MAX9775_V01 [MAXIM]
2 x 1.5W, Stereo Class D Audio Subsystem with DirectDrive Headphone Amplifier;
| 型号： | MAX9775_V01 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 2 x 1.5W, Stereo Class D Audio Subsystem with DirectDrive Headphone Amplifier |
| 文件： | 总38页 (文件大小：658K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0746; Rev 4; 8/08
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
General Description
Features
♦ Unique Spread-Spectrum Modulation and Active
The MAX9775/MAX9776 combine a high-efficiency
Class D, stereo/mono audio power amplifier with a
mono DirectDrive® receiver amplifier and a stereo
DirectDrive headphone amplifier.
Emissions Limiting Significantly Reduces EMI
♦ 3D Stereo Enhancement (MAX9775 Only)
♦ Up to 3 Stereo Inputs
Maxim’s 3rd-generation, ultra-low-EMI, Class D audio
power amplifiers provide Class AB performance with
Class D efficiency. The MAX9775/MAX9776 deliver
1.5W per channel into a 4Ω load from a 5V supply and
offer efficiencies up to 79%. Active emissions limiting
circuitry and spread-spectrum modulation greatly
reduce EMI, eliminating the need for output filtering
found in traditional Class D devices.
♦ 1.5W Stereo Speaker Output (4Ω, V
= 5V)
DD
♦ 50mW Mono Receiver/Stereo Headphone Outputs
(32Ω, V = 3.3V)
DD
♦ High PSRR (68dB at 217Hz)
♦ 79% Efficiency (V
= 3.3V, R = 8Ω, P
=
DD
L
OUT
470mW)
♦ I2C Control—Input Configuration, Volume Control,
Output Mode
The MAX9775/MAX9776 utilize a fully differential archi-
tecture, a full-bridged output, and comprehensive click-
and-pop suppression. A 3D stereo enhancement
function allows the MAX9775 to widen the stereo sound
field immersing the listener in a cleaner, richer sound
experience than typically found in portable applications.
The devices utilize a flexible, user-defined mixer archi-
tecture that includes an input mixer, volume control, and
output mixer. All control is done through I2C.
♦ Click-and-Pop Suppression
♦ Low Total Harmonic Distortion (0.03% at 1kHz)
♦ Current-Limit and Thermal Protection
♦ Available in Space-Saving, 36-Bump WLP (3mm x
3mm) and 32-Pin TQFN (5mm x 5mm) Packages
Ordering Information
CLASS D
AMPLIFIER
PART
PIN-PACKAGE
The mono receiver amplifier and stereo headphone
amplifier use Maxim’s DirectDrive architecture that pro-
duces a ground-referenced output from a single supply,
eliminating the need for large DC-blocking capacitors,
saving cost, space, and component height.
MAX9775EBX+T
MAX9776ETJ+
MAX9776EBX+T
36 WLP*
Stereo
Mono
Mono
32 TQFN-EP**
36 WLP*
The MAX9775 is available in a 36-bump WLP (3mm x
3mm) package. The MAX9776 is available in a 32-pin
TQFN (5mm x 5mm) or a 36-bump WLP (3mm x 3mm)
package. Both devices are specified over the extended
-40°C to +85°C temperature range.
Applications
Cell Phones
Note: All devices are specified over the -40°C to +85°C oper-
ating temperature range.
+Denotes a lead-free/RoHS-compliant package.
*Four center bumps depopulated.
**EP = Exposed pad.
Pin Configurations appear at end of data sheet.
DirectDrive is a registered trademark of Maxim Integrated
Products, Inc.
Portable Multimedia Players
Handheld Gaming Consoles
Simplified Block Diagrams
SINGLE SUPPLY 2.7V TO 5.5V
SINGLE SUPPLY 2.7V TO 5.5V
3D
SOUND
CONTROL
GAIN
CONTROL
GAIN
CONTROL
MIXER/
MUX
MIXER/
MUX
2
2
I C
I C
INTERFACE
INTERFACE
MAX9775
MAX9776
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
ABSOLUTE MAXIMUM RATINGS
DD
V
to GND..............................................................................6V
Duration of Short Circuit Between
PV
CPV
to PGND .........................................................................6V
OUT_+ and OUT_- ..................................................Continuous
Duration of HP_, OUT_ Short Circuit to
DD
to CPGND....................................................................6V
DD
CPV to CPGND.....................................................-6V to +0.3V
GND or PV ..........................................................Continuous
Continuous Power Dissipation (T = +70°C)
A
SS
DD
V
SS
to CPGND..........................................................-6V to +0.3V
C1N.......................................(CPV - 0.3V) to (CPGND + 0.3V)
36-Bump (3mm x 3mm) UCSP Multilayer Board
(derate 17.0mW/°C above +70°C)...........................1360.5mW
32-Pin (5mm x 5mm) TQFN Single-Layer Board
SS
C1P.......................................(CPGND - 0.3V) to (CPV
+ 0.3V)
+ 0.3V)
DD
HPL, HPR to GND...................(CPV - 0.3V) to (CPV
SS
DD
GND to PGND and CPGND................................................±0.3V
to PV and CPV ....................................................±0.3V
(derate 21.3mW/°C above +70°C)...........................1702.1mW
32-Pin TQFN Multilayer Board (derate 34.5mW/°C
above +70°C)...........................................................275±.6mW
Junction Temperature......................................................+150°C
Operating Temperature Range ...........................-40°C to +±5°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
V
DD
DD
DD
SDA, SCL to GND.....................................................-0.3V to +6V
All other pins to GND..................................-0.3V to (V + 0.3V)
DD
Continuous Current In/Out of PV , PGND, CPV , CPGND,
DD
DD
OUT__, HPR, and HPL..................................................±±00mA
Continuous Input Current CPV ......................................260mA
SS
Continuous Input Current (all other pins) .........................±20mA
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.
5/MAX976
ELECTRICAL CHARACTERISTICS
(V
= PV
= CPV
= 3.3V, V
= V
= V
= 0V, SHDN = V , I2C settings (INA gain = +20dB, INB gain = INC gain =
DD
DD
DD
GND
PGND
CPGND DD
0dB, volume setting = 0dB, mono path gain = 0dB, SHDN = 1, SSM = 1). Speaker load resistors (R
OUT_+ and OUT_-, headphone load resistors are terminated to GND, unless otherwise noted. C1 = C2 = C3 = 1µF. T = T
) are terminated between
LSP
to
A
MIN
T
MAX
, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
GENERAL
V
, P
PVDD
,
DD VDD
C
Supply Voltage Range
Inferred from PSRR test
2.7
5.5
V
Output mode 1, 6, 11 (Rx mode)
Output mode 4, 9, 14 (HP mode)
Output mode 2, 7, 12 (SP mode)
Output mode 3, ±, 13 (SP and HP mode)
Output mode 1, 6, 11 (Rx mode)
Output mode 4, 9, 14 (HP mode)
Output mode 2, 7, 12 (SP mode)
Output mode 3, ±, 13 (SP and HP mode)
Current in mute (low power)
6.3
±
10
12.6
15
Quiescent Current (Mono)
Quiescent Current (Stereo)
I
I
mA
mA
DD
DD
9.5
12.9
7
1±
9
16.5
20
Mute Current
I
4.7
0.1
10
10
mA
µA
MUTE
Hard shutdown
SHDN = GND
2
Shutdown Current
I
SHDN
See the I C Interface
section
Soft shutdown
±.5
30
2±
15
Time from shutdown or power-on to full
operation
Turn-On Time
t
ms
ON
B and C pair inputs, T = +25°C,
A
VOL = max
17.5
41.0
kΩ
Input Resistance
R
IN
A pair inputs, T = +25°C, +20dB
3.5
45
5.5
50
±.0
60
kΩ
dB
V
A
Common-Mode Rejection Ratio
Input DC Bias Voltage
CMRR
T = +25°C, f = 1kHz (Note 2)
A IN
V
IN_ inputs
1.12
1.25
1.3±
BIAS
2
_______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
ELECTRICAL CHARACTERISTICS (continued)
(V
= PV
= CPV
= 3.3V, V
= V
= V
= 0V, SHDN = V , I2C settings (INA gain = +20dB, INB gain = INC gain =
DD
DD
DD
GND
PGND
CPGND DD
0dB, volume setting = 0dB, mono path gain = 0dB, SHDN = 1, SSM = 1). Speaker load resistors (R
) are terminated between
LSP
OUT_+ and OUT_-, headphone load resistors are terminated to GND, unless otherwise noted. C1 = C2 = C3 = 1µF. T = T
to
A
MIN
T
MAX
, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SPEAKER AMPLIFIERS
T
T
= +25°C
±5.5
±23.5
±40
A
Output Offset Voltage
V
mV
OS
≤ T ≤ T
MAX
MIN
A
Peak voltage,
T = +25°C,
A-weighted, 32
samples per second
(Notes 2, 3)
Into shutdown
-62
-60
A
Out of shutdown
Into mute
Click-and-Pop Level
K
CP
dB
-63
-62
70
Out of mute
V
= 2.7V to 5.5V
4±
DD
f = 217Hz,
100mV
6±
60
50
ripple
ripple
ripple
P-P
Power-Supply Rejection Ratio
(Note 3)
PSRR
T = +25°C
A
dB
f = 1kHz,
100mV
P-P
f = 20kHz,
100mV
P-P
R = 4Ω, V
= 5V
1500
450
L
DD
DD
DD
THD+N = 1%,
= +25°C
Output Power (Note 4)
Current Limit
P
R = ±Ω, V
L
= 3.3V
= 5V
mW
A
OUT
T
A
R = ±Ω, V
L
1115
1.6
R = ±Ω,
L
0.03
0.04
P
= 125mW
OUT
Total Harmonic Distortion Plus
Noise (Note 4)
THD+N
SNR
f = 1kHz
%
R = 4Ω,
L
P
= 250mW
OUT
V
= 1.±V
,
OUT
RMS
BW = 20Hz to 20kHz
A-weighted
±1
±4
Signal-to-Noise Ratio
Output Frequency
dB
R = ±Ω, 3D not
L
active (Note 3)
Fixed-frequency modulation
Spread-spectrum modulation
1100
f
kHz
OSC
1100 ±30
P
= 470mW, f = 1kHz both channels
OUT
Efficiency
Gain
η
79
12
±1
%
dB
%
driven, L = 6±µH in series with ±Ω load
A
V
Channel-to-Channel Gain
Tracking (Note 5)
T
= +25°C
A
Used with 22nF and 2.2nF external
capacitors
3D Sound Resistors (Note 5)
Crosstalk (Notes 4, 5)
R
5
7
9
kΩ
3D
L to R, R to L, f = 10kHz, R = ±Ω,
L
73
dB
V
= 300mV
OUT
RMS
_______________________________________________________________________________________
3
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
ELECTRICAL CHARACTERISTICS (continued)
(V
= PV
= CPV
= 3.3V, V
= V
= V
= 0V, SHDN = V , I2C settings (INA gain = +20dB, INB gain = INC gain =
DD
DD
DD
GND
PGND
CPGND DD
0dB, volume setting = 0dB, mono path gain = 0dB, SHDN = 1, SSM = 1). Speaker load resistors (R
) are terminated between
LSP
OUT_+ and OUT_-, headphone load resistors are terminated to GND, unless otherwise noted. C1 = C2 = C3 = 1µF. T = T
to
A
MIN
T
MAX
, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
RECEIVER AMPLIFIER
Output Offset Voltage
V
T
= +25°C
A
±1.±
-62
-67
-63
-66
±0
±5.5
mV
OS
Into shutdown
Peak voltage, T
+25°C, A-weighted,
32 samples per
=
A
Into mute
Click-and-Pop Level
K
dB
dB
CP
Out of shutdown
Out of mute
second (Notes 3, 6)
V
= 2.7V to 5.5V
5±
DD
f = 217Hz,
100mV
±0
70
62
ripple
ripple
ripple
P-P
Power-Supply Rejection Ratio
(Note 3)
PSRR
T
T
= +25°C
= +25°C,
f = 1kHz,
100mV
A
A
5/MAX976
P-P
f = 20kHz,
100mV
P-P
R = 16Ω
L
60
50
Output Power
Gain
P
mW
dB
%
OUT
THD+N = 1%
R = 32Ω
L
A
3
V
R = 16Ω (V
= ±00mV
= ±00mV
, f = 1kHz)
, f = 1kHz)
0.03
0.024
±7
L
OUT
RMS
Total Harmonic Distortion Plus
Noise
THD+N
R = 32Ω (V
L
OUT
RMS
BW = 20Hz to 20kHz
A-weighted
R = 16Ω, V
±00mV
=
L
OUT
Signal-to-Noise Ratio
SNR
SR
dB
(Note 3)
RMS
±9
Slew Rate
0.3
300
V/µs
pF
Capacitive Drive
C
L
HEADPHONE AMPLIFIERS
Output Offset Voltage
V
T
= +25°C
A
±1.±
-61
-65
-60
-64
±4
±5.5
mV
dB
OS
Into shutdown
Into mute
Peak voltage, T
+25°C, A-weighted,
32 samples per
=
A
Click-and-Pop Level
ESD Protection
K
CP
Out of shutdown
Out of mute
Contact
second (Notes 2, 4)
HP_
kV
Air
±±
V
= 2.7V to 5.5V
5±
±0
DD
f = 217Hz,
100mV
±0
70
62
ripple
ripple
ripple
P-P
Power-Supply Rejection Ratio
(Note 3)
PSRR
T
= +25°C
dB
A
f = 1kHz,
100mV
P-P
f = 20kHz,
100mV
P-P
4
_______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
ELECTRICAL CHARACTERISTICS (continued)
(V
= PV
= CPV
= 3.3V, V
= V
= V
= 0V, SHDN = V , I2C settings (INA gain = +20dB, INB gain = INC gain =
DD
DD
DD
GND
PGND
CPGND DD
0dB, volume setting = 0dB, mono path gain = 0dB, SHDN = 1, SSM = 1). Speaker load resistors (R
) are terminated between
LSP
OUT_+ and OUT_-, headphone load resistors are terminated to GND, unless otherwise noted. C1 = C2 = C3 = 1µF. T = T
to
A
MIN
T
MAX
, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBOL
CONDITIONS
R = 16Ω
MIN
TYP
60
MAX
UNITS
L
T
= +25°C,
A
Output Power
P
mW
OUT
THD+N = 1%
R = 32Ω
L
50
Current Limit
Gain
170
+3
mA
dB
A
V
Channel-to-Channel Gain
Tracking
T
= +25°C
±1
%
%
A
R = 16Ω (V
= ±00mV
, f = 1kHz)
0.03
L
OUT
RMS
Total Harmonic Distortion Plus
Noise
THD+N
R = 32Ω (V
= ±00mV
, f = 1kHz)
0.024
L
OUT
RMS
BW = 20Hz to
20kHz
92
R = 16Ω,
L
Signal-to-Noise Ratio
SNR
SR
dB
V
= ±00mV
OUT
RMS
A-weighted
93
0.3
300
Slew Rate
V/µs
pF
Capacitive Drive
C
L
L to R, R to L, f = 10kHz, R = 16Ω,
L
Crosstalk
75
dB
V
= 160mV
OUT
RMS
VOLUME CONTROL
HP gain (max)
SP gain (max)
HP gain (min)
SP gain (min)
HP gain (max)
SP gain (max)
HP gain (min)
SP gain (min)
Mono+6dB = 0
3
IN+6dB = 0
(minimum gain
setting)
12
-72
-63
9
Volume Control
dB
dB
IN+6dB = 1
(maximum gain
setting)
1±
-61
-57
0
Mono Gain
All outputs
Mono+6dB = 1
6
INA+20dB = 0 (minimum gain setting)
INA+20dB = 1 (maximum gain setting)
Set by IN+6dB
20
Input Pair A Control
dB
dB
Mute Attenuation
(Minimum Volume)
V
= 1V
±0
IN
RMS
DIGITAL INPUTS (SHDN, SDA, SCL)
Input-Voltage High
V
1.4
V
V
IH
Input-Voltage Low
V
0.4
IL
Input Hysteresis (SDA, SCL)
V
200
mV
HYS
_______________________________________________________________________________________
5
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
ELECTRICAL CHARACTERISTICS (continued)
(V
= PV
= CPV
= 3.3V, V
= V
= V
= 0V, SHDN = V , I2C settings (INA gain = +20dB, INB gain = INC gain =
DD
DD
DD
GND
PGND
CPGND DD
0dB, volume setting = 0dB, mono path gain = 0dB, SHDN = 1, SSM = 1). Speaker load resistors (R
) are terminated between
LSP
OUT_+ and OUT_-, headphone load resistors are terminated to GND, unless otherwise noted. C1 = C2 = C3 = 1µF. T = T
to
A
MIN
T
MAX
, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
10
MAX
UNITS
pF
SDA, SCL Input Capacitance
Input Leakage Current
C
IN
IN
I
0.3
50
5.0
µA
Pulse Width of Spike Suppressed
DIGITAL OUTPUTS (SDA Open Drain)
t
SP
ns
Output Low Voltage SDA
V
I
= 6mA
SINK
0.4
V
OL
V
to V
bus capacitance =
L(MAX)
H(MIN)
Output Fall Time SDA
t
250
ns
OF
10pF to 400pF, I
= 3mA
SINK
2
I C INTERFACE TIMING (Note 7)
Serial Clock Frequency
f
DC
1.3
400
kHz
µs
SCL
Bus Free Time Between STOP
and START Conditions
5/MAX976
t
BUF
START Condition Hold
STOP Condition Setup Time
Clock Low Period
t
0.6
0.6
1.3
0.6
100
0
µs
µs
µs
µs
ns
ns
HD:STA
t
SU:STA
t
LOW
Clock High Period
Data Setup Time
t
HIGH
t
SU:DAT
HD:DAT
Data Hold Time
t
900
300
Maximum Receive SCL/SDA Rise
Time
t
ns
R
Maximum Receive SCL/SDA Fall
Time
t
300
ns
µs
pF
F
Setup Time for STOP Condition
t
0.6
SU:STO
Capacitive Load for Each Bus
Line
C
400
b
Note 1: All devices are 100% production tested at room temperature. All temperature limits are guaranteed by design.
Note 2: Measured at headphone outputs.
Note 3: Amplifier inputs AC-coupled to GND.
Note 4: Testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For R = ±Ω, L = 6±µH;
L
for R = 4Ω, L = 47µH.
L
Note 5: MAX9775 only.
Note 6: Testing performed at room temperature with an ±Ω resistive load in series with a 6±µH inductive load connected across BTL
outputs for speaker amplifier. Testing performed with a 32Ω resistive load connected between OUT_ and GND for head-
phone amplifier. Testing performed with 32Ω resistive load connected between OUTRx and GND for mono receiver amplifi-
2
er. Mode transitions are controlled by I C.
Note 7: Guaranteed by design.
6
_______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
Typical Operating Characteristics
(V
DD
= PV
= CPV
= 3.3V, GND = PGND = CPGND = 0V, SHDN = V , I2C default gain settings (INA gain = +20dB, INB gain =
DD DD
DD
INC gain = 0dB, volume setting = 0dB, mono path gain = 0dB, SHDN = 1, SSM = 1). Speaker load resistors (R
) are terminated
LSP
between OUT_+ and OUT_-, headphone load resistors are terminated to GND, unless otherwise stated. C1 = C2 = C3 = 1µF. T
+25°C, unless otherwise noted.)
=
A
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
1
1
1
V
DD
= 5V
V
DD
= 5V
V
DD
= 3.3V
R = 4Ω
L
R = 8Ω
L
R = 4Ω
L
P
= 400mW
P
OUT
= 150mW
OUT
P
OUT
= 400mW
0.1
0.1
0.1
P
= 150mW
OUT
P
= 1000mW
P
= 750mW
OUT
OUT
0.01
0.001
0.01
0.001
0.01
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
FREQUENCY (Hz)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
100
1
1
V
DD
= 5V
V
DD
= 3.3V
V
DD
= 3.3V
R = 4Ω
L
R = 8Ω
L
R = 8Ω
L
P
OUT
= 500mW
10
SSM
P
OUT
= 300mW
0.1
0.1
1
f = 10kHz
f = 1kHz
0.1
P
= 150mW
OUT
FFM
0.01
0.001
0.01
0.001
0.01
0.001
f = 20Hz
0
0.4
0.8
1.2
1.6
2.0
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
10k
100k
OUTPUT POWER (W)
FREQUENCY (Hz)
_______________________________________________________________________________________
7
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Typical Operating Characteristics (continued)
(V
DD
= PV
= CPV
= 3.3V, GND = PGND = CPGND = 0V, SHDN = V , I2C default gain settings (INA gain = +20dB, INB gain =
DD DD
DD
INC gain = 0dB, volume setting = 0dB, mono path gain = 0dB, SHDN = 1, SSM = 1). Speaker load resistors (R
) are terminated
LSP
between OUT_+ and OUT_-, headphone load resistors are terminated to GND, unless otherwise stated. C1 = C2 = C3 = 1µF. T
+25°C, unless otherwise noted.)
=
A
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
100
100
V
DD
= 3.3V
V
DD
= 5V
V
= 3.3V
DD
R = 4Ω
R = 8Ω
L
L
R = 8Ω
L
f = 1kHz
10
10
f = 1kHz
10
f = 1kHz
1
1
1
f = 10kHz
f = 10kHz
f = 10kHz
0.1
0.1
0.1
0.01
0.001
0.01
0.001
0.01
0.001
f = 20Hz
f = 20Hz
f = 20Hz
5/MAX976
0
0.2
0.4
0.6
0.8
0
0.3
0.6
0.9
1.2
1.5
0
0.2
0.4
0.6
OUTPUT POWER (W)
OUTPUT POWER (W)
OUTPUT POWER (W)
EFFICIENCY
vs. OUTPUT POWER
EFFICIENCY
vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
100
100
100
V
= 5V
DD
90
80
70
60
50
40
30
20
10
0
90
80
70
60
50
40
30
20
10
0
R = 8Ω
L
R = 8Ω
L
R = 8Ω
L
f = 1kHz
10
1
R = 4Ω
L
SSM
R = 4Ω
L
0.1
0.01
0.001
V
= 5V
= 1kHz
V
DD
= 3.3V
DD
FFM
f
f = 1kHz
IN
IN
P
OUT
= P
OUTL
+ P
OUTR
P
OUT
= P
+ P
OUTL OUTR
0
0.8
1.6
2.4
3.2
4.0
0
0.4
0.8
1.2
1.6
2.0
0
0.3
0.6
0.9
1.2
1.5
OUTPUT POWER (W)
OUTPUT POWER (W)
OUTPUT POWER (W)
8
_______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
Typical Operating Characteristics (continued)
(V
DD
= PV
= CPV
= 3.3V, GND = PGND = CPGND = 0V, SHDN = V , I2C default gain settings (INA gain = +20dB, INB gain =
DD DD
DD
INC gain = 0dB, volume setting = 0dB, mono path gain = 0dB, SHDN = 1, SSM = 1). Speaker load resistors (R
) are terminated
LSP
between OUT_+ and OUT_-, headphone load resistors are terminated to GND, unless otherwise stated. C1 = C2 = C3 = 1µF. T
+25°C, unless otherwise noted.)
=
A
OUTPUT POWER
vs. SUPPLY VOLTAGE
OUTPUT POWER
vs. SUPPLY VOLTAGE
OUTPUT POWER
vs. LOAD
1600
1400
1200
1000
800
600
400
200
0
2200
2000
1800
1600
1400
1200
1000
800
2.5
2.0
1.5
1.0
0.5
0
R = 8Ω
R = 4Ω
L
L
V
= 5V
DD
f = 1kHz
f = 1kHz
f = 1kHz
THD+N = 10%
THD+N = 10%
THD+N = 10%
THD+N = 1%
THD+N = 1%
THD+N = 1%
600
400
200
0
2.7
3.2
3.7
4.2
4.7
5.2
2.7
3.2
3.7
4.2
4.7
5.2
1
10
100
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
LOAD (Ω)
OUTPUT POWER
vs. LOAD
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
CROSSTALK vs. FREQUENCY
1000
800
600
400
200
0
0
0
-10
V
= 3.3V
V
= 3.3V
DD
DD
OUT_ = 1V
P-P
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
f = 1kHz
V
= 100mV
IN
P-P
R = 8Ω
L
-20
R = 8Ω
L
-30
THD+N = 10%
OUTR
OUTL
-40
RIGHT TO LEFT
-50
-60
-70
-80
THD+N = 1%
-90
LEFT TO RIGHT
-100
-110
-120
1
10
100
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
10k
100k
LOAD (Ω)
FREQUENCY (Hz)
_______________________________________________________________________________________
9
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Typical Operating Characteristics (continued)
(V
DD
= PV
= CPV
= 3.3V, GND = PGND = CPGND = 0V, SHDN = V , I2C default gain settings (INA gain = +20dB, INB gain =
DD DD
DD
INC gain = 0dB, volume setting = 0dB, mono path gain = 0dB, SHDN = 1, SSM = 1). Speaker load resistors (R
) are terminated
LSP
between OUT_+ and OUT_-, headphone load resistors are terminated to GND, unless otherwise stated. C1 = C2 = C3 = 1µF. T
+25°C, unless otherwise noted.)
=
A
IN-BAND OUTPUT SPECTRUM
IN-BAND OUTPUT SPECTRUM
CROSSTALK vs. INPUT AMPLITUDE
20
0
20
0
0
-10
SSM MODE
R = 8Ω
FFM MODE
R = 8Ω
f
= 1kHz
IN
L
R = 8Ω
GAIN = +12dB
L
V
L
V
-20
= 3.3V
= 3.3V
DD
DD
-20
-40
-60
-80
-100
-120
-140
-20
-40
-60
-80
-100
-120
-140
-30
f
= 1kHz
f = 1kHz
IN
IN
UNWEIGHTED
UNWEIGHTED
-40
RIGHT TO LEFT
-50
-60
-70
-80
-90
-100
-110
-120
7
LEFT TO RIGHT
0
5k
10k
15k
20k
0
5k
10k
15k
20k
0
0.1
0.2
0.3
0.4
0.5
0.6
FREQUENCY (Hz)
FREQUENCY (Hz)
INPUT AMPLITUDE (V
)
RMS
WIDEBAND OUTPUT SPECTRUM
FIXED-FREQUENCY MODE
WIDEBAND OUTPUT SPECTRUM
SPREAD-SPECTRUM MODE
MAX9775 SUPPLY CURRENT
vs. SUPPLY VOLTAGE
20
0
20
0
25
20
15
10
SP MODE
INPUTS AC GROUNDED
OUTPUTS UNLOADED
-20
-40
-60
-80
-100
-120
-140
-20
-40
-60
-80
-100
V
L
= 5V
DD
V
= 5V
DD
R = 8Ω
INPUTS AC GROUNDED
R = 8Ω
INPUTS AC GROUNDED
-120
-140
L
0.1
1
10
FREQUENCY (MHz)
100
1000
0.1
1
10
FREQUENCY (MHz)
100
1000
2.7
3.2
3.7
4.2
4.7
5.2
SUPPLY VOLTAGE (V)
10 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
Typical Operating Characteristics (continued)
(V
DD
= PV
= CPV
= 3.3V, GND = PGND = CPGND = 0V, SHDN = V , I2C default gain settings (INA gain = +20dB, INB gain =
DD DD
DD
INC gain = 0dB, volume setting = 0dB, mono path gain = 0dB, SHDN = 1, SSM = 1). Speaker load resistors (R
) are terminated
LSP
between OUT_+ and OUT_-, headphone load resistors are terminated to GND, unless otherwise stated. C1 = C2 = C3 = 1µF. T
+25°C, unless otherwise noted.)
=
A
MAX9776 SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
16
14
12
10
8
1
100
90
80
70
60
50
40
30
20
10
0
V
DD
= 5V
SP MODE
INPUTS AC GROUNDED
OUTPUTS UNLOADED
R = 32Ω
L
0.1
P
OUT
= 20mW
0.01
0.001
P
OUT
= 40mW
6
4
2.7
3.2
3.7
4.2
4.7
5.2
10
100
1k
10k
100k
2.7
3.2
3.7
4.2
4.7
5.2
SUPPLY VOLTAGE (V)
FREQUENCY (Hz)
SUPPLY VOLTAGE (V)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
1
1
100
10
V
DD
= 5V
V
= 3.3V
V
= 3.3V
DD
DD
R = 32Ω
L
R = 16Ω
L
R = 32Ω
L
f = 1kHz
0.1
0.1
P
= 40mW
OUT
1
P
OUT
= 40mW
f = 10kHz
0.1
0.01
0.001
0.01
0.001
P
= 20mW
OUT
0.01
0.001
P
OUT
= 10mW
f = 20Hz
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
10k
100k
0
20
40
60
80
FREQUENCY (Hz)
OUTPUT POWER (mW)
______________________________________________________________________________________ 11
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Typical Operating Characteristics (continued)
(V
DD
= PV
= CPV
= 3.3V, GND = PGND = CPGND = 0V, SHDN = V , I2C default gain settings (INA gain = +20dB, INB gain =
DD DD
DD
INC gain = 0dB, volume setting = 0dB, mono path gain = 0dB, SHDN = 1, SSM = 1). Speaker load resistors (R
) are terminated
LSP
between OUT_+ and OUT_-, headphone load resistors are terminated to GND, unless otherwise stated. C1 = C2 = C3 = 1µF. T
+25°C, unless otherwise noted.)
=
A
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. COMMON-MODE VOLTAGE
100
100
10
100
V
DD
= 3.3V
V = 3.3V
DD
V
= 3.3V
DD
R = 32Ω
L
f
= 1kHz
R = 16Ω
L
IN
P
= 30mW
10
OUT
10
GAIN = +3dB
f = 1kHz
R = 32Ω
L
f = 1kHz
1
1
1
f = 10kHz
f = 10kHz
0.1
0.1
0.1
0.01
0.001
0.01
0.001
0.01
0.001
5/MAX976
f = 20Hz
f = 20Hz
0
30
60
90
120
0
20
40
60
80
0
0.5
1.0
1.5
2.0
2.5
OUTPUT POWER (mW)
OUTPUT POWER (mW)
COMMON-MODE VOLTAGE (V)
POWER DISSIPATION
vs. OUTPUT POWER
POWER DISSIPATION
vs. OUTPUT POWER
OUTPUT POWER
vs. SUPPLY VOLTAGE
500
450
400
350
300
250
200
150
100
50
500
65
450
400
350
300
250
200
150
100
50
60
55
50
45
40
35
30
THD+N = 10%
THD+N = 1%
R = 16Ω
L
R = 32Ω
L
V
DD
= 5V
V
DD
= 3.3V
f = 1kHz
f = 1kHz
= P
R = 32Ω
L
R = 32Ω
L
P
+ P
OUTL
P
OUT
= P + P
OUTR OUTL
OUT
OUTR
f = 1kHz
0
0
0
40
80
120
160
0
40
80
120
2.7
3.2
3.7
4.2
4.7
5.2
TOTAL OUTPUT POWER (mW)
TOTAL OUTPUT POWER (mW)
SUPPLY VOLTAGE (V)
12 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
Typical Operating Characteristics (continued)
(V
DD
= PV
= CPV
= 3.3V, GND = PGND = CPGND = 0V, SHDN = V , I2C default gain settings (INA gain = +20dB, INB gain =
DD DD
DD
INC gain = 0dB, volume setting = 0dB, mono path gain = 0dB, SHDN = 1, SSM = 1). Speaker load resistors (R
) are terminated
LSP
between OUT_+ and OUT_-, headphone load resistors are terminated to GND, unless otherwise stated. C1 = C2 = C3 = 1µF. T
+25°C, unless otherwise noted.)
=
A
OUTPUT POWER
vs. LOAD
OUTPUT POWER
vs. LOAD
OUTPUT POWER vs. LOAD RESISTANCE
AND CHARGE-PUMP CAPACITOR SIZE
200
180
160
140
120
100
80
200
180
160
140
120
100
80
100
80
60
40
20
0
V
= 3.3V
V
DD
= 3.3V
DD
f = 1kHz
f = 1kHz
THD+N = 1%
C1 = C2 = 2.2μF
C1 = C2 = 1μF
THD+N = 10%
THD+N = 10%
60
60
40
40
V
= 5V
DD
20
20
THD+N = 1%
THD+N = 1%
f = 1kHz
C1 = C2 = 0.68μF
0
0
10
100
1000
10
100
1000
10
100
1000
LOAD (Ω)
LOAD (Ω)
LOAD (Ω)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
OUTPUT FREQUENCY SPECTRUM
CROSSTALK vs. FREQUENCY
20
0
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
0
-10
V
DD
= 3.3V
OUT_ = 1V
V
DD
= 3.3V
P-P
f = 1kHz
R = 32Ω
L
R = 32Ω
V
= 100mV
L
IN
P-P
-20
R = 32Ω
L
-20
-40
-60
-80
-100
-120
-140
-30
-40
-50
RIGHT TO LEFT
-60
-70
HPR
-80
-90
-100
-110
-120
LEFT TO RIGHT
HPL
10k
0
5k
10k
15k
20k
10
100
1k
FREQUENCY (Hz)
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
FREQUENCY (Hz)
______________________________________________________________________________________ 13
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Typical Operating Characteristics (continued)
(V
DD
= PV
= CPV
= 3.3V, GND = PGND = CPGND = 0V, SHDN = V , I2C default gain settings (INA gain = +20dB, INB gain =
DD DD
DD
INC gain = 0dB, volume setting = 0dB, mono path gain = 0dB, SHDN = 1, SSM = 1). Speaker load resistors (R
) are terminated
LSP
between OUT_+ and OUT_-, headphone load resistors are terminated to GND, unless otherwise stated. C1 = C2 = C3 = 1µF. T
+25°C, unless otherwise noted.)
=
A
TURN-OFF RESPONSE
TURN-ON RESPONSE
CROSSTALK vs. INPUT AMPLITUDE
MAX9775/76 toc45
MAX9775/76 toc44
0
-10
SCL
2V/div
SCL
2V/div
f
= 1kHz
IN
L
R = 32Ω
GAIN = +3dB
-20
-30
-40
-50
SPEAKER
OUTPUT
50mA/div
SPEAKER
OUTPUT
50mA/div
RIGHT TO LEFT
-60
-70
-80
HEADPHONE
OUTPUT
2V/div
-90
HEADPHONE
OUTPUT
2V/div
5/MAX976
-100
-110
-120
LEFT TO RIGHT
0
0.4
0.8
RMS
1.2
10ms/div
10ms/div
INPUT AMPLITUDE (V
)
MUTE-ON RESPONSE
MUTE-OFF RESPONSE
MAX9775/76 toc46
MAX9775/76 toc47
SCL
2V/div
SCL
2V/div
SPEAKER
OUTPUT
50mA/div
SPEAKER
OUTPUT
50mA/div
HEADPHONE
OUTPUT
2V/div
HEADPHONE
OUTPUT
2V/div
10ms/div
10ms/div
14 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
Pin Description—MAX9775
PIN
F1
NAME
PV
FUNCTION
Class D Power Supply
DD
E1
OUTL-
SCL
Negative Left-Speaker Output
D2
D1, F3
C1
C2
B1
B2
A1
A2
B3
A3
A4
B4
A5
A6
B5
B6
C5
C6
D6
D5
E6
Serial Clock Input. Connect a 1kΩ pullup resistor from SCL to V
.
DD
PGND
OUTL+
SDA
Power Ground
Positive Left-Speaker Output
Serial Data Input. Connect a 1kΩ pullup resistor from SDA to V
3D External Capacitor 3. Connect a 2.2nF capacitor to GND.
3D External Capacitor 4. Connect a 22nF capacitor to GND.
Charge-Pump Power Supply
.
DD
CL_L
CL_H
CPV
DD
C1P
Charge-Pump Flying Capacitor Positive Terminal
Common-Mode Bias
VBIAS
CPGND
C1N
Charge-Pump GND
Charge-Pump Flying Capacitor Negative Terminal
Input C1. Left input or positive input (see Table 5a).
INC1
CPV
Charge-Pump Output. Connect to V
.
SS
SS
HPL
Left Headphone Output
V
Headphone Amplifier Negative Power Supply. Connect to CPV
.
SS
SS
HPR
INC2
Right Headphone Output
Input C2. Right input or negative input (see Table 5a).
Mono Receiver Output
OUTRx
V
Analog Power Supply
DD
INB2
CR_L
INB1
Input B2. Right input or negative input (see Table 5a).
3D External Capacitor 1. Connect a 2.2nF capacitor to GND.
Input B1. Left input or positive input (see Table 5a).
Analog Ground
E5
F6
GND
F5
CR_H
INA2
3D External Capacitor 2. Connect a 22nF capacitor to GND.
Input A2. Right input or negative input (see Table 5a).
Positive Right Speaker Output
E4
F4
OUTR+
INA1
E3
Input A1. Left input or positive input (see Table 5a).
Negative Right Speaker Output
F2
OUTR-
SHDN
E2
Active-Low Hardware Shutdown
Exposed Pad. The external pad lowers the package’s thermal impedance by providing a
direct heat conduction path from the die to the PCB. The exposed pad is internally
connected to GND. Connect the exposed thermal pad to the GND plane.
—
EP
______________________________________________________________________________________ 15
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Pin Description—MAX9776
PIN
NAME
PV
FUNCTION
TQFN
UCSP
F1
1
Class D Power Supply
DD
2
3
E1
OUT-
SCL
Negative Left-Speaker Output
D2
Serial Clock Input. Connect a 1kΩ pullup resistor from SCL to V
.
DD
4, 29
5
D1, F3
C1
PGND
OUT+
SDA
Power Ground
Positive Left-Speaker Output
6
C2
Serial Data Input. Connect a 1kΩ pullup resistor from SDA to V
.
DD
B1, B2,
E6, F2,
F4, F5
7, ±, 23,
26, 2±, 31
Internal Connection. Leave unconnected. This pin is internally connected to the signal path.
Do not connect together or to any other pin.
I.C.
9
A1
A2
B3
A3
A4
B4
A5
A6
B5
B6
C5
C6
D6
D5
E5
F6
E4
E3
E2
CPV
Charge-Pump Power Supply
DD
10
11
12
13
14
15
16
17
1±
19
20
21
22
24
25
27
30
32
C1P
VBIAS
Charge-Pump Flying Capacitor Positive Terminal
Common-Mode Bias
5/MAX976
CPGND Charge-Pump GND
C1N
Charge-Pump Flying Capacitor Negative Terminal
Input C1. Left input or positive input (see Table 5a).
INC1
CPV
Charge-Pump Output. Connect to V
.
SS
SS
HPL
Left Headphone Output
V
Headphone Amplifier Negative Power Supply. Connect to CPV
.
SS
SS
HPR
INC2
Right Headphone Output
Input C2. Right input or negative input (see Table 5a).
Mono Receiver Output
OUTRx
V
Analog Power Supply
DD
INB2
INB1
GND
INA2
INA1
SHDN
Input B2. Right input or negative input (see Table 5a).
Input B1. Left input or positive input (see Table 5a).
Analog Ground
Input A2. Right input or negative input (see Table 5a).
Input A1. Left input or positive input (see Table 5a).
Active-Low Hardware Shutdown
Exposed Pad. The external pad lowers the package’s thermal impedance by providing a
direct heat conduction path from the die to the PCB. The exposed pad is internally connected
to GND. Connect the exposed thermal pad to the GND plane.
EP
—
EP
16 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
Typical Application Circuits
V
DD
V
DD
C2
1μF
1μF
0.1μF
1μF
CPV
V
SS
V
DD
PV
DD
SS
15 (A5) 17 (B5)
21 (D6)
1 (F1)
C1N 13 (A4)
CPGND 12 (A3)
C1P 10 (A2)
C1
1μF
10kΩ
CHARGE
PUMP
V
DD
DirectDrive
3dB
CPV
9 (A1)
DD
16 (A6) HPL
18 (B6) HPR
20 (C6) OUTRx
C3
1μF
RIGHT
VOLUME
1μF
30 (E3)
27 (E4)
INA1
INA2
3dB
3dB
INPUT A: 0dB,
6dB, OR 20dB
1μF
1μF
LEFT
VOLUME
OUTPUT
MIXER
24 (E5)
22 (D5)
INB1
INB2
INPUT B: 0dB
OR 6dB
INPUT
MIXER
12dB
CLASS D
5 (C1) OUTL+
2 (E1) OUTL-
1μF
1μF
MONO
VOLUME
AMPLIFIER
14 (B4)
19 (C5)
INC1
INC2
MAXIM 3D
SOUND
INPUT C: 0dB
OR 6dB
12dB
28 (F4) OUTR+
31 (F2) OUTR-
CLASS D
AMPLIFIER
1μF
VBIAS
11 (B3)
1μF
6 (C2)
3 (D2)
32 (E2)
SDA
SCL
MAX9775
2
I C CONTROL
3D CIRCUIT
SHDN
25 (F6)
GND
4 (D1) 29 (F3)
23 (E6)
26 (F5)
7 (B1)
8 (B2)
PGND
PGND
CR_L
2.2nF
CR_H
22nF
CL_L
2.2nF
CL_H
22nF
______________________________________________________________________________________ 17
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Typical Application Circuits (continued)
V
DD
V
DD
C2
1μF
1μF
0.1μF
1μF
CPV
V
SS
V
DD
PV
DD
SS
15 (A5) 17 (B5)
21 (D6)
1 (F1)
C1N 13 (A4)
CPGND 12 (A3)
C1P 10 (A2)
C1
1μF
10kΩ
CHARGE
PUMP
V
DD
CPV
9 (A1)
DD
DirectDrive
3dB
5/MAX976
C3
1μF
16 (A6) HPL
RIGHT
1μF
VOLUME
INA1
INA2
30 (E3)
27 (E4)
INPUT A: 0dB,
6dB, OR 20dB
18 (B6) HPR
3dB
3dB
1μF
1μF
LEFT
VOLUME
20 (C6) OUTRx
OUTPUT
MIXER
24 (E5)
22 (D5)
INB1
INB2
INPUT B: 0dB
OR 6dB
INPUT
MIXER
12dB
1μF
1μF
MONO
VOLUME
5 (C1) OUT+
2 (E1) OUT-
CLASS D
AMPLIFIER
14 (B4)
19 (C5)
INC1
INC2
INPUT C: 0dB
OR 6dB
1μF
VBIAS
11 (B3)
1μF
6 (C2)
3 (D2)
32 (E2)
SDA
SCL
MAX9776
2
I C CONTROL
SHDN
25 (F6)
GND
4 (D1) 29 (F3)
PGND
PGND
18 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
DirectDrive allows the headphone and mono receiver
Detailed Description
amplifiers to output ground-referenced signals from a
The MAX9775/MAX9776 ultra-low-EMI, filterless, Class D
single supply, eliminating the need for large DC-block-
audio power amplifiers feature several improvements to
ing capacitors. Comprehensive click-and-pop suppres-
switch-mode amplifier technology. The MAX9775/
sion minimizes audible transients during the turn-on
MAX9776 feature active emissions limiting circuitry to
and turn-off of amplifiers.
reduce EMI. Zero dead-time technology maintains state-
of-the-art efficiency and THD+N performance by allowing
the output FETs to switch simultaneously without cross-
conduction. A unique filterless modulation scheme and
spread-spectrum modulation create compact, flexible,
low-noise, efficient audio power amplifiers while
occupying minimal board space. The differential input
architecture reduces common-mode noise pickup with or
without the use of input-coupling capacitors. The
MAX9775/MAX9776 can also be configured as single-
ended input amplifiers without performance degradation.
Class D Speaker Amplifier
Comparators monitor the audio inputs and compare the
complementary input voltages to a sawtooth waveform.
The comparators trip when the input magnitude of the
sawtooth exceeds their corresponding input voltage. The
active emissions limiting circuitry slightly reduces the
turn-on rate of the output H-bridge by slew-rate limiting
the comparator output pulse. Both comparators reset at
a fixed time after the rising edge of the second compara-
tor trip point, generating a minimum-width pulse
(t
,100ns typ) at the output of the second com-
ON(MIN)
The MAX9775/MAX9776 feature three fully differential
input pairs (INA_, INB_, INC_) that can be configured
as stereo single-ended or mono differential inputs. I2C
provides control for input configuration, volume level,
and mixer configuration. The MAX9775’s 3D enhance-
ment feature widens the stereo sound field to improve
stereo imaging when stereo speakers are placed in
close proximity.
parator (Figure 1). 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 the net voltage across the speak-
er (V
- V
) to change. The minimum-width pulse
OUT+
OUT-
helps the devices to achieve high levels of linearity.
t
SW
V
IN-
V
IN+
OUT-
OUT+
t
ON(MIN)
V
- V
OUT-
OUT+
Figure 1. Outputs with an Input Signal Applied
______________________________________________________________________________________ 19
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
cycle-to-cycle variation of the switching period does not
degrade audio reproduction or efficiency (see the
Typical Operating Characteristics). Select spread-spec-
trum modulation mode through the I2C interface (Table
2). In spread-spectrum modulation mode, the switching
frequency varies randomly by ±±30Hz around the center
frequency (1.16MHz). The modulation scheme remains
the same, but the period of the sawtooth waveform
changes from cycle to cycle (Figure 2). Instead of a
large amount of spectral energy present at multiples of
the switching frequency, the energy is now spread over
a bandwidth that increases with frequency. Above a few
megahertz, the wideband spectrum loo0s li0e white
noise for EMI purposes (see Figure ±).
Operating Modes
Fixed-Frequency Modulation
The MAX9775/MAX9776 feature a fixed-frequency
modulation mode with a 1.1MHz switching frequency,
set through the I2C interface (Table 2). In fixed-frequen-
cy modulation mode, the frequency spectrum of the
Class D output consists of the fundamental switching
frequency and its associated harmonics (see the
Wideband Output Spectrum Fixed-Frequency Mode
graph in the Typical Operating Characteristics).
Spread-Spectrum Modulation
The MAX9775/MAX9776 feature a unique spread-spec-
trum modulation that flattens the wideband spectral com-
ponents. Proprietary techniques ensure that the
t
t
t
t
SW
5/MAX976
SW
SW
SW
V
IN-
V
IN+
OUT-
OUT+
t
ON(MIN)
V
OUT+
- V
OUT-
Figure 2. Output with an Input Signal Applied (Spread-Spectrum Modulation Mode)
20 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
40.0
35.0
30.0
EN55022B LIMIT
25.0
20.0
15.0
10.0
5.0
30.0
60.0
80.0
100.0
120.0
140.0
160.0
180.0
200.0
220.0
240.0
260.0
280.0
300.0
FREQUENCY (MHz)
Figure 3. EMI with 76mm of Speaker Cable
______________________________________________________________________________________ 21
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Filterless Modulation/Common-Mode Idle
The MAX9775/MAX9776 use Maxim’s unique modula-
tion scheme that eliminates the LC filter required by tra-
ditional Class D amplifiers, improving efficiency,
V
= 0V
IN
reducing component count, conserving board space
and system cost. Conventional Class D amplifiers out-
put a 50% duty-cycle square wave when no signal is
present. With no filter, the square wave appears across
the load as a DC voltage, resulting in finite load current,
increasing power consumption, especially when idling.
When no signal is present at the input of the
MAX9775/MAX9776, the outputs switch as shown in
Figure 4. Because the MAX9775/MAX9776 drive the
speaker differentially, the two outputs cancel each
other, resulting in no net idle mode voltage across the
speaker, minimizing power consumption.
OUT-
OUT+
DirectDrive
Traditional single-supply headphone amplifiers have
outputs biased at a nominal DC voltage (typically half
the supply) for maximum dynamic range. Large cou-
pling capacitors are needed to block this DC bias from
the headphone. Without these capacitors, a significant
amount of DC current flows to the headphone, resulting
in unnecessary power dissipation and possible dam-
age to both headphone and headphone amplifier.
5/MAX976
V
- V = 0V
OUT+ OUT-
Figure 4. Outputs with No Input Signal
In addition to the cost and size disadvantages of the
DC-blocking capacitors required by conventional head-
phone amplifiers, these capacitors limit the amplifier’s
low-frequency response and can distort the audio sig-
nal. Previous attempts at eliminating the output-cou-
pling capacitors involved biasing the headphone return
(sleeve) to the DC bias voltage of the headphone
amplifiers. This method raises some issues:
Maxim’s DirectDrive architecture uses a charge pump to
create an internal negative supply voltage. This allows the
headphone outputs of the MAX9775/MAX9776 to be
biased at GND, almost doubling 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 (220µF, typ) tantalum capacitors, the
MAX9775/MAX9776 charge pump requires two small
ceramic capacitors, conserving board space, reducing
cost, and improving the frequency response of the head-
phone amplifier. See the Output Power vs. Load
Resistance and Charge-Pump Capacitor Size graph in
the Typical Operating Characteristics for details of the
possible capacitor sizes. There is a low DC voltage on
the amplifier outputs due to amplifier offset. However, the
offset of the MAX9775/MAX9776 is typically 1.4mV,
which, when combined with a 32Ω load, results in less
than 44nA of DC current flow to the headphones.
1) The sleeve is typically grounded to the chassis.
Using the midrail biasing approach, the sleeve must
be isolated from system ground, complicating prod-
uct design.
2) During an ESD strike, the driver’s ESD structures are
the only path to system ground. Thus, the amplifier
must be able to withstand the full ESD strike.
3) When using the headphone jack as a lineout to
other equipment, the bias voltage on the sleeve may
conflict with the ground potential from other equip-
ment, resulting in possible damage to the amplifiers.
22 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
Q
R
RIGHT
V
DD
RIGHT
LISTENER
LEFT
+
+
I
L
d
V
DD
/ 2
V
OUT
I
R
GND
LEFT
Q
L
CONVENTIONAL DRIVER-BIASING SCHEME
Figure 6. MAX9775 3D Stereo Enhancement
+V
DD
With Maxim’s 3D stereo enhancement, it is possible to
emulate stereo sound in situations where the speakers
must be positioned close together. As shown in Figure
6, wave interference can be used to cancel the left
channel in the vicinity of the listener’s right ear and vice
versa. This technique can yield an apparent separation
between the speakers that is a factor of four or greater
than the actual physical separation.
V
OUT
GND
-V
DD
The external capacitors CL_L, CL_H, CR_L, and CR_H
set the starting and stopping range of the 3D effect.
CL_H and CR_H are for the lower limit (in the MAX9775
Typical Application Circuit, it is 1kHz), CR_L and CL_L
are for the higher limit (10kHz). The internal resistor is
typically 7kΩ and the frequencies are calculated as:
DirectDrive BIASING SCHEME
Figure 5. Traditional Amplifier Output vs. MAX9775/MAX9776
DirectDrive Output
Charge Pump
The MAX9775/MAX9776 feature a low-noise charge
pump. The switching frequency of the charge pump is
half the switching frequency of the Class D amplifier,
regardless of the operating mode. The nominal switch-
ing frequency is well beyond the audio range, and thus
does not interfere with the audio signals, resulting in an
SNR of 93dB. Although not typically required, addition-
al high-frequency noise attenuation can be achieved by
increasing the size of C2 (see the Typical Application
Circuits). The charge pump is active in both speaker
and headphone modes.
1
3D_START =
2πRC
where R = 7kΩ and C = CR_H and CL_H.
1
3D_STOP =
2πRC
where R = 7kΩ and C = CR_L and CL_L.
For example, with CR_L = CL_L = 2.2nF and CR_H =
CL_H = 22nF, the 3D start frequency is 1kHz and the
3D stop frequency is 10kHz.
3D Enhancement
The MAX9775 features a 3D stereo enhancement func-
tion, allowing the MAX9775 to widen the stereo sound field
and immerse the listener in a cleaner, richer sound experi-
ence. Note the MAX9776, mono Class D speaker amplifier
does not feature 3D stereo enhancement.
Enabling the 3D sound effect results in an apparent 6dB
gain because the internal left and right signals are mixed
together. This gain can be nulled by volume adjusting
the left and right signals. The volume control can be pro-
grammed through the I2C-compatible interface to com-
pensate for the extra 6dB increase in gain. For example,
As stereo speaker applications become more compact,
the quality of stereophonic sound is jeopardized.
______________________________________________________________________________________ 23
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
if the right and left volume controls are set for a maxi-
mum gain 0dB (11111 in Table 7, IN+6dB = 0 from Table
10) before the 3D effect is activated, the volume control
should be programmed to -6dB (11001 in Table 7)
immediately after the 3D effect has been activated.
in the Input Mixer to create the internal signals L, R,
and M.
In the second stage of amplification, the internal L, R,
and M signals are independently volume adjusted.
Finally, each output amplifier has its own internal gain.
The speaker, headphone, and mono receiver amplifiers
have fixed gains of 12dB, 3dB, and 3dB, respectively.
Signal Path
The audio inputs of the MAX9775/MAX9776—INA, INB,
and INC—are preamplified and then mixed by the input
mixer to create three internal signals: Left (L), Right (R),
and Mono (M). Tables 5a and 5b show how the inputs
are mixed to create L, R, and M. These signals are then
independently volume adjusted by the L, R, and M vol-
ume control and routed to the output mixer. The output
mixer mixes the internal L, R, and M signals to create a
variety of audio mixes that are output to the headphone
speaker and mono receiver amplifiers. Figure 6 shows
the signal path that the audio signals take.
Current-Limit and Thermal Protection
The MAX9775/MAX9776 feature current limiting and
thermal protection to protect the device from short cir-
cuits and overcurrent conditions. The headphone
amplifier pulses in the event of an overcurrent condition
with a pulse every 100µs as long as the condition is
present. Should the current still be high, the above
cycle is repeated. The speaker amplifier current-limit
protection clamps the output current without shutting
down the output. This can result in a distorted output.
Current is limited to 1.6A in the speaker amplifiers and
170mA in the headphone and mono receiver amplifiers.
Signal amplification takes place in three stages. In the
first stage, the inputs (INA, INB, and INC) are pre-
amplified. The amount by which each input is amplified
is determined by the bits INA+20dB (B4 in the Input
Mode Control Register) and IN+6dB (B3 in the Global
Control Register). After preamplification, they are mixed
5/MAX976
The MAX9775/MAX9776 have thermal protection that
disables the device at +150°C until the temperature
decreases to +120°C.
-75dB TO 0dB
12dB
3dB
SPEAKER
RVOL
PREAMPLIFIER
INPUT
-75dB TO 0dB
HEADPHONE
INPUT
OUTPUT
MIXER
MIXER
LVOL
INPUT A:
0dB, 6dB, 20dB
0dB TO 6dB
-75dB TO 0dB
MVOL
3dB
INPUT B AND C:
0dB, 6dB
RECEIVER
MONO
MONO+6dB
Figure 7. Signal Path
24 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
2
Click-and-Pop Suppression
In conventional single-supply headphone amplifiers, the
output-coupling capacitor is a major contributor of audi-
ble clicks and pops. Upon startup, the amplifier charges
the coupling capacitor to its bias voltage, typically half the
supply. Likewise, during shutdown, the capacitor is dis-
charged to GND. This results in a DC shift across the
capacitor, which, in turn, appears as an audible transient
at the speaker. Since the MAX9775/MAX9776 headphone
amplifier does not require output-coupling capacitors, this
problem does not arise.
I C Interface
The MAX9775/MAX9776 feature an I2C 2-wire serial
interface consisting of a serial data line (SDA) and a
serial clock line (SCL). SDA and SCL facilitate commu-
nication between the MAX9775/MAX9776 and the mas-
ter at clock rates up to 400kHz. Figure ± shows the
2-wire interface timing diagram. The MAX9775/
MAX9776 are receive-only slave devices relying on the
master to generate the SCL signal. The master, typical-
ly a microcontroller, generates SCL and initiates data
transfer on the bus. The MAX9775/MAX9776 cannot
write to the SDA bus except to acknowledge the receipt
of data from the master. The MAX9775/MAX9776 will
not acknowledge a read command from the master.
In most applications, the output of the preamplifier dri-
ving the MAX9775/MAX9776 has a DC bias of typically
half the supply. During startup, the input-coupling
capacitor is charged to the preamplifier’s DC bias volt-
age, resulting in a DC shift across the capacitor and an
audible click/pop. An internal delay of 30ms eliminates
the click/pop caused by the input filter.
A master device communicates to the MAX9775/
MAX9776 by transmitting the proper address followed
by the data word. Each transmit sequence is framed by
a START (S) or REPEATED START (Sr) condition and a
STOP (P) condition. Each word transmitted over the
bus is ± bits long and is always followed by an
acknowledge clock pulse.
Shutdown
The MAX9775/MAX9776 feature a 0.1µA hard shutdown
mode that reduces power consumption to extend battery
life and a soft shutdown where current consumption is
typically ±.5µA. Hard shutdown is controlled by connect-
ing the SHDN pin to GND, disabling the amplifiers, bias
circuitry, charge pump, and I2C. In shutdown, the head-
phone amplifier output impedance is 1.4kΩ and the
speaker output impedance is 300kΩ. Similarly, the
MAX9775/MAX9776 enter soft-shutdown when the SHDN
bit = 0 (see Table 2). The I2C interface is active and the
contents of the command register are not affected when
in soft-shutdown. This allows the master to write to the
MAX9775/MAX9776 while in shutdown. The I2C interface
is completely disabled in hardware shutdown. When the
MAX9775/MAX9776 are re-enabled the default settings
are applied (see Table 3).
The MAX9775/MAX9776 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
MAX9775/MAX9776 SCL line operates 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. Series resistors protect the digital inputs of
the MAX9775/MAX9776 from high-voltage spikes on
the bus lines, and minimize crosstalk and undershoot of
the bus signals.
SDA
t
BUF
t
t
SU, STA
SU, DAT
t
t
SP
HD, STA
t
SU, STO
t
t
HD, DAT
LOW
SCL
t
HIGH
t
HD, STA
t
R
t
F
START
CONDITION
REPEATED
START
STOP
CONDITION
START
CONDITION
CONDITION
Figure ±. 2-Wire Serial-Interface Timing Diagram
______________________________________________________________________________________ 25
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Bit Transfer
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). SDA and SCL idle high when the
I2C bus is not busy.
the seven most significant bits (MSBs) followed by the
Read/Write bit. The address is the first byte of informa-
tion sent to the MAX9775/MAX9776 after the START
condition. The MAX9775/MAX9776 are slave devices
only capable of being written to. The Read/Write bit
should be a zero when configuring the MAX9775/
MAX9776.
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
9). A START (S) condition from the master signals the
beginning of a transmission to the MAX9775/MAX9776.
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.
Acknowledge
The acknowledge bit (ACK) is a clocked 9th bit that the
MAX9775/MAX9776 use to handshake receipt of each
byte of data (see Figure 10). The MAX9775/MAX9776
pull down SDA during the master-generated 9th 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 may reattempt communications.
5/MAX976
Early STOP Conditions
The MAX9775/MAX9776 recognize a STOP condition at
any point during data transmission except if the STOP
condition occurs in the same high pulse as a START
condition.
Table 1. MAX9775/MAX9776 Address Map
SLAVE ADDRESS
PART
A6
1
A5
0
A4
0
A3
1
A2
1
A1
0
A0 R/W
MAX9775
MAX9776
0
1
0
0
Slave Address
The MAX9775/MAX9776 are available with one preset
slave address (see Table 1). The address is defined as
1
0
0
1
1
0
S
Sr
P
CLOCK PULSE FOR
ACKNOWLEDGMENT
START
CONDITION
SCL
SDA
SCL
1
2
8
9
NOT ACKNOWLEDGE
SDA
ACKNOWLEDGE
Figure 10. Acknowledge
Figure 9. START, STOP, and REPEATED START Conditions
26 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
The MAX9775/MAX9776 only accept write data, but
COMMAND BYTE IS STORED ON
RECEIPT OF STOP CONDITION
they acknowledge the receipt of the address byte with
the R/W bit set high. The MAX9775/MAX9776 do not
write to the SDA bus in the event that the R/W bit is set
high. Subsequently, the master reads all 1’s from the
MAX9775/MAX9776. Always set the R/W bit to zero to
avoid this situation.
B7 B6 B5 B4 B3 B2 B1 B0
ACKNOWLEDGE FROM
MAX9775/MAX9776
S
SLAVE ADDRESS
0
ACK COMMAND BYTE ACK P
ACKNOWLEDGE
FROM MAX9775/MAX9776
R/W
Programming the MAX9775/MAX9776
The MAX9775/MAX9776 are programmed through 6
control registers. Each register is addressed by the 3
MSBs (B5–B7) followed by 5 configure bits (B0–B4) as
shown in Table 2. Correct programming of the
MAX9775/MAX9776 requires writing to all 6 control reg-
isters. Upon power-on, their default settings are as list-
ed in Table 3.
Figure 11. Write Data Format Example
Write Data Format
A write to the MAX9775/MAX9776 includes transmis-
sion of a START condition, the slave address with the
R/W bit set to 0 (Table 1), one byte of data to configure
the Command Register, and a STOP condition. Figure
11 illustrates the proper format for one frame.
Table 2. Control Registers
B7
B6
B5
B4
B3
B2
DATA
B1
B0
FUNCTION
COMMAND
Input Mode Control
Mono Volume Control
Left Volume Control
Right Volume Control
Output Mode Control
Global Control Register
0
0
0
0
1
1
0
0
1
1
0
0
0
1
0
1
0
1
INA+20dB
INMODE (Tables 5a and 5b)
MVOL (Table 7)
LVOL (Table 7)
RVOL (Table 7)
MONO+6dB
OUTMODE (Table 9)
SHDN
IN+6dB
MUTE
SSM
3D/MONO
Table 3. Power-On Reset Conditions
COMMAND
Input Mode (000)
DATA
10000
11111
11111
11111
01000
00011
DESCRIPTION
Input A gain = +20dB; input A, B, and C singled-ended stereo inputs
Maximum volume
Mono Volume (001)
Left Volume (010)
Maximum volume
Right Volume (011)
Output Mode (100)
Global Control Register (101)
Maximum volume
0dB of extra mono gain, mode ±: stereo headphone, stereo speaker
Powered-off, input B/C gain = 0dB, MUTE off, SSM on, 3D/MONO on
______________________________________________________________________________________ 27
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Input Mode Control
Table 4. Input Mode Control Register
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
Input Mode Control
0
0
0
INA+20dB
INMODE (Tables 5a and 5b )
The MAX9775/MAX9776 have three flexible inputs that
can be configured as single-ended stereo inputs or dif-
ferential mono inputs. All input signals are summed into
three unique signals—Left (L), Right (R), and Mono
(M)—which are routed to the output amplifiers. The bit
INA+20dB allows the option of boosting low-level sig-
nals on INA. INA+20dB can be set as follows:
1 = Input A’s gain +20dB for low-level signals such as
FM receivers.
0 = Input A’s gain is either 0dB or +6dB as set by
IN+6dB (bit B3 of the Control Register).
Tables 5a and 5b show how the inputs—INA, INB, and
INC—are mixed to create the internal signals Left (L),
Right (R), and Mono (M).
Table 5a. Input Mode
PROGRAMMING MODE
INPUT CONFIGURATION
INMODE
INA1
INA2
INB1
INB2
INC1
INC2
5/MAX976
B3
0
0
0
0
0
0
0
0
1
1
1
1
B2
0
0
0
0
1
1
1
1
0
0
0
0
B1
0
0
1
1
0
0
1
1
0
0
1
1
B0
0
1
0
1
0
1
0
1
0
1
0
1
L
L
L
R
R
R
L
R
R
L
R
M-
R
L
M+
L
M+
M+
R+
L+
L
M-
M-
R-
L-
R
L
R
M+
L+
R+
L
M-
L-
R-
R
L
L
R
R
M+
M+
M+
M+
M+
M+
M-
M-
M-
M-
M-
M-
L
R
M+
L
M-
R
M+
M+
R+
L+
M-
M-
R-
L-
M+
L+
R+
M-
L-
R-
Table 5b. Internal Signals L, R, and M
PROGRAMMING MODE
INMODE
INTERNAL SIGNALS LEFT (L), RIGHT (R), AND MONO (M)
R
L
M
B3
0
B2
0
B1
0
B0
0
INA1 + INB1 + INC1
INA1 + INB1
INA1 + INC1
INA1
INA2 + INB2 + INC2
INA2 + INB2
INA2 + INC2
INA2
—
0
0
0
1
INC1 - INC2
INB1 - INB2
0
0
1
0
0
0
1
1
(INB1 - INB2) + (INC1 - INC2)
0
0
1
1
0
0
0
1
INA1 + (INC1 - INC2)
INA1 + (INB1 - INB2)
INB1 + INC1
INB1
INA2 + (INB1 - INB2)
INA2 + (INC1 - INC2)
INB2 + INC2
INB2
—
—
0
1
1
0
INA1 - INA2
0
1
1
0
1
0
1
0
(INA1 - INA2) + (INC1 - INC2)
(INA1 - INA2) + (INB1 - INB2)
INC1
INC2
(INA1 - INA2) + (INB1 - INB2)
+ (INC1 - INC2)
1
0
0
1
—
—
1
1
0
0
1
1
0
1
INC1 - INC2
INB1 - INB2
INB1 - INB2
INC1 - INC2
INA1 - INA2
INA1 - INA2
28 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
Mono/Left/Right Volume Control
Table 6. Mono/Left/Right Volume Control Registers
REGISTER
Mono Volume Control
B7
0
B6
0
B5
1
B4
B3
B2
B1
B0
MVOL
LVOL
RVOL
Left Volume Control
Right Volume Control
0
1
0
0
1
1
The MAX9775/MAX9776 have separate volume controls
for each of the internal signals: Left (L), Right (R), and
Mono (M). The final gain of each signal is determined
by the way the following bits are set: MVOL, LVOL,
RVOL, INA+20dB, IN+6dB, and MONO+6dB. Table 7
shows how to configure the L, R, and M amplifiers for
specific gains.
Table 7. Volume Control Settings
MVOL/LVOL/RVOL
GAIN (dB)
MVOL/LVOL/RVOL
GAIN (dB)
B4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
B3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
B2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
B1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
B0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
B4
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
B3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
B2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
B1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
B0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Mute
-75
-71
-67
-63
-59
-55
-51
-47
-44
-41
-3±
-35
-32
-29
-26
-23
-21
-19
-17
-15
-13
-11
-9
-7
-6
-5
-4
-3
-2
-1
0
______________________________________________________________________________________ 29
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Output Mode Control
Table 8. Output Mode Control Register
REGISTER
Output Mode Control
B7
B6
B5
B4
B3
B2
B1
B0
1
0
0
MONO+6dB
OUTMODE (Table 9)
MONO+6dB in the Output Mode Control register allows
an extra 6dB of gain on the internal mono signal:
amplifier, and a stereo Class D amplifier. The MAX9776
has four output amplifiers: a mono receiver amplifier, a
stereo DirectDrive headphone amplifier, and a mono
Class D amplifier.
1 = Additional 6dB of gain is applied to the internal
Mono (M) signal path.
Table 9 shows how each of the three internal signals—
Left (L), Right (R), and Mono (M)—are mixed and rout-
ed to the various outputs.
0 = No additional gain is applied to the Internal Mono
(M) signal path.
The MAX9775 has five output amplifiers: a mono
receiver amplifier, a stereo DirectDrive headphone
Table 9. Output Modes
5/MAX976
OUTMODE
MAX9775
MAX9776
MODE
RECEIVER
LEFT HP
RIGHT HP
RIGHT
B3
0
B2
0
B1
0
B0
0
LEFT SPK
SPK
—
0
1
2
3
4
5
—
M
—
—
—
M
—
—
—
M
—
—
M
—
—
M
0
0
0
1
—
0
0
1
0
—
M
0
0
1
1
—
M
M
M
0
1
0
0
—
M
M
—
—
—
—
—
0
1
0
1
—
—
—
—
1
6
0
1
1
0
/ (L + R)
2
—
—
—
—
—
7
±
0
1
1
1
1
0
0
0
1
0
0
1
1
0
1
0
—
—
—
—
1
—
L
—
R
L
L
R
R
L + R
L + R
—
9
L
R
—
—
—
—
10
—
—
—
11
1
0
1
1
M + / (L + R)
2
—
—
—
—
—
12
13
14
15
1
1
1
1
1
1
1
1
0
0
1
1
0
1
0
1
—
—
—
—
L + M
L + M
—
R + M
R + M
—
L + R + 2M
L + R + 2M
—
L + M
L + M
MUTE
R + M
R + M
MUTE
—
MUTE
MUTE
MUTE
MUTE
— = Amplifier off.
L = Left signal.
R = Right signal.
M = Mono signal.
30 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
Global Control Register
Table 10. Global Control Register
REGISTER
Global Control Register
B7
B6
B5
B4
B3
B2
B1
B0
1
0
1
SHDN
IN+6dB
MUTE
SSM
3D/MONO
The Global Control Register is used for global configu-
rations, those affecting all inputs and outputs. The bits
in the control register are shown in Table 11.
Table 11. Global Control Register Configurations
BIT
NAME
FUNCTION
1 = Normal operation
B4
SHDN
0 = Low-power shutdown mode. I2C settings are saved.
1 = All input signals are boosted by 6dB.
0 = All input signals are passed un-amplified.
This bit does not affect INA if the INA+20dB bit (B4 of the Input Mode Control Register) is set to
1, in which case INA is boosted by 20dB.
B3
IN+6dB
1 = Mute all outputs.
0 = All outputs are active.
B2
B1
MUTE
SSM
1 = Spread-spectrum Class D modulation.
0 = Fixed-frequency Class D modulation.
MAX9775:
1 = 3D Enhancement is on.
B0
3D/MONO
0 = 3D Enhancement is off.
1 = Speakers will output L+R in modes 7, ±, 12, and 13 (see Table 9).
0 = Speakers will output L in modes 7, ±, 12, and 13 (see Table 9).
of most speakers, voice coil movement due to the
Applications Information
square-wave frequency is very small. Although this move-
ment is small, a speaker not designed to handle the addi-
tional power may be damaged. For optimum results use a
speaker with a series inductance > 10µH. Typical ±Ω
speakers, for portable audio applications, exhibit series
inductances in the 20µH to 100µH range.
Class D Filterless Operation
Traditional Class D amplifiers require an output filter to
recover the audio signal from the amplifier’s PWM out-
put. The filters add cost, increase the solution size of
the amplifier, and can decrease efficiency. The tradi-
tional PWM scheme uses large differential output
Input Amplifier
swings (2 x V
) and causes large ripple currents.
DD(P-P)
Any parasitic resistance in the filter components results
in a loss of power, lowering the efficiency.
Differential Input
The MAX9775/MAX9776 feature a programmable differ-
ential input structure, making it compatible with many
CODECs, and offering improved noise immunity over a
single-ended input amplifier. In devices such as cell
phones, high-frequency signals from the RF transmitter
can be picked up by the amplifier’s input traces. The
signals appear at the amplifier’s inputs as common-
mode noise. A differential input amplifier amplifies the
difference of the two inputs and any signal common to
both is cancelled.
The MAX9775/MAX9776 do not require an output filter.
The device relies on the inherent inductance of the
speaker coil and the natural filtering of both the speak-
er and the human ear to recover the audio component
of the square-wave output. Eliminating the output filter
results in a smaller, less costly, more efficient solution.
Because the switching frequency of the MAX9775/
MAX9776 speaker output is well beyond the bandwidth
______________________________________________________________________________________ 31
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Single-Ended Input
The MAX9775/MAX9776 can be configured as a single-
ended input amplifier by appropriately configuring the
Input Control Register (see Tables 5a and 5b).
cally 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.
DC-Coupled Input
The input amplifier can accept DC-coupled inputs that
are biased to the amplifier’s bias voltage. DC-coupling
eliminates the input-coupling capacitors; reducing com-
ponent count to potentially six external components
(see the Typical Application Circuits). However, the
highpass filtering effect of the capacitors is lost, allow-
ing low-frequency signals to feed through to the load.
Class D Output Filter
The MAX9775/MAX9776 do not require a Class D out-
put filter. The devices pass EN55022B emission stan-
dards with 152mm of unshielded speaker cables.
However, output filtering can be used if a design is fail-
ing radiated emissions due to board layout or cable
length, or the circuit is near EMI-sensitive devices. Use
a ferrite bead filter when radiated frequencies above
10MHz are of concern. Use an LC filter when radiated
frequencies below 10MHz are of concern, or when long
leads (> 152mm) connect the amplifier to the speaker.
Figure 12 shows optional speaker amplifier output filters.
Unused Inputs
Connect any unused input pin directly to VBIAS. This
saves input capacitors on unused inputs and provides
the highest noise immunity on the input.
Component Selection
5/MAX976
External Component Selection
Input Filter
An input capacitor (C ) in conjunction with the input
IN
BIAS Capacitor
impedance of the MAX9775/MAX9776 form a highpass
filter that removes the DC bias from the incoming signal.
The AC-coupling capacitor allows the amplifiers to auto-
matically bias the signal to an optimum DC level.
Assuming zero source impedance, the -3dB point of the
highpass filter is given by:
V
is the output of the internally generated DC bias
BIAS
voltage. The V
bypass capacitor, C
improves
BIAS
VBIAS
PSRR and THD+N by reducing power supply and other
noise sources at the common-mode bias node, and
also generates the clickless/popless, startup/shutdown
DC bias waveforms for the speaker amplifiers. Bypass
V
BIAS
with a 1µF capacitor to GND.
1
f−3dB
Choose C so that f
=
2πR C
IN IN
22Ω
is well below the lowest fre-
-3dB
IN
quency of interest. Use capacitors whose dielectrics
have low-voltage coefficients, such as tantalum or alu-
minum electrolytic. Capacitors with high-voltage coeffi-
cients, such as ceramics, may result in increased
distortion at low frequencies.
0.033μF
0.033μF
0.1μF
33μH
OUT_+
OUT_-
0.47μF
0.1μF
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 cell
phones and two-way radios need only concentrate on
the frequency range of the spoken human voice (typi-
33μH
22Ω
Figure 12. Speaker Amplifier Output Filter
32 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
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. Most
surface-mount ceramic capacitors satisfy the ESR
requirement. For best performance over the extended
temperature range, select capacitors with an X7R dielec-
tric or better. Table 12 lists suggested manufacturers.
Connect all of the power-supply inputs (CPV , V
,
DD
DD
and PV ) together. Bypass CPV
with a 1µF capaci-
DD
DD
tor to CPGND. Bypass V
Bypass PV
with 1µF capacitor to GND.
with a 1µF capacitor in parallel with a
DD
DD
0.1µF capacitor to PGND. Place the bypass capacitors
as close to the MAX9775/MAX9776 as possible. Place
a bulk capacitor between PV
and PGND if needed.
DD
Use large, low-resistance output traces. Current drawn
from the outputs increases as load impedance
decreases. High output trace resistance decreases the
power delivered to the load. Large output, supply, and
GND traces also allow more heat to move from the
MAX9775/MAX9776 to the PCB, decreasing the thermal
impedance of the circuit.
Flying Capacitor (C1)
The value of the flying capacitor (C1) affects the 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 reduces the charge-pump out-
put resistance to an extent. Above 1µF, the on-resistance
of the switches and the ESR of C1 and C2 dominate.
TQFN Applications Information
The MAX9776 TQFN-EP package features an exposed
thermal pad on its underside. This pad lowers the
package’s thermal impedance by providing a direct
heat conduction path from the die to the PCB. The
exposed pad is internally connected to GND. Connect
the exposed thermal pad to the PCB GND plane.
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. Load Resistance and Charge-Pump Capacitor Size
graph in the Typical Operating Characteristics.
WLP Applications Information
For the latest application details on WLP construction,
dimensions, tape carrier information, PCB techniques,
bump-pad layout, and recommended reflow tempera-
ture profile, as well as the latest information of reliability
testing results, refer to Application Note 1±91:
Understanding the Basics of the Wafer-Level Chip-
Scale Package (WL-CSP) available on Maxim’s website
at www.maxim-ic.com/ucsp.
CPV
Bypass Capacitor (C3)
DD
The CPV
bypass capacitor (C3) lowers the output
DD
impedance of the power supply and reduces the
impact of the MAX9775/MAX9776’s charge-pump
switching transients. Bypass CPV
and place it physically close to the CPV
Use a value for C3 that is equal to C1.
with C3 to PGND
DD
and PGND.
DD
WLP Thermal Consideration
When operating at maximum output power, the WLP
thermal dissipation can become a limiting factor. The
WLP package does not dissipate as much power as a
TQFN and as a result will operate at a higher tempera-
ture. At peak output power into a 4Ω load, the
MAX9775/MAX9776 can exceed its thermal limit, trig-
gering thermal protection. As a result, do not choose
the WLP package when maximum output power into 4Ω
is required.
Supply Bypassing, 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. Large traces also aid in mov-
ing heat away from the package. Proper grounding
improves audio performance, minimizes crosstalk
between channels, 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 switching transients away from GND
and the traces/components in the audio signal path.
Table 12. Suggested Capacitor Manufacturers
SUPPLIER
Taiyo Yuden
TDK
PHONE
FAX
WEBSITE
www.t-yuden.com
www.component.tdk.com
±00-34±-2496
±07-±03-6100
±47-925-0±99
±47-390-4405
______________________________________________________________________________________ 33
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Pin Configurations
TOP VIEW
(BUMPS ON BOTTOM)
1
2
3
4
5
6
1
2
3
4
5
6
CPV
C1P
CPGND
CPV
SS
C1N
HPL
CPV
C1P
CPGND
CPV
DD
C1N
HPL
DD
SS
A
B
A
B
I.C.
I.C.
SDA
VBIAS
V
INC1
HPR
CL_L
OUTL+
PGND
OUTL-
CL_H
SDA
VBIAS
V
SS
INC1
HPR
SS
OUT+
PGND
OUT-
INC2
INB2
INB1
OUTRx
INC2
INB2
INB1
OUTRx
C
D
E
C
D
E
MAX9776
MAX9775
SCL
V
DD
SCL
V
DD
SHDN
INA1
INA2
I.C.
I.C.
SHDN
INA1
INA2
CR_L
GND
5/MAX976
PV
DD
I.C.
PGND
I.C.
GND
PV
DD
OUTR-
PGND
OUTR+
CR_H
F
F
WLP
WLP
TOP VIEW
32 31 30 29 28 27 26 25
PV
1
2
3
4
5
6
7
8
24 INB1
DD
I.C.
OUT-
SCL
23
+
*EP
22 INB2
PGND
OUT+
SDA
I.C.
21 V
DD
20 OUTRx
19 INC2
18 HPR
MAX9776
I.C.
17 V
SS
9
10 11 12 13 14 15 16
TQFN-EP*
Chip Information
PROCESS: BiCMOS
34 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
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.)
______________________________________________________________________________________ 35
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
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.)
5/MAX976
36 ______________________________________________________________________________________
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
5/MAX976
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.)
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
36 WLP
W363A3+3
T3255-4
21-0024
21-0140
32 TQFN-EP
______________________________________________________________________________________ 37
2 x 1.5W, Stereo Class D Audio Subsystem
with DirectDrive Headphone Amplifier
Revision History
REVISION REVISION
PAGES
CHANGED
DESCRIPTION
NUMBER
DATE
0
1
3/07
7/07
Initial release
—
Initial release of MAX9776 UCSP package and updated Tables 3 and 5b
1, 7, 27, 2±
Initial release of MAX9775 UCSP and removal of MAX9775 TQFN, updated Pin
Description and Table 9
2
9/07
1, 12, 15, 30, 33, 34
3
4
1/0±
±/0±
Updated the Typical Application Circuits
17, 1±
Changed package code and drawing
1, 33, 34, 37
5/MAX976
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.
38 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 200± Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
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