19-3700; Rev 0; 3/08
16V
P-P
Class G Amplifier with
Inverting Boost Converter
General Description
The MAX9738 features a mono Class G power amplifi-
er with an integrated inverting boost converter. The
Class G amplifier is specifically designed to drive the
high capacitance of a ceramic/piezoelectric loud-
speaker. The inverting boost converter can typically
supply up to 400mA of peak output current, allowing
for a constant output of 16V
P-P
over the 2.7V to 5.5V
supply voltage range.
The MAX9738 maximizes battery life by offering high-
performance efficiency. Maxim’s proprietary output
stage provides efficiency levels greater than Class AB
devices without the EMI penalties commonly associat-
ed with Class D amplifiers.
The MAX9738 is ideally suited to deliver the high output
voltage swing required to drive ceramic/piezoelectric
speakers.
The device utilizes fully differential inputs and outputs,
comprehensive click-and-pop suppression, shutdown
control, and soft-start circuitry. The MAX9738 is fully
specified over the -40°C to +85°C extended tempera-
ture range and is available in an ultra-small, lead-free
5x4 WLP (2.5mm x 2mm) package.
Typical Application Circuit/Functional Diagram and Pin
Configuration appear at end of data sheet.
Features
♦
Integrated Inverting Boost Converter
♦
2.7V to 5.5V Single-Supply Operation
♦
16V
P-P
Output Voltage Swing, Ideal for Driving a
Ceramic Speaker
♦
Maintains Output Voltage Swing as the Battery
Decays
♦
Clickless/Popless Operation
♦
Small, Thermally Efficient 5x4 WLP Package
(2.5mm x 2mm)
MAX9738
Applications
Cellular Phones
Smartphones
MP3 Players
Personal Media
Players
Handheld Gaming
Consoles
Notebook Computers
Ordering Information
PART
MAX9738EWP+TG45
TEMP RANGE
-40°C to +85°C
PIN-
PACKAGE
5x4 WLP
+Denotes
a lead-free package.
T = Tape and reel.
G45 indicates protective die coating.
Simplified Block Diagram
V
DD
V
DD
V
BAT
V
SS
INVERTING
BOOST
CONVERTER
ISET
BST
LX
FB+
IN+
IN-
FB-
GND
+
-
CLASS G
OUTPUT
STAGE
OUT+
OUT-
MAX9738
PIEZOELECTRIC
SPEAKER
________________________________________________________________
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.
16V
P-P
Class G Amplifier with
Inverting Boost Converter
MAX9738
ABSOLUTE MAXIMUM RATINGS
(Voltages with respect to GND.)
V
DD
, V
BAT
............................................................... -0.3V to +6V
V
DD
to V
BAT
......................................................... -0.1V to +0.1V
V
SS
...................................................Capacitor Connection Only,
(V
BAT
- 10V) to +0.3V
OUT+, OUT- .................................................-6V to (V
DD
+ 0.3V)
(OUT+ to OUT-) ................................................... -8.7V to +8.7V
IN+, IN-, FB+, FB-, ISET .............................-0.3V to (V
DD
+ 0.3V)
LX ..................................................(V
DD
- 11.5V) to (V
DD
+ 0.3V)
BST..........................................................(LX - 0.3V) to (LX + 6V)
SHDN........................................................................-0.3V
to +6V
Continuous Current into/out of
OUT+, OUT-, V
BAT
, V
SS
, V
DD
.......................................400mA
Any Other Pin ..................................................................20mA
Duration of OUT+, OUT- Short Circuit to
V
DD
, GND, V
SS
(V
SS
> -6V).....................................Continuous
RMS Current per Bump
V
BAT
, LX .........................................................................800mA
Continuous Power Dissipation (T
A
= +70°C)
20-Bump UCSP (derate 10mW/°C above +70°C) ........800mW
Operating Temperature Range .......................... -40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range ............................ -65°C to +150°C
Bump Temperature (soldering) Reflow............................+235°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
BAT
=
SHDN
= 3.6V, GND = 0V, V
DD
- V
SS
= 9V, R
ISET
= 100kΩ, R
IN+
= R
IN-
= 10kΩ, R
FB+
= R
FB-
= 10kΩ, C
L
= open, R
L
=
∞,
C1 = 10μF, C2 = 10μF, C3 = 0.1μF, C4 = 0.1μF, 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
Total Quiescent Current
Maximum Total Quiescent
Current
Shutdown Supply Current
Turn-On Time
ISET Bias Voltage
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
V
DD
I
DD_TOT
I
DD_TOT_MAX
I
SHDN
t
ON
V
ISET
Inferred from PSRR test
I
VDD
+ I
VBAT
(boost converter disabled)
Typical application circuit (Note 2)
SHDN
= GND
Time from shutdown or power-on to full
operation (C
IN
= 0.1μF)
0.9
2.7
7
16.5
0.6
10
1.0
150
15
1.1
2
5.5
12.5
V
mA
mA
μA
ms
V
°C
°C
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
16V
P-P
Class G Amplifier with
Inverting Boost Converter
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= V
BAT
=
SHDN
= 3.6V, GND = 0V, V
DD
- V
SS
= 9V, R
ISET
= 100kΩ, R
IN+
= R
IN-
= 10kΩ, R
FB+
= R
FB-
= 10kΩ, C
L
= open, R
L
=
∞,
C1 = 10μF, C2 = 10μF, C3 = 0.1μF, C4 = 0.1μF, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
SPEAKER AMPLIFIER
Output Offset Voltage
Input DC Bias Voltage
Common-Mode Output Level
V
OS
V
BIAS
V
CM
V
DD
= 2.7V or 5.5V
(Note 3)
V
DD
= 2.7V
V
DD
= 5.5V
Peak voltage into/out of shutdown,
A-weighted, 32 samples per second
(Note 4)
V
DD
= 2.7V (Note 5)
V
BAT
= V
DD
= 2.7V or 5.5V, R
LOAD
= 8Ω,
THD+N = 1%
V
BAT
= V
DD
=
2.7V, f = 1kHz
THD+N < 1%, C
IN_
=
0.1μF, C
L
= 1.6μF,
R
L
= 20Ω, T
A
= +25°C
(Note 6)
V
BAT
= V
DD
=
2.7V, f = 10kHz
V
BAT
= V
DD
=
3.6V, f = 1kHz
V
BAT
= V
DD
=
3.6V, f = 10kHz
Common-Mode Rejection
Ratio
CMRR
f
IN
= 1kHz (Note 7)
V
DD
= 2.7V to 5.5V
Power-Supply Rejection Ratio
PSRR
f = 217Hz, 100mV
P-P
ripple
f = 1kHz, 100mV
P-P
ripple
f = 20kHz, 100mV
P-P
ripple
Total Harmonic Distortion Plus
Noise
Peak Load Current
Signal-to-Noise Ratio
Dynamic Range
SHDN
Input Threshold
SHDN
Input Leakage Current
SNR
DR
V
IH
V
IL
I
IH
, I
IL
-3
V
OUT
= 5V
RMS
, A-weighted (Note 6)
A-weighted (Note 8)
1.4
0.4
+3
f = 1kHz, V
OUT
= 16V
P-P
, C
L
= 1.6μF,
R
L
= 20Ω
f = 10kHz, V
OUT
= 15.2V
P-P
, C
L
= 1.6μF,
R
L
= 20Ω
54
5.65
5.37
11.5
T
A
= +25°C
T
MIN
≤
T
A
≤
T
MAX
1.0
0.75
2.40
1.23
1.17
3
-60
12
0.25
5.5
5.0
V
RMS
6.3
6.0
60
60
80
70
60
0.2
0.4
355
95
110
mA
dB
dB
V
μA
0.5
%
dB
dB
12.5
±3.7
±15
±30
1.5
1.60
3.45
mV
V
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX9738
Click-and-Pop Level
Voltage Gain
Continuous Output Power
K
CP
A
V
P
OUT
dBV
dB
W
Output Voltage
V
OUT
THD+N
_______________________________________________________________________________________
3
16V
P-P
Class G Amplifier with
Inverting Boost Converter
MAX9738
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= V
BAT
=
SHDN
= 3.6V, GND = 0V, V
DD
- V
SS
= 9V, R
ISET
= 100kΩ, R
IN+
= R
IN-
= 10kΩ, R
FB+
= R
FB-
= 10kΩ, C
L
= open, R
L
=
∞,
C1 = 10μF, C2 = 10μF, C3 = 0.1μF, C4 = 0.1μF, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Switching Frequency
FET On-Time
Minimum FET Off-Time
Peak Output Current
FET Current Limit (DC)
FET Current Limit (Transient)
FET On-Resistance
Regulated Output Voltage
Transient Load Regulation
Maximum Output Ripple
BST Shutdown Leakage
V
BAT
Shutdown Current
LX Shutdown Leakage
R
DSON
V
DD
> 3V, typical application circuit
(Note 9)
T
A
= +25°C (Note 10)
Typical application circuit, inductor I
SAT
rating > 1.7A
I
LX
= 100mA, T
A
= +25°C
V
BAT
- V
SS
0 to 400mA load step, typical application
circuit
I
LOAD
= 20mA, typical application circuit
SHDN
= 0V, LX = 0V, BST = 5V
V
BAT
= V
DD
,
SHDN
= 0V, LX = 0V,
BST = 5V
LX = 0V,
SHDN
= 0V, BST = 5V
8.15
0.77
t
FON
550
100
750
220
400
1.1
1.6
0.2
8.9
300
200
0.01
0.01
0.01
1
3
3
0.26
9.60
1.35
SYMBOL
CONDITIONS
MIN
TYP
MAX
1.5
950
350
UNITS
MHz
ns
ns
mA
A
A
Ω
V
mV
mV
P-P
μA
μA
μA
INVERTING BOOST CONVERTER (V
DD
- V
SS
= -8.75V)
Note 1:
Note 2:
All devices are 100% production tested at T
A
= +25°C. Specifications over temperature limits are guaranteed by design.
Total quiescent current depends on overall efficiency and varies with the LX inductor value and ESR, diode turn-on volt-
age, and the parasitic losses in all external components.
Note 3:
Input DC bias voltage determines the maximum voltage swing of the input signal. An input signal with an amplitude
greater than the input DC bias voltage results in clipping.
Note 4:
Amplifier inputs AC-coupled to GND.
Note 5:
Voltage gain is defined as [V
OUT+
- V
OUT-
]/[V
IN+
- V
IN-
].
Note 6:
V
OUT
is defined as [V
OUT+
- V
OUT-
].
Note 7:
Matching of external AC-coupling input capacitors and gain resistors is critical to achieving good CMRR.
Note 8:
Dynamic range calculated by measuring the RMS voltage difference between a -60dBFS output signal and the noise floor,
then adding 60dB. Full scale is defined as the output signal needed to achieve 1% THD+N.
Note 9:
Peak output current depends on external power-supply components and the signal frequency.
Note 10:
Boost converter current limit is tested with a DC sweep. Actual current-limit values under transient conditions may be high-
er. At high input supply, V
BAT
, and low inductance, L, transient current limit might be higher than 1.7A.
4
_______________________________________________________________________________________
16V
P-P
Class G Amplifier with
Inverting Boost Converter
Typical Operating Characteristics
(V
DD
= V
BAT
=
SHDN
=+3.6V, GND = 0V, R
ISET
= 100kΩ, R
IN+
= R
IN-
= 10kΩ, R
FB+
= R
FB-
= 10kΩ, C
L
= 1.6μF, R
L
= 20Ω, C1 = 10μF,
C2 = 10μF, C3 = 0.1μF, C4 = 0.1μF, T
A
= +25°C,
Typical Application Circuit.)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
MAX9738 toc01
MAX9738
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
MAX9738 toc02
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
V
DD
= 4.2V
1
THD+N (%)
MAX9738 toc03
10
V
DD
= 2.7V
1
THD+N (%)
10
V
DD
= 3.6V
1
THD+N (%)
10
0.1
V
OUT
= 3.5V
RMS
0.01
V
OUT
= 1.2V
RMS
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0.1
V
OUT
= 5.5V
RMS
0.01
V
OUT
= 2V
RMS
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
0.1
V
OUT
= 5.5V
RMS
0.01
V
OUT
= 2.4V
RMS
0.001
10
100
1k
FREQUENCY (Hz)
10k
100k
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT VOLTAGE
MAX9738 toc04
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT VOLTAGE
MAX9738 toc05
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT VOLTAGE
V
DD
= 4.2V
1
THD+N (%)
f
IN
= 5kHz
f
IN
= 10kHz
MAX9738 toc06
10
V
DD
= 2.7V
f
IN
= 5kHz
1
THD+N (%)
f
IN
= 10kHz
0.1
f
IN
= 1kHz
0.01
10
V
DD
= 3.6V
f
IN
= 5kHz
1
THD+N (%)
f
IN
= 10kHz
10
0.1
f
IN
= 1kHz
0.01
0.1
f
IN
= 1kHz
0.01
0.001
0
1
2
3
4
5
6
7
OUTPUT VOLTAGE (V
RMS
)
0.001
0
1
2
3
4
5
6
7
OUTPUT VOLTAGE (V
RMS
)
0.001
0
1
2
3
4
5
6
7
OUTPUT VOLTAGE (V
RMS
)
TOTAL QUIESCENT CURRENT
vs. SUPPLY VOLTAGE
MAX9738 toc07
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
MAX9738 toc08
POWER-SUPPLY REJECTION RATIO
-10
-20
-30
PSRR (dB)
-40
-50
-60
-70
-80
-90
V
RIPPLE
= 100mV
P-P
MAX9738 toc09
17
TOTAL QUIESCENT CURRENT (mA)
15
13
11
9
7
I
Q
= I
VDD
+ I
VBAT
5
2
3
4
SUPPLY VOLTAGE (V)
5
6
1.0
0.9
SHUTDOWN CURRENT (μA)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
0
6.0
10
100
1k
FREQUENCY (Hz)
10k
100k
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5
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