LM4811_15 [UTC]

DUAL 105mW HEADPHONE AMPLIFIER WITH DIGITAL VOLUME CONTROL;


型号：	LM4811_15
厂家：	Unisonic Technologies
描述：	DUAL 105mW HEADPHONE AMPLIFIER WITH DIGITAL VOLUME CONTROL 放大器
文件：	总9页 (文件大小：204K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

UNISONIC TECHNOLOGIES CO., LTD

LM4811

Preliminary

CMOS IC

DUAL 105mW HEADPHONE

AMPLIFIER WITH DIGITAL

VOLUME CONTROL AND

SHUTDOWN MODE

DESCRIPTION

The UTC LM4811 is a dual audio power amplifier with digital

volume control and shutdown mode function. It is featured in

unity-gain stability. The digital volume control sets the amplifier’s

gain from +12dB to -33dB in 16 discrete steps using a two-wire

interface. The shutdown mode is externally controlled, active-high

and micropower consumption. An internal thermal shutdown

protection circuit is contained in the device.

Operating on a 5V power supply, it can drive 16Ω load at

105mW per channel of continuous average power with 0.1%

(THD+N).

This device is mainly used to provide customers with higher

quality output power but less required external components. The

UTC LM4811 reduces the use of bootstrap capacitors or snubber

networks that make making it ideal for low-power portable systems

applications.

The UTC LM4811 is generally applied in cellular phones, MP3,

CD, DVD players, PDA’s and other portable electronics.

FEATURES

* Digital volume control range: +12dB~ -33dB

* "Click and Pop" suppression circuitry

* Saving the use of bootstrap capacitors

* Low shutdown current

ORDERING INFORMATION

Ordering Number

Lead Free

Package

Packing

Tape Reel

Halogen Free

LM4811G-SM2-R

LM4811L-SM2-R

MSOP-10

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LM4811

Preliminary

CMOS IC

PIN CONFIGURATION

Top View

V_OUT1

V_IN1

V_DD

V_OUT2

Bypass

V_IN2

SHUTDOWN

UP/DN

CLOCK

GND

MSOP-10

PIN DESCRIPTION

PIN NO.

PIN NAME

V_OUT1

DESCRIPTION

Channel 1 output

V_IN1

Channel 1 audio input

Bypass

CLOCK

GND

Connect to internal voltage divider for middle supply bias

External clock input for the volume control

Ground

UP/DN

Volume UP/DOWN control

Shutdown mode control input, high active, place LM4811 into shutdown

mode, when held high

SHUTDOWN

V_IN2

V_OUT2

V_DD

Channel 2 audio input

Channel 2 output

Supply voltage

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LM4811

Preliminary

CMOS IC

BLOCK DIAGRAM

V_DD

V_IN1

V_DD

Shutdown 7

BIAS

V_OUT1

50kΩ

20kΩ

Bypass

V_OUT2

V_IN2

UP/DN

Clock

Digital Volume

Control

GND

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LM4811

Preliminary

CMOS IC

ABSOLUTE MAXIMUM RATING (T_C= 25°C, unless otherwise specified)

PARAMETER

SYMBOL

V_CC

RATINGS

6.0

UNIT

Supply Voltage

Junction Temperature

Storage Temperature

T_J

150

℃

T_STG

-65~ +150

℃

Notes: 1. Absolute maximum ratings are those values beyond which the device could be permanently damaged.

Absolute maximum ratings are stress ratings only and functional device operation is not implied.

THERMAL DATA

PARAMETER

SYMBOL

θ_JA

RATINGS

194

UNIT

°C/W

Junction to Ambient

Junction to Case

θ_JC

OPERATING RATINGS

PARAMETER

SYMBOL

V_CC

RATINGS

2.0 ~ 5.5

-40 ~ 85

UNIT

Supply Voltage

Operating Temperature

T_A

°C

ELECTRICAL CHARACTERISTICS (T_A=25°C, unless otherwise specified) (Note 4, 5)

For V_DD=5V

PARAMETER

SYMBOL

V_DD

TEST CONDITIONS

MIN TYP MAX UNIT

Supply Voltage

2.0

5.5

3.0

Supply Current

I_DD

V_IN=0V, I_O=0A

1.3

0.3

4.0

105

μA

Shutdown Current

Output Offset Voltage

I_SD

V_IN=0V

V_OS

R_L=16Ω

R_L=32Ω

Output Power

P_O

THD+N=0.1%, f=1kHz

Total Harmonic Distortion

Channel Separation

THD+N P_O=50mW, R_L=32Ω, f=20Hz~20kHz

Crosstalk R_L=32Ω, f=1kHz, P_O=70mW

0.3

100

C_B=1.0μF,V_RIPPLE=100mV_PP

f=217Hz

Power Supply Rejection Ratio

PSRR

Input Voltage

(Clock, UP/DN, Shutdown)

High

Low

V_IH

V_IL

1.4

0.4

Input referred minimum gain

Input referred maximum gain

All 16 discrete steps

-33

+12

3.0

Digital Volume Range

Digital Volume Stepsize

Stepsize Error

All 16 discrete steps

±0.3

Channel-to-Channel Volume

Tracking Error

All gain settings from -33dB ~ +12dB

Shutdown mode active

0.15

-100

Shutdown Attenuation

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LM4811

Preliminary

CMOS IC

ELECTRICAL CHARACTERISTICS(Cont.)

For V_DD=3.3V

PARAMETER

SYMBOL

I_DD

I_SD

TEST CONDITIONS

MIN TYP MAX UNIT

Supply Current

V_IN=0V, I_O=0A

V_IN=0V

1.1

0.3

4.0

μA

Shutdown Current

Output Offset Voltage

V_OS

V_IN=0V

R_L=16Ω

R_L=32Ω

Output Power

P_O

THD+N=0.1%, f=1kHz

Total Harmonic Distortion

Power Supply Rejection Ratio

THD+N P_O=25mW, R_L=32Ω, f=20Hz~20kHz

0.5

C_B=1.0μF,V_RIPPLE=100mV_PP

PSRR

f=217Hz

Input Voltage

(Clock, UP/DN, Shutdown)

High

V_IH

V_IL

1.4

Low

0.4

Input referred minimum gain

Input referred maximum gain

All 16 discrete steps

-33

+12

3.0

Digital Volume Range

Digital Volume Stepsize

Stepsize Error

All 16 discrete steps

±0.3

Channel-to-Channel Volume

Tracking Error

All gain settings from -33dB ~ +12dB

Shutdown mode active

0.15

-100

Shutdown Attenuation

For V_DD=2.6V

PARAMETER

SYMBOL

I_DD

TEST CONDITIONS

V_IN=0V, I_O=0A

V_IN=0V

MIN TYP MAX UNIT

Supply Current

Shutdown Current

Output Offset Voltage

1.0

0.3

4.0

μA

I_SD

V_OS

V_IN=0V

R_L=16Ω

THD+N=0.1%, f=1kHz

R_L=32Ω

Output Power

P_O

Total Harmonic Distortion

Power Supply Rejection Ratio

THD+N P_O=15mW, R_L=32Ω, f=20Hz~20kHz

0.6

C_B=1.0μF,V_RIPPLE=100mV_PP

PSRR

f=217Hz

Input Voltage

(Clock, UP/DN, Shutdown)

High

V_IH

V_IL

1.4

Low

0.4

Input referred minimum gain

Input referred maximum gain

All 16 discrete steps

-33

+12

3.0

Digital Volume Range

Digital Volume Stepsize

Stepsize Error

All 16 discrete steps

±0.3

Channel-to-Channel Volume

Tracking Error

All gain settings from -33dB ~ +12dB

0.15

Shutdown Attenuation

Shutdown mode active

-75

Notes: 4. Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.

5. All voltages are measured with respect to the ground pin, unless otherwise specified.

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LM4811

Preliminary

CMOS IC

APPLICATION INFORMATION

DIGITAL VOLUME CONTROL

The UTC LM4811 is dual audio power amplifier with digital volume control and shutdown mode function. The

CLOCK pin is drived by an external clock. It’ s gain is controlled by the signals applied to the CLOCK and UP/DN

inputs.

The audio power amplifier’s gain is fixed by the signals, which are applied to the CLOCK and UP/DN inputs. The

gain is controlled by the logic voltage level applied to the UP/DN pin at each rising edge of the clock signal. At each

rising edge of the clock signal, when a logic high voltage level is applying to the UP/DN pin, 3dB is increased, in

verse when a logic low voltage is applying to the UP/DN pin, 3dB is decreased on the contrary. For both the CLOCK

and UP/DN inputs, the trigger point is 1.4V (MIN.) for a logic high level, and 0.4V (MAX.) for a logic low level.

The UTC LM4811 contains16 discrete gain settings varying from +12dB (MAX.) to -33dB (MIN.), amplifier’s gain

is set to a default value of 0dB during power on condition. However, when coming out of shutdown mode, the UTC

LM4811 will revert back to its previous gain setting.

In order to avoid undesired state changes during transitions between V_ILand V_IH, the UTC LM4811’s CLOCK

and UP/DN pins should be debounced. This will ensure correct operation of the digital volume control. A

microcontroller or microprocessor output is expected to drive the CLOCK and UP/DN pins.

UP/DN

CLOCK

VOLUME

Default

Down

Figure 2. Timing Diagram

POWER SUPPLY BYPASSING

To obtain low noise performance and high power supply rejection, proper supply bypassing is essentially

needed for any power amplifier. Capacitor on both the bypass and power supply pins should be placed closely as

possible. Bypass capacitor value is also critical as it directly affects the device’s half-supply voltage stability and

PSRR. The stability and supply rejection increase as the bypass capacitor’s value increases. In the typical

applications, employing a 5V regulator with 10μF and a 0.1μF bypass capacitors which aid in supply stability. This,

however, is not saving the need for bypassing the supply nodes of the UTC LM4811. The issue of selecting bypass

capacitors, especially C_B, is thus dependent upon desired low frequency PSRR, click and pop performance, system

cost, and size constraints.

SHUTDOWN FUNCTION

The UTC LM4811 contains a bias circuitry shutdown to reduce power consumption while not is use. By applying

a logic high to the SHUTDOWN pin, the shutdown function is active. For a logic high level, the trigger point is 1.4V

(MIN.), and 0.4V (MAX.) for a logic low. For a better shutdown performance, it is best to switch between ground and

V_DD. By switching the SHUTDOWN pin to V_DD, the UTC LM4811 supply current draw will be minimized in idle mode.

Whereas the device will be disabled with shutdown voltages less than V_DD, the idle current may be greater than

0.3μA (TYP.). In either case, the SHUTDOWN pin should be tied to a fixed voltage to avoid undesired state changes.

In many applications, a microcontroller or microprocessor output is used to control the shutdown circuitry. This

provides a quick, smooth shutdown transition. Another solution is to use a single-pole, single-throw switch in

conjunction with an external pull-up resistor. When the switch is closed, the SHUTDOWN pin is connected to ground

and enables the amplifier. If the switch is open, the external pull-up resistor, R_PU, will disable the UTC LM4811. This

scheme guarantees that the SHUTDOWN pin will not float, thus preventing undesired state changes.

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LM4811

Preliminary

CMOS IC

APPLICATION INFORMATION(Cont.)

PROPER SELECTION OF EXTERNAL COMPONENTS

In applications, selection of external components when using integrated power amplifiers is critical for optimum

device and system performance. Moreover, the vales of external components are also important to consider as they

directly affect the overall system quality. The UTC LM4811 is tolerant to a variety external component combinations.

The UTC LM4811 is unity-gain stable, providing designers maximize system performance. Low gain settings

maximize signal-to-noise performance and minimizes THD+N. Low gain configurations require large input signals to

obtain a given output power. Input signals reach 1Vrms or higher are available from sources such as audio codecs.

SELECTION OF INPUT AND OUTPUT CAPACITOR SIZE

Another consideration is the closed loop bandwidth besides gain. To a large extent, the bandwidth is dicated by

the choice of external components shown in Figure 1. Both the C_I(input coupling capacitor) and the C_O(output

coupling capacitor) form first order high pass filters which limit low frequency response. The values of these

capacitors should be based on the desired frequency response weighed against the following:

Large value input and output capacitors are both expensive and space consuming for portable designs. Clearly

a certain sized capacitor is needed to couple in low frequencies without severe attenuation. But in many cases the

speakers used in portable systems, whether internal or external, have little ability to reproduce signals below 150Hz.

Thus large input and output capacitors may not increase system performance.

Moreover, for the system cost and size, click and pop performance is affected by the size of the C_I(input

coupling capacitor). 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 the pops are apt to be generated upon

device enable. Reducing the value of input coupling capacitor can minimize the turn on pops, which is based on

necessary low frequency response.

The value of bypass capacitor should be taken into consideration besides minimizing the input and output

capacitor values. For minimizing turn on pops, the bypass capacitor C_Bplays the most important role, since it

determines how fast the UTC LM4811 turns on. The slower the UTC LM4811’s outputs ramp to their quiescent DC

voltage (nominally 1/2 V_DD), the smaller the turn on pop. While the device will function properly, (no oscillations or

motorboating), with C_Bequal to 1μF, the device will be much more susceptible to turn on clicks and pops. Thus, a

value of C_Bequal to 1μF or larger is recommended in all but the most cost sensitive designs.

In addition, the type of capacitors should be given enough consideration since different types of capacitors

(tantalum, electrolytic, ceramic) have unique performance characteristics and may affect overall system

performance.

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LM4811

Preliminary

CMOS IC

TYPICAL APPLICATION CIRCUIT

V_DD

C_S

1μF

C_I

1μF

V_IN1

Audio

Input

V_DD

50kΩ

R_PU

100kΩ

V_OUT1

Shutdown

C_O

100μF

BIAS

20kΩ

Bypass

C_B

50kΩ

V_OUT2

1μF

C_O

100μF

C_I

1μF

V_IN2

Audio

Input

UP/DN

Clock

Digital Volume

Control

V_DD

GND

V_DD

R_P

100Ω

R_PD

100Ω

C_P

0.1μF

* Refer to the Application Information Section for information concerning proper selection of the input and output

coupling capacitors.

Figure 1. Typical Audio Amplifier Application Circuit

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LM4811

Preliminary

CMOS IC

EXTERNAL COMPONENTS DESCRIPTION

PIN NO.

PIN NAME

DESCRIPTION

This is the input coupling capacitor. It blocks the DC voltage at, and couples the input

signal to, the amplifier’s input terminals. C also creates a highpass filter with the internal

input resistor, R_I, at f_C=1/(2πR_IC_I). The minimum value of R_Iis 33kΩ. Refer to the

section, Proper Selection of External Components, for an explanation of how to

determine the value of C_I.

C_I

This is the supply bypass capacitor. It provides power supply filtering. Refer to the

Application Information section for proper placement and selection of the supply

bypass capacitor.

C_S

This is the BYPASS pin capacitor. It provides half-supply filtering. Refer to the section,

Proper Selection of External Components, for information concerning proper

placement and selection of C_B.

C_B

C_O

This is the output coupling capacitor. It blocks the DC voltage at the amplifier’s output

and it forms a high pass filter with R_Lat fO = 1/(2πR_LC_o)

UTC assumes no responsibility for equipment failures that result from using products at values that

exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or

other parameters) listed in products specifications of any and all UTC products described or contained

herein. UTC products are not designed for use in life support appliances, devices or systems where

malfunction of these products can be reasonably expected to result in personal injury. Reproduction in

whole or in part is prohibited without the prior written consent of the copyright owner. The information

presented in this document does not form part of any quotation or contract, is believed to be accurate

and reliable and may be changed without notice.

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LM4811_15 [UTC]

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