HM4990A [HMSEMI]

1.25W Mono Audio Power Amplifier;


型号：	HM4990A
厂家：	H&M Semiconductor
描述：	1.25W Mono Audio Power Amplifier
文件：	总12页 (文件大小：841K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

HM4990

1.25W Mono Audio Power Amplifier

GENERAL DESCRIPTION

FEATURES

The HM4990 is a mono Class-AB audio power amplifier . Ultra low current in shutdown mode

designed for demanding applications in mobile

. Low quiescent current

phones and other portable media devices. It is

. Improved pop & click circuitry eliminates noise

capable of delivering 1.25W of continuous output

during turn-on and turn-off transitions

power to an 8Ω BTL load with less than 1% distortion

. Supports both single-end and differential inputs

(THD+N) from a 5VDC power supply.

. Wide operating voltage range: 2.5 ~ 5.5V

The HM4990 is specifically designed to provide high

. No output coupling capacitors, snubber networks

quality output power with a minimal number of

or bootstrap capacitors required

external components. The HM4990 does not require

output coupling capacitors or bootstrap capacitors,

and is therefore ideal for use in mobile phones and

other low voltage applications where minimal power

consumption is a primary requirement.

. Available in space-saving package

COL1.5X1.5-9L

MSOP-8L

KEY SPECIFICATIONS

The HM4990 features a low-power shutdown mode. In

the shutdown mode where a logic low is applied onto

the SD pin, the amplifier is completely turned off and

no supply current will flow through the device.

. Improved PSRR at 217Hz : 66dB

. Power Output at 5V, 1% THD+N, 8Ω: 1.25W

. Power Output at 3V, 1% THD+N, 8Ω: 425mW

. Quiescent Current 1.6mA (VDD=3V)

The HM4990 also features advanced pop & click

circuitry which eliminates noise which would

otherwise occur during turn-on and turn-off

transitions.

APPLICATIONS

. Mobile phone

. PDA

The HM4990 is unity-gain stable and can be configured

by external gain-setting resistors.

. Portable electronic devices

APPLICATION CIRCUIT

Figure 1: Typical Audio Amplifier Application Circuit

HM4990

PIN CONFIGURATION AND DESCRIPTION

HM4990A

HM4990M

QFN1.5X1.5-9L

MSOP-8L

SYMBOL

V_DD

QFN9

MSOP8

DESCRIPTION

Power supply

Active low shutdown control

-IN

Negative differential input

Positive differential input

Negative BTL output

Positive BTL output

+IN

VO1

VO2

BYPASS

GND

Bypass capacitor pin which provides the common mode voltage

Ground

B1 & B2

ORDERING INFORMATION

PART NUMBER

TEMPERATURE RANGE

PACKAGE

GAIN (dB)

HM4990A

HM4990M

-40°C to +85°C

COL1.5X1.5-9L

MSOP-8L

Adjustable

HM4990

ABSOLUTE MAXIMUM RATINGS

PARAMETER

VALUE

Supply voltage, VDD

-0.3V to 6.0V

−0.3V to VDD+0.3V

−65°C to +150°C

Internally Limited

2000V

All other pins

Storage temperature

Power dissipation

ESD ratings - Human Body Model ( HBM)

Junction temperature

150°C

θ_JC

56°C/W

θ_JA

190°C/W

Maximum soldering temperature (@10 sec duration)

260°C

Note: Stresses beyond those listed under absolute maximun ratings may cause permanent damage to the device. These are stress ratings only,and

functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not

implied.Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

RECOMMENDED OPERATING CONDITIONS

CONDITIONS

MIN

2.5

-40

6.4

TYP

MAX

UNIT

PARAMETER

Supply voltage，VDD

Operating free-air temperature, T_A

Load impedance, Z_L

5.5

°C

Ω

HM4990

ELECTRICAL CHARACTERISTICS

VDD=5V.

The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. Limits apply for

TA=25°C.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNIT

VIN=0V, IO=0A, No Load

VIN=0V, IO=0A, 8Ω Load

V_SD= 0

2.5

μA

I_DD

Quiescent current

I_SD

Shutdown current

0.1

2.0

V_OS

Output offset voltage

SD pin HIGH input voltage

SD pin LOW input voltage

V_SDIH

V_SDIL

1.5

0.9

0.5

R_OUT

Resistor output to GND

kΩ

P_O

Output power (8Ω)

THD+N=1%，f=1KHz

1.25

130

0.2

T_WU

Wake-up time

CB=1uF

THD+N

Total Harmonic Distortion+Noise PO = 0.5Wrms; f=1KHz

_ripple=200mV sine p-p

Input grounded, f=217HZ

V_ripple=200mV sine p-p

Input grounded, f=1KHZ

PSRR

Power Supply Rejection Ratio

VDD=3V.

The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. Limits apply for

TA=25°C.

MIN

SYMBOL

PARAMETER

CONDITIONS

TYP

MAX

UNIT

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

V_IN=0V, I_O=0A, 8Ω Load

V_SD= 0

1.6

μA

I_DD

Quiescent current

I_SD

Shutdown current

0.1

2.0

V_OS

Output offset voltage

SD pin HIGH input voltage

SD pin LOW input voltage

Resistor output to GND

Output power (8Ω)

V_SDIH

V_SDIL

R_OUT

P_O

1.3

0.4

KΩ

THD+N=1%， f=1KHz

C_B=1uF

425

130

0.16

T_WU

Wake-up time

THD+N

Total Harmonic Distortion+Noise

P_O= 0.25Wrms; f=1KHz

_ripple=200mV sine p-p

Input grounded, f=217Hz

V_ripple=200mV sine p-p

Input grounded, f=1KHz

PSRR

Power Supply Rejection Ratio

HM4990

TYPICAL PERFORMANCE CHARACTERISTICS

THD+N vs Outpout Power

VDD=3V, RL=8Ω

VDD=5V, RL=8Ω

0.1

100

1000

100

1000

10000

Output Power(mW)

Figure 2

Figure 3

THD+N vs Frequency

0.1

VDD=5V,RL=8Ω,Po=800mW

VDD=3V,RL=8Ω,Po=250mW

0.01

100

1000

10000

100000

100

1000

10000

100000

Frequency(Hz)

Figure 4

Figure 5

Output Power vs Supply Voltage

1800

2000

1800

1600

1400

1200

1000

800

1600

1400

1200

1000

800

600

400

200

600

RL=8Ω,THD+N=10%

400

RL=8Ω,THD+N=1%

200

2.5

3.5

4.5

5.5

2.5

3.5

4.5

5.5

Supply Voltage(V)

Figure 6

Figure 7

HM4990

Power Dissipation vs Output Power

250

200

150

100

700

600

500

400

300

200

100

VDD=5V,RL=8Ω

VDD=3V,RL=8Ω

300

600

900

1200

1500

1800

100

200

300

400

500

600

Output Power(mW)

Figure 8

Figure 9

PSRR vs Frequency

-10

-20

-30

-40

-50

-60

-70

-80

VDD=5V, 8Ω Load, input grounded

100

1000

10000

100000

Frequency(Hz)

Figure 10

HM4990

APPLICATION INFORMATION

BRIDGE CONFIGURATION EXPLANATION

As shown in Figure 1, the HM4990 has two internal operational amplifiers. The first amplifier’s gain is externally

configurable, while the second amplifier is internally fixed in a unity-gain, inverting configuration. The

closed-loop gain of the first amplifier is set by selecting the ratio of R_Fto R_Iwhile the second amplifier’s gain is

fixed by the two internal 20kΩ resistors. Figure 1 shows that the output of amplifier 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

A_VD= 2*(R_F/R_I)

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

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

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 conditions. 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 excessive clipping, please refer to the Audio Power Amplifier

Design section.

A bridge configuration, such as the one used in HM4990, also creates a second advantage over single-ended

amplifiers. 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 configuration. 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.

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 HM4990 has two operational 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 Equation 1.

P_DMAX= 4*(V_DD)²/(2π²R_L)

(1)

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 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 HM4990. It is especially effective when connected to V_DD, GND, and the output pins. Refer

to the application information on the HM4990 reference design board for an example of good heat sinking. If T_JMAX

still exceeds 150°C, then additional changes must be made. These changes can include reduced supply

voltage, higher load impedance, or reduced ambient temperature. Internal power dissipation is a function of

output power.

HM4990

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 both the bypass and power supply pins 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 HM4990. The selection of a bypass capacitor, especially C_B, is dependent upon various design

considerations such as PSRR requirements, pop and click performance, system cost, and size constraints.

SHUTDOWN FUNCTION

In order to reduce power consumption while not in use, the HM4990 contains shutdown circuitry. This shutdown

turns the amplifier off when logic low is placed on the SD pin. By asserting the shutdown pin to GND, the HM4990

supply current draw will be minimized in idle mode.

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

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

conjunction with an external pull-down resistor. This scheme guarantees that the shutdown pin will not float,

thus preventing unwanted state changes.

PROPER SELECTION OF EXTERNAL COMPONENTS

Proper selection of external components in applications using integrated power amplifiers is critical to optimize

device and system performance. While the HM4990 is tolerant of external component combinations, consideration

to component values must be used to maximize overall system quality.

The HM4990 is unity-gain stable which gives the designer maximum system flexibility. The HM4990 should be used in

low gain configurations to minimize THD+N values, and maximize the signal to noise ratio. Low gain

configurations require large input signals to obtain a given output power. Input signals equal to or greater than

1Vrms are available from sources such as audio codec. Besides gain, one of the major considerations is the

closed loop bandwidth of the amplifier. To a large extent, the bandwidth is dictated by the choice of external

components shown in Figure 1. The input coupling capacitor, C_I, forms a first order high pass filter which limits

low frequency response. This value should be chosen based on needed frequency response for a few distinct

reasons.

SELECTION OF INPUT CAPACITOR SIZE

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 attenuation. 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 performance.

In addition to system cost and size, pop and click performance is also affected by the size of the input coupling

capacitor, 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.

Besides minimizing the input capacitor size, careful consideration should be paid to the bypass capacitor value.

Bypass capacitor, C_B, is the most critical component to minimize turn-on pops since it determines how fast the

HM4990 turns on. The slower the HM4990’s outputs ramp to their quiescent DC voltage (nominally 1/2 V_DD), the

HM4990

smaller the turn-on pops. Choosing C_Bequal to 1.0μF along with a small value of C_I(in the range of 0.1μF to

0.39μF), should produce a virtually click-less and pop-less shutdown function. While the device will function

properly with C_Bequal to 0.1μF, the device will be much more susceptible to turn-on pops and clicks. Thus, a

value of C_Bequal to 1.0μF is recommended in all but the most cost sensitive designs.

AUDIO POWER AMPLIFIER DESIGN EXAMPLE

A 1W/8Ω Audio Amplifier

Given that

Power Output:

Load Impedance:

Input Level:

1Wrms

8Ω

1Vrms

Input Impedance:

Bandwidth:

20kΩ

100Hz – 20kHz ± 0.25dB

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 Performance Characteristics section, the

supply rail can be easily found.

5V is a standard voltage in most applications, it is chosen for the supply rail. Extra supply voltage creates

headroom that allows the HM4990 to reproduce peaks in excess of 1W without producing 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.

Once the power dissipation equations have been addressed, the required differential gain can be determined

from Equation 2.

A_VD (P R_L)/(V_IN) V_ORMS/V_IRMS

(2)

R_F/R_I= A_VD/2

From Equation 2, the minimum A_VDis 2.83; use A_VD= 3. Since the desired input impedance was 20kΩ, and

with a A_VDimpedance of 2, a ratio of 1.5:1 of R_Fto R_Iresults in an allocation of R_I= 20kΩ and R_F= 30kΩ. The

final design step is to address the bandwidth requirements 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.

f_L= 100Hz/5 = 20Hz

f_H= 20kHz * 5 = 100kHz

R_Iin conjunction with C_Icreating a high-pass filter

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

The high frequency pole is determined by the product of the desired frequency pole, f_H, and the differential gain,

A_VD. With a A_VD= 3 and f_H= 100kHz, the resulting GBWP = 300kHz which is much smaller than the HM4990

GBWP of 2.5MHz. This figure displays that if a designer has a need to design an amplifier with a higher

differential gain, the HM4990 can still be used without running into bandwidth limitations.

The HM4990 is unity-gain stable and requires no external components besides gain-setting resistors, an input

HM4990

coupling capacitor, and proper supply bypassing in the typical application. However, if a closed-loop differential

gain of greater than 10 is required, a feedback capacitor (C₄) may be needed as shown in Figure 11 to

bandwidth limit the amplifier. This feedback capacitor creates a low pass filter that eliminates possible high

frequency oscillations. Care should be taken when calculating the -3dB frequ6ency in that an incorrect

combination of R₃and C₄will cause a roll-off lower than 20kHz. A typical combination of feedback resistor and

capacitor that will not produce audio band high frequency roll off is R₃= 20kΩ and C₄= 25pf. These

components result in a -3dB point of approximately 320kHz.

Figure 11: High Gain Audio Amplifier

Differential Input Application

The schematic in Figure 12 shows how to design the HM4990 to work in a differential input mode.

The gain of the amplifier is:

A_VD= 2 *(R₃/R₂), Given that R2=R5、R3=R6

In order to reach the optimal performance of the differential function, R2 and R5, or R3 and R6 should be

matched at 1% max.

Figure 12: Differential Amplifier Configuration For HM4990

HM4990

PHYSICAL DIMENSIONS

HM4990A --COL1.5X1.5-9L (P0.50T0.50/0.60) PACKAGE OUTLINE DIMENSIONS

Top View

Bottom View

Side View

Unit: millimeters.

HM4990

HM4990M MSOP8 Package

REF

MIN

TYP

1.10

0.10

0.86

3.0

MAX

0.05

0.78

2.90

4.75

0.4

0.15

0.94

3.1

5.05

0.7

3.0

4.9

0.55

0.95

0.30

0.15

0.65

0.22

0.08

0.38

0.23

Unit: millimeters.

HM4990A [HMSEMI]

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