EVALUATION KIT AVAILABLE
MAX9729
Stereo Headphone Amplifier with BassMax,
Volume Control, and Input Mux
General Description
The MAX9729 stereo DirectDrive® headphone amplifier
features bass boost, volume control, an input mux, and
an I
2
C/SMBus-compatible serial interface. This makes
the MAX9729 ideal for portable audio applications where
space is at a premium and performance is essential. The
MAX9729 operates from a single 1.8V to 3.6V, and uses
Maxim’s DirectDrive architecture, eliminating the need for
large DC-blocking capacitors. The headphone amplifiers
deliver 52mW into a 32Ω load, feature low 0.03% THD+N,
and high 90dB PSRR. Maxim’s industry-leading click-and-
pop suppression circuitry reduces audible transients during
power and shutdown cycles.
The BassMax feature boosts the bass response of the ampli-
fier, improving audio reproduction for low-end headphones.
The integrated volume control features 32 discrete volume
levels along with a ramping function to ensure smooth
transitions during shutdown cycles and input selection. The
MAX9729’s eight programmable maximum gain settings
allow for a wide range of input signal levels. A 3:1 multi-
plexer/mixer allows the selection and summation of multiple
stereo input signal sources. The MAX9729 also includes a
dedicated BEEP input with independent attenuation control.
BassMax, volume control, gain settings, and input selection
are controlled using the I
2
C/SMBus-compatible serial inter-
face. A lowpower, 5μA shutdown mode is controlled through
an external logic input or the serial interface.
The MAX9729 consumes only 4.8mA of supply current,
provides short-circuit and thermal-overload protection,
and is specified over the -40°C to +85°C extended tem-
perature range. The MAX9729 is available in a spacesav-
ing 28-pin
thin QFN package (5mm x 5mm x 0.8mm).
Pin Configuration appears at end of data sheet.
Features
●
●
●
●
●
●
●
●
●
●
●
●
DirectDrive Headphone Amplifier Eliminates
Bulky DC-Blocking Capacitors
3:1 Input Multiplexer with Digital-Fade Circuitry
Software-Enabled Bass Boost
32-Step Integrated Volume Control
Beep Input with Programmable Output Level
Low Quiescent Current
Industry-Leading Click-and-Pop Suppression
I
2
C-Compatible 2-Wire Interface
Short-Circuit Protection
1.8V to 3.6V Single-Supply Operation
Available in Space-Saving, Thermally Efficient
28-Pin TQFN-EP (5mm x 5mm x 0.8mm)
● MP3/PMP Players
● Flat-Panel TVs
Applications
● Portable CD/DVD/MD
Players
● Cell Phones
Ordering Information
PART
MAX9729ETI+
PIN-
PACKAGE
28 TQFN-EP**
SLAVE
ADDRESS*
101000_
Note:
This device operates over the -40°C to +85°C operating
temperature range.
+Denotes
lead-free package.
*Last digit of slave address is pin programmable.
**EP = Exposed pad.
DirectDrive is a registered trademark of Maxim Integrated
Products, Inc.
Simplified Block Diagram
1.8V TO 3.6V
SCL
SDA
INL1
INL2
INL3
INR1
INR2
INR3
BEEP
MIXER
MUX
FADER
CONTROL
PGA
PGA
VOLUME
CONTROL
BML
I
2
C INTERFACE
BassMax
MAX9729
Σ
OUTL
Σ
OUTR
BMR
BassMax
19-0857; Rev 1; 5/14
MAX9729
Stereo Headphone Amplifier with BassMax,
Volume Control, and Input Mux
Absolute Maximum Ratings
V
DD
, PV
DD
to PGND or SGND
...............................-0.3V
to +4V
V
DD
to PV
DD
..............................................
Internally Connected
PV
SS
to SV
SS
....................................................................±0.3V
SGND to PGND
..................................................................±0.3V
C1P to PGND
...........................................
-0.3V to (V
DD
+ 0.3V)
C1N to PGND
.........................................
(PV
SS
- 0.3V) to +0.3V
PV
SS
, SV
SS
to PGND
.............................................+0.3V
to -4V
INL_, INR_, BEEP to SGND
.......(SV
SS
- 0.3V) to (V
DD
+ 0.3V)
SDA, SCL, BEEP_EN to PGND
..............................-0.3V
to +4V
SHDN
to PGND
........................................
-0.3V to (V
DD
+ 0.3V)
OUT_ to PGND
..........................................................-3V
to +3V
BM_ to SGND.............................................................-2V to +2V
Duration of OUT_ Short Circuit to PGND..................Continuous
Continuous Current Into/Out of:
V
DD
, C1P, C1N, PGND, PV
SS
, SV
SS
, or OUT_
.........±0.85A
All other pins .................................................................±20mA
Continuous Power Dissipation (T
A
= +70°C, multilayer board)
28-Pin Thin QFN (derate 28.6mW/°C above +70°C) 0.2286mW
Junction-to-Ambient Thermal Resistance (θ
JA
)
28-Pin TQFN
...............................................................35°C/W
Operating Temperature Range
...........................
-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range
............................
-65°C to +150°C
OUT_ ESD Protection (Human Body Model)
......................±8kV
ESD Protection of All Other Pins
.........................................±2kV
Lead Temperature (soldering, 10s)
.................................
+300°C
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 (3V Supply)
(V
DD
= PV
DD
=
SHDN
= 3V, PGND = SGND = 0V, C1 = C2 = C3 = 1μF, BM_ = 0V, maximum gain setting = 6dB, volume attenuation
setting = -16dB (overall gain = -10dB), BassMax disabled. Load connected between OUT_ and PGND where specified. THD+N mea-
surement BW = 22Hz to 22kHz. T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
GENERAL
Supply Voltage Range
Charge-Pump and Logic Supply
Voltage
Quiescent Supply Current
Shutdown Supply Current
Turn-On Time
Beep Enable Time
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
HEADPHONE AMPLIFIER
Input Resistance
Output Offset Voltage
BMR, BML Input Bias Current
R
IN
V
OSHP
I
BIAS_BM
Applicable to all maximum gain and
volume settings
Measured between OUT_ and SGND,
overall gain = -10dB (Note 3)
14
25
±0.7
±10
35
±3.5
±100
kΩ
mV
nA
V
DD
PV
DD
I
DD
I
DD_SHDN
t
ON
t
ON_BEEP
T
THRES
T
HYST
(Note 2)
(Note 2)
No load, BEEP_EN = V
DD
(Note 3)
V
SHDN
= 0V
From shutdown mode to full operation
1.8
1.8
5.5
5
200
12
146
13
3.6
3.6
8
10
V
V
mA
µA
µs
µs
°C
°C
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
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Maxim Integrated
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2
MAX9729
Stereo Headphone Amplifier with BassMax,
Volume Control, and Input Mux
Electrical Characteristics (3V Supply)
(continued)
(V
DD
= PV
DD
=
SHDN
= 3V, PGND = SGND = 0V, C1 = C2 = C3 = 1μF, BM_ = 0V, maximum gain setting = 6dB, volume attenuation
setting = -16dB (overall gain = -10dB), BassMax disabled. Load connected between OUT_ and PGND where specified. THD+N mea-
surement BW = 22Hz to 22kHz. T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
V
DD
= 1.8V to 3.6V, overall
gain = 6dB
Power-Supply Rejection Ratio
f = 217Hz, 100mV
P-P
ripple,
overall gain = 26dB
f = 1kHz, 100mV
P-P
ripple,
overall gain = 26dB
f = 20kHz, 100mV
P-P
ripple,
overall gain = 26dB
THD+N = 1%,
f
IN
= 1kHz, overall
gain = 1.8dB,
T
A
= +25°C (Note 4)
f
IN
= 1kHz, overall
gain = 3.5dB
(Note 4)
R
L
= 16Ω
R
L
= 32Ω
R
L
= 16Ω,
P
OUT
= 42mW
R
L
= 32Ω,
P
OUT
= 40mW
12
21
MIN
72
TYP
95
90
dB
82
58
49
mW
52
0.04
%
0.04
3.5
6
8
10
19.5
22
24
26
10
20
30
40
50
52
54
56
99
101
0.5
No sustained oscillations
R
OUT_SHDN
V
SHDN
= 0V, measured from OUT_ to
SGND
200
20
dB
V/µs
pF
kΩ
dB
dB
MAX
UNITS
PSRR
(Note 3)
Output Power
P
OUT
Total Harmonic Distortion Plus
Noise
THD+N
Register 0x01, B[2:0] = 000
Register 0x01, B[2:0] = 001
Register 0x01, B[2:0] = 010
Maximum Gain
A
VMAX
Register 0x01, B[2:0] = 011
Register 0x01, B[2:0] = 100
Register 0x01, B[2:0] = 101
Register 0x01, B[2:0] = 110
Register 0x01, B[2:0] = 111
Register 0x01, B[7:5] = 000
Register 0x01, B[7:5] = 001
Register 0x01, B[7:5] = 010
Beep Input Attenuation
A
V_BEEP
Register 0x01, B[7:5] = 011
Register 0x01, B[7:5] = 100
Register 0x01, B[7:5] = 101
Register 0x01, B[7:5] = 110
Register 0x01, B[7:5] = 111
Signal-to-Noise Ratio
Slew Rate
Capacitive Drive
Output Resistance in Shutdown
SNR
SR
R
L
= 32Ω,
V
OUT
= 1V
RMS
BW = 22Hz to 22kHz
BW = 22Hz to 22kHz
and A-weighted
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Maxim Integrated
│
3
MAX9729
Stereo Headphone Amplifier with BassMax,
Volume Control, and Input Mux
Electrical Characteristics (3V Supply)
(continued)
(V
DD
= PV
DD
=
SHDN
= 3V, PGND = SGND = 0V, C1 = C2 = C3 = 1μF, BM_ = 0V, maximum gain setting = 6dB, volume attenuation
setting = -16dB (overall gain = -10dB), BassMax disabled. Load connected between OUT_ and PGND where specified. THD+N mea-
surement BW = 22Hz to 22kHz. T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
Peak voltage,
A-weighted, 32
samples per second
(Notes 3 and 5)
Into shutdown
Out of shutdown
505
L to R, or R to L, f = 10kHz, V
OUT
=
1V
RMS
, R
L
= 32Ω, both channels loaded
V
IH
V
IL
-1
V
OL
I
OH
I
OL
= 3mA
V
SDA
= V
DD
1.4
0.4
+1
0.4
1
MIN
TYP
81
dBV
80
600
78
730
kHz
dB
MAX
UNITS
Click-and-Pop Level
K
CP
Charge-Pump Switching
Frequency
Crosstalk
f
CP
DIGITAL INPUTS (SHDN, SDA, SCL, BEEP_EN)
Input High Voltage
Input Low Voltage
Input Leakage Current
DIGITAL OUTPUTS (SDA)
Output Low Voltage
Output High Current
V
µA
V
V
µA
Electrical Characteristics (2.4V Supply)
(V
DD
= PV
DD
=
SHDN
= 2.4V, PGND = SGND = 0V, C1 = C2 = C3 = 1μF, BM_ = 0V, maximum gain setting = 6dB, volume attenuation
setting = -16dB (overall gain = -10dB), BassMax disabled. Load connected between OUT_ and PGND where specified. THD+N mea-
surement BW = 22Hz to 22kHz. T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Quiescent Current
Shutdown Current
SYMBOL
I
DD
I
SHDN
V
SHDN
= 0V
THD+N = 1%,
f
IN = 1kHz, overall
gain = 3.5dB,
TA
= +25°C
(Note 4)
f
IN
= 1kHz, overall
gain = 3.5dB
(Note 4)
100mVP-P
ripple
(Note 3)
R
L
= 16Ω
R
L
= 32Ω
R
L
= 16Ω,
P
OUT
= 23mW
R
L
= 32Ω,
P
OUT
= 23mW
f = 217Hz
f = 1kHz
f = 10kHz
CONDITIONS
No load (Note 3)
MIN
TYP
4.5
4
32
mW
32
0.03
%
0.03
90
85
61
dB
MAX
UNITS
mA
µA
Output Power
P
OUT
Total Harmonic Distortion Plus
Noise
THD+N
Power-Supply Rejection Ratio
PSRR
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Maxim Integrated
│ 4
MAX9729
Stereo Headphone Amplifier with BassMax,
Volume Control, and Input Mux
Electrical Characteristics (2.4V Supply)
(continued)
(V
DD
= PV
DD
=
SHDN
= 2.4V, PGND = SGND = 0V, C1 = C2 = C3 = 1μF, BM_ = 0V, maximum gain setting = 6dB, volume attenuation
setting = -16dB (overall gain = -10dB), BassMax disabled. Load connected between OUT_ and PGND where specified. THD+N mea-
surement BW = 22Hz to 22kHz. T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
R
L
= 32Ω,
V
OUT
= 1V
RMS
,
overall gain =
3.5dB
Peak voltage,
A-weighted,
32 samples per
second
(Notes 3 and 5)
BW = 22Hz to 22kHz
BW = 22Hz to 22kHz
and A-weighted
Into shutdown
MIN
TYP
98
dB
101
79
dBV
Out of shutdown
79
MAX
UNITS
Signal-to-Noise Ratio
SNR
Click-and-Pop Level
K
CP
Timing Characteristics
(V
DD
= PV
DD
=
SHDN
= 3V, PGND = SGND = 0V, C1 = C2 = C3 = 1μF, BM_ = 0V, maximum gain setting = 6dB, volume setting =
-16dB (overall gain = -10dB), BassMax disabled. Load connected between OUT_ and PGND where specified. T
A
= T
MIN
to T
MAX
,
unless otherwise noted. Typical values are at T
A
= +25°C.) (Notes 1 and 6)
PARAMETER
Serial Clock Frequency
Bus Free Time Between a STOP and a
START Condition
Hold Time Repeated for a START
Condition
Low Period of the SCL Clock
High Period of the SCL Clock
Setup Time for a Repeated START
Condition
Data Hold Time
Data Setup Time
Rise Time of Both SDA and SCL Signals
Fall Time of Both SDA and SCL Signals
Setup Time for STOP Condition
Pulse Width of Suppressed Spike
Capacitive Load for Each Bus Line
Note
Note
Note
Note
Note
1:
2:
3:
4:
5:
SYMBOL
f
SCL
t
BUF
t
HD:STA
t
LOW
t
HIGH
t
SU:STA
t
HD:DAT
t
SU:DAT
t
r
t
f
t
SU:STO
t
SP
C
L_BUS
0.6
50
400
CONDITIONS
MIN
0
1.3
0.6
1.3
0.6
0.6
0
100
300
300
0.9
TYP
MAX
400
UNITS
kHz
µs
µs
µs
µs
µs
µs
ns
ns
ns
µs
ns
pF
All specifications are 100% tested at T
A
= +25°C. Temperature limits are guaranteed by design.
V
DD
and PV
DD
must be connected together.
Inputs AC-coupled to SGND.
Both channels loaded and driven in phase.
Headphone testing performed with a 32Ω resistive load connected to PGND. Mode transitions are controlled by
SHDN.
KCP
level is calculated as 20log[(peak voltage during mode transition, no input signal)/1V
RMS
]. Units are expressed in dBV.
Note 6:
Guaranteed by design.
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│
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