ETC MAX98500

19-5189; Rev 0; 8/10
MAX98500
带有自动电平控制的
2.2W升压型D类放大器
概述
特性
MAX98500为内置boost转换器的高效D类音频放大器，能
够在较宽的电池供电电压范围内提供恒定的输出功率。
S D类放大器升压输出
S 内置自动电平控制电路
Boost转换器的工作频率为2MHz，仅需一个小尺寸(2.2µH)
外部电感和电容。
S 输出功率
为8Ω负载提供2.2W功率，THD+N为10%
为8Ω负载提供1.7W功率，THD+N为1%
自动电平控制电路具有电池跟踪功能，能够在电源电压跌
落时降低输出摆幅，从而防止电池失效。
S 2.5V至5.5V较宽的电源电压范围
放大器具有差分输入，内部采用全差分设计。MAX98500
还具有3种增益设置(6dB、15.5dB和20dB)，通过一个逻
辑输入进行选择。
S 欠压锁定保护
MAX98500采用小尺寸、0.5mm焊球间隔的16焊球WLP
封 装(2.1mm x 2.1mm)， 工 作 在-40°C至+85°C扩 展 级 温
度范围。
S 较高的升压转换器开关频率(2MHz)
S 整体效率高达87%
S 有源辐射抑制可降低EMI
应用
定购信息
扬声器配件
PART
TEMP RANGE
PIN-PACKAGE
蜂窝电话
MAX98500EWE+
-40NC to +85NC
16 WLP
GPS设备
+表示无铅(Pb)/符合RoHS标准的封装。
移动互联网设备
典型应用电路在数据资料的最后给出。
智能电话
简化功能框图
BATTERY
VBAT
LX
B4
BOOST CONVERTER
SDBST D4
SDSPK C3
GAIN B2
RKNEE
A3
CONTROL
MAX98500
A2
VCCOUT
A1 PVDD
B3
INP D2
INN D3
B1 SPKP
DIFFERENTIAL
INPUT
C4
AGND
OUTPUT
STAGE
GAIN
A4
BSTPGND
C1 SPKN
D1, C2
SPKPGND
本文是英文数据资料的译文，文中可能存在翻译上的不准确或错误。如需进一步确认，请在您的设计中参考英文资料。
有关价格、供货及订购信息，请联络Maxim亚洲销售中心：10800 852 1249 (北中国区)，10800 152 1249 (南中国区)，
或访问Maxim的中文网站：china.maximintegrated.com。
MAX98500
带有自动电平控制的
2.2W升压型D类放大器
ABSOLUTE MAXIMUM RATINGS
Duration of SPK_ Short Circuit to PVDD or
SPKPGND...............................................................Continuous
Duration of Short Circuit Between SPKP
and SPKN...............................................................Continuous
Continuous Power Dissipation, Multilayer Board (TA = +70NC)
WLP (derate 20.4mW/NC above +70NC)........................1.33W
θJA (Note 1).................................................................49NC/W
Junction Temperature......................................................+150NC
Operating Temperature Range........................... -40NC to +85NC
Storage Temperature Range............................. -65NC to +150NC
Soldering Temperature (reflow).......................................+260NC
VBAT to AGND..........................................................-0.3V to +6V
VCCOUT 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 (VBAT + 0.3V)
SDBST, SDSPK to AGND....................................... -0.3V to VBAT
All Other Pins (excluding LX) to AGND...................-0.3V to +6V
Current Into/Out of LX, VCCOUT, BSTPGND...................... Q3.9A
Continuous Current Into/Out of SPK_, PVDD,
SPKPGND................................................................... Q800mA
Continuous Input Current (all other pins)......................... Q20mA
Duration of Short Circuit Between VCCOUT
and BSTPGND....................................................... Continuous
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to china.maximintegrated.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
(VBAT = 3.6V, RL = J between SPKP and SPKN, AV = +6dB, CIN = 1FF, 20Hz to 22kHz AC measurement bandwidth, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
PARAMETER
Power-Supply Rejection Ratio
(Note 3)
SYMBOL
PSRR
IVBAT
Quiescent Current
IPVDD
Combined Efficiency
Shutdown Current
Turn-On Time
E
ISHDN
tON
CONDITIONS
MIN
TYP
MAX
95
TA = +25NC, VBAT = 2.5V to 5.5V
dB
TA = +25NC, SDSPK = SDBST = VBAT
3.05
TA = +25NC, VSDSPK = 0V, SDBST = VBAT
0.09
0.15
TA = +25NC, PVDD = 5.55V, SDSPK =
SDBST = VBAT
1.7
2.7
87
POUT = 1.7W, f = 1kHz, ZSPK = 8I + 68FH
VSDSPK = VSDBST = 0V, TA = +25NC
Time from power-on to full operation
UNITS
mA
%
0.04
1.5
FA
10
12
ms
BOOST CONVERTER
Battery Supply Voltage Range
Soft-Start Interval
Undervoltage Lockout
Boost Converter Output Voltage
2.5
VBAT
UVLO
VBAT falling
VVCCOUT ILOAD = 0mA
IMAX
VBAT R = 3.6V
Input Current Limit
ILIMIT
Startup, VCCOUT = 0V
nMOS Current Limit
2.1
2.2
2.3
5.45
5.5
5.65
ILX,MAX
Switching Frequency
fS
E
Startup Short-Circuit Time
1.8
0.1A P IOUT P 0.75A
Converter latch off
Thermal Shutdown
LX Leakage Current
2
0.5
TA = +25NC
-40NC P TA P +85NC
-1.0
V
A
3.3
A
10
mA
2.0
2.2
MHz
93
%
50
ms
165
VLX = 0V or 5.5V,
VCCOUT = 5.5V
V
A
0.3
pMOS Turn-Off Current Limit
V
ms
1.5
Output Current Limit
Efficiency
5.5
5.6
tON
+0.1
0.1
NC
+1.0
FA
Maxim Integrated MAX98500
带有自动电平控制的
2.2W升压型D类放大器
ELECTRICAL CHARACTERISTICS (continued)
(VBAT = 3.6V, RL = J between SPKP and SPKN, AV = +6dB, CIN = 1FF, 20Hz to 22kHz AC measurement bandwidth, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
1
3
mV
SPEAKER AMPLIFIER
Output Offset Voltage
Click-and-Pop Level
Output Power (Note 5)
Total Harmonic Distortion Plus
Noise
VOS
TA = +25NC
KCP
Peak voltage, TA =
+25NC, A-weighted, 32
samples per second,
ZSPK = 8I + 68FH,
(Notes 3, 4)
POUT
THD+N
ZSPK = 8I + 68FH
Into shutdown
-56
Out of shutdown
-56
dBV
THD+N P 1%
1.7
THD+N P 10%
2.2
f = 1kHz, POUT = 850mW, TA = +25NC,
ZSPK = 8I + 33FH
Output Switching Frequency
Gain
AV
%
300
kHz
GAIN = AGND
5.5
6
15
15.5
16
19.5
20
20.5
Output Current Limit
6.5
2
E
Output Noise
Input Resistance
0.05
GAIN = unconnected
GAIN = VBAT
Efficiency
W
RIN
Common-Mode Rejection Ratio
CMRR
Bias Voltage
VBIAS
dB
A
POUT = 1.7W, f = 1kHz, ZSPK = 8I + 68FH
92
%
A-weighted
43
FVRMS
SDBST = SDSPK =
VBAT
VSDBST = VSDSPK = 0V
f = 1kHz
AV = 6dB
(GAIN = AGND)
36
54
72
AV = 15.5dB
(GAIN =
unconnected)
12
18
26
AV = 20dB
(GAIN = VBAT)
6.5
11
16
All gain settings
kI
110
60
1.3
1.4
dB
1.5
V
ALC
Attack Time
20
Fs/dB
Release Time
1.6
s/dB
Maximum Attenuation
8
dB
Attenuation Resolution
0.5
Knee Voltage
Maxim Integrated
VKNEE
TA = +25NC
dB
RKNEE = 154kI
2.19
2.3
2.42
RKNEE = 40.5kI
3.14
3.3
3.47
RKNEE = 13kI
3.71
3.9
4.10
V
3
MAX98500
带有自动电平控制的
2.2W升压型D类放大器
ELECTRICAL CHARACTERISTICS (continued)
(VBAT = 3.6V, RL = J between SPKP and SPKN, AV = +6dB, CIN = 1FF, 20Hz to 22kHz AC measurement bandwidth, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
PARAMETER
Knee Resistor
SYMBOL
RKNEE
DIGITAL INPUTS (SDBST, SDSPK)
Input Voltage High
ViH
Input Voltage Low
VIL
Input Capacitance
CIN
Input Leakage Current
IIN
CONDITIONS
TA = +25NC,
AV = 15.5dB
MIN
TYP
VKNEE = 3.25V
43.2
VKNEE = 3.35V
37.4
VKNEE = 3.45V
32.4
VKNEE = 3.55V
27.4
VKNEE = 3.65V
23.2
VKNEE = 3.75V
18.7
VKNEE = 3.85V
15.0
MAX
kI
1.4
V
0.4
10
TA = +25NC
UNITS
V
pF
-1.0
+1.0
FA
Note 2: 100% production tested at TA = +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
Maxim Integrated MAX98500
带有自动电平控制的
2.2W升压型D类放大器
典型工作特性
(VBAT = 3.6V, RL = ∞ between SPKP and SPKN, AV = +15.5dB, RKNEE = VBAT, 20Hz to 22kHz AC measurement bandwidth, unless
otherwise noted.)
General
BATTERY CURRENT
vs. BATTERY VOLTAGE
INPUTS AC-COUPLED TO AGND
SDSPK = GND, SDBST = VBAT
BATTERY CURRENT (µA)
BATTERY CURRENT (mA)
4.0
140
MAX98500 toc02
INPUTS AC-COUPLED TO AGND
SDSPK = SDBST = VBAT
4.5
MAX98500 toc01
5.0
BATTERY CURRENT
vs. BATTERY VOLTAGE
3.5
3.0
2.5
2.0
1.5
1.0
120
100
80
0.5
60
0
2.5
3.0
3.5
4.0
4.5
5.0
3.5
4.0
4.5
BATTERY VOLTAGE (V)
BATTERY VOLTAGE (V)
BATTERY CURRENT
vs. BATTERY VOLTAGE
TURN-ON RESPONSE
5.0
5.5
MAX98500 toc04
MAX98500 toc03
10
INPUTS AC-COUPLED TO AGND
SDSPK = VBAT, SDBST = AGND
9
8
BATTERY CURRENT (µA)
3.0
2.5
5.5
SDBST
2V/div
7
OV
VCCOUT
2V/div
6
5
4
OV
3
2
SPKR
OUTPUT
1V/div
OV
1
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2ms/div
BATTERY VOLTAGE (V)
EFFICIENCY vs. OUTPUT POWER
MAX98500 toc05
100
90
EFFICIENCY (%)
80
VBAT = 4.2V
70
VBAT = 3.6V
60
50
VBAT = 3.0V
40
30
20
ZLOAD = 8I + 68µH
fIN = 1kHz
10
0
0
0.5
1.0
1.5
2.0
2.5
POUT (W)
Maxim Integrated
5
MAX98500
带有自动电平控制的
2.2W升压型D类放大器
典型工作特性(续)
(VBAT = 3.6V, RL = ∞ between SPKP and SPKN, AV = +15.5dB, RKNEE = VBAT, 20Hz to 22kHz AC measurement bandwidth, unless
otherwise noted.)
Speaker
MAX98500 toc06
ZLOAD = 8I + 68µH
1
ZLOAD = 8I + 68µH
10
POUT = 1.4W
THD+N (%)
THD+N (%)
100
MAX98500 toc07
THD+N vs. OUTPUT POWER
THD+N vs. FREQUENCY
10
0.1
1
f = 6kHz
0.1
f = 1kHz
POUT = 400mW
0.01
0.01
f = 100Hz
0.001
0.001
0.1
1
10
100
0
0.4
OUTPUT POWER vs. LOAD RESISTANCE
fIN = 1kHz
ZSPRK = LOAD + 68µF
THD+N = 10%
fIN = 1kHz
ZSPRK = 8I + 68µH
2.5
OUTPUT POWER (W)
OUTPUT POWER (W)
2.5
1.2
1.6
2.0
2.4
OUTPUT POWER vs. BATTERY VOLTAGE
3.0
MAX98500 toc08
3.0
0.8
OUTPUT POWER (W)
FREQUENCY (kHz)
2.0
1.5
THD+N = 1%
1.0
0.5
THD+N = 10%
MAX98500 toc09
0.01
2.0
1.5
THD+N = 1%
1.0
0.5
0
1
10
100
0
1000
2.5
3.0
LOAD RESISTANCE (I)
3.5
4.0
4.5
5.0
5.5
BATTERY VOLTAGE (V)
ZLOAD = 8I + 68µH
AV = 20dB
GAIN (dB)
20
10
AV = 15.5dB
0
AV = 6dB
MAX98500 toc10
GAIN vs. FREQUENCY
30
-10
-20
-30
-40
0.1
1
10
100
1000
FREQUENCY (kHz)
6
Maxim Integrated MAX98500
带有自动电平控制的
2.2W升压型D类放大器
典型工作特性(续)
(VBAT = 3.6V, RL = ∞ between SPKP and SPKN, AV = +15.5dB, RKNEE = VBAT, 20Hz to 22kHz AC measurement bandwidth, unless
otherwise noted.)
SPEAKER POWER-SUPPLY REJECTION
RATIO vs. FREQUENCY
-20
MAX98500 toc12
VRIPPLE AT PVDD = 200mVP-P
INPUTS AC-COUPLED AGND
SHUTDOWN RESPONSE
MAX98500 toc13
0
MAX98500 toc11
0
COMMON-MODE REJECTION RATIO
vs. FREQUENCY
ZLOAD = 8I + 68µH
-20
SDSPK
2V/div
-40
CMRR (dB)
PSRR (dB)
AV = 15.5dB
-40
-60
0V
AV = 6dB
-60
-80
-80
-100
-100
SPKR
OUTPUT
1V/div
0V
AV = 20dB
0.01
0.1
1
10
100
0.1
0.01
FREQUENCY (kHz)
1
10
100
40µs/div
FREQUENCY (kHz)
TURN-ON RESPONSE
CLIPPING RESPONSE
MAX98500 toc14
MAX98500 toc15
SDBST = VBAT
THD+N = 10%
SDSPK
2V/div
0V
SPKR
OUTPUT
500mV/div
0V
0V
SPKR
OUTPUT
1V/div
1ms/div
200µs/div
WIDEBAND OUTPUT SPECTRUM
-40
-60
-80
-40
-60
-80
-100
-100
-120
0.1
1
10
FREQUENCY (MHz)
Maxim Integrated
fIN = 1kHz
OUTPUT = -60dBV
-20
AMPLITUDE (dBV)
AMPLITUDE (dBV)
-20
MAX98500 toc17
RBW = 100Hz
AUDIO INPUTS AC-GROUNDED
0
INBAND OUTPUT SPECTRUM
0
MAX98500 toc16
20
100
1000
0
5
10
15
20
FREQUENCY (kHz)
7
MAX98500
带有自动电平控制的
2.2W升压型D类放大器
典型工作特性(续)
(VBAT = 3.6V, RL = ∞ between SPKP and SPKN, AV = +15.5dB, RKNEE = VBAT, 20Hz to 22kHz AC measurement bandwidth, unless
otherwise noted.)
Boost Converter
EFFICIENCY vs. OUTPUT CURRENT
0
94
92
VBAT = 4V
90
88
VBAT = 3.6V
86
VBAT = 3V
84
82
80
-0.2
VBAT = 4.2V
-0.4
VBAT = 4V
-0.6
-0.8
VBAT = 3.6V
-1.2
0
200 400 600 800 1000 1200 1400 1600
0
VBAT = 3.3V
VBAT = 3V
200 400 600 800 1000 1200 1400 1600
IOUT (mA)
IOUT (mA)
OUTPUT VOLTAGE vs. OUTPUT CURRENT
SWITCHING FREQUENCY
vs. BATTERY VOLTAGE
2.04
5.51
5.50
5.49
SWITCHING FREQUENCY (MHz)
MAX98500 toc20
5.52
OUTPUT VOLTAGE (V)
VBAT = 5V
-1.0
VBAT = 3.3V
MAX98500 toc19
VBAT = 5V
VBAT = 4.2V
5.48
VBAT = 5V
5.47
5.46
VBAT = 3V
5.45
2.02
IOUT = 100mA
2.00
IOUT = 500mA
1.98
VBAT = 3.3V
VBAT = 3.6V
5.44
0
MAX98500 toc21
EFFICIENCY (%)
96
LOAD REGULATION (%)
VBAT = 4.2V
98
LOAD REGULATION vs. OUTPUT CURRENT
0.2
MAX98500 toc18
100
1.96
200 400 600 800 1000 1200 1400 1600
2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5
IOUT (A)
BATTERY VOLTAGE (V)
SOFT-START
MAX98500 toc22
SDBST
2V/div
0V
VCCOUT
2V/div
0V
1ms/div
8
Maxim Integrated MAX98500
带有自动电平控制的
2.2W升压型D类放大器
引脚配置
TOP VIEW
(BUMP SIDE DOWN)
MAX98500
1
2
3
4
A
PVDD
VCCOUT
LX
BSTPGND
B
SPKP
GAIN
RKNEE
VBAT
C
SPKN
SPKPGND
SDSPK
AGND
D
SPKPGND
INP
INN
SDBST
+
WLP
引脚说明
焊球
名称
A1
PVDD
A2
VCCOUT
A3
LX
A4
BSTPGND
B1
SPKP
B2
GAIN
B3
RKNEE
B4
VBAT
功能
扬声器放大器电源，利用0.1μF电容旁路至SPKPGND。
Boost转换器输出，在VCCOUT和BSTPGND之间连接22μF (0805)电容。
Boost开关输入。
Boost电源地。
扬声器输出正端。
增益选择输入。将GAIN连接至地，扬声器增益设置为6dB；保持GAIN浮空，扬声器增益设置
为15.5dB；将GAIN连接至VBAT，扬声器增益设置为20dB。
ALC拐点电压设置输入。利用连接至AGND的电阻设置ALC拐点电压。
电池电压输入。在VBAT和BSTPGND之间连接10μF (0805)电容，至少包括22μF的系统大容量
电容。
C1
SPKN
C2, D1
SPKPGND
C3
C4
SDSPK
AGND
D2
INP
音频输入正端。
D3
INN
音频输入负端。
D4
SDBST
Maxim Integrated
扬声器输出负端。
扬声器地。
扬声器输出关断。驱动SDSPK为低电平，关断扬声器输出。
模拟地。
Boost转换器关断。驱动SDBST为低电平，关断boost转换器和扬声器输出。
9
MAX98500
带有自动电平控制的
2.2W升压型D类放大器
详细说明
MAX98500是 高 效 率、D类 音 频 放 大 器， 器 件 内 部 集 成
boost转换器，在较宽的电池供电电压范围内提供恒定的
输出功率。Boost转换器工作在2MHz，只需小尺寸外部电
感(2.2μH)和输出电容。放大器采用差分输入和内部全差分
设计，具有三个增益设置(6dB、15.5dB和20dB)，可通过
逻辑输入进行选择。
MAX98500还具有自动电平控制。电池电压下降时，自动
电平控制降低输出摆幅，防止电池电压失效。
低EMI无滤波输出级
传 统D类 放 大 器 要 求 使 用 外 部LC滤 波 或 屏 蔽， 以 满 足
EN55022B电磁干扰(EMI)规范标准。Maxim的有源辐射抑
制电路可有效降低EMI辐射，同时维持高达92%的效率(仅
限扬声器)。10MHz以上时，宽带频谱类似EMI噪声。
自动电平控制
PEAK AMPLIFIER OUTPUT VOLTAGE
vs. BATTERY VOLTAGE
MAX98500具有自动电平控制电路，用于限制扬声器最大
输出摆幅。这有助于：
6
PEAK AMPLIFIER OUTPUT VOLTAGE (VPEAK)
D类扬声器放大器
MAX98500无滤波D类放大器的效率比AB类放大器高得
多。D类放大器的高效率得益于输出级晶体管的开关工作。
与D类放大器输出级相关的功率损耗主要是MOSFET导通
电阻和静态电流开销的I2R损耗。
U 避免发生削波
5
SLOPE
U 避免电池失效，以免造成系统复位
4
KNEE VOLTAGE
限幅器使峰值电压保持在某个电平以下，该电平是电池电
压的函数，如图1所示。
3
电池电压降到拐点电压时，维持5.2V的满摆幅输出；电池
电压更低时，最高VPEAK摆幅按照3V/V减小。
2
1
在RKNEE和AGND之间连接不同的电阻，可更改拐点电压。
典型跟踪函数随RKNEE电阻值不同而发生平移(图2)。
0
0
1
2
3
4
5
6
BATTERY VOLTAGE (V)
图1. 典型跟踪函数
自动电平控制激活时，前置放大器增益降低。增益最多降
低8dB，步长为0.5dB。
衰减(增益降低)可立即启动(20μs/dB)，释放状态则置为
1.6s/dB。
增益选择
VKNEE vs. RKNEE
4.0
MAX98500具有三种内部增益设置，通过GAIN输入进行
选择。表1所示为增益设置。
3.9
3.8
VKNEE (V)
3.7
表1. 增益设置
3.6
3.5
GAIN
3.4
AMPLIFIER GAIN (dB)
AGND
6
3.2
Unconnected
15.5
3.1
VBAT
20
3.3
3.0
2.9
10
20
30
40
50
60
70
RKNEE (kI)
图2. RKNEE和VKNEE的关系曲线
10
Maxim Integrated MAX98500
带有自动电平控制的
2.2W升压型D类放大器
表2. 关断配置
SDBST
SDSPK
BOOST
STATUS
SPEAKER
STATUS
Low
Low
Off
Off
Low
High
Off
Off
High
Low
On
Off
High
High
On
On
应用信息
无需滤波的D类放大器
关断
MAX98500具 有 两 个 低 电 平 有 效 的 关 断 输 入(SDSPK和
SDBST)。表2给出了不同的关断配置。
咔嗒/噼噗声抑制
MAX98500扬声器放大器采用Maxim专有的咔嗒/噼噗声
抑制。启动期间，咔嗒/噼噗声抑制电路可降低器件内部所
有可闻瞬态源。进入关断时，差分扬声器输出同时快速降
至SPKPGND。
限流和热保护
IC具有过流和热保护。VCCOUT输出降至规定输出的大约
80%时，IC关断。管芯温度超过+165°C时，IC也进入关
断状态。故障条件消除后，器件重新上电或将SDBST触发
为低电平然后再置高，可使器件退出关断状态。IC扬声器
放大器也具有2A (典型值)短路保护机制。
Boost转换器
软启动
MAX98500具有两级软启动上电顺序控制。SDBST为高电
平且VBAT高于UVLO时，软启动首先使VCCOUT快速上升至
VBAT电压，电池电流为300mA (典型值)。一旦VCCOUT达
到VBAT电压，内部开关导通，使VCCOUT在5ms (典型值)
内上升至5.5V，参见典型工作特性中的软启动图 。软启动
完成后，可提供最大负载电流。
Maxim Integrated
欠压锁定(UVLO)
欠压锁定(UVLO)电路将VBAT电压与UVLO门限(典型值为
2.2V)进行比较，确保输入电压足以维持可靠工作。一旦
VBAT电压超过UVLO门限，则开启软启动。输入电压降至
UVLO门限以下时，boost转换器和扬声器放大器关闭。
传统的D类放大器需要输出滤波器，从放大器的输出恢复
音频信号。滤波器增加成本、增大放大器方案尺寸，并会
降低效率和THD+N性能。传统的PWM方法采用较大的差
分输出摆幅(2 x 电源电压峰峰值)，并产生大纹波电流。滤
波器元件中的任何寄生电阻都会造成功率损耗，降低效率。
MAX98500无需输出滤波器。器件依赖于扬声器线圈的固
有电感及扬声器和人耳的天然滤波特性，恢复方波输出的
音频成分。由于省去了输出滤波器，使得方案的尺寸更小、
成本更低、效率更高。
由于MAX98500输出波形的频率超过绝大多数扬声器的带
宽，方波频率造成的音圈移动非常小。尽管移动非常小，
额外功率也有可能导致扬声器损坏。采用串联电感大于
10μH的扬声器可获得最佳结果。典型的8Ω扬声器的串联
电感在20μH至100μH范围内。
RF敏感度
GSM无线信号按照时分多址(TDMA)以217Hz间隔发射，
导致RF信号在217Hz具有较强的幅度调制，其谐波很容易
被音频放大器解调。MAX98500特别针对抑制射频信号进
行设计；而PCB布局对最终产品的RF敏感度影响很大。
射频应用中，改善布局及元件选择可减小MAX98500对射
频噪声的敏感度，防止射频信号被解调为可闻噪声。走线
长度应保持短于敏感射频波长的1/4。将走线长度最小化，
防止走线形成天线并将射频信号耦合进MAX98500。以米
为单位的波长(λ)由下式给出：λ = c/f，
其中c = 3 x 108 m/s，
f = 敏感射频频率。
11
MAX98500
带有自动电平控制的
2.2W升压型D类放大器
将音频信号布设在PCB的中间层，使上、下层接地区域提
供良好的屏蔽，防止射频干扰。理想情况下，PCB的顶层
和底层应主要为接地区域，产生有效屏蔽。
由于电容的频率响应与陷波滤波器相似，利用电容的自
谐振频率可以获得更好的射频抑制。根据制造商的不同，
10pF至20pF电容通常在射频频率处呈现自谐振。将这些
电容安装在输入引脚时，可在MAX98500输入端有效抑制
射频噪声。为了使这些电容有效工作，它们必须与地平面
间具有低阻、低电感通路。请勿使用微过孔连接至接地区
域，因为这些过孔在射频频率下传导不良。
扬声器元件选择
磁珠滤波器(可选)
采用磁珠及接地电容的滤波器结构，可进一步改善EMI抑
制(图3)。磁珠应具有较低的直流电阻，高频(> 100MHz)
阻抗介于100Ω至600Ω，额定电流至少为1A。根据所选的
磁珠及实际扬声器引线长度选择电容。按照EMI性能要求，
选择小于1μF的电容即可。
输入电容(CIN)
输入电容CIN与MAX98500扬声器输入端的输入阻抗形成
高通滤波器，消除模拟输入信号中的直流偏压。交流耦合
电容允许放大器自动偏置至最优直流电平。假定源阻抗为
零，高通滤波器的-3dB点由下式给出：
f-3dB =
1
2πRINCIN
选择CIN，使f-3dB低于感兴趣的最低频率。为了获得最佳
音质，使用具有低电压系数的电介质电容，例如钽电容或
铝电解电容。具有高电压系数的电容，例如陶瓷电容，低
频时可能会增大失真。
Boost转换器元件选择
电感选择
大多数升压转换器设计中，可以从下式得出合理的电感值。
该式将电感电流峰峰值设置为直流电感电流的1/2：
L = (2 x VBATT x D x (1-D))/(IOUT(MAX) x fSW)
式 中，fSW为 开 关 频 率，D为 由D = 1 - (VBAT/VOUT)得 出
的占空比。使用上式计算L，得到的电感电流峰峰值纹波
为0.5x IOUT/(1 - D)，峰值电感电流为1.25 x IOUT/(1 - D)。
确保电感峰值(饱和)电流额定值满足或超过该要求。
推荐MAX98500的标称电感为2.2μH。电感电流上升时，
标称电感下降。如果标称电感下降很严重，boost转换器
在输出功率比预期值低时可能变得不稳定，甚至关断。确
保峰值电感电流时的最小电感为1.0μH。
输出电容(CVCCOUT)
为使输出电压纹波较小，以及确保调节环路稳定，需要输
出电容CVCCOUT。输出电容必须在开关频率处具有低阻抗。
由于陶瓷电容尺寸小且ESR低，因此强烈建议使用陶瓷电
容。温度特性为X5R或X7R的陶瓷电容通常表现良好。推
荐MAX98500的标称电容为22μF (0805外壳尺寸或更大)。
确保5.5V下的最小电容为6.8μF。
输入电容(CVBAT)
输入电容CVBAT降低从电池或输入电源吸收的电流峰值，
以及降低IC中的开关噪声。输入电容在开关频率处的阻
抗应非常低。由于陶瓷电容尺寸小且ESR低，因此强烈建
议使用陶瓷电容。温度特性为X5R或X7R的陶瓷电容通常
表现良好。建议使用一个10μF陶瓷电容，系统总电容为
22μF或更大。
MAX98500
SPKP
SPKN
图3. 可选D类磁珠滤波器
12
Maxim Integrated MAX98500
带有自动电平控制的
2.2W升压型D类放大器
电源旁路、布局和接地
利用10μF电容和22μF或更大的系统总电容旁路VBAT。利
用0.1μF电容将PVDD旁路至SPKPGND，环路面积尽可能
小。尽量使用短且宽的走线，将SPKP和SPKN连接至扬
声器。降低走线长度可使辐射EMI最小化。在PCB上将
SPKP/SPKN作为差分对，将环路面积最小化，进而将电
路电感最小化。如果在扬声器输出上使用滤波元件，确保
使其尽量靠近MAX98500，保证最大效果。将任何接地无
源元件与SPKPGND的连接走线长度最小化，进一步减小
EMI。
合理的布局和接地对获得最佳性能至关重要。在PCB的专
用接地层上使用大面积连续地平面，使环路面积最小。采
用尽可能短的走线将AGND和BSTPGND/SPKPGND直接
连接至接地区域。合理的接地可改善音频性能，防止数字
噪声耦合至模拟音频信号。
0.25mm
现备有评估板(MAX98500评估板)，可作为MAX98500的
PCB布局实例。
WLP应用信息
关 于WLP结 构、 尺 寸、 载 带 信 息、PCB工 艺、 焊 球-焊
盘布局以及推荐的回流焊温度特性的最新应用信息，以
及可靠性测试结果的最新信息，请参考Maxim网站china.
maximintegrated.com/ucsp的应用笔记1891：晶片级封装
(WLP)及其应用 。关于推荐的MAX98500 PCB占位面积，
参见图4。
0.22mm
图4. 推荐的PCB占位面积
典型应用电路
2.2µH
20%
BATTERY
22µF*
CVBAT
10µF
0805
10%
LX
VBAT
B4
BOOST CONVERTER
SDBST D4
SDSPK C3
GAIN B2
A3
CONTROL
MAX98500
A2 VCCOUT
A1 PVDD
RKNEE B3
27.4kI
1%
CIN
1µF
INP D2
INN D3
CIN
1µF
CVCCOUT
22µF
0805
10%
0.1µF
10%
B1 SPKP
DIFFERENTIAL
INPUT
C4
AGND
GAIN
A4
BSTPGND
OUTPUT
STAGE
C1 SPKN
8I
D1, C2
SPKPGND
*SYSTEM LEVEL REQUIREMENT
Maxim Integrated
13
MAX98500
带有自动电平控制的
2.2W升压型D类放大器
封装信息
如需最近的封装外形信息和焊盘布局，请查询china.maximintegrated.com/packages。请注意，封装编码中的“+”、“#”或“-”仅
表示RoHS状态。封装图中可能包含不同的尾缀字符，但封装图只与封装有关，与RoHS状态无关。
14
封装类型
封装编码
文件编号
16 WLP
W162B2+1
21-0200
Maxim Integrated MAX98500
带有自动电平控制的
2.2W升压型D类放大器
修订历史
修订号
修订日期
0
5/10
说明
最初版本。
修改页
—
Maxim北京办事处
北京8328信箱 邮政编码100083
免费电话：800 810 0310
电话：010-6211 5199
传真：010-6211 5299
Maxim不对Maxim产品以外的任何电路使用负责，也不提供其专利许可。Maxim保留在任何时间、没有任何通报的前提下修改产品资料和规格的权利。
Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-10 00
© 2010 Maxim Integrated
15
Maxim标志和Maxim Integrated是Maxim Integrated Products, Inc.的商标。
19-5189; Rev 0; 5/10
Boosted 2.2W Class D Amplifier
with Automatic Level Control
Features
The MAX98500 is a high-efficiency, Class D audio amplifier that features an integrated boost converter to deliver
a constant output power over a wide range of battery
supply voltages.
S Boosted Class D Output
S Integrated Automatic Level Control
S Output Power
2.2W into 8I, 10% THD+N
1.7W into 8I, 1% THD+N
The boost converter operates at 2MHz, requiring only a
small (2.2FH) external inductor and capacitor.
S Wide 2.5V to 5.5V Supply Voltage Range
The automatic level control has a battery tracking function that reduces the output swing as the supply voltage
drops, preventing collapse of battery voltage.
S Undervoltage Lockout Protection
S High Total Efficiency of 87%
S High Step-Up Switching Frequency (2MHz)
The amplifier has differential inputs and an internal fully
differential design. The MAX98500 also features three
gain settings (6dB, 15.5dB, and 20dB) that are selectable with a logic input.
S Active Emission Limiting for Low EMI
The MAX98500 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.
Ordering Information
Applications
Cell Phones
PART
Smartphones
TEMP RANGE
PIN-PACKAGE
MAX98500EWE+
16 WLP
-40NC to +85NC
+Denotes a lead(Pb)-free/RoHS-compliant package.
GPS Devices
Mobile Internet Devices
Typical Application Circuit appears at end of data sheet.
Active Speaker Accessories
Simplified Block Diagram
BATTERY
VBAT
LX
B4
SDBST D4
SDSPK C3
GAIN B2
RKNEE
A3
BOOST CONVERTER
CONTROL
MAX98500
A2
VCCOUT
A1 PVDD
B3
INP D2
INN D3
B1 SPKP
DIFFERENTIAL
INPUT
C4
AGND
OUTPUT
STAGE
GAIN
A4
BSTPGND
C1 SPKN
D1, C2
SPKPGND
________________________________________________________________ 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.
MAX98500
General Description
MAX98500
Boosted 2.2W Class D Amplifier
with Automatic Level Control
ABSOLUTE MAXIMUM RATINGS
Duration of SPK_ Short Circuit to PVDD or
SPKPGND...............................................................Continuous
Duration of Short Circuit Between SPKP
and SPKN...............................................................Continuous
Continuous Power Dissipation, Multilayer Board (TA = +70NC)
WLP (derate 20.4mW/NC above +70NC)........................1.33W
θJA (Note 1).................................................................49NC/W
Junction Temperature......................................................+150NC
Operating Temperature Range........................... -40NC to +85NC
Storage Temperature Range............................. -65NC to +150NC
Soldering Temperature (reflow).......................................+260NC
VBAT to AGND..........................................................-0.3V to +6V
VCCOUT 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 (VBAT + 0.3V)
SDBST, SDSPK to AGND....................................... -0.3V to VBAT
All Other Pins (excluding LX) to AGND...................-0.3V to +6V
Current Into/Out of LX, VCCOUT, BSTPGND...................... Q3.9A
Continuous Current Into/Out of SPK_, PVDD,
SPKPGND................................................................... Q800mA
Continuous Input Current (all other pins)......................... Q20mA
Duration of Short Circuit Between VCCOUT
and BSTPGND....................................................... Continuous
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer 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
(VBAT = 3.6V, RL = J between SPKP and SPKN, AV = +6dB, CIN = 1FF, 20Hz to 22kHz AC measurement bandwidth, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
PARAMETER
Power-Supply Rejection Ratio
(Note 3)
SYMBOL
PSRR
IVBAT
Quiescent Current
IPVDD
Combined Efficiency
Shutdown Current
Turn-On Time
E
ISHDN
tON
CONDITIONS
MIN
TYP
MAX
95
TA = +25NC, VBAT = 2.5V to 5.5V
dB
TA = +25NC, SDSPK = SDBST = VBAT
3.05
TA = +25NC, VSDSPK = 0V, SDBST = VBAT
0.09
0.15
TA = +25NC, PVDD = 5.55V, SDSPK =
SDBST = VBAT
1.7
2.7
87
POUT = 1.7W, f = 1kHz, ZSPK = 8I + 68FH
VSDSPK = VSDBST = 0V, TA = +25NC
Time from power-on to full operation
UNITS
mA
%
0.04
1.5
FA
10
12
ms
BOOST CONVERTER
Battery Supply Voltage Range
Soft-Start Interval
Undervoltage Lockout
Boost Converter Output Voltage
Output Current Limit
2.5
VBAT
UVLO
VBAT falling
VVCCOUT ILOAD = 0mA
VBAT R = 3.6V
Input Current Limit
ILIMIT
Startup, VCCOUT = 0V
nMOS Current Limit
ILX,MAX
2.1
2.2
2.3
5.45
5.5
5.65
fS
Efficiency
E
1.8
V
2.0
A
A
mA
2.2
MHz
0.1A P IOUT P 0.75A
93
%
Converter latch off
50
ms
Thermal Shutdown
LX Leakage Current
0.5
3.3
10
Switching Frequency
V
A
0.3
pMOS Turn-Off Current Limit
V
ms
1.5
IMAX
Startup Short-Circuit Time
5.5
5.6
tON
165
VLX = 0V or 5.5V,
VCCOUT = 5.5V
TA = +25NC
-40NC P TA P +85NC
-1.0
+0.1
0.1
2 _______________________________________________________________________________________
NC
+1.0
FA
Boosted 2.2W Class D Amplifier
with Automatic Level Control
(VBAT = 3.6V, RL = J between SPKP and SPKN, AV = +6dB, CIN = 1FF, 20Hz to 22kHz AC measurement bandwidth, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
1
3
mV
SPEAKER AMPLIFIER
Output Offset Voltage
Click-and-Pop Level
Output Power (Note 5)
Total Harmonic Distortion Plus
Noise
VOS
TA = +25NC
KCP
Peak voltage, TA =
+25NC, A-weighted, 32
samples per second,
ZSPK = 8I + 68FH,
(Notes 3, 4)
POUT
THD+N
ZSPK = 8I + 68FH
Into shutdown
-56
Out of shutdown
-56
dBV
THD+N P 1%
1.7
THD+N P 10%
2.2
f = 1kHz, POUT = 850mW, TA = +25NC,
ZSPK = 8I + 68FH
Output Switching Frequency
Gain
AV
%
300
kHz
GAIN = AGND
5.5
6
15
15.5
16
19.5
20
20.5
Output Current Limit
6.5
2
E
Output Noise
Input Resistance
0.05
GAIN = unconnected
GAIN = VBAT
Efficiency
W
RIN
Common-Mode Rejection Ratio
CMRR
Bias Voltage
VBIAS
dB
A
POUT = 1.7W, f = 1kHz, ZSPK = 8I + 68FH
92
%
A-weighted
43
FVRMS
SDBST = SDSPK =
VBAT
VSDBST = VSDSPK = 0V
f = 1kHz
AV = 6dB
(GAIN = AGND)
36
54
72
AV = 15.5dB
(GAIN =
unconnected)
12
18
26
AV = 20dB
(GAIN = VBAT)
6.5
11
16
All gain settings
kI
110
60
1.3
1.4
dB
1.5
V
ALC
Attack Time
20
Fs/dB
Release Time
1.6
s/dB
Maximum Attenuation
8
dB
Attenuation Resolution
0.5
Knee Voltage
VKNEE
TA = +25NC
dB
RKNEE = 154kI
2.19
2.3
2.42
RKNEE = 40.5kI
3.14
3.3
3.47
RKNEE = 13kI
3.71
3.9
4.10
V
_______________________________________________________________________________________ 3
MAX98500
ELECTRICAL CHARACTERISTICS (continued)
MAX98500
Boosted 2.2W Class D Amplifier
with Automatic Level Control
ELECTRICAL CHARACTERISTICS (continued)
(VBAT = 3.6V, RL = J between SPKP and SPKN, AV = +6dB, CIN = 1FF, 20Hz to 22kHz AC measurement bandwidth, TA = TMIN to
TMAX, unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
PARAMETER
Knee Resistor
SYMBOL
RKNEE
DIGITAL INPUTS (SDBST, SDSPK)
Input Voltage High
ViH
Input Voltage Low
VIL
Input Capacitance
CIN
Input Leakage Current
IIN
CONDITIONS
TA = +25NC,
AV = 15.5dB
MIN
TYP
VKNEE = 3.25V
43.2
VKNEE = 3.35V
37.4
VKNEE = 3.45V
32.4
VKNEE = 3.55V
27.4
VKNEE = 3.65V
23.2
VKNEE = 3.75V
18.7
VKNEE = 3.85V
15.0
MAX
kI
1.4
V
0.4
10
TA = +25NC
UNITS
-1.0
Note 2: 100% production tested at TA = +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 _______________________________________________________________________________________
V
pF
+1.0
FA
Boosted 2.2W Class D Amplifier
with Automatic Level Control
General
BATTERY CURRENT
vs. BATTERY VOLTAGE
INPUTS AC-COUPLED TO AGND
SDSPK = GND, SDBST = VBAT
BATTERY CURRENT (µA)
BATTERY CURRENT (mA)
4.0
140
MAX98500 toc02
INPUTS AC-COUPLED TO AGND
SDSPK = SDBST = VBAT
4.5
MAX98500 toc01
5.0
BATTERY CURRENT
vs. BATTERY VOLTAGE
3.5
3.0
2.5
2.0
1.5
1.0
120
100
80
0.5
60
0
2.5
3.0
3.5
4.0
4.5
5.0
3.5
4.0
4.5
BATTERY VOLTAGE (V)
BATTERY VOLTAGE (V)
BATTERY CURRENT
vs. BATTERY VOLTAGE
TURN-ON RESPONSE
5.0
5.5
MAX98500 toc04
MAX98500 toc03
10
INPUTS AC-COUPLED TO AGND
SDSPK = VBAT, SDBST = AGND
9
8
SDBST
2V/div
7
OV
VCCOUT
2V/div
6
5
4
OV
3
2
SPKR
OUTPUT
1V/div
OV
1
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2ms/div
BATTERY VOLTAGE (V)
EFFICIENCY vs. OUTPUT POWER
MAX98500 toc05
100
90
80
EFFICIENCY (%)
BATTERY CURRENT (µA)
3.0
2.5
5.5
VBAT = 4.2V
70
VBAT = 3.6V
60
50
VBAT = 3.0V
40
30
20
ZLOAD = 8I + 68µH
fIN = 1kHz
10
0
0
0.5
1.0
1.5
2.0
2.5
POUT (W)
_______________________________________________________________________________________ 5
MAX98500
Typical Operating Characteristics
(VBAT = 3.6V, RL = ∞ between SPKP and SPKN, AV = +15.5dB, RKNEE = VBAT, 20Hz to 22kHz AC measurement bandwidth, unless
otherwise noted.)
Typical Operating Characteristics (continued)
(VBAT = 3.6V, RL = ∞ between SPKP and SPKN, AV = +15.5dB, RKNEE = VBAT, 20Hz to 22kHz AC measurement bandwidth, unless
otherwise noted.)
Speaker
MAX98500 toc06
ZLOAD = 8I + 68µH
1
ZLOAD = 8I + 68µH
10
POUT = 1.4W
THD+N (%)
THD+N (%)
100
MAX98500 toc07
THD+N vs. OUTPUT POWER
THD+N vs. FREQUENCY
10
0.1
1
f = 6kHz
0.1
f = 1kHz
POUT = 400mW
0.01
0.01
f = 100Hz
0.001
0.001
0.1
1
10
100
0
0.4
OUTPUT POWER vs. LOAD RESISTANCE
fIN = 1kHz
ZSPRK = LOAD + 68µF
2.5
1.2
1.6
2.0
2.4
fIN = 1kHz
ZSPRK = 8I + 68µH
2.5
OUTPUT POWER (W)
THD+N = 10%
OUTPUT POWER vs. BATTERY VOLTAGE
3.0
MAX98500 toc08
3.0
0.8
OUTPUT POWER (W)
FREQUENCY (kHz)
2.0
1.5
THD+N = 1%
1.0
0.5
THD+N = 10%
MAX98500 toc09
0.01
OUTPUT POWER (W)
2.0
1.5
THD+N = 1%
1.0
0.5
0
1
10
100
0
1000
2.5
3.0
LOAD RESISTANCE (I)
3.5
4.0
4.5
5.0
BATTERY VOLTAGE (V)
ZLOAD = 8I + 68µH
AV = 20dB
20
10
AV = 15.5dB
0
AV = 6dB
MAX98500 toc10
GAIN vs. FREQUENCY
30
GAIN (dB)
MAX98500
Boosted 2.2W Class D Amplifier
with Automatic Level Control
-10
-20
-30
-40
0.1
1
10
100
1000
FREQUENCY (kHz)
6 _______________________________________________________________________________________
5.5
Boosted 2.2W Class D Amplifier
with Automatic Level Control
SPEAKER POWER-SUPPLY REJECTION
RATIO vs. FREQUENCY
-20
MAX98500 toc12
VRIPPLE AT PVDD = 200mVP-P
INPUTS AC-COUPLED AGND
SHUTDOWN RESPONSE
MAX98500 toc13
0
MAX98500 toc11
0
COMMON-MODE REJECTION RATIO
vs. FREQUENCY
ZLOAD = 8I + 68µH
-20
SDSPK
2V/div
-40
CMRR (dB)
-60
0V
AV = 6dB
-60
-80
-80
-100
-100
SPKR
OUTPUT
1V/div
0V
AV = 20dB
0.1
1
10
100
0.1
0.01
FREQUENCY (kHz)
1
10
100
40µs/div
FREQUENCY (kHz)
TURN-ON RESPONSE
CLIPPING RESPONSE
MAX98500 toc14
MAX98500 toc15
SDBST = VBAT
THD+N = 10%
SDSPK
2V/div
0V
SPKR
OUTPUT
500mV/div
0V
0V
SPKR
OUTPUT
1V/div
1ms/div
200µs/div
WIDEBAND OUTPUT SPECTRUM
RBW = 100Hz
AUDIO INPUTS AC-GROUNDED
-20
-40
-60
-80
fIN = 1kHz
OUTPUT = -60dBV
-20
AMPLITUDE (dBV)
0
INBAND OUTPUT SPECTRUM
0
MAX98500 toc17
20
MAX98500 toc16
0.01
AMPLITUDE (dBV)
PSRR (dB)
AV = 15.5dB
-40
-40
-60
-80
-100
-100
-120
0.1
1
10
FREQUENCY (MHz)
100
1000
0
5
10
15
20
FREQUENCY (kHz)
_______________________________________________________________________________________ 7
MAX98500
Typical Operating Characteristics (continued)
(VBAT = 3.6V, RL = ∞ between SPKP and SPKN, AV = +15.5dB, RKNEE = VBAT, 20Hz to 22kHz AC measurement bandwidth, unless
otherwise noted.)
Typical Operating Characteristics (continued)
(VBAT = 3.6V, RL = ∞ between SPKP and SPKN, AV = +15.5dB, RKNEE = VBAT, 20Hz to 22kHz AC measurement bandwidth, unless
otherwise noted.)
Boost Converter
EFFICIENCY vs. OUTPUT CURRENT
0
94
92
VBAT = 4V
90
88
VBAT = 3.6V
86
VBAT = 3V
84
82
VBAT = 5V
-0.2
VBAT = 4.2V
-0.4
VBAT = 4V
-0.6
-0.8
VBAT = 3.6V
-1.0
VBAT = 3.3V
80
-1.2
0
MAX98500 toc19
VBAT = 5V
200 400 600 800 1000 1200 1400 1600
0
VBAT = 3.3V
VBAT = 3V
200 400 600 800 1000 1200 1400 1600
IOUT (mA)
IOUT (mA)
OUTPUT VOLTAGE vs. OUTPUT CURRENT
SWITCHING FREQUENCY
vs. BATTERY VOLTAGE
2.04
5.51
5.50
5.49
SWITCHING FREQUENCY (MHz)
MAX98500 toc20
5.52
VBAT = 4.2V
5.48
VBAT = 5V
5.47
5.46
VBAT = 3V
5.45
2.02
IOUT = 100mA
2.00
IOUT = 500mA
1.98
VBAT = 3.3V
VBAT = 3.6V
5.44
0
MAX98500 toc21
EFFICIENCY (%)
96
LOAD REGULATION (%)
VBAT = 4.2V
98
LOAD REGULATION vs. OUTPUT CURRENT
0.2
MAX98500 toc18
100
OUTPUT VOLTAGE (V)
MAX98500
Boosted 2.2W Class D Amplifier
with Automatic Level Control
1.96
200 400 600 800 1000 1200 1400 1600
2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5
IOUT (A)
BATTERY VOLTAGE (V)
SOFT-START
MAX98500 toc22
SDBST
2V/div
0V
VCCOUT
2V/div
0V
1ms/div
8 _______________________________________________________________________________________
Boosted 2.2W Class D Amplifier
with Automatic Level Control
TOP VIEW
(BUMP SIDE DOWN)
MAX98500
1
2
3
4
A
PVDD
VCCOUT
LX
BSTPGND
B
SPKP
GAIN
RKNEE
VBAT
C
SPKN
SPKPGND
SDSPK
AGND
D
SPKPGND
INP
INN
SDBST
+
WLP
Pin Description
BUMP
NAME
A1
PVDD
A2
VCCOUT
FUNCTION
Speaker Amplifier Power Supply. Bypass to SPKPGND with a 0.1mF capacitor.
Boost Converter Output. Connect a 22mF (0805) capacitor between VCCOUT and
BSTPGND.
Boost Switch Input
A3
LX
A4
BSTPGND
B1
SPKP
Positive Speaker Output
B2
GAIN
Gain Select Input. Connect GAIN to ground to set the speaker gain to 6dB. Leave GAIN
unconnected to set the speaker gain to 15.5dB. Connect GAIN to VBAT to set the speaker
gain to 20dB.
B3
RKNEE
B4
VBAT
C1
SPKN
C2, D1
SPKPGND
C3
SDSPK
AGND
C4
Boost Power Ground
ALC Knee Voltage Set Input. Set the ALC knee voltage with a resistor to AGND.
Battery Voltage Input. Connect a 10mF (0805) capacitor between VBAT and BSTPGND.
Include at least 22mF of system bulk capacitance.
Negative Speaker Output
Speaker Ground
Speaker Output Shutdown. Drive SDSPK low to shutdown the speaker output.
Analog Ground
D2
INP
Positive Audio Input
D3
INN
Negative Audio Input
D4
SDBST
Boost Converter Shutdown. Drive SDBST low to shutdown the boost converter and the
speaker output.
_______________________________________________________________________________________ 9
MAX98500
Pin Configuration
Detailed Description
The MAX98500 is a high-efficiency Class D audio amplifier that features an integrated boost converter to deliver a
constant output power over a large range of battery supply
voltages. The boost converter operates at 2MHz, requiring
only a small (2.2FH) external inductor and output capacitor. The amplifier has differential inputs and an internal fully
differential design with three gain settings (6dB, 15.5dB,
and 20dB) that are selectable with a logic input.
The MAX98500 also features automatic level control. The
automatic level control reduces the output swing when
the battery voltage decreases to prevent the collapse of
battery voltage.
PEAK AMPLIFIER OUTPUT VOLTAGE
vs. BATTERY VOLTAGE
PEAK AMPLIFIER OUTPUT VOLTAGE (VPEAK)
Low-EMI Filterless Output Stage
Traditional Class D amplifiers require the use of external
LC filters, or shielding, to meet EN55022B electromagnetic-interference (EMI) regulation standards. Maxim’s
active emissions limiting edge-rate control circuitry
reduces EMI emissions, while maintaining up to 92%
efficiency (speaker only). Above 10MHz, the wideband
spectrum looks like noise for EMI purposes.
The MAX98500 features an automatic level control circuit
that limits the maximum speaker output swing. This helps:
5
U Avoid clipping
SLOPE
4
KNEE VOLTAGE
U Save the battery from collapsing, which could cause
a reset of the system
3
The limiter keeps the peak voltage below a value that is a
function of battery voltage, as shown in Figure 1.
2
1
0
0
1
2
3
4
5
6
BATTERY VOLTAGE (V)
Figure 1. Typical Tracking Function
The full output swing of 5.2V is maintained for battery
voltages down to the knee voltage, while for lower battery
voltages the maximum VPEAK-swing is reduced by 3V/V.
The knee voltage can be changed by applying different
resistors between RKNEE and AGND. The typical tracking function is shifted horizontally with different RKNEE
resistor values (Figure 2).
The preamplifier gain reduces as the automatic level
control activates. The maximum gain reduction is 8dB
with a resolution of 0.5dB steps.
VKNEE vs. RKNEE
4.0
3.9
The attack (gain reduction) happens immediately (20Fs/
dB), while the release is set to 1.6s/dB.
3.8
3.7
3.6
GAIN Select
3.5
The MAX98500 features three internal gain settings that
are selectable with the GAIN input. Table 1 shows the
gain settings.
3.4
3.3
3.2
3.1
Table 1. Gain Settings
3.0
2.9
10
20
30
40
50
60
RKNEE (kI)
Figure 2. The Relationship of RKNEE and VKNEE
10
Class D Speaker Amplifier
The MAX98500 filterless Class D amplifier offers much
higher efficiency than Class AB amplifiers. The high
efficiency of a Class D amplifier is due to the switching
operation of the output stage transistors. Any power loss
associated with the Class D output stage is mostly due to
the I2R loss of the MOSFET on-resistance and quiescent
current overhead.
Automatic Level Control
6
VKNEE (V)
MAX98500
Boosted 2.2W Class D Amplifier
with Automatic Level Control
70
GAIN
AMPLIFIER GAIN (dB)
AGND
6
Unconnected
15.5
VBAT
20
_____________________________________________________________________________________
Boosted 2.2W Class D Amplifier
with Automatic Level Control
SDSPK
BOOST
STATUS
SPEAKER
STATUS
Low
Low
Off
Off
Low
High
Off
Off
High
Low
On
Off
High
High
On
On
SDBST
Shutdown
The MAX98500 features two active-low shutdown inputs
(SDSPK and SDBST). Table 2 shows the different shutdown configurations.
Click-and-Pop Suppression
threshold, the soft-start begins. When the input voltage
falls below the UVLO threshold, the boost converter and
speaker amplifier turn off.
Applications Information
Filterless Class D Operation
Traditional Class D amplifiers require an output filter to
recover the audio signal from the amplifier’s output. The
filter adds cost, increases the solution size of the amplifier, and can decrease efficiency and THD+N performance. The traditional PWM scheme uses large differential output swings (2 x supply voltage peak-to-peak) and
causes large ripple currents. Any parasitic resistance in
the filter components results in a loss of power and lowers the efficiency.
The MAX98500 speaker amplifier features Maxim’s comprehensive click-and-pop suppression. During startup,
the click-and-pop suppression circuitry reduces any
audible transient sources internal to the device. When
entering shutdown, the differential speaker outputs ramp
down to SPKPGND quickly and simultaneously.
The MAX98500 does not require an output filter. The
device relies on the inherent inductance of the speaker
coil and the natural filtering of both the speaker and
the human ear to recover the audio component of the
square-wave output. Eliminating the output filter results
in a smaller, less costly, and more efficient solution.
Current-Limit and Thermal Protection
Because the frequency of the MAX98500 output is well
beyond the bandwidth of most speakers, voice coil
movement due to the square-wave frequency is very
small. Although this movement is small, a speaker not
designed to handle the additional power can be damaged. For optimum results, use a speaker with a series
inductance > 10FH. Typical 8I speakers exhibit series
inductances in the 20FH to 100FH range.
The IC features overcurrent and thermal protection.
The IC shuts down when the VCCOUT output decreases
to about 80% of the expected output. The IC also
enters into shutdown when the die temperature exceeds
+165NC. The device remains in shutdown until power
is reset or SDBST is toggled low and back high after
the fault condition has been removed. The IC speaker
amplifier also features a 2A (typ) short-circuit protection
scheme.
Boost Converter
Soft-Start
The MAX98500 features a two-stage, soft-start, powerup sequence. When SDBST is taken high and VBAT is
above UVLO the soft-start first ramps VCCOUT quickly
to VBAT voltage with a battery current of 300mA (typ).
Once the VCCOUT reaches the VBAT voltage, the internal
switching turns on and ramps the VCCOUT to 5.5V in 5ms
(typ), see the Soft-Start graph in the Typical Operating
Characteristics. The maximum load current is available
after the soft-start is completed.
Undervoltage Lockout (UVLO)
The undervoltage lockout (UVLO) circuit compares the
voltage at VBAT with the UVLO threshold (2.2V typ) to
ensure that the input voltage is high enough for reliable
operation. Once the VBAT voltage exceeds the UVLO
RF Susceptibility
GSM radios transmit using time-division multiple access
(TDMA) with 217Hz intervals. The result is an RF signal
with strong amplitude modulation at 217Hz and its harmonics that is easily demodulated by audio amplifiers.
The MAX98500 is designed specifically to reject RF
signals; however, PCB layout has a large impact on the
susceptibility of the end product.
In RF applications, improvements to both layout and
component selection decrease the MAX98500’s susceptibility to RF noise and prevent RF signals from being
demodulated into audible noise. Trace lengths should be
kept below 1/4 of the wavelength of the RF frequency of
interest. Minimizing the trace lengths prevents them from
functioning as antennas and coupling RF signals into the
MAX98500. The wavelength (l) in meters is given by:
l = c/f where c = 3 x 108 m/s, and f = the RF frequency
of interest.
______________________________________________________________________________________ 11
MAX98500
Table 2. Shutdown Configurations
MAX98500
Boosted 2.2W Class D Amplifier
with Automatic Level Control
Route audio signals on the middle layers of the PCB to
allow the ground planes above and below to shield them
from RF interference. Ideally the top and bottom layers
of the PCB should primarily be ground planes to create
effective shielding.
Additional RF immunity can also be obtained from relying on the self-resonant frequency of capacitors as it
exhibits the frequency response similar to a notch filter.
Depending on the manufacturer, 10pF to 20pF capacitors
typically exhibit self resonance at RF frequencies. These
capacitors, when placed at the input pins, can effectively
shunt the RF noise at the inputs of the MAX98500. For
these capacitors to be effective, they must have a lowimpedance, low-inductance path to the ground plane.
Do not use microvias to connect to the ground plane as
these vias do not conduct well at RF frequencies.
Speaker Component Selection
Optional Ferrite Bead Filter
Additional EMI suppression can be achieved using a
filter constructed from a ferrite bead and a capacitor to
ground (Figure 3). Use a ferrite bead with low DC resistance, high-frequency (> 100MHz) impedance between
100I and 600I, and rated for at least 1A. The capacitor
value varies based on the ferrite bead chosen and the
actual speaker lead length. Select a capacitor less than
1nF based on EMI performance.
Input Capacitor (CIN)
An input capacitor, CIN, in conjunction with the input
impedance of the MAX98500 speaker inputs forms a
highpass filter that removes the DC bias from an incoming analog signal. The AC-coupling capacitor allows the
amplifier to automatically bias the signal to an optimum
DC level. Assuming zero-source impedance, the -3dB
point of the highpass filter is given by:
f-3dB =
1
2πRINCIN
Choose CIN such that f-3dB is well below the lowest frequency of interest. For best audio quality, use capacitors
whose dielectrics have low-voltage coefficients, such as
tantalum or aluminum electrolytic. Capacitors with highvoltage coefficients, such as ceramics, could result in
increased distortion at low frequencies.
Boost Converter Component Selection
Inductor Selection
In most step-up converter designs, a reasonable inductor value can be derived from the following equation.
This equation sets peak-to-peak inductor current at 1/2
the DC inductor current:
L = (2 x VBATT x D x (1-D))/(IOUT(MAX) x fSW)
where fSW is the switching frequency, and D is the duty
factor given by D = 1 - (VBAT/VOUT). Using L from the
equation above results in a peak-to-peak inductor current ripple of 0.5 x IOUT/(1 - D), and a peak inductor
current of 1.25 x IOUT/(1 - D). Ensure the peak (saturation) current rating of the inductor meets or exceeds this
requirement.
The recommended nominal inductance for the MAX98500
is 2.2FH. Nominal inductance decreases as the inductor
current increases. If the decrease from the nominal
inductance is severe, the boost converter may become
unstable or shut down at lower output power levels than
expected. Ensure the minimum inductance at the peak
inductor current is 1.0FH.
Output Capacitor (CVCCOUT)
An output capacitor, CVCCOUT, is required to keep the
output voltage ripple small and to ensure regulation loop
stability. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors
are highly recommended due to their small size and low
ESR. Ceramic capacitors with X5R or X7R temperature
characteristics generally perform well. The recommended nominal capacitance for the MAX98500 is 22FF (0805
case size or larger). Ensure the minimum capacitance at
5.5V is 6.8FF.
Input Capacitor (CVBAT)
An input capacitor, CVBAT, reduces the current peaks
drawn from the battery or input power source and reduces switching noise in the IC. The impedance of the input
capacitor at the switching frequency should be kept very
low. Ceramic capacitors are highly recommended due
to their small size and low ESR. Ceramic capacitors with
X5R or X7R temperature characteristics generally perform well. One 10FF ceramic capacitor is recommended
with a system bulk capacitance of 22FF or larger.
SPKP
MAX98500
SPKN
Figure 3. Optional Class D Ferrite Bead Filter
12 �������������������������������������������������������������������������������������
Boosted 2.2W Class D Amplifier
with Automatic Level Control
Bypass VBAT with a 10FF capacitor and a system
bulk capacitance of 22FF or larger. Bypass PVDD to
SPKPGND with a 0.1FF capacitor and with as minimal a
loop area as possible. Connect SPKP and SPKN to the
speaker using the shortest and widest traces possible.
Reducing trace length minimizes radiated EMI. Route
SPKP/SPKN as a differential pair on the PCB to minimize
loop area, thereby, the inductance of the circuit. If filter
components are used on the speaker outputs, be sure
to locate them as close as possible to the MAX98500 to
ensure maximum effectiveness. Minimize the trace length
from any ground-tied passive components to SPKPGND
to further minimize radiated EMI.
0.25mm
An evaluation kit (MAX98500 Evaluation Kit) is available
to provide an example layout for the MAX98500.
WLP Applications Information
For the latest application details on WLP construction,
dimensions, tape carrier information, PCB techniques,
bump-pad layout, and recommended reflow temperature profile, as well as the latest information on reliability
testing results, refer to the Application Note 1891: WaferLevel Packaging (WLP) and Its Applications on Maxim’s
website at www.maxim-ic.com/ucsp. See Figure 4 for the
recommended PCB footprint for the MAX98500.
0.22mm
Figure 4. Recommended PCB Footprint
Typical Application Circuit
2.2µH
20%
BATTERY
CVBAT
10µF
0805
10%
22µF*
LX
VBAT
B4
BOOST CONVERTER
SDBST D4
SDSPK C3
GAIN B2
A3
CONTROL
MAX98500
A2 VCCOUT
A1 PVDD
RKNEE B3
27.4kI
1%
CIN
1µF
INP D2
INN D3
CIN
1µF
CVCCOUT
22µF
0805
10%
0.1µF
10%
B1 SPKP
DIFFERENTIAL
INPUT
C4
AGND
GAIN
A4
BSTPGND
OUTPUT
STAGE
C1 SPKN
8I
D1, C2
SPKPGND
*SYSTEM LEVEL REQUIREMENT
______________________________________________________________________________________ 13
MAX98500
Supply Bypassing, Layout, and Grounding
Proper layout and grounding are essential for optimum
performance. Use a large continuous ground plane on
a dedicated layer of the PCB to minimize loop areas.
Connect AGND and BSTPGND/SPKPGND directly to the
ground plane using the shortest traces length possible.
Proper grounding improves audio performance, and
prevents any digital noise from coupling into the analog
audio signals.
MAX98500
Boosted 2.2W Class D Amplifier
with Automatic Level Control
Package 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 drawings may show a different suffix character, but the drawing pertains to the
package regardless of RoHS status.
PACKAGE TYPE
PACKAGE CODE
Document No.
16 WLP
W162B2+1
21-0200
14 �������������������������������������������������������������������������������������
Boosted 2.2W Class D Amplifier
with Automatic Level Control
REVISION
NUMBER
REVISION
DATE
0
5/10
DESCRIPTION
Initial release
PAGES
CHANGED
—
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
© 2010
Maxim Integrated Products 15
Maxim is a registered trademark of Maxim Integrated Products, Inc.
MAX98500
Revision History