19-2859; Rev 0; 4/03
50mW, DirectDrive, Stereo Headphone
Amplifier with SmartSense and Shutdown
General Description
The MAX9720 stereo headphone amplifier combines
Maxim’s patented DirectDrive architecture and
SmartSense™, an automatic mono/stereo detection fea-
ture. Conventional headphone amplifiers require a bulky
DC-blocking capacitor between the headphone and the
amplifier. DirectDrive produces a ground-referenced out-
put from a single supply, eliminating the need for large
DC-blocking capacitors, saving cost, board space, and
component height.
SmartSense automatically detects the presence of a
short at either the left or right amplifier output. Under a
fault condition, the shorted output is automatically dis-
abled and the stereo input signal is automatically mixed
and routed to the remaining active channel. This feature
is useful in cell phone and PDA applications where a
variety of headphone jacks with unknown loads can be
inserted into the headphone jack socket. SmartSense
prevents both damage to the amplifier and eliminates
battery drain into a shorted load.
The MAX9720 delivers up to 50mW per channel into a
16Ω load and has an ultra-low 0.003% THD+N. A high
(92dB at 217kHz) power-supply rejection ratio (PSRR)
allows the device to operate from noisy digital supplies
without additional power conditioning. The gain of the
MAX9720 is set internally, further reducing component
count. Two gain options are available (-1V/V, MAX9720A
and -1.41V/V, MAX9720B). The headphone outputs
include a comprehensive click-and-pop circuitry that
eliminates audible glitches on startup and shutdown. A
shutdown mode provides a fast 250µs turn-on time.
The MAX9720 operates from a single 1.8V to 3.6V
supply and consumes only 5mA of supply current. The
MAX9720 also features thermal overload protection,
and is specified over the extended -40°C to +85°C tem-
perature range. The MAX9720 is available in a tiny
(2mm x 2mm x 0.6mm) 16-bump chip-scale package
(UCSP™) and a 16-pin TSSOP package.
Features
o
DirectDrive Eliminates Bulky DC-Blocking
Capacitors
o
SmartSense Automatic Short Detection
o
Low 5mA Quiescent Current
o
Fixed Gain Eliminates External Feedback Network
MAX9720A: -1V/V
MAX9720B: -1.41V/V
o
50mW per Channel Output Power
o
Ultra-Low 0.003% THD+N
o
High PSRR (92dB at 217Hz)
o
Integrated Click-and-Pop Suppression
o
1.8V to 3.6V Single-Supply Operation
o
Thermal Overload Protection
o
Available in Space-Saving Packages
16-Bump UCSP (2mm x 2mm x 0.6mm)
16-Pin TSSOP
MAX9720
Ordering Information
PART
MAX9720AEBE-T
MAX9720BEBE-T
MAX9720AEUE
MAX9720BEUE
TEMP RANGE
-40
o
C to +85
o
C
-40 C to +85 C
-40 C to +85 C
-40 C to +85 C
o
o
o
o
o
o
PIN/BUMP-
PACKAGE
16 UCSP-16
16 UCSP-16
16 TSSOP
16 TSSOP
GAIN
(V/V)
-1
-1.41
-1
-1.41
Simplified Block Diagram
3.6V TO 1.8V
SUPPLY
Applications
R
IN
MAX9720
R
OUT
HPS
MODE1
MODE2
ALERT
L
OUT
PDAs
Cellular Phones
MP3 Players
Notebook PCs
Smart Phones
Tablet PCs
Portable Audio Equipment
+
SmartSense
SmartSense and UCSP are trademarks of Maxim Integrated
Products, Inc.
Pin Configuration and Typical Application Circuit appear at
end of data sheet.
L
IN
________________________________________________________________
Maxim Integrated Products
1
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.
50mW, DirectDrive, Stereo Headphone
Amplifier with SmartSense and Shutdown
MAX9720
ABSOLUTE MAXIMUM RATINGS
PGND to SGND .....................................................-0.3V to +0.3V
PV
SS
to SV
SS
.........................................................-0.3V to +0.3V
V
DD
to PGND or SGND ............................................-0.3V to +4V
PV
SS
and SV
SS
to PGND or SGND ..........................-4V to +0.3V
IN_, OUT_, and HPS to SGND .......(SV
SS
- 0.3V) to (V
DD
+ 0.3V)
C1P to PGND ...............................(PGND - 0.3V) to (V
DD
+ 0.3V)
C1N to PGND .............................(PV
SS
- 0.3V) to (PGND + 0.3V)
ALERT
to PGND .......................................................-0.3V to +4V
MODE_ to PGND ........................................-0.3V to (V
DD
+ 0.3V)
TIME to SGND ............................................-0.3V to (V
DD
+ 0.3V)
Output Short Circuit to GND or V
DD ...............................
Continuous
Continuous Power Dissipation (T
A
= +70°C)
16-Bump UCSP (derate 8.2mW/°C above +70°C) .......659mW
16-Pin TSSOP (derate 9.4mW/°C above +70°C) .......754.7mW
Junction Temperature ......................................................+150°C
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Bump Temperature (soldering)
Reflow ...........................................................................+235°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
(V
DD
= V
MODE1
= V
MODE2
= 3.0V, PGND = SGND = 0V, R
L
=
∞,
C1 = C2 = 2.2µF. 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
Supply Current
Shutdown Supply Current
Turn-On/Turn-Off Time
CHARGE PUMP
Oscillator Frequency
HEADPHONE AMPLIFIERS
Voltage Gain
Gain Match
Total Output Offset Voltage
(Note 3)
Input Resistance
A
V
∆A
V
V
OS
R
IN
1.8V
≤
V
DD
≤
3.6V
(Note 3)
Power-Supply Rejection Ratio
PSRR
V
DD
= 3.0V,
200mV
P-P
ripple
(Note 3)
THD+N = 1%, f
IN
=
1kHz, T
A
= +25°C
DC
f
RIPPLE
= 217Hz
f
RIPPLE
= 1kHz
f
RIPPLE
= 20kHz
R
L
= 32Ω
R
L
= 16Ω
32
MAX9720A
MAX9720B
Between OUTL and OUTR
MAX9720A
MAX9720B
-5
-6.5
10
76
-1.02
-1.443
-1
-1.415
±1
-0.8
-1
15
92
92
86
61
50
50
mW
dB
+3.6
+4.5
20
-0.98
-1.386
V/V
%
mV
kΩ
f
OSC
272
320
368
kHz
V
DD
I
DD
I
SHDN
t
S
Inferred from PSRR test
Stereo mode
Mono mode (MODE1 = V
DD
, MODE2 = GND)
MODE1 = MODE2 = GND
1.8
5
3
6
250
10
3.6
8.4
V
mA
µA
µs
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Output Power
P
OUT
2
_______________________________________________________________________________________
50mW, DirectDrive, Stereo Headphone
Amplifier with SmartSense and Shutdown
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= V
MODE1
= V
MODE2
= 3.0V, PGND = SGND = 0V, R
L
=
∞,
C1 = C2 = 2.2µF. T
A
= T
MIN
to T
MAX,
unless otherwise noted.
Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Total Harmonic Distortion Plus
Noise
SYMBOL
CONDITIONS
R
L
= 32Ω,
P
OUT
= 30mW
R
L
= 16Ω,
P
OUT
= 30mW
MIN
TYP
0.003
%
0.005
97
0.8
No sustained oscillations
R
L
= 32Ω, P
OUT
= 1mW, f
IN
= 10kHz
150
75
140
15
R
SMS
t
SMS
I
TIME
R
TIME
V
TIME
HPS = GND
0.7
4
1
0.9 x
V
DD
0.7 x
V
DD
±1
10
V
ALERT
= V
DD
I
OL
= 3mA
0.7 x
V
DD
0.3 x
V
DD
±1
µA
1
0.4
µA
pF
µA
V
1.1
2.4
4
3.1
1.1
1.8
10
1.2
5.6
dB
V/µs
pF
dB
o
o
MAX9720
MAX
UNITS
THD+N
f
IN
= 1kHz
Signal-to-Noise Ratio
Slew Rate
Maximum Capacitive Load
Crosstalk
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
SmartSense
Shorted Load Threshold
Pulse Duration
DEBOUNCE TIME (TIME)
TIME Charging Current
TIME Discharge Switch
Resistance
TIME Threshold
SNR
SR
C
L
f
IN
= 1kHz, V
OUT
= 0.5V
RMS
, R
L
= 16Ω,
BW = 22Hz to 22kHz
C
C
Ω
µs
µA
kΩ
V
HEADPHONE SENSE INPUT (HPS)
V
IH
HPS Threshold
V
IL
Input Leakage Current
Input Capacitance
ALERT
Output Current High
Output Voltage Low
MODE_ INPUT
V
IH
MODE_ Thresholds
V
IL
MODE_ Input Leakage Current
I
OH
V
OL
I
IL
C
IN
MODE1= MODE2 = GND
V
V
Note 1:
All specifications are 100% tested at T
A
= +25
o
C; temperature limits are guaranteed by design.
Note 2:
Inputs are AC-coupled to ground.
Note 3:
Inputs are connected directly to ground.
_______________________________________________________________________________________
3
50mW, DirectDrive, Stereo Headphone
Amplifier with SmartSense and Shutdown
MAX9720
Typical Operating Characteristics
(V
DD
= 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = V
DD
.)
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX9720 toc01
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX9720 toc02
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
V
DD
= 3V
A
V
= -1.41V/V
R
L
= 16Ω
MAX9720 toc03
1
V
DD
= 3V
A
V
= -1V/V
R
L
= 16Ω
1
V
DD
= 3V
A
V
= -1V/V
R
L
= 32Ω
1
0.1
THD+N (%)
THD+N (%)
0.1
THD+N (%)
0.1
P
OUT
= 10mW
0.01
P
OUT
= 10mW
0.01
P
OUT
= 40mW
P
OUT
= 40mW
0.01
P
OUT
= 10mW
P
OUT
= 40mW
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
MAX9720 toc04
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
V
DD
= 1.8V
A
V
= -1V/V
R
L
= 16Ω
MAX9720 toc05
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
1
V
DD
= 1.8V
A
V
= -1V/V
R
L
= 32Ω
0.1
MAX9720 toc06
1
V
DD
= 3V
A
V
= -1.41V/V
R
L
= 32Ω
1
0.1
THD+N (%)
THD+N (%)
P
OUT
= 10mW
0.01
P
OUT
= 40mW
0.1
P
OUT
= 2mW
P
OUT
= 9mW
0.01
THD + N (%)
P
OUT
= 2mW
P
OUT
= 9mW
0.01
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
MAX9720 toc07
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX9720 toc08
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9720 toc09
1
V
DD
= 3V
A
V
= -1.41V/V
R
L
= 16Ω
1
V
DD
= 3V
A
V
= -1.41V/V
R
L
= 32Ω
100
10
0.1
THD+N (%)
THD+N (%)
P
OUT
= 2mW
P
OUT
= 9mW
0.01
0.1
THD+N (%)
1
P
OUT
= 2mW
0.01
0.01
P
OUT
= 9mW
OUTPUTS
IN PHASE
0.1
OUTPUTS
OUT OF
PHASE
V
DD
= 3V
A
V
= -1V/V
f = 20Hz
R
L
= 16Ω
60
90
120
150
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0.001
0
30
OUTPUT POWER (mW)
4
_______________________________________________________________________________________
50mW, DirectDrive, Stereo Headphone
Amplifier with SmartSense and Shutdown
Typical Operating Characteristics (continued)
(V
DD
= 3V, THD+N bandwidth = 22Hz to 22kHz, MODE1 = MODE2 = V
DD
.)
MAX9720
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9720 toc10
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9720 toc11
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9720 toc12
100
100
100
10
OUTPUTS
IN PHASE
10
OUTPUTS
IN PHASE
10
OUTPUTS
IN PHASE
THD+N (%)
THD+N (%)
1
OUTPUTS
OUT OF
PHASE
V
DD
= 3V
A
V
= -1V/V
f = 10kHz
R
L
= 16Ω
0
30
60
90
120
150
THD+N (%)
1
OUTPUTS
OUT OF
PHASE
1
OUTPUTS
OUT OF
PHASE
0.1
0.1
0.1
0.01
V
DD
= 3V
A
V
= -1V/V
f = 1kHz
R
L
= 16Ω
60
90
120
150
0.01
0.01
0.001
0
30
OUTPUT POWER (mW)
V
DD
= 3V
A
V
= -1V/V
f = 20Hz
R
L
= 32Ω
40
60
80
100
0.001
OUTPUT POWER (mW)
0.001
0
20
OUTPUT POWER (mW)
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9720 toc13
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9720 toc14
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
OUTPUTS
IN PHASE
MAX9720 toc15
100
100
V
DD
= 3V
A
V
= -1V/V
f = 10kHz
R
L
= 32Ω
100
10
OUTPUTS
IN PHASE
10
10
OUTPUTS
IN PHASE
THD+N (%)
1
OUTPUTS
OUT OF
PHASE
THD+N (%)
1
OUTPUTS
OUT OF
PHASE
THD+N (%)
1
OUTPUTS
OUT OF
PHASE
0.1
0.1
0.1
0.01
V
DD
= 3V
A
V
= -1V/V
f = 1kHz
R
L
= 32Ω
40
60
80
100
0.01
0.01
0.001
0
20
OUTPUT POWER (mW)
0.001
0
20
40
60
80
100
OUTPUT POWER (mW)
0.001
0
30
60
90
V
DD
= 3V
A
V
= -1.41V/V
f = 20Hz
R
L
= 16Ω
120
150
OUTPUT POWER (mW)
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9720 toc16
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9720 toc17
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9720 toc18
100
OUTPUTS
IN PHASE
100
OUTPUTS
IN PHASE
100
OUTPUTS
IN PHASE
10
10
10
THD+N (%)
THD+N (%)
1
0.1
OUTPUTS
OUT OF
PHASE
1
THD+N (%)
0.1
OUTPUTS
OUT OF
PHASE
1
OUTPUTS
OUT OF
PHASE
0.1
0.01
0.001
0
30
60
90
V
DD
= 3V
A
V
= -1.41V/V
f = 1kHz
R
L
= 16Ω
120
150
OUTPUT POWER (mW)
0.01
0.001
0
30
60
90
V
DD
= 3V
A
V
= -1.41V/V
f = 10kHz
R
L
= 16Ω
120
150
OUTPUT POWER (mW)
0.01
V
DD
= 3V
A
V
= -1.41V/V
f = 20Hz
R
L
= 32Ω
40
60
80
100
120
0.001
0
20
OUTPUT POWER (mW)
_______________________________________________________________________________________
5
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