19-3963; Rev 1; 7/09
KIT
ATION
EVALU
BLE
AVAILA
60mW, DirectDrive, Stereo
Headphone Amplifiers with Shutdown
General Description
Features
♦
No Bulky DC-Blocking Capacitors Required
♦
Low-Power Shutdown Mode, < 0.1µA
♦
Adjustable Gain (MAX9728A) or Fixed -1.5V/V
Gain (MAX9728B)
♦
Low 0.02% THD+N
♦
High PSRR (80dB at 1kHz) Eliminates LDO
♦
Integrated Click-and-Pop Suppression
♦
4.5V to 5.5V Single-Supply Operation
♦
Low Quiescent Current (3.5mA)
♦
Available in Space-Saving Packages
12-Pin Thin QFN (3mm x 3mm x 0.8mm)
14-Pin TSSOP (5mm x 4.4mm x 1.1mm)
MAX9728A/MAX9728B
The MAX9728A/MAX9728B stereo headphone ampli-
fiers are designed for display and notebook applica-
tions or portable equipment where board space is at a
premium. These devices use a unique DirectDrive
®
architecture to produce a ground-referenced output
from a single supply, eliminating the need for large DC-
blocking capacitors, saving cost, board space, and
component height. The MAX9728A offers an externally
adjustable gain, while the MAX9728B has an internally
preset gain of -1.5V/V. The MAX9728A/MAX9728B
deliver up to 60mW per channel into a 32Ω load and
have low 0.02% THD+N. An 80dB at 1kHz power-sup-
ply rejection ratio (PSRR) allows these devices to oper-
ate from noisy digital supplies without an additional
linear regulator. Comprehensive click-and-pop circuitry
suppresses audible clicks and pops on startup and
shutdown.
The MAX9728A/MAX9728B operate from a single 4.5V
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-
pin Thin QFN (3mm x 3mm x 0.8mm) and 14-pin
TSSOP packages (5mm x 4.4mm x 1.1mm).
Ordering Information
PART
MAX9728AETC+
MAX9728AEUD+
MAX9728BETC+
MAX9728BEUD+
GAIN (V/V) PIN-PACKAGE
Adj.
Adj.
-1.5
-1.5
12 TQFN-EP*
14 TSSOP
12 TQFN-EP*
14 TSSOP
TOP MARK
ABC
—
ABD
—
Applications
Notebook PCs
DVD Players
LCD/PDP Displays
DirectDrive is a registered trademark of Maxim Integrated
Product, Inc.
CRT TVs
Multimedia Monitors
Note:
All devices specified over the -40°C to +85°C operating
range.
+Denotes
lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed pad.
Pin Configurations appear at end of data sheet.
Block Diagrams
MAX9728B
MAX9728A
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.
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
MAX9728A/MAX9728B
ABSOLUTE MAXIMUM RATINGS
V
DD
to PGND............................................................-0.3V to +6V
PV
SS
to SV
SS
.........................................................-0.3V to +0.3V
PGND to SGND .....................................................-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
and SV
SS
to PGND..........................................-6V to +0.3V
IN_ to SGND (MAX9728A)..........................-0.3V to (V
DD
+ 0.3V)
IN_ to SGND (MAX9728B) .............(SV
SS
- 0.3V) to (V
DD
+ 0.3V)
OUT_ to SV
SS
(Note 1) ....-0.3V to Min (V
DD
- SV
SS
+ 0.3V, +9V)
OUT_ to V
DD
(Note 2) ......+0.3V to Max (SV
SS
- V
DD
- 0.3V, -9V)
SHDN
to _GND.........................................................-0.3V to +6V
OUT_ Short Circuit to SGND ......................................Continuous
Short Circuit between OUTL and OUTR ....................Continuous
Continuous Input Current into PV
SS
..................................260mA
Continuous Input Current (any other pin) .........................±20mA
Continuous Power Dissipation (T
A
= +70°C)
12-Pin TQFN (derate 14.7mW/°C above +70°C) .........1177mW
14-Pin TSSOP (derate 9.1mW/°C above +70°C) ...........727mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature ......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
Note 1:
OUTR and OUTL should be limited to no more than 9V above SV
SS
, 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 SV
SS
- 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 MAX9728A gain = -1.5V/V
(R
IN
= 20kΩ, R
F
= 30kΩ); for MAX9728B 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
V
DD
I
CC
I
SHDN
t
SON
R
IN
V
OS
V
DD
= 4.5V to 5.5V
PSRR
f = 1kHz, 100mV
P-P
f = 20kHz, 100mV
P-P
Output Power
Voltage Gain
Channel-to-Channel Gain
Tracking
Total Harmonic Distortion Plus
Noise
THD+N
P
OUT
A
V
R
L
= 32Ω, THD+N = 1%
R
L
= 16Ω, THD+N = 1%
MAX9728B (Note 4)
MAX9728B
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
-1.52
30
MAX9728B, measured at IN_
15
SHDN
= SGND = PGND
4.5
3.5
< 0.1
180
19
±1.5
86
80
65
63
42
-1.5
±0.15
0.003
0.02
0.04
%
-1.48
mW
V/V
%
dB
25
±10
5.5
5.5
1
V
mA
µA
µs
kΩ
mV
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
60mW, DirectDrive, Stereo Headphone
Amplifier with Shutdown
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= 5V, PGND = SGND,
SHDN
= 5V, C1 = C2 = 1µF, R
L
=
∞,
resistive load reference to ground; for MAX9728A gain = -1.5V/V
(R
IN
= 20kΩ, R
F
= 30kΩ); for MAX9728B 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
SYMBOL
R
L
= 1kΩ,
V
OUT
= 2V
RMS
R
L
= 32Ω,
P
OUT
= 50mW
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
2
0.8
±1
V
V
µA
f
OSC
Into shutdown
R
L
= 32Ω, peak voltage,
A-weighted, 32 samples per Out of
second (Note 5)
shutdown
SR
C
L
No sustained oscillations
L to R, R to L, f = 10kHz, R
L
= 16Ω, P
OUT
=
15mW
190
CONDITIONS
BW = 22Hz to 22kHz
A-weighted
BW = 22Hz to 22kHz
A-weighted
MIN
TYP
102
105
98
101
0.5
100
-70
270
-67
-64
dB
400
V/µs
pF
dB
kHz
dB
MAX
UNITS
MAX9728A/MAX9728B
Signal-to-Noise Ratio
SNR
K
CP
Note 3:
All specifications are 100% tested at T
A
= +25°C; temperature limits are guaranteed by design.
Note 4:
Gain for the MAX9728A is adjustable.
Note 5:
Test performed with a 32Ω resistive load connected to SGND. Mode transitions are controlled by
SHDN.
K
CP
level is calcu-
lated 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
60mW, DirectDrive, Stereo Headphone
Amplifiers with Shutdown
MAX9728A/MAX9728B
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 MAX9728A),
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
MAX9728A/28B toc01
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
MAX9728A/28B toc02
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
V
DD
= 5V
R
L
= 16Ω
P
OUT
= 20mW
0.1
MAX9728A/28B toc03
100
V
DD
= 5V
R
L
= 16Ω
10
100
V
DD
= 5V
R
L
= 32Ω
10
1
THD+N (%)
f
IN
= 1kHz
0.1
f
IN
= 10kHz
0.01
f
IN
= 20Hz
0.1
f
IN
= 1kHz
THD+N (%)
1
THD+N (%)
1
0.01
0.01
f
IN
= 20Hz
0.001
0.001
0
20
40
60
80
100
120
10
100
f
IN
= 10kHz
P
OUT
= 37mW
0.001
0
20
40
60
80
100
OUTPUT POWER (mW)
1k
FREQUENCY (Hz)
10k
100k
OUTPUT POWER (mW)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
MAX9728A/28B toc04
OUTPUT POWER vs. SUPPLY VOLTAGE
MAX9728A/28B toc05
OUTPUT POWER vs. SUPPLY VOLTAGE
MAX9728A/28B toc06
1
V
DD
= 5V
R
L
= 32Ω
70
60
OUTPUT POWER (mW)
50
40
30
20
10
f
IN
= 1kHz
R
L
= 16Ω
4.5
5.0
SUPPLY VOLTAGE (V)
THD+N = 1%
THD+N = 10%
120
100
OUTPUT POWER (mW)
80
60
40
20
0
THD+N = 1%
f
IN
= 1kHz
R
L
= 32Ω
4.5
5.0
SUPPLY VOLTAGE (V)
THD+N = 10%
0.1
THD+N (%)
P
OUT
= 30mW
0.01
P
OUT
= 50mW
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0
5.5
5.5
4
_______________________________________________________________________________________
60mW, DirectDrive, Stereo Headphone
Amplifiers with 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 MAX9728A),
THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, T
A
= +25°C, unless otherwise noted.)
MAX9728A/MAX9728B
OUTPUT POWER
vs. LOAD RESISTANCE
MAX9728A/28B toc07
POWER-SUPPLY REJECTION
RATIO vs. FREQUENCY
MAX9728A/28B toc08
CROSSTALK vs. FREQUENCY
P
OUT
= 15mW
R
L
= 16Ω
MAX9728A/28B toc09
100
90
80
OUTPUT POWER (mW)
70
60
50
40
30
20
10
0
10
100
LOAD RESISTANCE (Ω)
V
DD
= 5V
f
IN
= 1kHz
THD+N = 1%
THD+N = 10%
0
-20
-40
PSRR (dB)
-60
-80
-100
-120
R
L
= 32Ω
V
DD
= 5V
0
-20
CROSSTALK (dB)
-40
-60
-80
-100
-120
RIGHT TO LEFT
LEFT TO RIGHT
1000
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
OUTPUT POWER vs. LOAD RESISTANCE
AND CHARGE-PUMP CAPACITOR SIZE
MAX9728A/28B toc10
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX9728A/28B toc11
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
9
SHUTDOWN CURRENT (nA)
8
7
6
5
4
3
2
MAX9728A/28B toc12
80
C1 = C2 = 2.2μF
70
OUTPUT POWER (mW)
60
50
C1 = C2 = 0.47μF
40
30
20
0
50
250
200
150
LOAD RESISTANCE (Ω)
100
V
DD
= 5V
f
IN
= 1kHz
THD+N = 1%
C1 = C2 = 1μF
3.50
3.45
SUPPLY CURRENT (mA)
3.40
3.35
3.30
3.25
NO LOAD INPUTS GROUND
3.20
10
1
0
5.5
4.5
NO LOAD INPUTS GROUND
5.0
SUPPLY VOLTAGE (V)
5.5
300
4.5
5.0
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5
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