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| 型号： | MAX9702ETI+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 11/31页 |
| 文件大小： | 0K |
| 描述： | IC AMP AUDIO PWR 1.8W D 28TQFN |
| 标准包装： | 2,500 |
| 系列： | DirectDrive® |
| 类型： | D 类 |
| 输出类型： | 2-通道（立体声）带立体声耳机 |
| 在某负载时最大输出功率 x 通道数量： | 1.8W x 2 @ 4 欧姆; 45mW x 2 @ 32 欧姆 |
| 电源电压： | 2.5 V ~ 5.5 V |
| 特点： | 消除爆音，差分输入，I²C，静音，短路和热保护，关机 |
| 安装类型： | 表面贴装 |
| 供应商设备封装： | 28-TQFN-EP（5x5） |
| 封装/外壳： | 28-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
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Headphone Amplifier
In conventional single-supply headphone amplifiers,
the output-coupling capacitor is a major contributor of
audible clicks and pops. Upon startup, the amplifier
charges the coupling capacitor to its bias voltage, typi-
cally half the supply. Likewise, during shutdown the
capacitor is discharged to GND. This results in DC shift
across the capacitor, which in turn, appears as an
audible transient at the speaker. Since the MAX9702
headphone amplifier does not require output-coupling
capacitors, this does not arise.
The MAX9702 offers four headphone amplifier gain set-
tings controlled through the I2C interface. Headphone
amplifier gains of -2dB, +1dB, +4dB, and +7dB are set
by command register bits 3 and 4 (Table 5).
Additionally, the MAX9702 features extensive click-and-
pop suppression that eliminates any audible transient
sources internal to the device.
In most applications, the output of the preamplifier dri-
ving the MAX9702 has a DC bias of typically half the
supply. During startup, the input-coupling capacitor is
charged to the preamplifier’s DC bias voltage through
the RF of the MAX9702, resulting in a DC shift across
the capacitor and an audible click-and-pop. An internal
delay of 40ms eliminates the clicks-and-pops caused
by the input filter.
DirectDrive
Traditional single-supply headphone amplifiers have
outputs biased at a nominal DC voltage (typically half
the supply) for maximum dynamic range. Large-cou-
pling capacitors are needed to block this DC bias from
the headphone. Without these capacitors, a significant
amount of DC current flows to the headphone, resulting
in unnecessary power dissipation and possible dam-
age to both headphone and headphone amplifier.
Maxim’s DirectDrive architecture uses a charge pump
to create an internal negative supply voltage. This
allows the headphone outputs of the MAX9702 to be
biased at GND, almost doubling dynamic range while
operating from a single supply. With no DC component,
there is no need for the large DC-blocking capacitors.
Instead of two large (220F, typ) tantalum capacitors,
the MAX9702 charge pump requires two small ceramic
capacitors, conserving board space, reducing cost,
and improving the frequency response of the head-
phone amplifier. See the Output Power vs. Charge-
Pump Capacitance and Load Resistance graph in the
Typical Operating Characteristics for details of the pos-
sible capacitor sizes. There is a low DC voltage on the
driver outputs due to amplifier offset. However, the off-
set of the MAX9702 is typically 1.1mV, which, when
combined with a 32Ω load, results in less than 56A of
DC current flow to the headphones.
In addition to the cost and size disadvantages of the
DC-blocking capacitors required by conventional head-
phone amplifiers, these capacitors limit the amplifier’s
low-frequency response and can distort the audio sig-
nal. Previous attempts at eliminating the output-cou-
pling capacitors involved biasing the headphone return
(sleeve) to the DC bias voltage of the headphone
amplifiers. This method raises some issues:
1) The sleeve is typically grounded to the chassis.
Using the midrail biasing approach, the sleeve must
be isolated from system ground, complicating prod-
uct design.
2) During an ESD strike, the driver’s ESD structures
are the only path to system ground. Thus, the driver
must be able to withstand the full ESD strike.
3) 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.
MAX9702
1.8W, Filterless, Stereo, Class D Audio Power
Amplifier and DirectDrive Stereo Headphone Amplifier
______________________________________________________________________________________
19
VDD
+VDD
-VDD
VDD/2
GND
CONVENTIONAL AMPLIFIER BIASING SCHEME
DirectDrive BIASING SCHEME
Figure 7. Traditional Amplifier Output vs. MAX9702 DirectDrive
Output
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX9702EUI+ | 制造商:Maxim Integrated Products 功能描述:AUD AMP HDPH/SPKR 2CH STEREO 1.8W/0.045W CLS-AB/CLS-D 28TSSO - Rail/Tube |
| MAX9702EUI+T | 制造商:Maxim Integrated Products 功能描述:AUD AMP HDPH/SPKR 2CH STEREO 1.8W/0.045W CLS-AB/CLS-D 28TSSO - Tape and Reel |
| MAX9702EVCMODU | 功能描述:放大器 IC 开发工具 MAX9702/2B Eval Kit RoHS:否 制造商:International Rectifier 产品:Demonstration Boards 类型:Power Amplifiers 工具用于评估:IR4302 工作电源电压:13 V to 23 V |
| MAX9702EVKIT | 功能描述:放大器 IC 开发工具 MAX9702/2B Eval Kit RoHS:否 制造商:International Rectifier 产品:Demonstration Boards 类型:Power Amplifiers 工具用于评估:IR4302 工作电源电压:13 V to 23 V |
| MAX9703DEVBRD | 功能描述:放大器 IC 开发工具 MAX9703 Eval Kit RoHS:否 制造商:International Rectifier 产品:Demonstration Boards 类型:Power Amplifiers 工具用于评估:IR4302 工作电源电压:13 V to 23 V |
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