19-0627; Rev 0; 9/06
DirectDrive, Headphone Amplifier with
BassMax, I
2
C, Volume and Gain Control
General Description
The MAX9726 stereo, DirectDrive™, headphone amplifier
with BassMax and volume control is ideal for portable
audio applications where space is at a premium and per-
formance is essential. The MAX9726 operates from a sin-
gle 2.7V to 5.5V power supply and includes features that
reduce external component count, system cost, board
space, and offer improved audio reproduction. High
85dB PSRR makes the MAX9726 ideal for direct connec-
tion to a battery-powered supply and eliminates the need
for a dedicated LDO. The MAX9726 features Maxim’s
industry-leading click-and-pop suppression circuitry,
which reduces/eliminates audible transients during
power-up and power-down.
The headphone amplifier uses Maxim’s patented
†
DirectDrive architecture that produces a ground-refer-
enced output from a single supply, eliminating the need
for large DC-blocking capacitors. The headphone ampli-
fiers deliver 105mW into a 32Ω load and feature low
0.02% THD+N.
The BassMax feature boosts the bass response of the
amplifier, improving audio reproduction when using inex-
pensive headphones. The integrated volume control fea-
tures 64 discrete volume levels, eliminating the need for
an external potentiometer. External resistors set the
MAX9726’s overall gain allowing for custom gain settings.
BassMax and the volume control are enabled through the
I
2
C/SMBus
™
-compatible interface. Shutdown can be con-
trolled through the hardware or software interface.
The MAX9726 consumes only 5.5mA 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 MAX9726 is available in a tiny
(2mm x 2.5mm x 0.62mm) 20-bump chip-scale pack-
age (UCSP™) and a 20-pin TQFN package (4mm x
4mm x 0.75mm).
Features
♦
105mW DirectDrive Headphone Amplifier
Eliminates Bulky DC-Blocking Capacitors
♦
2.7V to 5.5V Single-Supply Operation
♦
Integrated 64-Level Volume Control
♦
High 85dB PSRR at 1kHz
♦
Software-Enabled Bass Boost (BassMax)
♦
Industry-Leading Click-and-Pop Suppression
♦
±7.5kV HBM ESD-Protected Headphone Outputs
♦
Short-Circuit and Thermal-Overload Protection
♦
Low-Power Shutdown Mode (8µA)
♦
Low 0.02% THD+N
♦
I
2
C/SMBus-Compatible Interface
♦
Available in Space-Saving, Thermally Efficient
Packages
20-Bump UCSP (2mm x 2.5mm x 0.62mm)
20-Pin TQFN (4mm x 4mm x 0.75mm)
MAX9726
Ordering Information
PART
MAX9726AEBP+T*
MAX9726AETP+
MAX9726BEBP+T*
MAX9726BETP+
PIN-PACKAGE
20 UCSP-20
20 TQFN-EP**
20 UCSP-20
20 TQFN-EP**
SLAVE
ADDRESS
1001100
1001100
1001101
1001101
PKG
CODE
B20-1
T2044-3
B20-1
T2044-3
Note:
All devices specified over the -40°C to +85°C operating
range.
+Denotes
lead-free package.
*Future
product—contact factory for availability.
**EP
= Exposed pad.
Simplified Block Diagram
2.7V TO 5.5V SUPPLY
Applications
Cell Phones
MP3/PMP Players
Flat-Panel TVs
†
U.S. Patent # 7,061,327
INR
FBR
Automotive Rear-Seat
Entertainment (RSE)
Portable CD/DVD/MD
Players
SCL
SDA
FBL
INL
BML
I
2
C
INTERFACE
BassMax
VOLUME
CONTROL
Σ
Σ
OUTL
OUTR
MAX9726
BMR
BassMax
SMBus is a trademark of Intel Corp.
UCSP is a trademark of Maxim Integrated Products, Inc.
Pin Configurations appear at end of data sheet.
1
________________________________________________________________
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
DirectDrive, Headphone Amplifier with
BassMax, I
2
C, Volume and Gain Control
MAX9726
ABSOLUTE MAXIMUM RATINGS
V
DD
to PGND............................................................-0.3V to +6V
PV
SS
to SV
SS
.........................................................-0.3V to +0.3V
SGND to PGND .....................................................-0.3V to +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 -6V
IN_ to SGND...................................(SV
SS
- 0.3V) to (V
DD
+ 0.3V)
FB_ to SGND..................................(SV
SS
- 0.3V) to (V
DD
+ 0.3V)
SDA, SCL to PGND ....................................-0.3V to (V
DD
+ 0.3V)
SHDN
to PGND ..........................................-0.3V to (V
DD
+ 0.3V)
OUT_ to SGND ............................................................-3V to +3V
BM_ to SGND ..............................................................-3V to +3V
Duration of OUT_ Short Circuit to PGND....................Continuous
Continuous Current Into/Out of:
V
DD
, C1P, PGND, C1N, PV
SS
, SV
SS
, or OUT_ ...........±850mA
Any Other Pin................................................................±20mA
Continuous Power Dissipation (T
A
= +70°C, multilayer board)
20-Bump UCSP (derate 10mW/°C above +70°C) .......800mW
20-Pin TQFN (derate 25.6mW/°C above +70°C) .......2051mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
OUTL and OUTR ESD Protection (Human Body Model)....±7.5kV
Bump Temperature (soldering) Reflow............................+230°C
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 (5V Supply)
(V
DD
=
SHDN
= 5V, PGND = SGND = 0V, C1 = C2 = 1µF, C
PREG
= C
NREG
= 1µF, BM_ = 0V, R
IN
= 10kΩ, R
F
= 10kΩ, maximum vol-
ume (overall gain = 0dB), 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.) (Note 1)
PARAMETER
GENERAL
Supply Voltage Range
Quiescent Supply Current
Shutdown Supply Current
Turn-On Time
Turn-Off Time
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
HEADPHONE AMPLIFIER
Output Offset Voltage
Input Offset Voltage of Input
Amplifier
Input Bias Current
BMR, BML Input Bias Current
Power-Supply Rejection Ratio
(Note 2)
Output Power
Total Harmonic Distortion Plus
Noise
V
OSHP
Measured between OUT_ and SGND, gain
= 0dB, R
IN
= R
F
= 10kΩ, T
A
= +25°C
(Note 2)
Referenced to SGND, measured between
FBR, FBL, and SGND
±0.6
10
mV
V
DD
I
DD
I
DD_SHDN
t
ON
t
OFF
T
THRES
T
HYST
No load
SHDN
= 0V
SYMBOL
CONDITIONS
MIN
2.7
TYP
MAX
5.5
UNITS
V
mA
µA
µs
µs
°C
°C
5.5
8
440
1
+150
12
10
15
V
OS
I
B
I
BIAS_BB
3
±20
±20
±100
±100
mV
nA
nA
dB
DC, V
DD
= 2.7V to 5.5V
PSRR
f = 1kHz, 100mV
P-P
ripple
f = 20kHz, 100mV
P-P
ripple
P
OUT
THD+N
THD+N = 1%, R
L
= 16Ω
f
IN
= 1kHz
R
L
= 32Ω
R
L
= 16Ω, P
OUT
= 15mW, f
IN
= 1kHz
R
L
= 32Ω, P
OUT
= 30mW, f
IN
= 1kHz
80
97
85
74
124
104
0.04
0.02
mW
%
2
_______________________________________________________________________________________
DirectDrive, Headphone Amplifier with
BassMax, I
2
C, Volume and Gain Control
ELECTRICAL CHARACTERISTICS (5V Supply) (continued)
(V
DD
=
SHDN
= 5V, PGND = SGND = 0V, C1 = C2 = 1µF, C
PREG
= C
NREG
= 1µF, BM_ = 0V, R
IN
= 10kΩ, R
F
= 10kΩ, maximum vol-
ume (overall gain = 0dB), 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.) (Note 1)
PARAMETER
Signal-to-Noise Ratio
Slew Rate
Capacitive Drive
Output Resistance in Shutdown
R
OUT_SHDN
SYMBOL
SNR
SR
No sustained oscillations
V
SHDN
= 0V, measured from OUT_ to
SGND
Peak voltage, A-weighted,
32 samples per second
(Notes 2, 4)
Into
shutdown
Out of
shutdown
515
L to R, or R to L, f = 10kHz,
V
OUT
= 1V
P-P
, R
L
= 32Ω, both channels
loaded
R
L
= 32Ω,
V
OUT
=
1.77V
RMS
CONDITIONS
BW = 22Hz to 22kHz
A-weighted
MIN
TYP
102
dB
105
1
200
50
59
dBV
61
610
705
kHz
V/µs
pF
kΩ
MAX
UNITS
MAX9726
Click-and-Pop Level
K
CP
Charge-Pump Switching
Frequency
Crosstalk
VOLUME CONTROL
f
CP
85
dB
0 to 64dB
Attenuator Step Accuracy
DIGITAL INPUTS (SHDN, SDA, SCL)
Input High Voltage
Input Low Voltage
Input Leakage Current
DIGITAL OUTPUTS (SDA)
Output Low Voltage
Output High Current
V
OL
I
OH
I
OL
= 3mA
V
SDA
= V
DD
V
IH
V
IL
0.7 x
V
DD
68dB to 96dB
100dB to 120dB
±0.1
±0.5
±2
dB
V
0.3 x
V
DD
±1
0.06
1
V
µA
V
µA
ELECTRICAL CHARACTERISTICS (3.3V Supply)
(V
DD
=
SHDN
= 3.3V, PGND = SGND = 0V, C1 = C2 = 1µF, C
PREG
= C
NREG
= 1µF, BM_ = 0V, R
IN
= 10kΩ, R
F
= 10kΩ, maximum
volume (overall gain = 0dB), 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.) (Note 1)
PARAMETER
Output Power
Total Harmonic Distortion Plus
Noise
SYMBOL
P
OUT
THD+N
THD+N = 1%,
f
IN
= 1kHz
CONDITIONS
R
L
= 16Ω
R
L
= 32Ω
MIN
TYP
80
70
0.05
0.03
MAX
UNITS
mW
%
R
L
= 16Ω, P
OUT
= 15mW, f
IN
= 1kHz
R
L
= 32Ω, P
OUT
= 30mW, f
IN
= 1kHz
_______________________________________________________________________________________
3
DirectDrive, Headphone Amplifier with
BassMax, I
2
C, Volume and Gain Control
MAX9726
ELECTRICAL CHARACTERISTICS (3.3V Supply) (continued)
(V
DD
=
SHDN
= 3.3V, PGND = SGND = 0V, C1 = C2 = 1µF, C
PREG
= C
NREG
= 1µF, BM_ = 0V, R
IN
= 10kΩ, R
F
= 10kΩ, maximum
volume (overall gain = 0dB), 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.) (Note 1)
PARAMETER
Power-Supply Rejection Ratio
(Note 2)
Signal-to-Noise Ratio
SYMBOL
PSRR
SNR
CONDITIONS
f = 1kHz, 100mV
P-P
ripple
f = 20kHz, 100mV
P-P
ripple
R
L
= 32Ω,
V
OUT
= 1.5V
RMS
Peak voltage,
A-weighted, 32
samples per
second
(Notes 2, 4)
BW = 22Hz to 22kHz
A-weighted
Into shutdown
MIN
TYP
85
73
101
104
62
dBV
Out of shutdown
67
MAX
UNITS
dB
dB
Click-and-Pop Level
K
CP
TIMING CHARACTERISTICS
(V
DD
=
SHDN
= 5V, PGND = SGND = 0V, C1 = C2 = 1µF, C
PREG
= C
NREG
= 1µF, BM_ = 0V, R
IN
= 10kΩ, R
F
= 10kΩ, maximum vol-
ume (overall gain = 0dB), 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, 3)
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
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
Note 1:
Note 2:
Note 3:
Note 4:
All specifications are 100% tested at T
A
= +25°C. Temperature limits are guaranteed by design.
Inputs AC-coupled to SGND.
Guaranteed by design.
Headphone testing performed with a 32Ω resistive load connected to PGND. Mode transitions are controlled by
SHDN.
K
CP
level is calculated as 20log[(peak voltage during mode transition, no input signal)/1V
RMS
]. Units are expressed in dBV.
4
_______________________________________________________________________________________
DirectDrive, Headphone Amplifier with
BassMax, I
2
C, Volume and Gain Control
MAX9726
Typical Operating Characteristics
(V
DD
=
SHDN
= 5V, PGND = SGND = 0V, C1 = C2 = 1µF, C
PREG
= C
NREG
= 1µF, BM_ = 0V, R
IN
= 10kΩ, R
F
= 10kΩ, maximum vol-
ume (overall gain = 0dB), BassMax disabled. Load connected between OUT_ and PGND where specified. Outputs in phase, both
channels loaded. T
A
= +25°C, unless otherwise noted.) (See the
Functional Diagram/Typical Operating Circuit)
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9726 toc01
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9726 toc02
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
V
DD
= 5V
R
L
= 16Ω
MAX9726 toc03
100
V
DD
= 3.3V
R
L
= 16Ω
100
V
DD
= 3.3V
R
L
= 32Ω
f
IN
= 1kHz
THD+N (%)
100
f
IN
= 1kHz
10
10
10
THD+N (%)
THD+N (%)
1
f
IN
= 20Hz
f
IN
= 1kHz
1
f
IN
= 20Hz
1
f
IN
= 20Hz
0.1
f
IN
= 10kHz
0.1
f
IN
= 10kHz
0.1
f
IN
= 10kHz
0.01
0.01
0.01
0.001
0
20
40 60 80 100 120 140 160
OUTPUT POWER (mW)
0.001
0
20
40 60 80 100 120 140 160
OUTPUT POWER (mW)
0.001
0
20 40 60 80 100 120 140 160 180 200
OUTPUT POWER (mW)
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9726 toc04
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
V
DD
= 3.3V
R
L
= 16Ω
1
OUTPUT POWER = 60mW
THD+N (%)
MAX9726 toc05
100
V
DD
= 5V
R
L
= 32Ω
10
f
IN
= 1kHz
10
THD+N (%)
1
f
IN
= 20Hz
0.1
f
IN
= 10kHz
0.01
0.1
0.01
OUTPUT POWER = 20mW
0.001
0
20
40 60 80 100 120 140 160
OUTPUT POWER (mW)
0.001
10
100
1k
10k
FREQUENCY (Hz)
100k
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX9726 toc06
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
V
DD
= 5V
R
L
= 16Ω
1
THD+N (%)
MAX9726 toc07
10
V
DD
= 3.3V
R
L
= 32Ω
1
THD+N (%)
OUTPUT POWER = 20mW
0.1
10
OUTPUT POWER = 80mW
0.1
0.01
OUTPUT POWER = 60mW
0.001
10
100
1k
10k
FREQUENCY (Hz)
100k
0.01
OUTPUT POWER = 40mW
0.001
10
100
1k
10k
FREQUENCY (Hz)
100k
_______________________________________________________________________________________
5
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