19-6145; Rev 0; 12/11
Boosted 2.2W Class D Amplifier
with Automatic Level Control
General Description
The MAX98502 is a high-efficiency, Class D audio ampli-
fier that features an integrated boost converter to deliver
a constant output power over a wide range of battery
supply voltages.
The boost converter operates at 2MHz, requiring only a
small (2.2FH) external inductor and capacitor.
The automatic level control has a battery tracking func-
tion that reduces the output swing as the supply voltage
drops, preventing collapse of battery voltage.
The amplifier has differential inputs and an internal fully
differential design. The MAX98502 also features three
gain settings (6dB, 15.5dB, and 20dB) that are select-
able with a logic input.
The MAX98502 is available in a small, 0.5mm pitch
16-bump WLP package (2.1mm x 2.1mm). It is specified
over the extended -40NC to +85NC temperature range.
S
Boosted Class D Output
S
Integrated Automatic Level Control
S
Output Power
2.2W into 8I,
1.7W into 8I,
4.1W into 4I,
3.4W into 4I,
10% THD+N
1% THD+N
10% THD+N
1% THD+N
Features
MAX98502
S
Wide 2.5V to 5.5V Supply Voltage Range
S
Undervoltage Lockout Protection
S
High Total Efficiency of 87%
S
High Step-Up Switching Frequency (2MHz)
S
Active Emission Limiting for Low EMI
Applications
Cell Phones
Smartphones
GPS Devices
Mobile Internet Devices
Active Speaker Accessories
Ordering Information
PART
MAX98502EWE+
TEMP RANGE
-40NC to +85NC
PIN-PACKAGE
16 WLP
+Denotes
a lead(Pb)-free/RoHS-compliant package.
Typical Application Circuit appears at end of data sheet.
Simplified Block Diagram
BATTERY
V
BAT
B4
SDBST D4
SDSPK C3
GAIN B2
RKNEE
B3
CONTROL
A3
BOOST CONVERTER
A2
LX
V
CCOUT
MAX98502
A1 PVDD
INP D2
INN D3
B1 SPKP
DIFFERENTIAL
INPUT
C4
AGND
A4
BSTPGND
GAIN
D1, C2
SPKPGND
OUTPUT
STAGE
C1 SPKN
_______________________________________________________________
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.
Boosted 2.2W Class D Amplifier
with Automatic Level Control
MAX98502
ABSOLUTE MAXIMUM RATINGS
V
BAT
to AGND .........................................................-0.3V to +6V
V
CCOUT
to BSTPGND, AGND .................................-0.3V to +6V
PVDD to SPKPGND .................................................-0.3V to +6V
BSTPGND, SPKPGND to AGND ......................... -0.3V to +0.3V
GAIN to AGND ........................................ -0.3V to (V
BAT
+ 0.3V)
SDBST, SDSPK
to AGND ........................................-0.3V to +6V
All Other Pins (excluding LX) to AGND ..................-0.3V to +6V
Current Into/Out of LX, V
CCOUT
, BSTPGND .....................
Q3.9A
Continuous Current Into/Out of SPK_, PVDD,
SPKPGND ..................................................................
Q800mA
Continuous Input Current (all other pins) ........................
Q20mA
Duration of Short Circuit Between V
CCOUT
and BSTPGND...................................................... Continuous
Duration of SPK_ Short Circuit to PVDD or
SPKPGND ..............................................................Continuous
Duration of Short Circuit Between SPKP
and SPKN ..............................................................Continuous
Continuous Power Dissipation, Multilayer Board (T
A
= +70NC)
WLP (derate 20.4mW/NC above +70NC)........................1.33W
Junction Temperature .....................................................+150NC
Operating Temperature Range .......................... -40NC to +85NC
Storage Temperature Range............................ -65NC to +150NC
Soldering Temperature (reflow) ......................................+260NC
PACKAGE THERMAL CHARACTERISTICS (Note 1)
WLP
Junction-to-Ambient Thermal Resistance (q
JA
) ..........49°C/W
Note 1:
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, refer to
www.maxim-ic.com/thermal-tutorial.
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
BAT
= 3.6V, R
L
=
J
between SPKP and SPKN, A
V
= +6dB, C
IN
= 1FF, 20Hz to 22kHz AC measurement bandwidth, T
A
= T
MIN
to
T
MAX
, unless otherwise noted. Typical values are at T
A
= +25NC.) (Note 2)
PARAMETER
Power-Supply Rejection Ratio
(Note 3)
SYMBOL
PSRR
I
VBAT
Quiescent Current
I
PVDD
Combined Efficiency
Shutdown Current
Turn-On Time
BOOST CONVERTER
Battery Supply Voltage Range
Soft-Start Interval
Undervoltage Lockout
Boost Converter Output Voltage
Output Current Limit
Input Current Limit
nMOS Current Limit
pMOS Turn-Off Current Limit
V
BAT
t
ON
UVLO
I
MAX
I
LIMIT
I
LX,MAX
V
BAT
falling
V
BAT
R
= 3.6V
Startup, V
CCOUT
= 0V
2.1
5.45
1.5
0.3
3.3
10
0.5
V
VCCOUT
I
LOAD
= 0mA
2.5
5.6
2.2
5.5
2.3
5.65
5.5
V
ms
V
V
A
A
A
mA
E
I
SHDN
t
ON
CONDITIONS
T
A
= +25NC, V
BAT
= 2.5V to 5.5V
T
A
= +25NC,
SDSPK
=
SDBST
= V
BAT
T
A
= +25NC, V
SDSPK
= 0V,
SDBST
= V
BAT
T
A
= +25NC, PVDD = 5.55V,
SDSPK
=
SDBST
= V
BAT
P
OUT
= 1.7W, f = 1kHz, Z
SPK
= 8I + 68FH
V
SDSPK
= V
SDBST
= 0V, T
A
= +25NC
Time from power-on to full operation
MIN
TYP
95
3.7
0.1
1.7
87
0.04
10
1.5
12
0.15
2.7
%
FA
ms
mA
MAX
UNITS
dB
2
______________________________________________________________________________________
Boosted 2.2W Class D Amplifier
with Automatic Level Control
ELECTRICAL CHARACTERISTICS (continued)
(V
BAT
= 3.6V, R
L
=
J
between SPKP and SPKN, A
V
= +6dB, C
IN
= 1FF, 20Hz to 22kHz AC measurement bandwidth, T
A
= T
MIN
to
T
MAX
, unless otherwise noted. Typical values are at T
A
= +25NC.) (Note 2)
PARAMETER
Switching Frequency
Efficiency
Startup Short-Circuit Time
Thermal Shutdown
LX Leakage Current
SPEAKER AMPLIFIER
Output Offset Voltage
V
OS
T
A
= +25NC
Peak voltage, T
A
=
+25NC, A-weighted, 32
samples per second,
Z
SPK
= 8I + 68FH,
(Notes 3, 4)
Z
SPK
= 4I + 33FH
Output Power (Note 5)
P
OUT
Z
SPK
= 8I + 68FH
Into shutdown
Out of shutdown
THD+N
P
1%
THD+N
P
10%
THD+N
P
1%
THD+N
P
10%
1
-56
dBV
-56
3.4
4.1
1.7
2.2
0.05
0.04
300
GAIN = AGND
Gain
Output Current Limit
Efficiency
Output Noise
E
P
OUT
= 1.5W, f = 1kHz, Z
SPK
= 8I + 68FH
P
OUT
= 1.5W, f = 1kHz, Z
SPK
= 4I + 33FH
A-weighted
A
V
= 6dB
(GAIN = AGND)
SDBST
=
SDSPK
=
V
BAT
A
V
= 15.5dB
(GAIN =
unconnected)
A
V
= 20dB
(GAIN = V
BAT
)
Common-Mode Rejection Ratio
Bias Voltage
CMRR
V
BIAS
V
SDBST
= V
SDSPK
= 0V
f = 1kHz
All gain settings
1.3
36
12
6.5
A
V
GAIN = unconnected
GAIN = V
BAT
5.5
15
19.5
6
15.5
20
2
92
87
43
54
18
11
110
60
1.4
1.5
dB
V
72
26
16
6.5
16
20.5
A
%
FV
RMS
dB
kHz
%
W
3
mV
V
LX
= 0V or 5.5V,
V
CCOUT
= 5.5V
T
A
= +25NC
-40NC
P
T
A
P
+85NC
-1.0
SYMBOL
f
S
E
0.1A
P
I
OUT
P
0.75A
Converter latch off
CONDITIONS
MIN
1.8
TYP
2.0
93
50
165
+0.1
0.1
+1.0
MAX
2.2
UNITS
MHz
%
ms
NC
FA
MAX98502
Click-and-Pop Level
K
CP
Total Harmonic Distortion Plus
Noise
Output Switching Frequency
THD+N
f = 1kHz, P
OUT
= 1.7W, T
A
= +25NC,
Z
SPK
= 4I + 33FH
f = 1kHz, P
OUT
= 850mW, T
A
= +25NC,
Z
SPK
= 8I + 33FH
Input Resistance
R
IN
kI
_______________________________________________________________________________________
3
Boosted 2.2W Class D Amplifier
with Automatic Level Control
MAX98502
ELECTRICAL CHARACTERISTICS (continued)
(V
BAT
= 3.6V, R
L
=
J
between SPKP and SPKN, A
V
= +6dB, C
IN
= 1FF, 20Hz to 22kHz AC measurement bandwidth, T
A
= T
MIN
to
T
MAX
, unless otherwise noted. Typical values are at T
A
= +25NC.) (Note 2)
PARAMETER
ALC
Attack Time
Release Time
Maximum Attenuation
Attenuation Resolution
R
KNEE
= 154kI
Knee Voltage
V
KNEE
T
A
= +25NC
R
KNEE
= 40.5kI
R
KNEE
= 13kI
V
KNEE
= 3.25V
V
KNEE
= 3.35V
Knee Resistor
R
KNEE
T
A
= +25NC,
A
V
= 15.5dB
V
KNEE
= 3.45V
V
KNEE
= 3.55V
V
KNEE
= 3.65V
V
KNEE
= 3.75V
V
KNEE
= 3.85V
DIGITAL INPUTS (SDBST,
SDSPK)
Input Voltage High
Input Voltage Low
Input Capacitance
Input Leakage Current
V
iH
V
IL
C
IN
I
IN
T
A
= +25NC
-1.0
10
+1.0
1.4
0.4
2.19
3.14
3.71
20
1.6
8
0.5
2.3
3.3
3.9
43.2
37.4
32.4
27.4
23.2
18.7
15.0
V
V
pF
FA
kI
2.42
3.47
4.10
V
Fs/dB
s/dB
dB
dB
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Note 2:
100% production tested at T
A
= +25NC. Specifications over temperature limits are guaranteed by design.
Note 3:
Amplifier inputs are AC-coupled to AGND.
Note 4:
Mode transitions are controlled by
SDSPK.
4
______________________________________________________________________________________
Boosted 2.2W Class D Amplifier
with Automatic Level Control
Typical Operating Characteristics
(V
BAT
= 3.6V, R
L
= ∞ between SPKP and SPKN, A
V
= +15.5dB, RKNEE = V
BAT
, 20Hz to 22kHz AC measurement bandwidth, unless
otherwise noted.)
MAX98502
General
BATTERY CURRENT
vs. BATTERY VOLTAGE
MAX98502 toc01
BATTERY CURRENT
vs. BATTERY VOLTAGE
130
BATTERY CURRENT (µA)
120
110
100
90
80
70
60
INPUTS AC-COUPLED TO GND
SDSPK = SDBST = V
BAT
MAX98502 toc02
7
6
BATTERY CURRENT (mA)
5
4
3
2
1
0
2.5
3.0
3.5
INPUTS AC-COUPLED TO GND
SDSPK = SDBST = V
BAT
140
4.0
4.5
5.0
5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
BATTERY CURRENT
vs. BATTERY VOLTAGE
0.035
BATTERY CURRENT (µA)
0.030
0.025
0.020
0.015
0.010
0.005
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUTS AC-COUPLED TO GND
SDSPK = SDBST = AGND
MAX98502 toc03
TURN-ON RESPONSE
MAX98502 toc04
0.040
SDBST
V
CCOUT
2V/div
SPKR OUT
2ms/div
BATTERY VOLTAGE (V)
EFFICIENCY vs. OUTPUT POWER
MAX98502 toc05
EFFICIENCY vs. OUTPUT POWER
90
80
EFFICIENCY (%)
70
60
50
40
30
20
V
BAT
= 3.6V
V
BAT
= 3.0V
V
BAT
= 4.2V
MAX98502 toc06
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
0.5
V
BAT
= 4.2V
100
V
BAT
= 3.6V
V
BAT
= 3.0V
Z
LOAD
= 8I + 68µF
f
IN
= 1kHz
1.0
1.5
P
OUT
(W)
2.0
2.5
3.0
10
0
0
Z
LOAD
= 4I + 33µF
C
VCCOUT
= 22µF (0804)
f
IN
= 1kHz
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
P
OUT
(W)
_______________________________________________________________________________________
5
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