MAX9725AEBC+TG45 [MAXIM]
1V, Low-Power, DirectDrive, Stereo Headphone Amplifier with Shutdown;
| 型号： | MAX9725AEBC+TG45 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 1V, Low-Power, DirectDrive, Stereo Headphone Amplifier with Shutdown |
| 文件： | 总17页 (文件大小：332K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3465; Rev 4; 3/09
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
MAX9725
General Description
Features
♦ Low Quiescent Current
2.1mA (MAX9725A–MAX9725D)
2.3mA (MAX9725E)
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.
♦ 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
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).
♦
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)
Block Diagrams
SINGLE
C3
V
DD
1.5V CELL
AA OR AAA
BATTERY
MAX9725A–MAX9725D
Applications
DirectDrive OUTPUTS
ELIMINATE DC-BLOCKING
CAPACITORS.
MP3 Players
Cellular Phones
PDAs
Smart Phones
INL
Portable Audio Equipment
OUTL
Ordering Information
C1P
C1N
PV
SS
INVERTING
CHARGE PUMP
TOP
MARK
GAIN
(V/V)
PART
PIN-PACKAGE
C2
V
SS
MAX9725AEBC+TG45
MAX9725AETC+
12 UCSP
+ACK
+AAEW
+ACL
-2
-2
12 TQFN-EP*
12 UCSP
OUTR
INR
MAX9725BEBC+TG45
-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.
SGND
PGND
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
*EP = Exposed pad.
UCSP is a trademark of Maxim Integrated Products, Inc.
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
ABSOLUTE MAXIMUM RATINGS
SGND to PGND .....................................................-0.3V to +0.3V
SHDN to SGND or PGND.........................................-0.3V to +4V
Output Short-Circuit Current ......................................Continuous
V
V
to SGND or PGND ............................................-0.3V to +2V
DD
SS
to PV ...........................................................-0.3V to +0.3V
Continuous Power Dissipation (T = +70°C)
SS
A
C1P to PGND..............................................-0.3V to (V
+ 0.3V)
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
DD
C1N to PGND............................................(PV - 0.3V) to +0.3V
SS
V
SS
, PV to GND ....................................................+0.3V to -2V
SS
OUTR, OUTL, INR, INL to SGND
(MAX9725A–MAX9725D)..............(V - 0.3V) to (V
+ 0.3V)
+ 0.3V)
SS
DD
DD
OUTR, OUTL to SGND
MAX9725
(MAX9725E)..................................(V - 0.3V) to (V
SS
INR, INL to SGND (MAX9725E)...................................-4V to +4V
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
= V
= 0V, V
= 1.5V, V = V
, C1 = C2 = 1µF, C = 1µF, R = ∞, T = T
to T
unless other-
PGND
SGND
SHDN
SS
PVSS
IN
L
A
MIN
MAX,
wise noted. Typical values are at T = +25°C.) (See the Functional Diagrams.) (Note 1)
A
PARAMETER
Supply Voltage Range
Quiescent Supply Current
SYMBOL
CONDITIONS
Guaranteed by PSRR test
Both channels active
MIN
TYP
MAX
1.8
UNITS
V
V
0.9
DD
DD
I
2.1
0.6
3.3
10
30
mA
T
A
T
A
= +25°C
= -40°C to +85°C
Shutdown Current
I
V
= 0V
SHDN
µA
µs
V
SHDN
Shutdown to Full Operation
SHDN Thresholds
t
180
ON
V
V
V
V
= 0.9V to 1.8V
0.7 x V
493
IH
DD
DD
DD
DD
V
= 0.9V to 1.8V
0.3 x V
DD
IL
SHDN Input Leakage Current
CHARGE PUMP
I
= 0.9V to 1.8V (Note 2)
1
µA
LEAK
Oscillator Frequency
AMPLIFIERS
f
580
667
kHz
OSC
MAX9725A
MAX9725B
MAX9725C
MAX9725D
-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
-1.96
-1.47
-0.98
-3.92
Voltage Gain
A
V
V/V
Gain Match
ΔA
%
V
MAX9725A/MAX9725D
MAX9725B
1.05
1.58
2.1
Input AC-coupled,
Total Output Offset Voltage
Input Resistance
V
R = 32Ω to GND,
mV
kΩ
dB
OS
L
T
= +25°C
A
MAX9725C
R
15
60
35
IN
V
= 0.9V to 1.8V, T = +25°C
80
DD
A
Power-Supply Rejection Ratio
PSRR
f
= 1kHz
70
IN
IN
100mV
ripple
P-P
f
= 20kHz
62
R = 32Ω
R = 16Ω
L
10
20
L
V
= 1.5V
DD
25
Output Power (Note 3)
P
mW
OUT
V
V
= 1.0V, R = 32Ω
7
DD
DD
L
= 0.9V, R = 32Ω
6
L
2
_______________________________________________________________________________________
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
MAX9725
ELECTRICAL CHARACTERISTICS (MAX9725A–MAX9725D) (continued)
(V
DD
= 1.5V, V
= V
= 0V, V
= 1.5V, V = V
, C1 = C2 = 1µF, C = 1µF, R = ∞, T = T
to T
unless other-
PGND
SGND
SHDN
SS
PVSS
IN
L
A
MIN
MAX,
wise noted. Typical values are at T = +25°C.) (See the Functional Diagrams.) (Note 1)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
R = 32Ω, P
= 12mW, f = 1kHz
= 15mW, f = 1kHz
0.006
0.015
89
Total Harmonic Distortion Plus
Noise
L
OUT
THD+N
%
R = 16Ω, P
L
OUT
BW = 22Hz to 22kHz
A-weighted filter
Signal-to-Noise Ratio
SNR
SR
R = 32Ω, P
= 12mW
dB
L
OUT
92
Slew Rate
0.2
V/µs
pF
Maximum Capacitive Load
Crosstalk
C
No sustained oscillations
= 1.0kHz, R = 32Ω, P = 5mW
OUT
150
100
L
XTALK
f
dB
IN
L
R = 32Ω, peak voltage,
A-weighted, 32 samples per
second (Note 4)
L
Into shutdown
Out of shutdown
72.8
Click-and-Pop Level
ESD Protection
K
dBV
kV
CP
72.8
8
V
Human Body Model (OUTR, OUTL)
ESD
ELECTRICAL CHARACTERISTICS (MAX9725E)
(V
DD
= 1.5V, V
= V
= 0V, V
= 1.5V, V = V
, C1 = C2 = 1µF, C = 1µF, R = 32Ω, R = 60kΩ, R = 10kΩ, T
=
F
IN
PGND
SGND
SHDN
SS
PVSS
IN
L
A
T
MIN
to T unless otherwise noted. Typical values are at T = +25°C.) (See the Functional Diagrams.) (Note 1)
MAX, A
PARAMETER
SYMBOL
CONDITIONS
Guaranteed by PSRR test
Both channels active
MIN
TYP
MAX
1.8
3.7
1
UNITS
V
Supply Voltage Range
V
0.9
DD
DD
Quiescent Supply Current
I
2.3
0.6
mA
T
A
T
A
= +25°C
= -40°C to +85°C
Shutdown Current
I
V
= 0V
SHDN
µA
µs
V
SHDN
10
Shutdown to Full Operation
SHDN Thresholds
t
180
ON
V
V
V
V
= 0.9V to 1.8V
0.7 x V
DD
IH
DD
DD
DD
V
= 0.9V to 1.8V
0.3 x V
IL
DD
SHDN Input Leakage Current
CHARGE PUMP
I
= 0.9V to 1.8V (Note 2)
1
µA
LEAK
Oscillator Frequency
AMPLIFIERS
f
483
592
687
kHz
OSC
Voltage Gain
A
(Note 5)
-6.11
-6.07
-1.0
-6.00
V/V
V/V
V
Minimum Stable Gain
ΔA
V
Input AC-coupled, R = 32Ω to GND,
L
Total Output Offset Voltage
V
0.63
9.78
2.1
mV
OS
T
A
= +25°C (Note 6)
Input Resistance
INR, INL Input Leakage
Current
R
6.3
14
kΩ
IN
I
100
nA
LK
Maximum Input Parasitic
Capacitance
C
5
pF
dB
PAR
V
= 0.9V to 1.8V, T = +25°C
52.9
67.8
70
DD
A
Power-Supply Rejection Ratio
PSRR
f
IN
IN
= 1kHz
100mV
(Note 5)
ripple
P-P
f
= 20kHz
62
_______________________________________________________________________________________
3
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
ELECTRICAL CHARACTERISTICS (MAX9725E) (continued)
(V
= 1.5V, V
= V
= 0V, V
= 1.5V, V = V
, C1 = C2 = 1µF, C = 1µF, R = 32Ω, R = 60kΩ, R = 10kΩ, T =
F IN
PVSS IN L A
DD
PGND
SGND
SHDN
SS
T
MIN
to T unless otherwise noted. Typical values are at T = +25°C.) (See the Functional Diagrams.) (Note 1)
MAX, A
PARAMETER
SYMBOL
CONDITIONS
R = 32Ω
MIN
TYP
24
MAX UNITS
10
L
V
= 1.5V
DD
R = 16Ω
L
25
Output Power (Note 3)
P
mW
OUT
V
V
= 1.0V, R = 32Ω
= 0.9V, R = 32Ω
7
DD
DD
L
6
L
MAX9725
R = 32Ω, P
R = 16Ω, P
L
= 12mW, f = 1kHz
= 15mW, f = 1kHz
0.006
0.015
89
Total Harmonic Distortion Plus
Noise (Note 5)
L
OUT
OUT
THD+N
%
BW = 22Hz to 22kHz
A-weighted filter
Signal-to-Noise Ratio
SNR
SR
R = 32Ω, P
= 12mW
dB
L
OUT
92
Slew Rate
0.3
150
V/µs
pF
Maximum Capacitive Load
Crosstalk
C
No sustained oscillations
= 1.0kHz, R = 32Ω, P = 5mW
OUT
L
XTALK
f
100
dB
IN
L
R = 32Ω, peak voltage,
A-weighted, 32 samples per
second (Note 4)
L
Into shutdown
Out of shutdown
72.8
Click-and-Pop Level
K
dBV
CP
72.8
ESD Protection
V
Human Body Model (OUTR, OUTL)
R = 32Ω
8
-120
-75
kV
ESD
L
Attenuation in Shutdown
A
V
= 0V
SHDN
dB
TT(SD)
R = 10kΩ
L
Note 1: All specifications are 100% tested at T = +25°C; temperature limits are guaranteed by design.
A
Note 2: Input leakage current measurements limited by automated test equipment.
Note 3: f = 1kHz, T = +25°C, THD+N < 1%, both channels driven in-phase.
IN
A
Note 4: Testing performed with 32Ω resistive load connected to outputs. Mode transitions controlled by SHDN. K level calculated
CP
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 = 10Ω, R =10kΩ.
IN
F
Typical Operating Characteristics
(V
= 1.5V, V
= V
= 0V, V
= 1.5V, V = V
C1 = C2 = 1µF, C = 1µF, THD+N measurement bandwidth =
DD
PGND
SGND
SHDN
SS
PVSS, IN
22Hz to 22kHz, T = +25°C, unless otherwise noted.) (See the Functional Diagrams.)
A
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
1
0.1
1
0.1
1
0.1
V
= 1.5V
V
= 1V
V
= 1.5V
DD
DD
DD
R = 32Ω
R = 16Ω
R = 16Ω
L
L
L
A
= -2V/V
A
= -2V/V
A
= -2V/V
V
V
V
P
= 0.7mW
OUT
P
= 15mW
= 2mW
OUT
P
= 2mW
OUT
0.01
0.001
0.01
0.001
0.01
0.001
P
OUT
P
= 4mW
OUT
P
= 12mW
OUT
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
4
_______________________________________________________________________________________
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
MAX9725
Typical Operating Characteristics (continued)
(V
= 1.5V, V
= V
= 0V, V
= 1.5V, V = V
C1 = C2 = 1µF, C = 1µF, THD+N measurement bandwidth = 22Hz
DD
PGND
SGND
SHDN
SS
PVSS, IN
to 22kHz, T = +25°C, unless otherwise noted.) (See the Functional Diagrams.)
A
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
100
10
1
100
10
1
1
0.1
V
= 1.5V
V
= 1.5V
DD
DD
L
V
V
= 1V
DD
f
f
= 20Hz
= 1kHz
IN
IN
R = 16Ω
V
R = 32Ω
A
L
f
f
= 20Hz
= 1kHz
R = 32Ω
IN
IN
L
A
= -2V/V
= -2V/V
A
= -2V/V
V
P
= 0.7mW
OUT
f
= 10kHz
IN
f
= 10kHz
IN
0.1
0.1
0.01
0.001
0.01
0.01
P
= 4mW
OUT
0.001
0.001
0
10
20
30
40
0
10
20
30
40
10
100
1k
FREQUENCY (Hz)
10k
100k
OUTPUT POWER (mW)
OUTPUT POWER (mW)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
100
10
1
100
10
1
V
= 1.5V
DD
V
= 1V
V
= 1V
DD
L
DD
f
f
= 20Hz
= 1kHz
IN
IN
R = 32Ω
L
R = 16Ω
V
R = 32Ω
A = -2V/V
V
L
f
f
= 20Hz
= 1kHz
IN
IN
A
= -2V/V
f
= 10kHz
IN
f
= 10kHz
IN
0.1
0.1
0.01
0.01
0.001
0.001
0
5
10
15
0
5
10
15
10
100
1k
10k
100k
FREQUENCY (Hz)
OUTPUT POWER (mW)
OUTPUT POWER (mW)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
CROSSTALK vs. FREQUENCY
OUTPUT POWER vs. SUPPLY VOLTAGE
0
-20
80
70
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
V
P
= 1.5V
= 5mW
R = 32Ω
f
= 1kHz
DD
OUT
L
IN
V
= 1V
DD
R = 16Ω
L
R = 32Ω
L
BOTH INPUTS
DRIVEN IN-PHASE
60
50
40
30
20
10
0
-40
THD+N = 10%
LEFT TO RIGHT
-60
-80
-100
-120
RIGHT TO LEFT
10k
THD+N = 1%
1.3
10
100
1k
FREQUENCY (Hz)
100k
0.9
1.1
1.5
10
100
1k
10k
100k
SUPPLY VOLTAGE (V)
FREQUENCY (Hz)
_______________________________________________________________________________________
5
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
Typical Operating Characteristics (continued)
(V
= 1.5V, V
= V
= 0V, V
= 1.5V, V = V
C1 = C2 = 1µF, C = 1µF, THD+N measurement bandwidth = 22Hz
DD
PGND
SGND
SHDN
SS
PVSS, IN
to 22kHz, T = +25°C, unless otherwise noted.) (See the Functional Diagrams.)
A
OUTPUT POWER
vs. SUPPLY VOLTAGE
OUTPUT POWER
vs. LOAD RESISTANCE
OUTPUT POWER
vs. LOAD RESISTANCE
50
45
40
35
30
25
20
15
10
5
80
70
60
50
40
30
20
10
0
80
70
60
50
40
30
20
10
0
V
f
= 1.5V
= 1kHz
V
f
= 1V
DD
f
= 1kHz
DD
IN
IN
L
= 1kHz
R = 32Ω
BOTH INPUTS
DRIVEN IN-PHASE
IN
BOTH INPUTS
DRIVEN IN-PHASE
BOTH INPUTS
DRIVEN IN-PHASE
MAX9725
THD+N = 10%
THD+N = 1%
THD+N = 10%
THD+N = 10%
THD+N = 1%
THD+N = 1%
1.3
0
0.9
1.1
1.5
10
100
1k
10
100
1k
SUPPLY VOLTAGE (V)
LOAD RESISTANCE (Ω)
LOAD RESISTANCE (Ω)
POWER DISSIPATION
vs. OUTPUT POWER
POWER DISSIPATION
vs. OUTPUT POWER
GAIN FLATNESS
vs. FREQUENCY
80
35
2
1
0
R = 16Ω
L
70
60
50
40
30
20
10
0
30
25
20
15
10
5
-1
-2
-3
-4
-5
-6
-7
-8
-9
R = 16Ω
L
V
f
P
= 1.5V
V
f
P
= 1V
DD
IN
DD
IN
R = 32Ω
L
= 1kHz
= P
= 1kHz
= P
R = 32Ω
L
+ P
OUTR
+ P
OUTR
OUT
OUTL
OUT
OUTL
OUTPUTS IN-PHASE
OUTPUTS IN-PHASE
0
-10
0
10
20
30 40
50
0
5
10
15 20
10
100
1k
10k
100k
OUTPUT POWER (mW)
OUTPUT POWER (mW)
FREQUENCY (Hz)
OUTPUT POWER vs. CHARGE-PUMP
CAPACITANCE AND LOAD RESISTANCE
OUTPUT SPECTRUM
vs. FREQUENCY
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
5.0
40
35
0
-20
NO LOAD
f
= 1kHz
IN
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
C1 = C2 = 2.2μF
C1 = C2 = 1μF
R = 32Ω
L
V
V
= -60dBV
= 1.5V
OUT
DD
-40
30
25
20
15
10
5
-60
-80
-100
-120
-140
-160
C1 = C2 = 0.68μF
V
= 1.5V
DD
C1 = C2 = 0.47μF
f
IN
= 1kHz
THD+N = 1%
0
0.9
1.0
1.1
1.2
1.3
1.4
1.5
10
20
30
40 50
0
5
10
15
20
SUPPLY VOLTAGE (V)
LOAD RESISTANCE (Ω)
FREQUENCY (kHz)
6
_______________________________________________________________________________________
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
MAX9725
Typical Operating Characteristics (continued)
(V
= 1.5V, V
= V
= 0V, V
= 1.5V, V = V
C1 = C2 = 1µF, C = 1µF, THD+N measurement bandwidth = 22Hz
DD
PGND
SGND
SHDN
SS
PVSS, IN
to 22kHz, T = +25°C, unless otherwise noted.) (See the Functional Diagrams.)
A
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
POWER-UP/-DOWN WAVEFORM
EXITING SHUTDOWN
MAX9725toc24
MAX9725 toc23
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
V
DD
OUT_
1V/div
1V/div
SHDN
500mV/div
OUT_
10mV/div
0.9
1.1
1.3
1.5
200ms/div
200μs/div
SUPPLY VOLTAGE (V)
Pin Description
PIN
BUMP
NAME
FUNCTION
THIN
QFN
UCSP
A1
1
C1N
Flying Capacitor Negative Terminal. Connect a 1µF capacitor from C1P to C1N.
Inverting Charge-Pump Output. Bypass with 1µF from PV to PGND. PV must be connected to
SS
SS
2
A2
PV
SS
V
.
SS
Left-Amplifier Inverting Input. Connect input resistor R from input capacitor C1N to INL (MAX9725E
IN
only).
3
A3
INL
Right-Amplifier Inverting Input. Connect input resistor R from input capacitor C1N to INR
IN
(MAX9725E only).
4
5
6
A4
B4
B3
INR
V
Amplifier Negative Power Supply. Must be connected to PV
.
SS
SS
Signal Ground. SGND must be connected to PGND. SGND is the ground reference for the input and
output signal.
SGND
7
8
C4
C3
C2
C1
B1
OUTR Right-Channel Output. Connect feedback resistor R between OUTR and INR (MAX9725E only).
FB
OUTL Left-Channel Output. Connect feedback resistor R between OUTL and INL (MAX9725E only).
FB
9
V
Positive Power-Supply Input. Bypass with a 1µF capacitor to PGND.
DD
10
11
C1P
Flying Capacitor Positive Terminal. Connect a 1µF capacitor from C1P to C1N.
PGND Power Ground. Ground reference for the internal charge pump. PGND must be connected to SGND.
Active-Low Shutdown. Connect to V
charge pump.
for normal operation. Pull low to disable the amplifier and
DD
12
EP
B2
—
SHDN
EP
Exposed Paddle. Internally connected to V . Leave paddle unconnected or solder to V
.
SS
SS
_______________________________________________________________________________________
7
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
Previous attempts to eliminate the output-coupling
Detailed Description
capacitors involved biasing the headphone return
The MAX9725 stereo headphone driver features Maxim’s
(sleeve) to the DC-bias voltage of the headphone
amplifiers. This method raises some issues:
DirectDrive architecture, eliminating the large output-cou-
pling capacitors required by conventional single-supply
•
The sleeve is typically grounded to the chassis.
Using this biasing approach, the sleeve must be
isolated from system ground, complicating product
design.
headphone drivers. The MAX9725 consists of two 20mW
class AB headphone drivers, shutdown control, inverting
charge pump, internal gain-setting resistors, and compre-
hensive click-and-pop suppression circuitry (see the
Functional Diagrams). A negative power supply (PV ) is
7
SS
•
•
During an ESD strike, the driver’s ESD structures
are the only path to system ground. The driver must
be able to withstand the full ESD strike.
created by inverting the positive supply (V ). Powering
DD
the drivers from V
and PV increases the dynamic
DD
SS
range of the drivers to almost twice that of other 1V sin-
gle-supply drivers. This increase in dynamic range allows
for higher output power.
When using the headphone jack as a line out to
other equipment, the bias voltage on the sleeve may
conflict with the ground potential from other equip-
ment, resulting in possible damage to the drivers.
The outputs of the MAX9725 are biased about GND
(Figure 1). The benefit of this GND bias is that the driver
outputs do not have a DC component, thus large DC-
blocking capacitors are unnecessary. Eliminating the
DC-blocking capacitors on the output saves board
space, system cost, and improves frequency response.
V
V
DD
DirectDrive
Conventional single-supply headphone drivers have their
outputs biased about a nominal DC voltage (typically half
the supply) for maximum dynamic range. Large coupling
capacitors are needed to block the DC bias from the
headphones. Without these capacitors, a significant
amount of DC current flows to the headphone, resulting
in unnecessary power dissipation and possible damage
to both headphone and headphone driver.
V
OUT
/ 2
DD
GND
CONVENTIONAL DRIVER-BIASING SCHEME
Maxim’s DirectDrive architecture uses a charge pump
to create an internal negative supply voltage. This
allows the MAX9725 outputs to be biased about GND,
increasing the dynamic range while operating from a
single supply. A conventional amplifier powered from
1.5V ideally provides 18mW to a 16Ω load. The
MAX9725 provides 25mW to a 16Ω load. The
DirectDrive architecture eliminates the need for two
large (220µF, typ) DC-blocking capacitors on the out-
put. The MAX9725 charge pump requires two small
ceramic capacitors, conserving board space, reducing
cost, and improving the frequency response of the
headphone driver. See the Output Power vs. Charge-
Pump Capacitance and Load Resistance graph in the
Typical Operating Characteristics for details of the possi-
ble capacitor sizes.
V
DD
V
OUT
GND
-V
DD
DirectDrive BIASING SCHEME
Figure 1. Traditional Driver Output Waveform vs. MAX9725
Output Waveform (Ideal Case)
8
_______________________________________________________________________________________
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
MAX9725
ADDITIONAL THD+N DUE
TO DC-BLOCKING CAPACITORS
LF ROLLOFF (16Ω LOAD)
0
10
-3
-5
330μF
220μF
1
-10
-3dB CORNER FOR
100μF
100μF IS 100Hz
-15
0.1
0.01
33μF
TANTALUM
-20
-25
-30
0.001
0.0001
ALUM/ELEC
100
-35
10
100
FREQUENCY (Hz)
1k
10
1k
FREQUENCY (Hz)
10k
100k
Figure 3. Distortion Contributed By DC-Blocking Capacitors
Figure 2. Low-Frequency Attenuation for Common DC-Blocking
Capacitor Values
Low-Frequency Response
Large DC-blocking capacitors limit the amplifier’s low-
frequency response and can distort the audio signal:
voltage coefficient appears as frequency-dependent
distortion. Figure 3 shows the THD+N introduced by
two different capacitor dielectric types. Note that
below 100Hz, THD+N increases rapidly.
1) The impedance of the headphone load and the DC-
blocking capacitor forms a highpass filter with the
-3dB point set by:
The combination of low-frequency attenuation and fre-
quency-dependent distortion compromises audio
reproduction in portable audio equipment that empha-
sizes low-frequency effects such as multimedia lap-
tops, as well as MP3, CD, and DVD players. These
low-frequency, capacitor-related deficiencies are elimi-
nated by using DirectDrive technology.
1
f
=
-3dB
2πR C
L
OUT
where R is the impedance of the headphone and
L
C
OUT
is the value of the DC-blocking capacitor. The
Charge Pump
The MAX9725 features a low-noise charge pump. The
580kHz switching frequency is well beyond the audio
range, and does not interfere with the audio signals.
The switch drivers feature a controlled switching speed
that minimizes noise generated by turn-on and turn-off
transients. The di/dt noise caused by the parasitic bond
wire and trace inductance is minimized by limiting the
turn-on/off speed of the charge pump. Additional high-
frequency noise attenuation can be achieved by
increasing the size of C2 (see the Functional Diagrams).
Extra noise attenuation is not typically required.
highpass filter is required by conventional single-
ended, single power-supply headphone drivers to
block the midrail DC-bias component of the audio
signal from the headphones. The drawback to the
filter is that it can attenuate low-frequency signals.
Larger values of C
reduce this effect but result
OUT
in physically larger, more expensive capacitors.
Figure 2 shows the relationship between the size of
C
and the resulting low-frequency attenuation.
OUT
Note that the -3dB point for a 16Ω headphone with
a 100µF blocking capacitor is 100Hz, well within the
normal audio band, resulting in low-frequency
attenuation of the reproduced signal.
Shutdown
The MAX9725’s low-power shutdown mode reduces
supply current to 0.6µA. Driving SHDN low disables the
amplifiers and charge pump. The driver’s output imped-
ance is typically 50kΩ (MAX9725A), 37.5kΩ
(MAX9725B), 25kΩ (MAX9725C), 100kΩ (MAX9725D),
2) The voltage coefficient of the DC-blocking capacitor
contributes distortion to the reproduced audio signal
as the capacitance value varies when the function of
the voltage across the capacitor changes. At low
frequencies, the reactance of the capacitor domi-
nates at frequencies below the -3dB point and the
or R (MAX9725E) when in shutdown mode.
F
_______________________________________________________________________________________
9
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
Applications Information
OUTPUT POWER vs. SUPPLY VOLTAGE
WITH INPUTS IN- AND OUT-OF-PHASE
Power Dissipation
Linear power amplifiers can dissipate a significant
50
f
= 1kHz
IN
45
40
35
30
25
20
15
10
5
amount of power under normal operating conditions.
The maximum power dissipation for each package is
given in the Absolute Maximum Ratings section under
Continuous Power Dissipation or can be calculated by
the following equation:
R = 16Ω
L
THD+N = 1%
°
INPUTS 180 OUT-OF-PHASE
MAX9725
T
- T
A
J(MAX)
P
=
DISSPKG(MAX)
θ
JA
INPUTS IN-PHASE
where T
is +150°C, T is the ambient tempera-
A
J(MAX)
0
ture, and θ is the reciprocal of the derating factor in
JA
0.9
1.1
1.3
1.5
°C/W as specified in the Absolute Maximum Ratings
SUPPLY VOLTAGE (V)
section. For example, θ for the thin QFN package is
JA
+59.3°C/W.
Figure 4. Output Power vs. Supply Voltage with Inputs In-/Out-
of-Phase
The MAX9725 has two power dissipation sources, the
charge pump and the two amplifiers. If the power dissi-
pation exceeds the rated package dissipation, reduce
Click-and-Pop Suppression
In conventional single-supply audio drivers, the output-
coupling capacitor is a major contributor of audible
clicks and pops. Upon startup, the driver charges the
coupling capacitor to its bias voltage, typically half the
supply. Likewise, on shutdown, the capacitor is dis-
charged to GND. This results in a DC shift across the
capacitor that appears as an audible transient at the
speaker. The MAX9725’s DirectDrive technology elimi-
nates the need for output-coupling capacitors.
V
, increase load impedance, decrease the ambient
DD
temperature, or add heatsinking to the device. Large
output, supply, and ground traces decrease θ , allow-
ing more heat to be transferred from the package to
surrounding air.
JA
Output Power
The MAX9725’s output power increases when the left
and right audio signals differ in magnitude and/or
phase. Figure 4 shows the two extreme cases for in-
and out-of-phase input signals. The output power of a
typical stereo application lies between the two extremes
shown in Figure 4. The MAX9725 is specified to output
20mW per channel when both inputs are in-phase.
The MAX9725 also features extensive click-and-pop
suppression that eliminates any audible transient
sources internal to the device. The Power-Up/-Down
Waveform in the Typical Operating Characteristics
shows minimal DC shift and no spurious transients at
the output upon startup or shutdown.
Powering Other Circuits from
the Negative Supply
The MAX9725 internally generates a negative supply
In most applications, the output of the preamplifier dri-
ving the MAX9725 has a DC bias of typically half the
supply. At startup, the input-coupling capacitor is
charged to the preamplifier’s DC bias voltage through
the internal input resistor (25kΩ for MAX9725A-
MAX9725D, minimum 10kΩ for MAX9725E) causing an
audible click and pop. Delaying the rise of SHDN 4 or 5
time constants, based on R x C , relative to the start-
up of the preamplifier eliminates any click and pop
caused by the input filter (see the Functional Diagrams).
voltage (PV ) to provide the ground-referenced output
SS
signal. Other devices can be powered from PV pro-
SS
vided the current drawn from the charge pump does
not exceed 1mA. Headphone driver output power and
THD+N will be adversely affected if more than 1mA is
drawn from PV . Using PV as an LCD bias is a typi-
SS
SS
cal application for the negative supply.
IN
IN
PV is unregulated and proportional to V . Connect
SS
DD
a 1µF capacitor from C1P to C1N for best charge-pump
operation.
10 ______________________________________________________________________________________
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
MAX9725
Hold Capacitor (C2)
Component Selection
Input Filtering
The AC-coupling capacitor (C ) and an internal gain-
IN
setting resistor form a highpass filter that removes any
DC bias from an input signal (see the Functional
Diagrams). C allows the MAX9725A–MAX9725D to
IN
bias the signal to an optimum DC level. The -3dB point
of the highpass filter, assuming zero source imped-
ance, is given by:
The hold capacitor’s value and ESR directly affect the
ripple at PV . Increasing the value of C2 reduces rip-
SS
ple. Choosing a capacitor with lower ESR reduces rip-
ple and output impedance. Lower capacitance values
can be used in systems with low maximum output
power levels. See the Output Power vs. Charge-Pump
Capacitance and Load Resistance graph in the Typical
Operating Characteristics.
Power-Supply Bypass Capacitor (C3)
The power-supply bypass capacitor (C3) lowers the
output impedance of the power supply and reduces the
impact of the MAX9725’s charge-pump switching tran-
1
f
=
-3dB
2π × R × C
IN
IN
Choose C so f
is well below the lowest frequency of
IN
IN
-3dB
sients. Bypass V
to PGND with the same value as
DD
interest. R for the MAX9725A–MAX9725D is 25kΩ and a
C1. Place C3 as close to V
as possible.
DD
minimum of 10kΩ for the MAX9725E. Setting f
too
-3dB
Layout and Grounding
Proper layout and grounding are essential for optimum
performance. Connect PGND and SGND together at a
high affects the amplifier’s low-frequency response. Use
capacitors with low-voltage coefficient dielectrics. Film or
C0G dielectric capacitors are good choices for AC-cou-
pling capacitors. Capacitors with high-voltage coeffi-
cients, such as ceramics, can result in increased
distortion at low frequencies.
single point on the PC board. Connect PV
to SV
SS
SS
to PGND
and bypass with C2 to PGND. Bypass V
DD
with C3. Place capacitors C2 and C3 as close to the
MAX9725 as possible. Route PGND, and all traces that
carry switching transients, away from SGND and the
audio signal path.
Charge-Pump Capacitor Selection
Use capacitors with less than 100mΩ of ESR. Low-ESR
ceramic capacitors minimize the output impedance of the
charge pump. Capacitors with an X7R dielectric provide
the best performance over the extended temperature
range. Table 1 lists suggested capacitor manufacturers.
The MAX9725 does not require additional heatsinking.
The thin QFN package features an exposed paddle that
improves thermal efficiency of the package. Ensure the
exposed paddle is electrically isolated from GND and
V . Connect the exposed paddle to V if necessary.
DD SS
Flying Capacitor (C1)
The value of C1 affects the charge pump’s load regula-
tion and output impedance. Choosing C1 too small
degrades the MAX9725’s ability to provide sufficient
current drive and leads to a loss of output voltage.
Increasing the value of C1 improves load regulation
and reduces the charge-pump output impedance. See
the Output Power vs. Charge-Pump Capacitance and
Load Resistance graph in the Typical Operating
Characteristics.
UCSP Applications Information
For the latest application details on UCSP construction,
dimensions, tape carrier information, printed circuit
board techniques, bump-pad layout , and recommend-
ed reflow temperature profile, as well as the latest infor-
mation on reliability testing results, go to Maxim’s
website at www.maxim-ic.com/ucsp for the
Application Note 1891: Wafer-Level Packaging (WLP)
and Its Applications.
Table 1. Suggested Capacitor Manufacturers
SUPPLIER
PHONE
FAX
—
WEBSITE
www.murata.com
Murata
770-436-1300
800-348-2496
847-803-6100
Taiyo Yuden
TDK
847-925-0899
847-390-4405
www.t-yuden.com
www.component.tdk.com
______________________________________________________________________________________ 11
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
System Diagrams
0.9V TO 1.8V
1μF
MAX9725
V
DD
SHDN
1μF
1μF
INR
INL
MP3
DECODER
STEREO
DAC
MAX9725A–
MAX9725D
C1P
C1N
1μF
OUTR
OUTL
V
SS
PV
SS
1μF
SGND PGND
R
F
V
DD
MAX9725E
1μF
SHDN
OUTL
1μF
R
IN
INL
P
C1N
DIN
VSS
CHARGE
PUMP
1μF
1μF
V
SS
1μF
R
IN
INR
OUTR
SGND PGND
R
F
12 ______________________________________________________________________________________
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
MAX9725
Functional Diagrams
0.9V TO 1.8V
LEFT-
CHANNEL
AUDIO IN
C
IN
C3
1μF
0.47μF
12
3
9
(B2)
(A3)
(C2)
V
DD
INL
SHDN
R *
F
V
DD
R
IN
25kΩ
8
(C3)
OUTL
HEADPHONE
JACK
SGND
UVLO/
SHUTDOWN
CONTROL
10
(C1)
C1P
V
SS
CHARGE
PUMP
CLICK-AND-POP
SUPPRESSION
C1
1μF
1
(A1) C1N
V
DD
SGND
7
(C4)
OUTR
MAX9725A–
MAX9725D
R
IN
V
SS
25kΩ
R *
F
PV
V
5
PGND
SS
SGND
INR
SS
6
4
2
11
(B4)
(B3)
(A4)
(A2)
(B1)
C
IN
C2
1μF
0.47μF
LEFT-
CHANNEL
AUDIO IN
*MAX9725A = 50kΩ.
MAX9725B = 37.5kΩ.
MAX9725C = 25kΩ.
MAX9725D = 100kΩ.
( ) DENOTE BUMPS FOR UCSP.
______________________________________________________________________________________ 13
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
Functional Diagrams (continued)
LEFT-CHANNEL
AUDIO IN
C
1μF
IN
0.9V TO 1.8V
R
IN
C3
1μF
MAX9725
12
3
9
(B2)
(A3)
(C2)
V
DD
INL
SHDN
R
F
V
DD
8
(C3)
OUTL
HEADPHONE
JACK
SGND
UVLO/
SHUTDOWN
CONTROL
10
(C1)
C1P
V
SS
CHARGE
PUMP
CLICK-AND-POP
SUPPRESSION
C1
1μF
1
(A1) C1N
V
SS
SGND
7
(C4)
OUTR
MAX9725E
V
DD
R
R
F
PV
V
5
(B4)
PGND
SS
SGND
INR
SS
6
(B3)
4
(A4)
2
11
(B1)
(A2)
C2
1μF
IN
C
IN
1μF
( ) DENOTE BUMPS FOR UCSP.
RIGHT-
CHANNEL
AUDIO IN
14 ______________________________________________________________________________________
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
MAX9725
Pin Configurations
MAX9725
TOP VIEW
(BUMP-SIDE DOWN)
TOP VIEW
1
2
3
4
9
8
7
A
B
C1N
PV
INL
INR
SS
SGND
10
11
6
5
C1P
PGND
SHDN
SGND
OUTL
V
SS
PGND
C1P
SHDN
V
SS
MAX9725
C
OUTR
V
DD
INR
12
4
*EP
+
UCSP
1
2
3
THIN QFN
*EP = EXPOSED PAD.
Block Diagrams (continued)
Ordering Information (continued)
TOP
MARK
GAIN
(V/V)
PART
PIN-PACKAGE
SINGLE
C3
MAX9725BETC+
MAX9725CEBC+TG45
MAX9725CETC+
12 TQFN-EP*
12 UCSP
+AAEX
+ACM
+AAEY
+ACN
-1.5
-1
V
DD
1.5V CELL
AA OR AAA
BATTERY
R
FB
12 TQFN-EP*
-1
MAX9725E
MAX9725DEBC+TG45 12 UCSP
-4
DirectDrive OUTPUTS
ELIMINATE DC-BLOCKING
CAPACITORS.
INL
MAX9725DETC+
12 TQFN-EP*
+AAEZ
+AEF
-4
MAX9725EEBC+TG45
MAX9725EETC+**
12 UCSP
ADJ
ADJ
OUTL
12 TQFN-EP*
+AAGH
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.
C1P
C1N
PV
SS
INVERTING
CHARGE PUMP
C2
V
SS
*EP = Exposed pad.
**Future product—contact factory for availability.
OUTR
INR
SGND
PGND
R
FB
______________________________________________________________________________________ 15
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
Package Information
Chip Information
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in
the package code indicates RoHS status only. Package draw-
ings may show a different suffix character, but the drawing per-
tains to the package regardless of RoHS status.
PROCESS: BiCMOS
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
12 UCSP
B12-1
21-0104
21-0139
MAX9725
12 TQFN-EP
T1244-4
16 ______________________________________________________________________________________
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
MAX9725
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
1
11/04
5/05
Initial release
—
Removed future product asterisks for UCSP package, added EC table note
1–3, 13, 14
Added MAX9725E packages, MAX9725E EC table, block diagram, functional
diagram, and system diagram. Updated package outlines.
2
11/07
1–3, 6, 8–19
3
4
8/08
3/09
Corrected error in Functional Diagrams
14
Updated Ordering Information, style changes
1, 15
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 17
© 2009 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
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MAX9725AETC-T
Audio Amplifier, 0.025W, 2 Channel(s), 1 Func, BICMOS, 4 X 4 MM, 0.80 MM HEIGHT, MO-220-WGGB, TQFN-12
MAXIM
MAX9725BEBC+
Audio Amplifier, 0.025W, 2 Channel(s), 1 Func, BICMOS, PBGA12, 1.54 X 2.02 MM, 0.60 MM HEIGHT, ROHS COMPLIANT, UCSP-12
MAXIM
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