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MAX9768BETG/V+ [MAXIM]

10W Mono Class D Speaker Amplifier with Volume Control;
MAX9768BETG/V+
型号： MAX9768BETG/V+
厂家： MAXIM INTEGRATED PRODUCTS    MAXIM INTEGRATED PRODUCTS
描述：

10W Mono Class D Speaker Amplifier with Volume Control

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EVALUATION KIT AVAILABLE  
Click here for production status of specific part numbers.  
MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
General Description  
The MAX9768 mono 10W Class D speaker amplifier pro-  
vides high-quality, efficient audio power with an integrated  
volume control function.  
Features  
● 10W Output (8Ω, PV  
= 14V, THD+N = 10%)  
DD  
● Spread-Spectrum Modulation  
● Meets EN55022B EMC with Ferrite Bead Filters  
● Amplifier Operation from 4.5V to 14V Supply  
The MAX9768 features a 64-step dual-mode (analog or  
digitally programmable) volume control and mute function.  
The audio amplifier operates from a 4.5V to 14V single  
supply and can deliver up to 10W into an 8Ω speaker with  
a 14V supply.  
2
● 64-Step Integrated Volume Control (I C or Analog)  
● Low 0.08% THD+N (R = 8Ω, P  
= 6W)  
OUT  
L
● High 77dB PSRR  
A selectable spread-spectrum mode reduces EMI-  
radiated emissions, allowing the device to pass EMC  
testing with ferrite bead filters and cable lengths up to 1m.  
The MAX9768 can be synchronized to an external clock,  
allowing synchronization of multiple Class D amplifiers.  
● Two t  
Times Offered  
ON  
• MAX9768—220ms  
• MAX9768B—15ms  
● Low-Power Shutdown Mode (0.5μA)  
● Short-Circuit and Thermal-Overload Protection  
The MAX9768 features high 77dB PSRR, low 0.08%  
THD+N, and SNR up to 97dB. Robust short-circuit and  
thermal-overload protection prevent device damage during  
a fault condition. The MAX9768 is available in a 24-pin thin  
QFN-EP (4mm x 4mm x 0.8mm) package and is specified  
over the extended -40°C to +85°C temperature range.  
Pin Configuration located toward end of data sheet.  
Ordering Information located at end of data sheet.  
Applications  
● Notebook Computers  
● Flat-Panel Displays  
● Multimedia Monitors  
● GPS Navigation Systems  
● Security/Personal Mobile Radio  
Simplified Block Diagram  
MAX9768 EMI WITH FERRITE BEAD FILTERS  
3.3V  
4.5V TO 14V  
(V = 12V, 1m CABLE, 8Ω LOAD)  
DD  
40  
35  
30  
25  
20  
15  
10  
5
SPEAKER  
AUDIO  
INPUT  
FILTERLESS  
CLASS D  
SPEAKER  
OUTPUT  
OVER 20dB MARGIN  
TO EN55022B LIMIT  
SHDN  
MUTE  
ANALOG OR  
I C VOLUME  
CONTROL  
2
0
MAX9768  
0
100 200 300 400 500 600 700 800 900 1000  
FREQUENCY (MHz)  
19-0854; Rev 5; 11/20  
MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Absolute Maximum Ratings  
PV  
to PGND......................................................-0.3V to +16V  
Continuous Power Dissipation (T = +70°C)  
A
DD  
V
to GND ............................................................-0.3V to +4V  
Single-Layer Board:  
DD  
SCLK, SDA/VOL to GND ........................................-0.3V to +4V  
FB, SYNCOUT ......................................... -0.3V to (V + 0.3V)  
24-Pin Thin QFN 4mm x 4mm,  
(derate 20.8mW/°C above +70°C) ................................1.67W  
Multilayer Board:  
DD  
BOOT_ to OUT_......................................................-0.3V to +4V  
OUT_ to GND.........................................-0.3V to (PV + 0.3V)  
24-Pin Thin QFN 4mm x 4mm,  
DD  
PGND to GND......................................................-0.3V to +0.3V  
Any Other Pin to GND.............................................-0.3V to +4V  
OUT_ Short-Circuit Duration.....................................Continuous  
(derate 27.8mW/°C above +70°C) ................................2.22W  
θ
θ
, Single-Layer Board..................................................48°C/W  
, Multilayer Board.......................................................36°C/W  
JA  
JA  
Continuous Current (PV , PGND, OUT_) .........................2.2A  
Continuous Input Current (Any Other Pin).......................±20mA  
Continuous Input Current (FB_).......................................±60mA  
Operating Temperature Range........................... -40°C to +85°C  
Storage Temperature Range............................ -65°C to +150°C  
Lead Temperature (soldering, 10s) .................................+300°C  
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  
(PV  
= 12V, V  
= 3.3V, V  
= V  
= 0, V  
= V , V  
= 0; Max volume setting; speaker load resistor connected  
DD  
DD  
GND  
PGND  
SHDN  
DD  
MUTE  
between OUT+ and OUT-, R = ∞, unless otherwise noted. C  
= 2.2μF, C1 = C2 = 0.1μF, C = 0.47μF, R = 20kΩ, R = 30kΩ,  
L
BIAS  
IN  
IN  
F
SSM mode. Filterless modulation mode (see the Functional Diagram/Typical Application Circuit). T = T  
to T , unless otherwise  
A
MIN  
MAX  
noted. Typical values are at T = +25°C.) (Note 1)  
A
PARAMETER  
GENERAL  
SYMBOL  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
Speaker Supply Voltage  
Range  
PV  
Inferred from PSRR test  
4.5  
2.7  
14.0  
V
V
DD  
Supply Voltage Range  
V
Inferred from PSRR and UVLO test  
3.6  
14.2  
7.6  
7.6  
50  
DD  
I
7
4
VDD  
Quiescent Current  
Filterless modulation  
mA  
I
I
PVDD  
Classic PWM modulation  
4
Shutdown Current  
I
= I  
+ I , SHDN = GND, T = +25°C  
0.5  
±2  
±2  
220  
15  
1.5  
µA  
SHDN  
SHDN  
PVDD  
DD  
A
Filterless modulation, V  
Filterless modulation, V  
MAX9768  
= V , T = +25°C  
±12.5  
±14  
MUTE  
MUTE  
DD  
A
Output Offset  
V
mV  
OS  
= 0V, T = +25°C  
A
Turn-On Time  
t
ms  
ON  
MAX9768B  
Common-Mode Bias Voltage  
V
V
BIAS  
Input Amplifier Output-  
Voltage Swing High  
Specified as  
V
R = 2kΩ connect to 1.5V  
3.6  
6
100  
50  
mV  
OH  
L
V
- V  
DD OH  
Input Amplifier Output-  
Voltage Swing Low  
Specified as  
V - GND  
OL  
V
R = 2kΩ connect to 1.5V  
mV  
mA  
OL  
L
Input Amplifier Output  
Short-Circuit Current Limit  
±60  
1.8  
Input Amplifier Gain-  
Bandwidth Product  
GBW  
MHz  
SPEAKER AMPLIFIERS  
Max volume setting; from FB to amplifier outputs  
|(OUT+) - (OUT-)|; excludes external gain resistors  
Internal Gain  
A
29.27  
30.1  
31.00  
dB  
VMAX  
Maxim Integrated  
│ 2  
www.maximintegrated.com  
MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Electrical Characteristics (continued)  
((PV  
= 12V, V  
= 3.3V, V  
= V  
= 0, V  
= V , V = 0; Max volume setting; speaker load resistor connected  
DD MUTE  
DD  
DD  
GND  
PGND  
SHDN  
between OUT+ and OUT-, R = ∞, unless otherwise noted. C  
= 2.2μF, C1 = C2 = 0.1μF, C = 0.47μF, R = 20kΩ, R = 30kΩ,  
L
BIAS  
IN  
IN  
F
SSM mode. Filterless modulation mode (see the Functional Diagram/Typical Application Circuit). T = T  
to T , unless otherwise  
A
MIN  
MAX  
noted. Typical values are at T = +25°C.) (Note 1)  
A
PARAMETER  
Efficiency (Note 2)  
SYMBOL  
CONDITIONS  
MIN  
TYP  
87  
MAX  
UNITS  
Filterless modulation  
Classic PWM modulation  
P
= 8W, f  
=
OUT  
IN  
η
%
1kHz, R = 8Ω  
85  
L
R = 8Ω, THD+N = 1%,  
filterless modulation  
L
1.3  
1.7  
9
PV  
PV  
PV  
= 5V  
DD  
DD  
DD  
R = 8Ω, THD+N = 10%,  
L
filterless modulation  
R = 8Ω, THD+N = 10%,  
L
classic PWM modulation  
Output Power (Note 2)  
P
= 12V  
= 14V  
W
OUT  
R = 8Ω, THD+N = 10%,  
filterless modulation  
L
9
R = 8Ω, THD+N = 10%,  
L
10  
10  
classic PWM modulation  
R = 8Ω, THD+N = 10%,  
L
filterless modulation  
Soft Output Current Limit  
Hard Output Current Limit  
I
1.75  
2
2.5  
0.09  
0.08  
94  
A
A
LIM  
I
SC  
Filterless modulation  
Total Harmonic Distortion  
Plus Noise (Note 2)  
f = 1kHz, R = 8Ω,  
L
THD+N  
%
P
= 5W  
Classic PWM modulation  
OUT  
FFM  
Unweighted  
SSM  
0dB = 8W, R =  
L
93  
8Ω, BW = 22Hz to  
22kHz, filterless  
modulation mode  
FFM  
A-weighted  
SSM  
97  
97  
Signal-to-Noise Ratio  
(Note 2)  
SNR  
dB  
FFM  
Unweighted  
SSM  
93  
0dB = 8W, R =  
L
89  
8Ω, BW = 22Hz  
to 22kHz, classic  
PWM modulation  
FFM  
A-weighted  
SSM  
97  
91  
MUTE Attenuation (Note 3)  
0dB = 8W, f = 1kHz  
115  
dB  
dB  
V
= 2.7V to 3.6V, filterless modulation,  
DD  
52  
67  
68  
84  
T
= +25°C  
A
PV  
= 4.5V to 14V, filterless modulation,  
Power-Supply Rejection  
Ratio  
DD  
PSRR  
T
A
= +25°C  
f = 1kHz, V  
= 200mV  
= 100mV  
on PV  
DD  
77  
60  
RIPPLE  
RIPPLE  
P-P  
P-P  
f = 1kHz, V  
on V  
DD  
SYNC = GND  
SYNC = unconnected  
1060  
1296  
1200  
1440  
1320  
1584  
Oscillator Frequency  
f
kHz  
OCS  
SYNC = V  
mode)  
(spread-spectrum modulation  
1200  
±30  
DD  
Maxim Integrated  
│ 3  
www.maximintegrated.com  
MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Electrical Characteristics (continued)  
((PV  
= 12V, V  
= 3.3V, V  
= V  
= 0, V  
= V , V = 0; Max volume setting; speaker load resistor connected  
DD MUTE  
DD  
DD  
GND  
PGND  
SHDN  
between OUT+ and OUT-, R = ∞, unless otherwise noted. C  
= 2.2μF, C1 = C2 = 0.1μF, C = 0.47μF, R = 20kΩ, R = 30kΩ,  
L
BIAS  
IN  
IN  
F
SSM mode. Filterless modulation mode (see the Functional Diagram/Typical Application Circuit). T = T  
to T  
, unless otherwise  
A
MIN  
MAX  
noted. Typical values are at T = +25°C.) (Note 1)  
A
PARAMETER  
SYMBOL  
CONDITIONS  
MIN  
265  
324  
TYP  
300  
360  
MAX  
330  
UNITS  
SYNC = GND  
SYNC = unconnected  
396  
Class D Switching Frequency  
kHz  
SYNC = V  
mode)  
(spread-spectrum modulation  
300  
±7.5  
DD  
SYNC Frequency Lock  
Range  
1000  
1600  
kHz  
%
Minimum SYNC Frequency  
Lock Duty Cycle  
40  
60  
Maximum SYNC Frequency  
Lock Duty Cycle  
%
%
Gain Matching  
Full volume (ideal matching for R and R )  
2
52.6  
48  
IN  
F
Into shutdown  
Out of shutdown  
Into mute  
Peak voltage, 32 samples  
per second, A-weighted, R  
IN  
Click-and-Pop Level (Note 2)  
K
dBV  
CP  
x C ≤ 10ms to guarantee  
67  
IN  
clickless/popless operation  
Out of mute  
57  
Input Impedance  
Input Hysteresis  
9.5dB Gain Voltage  
Full Mute Voltage  
DC volume control mode (SDA/VOL)  
DC volume control mode (SDA/VOL)  
DC volume control mode (SDA/VOL)  
DC volume control mode (SDA/VOL)  
100  
11  
MΩ  
mV  
V
0.1 x V  
0.9 x V  
DD  
V
DD  
DIGITAL INPUTS (SHDN, MUTE, ADDR1, ADDR2, SYNC)  
SYNC  
2.33  
Input-Voltage High  
Input-Voltage Low  
Input Leakage Current  
V
V
V
IH  
All other pins  
SYNC  
0.7 x V  
DD  
0.8  
0.3 x V  
V
IL  
All other pins  
DD  
I
T
= +25°C  
±7.5  
±13  
SYNC  
A
µA  
I
All other digital inputs, T = +25°C  
A
±1  
LK  
DIGITAL OUTPUT (SYNCOUT)  
Output-Voltage High  
Output-Voltage Low  
Rise/Fall Time  
Load = 1mA  
Load = 1mA  
V
- 0.3  
V
V
DD  
0.3  
C = 10pF  
5
ns  
L
Maxim Integrated  
│ 4  
www.maximintegrated.com  
MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Electrical Characteristics (continued)  
((PV  
= 12V, V  
= 3.3V, V  
= V  
= 0, V  
= V , V = 0; Max volume setting; speaker load resistor connected  
DD MUTE  
DD  
DD  
GND  
PGND  
SHDN  
between OUT+ and OUT-, R = ∞, unless otherwise noted. C  
= 2.2μF, C1 = C2 = 0.1μF, C = 0.47μF, R = 20kΩ, R = 30kΩ,  
L
BIAS  
IN  
IN  
F
SSM mode. Filterless modulation mode (see the Functional Diagram/Typical Application Circuit). T = T  
to T , unless otherwise  
A
MIN  
MAX  
noted. Typical values are at T = +25°C.) (Note 1)  
A
PARAMETER  
SYMBOL  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
THERMAL PROTECTION  
Thermal Shutdown Threshold  
150  
15  
°C  
°C  
Thermal Shutdown  
Hysteresis  
DIGITAL INPUTS (SCLK, SDA/VOL)  
Input-Voltage High  
V
0.7 x V  
V
V
IH  
DD  
Input-Voltage Low  
V
0.3 x V  
DD  
IL  
Input High Leakage Current  
Input Low Leakage Current  
Input Hysteresis  
I
V
V
= V , T = +25°C  
±1  
±1  
µA  
µA  
V
IH  
IN  
DD  
A
I
= GND, T = +25°C  
A
IL  
IN  
0.1 x V  
5
DD  
Input Capacitance  
C
pF  
IN  
DIGITAL OUTPUTS (SDA/VOL)  
Output High Current  
I
V
= V  
DD  
1
µA  
V
OH  
OH  
Output Low Voltage  
V
I
= 3mA  
0.4  
OL  
OL  
2
I C TIMING CHARACTERISTICS (Figure 3)  
Serial Clock  
f
400  
kHz  
µs  
SCL  
Bus Free Time Between a  
STOP and START  
Condition  
t
1.3  
BUF  
Hold Time (Repeated)  
START Condition  
t
0.6  
0.6  
µs  
µs  
HD,STA  
Repeated START Condition  
Setup Time  
t
SU,STA  
STOP Condition Setup Time  
Data Hold Time  
t
0.6  
0
µs  
µs  
ns  
µs  
µs  
SU,STO  
t
0.9  
HD,DAT  
Data Setup Time  
t
100  
1.3  
0.6  
SU,DAT  
SCL Clock Low Period  
SCL Clock High Period  
t
LOW  
t
HIGH  
Rise Time of SDA and SCL,  
Receiving  
20 +  
0.1Cb  
t
(Note 4)  
(Note 4)  
300  
300  
ns  
ns  
R
Fall Time of SDA and SCL,  
Receiving  
20 +  
0.1Cb  
t
F
Maxim Integrated  
│ 5  
www.maximintegrated.com  
MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Electrical Characteristics (continued)  
((PV  
= 12V, V  
= 3.3V, V  
= V  
= 0, V  
= V , V = 0; Max volume setting; speaker load resistor connected  
DD MUTE  
DD  
DD  
GND  
PGND  
SHDN  
between OUT+ and OUT-, R = ∞, unless otherwise noted. C  
= 2.2μF, C1 = C2 = 0.1μF, C = 0.47μF, R = 20kΩ, R = 30kΩ,  
L
BIAS  
IN  
IN  
F
SSM mode. Filterless modulation mode (see the Functional Diagram/Typical Application Circuit). T = T  
to T , unless otherwise  
A
MIN  
MAX  
noted. Typical values are at T = +25°C.) (Note 1)  
A
PARAMETER  
Fall Time of SDA,  
SYMBOL  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
20 +  
0.1Cb  
t
(Note 4)  
250  
ns  
F
Transmitting  
Pulse Width of Spike  
Suppressed  
t
0
50  
ns  
SP  
Capacitive Load for Each  
Bus Line  
C
400  
pF  
b
Note 1: All devices are 100% production tested at T = +25°C. All temperature limits are guaranteed by design.  
A
Note 2: Testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For R = 8Ω, L = 68μH.  
L
Note 3: Device muted by either asserting MUTE or minimum V setting.  
OL  
Note 4: C = total capacitance of one bus line in pF.  
b
Typical Operating Characteristics  
((PV  
= 12V, V  
= 3.3V, V  
= V  
= 0, V  
= 0; 0dB volume setting; all speaker load resistors connected between OUT+  
DD  
DD  
GND  
PGND  
MUTE  
and OUT-, R = 8Ω, unless otherwise noted. C  
= 2.2μF, C1 = C2 = 0.1μF, C = 0.47μF, R = 20kΩ, R = 30kΩ, spread-spectrum  
L
BIAS  
IN  
IN  
FB  
modulation mode.)  
TOTAL HARMONIC DISTORTION  
PLUS NOISE vs. FREQUENCY  
TOTAL HARMONIC DISTORTION  
PLUS NOISE vs. FREQUENCY  
TOTAL HARMONIC DISTORTION  
PLUS NOISE vs. FREQUENCY  
10  
10  
10  
PV = 12V  
DD  
PV = 12V  
DD  
PV = 5V  
DD  
R = 8Ω  
L
R = 8Ω  
L
R = 8Ω  
L
FILTERLESS MODULATION  
PWM MODE  
FILTERLESS MODULATION  
1
0.1  
1
0.1  
1
0.1  
OUTPUT POWER = 1W  
OUTPUT POWER = 6W  
OUTPUT POWER = 5W  
OUTPUT POWER = 300mW  
0.01  
0.001  
OUTPUT POWER = 2W  
OUTPUT POWER = 2W  
0.01  
0.01  
10  
100  
1k  
10k  
100k  
10  
100  
1k  
FREQUENCY (Hz)  
10k  
100k  
10  
100  
1k  
10k  
100k  
FREQUENCY (Hz)  
FREQUENCY (Hz)  
Maxim Integrated  
│ 6  
www.maximintegrated.com  
MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Typical Operating Characteristics (continued)  
((PV  
= 12V, V  
= 3.3V, V  
= V  
= 0, V  
= 0; 0dB volume setting; all speaker load resistors connected between OUT+  
DD  
DD  
GND  
PGND  
MUTE  
and OUT-, R = 8Ω, unless otherwise noted. C  
= 2.2μF, C1 = C2 = 0.1μF, C = 0.47μF, R = 20kΩ, R = 30kΩ, spread-spectrum  
L
BIAS  
IN  
IN  
FB  
modulation mode.)  
TOTAL HARMONIC DISTORTION  
PLUS NOISE vs. FREQUENCY  
TOTAL HARMONIC DISTORTION  
PLUS NOISE vs. FREQUENCY  
TOTAL HARMONIC DISTORTION  
PLUS NOISE vs. FREQUENCY  
10  
10  
1
10  
PV = 12V  
DD  
PV = 5V  
DD  
R = 8Ω  
L
PV = 12V  
DD  
R = 8Ω  
L
R = 8Ω  
L
FILTERLESS MODULATION  
PWM MODE  
1
PWM MODE  
P
= 4W  
OUT  
1
0.1  
P
= 4W  
OUT  
FIXED-FREQUENCY  
MODULATION  
FIXED-FREQUENCY  
MODULATION  
OUTPUT POWER = 300mW  
0.1  
0.1  
0.01  
SPREAD-SPECTRUM  
MODULATION  
0.01  
0.01  
0.001  
SPREAD-SPECTRUM  
MODULATION  
OUTPUT POWER = 800mW  
0.001  
0.001  
10  
100  
1k  
10k  
100k  
10  
100  
1k  
10k  
100k  
10  
100  
1k  
10k  
100k  
FREQUENCY (Hz)  
FREQUENCY (Hz)  
FREQUENCY (Hz)  
TOTAL HARMONIC DISTORTION  
PLUS NOISE vs. OUTPUT POWER  
TOTAL HARMONIC DISTORTION  
PLUS NOISE vs. OUTPUT POWER  
TOTAL HARMONIC DISTORTION  
PLUS NOISE vs. OUTPUT POWER  
100  
10  
1
100  
10  
1
100  
10  
1
PV = 12V  
PV = 12V  
PV = 5V  
DD  
DD  
DD  
R = 8Ω  
R = 8Ω  
R = 8Ω  
L
L
L
FILTERLESS MODULATION  
PWM MODE  
FILTERLESS MODULATION  
f
IN  
= 10kHz  
f = 10kHz  
IN  
f
= 10kHz  
IN  
0.1  
0.1  
0.1  
0.01  
0.01  
0.01  
f
= 1kHz  
IN  
f
IN  
= 100Hz  
f
= 100Hz  
0.5  
f
= 1kHz  
IN  
f
= 100Hz  
2
IN  
IN  
f
= 1kHz  
IN  
0.001  
0.001  
0.001  
0
2
4
6
8
10  
12  
0
4
6
8
10  
0
1.0  
1.5  
2.0  
OUTPUT POWER (W)  
OUTPUT POWER (W)  
OUTPUT POWER (W)  
TOTAL HARMONIC DISTORTION  
PLUS NOISE vs. OUTPUT POWER  
TOTAL HARMONIC DISTORTION  
PLUS NOISE vs. OUTPUT POWER  
TOTAL HARMONIC DISTORTION  
PLUS NOISE vs. OUTPUT POWER  
100  
10  
1
100  
10  
100  
10  
PV = 5V  
PV = 12V  
PV = 12V  
DD  
DD  
DD  
R = 8Ω  
R = 8Ω  
R = 8Ω  
L
L
L
PWM MODE  
f
= 1kHz  
f = 1kHz  
IN  
PWM MODE  
IN  
FILTERLESS MODULATION  
f
= 10kHz  
IN  
1
1
FIXED-FREQUENCY  
MODULATION  
FIXED-FREQUENCY  
MODULATION  
0.1  
0.1  
0.01  
0.1  
0.01  
0.01  
SPREAD-SPECTRUM  
MODULATION  
f
= 100Hz  
0.4  
IN  
SPREAD-SPECTRUM  
MODULATION  
f
= 1kHz  
1.2  
IN  
0.001  
0
0.8  
1.6  
2.0  
0
2
4
6
8
10  
0
2
4
6
8
10  
OUTPUT POWER (W)  
OUTPUT POWER (W)  
OUTPUT POWER (W)  
Maxim Integrated  
│ 7  
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Typical Operating Characteristics (continued)  
((PV  
= 12V, V  
= 3.3V, V  
= V  
= 0, V  
= 0; 0dB volume setting; all speaker load resistors connected between OUT+  
DD  
DD  
GND  
PGND  
MUTE  
and OUT-, R = 8Ω, unless otherwise noted. C  
= 2.2μF, C1 = C2 = 0.1μF, C = 0.47μF, R = 20kΩ, R = 30kΩ, spread-spectrum  
L
BIAS  
IN  
IN  
FB  
modulation mode.)  
EFFICIENCY vs. OUTPUT POWER  
EFFICIENCY vs. OUTPUT POWER  
EFFICIENCY vs. SUPPLY VOLTAGE  
100  
100  
95  
FILTERLESS MODULATION  
f
= 1kHz  
IN  
FILTERLESS MODULATION  
PWM MODE  
90  
80  
70  
60  
90  
80  
70  
60  
R = 8Ω  
FILTERLESS MODULATION  
L
92  
89  
86  
83  
80  
PWM MODE  
THD+N = 10%  
50  
40  
50  
40  
30  
20  
10  
0
30  
20  
10  
0
THD+N = 1%  
PV = 12V  
PV = 5V  
DD  
DD  
f
IN  
= 1kHz  
f
IN  
= 1kHz  
R = 8Ω  
L
R = 8Ω  
L
0
2
4
6
8
10  
0
0.5  
1.0  
1.5  
2.0  
4.5  
6.5  
8.5  
10.5  
12.5  
14.5  
OUTPUT POWER (W)  
OUTPUT POWER (W)  
SUPPLY VOLTAGE (V)  
EFFICIENCY vs. SUPPLY VOLTAGE  
OUTPUT POWER vs. SUPPLY VOLTAGE  
OUTPUT POWER vs. SUPPLY VOLTAGE  
95  
92  
89  
86  
14  
12  
12  
10  
8
f
= 1kHz  
R = 8Ω  
R = 4Ω  
L
IN  
L
R = 8Ω  
PWM MODULATION  
f
= 1kHz  
f = 1kHz  
L
IN  
IN  
PWM MODE  
PWM MODE  
10  
8
THD+N = 10%  
THD+N = 10%  
THD+N = 10%  
6
4
2
6
THD+N = 1%  
4
THD+N = 1%  
THD+N = 1%  
83  
80  
2
0
0
4.5  
6.5  
8.5  
10.5  
12.5  
14.5  
4
6
8
10  
12  
14  
4
6
8
10  
12  
14  
SUPPLY VOLTAGE (V)  
SUPPLY VOLTAGE (V)  
SUPPLY VOLTAGE (V)  
OUTPUT POWER vs. LOAD RESISTANCE  
OUTPUT POWER vs. LOAD RESISTANCE  
CASE TEMPERATURE vs. OUTPUT POWER  
12  
10  
8
3.5  
3.0  
2.5  
2.0  
1.5  
1.0  
0.5  
0
90  
80  
70  
60  
50  
PV = 12V  
DD  
f = 1kHz  
PWM MODE  
PV = 5V  
DD  
f = 1kHz  
PWM MODE  
f = 1kHz  
IN  
R = 8Ω  
L
PV = 14V  
DD  
THD+N = 10%  
THD+N = 10%  
6
4
2
THD+N = 1%  
40  
30  
20  
PV = 12V  
DD  
THD+N = 1%  
10  
0
0
0
5
10  
15  
20  
25  
30  
0
5
10  
15  
20  
25  
30  
0
2
4
6
8
10  
12  
LOAD RESISTANCE (Ω)  
LOAD RESISTANCE (Ω)  
OUTPUT POWER (W)  
Maxim Integrated  
│
8
www.maximintegrated.com  
MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Typical Operating Characteristics (continued)  
((PV  
= 12V, V  
= 3.3V, V  
= V  
= 0, V  
= 0; 0dB volume setting; all speaker load resistors connected between OUT+  
DD  
DD  
GND  
PGND  
MUTE  
and OUT-, R = 8Ω, unless otherwise noted. C  
= 2.2μF, C1 = C2 = 0.1μF, C = 0.47μF, R = 20kΩ, R = 30kΩ, spread-spectrum  
L
BIAS  
IN  
IN  
FB  
modulation mode.)  
POWER-SUPPLY REJECTION RATIO (PV  
vs. FREQUENCY  
)
DD  
POWER-SUPPLY REJECTION RATIO (V  
)
DD  
OUTPUT WAVEFORM  
(FILTERLESS MODULATION)  
vs. FREQUENCY  
0
0
MAX9768 toc24  
PV = 12V  
DD  
V = 3.3V  
DD  
V = 100mV  
RIPPLE P-P  
-10  
-20  
-30  
-40  
-10  
-20  
-30  
-40  
V
= 100mV  
RIPPLE  
P-P  
R = 8Ω  
R = 8Ω  
L
L
5V/div  
5V/div  
PWM MODE  
-50  
-50  
PWM MODE  
-60  
-70  
-80  
-60  
-70  
-80  
FILTERLESS MODULATION  
-90  
-90  
FILTERLESS MODULATION  
-100  
-100  
10  
100  
1k  
10k  
100k  
10  
100  
1k  
10k  
100k  
1µs/div  
FREQUENCY (Hz)  
FREQUENCY (Hz)  
OUTPUT FREQUENCY SPECTRUM  
OUTPUT FREQUENCY SPECTRUM  
OUTPUT WAVEFORM (PWM MODE)  
0
0
MAX9768 toc25  
FFM MODE  
V = -60dBV  
IN  
V
= -60dBV  
f = 1kHz  
IN  
-20  
-20  
f = 1kHz  
R = 8Ω  
UNWEIGHTED  
R = 8Ω  
L
UNWEIGHTED  
L
-40  
-60  
-80  
-40  
-60  
-80  
5V/div  
-100  
-120  
-140  
-100  
-120  
-140  
5V/div  
0
5
10  
15  
20  
0
5
10  
15  
20  
1µs/div  
FREQUENCY (kHz)  
FREQUENCY (kHz)  
WIDEBAND OUTPUT SPECTRUM  
(FIXED-FREQUENCY MODULATION MODE)  
WIDEBAND OUTPUT SPECTRUM  
(FIXED-FREQUENCY MODULATION MODE)  
WIDEBAND OUTPUT SPECTRUM  
(SPREAD-SPECTRUM MODULATION MODE)  
0
-10  
-20  
-30  
0
-10  
-20  
-30  
0
-10  
-20  
-30  
RBW = 10kHz  
INPUT AC GROUNDED  
FILTERLESS MODULATION  
RBW = 10kHz  
INPUT AC GROUNDED  
PWM MODE  
RBW = 10kHz  
INPUT AC GROUNDED  
FILTERLESS MODULATION  
-40  
-50  
-60  
-70  
-80  
-40  
-50  
-60  
-70  
-80  
-40  
-50  
-60  
-70  
-80  
-90  
-90  
-90  
-100  
-100  
-100  
1
10  
100  
1000  
1
10  
100  
1000  
1
10  
100  
1000  
FREQUENCY (MHz)  
FREQUENCY (MHz)  
FREQUENCY (MHz)  
Maxim Integrated  
│ 9  
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Typical Operating Characteristics (continued)  
((PV  
= 12V, V  
= 3.3V, V  
= V  
= 0, V  
= 0; 0dB volume setting; all speaker load resistors connected between OUT+  
DD  
DD  
GND  
PGND  
MUTE  
and OUT-, R = 8Ω, unless otherwise noted. C  
= 2.2μF, C1 = C2 = 0.1μF, C = 0.47μF, R = 20kΩ, R = 30kΩ, spread-spectrum  
IN IN FB  
L
BIAS  
modulation mode.)  
TURN-ON/OFF RESPONSE  
(MAX9768)  
TURN-ON/OFF RESPONSE  
(MAX9768B)  
WIDEBAND OUTPUT SPECTRUM  
(SPREAD-SPECTRUM MODULATION MODE)  
MAX9768 toc32  
MAX9768 toc33  
0
RBW = 10kHz  
-10  
-20  
-30  
INPUT AC GROUNDED  
PWM MODE  
SHDN  
2V/div  
SHDN  
2V/div  
-40  
-50  
-60  
-70  
-80  
OUT  
500mA/div  
OUT  
500mA/div  
-90  
-100  
1
10  
100  
1000  
100ms/div  
40ms/div  
FREQUENCY (MHz)  
VOLUME CONTROL LEVEL  
SUPPLY CURRENT (PV  
)
DD  
vs. VOLUME CONTROL VOLTAGE  
vs. SUPPLY VOLTAGE  
20  
0
4.0  
R = ∞  
L
3.5  
3.0  
2.5  
-20  
-40  
-60  
PWM MODE  
2.0  
1.5  
-80  
-100  
-120  
FILTERLESS MODULATION  
1.0  
0.5  
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5  
4
6
8
10  
12  
14  
V
VOL  
(V)  
SUPPLY VOLTAGE (V)  
SUPPLY CURRENT (V  
vs. SUPPLY VOLTAGE  
)
DD  
SHUTDOWN CURRENT  
vs. SUPPLY VOLTAGE  
15  
13  
11  
0.50  
0.45  
0.40  
0.35  
SHUTDOWN CURRENT = I  
+ I  
PVDD DD  
V
DD  
= 3.3V  
PWM MODE  
9
7
5
FILTERLESS MODULATION  
0.30  
2.6  
2.8  
3.0  
3.2  
3.4  
3.6  
4
6
8
10  
12  
14  
SUPPLY VOLTAGE (V)  
SUPPLY VOLTAGE (V)  
Maxim Integrated  
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Pin Configuration  
TOP VIEW  
18  
17  
16  
15  
14  
13  
12  
SHDN 19  
MUTE  
SYNC  
11  
GND  
20  
PGND 21  
10 BIAS  
MAX9768  
22  
23  
24  
9
PGND  
GND  
ADDR2  
8
7
IN  
+
ADDR1  
FB  
1
2
3
4
5
6
TQFN  
(4mm x 4mm)  
Pin Description  
PIN  
1, 2  
NAME  
FUNCTION  
OUT+  
Positive Speaker Output  
3, 16  
PV  
Speaker Amplifier Power-Supply Input. Bypass with a 1µF capacitor to ground.  
DD  
Positive Speaker Output Boost Flying-Capacitor Connection. Connect a 0.1µF ceramic capacitor  
between BOOT+ and OUT+.  
4
BOOT+  
2
2
I C Serial-Clock Input and Modulation Scheme Select. In I C mode (ADDR1 and ADDR2 ≠ GND)  
2
5
SCLK  
acts as I C serial-clock input. Connect SCLK to V  
for classic PWM modulation, or connect  
DD  
SCLK to ground for filterless modulation.  
2
6
7
SDA/VOL  
FB  
I C Serial Data I/O and Analog Volume Control Input  
Feedback. Connect feedback resistor between FB and IN to set amplifier gain. See the Adjustable  
Gain section.  
8
IN  
Audio Input  
9, 11  
10  
GND  
BIAS  
Ground  
Common-Mode Bias Voltage. Bypass with a 2.2µF capacitor to GND.  
Frequency Select and External Clock Input.  
SYNC = GND: Fixed-frequency mode with f = 300kHz.  
S
12  
SYNC  
SYNC = Unconnected: Fixed-frequency mode with f = 360kHz.  
S
SYNC = V : Spread-spectrum mode with f = 300kHz ±7.5kHz.  
DD  
S
SYNC = Clocked: Fixed-frequency mode with f = external clock frequency.  
S
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Pin Configuration (continued)  
13  
14  
SYNCOUT  
Clock Signal Output  
V
Power-Supply Input. Bypass with a 1µF capacitor to GND.  
DD  
Negative Speaker Output Boost Flying-Capacitor Connection. Connect a 0.1µF ceramic capacitor  
between BOOTL- and OUTL-.  
15  
17, 18  
19  
BOOT-  
OUT-  
Negative Speaker Output  
Shutdown Input. Drive SHDN low to disable the audio amplifiers. Connect SHDN to V  
for normal  
DD  
SHDN  
operation  
Mute Input. Drive MUTE high to mute the speaker outputs. Connect Mute to GND for normal  
operation.  
20  
MUTE  
21, 22  
23  
PGND  
ADDR2  
ADDR1  
Power Ground  
2
Address Select Input 2. I C address option, also selects volume control mode.  
2
24  
Address Select Input 1. I C address option, also selects volume control mode.  
Exposed Pad. Connect the exposed thermal pad to GND, and use multiple vias to a solid copper  
area on the bottom of the PCB.  
—
EP  
Functional Diagram/Typical Application Circuit  
2.7V to 3.6V  
4.5V to 14V  
1µF  
1µF  
V
PV  
DD  
DD  
14  
3, 16  
R
30kΩ  
MAX9768  
F
FB  
IN  
7
8
4
BOOT+  
C
IN  
R
20kΩ  
IN  
C1  
0.1µF  
0.47µF  
1, 2  
OUT+  
OUT-  
VOLUME  
CONTROL  
17, 18  
15  
C2  
0.1µF  
BOOT-  
BIAS  
20  
MUTE  
MUTE  
SHDN 19  
10  
SHUTDOWN  
CONTROL  
BIAS  
SDA/VOL  
SCLK  
6
5
C
BIAS  
2.2µF  
2
I C  
V
DD  
24  
ADDR1  
ANALOG  
ADDR2 23  
CONTROL  
SYNCOUT  
13  
SYNC 12  
OSCILLATOR  
9, 11  
GND  
21, 22  
PGND  
(SHOWN IN ANALOG VOLUME CONTOL MODE, A = 23.5dB, f  
= 17Hz, SPREAD-SPECTRUM MODULATION MODE, FILTERLESS MODULATION MODE, MUTE OFF)  
-3dB  
V
Maxim Integrated  
│ 12  
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
spectrum placement of the switching fundamental is  
important, program the switching frequency so the har-  
monics do not fall within a sensitive frequency band  
(Table 1). Audio reproduction is not affected by changing  
the switching frequency.  
Detailed Description  
The MAX9768 10W, Class D audio power amplifier  
with spread-spectrum modulation provides a significant  
step forward in switch-mode amplifier technology. The  
MAX9768 offers Class AB performance with Class D effi-  
ciency and a minimal board space solution. This device  
features a wide supply voltage operation (4.5V to 14V),  
analog or digitally adjusted volume control, externally  
set input gain, shutdown mode, SYNC input and output,  
speaker mute, and industry-leading click-and-pop sup-  
pression.  
Spread-Spectrum Mode  
The MAX9768 features a unique spread-spectrum mode  
that flattens the wideband spectral components, improv-  
ing EMI emissions that may be radiated by the speaker  
and cables. This mode is enabled by setting SYNC =  
V
(Table 1). In SSM mode, the switching frequency  
DD  
The MAX9768 features a 64-step, dual-mode (analog  
or I C programmed) volume control and mute function.  
In analog volume control mode, voltage applied to SDA/  
VOL sets the volume level. Two address inputs (ADDR1,  
ADDR2) set the volume control function between analog  
varies randomly by ±7.5kHz around the center frequency  
(300kHz). The modulation scheme remains the same, but  
the period of the triangle waveform changes from cycle to  
cycle. Instead of a large amount of spectral energy pres-  
ent at multiples of the switching frequency, the energy is  
now spread over a bandwidth that increases with frequen-  
2
2
2
and I C and set the slave address. In I C mode there  
are three selectable slave addresses allowing for multiple  
devices on a single bus.  
Spread-spectrum modulation and synchronizable switch-  
ing frequency significantly reduce EMI emissions. The  
outputs use Maxim’s low-EMI modulation scheme with  
minimum pulse outputs when the audio inputs are at the  
zero crossing. As the input voltage increases or decreases,  
the duration of the pulse at one output increases while the  
other output pulse duration remains the same. This causes  
OUT+  
MAX9768  
OUT-  
SYNCOUT  
the net voltage across the speaker (V  
- V ) to  
OUT-  
OUT+  
change. The minimum-width pulse topology reduces EMI  
and increases efficiency.  
Operating Modes  
Fixed-Frequency Mode  
MAX9768  
The MAX9768 features two fixed-frequency modes:  
300kHz and 360kHz. Connect SYNC to GND to select  
300kHz switching frequency; leave SYNC unconnected  
to select 360kHz switching frequency. The frequency  
spectrum of the MAX9768 consists of the fundamental  
switching frequency and its associated harmonics (see  
the Wideband Output Spectrum graphs in the Typical  
Operating Characteristics). For applications where exact  
OUT+  
SYNC  
OUT-  
Figure 1. Cascading Two Amplifiers  
Table 1. Operating Modes  
SYNC  
OSCILLATOR FREQUENCY (kHZ)  
CLASS D FREQUENCY (kHZ)  
GND  
Fixed-frequency modulation with f  
= 1200  
= 1440  
Fixed-frequency modulation with f  
Fixed-frequency modulation with f  
= 300  
= 360  
OSC  
OSC  
OSC  
OSC  
Unconnected Fixed-frequency modulation with f  
V
Spread-spectrum modulation with f  
= 1200 ±30  
Spread-spectrum modulation with f  
= 300 ±7.5  
OSC  
DD  
OSC  
Fixed-frequency modulation with f  
frequency  
= external clock  
Fixed-frequency modulation with f  
frequency/4  
= external clock  
OSC  
OSC  
Clocked  
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
cy. Above a few megahertz, the wideband spectrum looks  
like white noise for EMI purposes. A proprietary amplifier  
topology ensures this does not corrupt the noise floor in  
the audio bandwidth.  
Efficiency  
Efficiency of a Class D amplifier is due to the switching  
operation of the output stage transistors. In a Class D  
amplifier, the output transistors act as current-steering  
switches and consume negligible additional power. Any  
power loss associated with the Class D output stage is  
External Clock Mode  
The SYNC input allows the MAX9768 to be synchronized  
to an external clock, or another Maxim Class D ampli-  
fier, creating a fully synchronous system, minimizing clock  
intermodulation, and allocating spectral components of  
the switching harmonics to insensitive frequency bands.  
Applying a clock signal between 1MHz and 1.6MHz to  
SYNC synchronizes the MAX9768. The Class D switching  
frequency is equal to one-fourth the SYNC input frequency.  
2
mostly due to the I R loss of the MOSFET on-resistance,  
and quiescent-current overhead.  
The theoretical best efficiency of a linear amplifier is 78%,  
however, that efficiency is only exhibited at peak output  
power. Under normal operating levels (typical music  
reproduction levels), efficiency falls below 30%, whereas  
the MAX9768 still exhibits > 80% efficiencies under the  
same conditions (Figure 2).  
SYNCOUT is equal to the SYNC input frequency and  
allows several Maxim amplifiers to be cascaded. The  
synchronized output minimizes interference due to clock  
intermodulation caused by the switching spread between  
single devices. The modulation scheme remains the same  
when using SYNCOUT, and audio reproduction is not  
affected (Figure 1). Current flowing between SYNCOUT  
of a master device and SYNC of a slave device is low as  
the SYNC input is high impedance (typically 200kΩ).  
Soft Current Limit  
When the output current exceeds the soft current limit, 2A  
(typ), the MAX9768 enters a cycle-by-cycle current-limit  
mode. In soft current-limit mode, the output is clipped at  
2A. When the output decreases so the output current  
falls below 2A, normal operation resumes. The effect of  
soft current limiting is a slight increase in distortion. Most  
Filterless Modulation/PWM Modulation  
The MAX9768 features two output modulation schemes:  
filterless modulation or classic PWM, selectable through  
SCLK when the device is in analog mode (ADDR2 and  
EFFICIENCY vs. OUTPUT POWER  
100  
2
ADDR1 = GND, Table 2) or through the I C interface  
MAX9768  
90  
(Table 7). Maxim’s unique, filterless modulation scheme  
eliminates the LC filter required by traditional Class D  
amplifiers, reducing component count, conserving board  
space and system cost. Although the MAX9768 meets  
FCC and other EMI limits with a low-cost ferrite bead filter,  
many applications still may want to use a full LC-filtered  
output. If using a full LC filter, the performance is best with  
the MAX9768 configured for classic PWM output.  
80  
70  
60  
CLASS AB  
50  
40  
30  
20  
10  
0
PV = 12V  
DD  
Switching between schemes while in normal operating  
f = 1kHz  
IN  
R = 8Ω  
L
2
mode with the I C interface, the output is not click-and-  
pop protected. To have click-and-pop protection when  
switching between output schemes, the device must enter  
shutdown mode and be configured to the new output  
scheme before the startup sequence is terminated.  
0
2
4
6
8
10  
OUTPUT POWER (W)  
The startup time for the MAX9768 is typically 220ms. The  
startup time for the MAX9768B is typically 15ms.  
Figure 2. MAX9768 Efficiency vs. Class AB Efficiency  
Table 2. Modulation Scheme Selection In Analog Mode  
ADDR2  
ADDR1  
SDA/VOL  
SCLK  
FUNCTION  
0
0
0
0
Analog Volume Control  
Analog Volume Control  
0
1
Filterless Modulation  
Classic PWM (50% Duty Cycle)  
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
applications will not enter soft current-limit mode unless  
the speaker or filter creates impedance nulls below 8Ω.  
Volume Control  
The volume control operates from either an analog volt-  
age input or through the I C interface. The volume control  
has 64 levels, with the lowest setting equal to mute.  
2
Hard Current Limit  
When the output current exceeds the hard current limit,  
2.5A (typ), the MAX9768 disables the outputs and initiates  
a startup sequence. This startup sequence takes 220ms  
for the MAX9768 and 15ms for the MAX9768B. The shut-  
down and startup sequence is repeated until the output  
fault is removed. When in hard current limit, the output may  
make a soft clicking sound. The average supply current is  
relatively low, as the duty cycle of the output short is brief.  
Most applications will not enter hard current-limit mode  
unless the output is short circuited or incorrectly connected.  
To set the device to analog mode, connect ADDR1 and  
ADDR2 to GND. In analog mode, SDA/VOL is an analog  
input for volume control, see the Functional Diagram/  
Typical Application Circuit. The analog input range is  
ratiometric between 0.9 x V  
and 0.1 x V , where 0.9  
DD  
DD  
x V  
= full mute and 0.1 x V  
= full volume (Table 6).  
DD  
2
DD  
In I C mode, volume control for the speaker is controlled  
separately by the command register (see Table 4, Table  
5, and Table 6). See the Write Data Format section for  
more information regarding formatting data and tables to  
set volume levels.  
Thermal Shutdown  
When the die temperature exceeds the thermal shutdown  
threshold, +150°C (typ), the MAX9768 outputs are dis-  
abled. When the die temperature decreases below +135°C  
(typ), normal operation resumes. The effect of thermal shut-  
down is an output signal turning off for approximately 3s in  
most applications, depending on the thermal time constant  
of the audio system. Most applications should never enter  
thermal shutdown. Some of the possible causes of thermal  
shutdown are too low of a load impedance, high ambient  
temperature, poor PCB layout and assembly, or excessive  
output overdrive.  
2
I C Interface  
2
The MAX9768 features an I C 2-wire serial interface con-  
sisting of a serial data line (SDA) and a serial clock line  
(SCL). SDA and SCL facilitate communication between  
the MAX9768 and the master at clock rates up to 400kHz.  
2
When the MAX9768 is used on an I C bus with multiple  
devices, the V  
2
supply must stay powered on to ensure  
DD  
proper I C bus operation. The master, typically a micro-  
controller, generates SCL and initiates data transfer on the  
bus. Figure 3 shows the 2-wire interface timing diagram.  
A master device communicates to the MAX9768 by trans-  
mitting the proper address followed by the data word.  
Each transmit sequence is framed by a START (S) or  
Shutdown  
The MAX9768 features a shutdown mode that reduces  
power consumption and extends battery life. Driving SHDN  
low places the device in low-power (0.5μA) shutdown  
mode. Connect SHDN to digital high for normal opera-  
tion. In shutdown mode, the outputs are high impedance,  
SYNCOUT is pulled high, the BIAS voltage decays to zero,  
and the common-mode input voltage decays to zero. The  
REPEATED START (S ) condition and a STOP (P) condi-  
r
tion. Each word transmitted over the bus is 8 bits long and  
is always followed by an acknowledge clock pulse.  
The MAX9768 SDA line operates as both an input and an  
open-drain output. A pullup resistor, greater than 500Ω, is  
required on the SDA bus. The MAX9768 SCL line oper-  
ates as an input only. A pullup resistor, greater than 500Ω,  
is required on SCL if there are multiple masters on the  
bus, or if the master in a single-master system has an  
open-drain SCL output. Series resistors in line with SDA  
and SCL are optional. The SCL and SDA inputs suppress  
noise spikes to assure proper device operation even on  
a noisy bus.  
2
I C register does not retain its contents during shutdown.  
Undervoltage Lockout (UVLO)  
The MAX9768 features an undervoltage lockout protection  
that shuts down the device if either of the supplies are too  
low. The device will go into shutdown if V  
is less than  
is less than 4V (PV  
DD DD  
DD  
2.5V (V  
UVLO = 2.5V) or if PV  
DD  
UVLO = 4V).  
Mute Function  
Bit Transfer  
The MAX9768 features a clickless/popless mute mode.  
When the device is muted, the outputs do not stop  
switching, only the volume level is muted to the speaker.  
To mute the MAX9768, drive MUTE to logic-high. MUTE  
should be held high during system power-up and power-  
down to ensure optimum click-and-pop performance.  
One data bit is transferred during each SCL cycle. The data  
on SDA must remain stable during the high period of the  
SCL pulse. Changes in SDA while SCL is high are control  
signals (see the START and STOP Conditions section).  
2
SDA and SCL idle high when the I C bus is not busy.  
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
SDA  
SCL  
t
BUF  
t
t
SU,STA  
SU,DAT  
t
t
SP  
HD,STA  
t
SU,STO  
t
t
HD,DAT  
LOW  
t
HIGH  
t
HD,STA  
t
t
F
R
START  
CONDITION  
REPEATED  
START  
STOP  
START  
CONDITION CONDITION  
CONDITION  
Figure 3. 2-Wire Serial-Interface Timing Diagram  
(10010). The second is a 2-bit field, which is set through  
ADDR2 and ADDR1 (externally connected as logic-high  
or low). Third field is a R/W flag bit. Set R/W = 0 to write to  
the slave. A representation of the slave address is shown  
in Table 3.  
START and STOP Conditions  
A master device initiates communication by issuing a  
START condition. A START condition is a high-to-low  
transition on SDA with SCL high. A STOP condition  
is a low-to-high transition on SDA while SCL is high  
(Figure 4). A START (S) condition from the master signals  
the beginning of a transmission to the MAX9768. The  
master terminates transmission, and frees the bus, by  
issuing a STOP (P) condition. The bus remains active if a  
REPEATED START (Sr) condition is generated instead of  
a STOP condition.  
When ADDR1 and ADDR2 are connected to GND, serial  
interface communication is disabled. Table 4 summarizes  
the slave address of the device as a function of ADDR1  
and ADDR2.  
Acknowledge  
The acknowledge bit (ACK) is a clocked 9th bit that the  
MAX9768 uses to handshake receipt each byte of data  
(Figure 5). The MAX9768 pulls down SDA during the mas-  
ter-generated 9th clock pulse. The SDA line must remain  
stable and low during the high period of the acknowledge  
clock pulse. Monitoring ACK allows for detection of unsuc-  
cessful data transfers. An unsuccessful data transfer  
occurs if a receiving device is busy or if a system fault has  
occurred. In the event of an unsuccessful data transfer, the  
bus master can reattempt communication.  
Early STOP Conditions  
The MAX9768 recognizes a STOP condition at any point  
during data transmission except if the STOP condition  
occurs in the same high pulse as a START condition.  
Slave Address  
The slave address of the MAX9768 is 8 bits and consist-  
S
Sr  
P
Write Data Format  
SCL  
SDA  
A write to the MAX9768 includes transmission of a START  
condition, the slave address with the R/W bit set to 0 (see  
Table 3), one byte of data to the command register, and  
a STOP condition. Figure 6 illustrates the proper format  
for one frame.  
Figure 4. START, STOP, and REPEATED START Conditions  
ing of 3 fields: the first field is 5 bits wide and is fixed  
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Table 3. Slave Address Block  
SA7 (MSB)  
SA6  
SA5  
SA4  
SA3  
SA2  
SA1  
SA0 (LSB)  
1
0
0
1
0
ADDR2  
ADDR1  
R/W  
Table 4. Slave Address  
Table 5. Data Byte Format  
ADDR2  
ADDR1  
SLAVE ADDRESS  
Disabled  
D7  
(MSB)  
D0  
D1  
D6  
D5  
D4  
D3  
D2  
(LSB)  
0
0
1
1
0
1
0
1
0
0
V5  
V4  
V3  
V2  
V1  
V0  
1001001_  
1001010_  
1001011_  
CLOCK PULSE FOR  
ACKNOWLEDGMENT  
START  
CONDITION  
Volume Control  
The command register is used to control the volume  
level of the speaker amplifier. The two MSBs (D7 and  
D6) should be set to 00 to choose the speaker register.  
V5–V0 is the volume control data that will be written into  
the addresses register to set the volume level (see Table  
5 and Table 6).  
SCL  
1
2
8
9
NOT ACKNOWLEDGE  
SDA  
ACKNOWLEDGE  
For a write byte operation, the master sends a single byte  
to the slave device (MAX9768). This is done as follows:  
Figure 5. Acknowledge  
1) The master sends a start condition.  
2) The master sends the 7-bit slave ID plus a write bit  
(low).  
WRITE BYTE FORMAT  
3) The addressed slave asserts an ACK on the data  
line.  
S
SLAVE ADDRESS  
WR ACK  
DATA  
8 bits  
ACK  
P
4) The master sends 8 data bits.  
7 bits  
0
5) The active slave asserts an ACK (or NACK) on the  
data line.  
SLAVE ADDRESS:  
DATA BYTE: GIVES A COMMAND.  
EQUIVALENT TO CHIP-  
SELECT LINE OF A 3-  
WIRE INTERFACE.  
6) The master generates a stop condition.  
Applications Information  
Figure 6. Write Data Format Example  
Filterless Class D Operation  
The MAX9768 can be operated without a filter and meet  
common EMC radiation limits when the speaker leads are  
less than approximately 10cm. Lengths beyond 10cm are  
possible but should be verified against the appropriate  
EMC standard. Select the filter-less modulation mode with  
spread-spectrum modulation mode for best performance.  
For longer speaker wire lengths, a simple ferrite bead and  
capacitor-based filter can be used to meet EMC limits.  
See Figure 7 for the correct connections of these com-  
ponents. Select a ferrite bead with 100Ω to 600Ω imped-  
ance, and rated for at least 1.5A. The capacitor value  
will vary based on the ferrite bead chosen and the actual  
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Table 6. Speaker Volume Levels  
VOLUME  
POSITION  
VOLUME  
LEVEL (dB)  
STEP SIZE  
(dB)  
V5  
V4  
V3  
V2  
V1  
V0  
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
63  
62  
61  
60  
59  
58  
57  
56  
55  
54  
53  
52  
51  
50  
49  
48  
47  
46  
45  
44  
43  
42  
41  
40*  
39  
38  
37  
36  
35  
34  
33  
32  
9.5  
8.8  
0.7  
0.7  
0.6  
0.6  
0.6  
0.5  
0.5  
0.5  
0.5  
0.5  
0.6  
0.4  
0.5  
0.4  
0.4  
0.4  
0.7  
1.0  
1.5  
1.5  
1.5  
1.1  
1.1  
1.8  
1.0  
1.0  
1.1  
1.2  
1.3  
0.9  
1.0  
1.1  
1
1
8.2  
1
7.6  
1
7.0  
1
6.5  
1
5.9  
1
5.4  
1
4.9  
1
4.4  
1
3.9  
1
3.4  
1
2.9  
1
2.4  
1
2.0  
1
1.6  
1
1.2  
1
0.5  
1
-0.5  
-1.9  
-3.4  
-5.0  
-6.0  
-7.1  
-8.9  
-9.9  
-10.9  
-12.0  
-13.1  
-14.4  
-15.4  
-16.4  
1
1
1
1
1
1
1
1
1
1
1
1
1
*Default.  
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Table 6. Speaker Volume Levels (continued)  
VOLUME  
POSITION  
VOLUME  
LEVEL (dB)  
STEP SIZE  
(dB)  
V5  
V4  
V3  
V2  
V1  
V0  
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
31  
30  
29  
28  
27  
26  
25  
24  
23  
22  
21  
20  
19  
18  
17  
16  
15  
14  
13  
12  
11  
10  
9
-17.5  
-19.7  
-21.6  
-23.5  
-25.2  
-27.2  
-29.8  
-31.5  
-33.4  
-36.0  
-37.6  
-39.6  
-42.1  
-43.7  
-45.6  
-48.1  
-50.6  
-54.2  
-56.7  
-60.2  
-62.7  
-66.2  
-68.7  
-72.2  
-74.7  
-78.3  
-80.8  
-84.3  
-86.8  
-90.3  
-92.8  
-161.5  
2.2  
1.9  
1.9  
1.7  
2.0  
2.6  
1.6  
2.0  
2.5  
1.6  
2.0  
2.5  
1.6  
2.0  
2.5  
2.5  
3.5  
2.5  
3.5  
2.5  
3.5  
2.5  
3.5  
2.5  
3.5  
2.5  
3.5  
2.5  
3.5  
2.5  
—
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
8
0
7
0
6
0
5
0
4
0
3
0
2
0
0
1
0 (MUTE)  
—
*Default.  
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
speaker lead length. Select the capacitor value based on  
EMC performance.  
ing to compensate for the rising impedance of the loud-  
speaker. Without a Zobel, the filter will have a peak in its  
response near the cutoff frequency. Capacitors C11 and  
C12 provide additional high-frequency bypass to reduce  
radiated emissions.  
When doing bench evaluation without a filter or a ferrite  
bead filter, include a series inductor (68μH for 8Ω load) to  
model the actual loudspeaker’s behavior. If this inductance  
is omitted, the MAX9768 will have reduced efficiency and  
output power, as well as worse THD+N performance.  
Adjustable Gain  
Gain-Setting Resistors  
Inductor-Based Output Filters  
External feedback resistors set the gain of the MAX9768.  
The output stage has an internal 20dB gain in addition to  
the externally set gain. Set the maximum gain by using  
Some applications will use the MAX9768 with a full induc-  
tor-/capacitor-based (LC) output filter. This is common  
for longer speaker lead lengths, and to gain increased  
margin to EMC limits. Select the PWM output mode and  
use fixed-frequency modulation mode for best audio  
performance. See Figure 8 for the correct connections of  
these components.  
resistors R and R (Figure 9) as follows:  
F
IN  
R
R
F
A
= −10  
V / V  
V
IN  
Choose R between 10kΩ and 50kΩ. Please note that the  
F
The component selection is based on the load impedance  
of the speaker. Table 8 lists suggested values for a variety  
of load impedances.  
actual gain of the amplifier is dependent on the volume  
level setting. For example, with the volume control set to  
+9.5dB, the amplifier gain would be 9.5dB + 20dB, assum-  
Inductors L3 and L4, and capacitor C15 form the primary  
output filter. In addition to these primary filter components,  
other components in the filter improve its functionality.  
Capacitors C13 and C14, plus resistors R6 and R7, form  
a Zobel at the output. A Zobel corrects the output load-  
ing R = R .  
F
IN  
The input amplifier can be configured into a variety of  
circuits. The FB terminal is an actual operational ampli-  
fier output, allowing the MAX9768 to be configured as a  
summing amplifier, a filter, or an equalizer, for example.  
Table 7. Setting Class D Output Modulation Scheme  
D7 (MSB)  
D6  
1
D5  
0
D4  
1
D3  
0
D2  
1
D1  
0
D0 (LSB)  
FUNCTION  
1
1
Classic PWM  
FILTERLESS MODULATION*  
1
1
0
1
0
1
1
0
*Power-on default.  
BOOT_+  
OUT_+  
C1  
0.1µF  
MAX9768  
C9  
330pF  
OUT_-  
C10  
330pF  
C2  
0.1µF  
BOOT_-  
Figure 7. Ferrite Bead Filter  
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Choose C so f  
is well below the lowest frequency of  
Power Supplies  
IN  
-3dB  
interest. Use capacitors whose dielectrics have lowvoltage  
coefficients, such as tantalum or aluminum electrolytic.  
Capacitors with high-voltage coefficients, such as ceram-  
ics, may result in increased distortion at low frequencies.  
The MAX9768 has different supplies for each portion of  
the device, allowing for the optimum combination of head-  
room power dissipation and noise immunity. The speaker  
amplifiers are powered from PV  
and can range from  
DD  
4.5V to 14V. The remainder of the device is powered by  
. Power supplies are independent of each other so  
sequencing is not necessary. Power may be supplied by  
separate sources or derived from a single higher source  
using a linear regulator to reduce the voltage, as shown  
in Figure 10.  
Other considerations when designing the input filter  
include the constraints of the overall system and the  
actual frequency band of interest. Although high-fidelity  
audio calls for a flat-gain response between 20Hz and  
20kHz, portable voice-reproduction devices such as cellu-  
lar phones and two-way radios need only concentrate on  
the frequency range of the spoken human voice (typically  
300Hz to 3.5kHz). In addition, speakers used in portable  
devices typically have a poor response below 300Hz.  
Taking these two factors into consideration, the input  
filter may not need to be designed for a 20Hz to 20kHz  
response, saving both board space and cost due to the  
use of smaller capacitors.  
V
DD  
Component Selection  
Input Filter  
An input capacitor, C , in conjunction with the input resis-  
IN  
tor of the MAX9768 forms a highpass filter that removes  
the DC bias from an incoming signal. The AC-coupling  
capacitor allows the amplifier to automatically bias the  
signal to an optimum DC level. Assuming zero source  
impedance, the -3dB point of the highpass filter is given by:  
BIAS Capacitor  
BIAS is the output of the internally generated DC bias  
voltage. The BIAS bypass capacitor, C  
, improves  
1
BIAS  
f
=
− 3dB  
PSRR and THD+N by reducing power supply and other  
noise sources at the common-mode bias node. Bypass  
BIAS with a 2.2μF capacitor to GND.  
2πR C  
IN IN  
BOOT_+  
OUT_+  
4
C1  
0.1µF  
L4  
L3  
1, 2  
MAX9768  
C11  
C12  
C13  
R6  
C15  
R
L
OUT_-  
14, 18  
15  
C2  
0.1µF  
C14  
R7  
BOOT_-  
Figure 8. Output Filter for PWM Mode  
Table 8. Suggested Values for LC filter  
R (Ω)  
L3, L4 (µH)  
C15 (µF)  
0.33  
C11, C12 (µF)  
0.01  
R6, R7 (Ω)  
C13, C14 (µF)  
0.68  
L
6
8
15  
22  
33  
7.5  
10  
15  
0.22  
0.01  
0.47  
12  
0.1  
0.01  
0.33  
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MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
12V  
BOOT+  
OUT+  
AUDIO  
INPUT  
C
IN  
R
IN  
IN  
PV  
DD  
MAX9768  
IN  
1µF  
1µF  
OUT  
3.3V  
SHDN  
V
DD  
MAX9768  
R
F
MAX1726  
FB  
OUT-  
GND  
BOOT-  
GND  
Figure 10. Using a Linear Regulator to Produce 3.3V from a  
12V Power Supply  
Figure 9. Setting Gain  
Bypass V  
and PV  
with a 1μF capacitor to PGND.  
Supply Bypassing, Layout, and Grounding  
DD  
DD  
Place the bypass capacitors as close to the MAX9768  
as possible. Place a bulk capacitor between PV  
PGND, if needed.  
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. Large traces also aid in moving  
heat away from the package. Proper grounding improves  
audio performance, minimizes crosstalk between chan-  
nels, and prevents any switching noise from coupling into  
the audio signal. Connect PGND and GND together at a  
single point on the PCB. Route all traces that carry switch-  
ing transients away from GND and the traces/components  
in the audio signal path.  
and  
DD  
Use large, low-resistance output traces. Current drawn  
from the outputs increase as load impedance decreases.  
High output trace resistance decreases the power deliv-  
ered to the load. Large output, supply, and GND traces  
allow more heat to move from the MAX9768 to the air,  
decreasing the thermal impedance of the circuit if possible.  
Ordering Information  
Package Information  
For the latest package outline information and land patterns (foot-  
prints), go to www.maximintegrated.com/packages. Note that  
a “+”, “#”, or “-” in the package code indicates RoHS status only.  
Package drawings may show a different suffix character, but the  
drawing pertains to the package regardless of RoHS status.  
PART  
PIN-PACKAGE  
24 TQFN-EP*  
24 TQFN-EP*  
24 TQFN-EP*  
t
(ms)  
ON  
MAX9768ETG+  
MAX9768BETG+  
MAX9768BETG/V+  
220  
15  
15  
PACKAGE  
TYPE  
PACKAGE  
CODE  
DOCUMENT  
NO.  
Note: All devices are specified over the -40°C to +85°C  
operating temperature range.  
24 TQFN-EP  
T2444+4  
21-0139  
+Denotes a lead(Pb)-free/RoHS-compliant package.  
/V Denotes an automotive-qualified part,  
*EP = Exposed pad.  
Chip Information  
PROCESS: BiCMOS  
Maxim Integrated  
│ 22  
www.maximintegrated.com  
MAX9768  
10W Mono Class D Speaker  
Amplifier with Volume Control  
Revision History  
REVISION  
NUMBER  
REVISION  
DATE  
PAGES  
CHANGED  
DESCRIPTION  
0
1
2
9/07  
3/08  
Initial release  
—
Updated package outline  
Corrected various items  
24, 25  
11/08  
2, 4, 5, 11  
Converted data sheet to new template; updated globals in Electrical  
Characteristics and Typical Operating Characteristics, and added new variant  
(MAX9768BETG/V+) to Ordering Information  
3
12/17  
1‒25  
4
5
7/19  
Updated Table 6  
18, 19  
15  
11/20  
Updated Shutdown section  
For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.  
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses  
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)  
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.  
©
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.  
2020 Maxim Integrated Products, Inc.  
│ 23  

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