MAX9757_技术文档

19-3782; Rev 1; 1/06

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

General Description

Features

♦ Automatic Level Control—Protects Speakers

The MAX9756/MAX9757/MAX9758 combine dual, 2.3W,

bridge tied load (BTL) stereo audio power amplifiers and

a DirectDrive^TMheadphone amplifier in a single device.

These devices feature single-supply voltage operation,

shutdown mode, logic-selectable gain, a headphone

sense input, a 31-step analog volume control, and indus-

try-leading click-and-pop suppression. The headphone

amplifier uses Maxim’s DirectDrive architecture that pro-

duces a ground-referenced output from a single supply,

eliminating the need for large DC-blocking capacitors.

♦ Analog Volume Control

♦ 120mW DirectDrive Headphone Amplifiers (16Ω)

♦ 150mA Adjustable LDO

♦ Class AB, 2.3W, Stereo BTL Speaker Amplifiers

(3Ω)

♦ High 95dB PSRR

♦ Low-Power Shutdown Mode

♦ Industry-Leading Click-and-Pop Suppression

♦ Short-Circuit and Thermal Protection

♦ Beep Input

The MAX9756/MAX9757 feature automatic level control

(ALC) that automatically limits output power to the speak-

er in the event of an overpowered output.

The MAX9756/MAX9758s’ 150mA internal linear regula-

tor provides a complete solution for DAC- or CODEC-

based designs.

The MAX9756/MAX9757/MAX9758 are offered in space-

saving, thermally efficient 32-pin (5mm x 5mm x 0.8mm)

and 36-pin thin QFN (6mm x 6mm x 0.8mm) packages.

All devices are specified over the extended -40°C to

+85°C temperature range.

Ordering Information

PART

ALC

√

LDO

√

PIN-PACKAGE

36 Thin QFN-EP*

32 Thin QFN-EP*

MAX9756ETX+

MAX9757ETJ+

MAX9758ETJ+

√

—

√

—

Applications

Note: All devices specified for -40°C to +85°C operating

Notebook PCs

Tablet PCs

Flat-Panel TVs

PC Displays

temperature range.

+Denotes lead-free package.

*EP = Exposed paddle.

Portable DVD

Players

LCD Projectors

Portable Audio

Simplified Block Diagrams

SINGLE SUPPLY 4.5V TO 5.5V

ALC

SINGLE SUPPLY 4.5V TO 5.5V

ALC

VOL

BEEP

HPS

VOL

BEEP

HPS

VOL

BEEP

HPS

1.2V TO 5V

LDO

1.2V TO 5V

LDO

MAX9757

MAX9756

MAX9758

________________________________________________________________ Maxim Integrated Products

1

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

ABSOLUTE MAXIMUM RATINGS

Supply Voltage (V , PV , HPV , CPV , IN to GND) ....+6V

Continuous Input Current (all other pins) ......................... 20mA

DD

PGND, CPGND to GND...................................................... 0.3V

CPV , C1N, V to GND......................................-6.0V to +0.3V

Continuous Power Dissipation (T = +70°C, single-layer board)

A

32-Pin Thin QFN (derate 18.6mW/°C above +70°C).....1490mW

36-Pin Thin QFN (derate 20.4mW/°C above +70°C).....1633mW

Continuous Power Dissipation (T =+70°C, multilayer board)

A

32-Pin Thin QFN (derate 24.9mW/°C above +70°C).....1990mW

36-Pin Thin QFN (derate 27.7mW/°C above +70°C).....2180mW

Junction Temperature .....................................................+150°C

Operating Temperature Range ...........................-40°C to +85°C

Storage Temperature Range.............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

SS

HP_ to GND ........................................................................... 3V

Any Other Pin .............................................-0.3V to (V + 0.3V)

DD

Duration of OUT_ Short Circuit to GND or PV ........Continuous

DD

Duration of OUT_+ Short Circuit to OUT_-.................Continuous

Duration of HP_ Short Circuit to GND,

V , or HPV .........................................................Continuous

SS DD

Duration of OUT Short Circuit to GND........................Continuous

Continuous Current (PV , OUT_, PGND) ...........................1.7A

DD

Continuous Current (CPV , C1N, CPGND, C1P, CPV

,

SS

DD

V

SS

, HPV , HP_, IN, OUT).............................................0.85A

DD

Stresses beyond those listed under “Absolute Maximum 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 in the operational sections of the specifications is not implied. Exposure to

absolute maximum rating conditions for extended periods may affect device reliability.

ELECTRICAL CHARACTERISTICS

(V = PV

= HPV

= CPV = IN = +5.0V, GND = PGND = CPGND = 0, SHDN = V , REGEN = V , DR = SET = GND, C

DD

DD DD DD DD BIAS

= 1µF, C

= 1µF, C1 = C2 = 1µF, PREF = unconnected, speaker loads terminated between OUT_+ and OUT_-, headphone load

PVSS

terminated between HP_ and GND, GAIN1 = GAIN2 = GAIN3 = VOL = 0 (A

= 15dB, A

= 0dB), T = -40°C to +85°C, unless

V(HP) A

V(SP)

otherwise noted. Typical values are at T = +25°C.) (Note 1)

A

PARAMETER

GENERAL

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Supply Voltage Range

V

, PV

Inferred from PSRR test

4.5

3.0

5.5

V

DD

Headphone Supply Voltage

HPV

Inferred from PSRR test

DD

HPS = GND, speaker

14

7

29

13

mode, R = ∞

I

= I

HPVDD

+

L

DD

VDD

+ I

Quiescent Supply Current

I

mA

DD

HPS = 5V, headphone

CPVDD

mode, R = ∞

L

Shutdown Supply Current

Bias Voltage

I

SHDN = REGEN = GND

0.2

2.43

10

5

µA

V

SHDN

V

2.2

10

2.65

BIAS

Switching Time

t

Gain or input switching

INL and INR

µs

kΩ

ms

SW

Input Resistance

Turn-On Time

R

20

30

15

IN

t

25

SON

SPEAKER AMPLIFIERS (HPS = GND)

Measured between OUT_+ and OUT_-,

Output Offset Voltage

V

0.4

mV

dB

OS

T

A

= +25°C

PV

= 4.5V to 5.5V, T = +25°C

75

95

83

DD

A

Power-Supply Rejection Ratio

(Note 2)

PSRR

f = 1kHz, V

= 200mV

RIPPLE

P-P

f = 10kHz, V

= 200mV

68

RIPPLE

P-P

R = 8Ω

0.9

1.3

L

THD+N = 1%, f = 1kHz

(T = +25°C)

R = 4Ω

L

2.0

Output Power (Note 3)

P

W

OUT

A

R = 3Ω

L

2.3

R = 8Ω, BTL P

= 1W, f = 1kHz

0.009

0.015

L

OUT

Total Harmonic Distortion Plus

Noise

THD+N

SNR

%

R = 4Ω, BTL P

L

= 1W, f = 1kHz

R = 8Ω, BTL P

= 1W, BW = 22Hz to

L

92

95

22kHz, unweighted

Signal-to-Noise Ratio

dB

R = 8Ω, BTL P

L

= 1W, A weighted

OUT

2

_______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

ELECTRICAL CHARACTERISTICS (continued)

(V = PV

= HPV

= CPV = IN = +5.0V, GND = PGND = CPGND = 0, SHDN = V , REGEN = V , DR = SET = GND, C

DD

DD DD DD DD BIAS

= 1µF, C

= 1µF, C1 = C2 = 1µF, PREF = unconnected, speaker loads terminated between OUT_+ and OUT_-, headphone load

PVSS

terminated between HP_ and GND, GAIN1 = GAIN2 = GAIN3 = VOL = 0 (A

= 15dB, A

= 0dB), T = -40°C to +85°C, unless

V(HP) A

V(SP)

otherwise noted. Typical values are at T = +25°C.) (Note 1)

A

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

µV

BW = 22Hz to 22kHz, unweighted,

measured at output, input at AC GND

Noise

V

71

n

RMS

Capacitive-Load Drive

Crosstalk

C

No sustained oscillations

200

80

pF

dB

L

L to R, R to L, f = 10kHz

Slew Rate

SR

Measured between OUT_+ and OUT_-

1.3

V/µs

GAIN3 = 0

GAIN3 = 1

GAIN2 = 0

GAIN2 = 1

GAIN2 = 0

GAIN2 = 1

GAIN1 = 0

GAIN1 = 1

GAIN1 = 0

GAIN1 = 1

GAIN1 = 0

GAIN1 = 1

GAIN1 = 0

GAIN1 = 1

15

16.5

18

19.5

21

Gain (Maximum Volume Settings)

(Note 4)

A

VMAX

(SPKR)

dB

22.5

24.0

25.5

Into

shutdown

Out of

shutdown

65

Peak voltage, 32

samples/second,

A weighted (Note 5)

Click-and-Pop Level

K

dBV

CP

38.5

HEADPHONE AMPLIFIERS (HPS = V

)

DD

Output Offset Voltage

V

T

= +25°C

2

90

7

mV

dB

OS(HP)

A

HPV

= 3V to 5.5V, T = +25°C

70

40

DD

A

Power-Supply Rejection Ratio

(Note 2)

PSRR

f = 1kHz, V

= 200mV

72

RIPPLE

P-P

f = 10kHz, V

= 200mV

70

RIPPLE

P-P

R = 32Ω

L

68

THD+N = 1%, f = 1kHz

(T = +25°C)

Output Power (Note 3)

P

mW

%

OUT

A

R = 16Ω

L

130

0.02

0.04

R = 32Ω, V

= 1V

, f = 1kHz

L

OUT

RMS

Total Harmonic Distortion Plus

Noise

THD+N

SNR

R = 16Ω, V

L

OUT

RMS

R = 32Ω, BTL P

BW = 22Hz to 22kHz, unweighted

= 65mW,

L

OUT

97

Signal-to-Noise Ratio

dB

R = 32Ω, BTL P = 65W,

BW = 22Hz to 22kHz, A weighted

L

OUT

100

Noise

V

BW = 22Hz to 22kHz

20.4

200

60

µV

RMS

n

Capacitive-Load Drive

Crosstalk

C

No sustained oscillations

L to R, R to L, f = 10kHz

pF

dB

L

Slew Rate

SR

1.4

0

V/µs

GAIN2 = 0, HPS = 1

GAIN2 = 1, HPS = 1

Gain (Maximum Volume Settings)

(Note 6)

A

dB

VMAX(HP)

3.0

Peak voltage, 32

samples/second,

A weighted (Note 4)

Into shutdown

Out of shutdown

62

50

Click-and-Pop Level

K

dBV

CP

_______________________________________________________________________________________

3

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

ELECTRICAL CHARACTERISTICS (continued)

(V = PV

= HPV

= CPV = IN = +5.0V, GND = PGND = CPGND = 0, SHDN = V , REGEN = V , DR = SET = GND, C

DD

DD DD DD DD BIAS

= 1µF, C

= 1µF, C1 = C2 = 1µF, PREF = unconnected, speaker loads terminated between OUT_+ and OUT_-, headphone load

PVSS

terminated between HP_ and GND, GAIN1 = GAIN2 = GAIN3 = VOL = 0 (A

= 15dB, A

= 0dB), T = -40°C to +85°C, unless

V(HP) A

V(SP)

otherwise noted. Typical values are at T = +25°C.) (Note 1)

A

PARAMETER

CHARGE PUMP

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Charge-Pump Frequency

VOLUME CONTROL

VOL Input Impedance

VOL Input Hysteresis

f

500

550

600

kHz

OSC

R

100

10

MΩ

VOL

mV

0.858 x

Full Mute Voltage

(Note 7)

= 1kHz

V

HPV

DD

Full Mute Attenuation

Input Impedance

f

-85

dB

IN

R

VOL_

Any gain setting

100

0.2

0.3

1.0

MΩ

A

V

A

V

A

V

= +15dB to 0dB

= -2dB to -20dB

= -22dB to -56dB

Channel Matching

dB

BEEP INPUT

T

= +25°C, R = 47kΩ (see BEEP Input

B

A

Beep Signal Amplitude Threshold

0.3

V

section)

Beep Signal Frequency

Threshold

T

A

= +25°C

300

Hz

AUTOMATIC LEVEL CONTROL SPEAKER AMPLIFIER (MAX9756/MAX9757)

PREF Threshold Accuracy

Maximum Gain Compression

Attack Time

R

= 180kΩ

5

8.1

%

PREF

6.0

6.3

15

50

30

9.5

3

dB

ms

C = 1µF (Note 8)

T

Hold Time

Time between attack and release phases

0V < V < (0.3V x V

)

DR

DD

C = 1µF,

T

release from

6dB

Release Time (Note 9)

0.4V < V < (0.6V x V

)

s

DR

DD

0.8V < V < V

DR

DD

DR INPUT (TRI-STATE INPUT)

0.8 x

DR Input Voltage High

V

DRH

DD

V

DD

0.4 x

0.6 x

V

DD

DR Input Voltage Middle

V

DRM

V

DD

0.3 x

DR Input Voltage Low

Input Leakage Current

V

0

V

DRL

V

DD

0V ≤ V ≤ V

1

µA

DR

DD

LOGIC INPUTS (GAIN_, SHDN, REGEN)

Input High Voltage

Input Low Voltage

Input Leakage Current

V

2

V

IH

V

0.8

1

IL

I

µA

IN

4

_______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

ELECTRICAL CHARACTERISTICS (continued)

(V = PV

= HPV

= CPV = IN = +5.0V, GND = PGND = CPGND = 0, SHDN = V , REGEN = V , DR = SET = GND, C

DD

DD DD DD DD BIAS

= 1µF, C

= 1µF, C1 = C2 = 1µF, PREF = unconnected, speaker loads terminated between OUT_+ and OUT_-, headphone load

PVSS

terminated between HP_ and GND, GAIN1 = GAIN2 = GAIN3 = VOL = 0 (A

= 15dB, A

= 0dB), T = -40°C to +85°C, unless

V(HP) A

V(SP)

otherwise noted. Typical values are at T = +25°C.) (Note 1)

A

PARAMETER

LOGIC INPUT HEADPHONE (HPS)

Input High Voltage

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

V

2

V

IH

Input Low Voltage

V

0.8

IL

HPS Pullup Current

35

µA

LOW-DROPOUT LINEAR REGULATOR

Input Voltage Range

V

Inferred from line regulation

3.5

5.5

V

IN

I

= 0mA, SHDN = GND

100

350

0.1

160

OUT

Supply (Ground) Current

I

µA

Q

= 150mA

Shutdown Current

Output Current

I

REGEN = 0V

3

µA

SHDN

I

150

mA

OUT

Fixed Output Voltage Accuracy

Adjustable Output Voltage Range

SET Reference Voltage

I

= 1mA

1.5

4.85

1.23

%

V

OUT

V

SET

V

1.19

1.21

200

20

V

SET

SET Dual-Mode Threshold

SET Input Leakage Current

mV

nA

I

500

50

SET

I

= 50mA

25

OUT

V

= 4.65V (fixed

OUT

Dropout Voltage (Note 10)

∆V

mV

OD

output operation)

= 150mA

100

300

20

150

OUT

Output Current Limit

Startup Time

I

mA

µs

LIM

V

= 3.5V to 5.5V, V

= 1mA

= 2.5V,

IN

OUT

Line Regulation

Load Regulation

Ripple Rejection

-0.1

+0.01

+0.1

%/V

%

I

OUT

V

= 4.65V, 1mA < I

< 150mA

0.5

60

50

OUT

f = 1kHz

f = 10kHz

= 200mV

dB

RIPPLE

P-P

20Hz to 22kHz, C

= 2 x 1µF,

= 4.65V

OUT

Output Voltage Noise

100

µV

RMS

I

= 150mA, V

OUT

Note 1: All devices are 100% production tested at room temperature. All temperature limits are guaranteed by design.

Note 2: PSRR is specified with the amplifier input connected to GND through R and C

.

IN

Note 3: Output power levels are measured with the TQFN’s exposed paddle soldered to the ground plane.

Note 4: Speaker path gain is defined as: A = (V - V )/V ).

VSPKR

OUT+

OUT- IN__

Note 5: Speaker mode testing performed with 8Ω resistive load connected across BTL output. Headphone mode testing per-

formed with 32Ω resistive load connected between HP_ and GND. Mode transitions are controlled by SHDN.

Note 6: Headphone path gain is defined as: A

= V

/V

.

VHP

HP_ IN__

Note 7: See Table 3 for detains on the mute levels.

Note 8: Attack envelope is exponential. Attack time is defined as the 15 x 10³x C .

T

Note 9: Time for the gain to return to within 10% of nominal gain setting after the input signal has fallen below the PREF threshold.

Release is linear in dB. Release time is proportional to magnitude of gain compression.

Note 10: Dropout voltage is defined as (V - V

) when V

is 2% below the value of V

for V = V

+ 1V.

OUT(NOM)

IN

OUT

IN

_______________________________________________________________________________________

5

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Typical Operating Characteristics

(V

= PV

= HPV

= CPV

= IN = +5.0V, GND = PGND = CPGND = 0V, SHDN = V , REGEN = DR = SET = GND, C

=

DD

BIAS

1µF, C

= 1µF, C1 = C2 = 1µF, PREF = unconnected, GAIN1 = 1, GAIN2 = GAIN3 = VOL = 0V, measurement BW = 22Hz to

PVSS

22kHz, T = +25°C, unless otherwise noted.)

A

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY (HEADPHONE MODE)

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY (HEADPHONE MODE)

10

V

= 5V

V

= 5V

V

= 5V

DD

R = 3Ω

L

R = 4Ω

L

R = 8Ω

L

1

0.1

1

0.1

OUTPUT POWER = 500mW

0.01

0.001

0.01

0.001

0.01

0.001

OUTPUT POWER = 1.8W

OUTPUT POWER = 1.5W

OUTPUT POWER = 1W

10

100

1k

10k

100k

10

100

1k

10k

100k

10

100

1k

10k

100k

FREQUENCY (Hz)

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER (SPEAKER MODE)

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER (SPEAKER MODE)

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER (SPEAKER MODE)

100

V

= 5V

V

= 5V

DD

V

= 5V

DD

R = 3Ω

L

R = 8Ω

L

R = 4Ω

L

10

1

f

= 10kHz

f

= 10kHz

IN

f

= 10kHz

IN

0.1

0.01

0.001

0.01

0.001

0.01

0.001

f

= 100Hz

IN

f

= 1kHz

f

= 1kHz

IN

f = 100Hz

IN

f

= 1kHz

0.5

f

= 100Hz

1.5

IN

0

0.5 1.0 1.5 2.0 2.5 3.0 3.5

OUTPUT POWER (W)

0

0.5 1.0 1.5 2.0 2.5 3.0 3.5

OUTPUT POWER (W)

0

1.0

2.0

OUTPUT POWER (W)

POWER DISSIPATION vs. OUTPUT POWER

(SPEAKER MODE)

OUTPUT POWER

vs. LOAD RESISTANCE (SPEAKER MODE)

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY (SPEAKER MODE)

3.0

2.5

2.0

1.5

1.0

0.5

0

3.0

2.5

2.0

1.5

1.0

0.5

0

-10

R = 4Ω

L

V

= 200mV

RIPPLE P-P

V

= 5V

DD

R = 8Ω

L

f = 1kHz

-20

-30

-40

THD+N = 10%

-50

R = 8Ω

L

-60

-70

-80

THD+N = 1%

-90

-100

-110

-120

f = 1kHz

P

= P

+ P

OUTL OUTR

OUT

1

10

LOAD RESISTANCE (Ω)

100

0

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

OUTPUT POWER (W)

10

100

1k

FREQUENCY (Hz)

10k

100k

6

_______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Typical Operating Characteristics (continued)

(V

= PV

= HPV

= CPV

= IN = +5.0V, GND = PGND = CPGND = 0V, SHDN = V , REGEN = DR = SET = GND, C

=

DD

BIAS

1µF, C

= 1µF, C1 = C2 = 1µF, PREF = unconnected, GAIN1 = 1, GAIN2 = GAIN3 = VOL = 0V, measurement BW = 22Hz to

PVSS

22kHz, T = +25°C, unless otherwise noted.)

A

CROSSTALK vs. FREQUENCY

TURN-ON RESPONSE (SPEAKER MODE)

(SPEAKER MODE)

TURN-OFF RESPONSE (SPEAKER MODE)

MAX9756 toc11

MAX9756 toc12

0

V

= 200mV

P-P

-10

-20

-30

-40

-50

-60

-70

-80

-90

-100

-110

IN

SHDN

5V/div

SHDN

5V/div

OUT_+

2V/div

RIGHT TO LEFT

OUT_+

2V/div

OUT_-

2V/div

LEFT TO RIGHT

OUT_-

2V/div

OUT_+ - OUT_-

50mV/div

OUT_+ - OUT_-

50mV/div

10

100

1k

FREQUENCY (Hz)

10k

100k

10ms/div

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY (HEADPHONE MODE)

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY (HEADPHONE MODE)

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY (HEADPHONE MODE)

10

V

= 5V

V

= 3.3V

DD

V

= 5V

DD

R = 32Ω

L

R = 16Ω

L

R = 16Ω

L

1

OUTPUT POWER = 100mW

OUTPUT POWER = 80mW

OUTPUT POWER = 20mW

0.1

0.01

0.001

0.01

0.001

0.01

0.001

OUTPUT POWER = 40mW

OUTPUT POWER = 20mW

OUTPUT POWER = 60mW

10

100

1k

10k

100k

10

100

1k

10k

100k

10

100

1k

10k

100k

FREQUENCY (Hz)

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER (HEADPHONE MODE)

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER (HEADPHONE MODE)

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY (HEADPHONE MODE)

10

100

HPV = 5V

DD

R = 16Ω

L

HPV = 5V

DD

R = 32Ω

L

V

= 3.3V

DD

R = 32Ω

L

10

1

10

1

f

= 10kHz

IN

f

= 1kHz

IN

f

= 1kHz

f

= 100Hz

IN

0.1

OUTPUT POWER = 50mW

0.1

0.01

0.001

0.01

0.001

0.01

0.001

OUTPUT POWER = 20mW

f

= 10kHz

f

= 100Hz

IN

0

20 40 60 80 100 120 140 160 180 200

OUTPUT POWER (mW)

0

10 20 30 40 50 60 70 80 90 100

OUTPUT POWER (mW)

10

100

1k

10k

100k

FREQUENCY (Hz)

_______________________________________________________________________________________

7

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Typical Operating Characteristics (continued)

(V

= PV

= HPV

= CPV

= IN = +5.0V, GND = PGND = CPGND = 0V, SHDN = V , REGEN = DR = SET = GND, C

=

DD

BIAS

1µF, C

= 1µF, C1 = C2 = 1µF, PREF = unconnected, GAIN1 = 1, GAIN2 = GAIN3 = VOL = 0V, measurement BW = 22Hz to

PVSS

22kHz, T = +25°C, unless otherwise noted.)

A

OUTPUT POWER vs. LOAD RESISTANCE

(HEADPHONE MODE)

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER (HEADPHONE MODE)

100

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT POWER (HEADPHONE MODE)

140

120

100

80

100

HPV = 3.3V

DD

HPV = 3.3V

DD

f = 1kHz

R = 16Ω

R = 32Ω

L

10

1

10

1

THD+N = 10%

f

= 1kHz

IN

f

= 1kHz

IN

f = 100Hz

IN

f

= 100Hz

IN

THD+N = 1%

60

0.1

40

f

= 10kHz

100

0.01

0.001

IN

0.01

0.001

20

f

= 10kHz

IN

0

10

100

LOAD RESISTANCE (Ω)

1000

20 30

0

20

40

60

80

120

0

10

40 50 60 70 80 90 100

OUTPUT POWER (mW)

POWER DISSIPATION vs. OUTPUT POWER

(HEADPHONE MODE)

OUTPUT POWER vs. SUPPLY VOLTAGE

(HEADPHONE MODE)

OUTPUT POWER vs. LOAD RESISTANCE

(HEADPHONE MODE)

0.8

0.6

0.4

0.2

0

200

180

160

140

120

100

80

140

130

120

110

100

90

80

70

60

50

HPV = 5V

DD

f = 1kHz

THD+N = 1%

f = 1kHz

P

= P + P

HL HR

OUT

R = 16Ω

L

R = 16Ω

L

THD+N = 10%

THD+N = 1%

R = 32Ω

L

60

40

30

20

10

R = 32Ω

L

40

20

0

25 50 75 100 125 150 175 200 225 250

OUTPUT POWER (mW)

10

100

1000

3.0

3.5

4.0

4.5

5.0

5.5

LOAD RESISTANCE (Ω)

SUPPLY VOLTAGE (V)

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY (HEADPHONE MODE)

OUTPUT POWER vs. CHARGE-PUMP

CAPACITANCE (HEADPHONE MODE)

CROSSTALK vs. FREQUENCY

(HEADPHONE MODE)

150

140

0

-10

-20

-30

-40

-50

-60

-70

-80

-90

-100

0

-10

-20

-30

-40

-50

-60

-70

-80

-90

-100

-110

f = 1kHz

THD+N = 1%

V

= 100mV

P-P

RIPPLE

R = 32Ω

f = 1kHz

L

INPUTS AC-GROUNDED

130

120

110

V

= 200mV

C1 = C2 = 1µF

IN

P-P

100

90

HPV = 3.3V

DD

RIGHT TO LEFT

80

70

C1 = C2 = 2.2µF

60

50

LEFT TO RIGHT

40

30

20

HPV = 5V

DD

20

35 40

25 30

LOAD (Ω)

10 15

45 50

10

100

1k

10k

100k

0.01

0.1

1

10

100

FREQUENCY (Hz)

8

_______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Typical Operating Characteristics (continued)

(V

= PV

= HPV

= CPV

= IN = +5.0V, GND = PGND = CPGND = 0V, SHDN = V , REGEN = DR = SET = GND, C

=

DD

BIAS

1µF, C

= 1µF, C1 = C2 = 1µF, PREF = unconnected, GAIN1 = 1, GAIN2 = GAIN3 = VOL = 0V, measurement BW = 22Hz to

PVSS

22kHz, T = +25°C, unless otherwise noted.)

A

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

TURN-OFF RESPONSE (HEADPHONE MODE)

TURN-ON RESPONSE (HEADPHONE MODE)

MAX9756 toc29

MAX9756 toc28

20

17

14

11

8

SHDN

5V/div

SHDN

5V/div

HPS = GND

HPR

10mV/div

HPR

10mV/div

HPS = V

DD

HPL

10mV/div

HPL

10mV/div

5

4.5

4.7

4.9

5.1

5.3

5.5

10ms/div

SUPPLY VOLTAGE (V)

SHUTDOWN CURRENT

vs. SUPPLY VOLTAGE

POWER LIMITING OF SINE BURST

(FAST ATTACK AND SLOW RELEASE)

(FAST ATTACK AND FAST RELEASE)

MAX9756 toc32

MAX9756 toc33

600

500

400

300

200

100

0

OUTPUT

2V/div

OUTPUT

2V/div

CT

1V/div

CT

1V/div

4.5

4.7

4.9

5.1

5.3

5.5

10ms/div

40ms/div

SUPPLY VOLTAGE (V)

LDO OUTPUT VOLTAGE ACCURACY

vs. LOAD CURRENT

POWER LIMITING OF SINE BURST

(SLOW ATTACK AND SLOW RELEASE)

MAX9756 toc33

2.0

1.5

1.0

0.5

0

OUTPUT

2V/div

-0.5

-1.0

-1.5

-2.0

CT

1V/div

0

25

50

75

100

125

150

2s/div

LOAD CURRENT (mA)

_______________________________________________________________________________________

9

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Typical Operating Characteristics (continued)

(V

= PV

= HPV

= CPV

= IN = +5.0V, GND = PGND = CPGND = 0V, SHDN = V , REGEN = DR = SET = GND, C

=

DD

BIAS

1µF, C

= 1µF, C1 = C2 = 1µF, PREF = unconnected, GAIN1 = 1, GAIN2 = GAIN3 = VOL = 0V, measurement BW = 22Hz to

PVSS

22kHz, T = +25°C, unless otherwise noted.)

A

CROSSTALK vs. FREQUENCY

LDO OUTPUT VOLTAGE ACCURACY

vs. TEMPERATURE

DROPOUT VOLTAGE

vs. LOAD CURRENT

(LDO)

5

4

0

300

200

100

0

R

P

= 4Ω

OUT(SPK)

L

-10

-20

-30

-40

-50

-60

-70

-80

-90

-100

-110

= 1W

3

2

1

0

-1

-2

-3

-4

-5

-100

-200

-300

I

= 90mA

OUT

I

= 50mA

OUT

I

= 10mA

OUT

0.1

-40

-15

10

35

60

85

0.01

1

10

100

0

25

50

75

100

125

150

TEMPERATURE (°C)

FREQUENCY (Hz)

LOAD CURRENT (mA)

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY (LDO)

LDO OUTPUT NOISE

MAX9756 toc40

0

-10

-20

-30

-40

-50

-60

-70

-80

-90

V

= 100mV

P-P

RIPPLE

LDO_OUT

1mV/div

-100

10

100

1k

FREQUENCY (Hz)

10k

100k

200µs/div

10 ______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Typical Operating Characteristics (continued)

(V

= PV

= HPV

= CPV

= IN = +5.0V, GND = PGND = CPGND = 0V, SHDN = V , REGEN = DR = SET = GND, C

=

DD

BIAS

1µF, C

= 1µF, C1 = C2 = 1µF, PREF = unconnected, GAIN1 = 1, GAIN2 = GAIN3 = VOL = 0V, measurement BW = 22Hz to

PVSS

22kHz, T = +25°C, unless otherwise noted.)

A

OUTPUT NOISE

vs. FREQUENCY (LDO)

110

LINE-TRANSIENT RESPONSE

MAX9756 toc42

C

= 2µF

OUT

100

90

80

70

60

50

40

30

20

10

5.5V

10Hz TO 100kHz

V

IN

500mV/div

4.5V

LDO_OUT

20mV/div

10

100

1k

FREQUENCY (Hz)

10k

100k

40µs/div

LOAD-TRANSIENT RESPONSE

LDO SHUTDOWN RESPONSE

MAX9756 toc43

MAX9756 toc44

50V

REGEN

5V/div

I

LOAD

25mV/div

0V

LDO_OUT = 4.65V

20mV/div

LDO_OUT

1V/div

20µs/div

100ms/div

Pin Description

NAME

FUNCTION

MAX9756 MAX9757 MAX9758

1

32

INL

Left-Channel Audio Input

2

3

1

2

1

GAIN1 Gain Control Input 1

GAIN2 Gain Control Input 2

GAIN3 Gain Control Input 3

BEEP Audible Alert Beep Input

PGND Power Ground

2

3

4

3

5

4

6, 22

7

5, 21

6

5, 21

6

OUTL+ Left-Channel Positive Speaker Output

OUTL- Left-Channel Negative Speaker Output

8

7

9,19

8,18

8, 18

PV

Speaker Amplifier Power Supply. Bypass with 1µF ceramic capacitor to PGND.

DD

______________________________________________________________________________________ 11

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Pin Description (continued)

NAME

CPV

FUNCTION

MAX9756 MAX9757 MAX9758

10

9

Charge-Pump Power Supply. Bypass with 1µF ceramic capacitor to CPGND.

DD

Charge-Pump Flying-Capacitor Positive Terminal. Connect a 1µF capacitor from C1P

to C1N.

11

10

C1P

12

13

14

11

12

13

11

12

13

CPGND Charge-Pump Ground

Charge-Pump Flying-Capacitor Negative Terminal. Connect a 1µF capacitor from

C1N

CPV

C1P to C1N.

Charge-Pump Negative Output. Connect to V

.

SS

Headphone Amplifier Negative Power Supply. Bypass with 1µF ceramic capacitor to

GND.

15

14

V

SS

16

17

15

16

15

16

HPR

HPL

Right Headphone Output

Left Headphone Output

18

17

HPV

Headphone Positive Power Supply. Bypass with 1µF ceramic capacitor to GND.

DD

20

21

19

20

19

20

OUTR- Right-Channel Negative Speaker Output

OUTR+ Right-Channel Positive Speaker Output

Headphone Sense Input. Leave HPS unconnected if automatic headphone sensing

is not used.

23

24

22

—

22

23

HPS

LDO Enable. Connect REGEN to V to enable the LDO. Connect to GND to

DD

disable LDO.

REGEN

Automatic Level Control Attack to Release Time Ratio Select. Hardwired to V

GND, or BIAS to set the attack to release ratio; see the ALC section.

,

DD

25

26

27

28

29

23

24

25

26

27

—

24

25

26

—

DR

BIAS

SHDN

VOL

Common-Mode Bias Voltage. Bypass with a 1.0µF capacitor to GND.

Shutdown Input. Drive SHDN low to disable the audio amplifiers. Connect SHDN to

for normal operation.

V

DD

Analog Volume Control Input

Power-Limiting Input. Connect a resistor from PREF to GND to set the speaker output

clamping level. Leave PREF unconnected to disable ALC; see the ALC section.

PREF

Regulator Feedback Input. Connect to GND for 4.65V fixed output. Connect to

resistor-divider for adjustable output; see the Low-Dropout Linear Regulator section.

30

—

27

SET

31

32

33

34

28

29

—

28

—

30

GND

Ground

V

Power Supply

DD

IN

LDO Input. Bypass with two 1µF ceramic capacitors to GND.

LDO Output. Bypass with two 1µF ceramic capacitors to GND.

OUT

Automatic Level Control Attack and Release Timing Capacitor. Connect CT to GND

to disable ALC; see the ALC section.

35

30

—

CT

36

—

31

—

31

29

INR

Right-Channel Audio Input

V

Power-Supply and LDO Input. Bypass with two 1µF ceramic capacitors to GND.

DD

Exposed Pad. The external pad lowers the package’s thermal impedance by

providing a direct-heat conduction path from the die to the PC board. Connect the

exposed thermal pad to GND.

EP

12 ______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

All devices feature a single-supply voltage, a shut-

Detailed Description

down mode, logic-selectable gain, and a headphone

The MAX9756/MAX9757/MAX9758 combine dual, 2W

sense input. Industry-leading click-and-pop suppres-

BTL stereo audio power amplifiers with a DirectDrive

sion eliminates audible transients during power and

headphone amplifier in a single device. The stereo

shutdown cycles.

power amplifiers deliver up to 2.3W per channel into a

Each signal path consists of an input amplifier that sets

the signal-path gain and feeds both the speaker and

headphone amplifiers (Figure 1). The speaker amplifier

uses a BTL architecture, doubling the voltage drive to

the speakers and eliminating the need for DC-blocking

capacitors. The output consists of two signals, identical

in magnitude, but 180° out of phase.

3Ω speaker from a 5V supply and the stereo head-

phone amplifiers deliver up to 130mW per channel into

a 16Ω headphone from a 5V supply.

The MAX9756/MAX9757 feature ALC that automatically

controls output power to the speaker, preventing loud-

speaker, overload and provides optimized dynamic

range.

The headphone amplifiers use Maxim’s DirectDrive

architecture that eliminates the bulky output DC-blocking

capacitors required by traditional headphone amplifiers.

The MAX9756/MAX9757/MAX9758 feature 31-step ana-

log volume control and a BEEP input. The amplifier

gain is pin programmable. These devices feature click-

and-pop suppression, eliminating the need for discrete

muting circuitry. Speaker and headphone outputs have

short-circuit and thermal protection.

A charge pump inverts the positive supply (CPV ), cre-

DD

ating a negative supply (CPV ). The headphone ampli-

SS

fiers operate from these bipolar supplies with their

outputs biased about GND (Figure 2).

The MAX9756/MAX9758s’ internal LDO features

Maxim’s Dual Mode™ feedback. The LDO output volt-

age is either fixed at 4.65V (SET = GND), or adjusted

between 1.23V and 5V using a resistive divider at SET.

The LDO delivers up to 150mA of continuous current,

and can be enabled independently from the audio

amplifiers. Short-circuit and thermal-overload protec-

tion are provided for the LDO.

The amplifiers have almost twice the supply range

compared to other single-supply amplifiers, nearly qua-

drupling the available output power. The benefit of the

GND bias is that the amplifier outputs do not have a DC

component (typically V /2). This eliminates the large

DD

DC-blocking capacitors required with conventional

headphone amplifiers, conserving board space and

system cost while improving frequency response.

IN_

V

DD

V

OUT

V

DD

/2

ALC

OUT_+

GND

BIAS

CONVENTIONAL DRIVER-BIASING SCHEME

+V

DD

VOLUME

VOL

OUT_-

HP_

CONTROL

BIAS

GND

-V

DD

DirectDrive BIASING SCHEME

Figure 1. MAX9756/MAX9757 Signal Path

Figure 2. Traditional Headphone Amplifier Output Waveform

vs. DirectDrive Headphone Amplifier Output Waveform

Dual Mode is a trademark of Maxim Integrated Products, Inc.

______________________________________________________________________________________ 13

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

The MAX9756/MAX9757/MAX9758 feature an under-

voltage lockout that prevents operation from an insuffi-

cient power supply and click-and-pop suppression that

eliminates audible transients on startup and shutdown.

The amplifiers include thermal-overload and short-cir-

cuit protection. An additional feature of the amplifiers is

that there is no phase inversion from input to output.

applied to the input, eliminating output clipping. Figure 3

shows a comparison of an overgained speaker input with

and without ALC.

The MAX9756/MAX9758 control the gain to the speakers

by first detecting that the output voltage to the speaker

has exceeded a preset limit. The speaker amplifier gain

is rapidly reduced to correct for the excessive output

power. This process is known as the attack time. When

the signal subsequently lowers in amplitude, the gain is

held at the reduced state for a short period before slowly

increasing to the normal value. This process is known as

the hold and release time. The speed at which the ampli-

fiers adjust to changing input signals is set by the exter-

Automatic Level Control (ALC)

Two-watt amplifiers are commonly used in notebook

PCs (almost always powered from a 5V supply). With

an 8Ω speaker driven from a BTL amplifier, the maxi-

m

u

m

theoretical continuous power available is:

nal timing capacitor C and the setting of logic input

CT

DR. The output power limit can be set by adjusting the

value of the external resistor connected to PREF. Gain

reduction is a function of input signal amplitude with a

maximum ALC attenuation of 6dB. Figure 4 shows the

effect of an input burst exceeding the preset limit, output

attack, hold and release times.

2

⎛

⎞

⎛

⎞

⎛

⎞

⎛

⎞

V

5

PEAK

⎜

⎝

⎟

⎠

⎜

⎝

⎟

⎠

⎜

⎟

⎜

⎟

⎝

R

⎠

⎝

⎠

2

8

P

=

= 1.56W

OUT

SPEAKER

This process (referred to as “limiting” in audio) limits the

amplifier output power so loudspeaker overload can be

prevented. If the attack and release times are configured

to respond too fast, audible artifacts often, described as

“pumping” or “breathing,” can occur as the gain is rapid-

ly adjusted to follow the dynamics of the signal. For best

results, adjust the time constant of the ALC to accommo-

date the source material. Notebook applications in which

music CDs and DVDs are the main audio source, a

495µs attack time with a 990ms release time is recom-

mended with a 1.2W output into an 8Ω load.

See Figure 5 for suggested ALC component values.

The ALC feature offers two benefits:

1) To limit amplifier power to protect a loudspeaker.

2) To make input signals with a wide dynamic range

more intelligible by boosting low-level signals with-

out distorting the high-level signals.

A device without ALC experiences clipping at the output

when too much gain is applied to the input. ALC pre-

vents clipping at the output when too much gain is

ALC ENABLE, NO CLIPPING AT THE OUTPUT

ALC DISABLE, CLIPPING AT THE OUTPUT

INPUT

SIGNAL

OUTPUT

SIGNAL

10ms/div

Figure 3. ALC Disabled vs. ALC Enabled

14 ______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

This allows the louder passages to be reduced in vol-

ume, thereby maximizing output dynamic range.

Having the attack time too long can possibly result in

some damage to the loudspeaker under harsh condi-

tions.

OUTPUT

2V/div

Hold Time

Hold time is the delay after the signal falls below the

threshold level before the release phase is initiated.

Hold time is internally set to 50ms and nonadjustable.

The hold time is cancelled by any signal exceeding the

set threshold level and attack is reinitiated.

CT

1V/div

Release Time

The release time is how long it takes for the gain to

return to its normal level after the input signal has fallen

10ms/div

below the threshold level and 50ms hold time has

expired. Release time is defined as release from a 6dB

gain compression to 10% of the nominal gain setting

after the input signal has fallen below PREF threshold

and the 50ms hold time has expired. Release time is

adjustable between 95ms and 10s. The release time is

Figure 4. Attack, Hold, and Release Time

Attack Time

The attack time is the time it takes to reduce the gain

after the input signal has exceeded the threshold level.

Suggested attack time range is from 150µs to 50ms.

The gain attenuation in attack is exponential and the

attack time is defined as one time constant. The time

set by picking an attack time using C and setting the

CT

attack to release time ratio by configuring DR as shown

in Table 2. Release time is linear in dB with time and is

inversely proportional to the magnitude of gain com-

pression:

constant of the attack is given by 15,000 x C

sec-

CT

• Use a small ratio to maximize the speed of the ALC.

onds (where C is the external timing capacitor).

CT

• Use a large ratio to maximize the sound quality and

prevent repeated excursions above the threshold

from being independently adjusted by the ALC.

• Use a short attack time for the ALC to react quickly

to transient signals, such as snare drum beats

(music) or gun shots (DVD). Fast attack times can

lead to gain “pumping” where rapid ALC action can

be heard reacting to dynamic material.

Release and attack times are set by selecting the

capacitance value between CT and GND, and by set-

ting the logic state of DR (Table 1). DR is a tristate logic

input that sets the attack-to-release time ratio. A fixed

hold time of 50ms is internally added to the release time.

• Use a longer attack time to allow the ALC to ignore

short-duration peaks and only reduce the gain when

a noticeable increase in loudness occurs. Short-dura-

tion peaks are not reduced, but louder passages are.

Table 1. Attack and Release Time

ATTACK TIME

DR = ‘X’

150µs

RELEASE TIME

TIMING CAPACITOR

(C

)

CT

DR = V

DR = GND

300ms

990ms

3s

DD

BIAS

10nF

33nF

100nF

330nF

1µF

30ms

99ms

300ms

990ms

3s

95ms

495µs

313ms

950ms

3.1s

9.5s

—

1.5ms

4.95ms

15ms

9.9s

—

2.2µF

3.3µF

33ms

6.6s

—

49.5ms

10s

—

______________________________________________________________________________________ 15

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

The release/attack time ratio that can be achieved by

programming DR is listed in Table 2.

OUTPUT POWER THRESHOLD

vs. R

PREF

3.0

2.5

2.0

1.5

1.0

0.5

0

Table 2. Release to Attack Ratio

DR

RELEASE/ATTACK RATIO

R = 4Ω

L

V

200

633

DD

V

BIAS

GND

2000

R = 8Ω

L

5V

V

DD

DR

CT

100 110 120 130 140 150 160 170 180 190 200

(kΩ)

R

PREF

MAX9756

MAX9757

33nF

Figure 6. Output Power Threshold vs. R

PREF

limit on an 8Ω load and a 200kΩ resistor results in a

1.5W clamp limit on an 8Ω load (Figure 6).

180kΩ

Use the following equation to choose the value for

R

for the desired maximum output power level

PREF

based on a sine wave input:

VALUES SHOWN FOR AN OUTPUT POWER THRESHOLD OF 1.2W WITH AN

R = 8Ω ATTACK TIME OF 495µs AND A RELEASE TIME OF 990ms

L

⎛

⎜

⎝

⎞

⎟

⎠

⎛

⎞

⎛

⎞

P

R

L

8

OUT

R

= 180kΩ

×

⎜

⎟

⎜

⎟

PREF

Figure 5. Recommended Output Power Threshold, Attack, and

Release Time Components

1.166

⎝

⎠

⎝

⎠

Output Power Threshold

To set the threshold at which speaker output is

clamped, an external resistor must be connected from

PREF to ground. The suggested external resistor range

is from 100kΩ to 200kΩ (for best results use a 1% resis-

tor). Leaving PREF unconnected disables the ALC

function. A constant current of 12µA is sourced at

PREF, so that a 180kΩ resistor results in 1.2W clamp

Gain Selection

The MAX9756/MAX9757/MAX9758 feature an internally

set, selectable gain. The GAIN1, GAIN2, and GAIN3

inputs set the maximum gain for the speaker and head-

phone amplifiers (Table 3). The gain of the device can

vary based upon the voltage at VOL but does not

exceed the maximum gain listed below (see the Analog

Volume (VOL) Control section).

Table 3. Maximum Gain Settings

GAIN3

GAIN2

GAIN1

SPEAKER MODE GAIN (dB)

HEADPHONE MODE GAIN (dB)

0

1

0

1

0

1

0

1

0

1

0

1

0

1

+15

+16.5

+18

0

+3

0

+19.5

+21

+22.5

+24

0

+3

+25.5

16 ______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Analog Volume Control (VOL)

The MAX9756/MAX9757/MAX9758 feature an analog

volume control that varies the gain of the device in 31

MAX9756

DD

HPV

VOL

discrete steps based upon the DC voltage applied to

VOL (see Table 4). The input range of VOL is from 0

V

REF

(full volume) to HPV

(full mute), with example step

DD

DAC

sizes shown in Table 3. Connect the reference of the

device driving VOL (Figure 7) to HPV . Connect VOL

DD

to GND (full volume) if volume control is not used.

Figure 7. Volume Control Circuit

Table 4. Volume Levels

V

(V) = MULTIPLIER x

SPEAKER MODE

GAIN (dB)

HEADPHONE MODE

GAIN (dB)

VOL

HPV

DD

GAIN3 = 0 GAIN3 = 0 GAIN3 = 0 GAIN3 = 0 GAIN3 = 1 GAIN3 = 1 GAIN3 = 1 GAIN3 = 1 GAIN3 = X GAIN3 = X

GAIN2 = 0 GAIN2 = 0 GAIN2 = 1 GAIN2 = 1 GAIN2 = 0 GAIN2 = 0 GAIN2 = 1 GAIN2 = 1 GAIN2 = 0 GAIN2 = 1

GAIN1 = 0 GAIN1 = 1 GAIN1 = 0 GAIN1 = 1 GAIN1 = 0 GAIN1 = 1 GAIN1 = 0 GAIN1 = 1 GAIN1 = X GAIN1 = X

V

VOL

MULTIPLIER

*

(MAX)

(MIN)

0.07

0.16

0.18

0.21

0.23

0.25

0.28

0.30

0.32

0.35

0.37

0.39

0.42

0.44

0.46

0.49

0.51

0.54

0.56

0.58

0.61

0.63

0.65

0.68

0.70

0.72

0.75

0.77

0.79

0.82

0.84

0.93

0.00

0.49

0.57

0.64

0.72

0.80

0.88

0.95

1.03

1.11

1.19

1.26

1.34

1.42

1.50

1.57

1.65

1.73

1.80

1.88

1.96

2.04

2.11

2.19

2.27

2.35

2.42

2.50

2.58

2.66

2.73

2.81

0.49

0.57

0.64

0.72

0.80

0.88

0.95

1.03

1.11

1.19

1.26

1.34

1.42

1.50

1.57

1.65

1.73

1.80

1.88

1.96

2.04

2.11

2.19

2.27

2.35

2.42

2.50

2.58

2.66

2.73

2.81

3.30

15

14

16.5

16

18

17.5

17

19.5

19

21

20

19

18

16

14

12

10

8

22.5

22

21

20

19

18

16

14

12

10

8

24

23.5

23

22.5

22

21

20

19

18

16

14

12

10

8

25.5

25

0

-1

3

2.5

2

13

15

18.5

18

24.5

24

-2

12

14

16.5

16

-3

1.5

1

10

13

17.5

17

23.5

23

-5

8

12

15

-7

0

6

10

14

16.5

16

22.5

22

-9

-1

4

8

13

-11

-13

-15

-17

-19

-21

-23

-25

-27

-29

-31

-33

-35

-37

-39

-41

-43

-47

-51

-55

-59

-63

-67

-71

MUTE

-2

2

6

12

15

21

-3

0

4

10

14

6

20

-5

-2

2

8

13

4

19

-7

-4

0

6

12

2

6

18

-9

-6

-2

4

10

0

4

16

-11

-13

-15

-17

-19

-21

-23

-25

-27

-29

-31

-33

-35

-37

-39

-41

-43

-47

-51

MUTE

-8

-4

2

8

-2

2

14

-10

-12

-14

-16

-18

-20

-22

-24

-26

-28

-32

-36

-40

-44

-48

-52

-56

MUTE

-6

0

6

-4

0

6

12

-8

-2

4

-6

-2

4

10

-10

-12

-14

-16

-18

-20

-22

-24

-26

-28

-32

-36

-40

-44

-48

MUTE

-4

2

-8

-4

2

8

-6

0

-10

-12

-14

-16

-18

-20

-22

-26

-30

-34

-38

-42

-46

-50

MUTE

-6

0

6

-8

-2

-8

-2

4

-10

-12

-14

-16

-18

-20

-22

-24

-26

-28

-32

-36

MUTE

-4

-10

-12

-14

-16

-18

-20

-22

-26

-30

-34

-38

-42

MUTE

-4

2

-6

0

-8

-2

-10

-12

-14

-16

-18

-20

-22

-24

-26

MUTE

-10

-12

-14

-16

-18

-20

-22

-26

-30

MUTE

-4

-6

-8

-10

-12

-14

-15

-18

-20

MUTE

*Based on HPV

X = Don’t care.

= 3.3V.

DD

______________________________________________________________________________________ 17

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Since the volume control (VOL) ADC is ratiometric to

HPV , any variations in HPV

are negated. The gain

DD

VOLUME CONTROL TRANSFER FUNCTION

step sizes are not constant; the step sizes are

0.5dB/step at the upper extreme, 2dB/step in the

midrange, and 4dB/step at the lower extreme. Figure 8

shows the transfer function of the volume control for a

3.3V supply.

40

20

GAIN1 = GAIN2 = GAIN3 = 1

HPV = 3.3V

DD

SPEAKER MODE

0

Low-Dropout Linear Regulator

The MAX9756/MAX9758s’ low-dropout linear regulator

(LDO) can be used to provide a clean power supply to

a CODEC or other circuitry. The LDO can be enabled

independently of the audio amplifiers. REGEN

-20

-40

-60

-80

HEADPHONE MODE

enables/disables the LDO, set REGEN = V

to enable

DD

the LDO or set REGEN = GND to disable. The LDO is

capable of providing up to 150mA continuous current

and features Maxim’s Dual Mode feedback. When SET

is connected to GND, the output is internally set to

approximately 4.65V. Adjust the output from 1.23V to

5V by connecting two external resistors, used as a volt-

age-divider, at SET (Figure 9).

0

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

(V)

V

VOL

Figure 8. Volume Control Transfer Function

The output voltage is set by the following equation:

OUT

R1

R2

⎛

⎞

V

= V

1+

⎜

⎝

⎟

⎠

OUT

SET

R1

R2

10pF

1µF

MAX9756

MAX9758

where V

= 1.23V.

SET

To simplify resistor selection:

⎛

⎞

V

OUT

GND

R1= R2

−1

⎜

⎟

⎝

⎠

SET

Since the input bias current at SET is nominally zero,

large resistance values can be used for R1 and R2 to

minimize power consumption without losing accuracy.

Up to 1.5MΩ is acceptable for R2.

To minimize the current consumption, it is desirable to

use high-value resistors (> 10kΩ for the external feed-

back divider (R1, R2). The input capacitance at SET

and the stray and wiring capacitance should be com-

pensated by placing a small capacitor (in the 10pF

range) across the upper feedback resistor R1 (see

Figure 9).

Figure 9. Adjustable Output Using External Feedback Resistors

The ESR of each capacitor should not exceed 40mΩ

for good stability up to the full-rated current (150mA).

Place the capacitors as close as possible to the device

to limit the parasitic resistance and inductance. There

is no upper limit to the amount of additional bypass

capacitance.

DirectDrive Headphone Amplifier

Unlike the MAX9756/MAX9757/MAX9758, conventional

single-supply headphone amplifiers typically have their

outputs biased at half the supply voltage for maximum

dynamic range. Large coupling capacitors are needed

to block this DC bias from the headphones. Without

these capacitors, a significant amount of DC current

flows to the headphone, resulting in unnecessary

power dissipation and possible damage to both head-

phone and headphone amplifier.

This capacitor creates a zero in the feedback loop to

reduce overshoot. Overcompensation can cause poor

stability in the high current range.

The regulator should be compensated with two 1µF

ceramic capacitors connected between IN and GND

and OUT and GND. X7R dielectric with 10% tolerance

is recommended.

18 ______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Maxim’s DirectDrive architecture uses a charge pump to

create an internal negative supply voltage. This allows the

MAX9756/MAX9757/MAX9758 headphone amplifier out-

put to be biased at GND, almost doubling the dynamic

range while operating from a single supply. With no DC

component, there is no need for the large DC-blocking

capacitors. Instead of two large capacitors (220µF, typ),

the MAX9756/MAX9757/MAX9758 charge pump requires

only two small ceramic capacitors (1µF typ), conserving

board space, reducing cost, and improving the frequen-

cy response of the headphone amplifier. See the Output

Power vs. Charge-Pump Capacitance graph in the

Typical Operating Characteristics for details of the possi-

ble capacitor values.

Larger values of C

physically larger, more expensive capacitors. Figure 10

shows the relationship between the size of C and

the resulting low-frequency attenuation. Note that the

-3dB point for a 16Ω headphone with a 100µF-blocking

capacitor is 100Hz, well within the audio band.

reduce the attenuation but are

OUT

Charge Pump

The MAX9756/MAX9757/MAX9758 feature a low-noise

inverting charge pump to generate the negative rail

necessary for DirectDrive headphone operation. The

switching frequency is well beyond the audio range,

and does not interfere with the audio signals. The

switch drivers feature a controlled switching speed that

minimizes noise generated by turn-on and turn-off tran-

sients. Limiting the switching speed of the charge

pump minimizes the di/dt noise caused by the parasitic

bond wire and trace inductance.

Low-Frequency Response

In addition to the cost and size disadvantages, the DC-

blocking capacitors limit the low-frequency response of

the amplifier. The impedance of the headphone load to

the DC-blocking capacitor forms a highpass filter with

the -3dB point determined by:

Headphone Sense Input (HPS)

The headphone sense input (HPS) monitors the head-

phone jack and automatically configures the MAX9756/

MAX9757/MAX9758 based upon the voltage applied at

HPS. A voltage of less than 0.8V enables the speaker

amplifier. A voltage of greater than 2V disables the

speaker amplifiers and enables the headphone ampli-

fiers. For automatic headphone detection, connect HPS

to the control pin of a 3-wire headphone jack as shown

in Figure 11. With no headphone present, the output

impedance of the headphone amplifier pulls HPS low.

When a headphone plug is inserted into the jack, the

control pin is disconnected from the tip contact and

1

f − 3dB =

2πR C

L

OUT

where R is the impedance of the headphone and

L

C

OUT

is the value of the DC-blocking capacitor.

The highpass filter is required by conventional single-

ended, single-supply headphone amplifiers to block the

midrail DC component of the audio signal from the

headphones. Depending on the -3dB point, the filter can

attenuate low-frequency signals within the audio band.

HPS is pulled to V

with 35µA.

DD

LOW-FREQUENCY ROLLOFF

V

(R = 16Ω)

L

DD

MAX9756/

0

MAX9757/

MAX9758

-1.5

35μA

DirectDrive

330μF

220μF

100μF

-3.0

-4.5

-6.0

SHUTDOWN

CONTROL

HPS

HPL

-7.5

-9.0

HPR

33μF

-10.5

-12.0

14kΩ

-13.5

-15.0

10

100

1k

FREQUENCY (Hz)

10k

100k

Figure 10. Low-Frequency Attenuation of Common DC-

Blocking Capacitor Values

Figure 11. HPS Configuration

______________________________________________________________________________________ 19

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

BIAS

⎛

⎞

V

The MAX9756/MAX9757/MAX9758 feature an internally

generated, power-supply independent, common-mode

bias voltage of 2.5V referenced to GND. BIAS provides

both click-and-pop suppression and sets the DC bias

level for the amplifiers. Choose the value of the bypass

capacitor as described in the BIAS Capacitor section.

No external load should be applied to BIAS. Any load

lowers the BIAS voltage, affecting the overall perfor-

mance of the device.

47kΩ

OUT(BEEP)

=

+ A

V(BEEPOUT)

⎜

⎟

V

R

B

⎝

⎠

IN(BEEP)

where 47kΩ is the value of the BEEP amplifier feedback

resistor, V

is the BEEP amplifier output, V

IN(BEEP)

BEEP

is the BEEP input amplitude, and V

is the total

OUT(BEEP)

) is given by the values

BEEP output signal. A

V(BEEPOUT

listed in Table 5. Note that V

must be higher than

BEEP

300mV . The BEEP amplifier can be set up as either

P-P

an attenuator, if the original alert signal amplitude is too

large, or to gain up the alert signal if it is below

BEEP Input

The MAX9756/MAX9757/MAX9758 feature an audible

alert beep input (BEEP) that accepts a mono system

alert signal and mixes it into the stereo audio path.

300mV . AC-couple the alert signal to BEEP. Choose

P-P

the value of the coupling capacitor as described in the

Input Filtering section. Multiple beep inputs can be

summed (Figure 12).

When the amplitude of V

exceeds 300mV

and

BEEP

P-P

the frequency of the beep signal is greater than 300Hz,

the beep signal is mixed into the active audio path

(speaker or headphone). If the signal at V

is either

BEEP

Table 5. BEEP Output Gain

< 300mV

or < 300Hz, the BEEP signal is not mixed

P-P

into the audio path. The amplitude of the BEEP signal at

the device output is roughly the amplitude V

the gain of the selected signal path.

A

V(BEEPOUT)

times

BEEP

GAIN3 GAIN2 GAIN1

HEADPHONE *

(V/V)

SPEAKER*

(V/V)

The input resistor (R ) sets the gain of the BEEP input

B

1.5

8.4

9.4

10

0

1

0

1

0

1

0

1

0

1

0

1

0

1

amplifier, and thus the amplitude of V

based on:

. Choose R

BEEP

B

1.78

1.5

V

× 47kΩ

IN(BEEP)

10

R

≤

B

V

15.8

18.8

20

BEEP

1.5

The total BEEP gain is given by:

1.78

20

*All output gains are for V

= GND.

VOL

R

B

0.47µF

47kΩ

SOURCE 1

SOURCE 2

SOURCE 3

47kΩ

R

B

47kΩ

SPEAKER/HEADPHONE

AMPLIFIER INPUTS

BEEP

V

BEEP

R

B

47kΩ

WINDOW

DETECTOR

(0.3V THRESHOLD)

P-P

MAX9756/

MAX9757/

MAX9758

FREQUENCY

DETECTOR

(300Hz THRESHOLD)

BIAS

Figure 12. Beep Input

20 ______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Shutdown (SHDN)

The MAX9756/MAX9757/MAX9758 feature a 0.2µA,

low-power shutdown mode that reduces quiescent cur-

V

+1

OUT(P-P)

rent consumption and extends battery life. Driving

SHDN low disables the drive amplifiers, bias circuitry,

and charge pump, and drives BIAS and all outputs to

2 x V

OUT(P-P)

GND. Connect SHDN to V

for normal operation.

DD

Click-and-Pop Suppression

-1

V

OUT(P-P)

Speaker Amplifier

The MAX9756/MAX9757/MAX9758 speaker amplifiers

feature Maxim’s comprehensive, industry-leading click-

and-pop suppression. During startup, the click-and-

pop suppression circuitry eliminates any audible

transient sources internal to the device. When entering

shutdown, both amplifier outputs ramp to GND quickly

and simultaneously.

Figure 13. Bridge-Tied Load Configuration

package is given in the Absolute Maximum Ratings

under Continuous Power Dissipation, or can be calcu-

lated by the following equation:

Headphone Amplifier

In conventional single-supply headphone amplifiers, the

output-coupling capacitor is a major contributor of audi-

ble clicks and pops. Since the MAX9756/MAX9757/

MAX9758 do not require output-coupling capacitors, no

audible transient occurs.

T

J(MAX) − T

A

P

=

DISSPKG(MAX)

θ

JA

where T

is +150°C, T is the ambient temperature,

A

J(MAX)

and θ is the reciprocal of the derating factor in °C/W as

JA

specified in the Absolute Maximum Ratings section. For

Additionally, the MAX9756/MAX9757/MAX9758 feature

extensive click-and-pop suppression that eliminates any

audible transient sources internal to the device. The

Turn-On/Turn-Off waveforms in the Typical Operating

Characteristics show that there are minimal spectral

components in the audible range at the output upon

startup and shutdown.

example, θ

of the 32-pin thin QFN package is

JA

+40.2°C/W. For optimum power dissipation, the exposed

paddle of the package should be connected to the

ground plane (see the Layout and Grounding section).

Output Power (Speaker Amplifier)

The increase in power delivered by the BTL configura-

tion directly results in an increase in internal power dis-

sipation over the single-ended configuration. The

maximum power dissipation for a given V

given by the following equation:

Applications Information

and load is

DD

BTL Speaker Amplifiers

The MAX9756/MAX9757/MAX9758 feature speaker

amplifiers designed to drive a load differentially, a config-

uration referred to as bridge-tied load (BTL). The BTL

configuration (Figure 13) offers advantages over the sin-

gle-ended configuration, where one side of the load is

connected to ground. Driving the load differentially dou-

bles the output voltage compared to a single-ended

amplifier under similar conditions.

2

2V

DD

P

=

DISS(MAX)

2

π R

L

If the power dissipation for a given application exceeds

the maximum allowed for a given package, either reduce

V

, increase load impedance, decrease the ambient

DD

temperature, or add heatsinking to the device or setting

PREF to limit output power to a safe level. Large output,

supply, and ground PC board traces improve the maxi-

mum power dissipation in the package. Thermal-over-

load protection limits total power dissipation in these

devices. When the junction temperature exceeds

+160°C, the thermal-protection circuitry disables the

amplifier output stage. The amplifiers are enabled once

the junction temperature cools by 15°C. This results in a

pulsing output under continuous thermal-overload condi-

tions as the device heats and cools.

Since the differential outputs are biased at 2.5V, there is

no net DC voltage across the load. This eliminates the

need for DC-blocking capacitors required for single-

ended amplifiers. These capacitors can be large and

expensive, can consume board space, and can degrade

low-frequency performance.

Power Dissipation and Heat Sinking

Under normal operating conditions, the MAX9756/

MAX9757/MAX9758 can dissipate a significant amount

of power. The maximum power dissipation for each

______________________________________________________________________________________ 21

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Output Power (Headphone Amplifier)

The headphone amplifiers have been specified for the

100

HPV = 5V

R = 16Ω

L

worst-case scenario—when both inputs are in phase.

DD

Under this condition, the drivers simultaneously draw

10

current from the charge pump, leading to a slight loss

in headroom of V . In typical stereo audio applica-

SS

tions, the left and right signals have differences in both

magnitude and phase, subsequently leading to an

increase in the maximum attainable output power.

Figure 14 shows the two extreme cases for in and out

of phase. In reality, the available power lies between

these extremes.

1

0.1

OUTPUTS IN PHASE

0.01

0.001

OUTPUTS 180° OUT OF PHASE

Power Supplies

The MAX9756/MAX9757/MAX9758 have different sup-

plies for each portion of the device, allowing for the opti-

mum combination of headroom and power dissipation

and noise immunity. The speaker amplifiers are pow-

40

80

180

100 120 140 160 200

0

20

60

OUTPUT POWER (mW)

Figure 14. Total Harmonic Distortion Plus Noise vs. Output

Power with Inputs In/Out of Phase (Headphone Mode)

ered from PV . PV

ranges from 4.5V to 5.5V. The

DD

headphone amplifiers are powered from HPV

and

DD

V

. HPV

is the positive supply of the headphone

SS

DD

amplifiers and ranges from 3V to 5.5V. V is the nega-

SS

Setting f

too high affects the amplifier’s low-fre-

tive supply of the headphone amplifiers. Connect V to

SS

-3dB

quency response. Use capacitors with low-voltage

coefficient dielectrics, such as tantalum or aluminum

electrolytic. Capacitors with high-voltage coefficients,

such as ceramics, may result in increased distortion at

low frequencies.

CPV . The charge pump is powered by CPV

.

DD

SS

CPV

ranges from 3V to 5.5V and should be the same

DD

potential as HPV . The charge pump inverts the volt-

DD

age at CPV , and the resulting voltage appears at

DD

CPV . The remainder of the device is powered by V

.

SS

DD

BIAS Capacitor

Component Selection

BIAS is the output of the internally generated DC bias

Input Filtering

voltage. The BIAS bypass capacitor, C

, improves

BIAS

The input capacitor (C ), in conjunction with the ampli-

IN

PSRR and THD+N by reducing power supply and other

noise sources at the common-mode bias node, and

also generates the startup/shutdown DC bias wave-

forms for the speaker amplifiers. Bypass BIAS with a

1µF capacitor to GND.

fier input resistance (R ), forms a highpass filter that

removes the DC bias from an incoming signal (see the

Typical Application Circuit). The AC-coupling capacitor

allows the amplifier to bias the signal to an optimum DC

level. Assuming zero source impedance, the -3dB point

of the highpass filter is given by:

Charge-Pump Capacitor Selection

Use capacitors with an ESR less than 100mΩ for opti-

mum performance. Low-ESR ceramic capacitors mini-

mize the output resistance of the charge pump. For

best performance over the extended temperature

range, select capacitors with an X7R dielectric. Table 6

lists suggested manufacturers.

1

f_−3dB

=

2πR C

IN IN

R

is the amplifier’s internal input resistance value

IN

given in the Electrical Characteristics. Choose C such

IN

that f

is well below the lowest frequency of interest.

-3dB

Table 6. Suggested Capacitor Manufacturers

SUPPLIER

Taiyo Yuden

TDK

PHONE

FAX

WEBSITE

800-384-2496

807-803-6100

800-925-0899

847-390-4405

www.t-yuden.com

www.component.tdk.com

22 ______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Flying Capacitor (C1)

The value of the flying capacitor (C1) affects the load

regulation and output resistance of the charge pump. A

C1 value that is too small degrades the device’s ability to

provide sufficient current drive, which leads to a loss of

output voltage. Increasing the value of C1 improves load

regulation and reduces the charge-pump output resis-

tance to an extent. See the Output Power vs. Charge-

Pump Capacitance graph in the Typical Operating

Characteristics. Above 2.2µF, the on-resistance of the

switches and the ESR of C1 and C2 dominate.

When considering the use of CPV

in this manner,

SS

note that the charge-pump voltage of CPV is roughly

SS

proportional to CPV

and is not a regulated voltage.

DD

Layout and Grounding

Proper layout and grounding are essential for optimum

performance. Use large traces for the power-supply

inputs and amplifier outputs to minimize losses due to

parasitic trace resistance, as well as route heat away

from the device. Good grounding improves audio per-

formance, minimizes crosstalk between channels, and

prevents any switching noise from coupling into the

audio signal. Connect CPGND, PGND, and GND

together at a single point on the PC board. Route

CPGND and all traces that carry switching transients

away from GND, PGND, and the traces and compo-

nents in the audio signal path.

Output Capacitor (C2)

The output capacitor value and ESR directly affect the

ripple at CPV . Increasing the value of C2 reduces

SS

output ripple. Likewise, decreasing the ESR of C2

reduces both ripple and output resistance. Lower

capacitance values can be used in systems with low

maximum output power levels. See the Output Power

vs. Charge-Pump Capacitance graph in the Typical

Operating Characteristics.

Connect all components associated with the charge

pump (C2 and C3) to the CPGND plane. Connect V

SS

and CPV

together at the device. Place the charge-

SS

pump capacitors (C1, C2, and C3) as close to the

device as possible. Bypass HPV and PV with a

DD

CPV

Bypass Capacitor

DD

1µF capacitor to GND. Place the bypass capacitors as

close to the device as possible.

The CPV

bypass capacitor (C3) lowers the output

DD

impedance of the power supply and reduces the impact

of the MAX9756/MAX9757/MAX9758’s charge-pump

Use large, low-resistance output traces. As load imped-

ance decreases, the current drawn from the device out-

puts increase. At higher current, the resistance of the

output traces decrease the power delivered to the load.

switching transients. Bypass CPV

with C3, the same

DD

value as C1, and place it physically close to CPV

and

DD

PGND (refer to the MAX9756/MAX9757/MAX9758

Evaluation Kit for a suggested layout).

For example, when compared to a 0Ω trace, a 100mΩ

trace reduces the power delivered to a 4Ω load from

2.1W to 2W. Large output, supply, and GND traces also

improve the power dissipation of the device. The

MAX9756/MAX9757/MAX9758 thin QFN package fea-

tures an exposed thermal pad on its underside. This pad

lowers the package’s thermal resistance by providing a

direct-heat conduction path from the die to the PC

board. Connect the exposed thermal pad to GND by

using a large pad and multiple vias to the GND plane.

Powering Other Circuits

from a Negative Supply

An additional benefit of the MAX9756/MAX9757/

MAX9758 is the internally generated negative supply

voltage (CPV ). CPV

is used by the MAX9756/

SS

MAX9757/MAX9758 to provide the negative supply for

the headphone amplifiers. It can also be used to power

other devices within a design. Current draw from

CPV should be limited to 5mA; exceeding this affects

SS

the operation of the headphone amplifier. A typical

application is a negative supply to adjust the contrast

of LCD modules.

______________________________________________________________________________________ 23

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

MAX9756 Block Diagram

4.5V TO 5.5V

0.1µF

100µF

V

DD

PV

DD

32

9, 19

MAX9756

C

1µF

IN

7

8

OUTL+

OUTL-

GAIN/

VOLUME

1

INL

DR

BTL

AMPLIFIER

LEFT-CHANNEL

AUDIO INPUT

25

35

29

CT

PEAK

DETECT

PREF

0.033µF

180kΩ

C

1µF

IN

21

20

OUTR+

OUTR-

GAIN/

VOLUME

CONTROL

RIGHT-

CHANNEL

AUDIO INPUT

36

INR

BTL

AMPLIFIER

BIAS 26

C

1µF

18

23

HPV

DD

BIAS

0V TO

HPV

28

2

VOL

3V TO 5.5V

VOLUME

AND GAIN

CONTROL

DD

1µF

GAIN1

HPS

V

DD

3

4

GAIN2

GAIN3

HEADPHONE

DETECTION

17 HPL

SHUTDOWN

CONTROL

27

5

SHDN

BEEP

R

B

0.47µF

47kΩ

BEEP

DETECTION

HPR

16

CPV

DD

10

3V TO 5.5V

1µF

11

13

C1P

C1N

C1

1µF

CHARGE

PUMP

CPGND

12

C1

1µF

CPV

V

SS 14

V

DD

SS 15

4.65V OUTPUT TO CODEC

1µF 1µF

REGEN

IN

34

30

24

33

OUT

SET

LDO

C3, C4

1µF

31

6, 22

GND

PGND

FIGURE SHOWN WITH AN ATTACK TIME = 495µs, RELEASE TIME = 990ms AND AN OUTPUT POWER LIMIT SET TO 1.2W, SPKR GAIN = 25.5dB, LDO SHOWN IN FIXED OUTPUT MODE, HPGAIN = 3dB.

24 ______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

MAX9757 Block Diagram

4.5V TO 5.5V

0.1µF

100µF

V

PV

DD

29

8, 18

MAX9757

C

1µF

IN

6

7

OUTL+

OUTL-

32

23

GAIN/

VOLUME

INL

DR

BTL

AMPLIFIER

LEFT-CHANNEL

AUDIO INPUT

30

27

CT

PEAK

DETECT

PREF

100µF

180kΩ

C

1µF

IN

20

19

OUTR+

OUTR-

GAIN/

VOLUME

CONTROL

RIGHT-

CHANNEL

AUDIO INPUT

31

INR

BTL

AMPLIFIER

BIAS 26

C

1µF

17

22

HPV

DD

BIAS

0V TO

HPV

28

1

VOL

3V TO 5.5V

VOLUME

AND GAIN

CONTROL

DD

1µF

GAIN1

HPS

V

DD

2

3

GAIN2

GAIN3

HEADPHONE

DETECTION

15 HPL

SHUTDOWN

CONTROL

25

4

SHDN

BEEP

R

B

0.47µF

47kΩ

BEEP

DETECTION

HPR

16

CPV

DD

9

3V TO 5.5V

1µF

10

12

C1P

C1N

C1

1µF

CHARGE

PUMP

CPGND

11

C2

1µF

CPV

V

SS 13

SS 14

28

5, 21

PGND

GND

FIGURE SHOWN WITH AN ATTACK TIME = 495µs, RELEASE TIME = 990ms AND AN OUTPUT POWER LIMIT SET TO 1.2W, SPKR GAIN = 25.5dB, HP GAIN = 3dB.

______________________________________________________________________________________ 25

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

MAX9758 Block Diagram

4.5V TO 5.5V

0.1µF

100µF

V

DD

PV

DD

29

8, 18

MAX9758

C

1µF

IN

6

7

OUTL+

OUTL-

32

INL

BTL

AMPLIFIER

LEFT-CHANNEL

AUDIO INPUT

VOLUME

C

1µF

IN

20

19

OUTR+

OUTR-

31

INR

RIGHT-CHANNEL

AUDIO INPUT

BTL

AMPLIFIER

VOLUME

BIAS 24

C

1µF

17

22

HPV

DD

BIAS

0V TO

HPV

26

1

VOL

3V TO 5.5V

VOLUME

AND GAIN

CONTROL

DD

1µF

GAIN1

HPS

V

DD

2

3

GAIN2

GAIN3

HEADPHONE

DETECTION

15 HPL

SHUTDOWN

CONTROL

25

4

SHDN

BEEP

0.47µF

R

B

BEEP

DETECTION

HPR

16

CPV

DD

9

3V TO 5.5V

1µF

10

12

C1P

C1N

C1

1µF

CHARGE

PUMP

CPGND

11

C2

1µF

CPV

V

SS 13

3.3V OUTPUT TO CODEC

SS 14

30

27

OUT

SET

REGEN

23

LDO

82kΩ

47kΩ

V

10pF

DD

1µF

28

5, 21

GND

PGND

FIGURE SHOWN WITH SPKR GAIN = 25.5dB, LDO SHOWN IN ADJUSTABLE OUTPUT MODE SET TO 3.3V, HP GAIN = 3dB.

26 ______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

System Diagram

4.5V TO 5.5V 3V TO 5.5V

10µF

1µF

V

DD

PV

DD

HPV

DD

IN

OUTL+

OUTL-

REGEN

INL

1µF

MAX9756

CODEC

INR

OUTR+

OUTR-

OUT

1µF

47kΩ

BEEP

HPL

SHDN

GAIN1

HPS

HPR

µC

GAIN2

GAIN3

HPV

DD

DR

VOL

3V TO 5.5V

1µF

CPV

C1P

DD

CPV

SS

V

1µF

C1N

SET

PREF

BIAS

CT

CPGND

180kΩ

BIAS

1µF

0.1µF

0.033µF

GND

PGND

______________________________________________________________________________________ 27

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Pin Configurations

TOP VIEW

26 25

23

27

24

22

21 20 19

VOL 28

PREF 29

SET 30

GND 31

18 HPV

17 HPL

16 HPR

DD

15

V

SS

V

32

33

14 CPV

13 C1N

DD

SS

MAX9756

IN

OUT 34

CT 35

INR 36

12 CPGND

C1P

10 CPV

11

DD

2

3

5

7

8

9

1

4

6

TQFN

6mm x 6mm

24 23 22 21 20 19 18 17

16

15

14

13

12

25

HPL

HPR

16

15

14

13

12

SHDN

SHDN 25

VOL 26

HPL

HPR

VOL 26

V

SS

27

28

29

30

31

32

V

SS

SET

27

28

29

30

31

32

PREF

GND

CPV

SS

GND

SS

MAX9758

MAX9757

V

C1N

V

C1N

DD

11 CPGND

OUT

INR

INL

11 CPGND

CT

INR

INL

10

9

C1P

CPV

10

9

C1P

CPV

DD

1

2

3

4

5

6

7

8

1

2

3

4

5

6

7

8

THIN QFN

5mm x 5mm

THIN QFN

5mm x 5mm

Chip Information

PROCESS: BICMOS

28 ______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information

go to www.maxim-ic.com/packages.)

D2

D

b

0.10 M

C A B

C

L

D2/2

D/2

k

L

MARKING

AAAAA

E/2

E2/2

C

(NE-1) X

e

L

E2

E

PIN # 1 I.D.

0.35x45°

DETAIL A

e/2

PIN # 1

I.D.

e

(ND-1) X

e

DETAIL B

e

L

C

L

C

L

L1

L

e

0.10

C

A

0.08

C

A3

A1

PACKAGE OUTLINE,

16, 20, 28, 32, 40L THIN QFN, 5x5x0.8mm

1

-DRAWING NOT TO SCALE-

I

21-0140

2

______________________________________________________________________________________ 29

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information

go to www.maxim-ic.com/packages.)

COMMON DIMENSIONS

EXPOSED PAD VARIATIONS

PKG.

SYMBOL MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX.

DOWN

BONDS

ALLOWED

16L 5x5

20L 5x5

28L 5x5

32L 5x5

40L 5x5

L

D2

E2

exceptions

PKG.

CODES

±0.15

MIN. NOM. MAX.

A

0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80

0.02 0.05 0.02 0.05 0.02 0.05 0.02 0.05 0.02 0.05

0.20 REF. 0.20 REF. 0.20 REF. 0.20 REF. 0.20 REF.

T1655-2

T1655-3

3.00 3.10 3.20 3.00 3.10 3.20

T1655N-1 3.00 3.10 3.20 3.00 3.10 3.20

YES

NO

**

A1

0

A3

b

0.25 0.30 0.35 0.25 0.30 0.35 0.20 0.25 0.30 0.20 0.25 0.30 0.15 0.20 0.25

4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10

T2055-3

T2055-4

T2055-5

T2855-3

3.00 3.10 3.20 3.00 3.10 3.20

YES

NO

D

E

**

YES

3.15 3.25 3.35 3.15 3.25 3.35 0.40

e

0.80 BSC.

0.25

0.65 BSC.

0.25

0.50 BSC.

0.25

0.50 BSC.

0.25

0.40 BSC.

3.15 3.25 3.35 3.15 3.25 3.35

**

YES

NO

k

-

0.25 0.35 0.45

T2855-4

T2855-5

2.60 2.70 2.80 2.60 2.70 2.80

3.15 3.25 3.35 3.15 3.25 3.35

**

L

0.30 0.40 0.50 0.45 0.55 0.65 0.45 0.55 0.65 0.30 0.40 0.50 0.40 0.50 0.60

L1

-

0.30 0.40 0.50

NO

YES

T2855-6

T2855-7

**

N

ND

NE

16

4

20

5

28

7

32

8

40

10

2.80

2.60 2.70

2.60 2.70 2.80

T2855-8

3.15 3.25 3.35 3.15 3.25 3.35 0.40

WHHB

WHHC

WHHD-1

WHHD-2

-----

JEDEC

T2855N-1 3.15 3.25 3.35 3.15 3.25 3.35

NO

YES

NO

YES

NO

**

3.20

3.00 3.10 3.20

T3255-3

T3255-4

T3255-5

3.00 3.10

3.00 3.10 3.20 3.00 3.10 3.20

3.20

NOTES:

3.00 3.10

3.00 3.10 3.20

1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.

2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES.

3. N IS THE TOTAL NUMBER OF TERMINALS.

T3255N-1 3.00 3.10 3.20 3.00 3.10 3.20

T4055-1 3.20 3.30 3.40 3.20 3.30 3.40

YES

**^{SEE COMMON DIMENSIONS TABLE}

4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL

CONFORM TO JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE

OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE TERMINAL #1

IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE.

5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN

0.25 mm AND 0.30 mm FROM TERMINAL TIP.

6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.

7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION.

8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS.

9. DRAWING CONFORMS TO JEDEC MO220, EXCEPT EXPOSED PAD DIMENSION FOR

T2855-3 AND T2855-6.

10. WARPAGE SHALL NOT EXCEED 0.10 mm.

11. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY.

12. NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY.

13. LEAD CENTERLINES TO BE AT TRUE POSITION AS DEFINED BY BASIC DIMENSION "e", ±0.05.

PACKAGE OUTLINE,

16, 20, 28, 32, 40L THIN QFN, 5x5x0.8mm

2

-DRAWING NOT TO SCALE-

21-0140

I

2

30 ______________________________________________________________________________________

2.3W Stereo Speaker Amplifiers and DirectDrive

Headphone Amplifiers with Automatic Level Control

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information

go to www.maxim-ic.com/packages.)

(NE-1) X

e

E

E/2

k

D/2

C

(ND-1) X

e

D

D2

L

D2/2

e

b

E2/2

L

C

L

k

E2

e

L

C

L

L1

L

e

A

A1

A2

PACKAGE OUTLINE

36, 40, 48L THIN QFN, 6x6x0.8mm

1

F

21-0141

2

NOTES:

1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.

2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES.

3. N IS THE TOTAL NUMBER OF TERMINALS.

4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1

SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE

ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE.

5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm

FROM TERMINAL TIP.

6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.

7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION.

8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS.

9. DRAWING CONFORMS TO JEDEC MO220, EXCEPT FOR 0.4mm LEAD PITCH PACKAGE T4866-1.

10. WARPAGE SHALL NOT EXCEED 0.10 mm.

11. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY.

12. NUMBER OF LEADS SHOWN FOR REFERENCE ONLY.

PACKAGE OUTLINE

36, 40, 48L THIN QFN, 6x6x0.8mm

2

F

21-0141

2

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 31

Printed USA

is a registered trademark of Maxim Integrated Products, Inc.

Quijano


型号：	MAX9757
厂家：	MAXIM INTEGRATED PRODUCTS
描述：	2.3W Stereo Speaker Amplifiers and DirectDrive Headphone Amplifiers with Automatic Level Control
文件：	总31页 (文件大小：790K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

MAX9757 [MAXIM]

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