that does not require an external PSRR

bypass capacitor. The LM4906 also has an internal select-

able gain of either 6dB or 12dB. In addition, no output

coupling capacitors or bootstrap capacitors are required

which makes the LM4906 ideally suited for cell phone and

other low voltage portable applications.

Features

n Selectable gain of 6dB (2V/V) or 12dB (4V/V)

n No output or PSRR bypass capacitors required

n Improved “Click and Pop” suppression circuitry

n Very fast turn on time: 5ms (typ)

n Minimum external components

n 2.6 - 5.5V operation

The LM4906 contains advanced pop and click circuitry that

eliminates noise, which would otherwise occur during

turn-on and turn-off transitions.

n BTL output can drive capacitive loads

n Ultra low current shutdown mode (SD Low)

Boomer audio power amplifiers were designed specifically to

provide high quality output power with a minimal amount of

external components. The LM4906 features a low -power

consumption shutdown mode (the part is enabled by pulling

the SD pin high). Additionally, the LM4906 features an inter-

nal thermal shutdown protection mechanism.

Applications

n Portable computers

n Desktop computers

n Multimedia monitors

Typical Application

200571B9

FIGURE 1. Typical Audio Amplifier Application Circuit

Boomer^®is a registered trademark of National Semiconductor Corporation.

DS200571

www.national.com

Connection Diagrams

MSOP Package

MSOP Marking

20057102

200571F1

Top View

Order Number LM4906MM

See NS Package Number MUB08A

Z - Plant Code

X - Date Code

T - Die Traceability

LLP Package

LD Marking

200571F2

Z - Plant Code

XY - Date Code

T - Die Traceability

200571C3

Top View

Order Number LM4906LD

See NS Package Number LDA10B

www.national.com

Absolute Maximum Ratings (Note 2)

Thermal Resistance

θ_JC(MSOP)

θ_JA(MSOP)

θ_JC(LLP)

56˚C/W

190˚C/W

12˚C/W

63˚C/W

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

Supply Voltage (Note 10)

Storage Temperature

6.0V

−65˚C to +150˚C

−0.3V to V_DD+0.3V

Internally Limited

2000V

θ_JA(LLP)

Input Voltage

Operating Ratings

Temperature Range

T_MIN≤ T_A≤ T_MAX

Supply Voltage

Power Dissipation (Notes 3, 11)

ESD Susceptibility (Note 4)

ESD Susceptibility (Note 5)

Junction Temperature

−40˚C ≤ T_A≤ 85˚C

2.6V ≤ V_DD≤ 5.5V

200V

150˚C

Electrical Characteristics V_DD= 5V (Notes 1, 2)

The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. Limits apply for T_A= 25˚C.

LM4906

Units

(Limits)

Symbol

Parameter

Conditions

Typical

Limit

(Note 6)

(Notes 7, 8)

V_IN= 0V, I_o= 0A, No Load

V_IN= 0V, I_o= 0A, 8Ω Load

V_SD= GND

3.5

mA (max)

µA (max)

mV (max)

I_DD

Quiescent Power Supply Current

I_SD

Shutdown Current

0.1

V_OS

Output Offset Voltage

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

P_o

Output Power

1.0

0.9

W (min)

R_L= 8Ω

T_WU

Wake-up time

THD+N

Total Harmonic Distortion+Noise

P_o= 0.4 Wrms; f = 1kHz

V_ripple= 200mV sine p-p

Input terminated with 10Ω

Gain at 6dB

0.2

67 (f =

PSRR

Power Supply Rejection Ratio

217Hz)

70 (f = 1kHz)

1.5

V_SDIH

V_SDIL

Shutdown Voltage Input High

Shutdown Voltage Input Low

SD Pin High = Part On

SD Pin Low = Part Off

V (min)

V (max)

1.3

Electrical Characteristics V_DD= 3V (Notes 1, 2)

The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. Limits apply for T_A= 25˚C.

LM4906

Units

(Limits)

Symbol

Parameter

Conditions

Typical

Limit

(Note 6)

(Notes 7, 8)

V_IN= 0V, I_o= 0A, No Load

V_IN= 0V, I_o= 0A, 8Ω Load

V_SD= GND

2.6

mA (max)

µA (max)

mV (max)

I_DD

Quiescent Power Supply Current

I_SD

Shutdown Current

0.1

V_OS

Output Offset Voltage

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

P_o

Output Power

390

R_L= 8Ω

T_WU

Wake-up time

THD+N

Total Harmonic Distortion+Noise

P_o= 0.15 Wrms; f = 1kHz

V_ripple= 200mV sine p-p

Input terminated with 10Ω

Gain at 6dB

0.1

71 (f =

PSRR

Power Supply Rejection Ratio

217Hz)

73 (f = 1kHz)

1.1

V_SDIH

V_SDIL

Shutdown Voltage Input High

Shutdown Voltage Input Low

SD Pin High = Part On

SD Pin Low = Part Off

V (min)

V (max)

0.9

www.national.com

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

, θ , and the ambient temperature T . The maximum

JMAX JA

allowable power dissipation is P

= (T

–T )/θ or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4906, see power derating

DMAX

JMAX A JA

curves for additional 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.

Note 9: R

is measured from the output pin to ground. This value represents the parallel combination of the 10kΩ output resistors and the two 20kΩ resistors.

OUT

Note 10: If the product is in Shutdown mode and V exceeds 6V (to a max of 8V V ), then most of the excess current will flow through the ESD protection circuits.

If the source impedance limits the current to a max of 10mA, then the device will be protected. If the device is enabled when V is greater than 5.5V and less than

6.5V, no damage will occur, although operation life will be reduced. Operation above 6.5V with no current limit will result in permanent damage.

Note 11: Maximum power dissipation in the device (P

) occurs at an output power level significantly below full output power. P

can be calculated using

DMAX

Equation 1 shown in the Application Information section. It may also be obtained from the power dissipation graphs.

External Components Description

Components

Functional Description

C₂

Input coupling capacitor which blocks the DC voltage at the amplifiers input terminals. Also creates a

highpass filter with R_iat f_c= 1 / (2πR_iC_i). Refer to the section, Proper Selection of External Components,

for an explanation of how to determine the value of C_i.

C₁

Supply 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.

www.national.com

Typical Performance Characteristics

THD+N vs Frequency

V_DD= 5V, R_L= 8Ω,

f = 1kHz, PWR = 500mW

THD+N vs Frequency

V_DD= 3V, R_L= 8Ω,

f = 1kHz, PWR = 250mW

200571C4

200571C5

THD+N vs Power Out

V_DD= 5V, R_L= 8Ω, f = 1kHz

V_DD= 3V, R_L= 8Ω, f = 1kHz

200571C6

200571C7

Power Supply Rejection Ratio

vs Frequency

Power Supply Rejection Ratio

vs Frequency

V_DD= 5V, R_L= 8Ω

V_DD= 3V, R_L= 8Ω

200571E2

200571C9

www.national.com

Typical Performance Characteristics (Continued)

Noise Floor

V_DD= 5V, R_L= 8Ω

80kHz Bandwith, Input to GND

Power Derating Curve

200571E4

200571D0

Power Dissipation

vs Output Power, V_DD= 5V

vs Output Power, V_DD= 3V

200571D2

200571D1

Shutdown Hysteresis Voltage

V_DD= 5V, SD Mode = V_DD(High)

Shutdown Hysteresis Voltage

V_DD= 5V, SD Mode = V_DD(Low)

200571D3

200571D4

www.national.com

Typical Performance Characteristics (Continued)

Shutdown Hysteresis Voltage

V_DD= 3V, SD Mode = V_DD(High)

Shutdown Hysteresis Voltage

V_DD= 3V, SD Mode = GND (Low)

200571E5

200571D6

Output Power

vs Supply Voltage, R_L= 8Ω

vs Supply Voltage, R_L= 16Ω

200571D7

200571D9

Output Power

vs Supply Voltage, R_L= 32Ω

Frequency Response

vs Input Capacitor Size

200571D8

200571F3

www.national.com

Typical Performance Characteristics (Continued)

PSRR Distribution

V_DD= 5V, f = 1kHz, R_L= 8Ω

V_DD= 5V, f = 217Hz, R_L= 8Ω

200571F4

200571F5

PSRR Distribution

V_DD= 3V, f = 1kHz, R_L= 8Ω

V_DD= 3V, f = 217Hz, R_L= 8Ω

200571F6

200571F7

www.national.com

sinking. If T_JMAXstill exceeds 150˚C, then additional

changes must be made. These changes can include re-

duced supply voltage, higher load impedance, or reduced

ambient temperature. Internal power dissipation is a function

of output power. Refer to the Typical Performance Charac-

teristics curves for power dissipation information for differ-

ent output powers and output loading.

Application Information

BRIDGE CONFIGURATION EXPLANATION

As shown in Figure 2, the LM4906 has two internal opera-

tional amplifiers. The first amplifier’s gain is either 6dB or

12dB depending on the gain select input (Low = 6dB, High =

12dB). The second amplifier’s gain is fixed by the two inter-

nal 20kΩ resistors. Figure 2 shows that the output of ampli-

fier one serves as the input to amplifier two which results in

both amplifiers producing signals identical in magnitude, but

out of phase by 180˚. Consequently, the differential gain for

the IC is

POWER SUPPLY BYPASSING

As with any amplifier, proper supply bypassing is critical for

low noise performance and high power supply rejection. The

capacitor location on the power supply pin should be as

close to the device as possible. Typical applications employ

a 5V regulator with 10µF tantalum or electrolytic capacitor

and a ceramic bypass capacitor which aid in supply stability.

This does not eliminate the need for bypassing the supply

nodes of the LM4906.

A_VD= 2 * (20k / 20k) or 2 * (40k / 20k)

By driving the load differentially through outputs Vo1 and

Vo2, an amplifier configuration commonly referred to as

“bridged mode” is established. Bridged mode operation is

different from the classical single-ended amplifier configura-

tion where one side of the load is connected to ground.

TURNING ON THE LM4906

The power supply must first be applied before the application

of an input signal to the device and the ramp time to V_DD

must be less than 4ms, otherwise the wake-up time of the

device will be affected. After applying V_DD, the LM4906 will

turn-on after an initial minimum threshold input signal of

7mV_RMS, resulting in a generated output differential signal.

An input signal of less than 7mV_RMSwill result in a negligible

output voltage. Once the device is turned on, the input signal

can go below the 7mV_RMSwithout shutting the device off. If,

however, SHUTDOWN or V_DDis cycled, the minimum

threshold requirement for the input signal must first be met

again, with V_DDramping first.

A bridge amplifier design has a few distinct advantages over

the single-ended configuration, as it provides differential

drive to the load, thus doubling output swing for a specified

supply voltage. Four times the output power is possible as

compared to a single-ended amplifier under the same con-

ditions. This increase in attainable output power assumes

that the amplifier is not current limited or clipped. In order to

choose an amplifier’s closed-loop gain without causing ex-

cessive clipping, please refer to the Audio Power Amplifier

Design section.

A bridge configuration, such as the one used in LM4906,

also creates a second advantage over single-ended amplifi-

ers. Since the differential outputs, Vo1 and Vo2, are biased

at half-supply, no net DC voltage exists across the load. This

eliminates the need for an output coupling capacitor which is

required in a single supply, single-ended amplifier configura-

tion. Without an output coupling capacitor, the half-supply

bias across the load would result in both increased internal

IC power dissipation and also possible loudspeaker damage.

SHUTDOWN FUNCTION

In order to reduce power consumption while not in use, the

LM4906 contains shutdown circuitry that is used to turn off

the amplifier’s bias circuitry. The device is placed into shut-

down mode by toggling the Shutdown pin Low/ground. The

trigger point for shutdown low is shown as a typical value in

the Supply Current vs Shutdown Voltage graphs in the Typi-

cal Performance Characteristics section. It is best to

switch between ground and supply for maximum perfor-

mance. While the device may be disabled with shutdown

voltages in between ground and supply, the idle current may

be greater than the typical value of 0.1µA. In either case, the

shutdown pin should be tied to a definite voltage to avoid

unwanted state changes.

POWER DISSIPATION

Power dissipation is a major concern when designing a

successful amplifier, whether the amplifier is bridged or

single-ended. A direct consequence of the increased power

delivered to the load by a bridge amplifier is an increase in

internal power dissipation. Since the LM4906 has two opera-

tional amplifiers in one package, the maximum internal

power dissipation is 4 times that of a single-ended amplifier.

The maximum power dissipation for a given application can

be derived from the power dissipation graphs or from Equa-

tion 1.

In many applications, a microcontroller or microprocessor

output is used to control the shutdown circuitry, which pro-

vides a quick, smooth transition to shutdown. Another solu-

tion is to use a single-throw switch in conjunction with an

external pull-up resistor (or pull-down, depending on shut-

down high or low application). This scheme guarantees that

the shutdown pin will not float, thus preventing unwanted

state changes.

P_DMAX= 4 * (V_DD

)

/ (2π²R_L)

(1)

SELECTION OF INPUT CAPACITOR SIZE

It is critical that the maximum junction temperature T_JMAXof

150˚C is not exceeded. T_JMAXcan be determined from the

power derating curves by using P_DMAXand the PC board foil

area. By adding copper foil, the thermal resistance of the

Large input capacitors are both expensive and space hungry

for portable designs. Clearly, a certain sized capacitor is

needed to couple in low frequencies without severe attenu-

ation. But in many cases the speakers used in portable

systems, whether internal or external, have little ability to

reproduce signals below 100Hz to 150Hz. Thus, using a

large input capacitor may not increase actual system perfor-

mance.

application can be reduced from the free air value of θ_JA

resulting in higher P_DMAXvalues without thermal shutdown

protection circuitry being activated. Additional copper foil can

be added to any of the leads connected to the LM4906. It is

especially effective when connected to V_DD, GND, and the

output pins. Refer to the application information on the

LM4906 reference design board for an example of good heat

In addition to system cost and size, click and pop perfor-

mance is effected by the size of the input coupling capacitor,

www.national.com

Extra supply voltage creates headroom that allows the

LM4906 to reproduce peaks in excess of 1W without pro-

ducing audible distortion. At this time, the designer must

make sure that the power supply choice along with the

output impedance does not violate the conditions explained

in the Power Dissipation section.

Application Information (Continued)

C_i.A larger input coupling capacitor requires more charge to

reach its quiescent DC voltage (nominally 1/2 V_DD). This

charge comes from the output via the feedback and is apt to

create pops upon device enable. Thus, by minimizing the

capacitor size based on necessary low frequency response,

turn-on pops can be minimized.

The gain of the LM4906 is internally set at either 6dB or

12dB.

The final design step is to address the bandwidth require-

ments which must be stated as a pair of −3dB frequency

points. Five times away from a −3dB point is 0.17dB down

from passband response which is better than the required

0.25dB specified.

AUDIO POWER AMPLIFIER DESIGN

A 1W/8Ω Audio Amplifier

Given:

Power Output

Load Impedance

Input Level

1 Wrms

f_L= 100Hz / 5 = 20Hz

8Ω

1 Vrms

f_H= 20kHz * 5 = 100kHz

Input Impedance

Bandwidth

20 kΩ

100 Hz–20 kHz 0.25 dB

As stated in the External Components section, R_in(20k) in

conjunction with C₂create a highpass filter.

A designer must first determine the minimum supply rail to

obtain the specified output power. By extrapolating from the

Output Power vs Supply Voltage graphs in the Typical Per-

formance Characteristics section, the supply rail can be

easily found.

C₂≥ 1 / (2π*20kΩ*20Hz) = 0.397µF; use 0.39µF

200571C0

FIGURE 2. REFERENCE DESIGN BOARD SCHEMATIC

www.national.com

Application Information (Continued)

LM4906 MSOP DEMO BOARD ARTWORK

Top Layer

200571E6

Bottom Layer

200571E7

www.national.com

Application Information (Continued)

LM4906 LD DEMO BOARD ARTWORK

Top Layer

200571E8

Bottom Layer

200571E9

www.national.com

Application Information (Continued)

Mono LM4906 Reference Design Boards

Bill of Material

Part Description

LM4906 Audio Amplifier

Quantity

Reference Designator

Tantalum Capcitor, 1µF

Ceramic Capacitor, 0.39µF

Jumper Header Vertical Mount 2X1 0.100“ spacing

J1, J2, Input, Output, V_DD

PCB LAYOUT GUIDELINES

Single-Point Power / Ground Connections

This section provides practical guidelines for mixed signal

PCB layout that involves various digital/analog power and

ground traces. Designers should note that these are only

"rule-of-thumb" recommendations and the actual results will

depend heavily on the final layout.

The analog power traces should be connected to the digital

traces through a single point (link). A "Pi-filter" can be helpful

in minimizing High Frequency noise coupling between the

analog and digital sections. It is further recommended to put

digital and analog power traces over the corresponding digi-

tal and analog ground traces to minimize noise coupling.

GENERAL MIXED SIGNAL LAYOUT

RECOMMENDATION

Placement of Digital and Analog Components

All digital components and high-speed digital signal traces

should be located as far away as possible from analog

components and circuit traces.

Power and Ground Circuits

For 2 layer mixed signal design, it is important to isolate the

digital power and ground trace paths from the analog power

and ground trace paths. Star trace routing techniques (bring-

ing individual traces back to a central point rather than daisy

chaining traces together in a serial manner) can have a

major impact on low level signal performance. Star trace

routing refers to using individual traces to feed power and

ground to each circuit or even device. This technique will

require a greater amount of design time but will not increase

the final price of the board. The only extra parts required will

be some jumpers.

Avoiding Typical Design / Layout Problems

Avoid ground loops or running digital and analog traces

parallel to each other (side-by-side) on the same PCB layer.

When traces must cross over each other do it at 90 degrees.

Running digital and analog traces at 90 degrees to each

other from the top to the bottom side as much as possible will

minimize capacitive noise coupling and cross talk.

www.national.com

Physical Dimensions inches (millimeters) unless otherwise noted

MSOP

Order Number LM4906MM

NS Package Number MUA08A

www.national.com

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

LLP

Order Number LM4906LD

NS Package Number LDA10B

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.

National Semiconductor

Americas Customer

Support Center

National Semiconductor

Europe Customer Support Center

Fax: +49 (0) 180-530 85 86

National Semiconductor

Asia Pacific Customer

Support Center

National Semiconductor

Japan Customer Support Center

Fax: 81-3-5639-7507

Email: new.feedback@nsc.com

Tel: 1-800-272-9959

Email: europe.support@nsc.com

Deutsch Tel: +49 (0) 69 9508 6208

English Tel: +44 (0) 870 24 0 2171

Français Tel: +33 (0) 1 41 91 8790

Email: ap.support@nsc.com

Email: jpn.feedback@nsc.com

Tel: 81-3-5639-7560

www.national.com

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.

MUB08A [NSC]

相关型号：

SI9130DB

SI9135LG-T1

SI9135LG-T1-E3

SI9135_11

SI9136_11

SI9130CG-T1-E3

SI9130LG-T1-E3

SI9130_11

SI9137

SI9137DB

SI9137LG

SI9122E