19-3465; Rev 4; 3/09
KIT
ATION
EVALU
E
BL
AVAILA
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
General Description
The MAX9725A–MAX9725D fixed-gain, stereo head-
phone amplifiers are ideal for portable equipment where
board space is at a premium. The MAX9725E offers the
flexibility to adjust the gain with external input and feed-
back resistors. The MAX9725A–MAX9725E 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. Fixed gains of -2V/V (MAX9725A),
-1.5V/V (MAX9725B), -1V/V (MAX9725C), and -4V/V
(MAX9725D) further reduce external component count.
The adjustable gain of the MAX9725E DirectDrive head-
phone amplifier allows for any gain down to -1V/V using
external resistors.
The MAX9725 delivers up to 20mW per channel into a
32Ω load and achieves 0.006% THD+N. An 80dB at 1kHz
power-supply rejection ratio (PSRR) allows the MAX9725
to operate from noisy digital supplies without an additional
linear regulator. The MAX9725 includes
±8kV
ESD protec-
tion on the headphone output. Comprehensive click-and-
pop circuitry suppresses audible clicks and pops at
startup and shutdown. A low-power shutdown mode
reduces supply current to 0.6µA (typ).
The MAX9725 operates from a single 0.9V to 1.8V supply,
allowing the device to be powered directly from a single
AA or AAA battery. The MAX9725 consumes only
2.1mA of supply current, provides short-circuit protection,
and is specified over the extended -40°C to +85°C tem-
perature range. The MAX9725 is available in a tiny
(1.54mm x 2.02mm x 0.6mm) 12-bump chip-scale
package (UCSP™) and a 12-pin thin QFN package
(4mm x 4mm x 0.8mm).
Features
♦
Low Quiescent Current
2.1mA (MAX9725A–MAX9725D)
2.3mA (MAX9725E)
♦
Single-Cell, 0.9V to 1.8V Single-Supply Operation
♦
Fixed Gain Eliminates External Feedback Network
MAX9725A: -2V/V
MAX9725B: -1.5V/V
MAX9725C: -1V/V
MAX9725D: -4V/V
♦
Adjustable Gain with External Input and Feedback
Resistors
MAX9725E: Minimum Stable Gain of -1V/V
♦
Ground-Referenced Outputs Eliminate DC Bias
♦
No Degradation of Low-Frequency Response Due
to Output Capacitors
♦
20mW per Channel into 32Ω
♦
Low 0.006% THD+N
♦
High PSRR (80dB at 1kHz)
♦
Integrated Click-and-Pop Suppression
♦
Low-Power Shutdown Control
♦
Short-Circuit Protection
♦
±8kV
ESD-Protected Amplifier Outputs
♦
Available in Space-Saving Packages
12-Bump UCSP (1.54mm x 2.02mm x 0.6mm)
12-Pin Thin QFN (4mm x 4mm x 0.8mm)
MAX9725
Block Diagrams
V
DD
C3
SINGLE
1.5V CELL
AA OR AAA
BATTERY
Applications
MP3 Players
Cellular Phones
PDAs
Smart Phones
Portable Audio Equipment
INL
MAX9725A–MAX9725D
DirectDrive OUTPUTS
ELIMINATE DC-BLOCKING
CAPACITORS.
OUTL
Ordering Information
C1P
PART
MAX9725AEBC+TG45
MAX9725AETC+
PIN-PACKAGE
12 UCSP
12 TQFN-EP*
TOP
MARK
+ACK
+AAEW
GAIN
(V/V)
-2
-2
INVERTING
CHARGE PUMP
C1N
PV
SS
C2
V
SS
MAX9725BEBC+TG45
12 UCSP
+ACL
-1.5
Ordering Information continued at end of data sheet.
Note:
All devices are specified over the -40°C to +85°C operating
temperature range.
+Denotes
a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
*EP
= Exposed pad.
UCSP is a trademark of Maxim Integrated Products, Inc.
INR
OUTR
SGND
PGND
Block Diagrams continued at end of data sheet.
Pin Configurations appear at end of data sheet.
________________________________________________________________
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.
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
MAX9725
ABSOLUTE MAXIMUM RATINGS
SGND to PGND .....................................................-0.3V to +0.3V
V
DD
to SGND or PGND ............................................-0.3V to +2V
V
SS
to PV
SS
...........................................................-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
V
SS
, PV
SS
to GND ....................................................+0.3V to -2V
OUTR, OUTL, INR, INL to SGND
(MAX9725A–MAX9725D)..............(V
SS
- 0.3V) to (V
DD
+ 0.3V)
OUTR, OUTL to SGND
(MAX9725E) ..................................(V
SS
- 0.3V) to (V
DD
+ 0.3V)
INR, INL to SGND (MAX9725E)...................................-4V to +4V
SHDN
to SGND or PGND .........................................-0.3V to +4V
Output Short-Circuit Current ......................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
12-Bump UCSP (derate 6.5mW/°C above +70°C)....518.8mW
12-Pin Thin QFN (derate 16.9mW/°C above +70°C) ..1349.1mW
Junction Temperature ......................................................+150°C
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
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 (MAX9725A–MAX9725D)
(V
DD
= 1.5V, V
PGND
= V
SGND
= 0V, V
SHDN
= 1.5V, V
SS
= V
PVSS
, C1 = C2 = 1µF, C
IN
= 1µF, R
L
=
∞,
T
A
= T
MIN
to T
MAX,
unless other-
wise noted. Typical values are at T
A
= +25°C.) (See the
Functional Diagrams.)
(Note 1)
PARAMETER
Supply Voltage Range
Quiescent Supply Current
Shutdown Current
Shutdown to Full Operation
SHDN
Thresholds
SHDN
Input Leakage Current
CHARGE PUMP
Oscillator Frequency
AMPLIFIERS
MAX9725A
Voltage Gain
A
V
MAX9725B
MAX9725C
MAX9725D
Gain Match
Total Output Offset Voltage
Input Resistance
Power-Supply Rejection Ratio
ΔA
V
V
OS
R
IN
PSRR
V
DD
= 0.9V to 1.8V, T
A
= +25°C
f
IN
= 1kHz
100mV
P-P
ripple
f
IN
= 20kHz
V
DD
= 1.5V
Output Power (Note 3)
P
OUT
V
DD
= 1.0V, R
L
= 32Ω
V
DD
= 0.9V, R
L
= 32Ω
R
L
= 32Ω
R
L
= 16Ω
Input AC-coupled,
R
L
= 32Ω to GND,
T
A
= +25°C
MAX9725A/MAX9725D
MAX9725B
MAX9725C
15
60
-2.04
-1.53
-1.02
-4.08
-2.00
-1.5
-1.00
-4.00
±0.5
±0.3
±0.45
±0.6
25
80
70
62
10
20
25
7
6
mW
±1.05
±1.58
±2.1
35
kΩ
dB
-1.96
-1.47
-0.98
-3.92
%
mV
V/V
SYMBOL
V
DD
I
DD
I
SHDN
t
ON
V
IH
V
IL
I
LEAK
f
OSC
CONDITIONS
Guaranteed by PSRR test
Both channels active
V
SHDN
= 0V
T
A
= +25°C
T
A
= -40°C to +85°C
180
V
DD
= 0.9V to 1.8V
V
DD
= 0.9V to 1.8V
V
DD
= 0.9V to 1.8V (Note 2)
493
580
0.7 x V
DD
0.3 x V
DD
±1
667
MIN
0.9
2.1
0.6
TYP
MAX
1.8
3.3
10
30
UNITS
V
mA
µA
µs
V
µA
kHz
2
_______________________________________________________________________________________
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
ELECTRICAL CHARACTERISTICS (MAX9725A–MAX9725D) (continued)
(V
DD
= 1.5V, V
PGND
= V
SGND
= 0V, V
SHDN
= 1.5V, V
SS
= V
PVSS
, C1 = C2 = 1µF, C
IN
= 1µF, R
L
=
∞,
T
A
= T
MIN
to T
MAX,
unless other-
wise noted. Typical values are at T
A
= +25°C.) (See the
Functional Diagrams.)
(Note 1)
PARAMETER
Total Harmonic Distortion Plus
Noise
Signal-to-Noise Ratio
Slew Rate
Maximum Capacitive Load
Crosstalk
Click-and-Pop Level
ESD Protection
SYMBOL
THD+N
SNR
SR
C
L
XTALK
K
CP
V
ESD
No sustained oscillations
f
IN
= 1.0kHz, R
L
= 32Ω, P
OUT
= 5mW
R
L
= 32Ω, peak voltage,
A-weighted, 32 samples per
second (Note 4)
Into shutdown
Out of shutdown
CONDITIONS
R
L
= 32Ω, P
OUT
= 12mW, f = 1kHz
R
L
= 16Ω, P
OUT
= 15mW, f = 1kHz
BW = 22Hz to 22kHz
R
L
= 32Ω, P
OUT
= 12mW
A-weighted filter
MIN
TYP
0.006
0.015
89
92
0.2
150
100
72.8
dBV
72.8
±8
kV
MAX
UNITS
%
dB
V/µs
pF
dB
MAX9725
Human Body Model (OUTR, OUTL)
ELECTRICAL CHARACTERISTICS (MAX9725E)
(V
DD
= 1.5V, V
PGND
= V
SGND
= 0V, V
SHDN
= 1.5V, V
SS
= V
PVSS
, C1 = C2 = 1µF, C
IN
= 1µF, R
L
= 32Ω, R
F
= 60kΩ, R
IN
= 10kΩ, T
A
=
T
MIN
to T
MAX,
unless otherwise noted. Typical values are at T
A
= +25°C.) (See the
Functional Diagrams.)
(Note 1)
PARAMETER
Supply Voltage Range
Quiescent Supply Current
Shutdown Current
Shutdown to Full Operation
SHDN
Thresholds
SHDN
Input Leakage Current
CHARGE PUMP
Oscillator Frequency
AMPLIFIERS
Voltage Gain
Minimum Stable Gain
Total Output Offset Voltage
Input Resistance
INR, INL Input Leakage
Current
Maximum Input Parasitic
Capacitance
Power-Supply Rejection Ratio
A
V
ΔA
V
V
OS
R
IN
I
LK
C
PAR
V
DD
= 0.9V to 1.8V, T
A
= +25°C
PSRR
100mV
P-P
ripple
(Note 5)
f
IN
= 1kHz
f
IN
= 20kHz
52.9
5
67.8
70
62
dB
Input AC-coupled, R
L
= 32Ω to GND,
T
A
= +25°C (Note 6)
6.3
(Note 5)
-6.11
-6.07
-1.0
±0.63
9.78
±2.1
14
±100
-6.00
V/V
V/V
mV
kΩ
nA
pF
SYMBOL
V
DD
I
DD
I
SHDN
t
ON
V
IH
V
IL
I
LEAK
f
OSC
CONDITIONS
Guaranteed by PSRR test
Both channels active
V
SHDN
= 0V
T
A
= +25°C
T
A
= -40°C to +85°C
180
V
DD
= 0.9V to 1.8V
V
DD
= 0.9V to 1.8V
V
DD
= 0.9V to 1.8V (Note 2)
483
592
0.7 x V
DD
0.3 x V
DD
±1
687
MIN
0.9
2.3
0.6
TYP
MAX
1.8
3.7
1
10
UNITS
V
mA
µA
µs
V
µA
kHz
_______________________________________________________________________________________
3
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
MAX9725
ELECTRICAL CHARACTERISTICS (MAX9725E) (continued)
(V
DD
= 1.5V, V
PGND
= V
SGND
= 0V, V
SHDN
= 1.5V, V
SS
= V
PVSS
, C1 = C2 = 1µF, C
IN
= 1µF, R
L
= 32Ω, R
F
= 60kΩ, R
IN
= 10kΩ, T
A
=
T
MIN
to T
MAX,
unless otherwise noted. Typical values are at T
A
= +25°C.) (See the
Functional Diagrams.)
(Note 1)
PARAMETER
SYMBOL
V
DD
= 1.5V
Output Power (Note 3)
P
OUT
V
DD
= 1.0V, R
L
= 32Ω
V
DD
= 0.9V, R
L
= 32Ω
Total Harmonic Distortion Plus
Noise (Note 5)
Signal-to-Noise Ratio
Slew Rate
Maximum Capacitive Load
Crosstalk
Click-and-Pop Level
ESD Protection
Attenuation in Shutdown
THD+N
SNR
SR
C
L
XTALK
K
CP
V
ESD
A
TT(SD)
No sustained oscillations
f
IN
= 1.0kHz, R
L
= 32Ω, P
OUT
= 5mW
R
L
= 32Ω, peak voltage,
A-weighted, 32 samples per
second (Note 4)
Into shutdown
Out of shutdown
R
L
= 32Ω, P
OUT
= 12mW, f = 1kHz
R
L
= 16Ω, P
OUT
= 15mW, f = 1kHz
BW = 22Hz to 22kHz
R
L
= 32Ω, P
OUT
= 12mW
A-weighted filter
CONDITIONS
R
L
= 32Ω
R
L
= 16Ω
MIN
10
TYP
24
25
7
6
0.006
0.015
89
92
0.3
150
100
72.8
dBV
72.8
±8
-120
-75
kV
dB
%
dB
V/µs
pF
dB
mW
MAX
UNITS
Human Body Model (OUTR, OUTL)
V
SHDN
= 0V
R
L
= 32Ω
R
L
= 10kΩ
Note 1:
Note 2:
Note 3:
Note 4:
All specifications are 100% tested at T
A
= +25°C; temperature limits are guaranteed by design.
Input leakage current measurements limited by automated test equipment.
f
IN
= 1kHz, T
A
= +25°C, THD+N < 1%, both channels driven in-phase.
Testing performed with 32Ω resistive load connected to outputs. Mode transitions controlled by
SHDN.
K
CP
level calculated
as 20 log [peak voltage under normal operation at rated power level / peak voltage during mode transition]. Inputs are AC-
grounded.
Note 5:
Using existing resistors with 1% precision.
Note 6:
R
IN
= 10Ω, R
F
=10kΩ.
Typical Operating Characteristics
(V
DD
= 1.5V, V
PGND
= V
SGND
= 0V, V
SHDN
= 1.5V, V
SS
= V
PVSS,
C1 = C2 = 1µF, C
IN
= 1µF, THD+N measurement bandwidth =
22Hz to 22kHz, T
A
= +25°C, unless otherwise noted.) (See the
Functional Diagrams.)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
MAX9725 toc01
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
V
DD
= 1.5V
R
L
= 32Ω
A
V
= -2V/V
MAX9725 toc02
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
V
DD
= 1V
R
L
= 16Ω
A
V
= -2V/V
P
OUT
= 0.7mW
MAX9725 toc03
1
V
DD
= 1.5V
R
L
= 16Ω
A
V
= -2V/V
1
1
0.1
THD+N (%)
THD+N (%)
P
OUT
= 15mW
0.1
P
OUT
= 2mW
THD+N (%)
0.1
0.01
P
OUT
= 2mW
0.01
0.01
P
OUT
= 4mW
P
OUT
= 12mW
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
4
_______________________________________________________________________________________
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
MAX9725
Typical Operating Characteristics (continued)
(V
DD
= 1.5V, V
PGND
= V
SGND
= 0V, V
SHDN
= 1.5V, V
SS
= V
PVSS,
C1 = C2 = 1µF, C
IN
= 1µF, THD+N measurement bandwidth = 22Hz
to 22kHz, T
A
= +25°C, unless otherwise noted.) (See the
Functional Diagrams.)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
MAX9725 toc04
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
MAX9725 toc05
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
V
DD
= 1.5V
R
L
= 32Ω
A
V
= -2V/V
f
IN
= 20Hz
f
IN
= 1kHz
MAX9725 toc06
1
100
V
DD
= 1V
R
L
= 32Ω
A
V
= -2V/V
10
V
DD
= 1.5V
R
L
= 16Ω
A
V
= -2V/V
100
f
IN
= 20Hz
f
IN
= 1kHz
10
THD+N (%)
P
OUT
= 0.7mW
THD+N (%)
1
f
IN
= 10kHz
0.1
THD+N (%)
0.1
1
f
IN
= 10kHz
0.1
0.01
0.01
P
OUT
= 4mW
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0.001
0
10
20
30
40
OUTPUT POWER (mW)
0.001
0
10
20
30
40
OUTPUT POWER (mW)
0.01
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
MAX9725 toc07
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
MAX9725 toc08
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
-20
-30
-40
V
DD
= 1.5V
R
L
= 32Ω
MAX9725 toc09
100
10
V
DD
= 1V
R
L
= 16Ω
A
V
= -2V/V
100
V
DD
= 1V
R
L
= 32Ω
A
V
= -2V/V
f
IN
= 20Hz
f
IN
= 1kHz
-10
f
IN
= 20Hz
f
IN
= 1kHz
10
THD+N (%)
THD+N (%)
f
IN
= 10kHz
0.1
f
IN
= 10kHz
0.1
PSRR (dB)
15
1
1
-50
-60
-70
-80
0.01
0.001
0
5
10
15
OUTPUT POWER (mW)
0.01
0.001
0
5
10
OUTPUT POWER (mW)
-90
-100
-110
10
100
1k
FREQUENCY (Hz)
10k
100k
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX9725 toc10
CROSSTALK vs. FREQUENCY
MAX9725 toc11
OUTPUT POWER vs. SUPPLY VOLTAGE
70
OUTPUT POWER (mW)
60
50
40
30
20
f
IN
= 1kHz
R
L
= 16Ω
BOTH INPUTS
DRIVEN IN-PHASE
THD+N = 10%
MAX9725 toc12
0
-10
-20
-30
PSRR (dB)
0
-20
-40
PSRR (dB)
-60
-80
-100
V
DD
= 1V
R
L
= 32Ω
V
DD
= 1.5V
P
OUT
= 5mW
R
L
= 32Ω
80
-40
-50
-60
-70
-80
-90
-100
10
100
1k
FREQUENCY (Hz)
10k
100k
LEFT TO RIGHT
RIGHT TO LEFT
-120
10
100
1k
FREQUENCY (Hz)
10k
100k
10
0
0.9
1.1
THD+N = 1%
1.3
1.5
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5
Microchip MCU
