19-4130; Rev 0; 5/08
Low RF Susceptibility DirectDrive Stereo Head-
phone Amplifier with 1.8V Compatible Shutdown
General Description
The MAX9724C/MAX9724D stereo headphone ampli-
fiers are designed for portable equipment where board
space is at a premium. These devices use a unique,
DirectDrive
®
architecture to produce a ground-refer-
enced output from a single supply, eliminating the need
for large DC-blocking capacitors, saving cost, board
space, and component height. The MAX9724 sup-
presses RF radiation received by input and supply
traces acting as antennas and prevents the amplifier
from demodulating the coupled noise. The MAX9724C
offers an externally adjustable gain while the
MAX9724D has an internally preset gain of -1.5V/V. The
MAX9724C/MAX9724D deliver up to 60mW per channel
into a 32Ω load and have low 0.02% THD+N. An 80dB
at 1kHz power-supply rejection ratio (PSRR) allows
these devices to operate from noisy digital supplies
without an additional linear regulator. Comprehensive
click-and-pop circuitry suppresses audible clicks and
pops on startup and shutdown.
The MAX9724C/MAX9724D operate from a single 2.5V
to 5.5V supply, consume only 3.5mA of supply current,
feature short-circuit and thermal-overload protection,
and are specified over the extended -40°C to +85°C
temperature range. The devices are available in tiny
12-bump UCSP™ (1.5mm x 2mm) and 12-pin thin QFN
(3mm x 3mm x 0.8mm) packages.
Features
♦
Improved RF Noise Rejection (Up to 67dB Over
Typical Amplifiers)
♦
No Bulky DC-Blocking Capacitors Required
♦
Low-Power Shutdown Mode, < 0.1µA
♦
Adjustable Gain (MAX9724C) or Fixed -1.5V/V
Gain (MAX9724D)
♦
Low 0.02% THD+N
♦
High PSRR (80dB at 1kHz) Eliminates LDO
♦
Integrated Click-and-Pop Suppression
♦
2.5V to 5.5V Single-Supply Operation
♦
Low Quiescent Current (3.5mA)
♦
Available in Space-Saving Packages
12-Bump UCSP (1.5mm x 2mm)
12-Pin Thin QFN (3mm x 3mm x 0.8mm)
MAX9724C/MAX9724D
Ordering Information
PART
MAX9724CEBC+T
MAX9724CETC+
MAX9724DEBC+T
MAX9724DETC+
GAIN (V/V)
Adj.
Adj.
-1.5
-1.5
PIN-PACKAGE
12 UCSP
12 TQFN-EP*
12 UCSP
12 TQFN-EP*
TOP
MARK
+AGE
+ABJ
+AEH
+ABK
Applications
Cellular Phones
MP3 Players
Notebook PCs
Handheld Gaming Consoles
DVD Players
Smart Phones
PDAs
Note:
All devices specified over the -40°C to +85°C operating
range.
+Denotes
a lead-free package.
T = Tape and reel.
*EP
= Exposed pad.
DirectDrive is a registered trademark of
Maxim Integrated Products, Inc.
UCSP is a trademark of Maxim Integrated Products, Inc.
Pin Configurations appear at end of data sheet.
Block Diagrams
MAX9724D
MAX9724C
LEFT
AUDIO
INPUT
DirectDrive OUTPUTS
ELIMINATE DC-BLOCKING
CAPACITORS
LEFT
AUDIO
INPUT
DirectDrive OUTPUTS
ELIMINATE DC-BLOCKING
CAPACITORS
SHDN
SHDN
RIGHT
AUDIO
INPUT
RIGHT
AUDIO
INPUT
FIXED GAIN ELIMINATES
EXTERNAL RESISTOR
NETWORK
________________________________________________________________
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.
Low RF Susceptibility DirectDrive Stereo Head-
phone Amplifier with 1.8V Compatible Shutdown
MAX9724C/MAX9724D
ABSOLUTE MAXIMUM RATINGS
V
DD
to GND ..............................................................-0.3V to +6V
Continuous Input Current into PVSS .................................260mA
PVSS to SVSS ........................................................-0.3V to +0.3V
Continuous Input Current (any other pin) .........................±20mA
PGND to SGND .....................................................-0.3V to +0.3V
Continuous Power Dissipation (T
A
= +70°C, multilayer board)
12-Bump UCSP (derate 6.5mW/°C above +70°C) ........519mW
C1P to PGND..............................................-0.3V to (V
DD
+ 0.3V)
C1N to PGND ...........................................(PVSS - 0.3V) to +0.3V
θ
JA
................................................................................154 C/W
12-Pin TQFN (derate 16.7mW/°C above +70°C) .........1333mW
PVSS and SVSS to PGND.........................................-6V to +0.3V
θ
JA
..................................................................................60°C/W
IN_ to SGND (MAX9724C) .........................-0.3V to (V
DD
+ 0.3V)
IN_ to SGND (MAX9724D) ............(SVSS - 0.3V) to (V
DD
+ 0.3V)
θ
JC
..................................................................................11°C/W
OUT_ to SVSS (Note 1) ...-0.3V to Min (V
DD
- SVSS + 0.3V, +9V)
Operating Temperature Range ...........................-40°C to +85°C
OUT_ to V
DD
(Note 2) .....+0.3V to Max (SVSS - V
DD
- 0.3V, -9V)
Storage Temperature Range .............................-65°C to +150°C
SHDN
to _GND.........................................................-0.3V to +6V
Junction Temperature ......................................................+150°C
OUT_ Short Circuit to GND ........................................Continuous
Lead Temperature (soldering, 10s) .................................+300°C
Short Circuit between OUTL and OUTR ....................Continuous
Bump Temperature (soldering) Reflow............................+235°C
Note 1:
OUTR and OUTL should be limited to no more than 9V above SVSS, or above V
DD
+ 0.3V, whichever limits first.
Note 2:
OUTR and OUTL should be limited to no more than 9V below V
DD
, or below SVSS - 0.3V, whichever limits first.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
DD
= 5V,
PGND = SGND,
SHDN
= 5V, C1 = C2 = 1µF, R
L
=
∞,
resistive load reference to ground; for MAX9724C gain = -1.5V/V
(R
IN
= 20kΩ, R
F
= 30kΩ); for MAX9724D gain = -1.5V/V (internally set), T
A
= -40°C to +85°C, unless otherwise noted. Typical values
are at T
A
= +25°C, unless otherwise noted.) (Note 3)
PARAMETER
GENERAL
Supply Voltage Range
Quiescent Current
Shutdown Current
Shutdown to Full Operation
Input Impedance
Output Offset Voltage
Power-Supply Rejection Ratio
SYMBOL
V
DD
I
CC
I
SHDN
t
SON
R
IN
V
OS
PSRR
SHDN
= SGND = PGND
MAX9724D, measured at IN_
T
A
= +25°C (Note 4)
V
DD
= 2.7V to 5.5V, T
A
= +25°C
f = 1kHz, 100mV
P-P
(Note 4)
f = 20kHz, 100mV
P-P
(Note 4)
Output Power (TQFN)
Output Power (UCSP)
Voltage Gain
Channel-to-Channel Gain Tracking
Total Harmonic Distortion Plus
Noise (TQFN) (Note 6)
Total Harmonic Distortion Plus
Noise (UCSP) (Note 6)
THD+N
P
OUT
P
OUT
A
V
R
L
= 32Ω, THD+N = 1%
R
L
= 16Ω, THD+N = 1%
R
L
= 32Ω, THD+N = 1%
R
L
= 16Ω, THD+N = 1%
MAX9724D (Note 5)
MAX9724D
R
L
= 1kΩ, V
OUT
= 2V
RMS
, f
IN
= 1kHz
R
L
= 32Ω, P
OUT
= 50mW, f
IN
= 1kHz
R
L
= 16Ω, P
OUT
= 35mW, f
IN
= 1kHz
R
L
= 1kΩ, V
OUT
= 2V
RMS
, f
IN
= 1kHz
THD+N
R
L
= 32Ω, P
OUT
= 45mW, f
IN
= 1kHz
R
L
= 16Ω, P
OUT
= 32mW, f
IN
= 1kHz
R
L
= 1kΩ,
V
OUT
= 2V
RMS
R
L
= 32Ω,
P
OUT
= 50mW
BW = 22Hz to 22kHz
A-weighted
BW = 22Hz to 22kHz
A-weighted
-1.52
30
25
69
12
CONDITIONS
MIN
2.5
3.5
0.1
180
19
±1.5
86
80
65
63
42
45
35
-1.5
±0.15
0.003
0.02
0.04
0.003
0.03
0.05
102
105
98
101
%
%
-1.48
mW
mW
V/V
%
TYP
MAX
5.5
5.5
1
28
±10
UNITS
V
mA
µA
µs
kΩ
mV
dB
Signal-to-Noise Ratio
SNR
dB
2
_______________________________________________________________________________________
Low RF Susceptibility DirectDrive Stereo Head-
phone Amplifier with 1.8V Compatible Shutdown
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= 5V,
PGND = SGND,
SHDN
= 5V, C1 = C2 = 1µF, R
L
=
∞,
resistive load reference to ground; for MAX9724C gain = -1.5V/V
(R
IN
= 20kΩ, R
F
= 30kΩ); for MAX9724D gain = -1.5V/V (internally set), T
A
= -40°C to +85°C, unless otherwise noted. Typical values
are at T
A
= +25°C, unless otherwise noted.) (Note 3)
PARAMETER
Slew Rate
Capacitive Drive
Crosstalk
Charge-Pump Oscillator
Frequency
Click-and-Pop Level
DIGITAL INPUTS (SHDN)
Input-Voltage High
Input-Voltage Low
Input Leakage Current
V
INH
V
INL
1.4
0.4
±1
V
V
µA
f
OSC
Into shutdown
R
L
= 32Ω, peak voltage,
A-weighted, 32 samples per Out of
second (Notes 4, 7)
shutdown
SYMBOL
SR
C
L
No sustained oscillations
L to R, R to L, f = 10kHz, R
L
= 16Ω,
P
OUT
= 15mW
190
CONDITIONS
MIN
TYP
0.5
100
-70
270
-67
-64
dB
400
MAX
UNITS
V/µs
pF
dB
kHz
MAX9724C/MAX9724D
K
CP
ELECTRICAL CHARACTERISTICS
(V
DD
= 3V,
PGND = SGND,
SHDN
= 3V, C1 = C2 = 1µF, R
L
=
∞,
resistive load reference to ground; for MAX9724C gain = -1.5V/V
(R
IN
= 20kΩ, R
F
= 30kΩ); for MAX9724D gain = -1.5V/V (internally set), T
A
= -40°C to +85°C, unless otherwise noted. Typical values
are at T
A
= +25°C, unless otherwise noted.) (Note 3)
PARAMETER
Quiescent Current
Shutdown Current
Power-Supply Rejection Ratio
(Note 4)
Output Power (TQFN)
Output Power (UCSP)
Total Harmonic Distortion Plus
Noise (TQFN) (Note 6)
SYMBOL
I
CC
I
SHDN
PSRR
P
OUT
P
OUT
SHDN
= SGND = PGND
f = 1kHz, 100mV
P-P
f = 20kHz, 100mV
P-P
R
L
= 32Ω, THD+N = 1%
R
L
= 16Ω, THD+N = 1%
R
L
= 32Ω, THD+N = 1%
R
L
= 16Ω, THD+N = 1%
R
L
= 1kΩ, V
OUT
= 2V
RMS
, f
IN
= 1kHz
THD+N
R
L
= 32Ω, P
OUT
= 15mW, f
IN
= 1kHz
R
L
= 16Ω, P
OUT
= 10mW, f
IN
= 1kHz
Total Harmonic Distortion Plus
Noise (UCSP) (Note 6)
R
L
= 1kΩ, V
OUT
= 2V
RMS
, f
IN
= 1kHz
THD+N
R
L
= 32Ω, P
OUT
= 15mW, f
IN
= 1kHz
R
L
= 16Ω, P
OUT
= 10mW, f
IN
= 1kHz
CONDITIONS
MIN
TYP
3.0
0.1
80
65
20
14
17
12
0.05
0.03
0.06
0.003
0.04
0.06
%
%
MAX
UNITS
mA
µA
dB
mW
mW
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
All specifications are 100% tested at T
A
= +25°C; temperature limits are guaranteed by design.
The amplifier inputs are AC-coupled to GND.
Gain for the MAX9724C is adjustable.
Measurement bandwidth is 22Hz to 22kHz.
Test performed with a 32Ω resistive load connected to GND. Mode transitions are controlled by
SHDN.
K
CP
level is calculated
as 20log[(peak voltage during mode transition, no input signal)/(peak voltage under normal operation at rated power level)].
Units are expressed in dB.
_______________________________________________________________________________________
3
Low RF Susceptibility DirectDrive Stereo Head-
phone Amplifier with 1.8V Compatible Shutdown
MAX9724C/MAX9724D
Typical Operating Characteristics
(V
DD
= 5V, PGND = SGND = 0V,
SHDN
= V
DD
, C1 = C2 = 1µF, R
L
=
∞,
gain = -1.5V/V (R
IN
= 20kΩ, R
F
= 30kΩ for the MAX9724C),
THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, T
A
= +25°C, unless otherwise noted.)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (TQFN)
MAX9724 toc01
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (UCSP)
V
DD
= 3V
R
L
= 16Ω
1
MAX9724 toc02
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (TQFN)
V
DD
= 3V
R
L
= 32Ω
10
MAX9724toc03
100
V
DD
= 3V
R
L
= 16Ω
10
10
100
THD+N (%)
THD+N (%)
THD+N (%)
1
f
IN
= 1kHz
0.1
f
IN
= 10kHz
1
f
IN
= 1kHz
0.1
f
IN
= 10kHz
0.01
0.1
0.01
0.01
f
IN
= 20Hz
0.001
0
10
20
30
40
OUTPUT POWER (mW)
0.001
0
f
IN
= 10kHz
f
IN
= 1kHz
f
IN
= 20Hz
0.001
5
10
15
20
25
30
0
OUTPUT POWER (mW)
f
IN
= 20Hz
10
20
30
40
50
OUTPUT POWER (mW)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (USCP)
MAX9724toc04
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (TQFN)
MAX9724 toc05
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (UCSP)
V
DD
= 5V
R
L
= 16Ω
1
MAX9724 toc06
10
V
DD
= 3V
R
L
= 32Ω
1
THD+N (%)
100
V
DD
= 5V
R
L
= 16Ω
10
10
THD+N (%)
1
f
IN
= 1kHz
0.1
f
IN
= 10kHz
0.1
THD+N (%)
f
IN
= 1kHz
0.1
0.01
f
IN
= 1kHz
0.001
0
5
10
f
IN
= 20Hz
15
20
f
IN
= 10kHz
0.01
f
IN
= 20Hz
0.001
0.01
f
IN
= 20Hz
0.001
f
IN
= 10kHz
25
30
35
40
0
20
40
60
80
100
0
10
20
30
40
50
60
70
80
OUTPUT POWER (mW)
OUTPUT POWER (mW)
OUTPUT POWER (mW)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (TQFN)
MAX9724 toc07
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER (UCSP)
MAX9724 toc08
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (TQFN)
V
DD
= 3V
R
L
= 16Ω
MAX9724 toc09
100
V
DD
= 5V
R
L
= 32Ω
10
10
V
DD
= 5V
R
L
= 32Ω
1
1
THD+N (%)
f
IN
= 1kHz
0.1
0.1
f
IN
= 1kHz
THD+N (%)
1
THD+N (%)
0.1
P
OUT
= 5mW
0.01
0.01
0.01
f
IN
= 20Hz
0.001
0
20
40
60
80
100
120
OUTPUT POWER (mW)
0.001
0
25
50
75
100
OUTPUT POWER (mW)
f
IN
= 10kHz
f
IN
= 20Hz
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
f
IN
= 10kHz
P
OUT
= 10mW
4
_______________________________________________________________________________________
Low RF Susceptibility DirectDrive Stereo Head-
phone Amplifier with 1.8V Compatible Shutdown
Typical Operating Characteristics (continued)
(V
DD
= 5V, PGND = SGND = 0V,
SHDN
= V
DD
, C1 = C2 = 1µF, R
L
=
∞,
gain = -1.5V/V (R
IN
= 20kΩ, R
F
= 30kΩ for the MAX9724C),
THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, T
A
= +25°C, unless otherwise noted.)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (UCSP)
MAX9724 toc10
MAX9724C/MAX9724D
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (TQFN)
MAX9724 toc11
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (UCSP)
V
DD
= 3V
R
L
= 32Ω
MAX9724 toc12
1
1
V
DD
= 3V
R
L
= 32Ω
1
V
DD
= 3V
R
L
= 16Ω
P
OUT
= 5mW
0.1
THD+N (%)
THD+N (%)
0.1
THD+N (%)
P
OUT
= 8mW
0.01
P
OUT
= 15mW
0.1
P
OUT
= 8mW
P
OUT
= 10mW
0.01
0.01
P
OUT
= 13mW
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (TQFN)
MAX9724 toc13
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (UCSP)
V
DD
= 5V
R
L
= 16Ω
MAX9724 toc14
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (TQFN)
V
DD
= 5V
R
L
= 32Ω
MAX9724 toc15
1
V
DD
= 5V
R
L
= 16Ω
P
OUT
= 20mW
1
1
0.1
THD+N (%)
THD+N (%)
0.1
THD+N (%)
P
OUT
= 20mW
0.1
P
OUT
= 30mW
0.01
P
OUT
= 37mW
0.01
P
OUT
= 32mW
0.01
P
OUT
= 50mW
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY (UCSP)
MAX9724 toc16
OUTPUT POWER vs. SUPPLY
VOLTAGE (TQFN)
MAX9724 toc17
OUTPUT POWER vs. SUPPLY
VOLTAGE (UCSP)
f
IN
= 1kHz
R
L
= 16Ω
MAX9724 toc18
1
V
DD
= 5V
R
L
= 32Ω
60
50
OUTPUT POWER (mW)
40
30
20
10
0
f
IN
= 1kHz
R
L
= 16Ω
70
60
OUTPUT POWER (mW)
50
10% THD+N
40
30
20
10
0
1% THD+N
0.1
THD+N (%)
10% THD+N
P
OUT
= 20mW
0.01
P
OUT
= 45mW
1% THD+N
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5
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