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參數(shù)資料
| 型號： | MAX9720AEBE+T |
| 廠商： | Maxim Integrated Products |
| 文件頁數(shù)： | 3/21頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC AMP AUDIO .05W STER AB 16UCSP |
| 產(chǎn)品培訓(xùn)模塊： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 標(biāo)準(zhǔn)包裝： | 2,500 |
| 系列： | DirectDrive®, SmartSense™ |
| 類型： | AB 類 |
| 輸出類型： | 耳機，2-通道（立體聲） |
| 在某負(fù)載時最大輸出功率 x 通道數(shù)量： | 50mW x 2 @ 32 歐姆 |
| 電源電壓： | 1.8 V ~ 3.6 V |
| 特點： | 消除爆音，短路保護(hù)和熱保護(hù)，關(guān)閉 |
| 安裝類型： | 表面貼裝 |
| 供應(yīng)商設(shè)備封裝： | 16-UCSP（2x2） |
| 封裝/外殼： | 16-WFBGA，CSPBGA |
| 包裝： | 帶卷 (TR) |
DirectDrive
Conventional single-supply headphone amplifiers have
their outputs biased about a nominal DC voltage (typical-
ly half the supply) for maximum dynamic range. Large
coupling capacitors are needed to block this DC bias
from the headphone. Without these capacitors, a signifi-
cant amount of DC current flows to the headphone,
resulting in unnecessary power dissipation and possible
damage to both headphone and headphone amplifier.
Maxim’s DirectDrive architecture uses a charge pump
to create an internal negative supply voltage. This
allows the MAX9720 output to be biased about 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 capacitors (220F typ), the MAX9720 charge
pump requires only two, small ceramic capacitors (1F
typ), conserving board space, reducing cost, and
improving the frequency response of the headphone
amplifier. See the Output Power vs. Charge-Pump
Capacitance and Load Resistance graph in the Typical
Operating Characteristics for details of the possible
capacitor sizes.
Previous attempts to eliminate the output-coupling
capacitors involved biasing the headphone return
(sleeve) to the DC bias voltage of the headphone
amplifiers. This method raised some issues:
The sleeve is typically grounded to the chassis.
Using this biasing approach, the sleeve must be
isolated from system ground, complicating product
design.
During an ESD strike, the amplifier’s ESD structures
are the only path to system ground. The amplifier
must be able to withstand the full ESD strike.
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
equipment, resulting in large ground-loop current
and possible damage to the amplifiers.
When using a combination microphone and speak-
er headset (in a cell phone or PDA application), the
microphone typically requires a GND return. Any
DC bias on the sleeve conflicts with the microphone
requirements (Figure 2).
Low-Frequency Response
In addition to the cost and size disadvantages, the DC-
blocking capacitors limit the low-frequency response of
the amplifier and distort the audio signal:
The impedance of the headphone load and the DC-
blocking capacitor form a highpass filter with the
-3dB point determined by:
where RL is the impedance of the headphone and
COUT is the value of the DC-blocking capacitor.
The highpass filter is required by conventional single-
ended, single-supply headphone amplifiers to block
the midrail DC component of the audio signal from the
headphones. Depending on the -3dB point, the filter
can attenuate low-frequency signals within the audio
band. Larger values of COUT reduce the attenuation,
but are physically larger, more expensive capacitors.
Figure 3 shows the relationship between the size of
COUT and the resulting low-frequency attenuation. Note
that the -3dB point for a 16
Ω headphone with a 100F
blocking capacitor is 100Hz, well within the audio
band.
f
RC
dB
L OUT
=
3
1
2
π
MAX9720
50mW, DirectDrive, Stereo Headphone
Amplifier with SmartSense and Shutdown
______________________________________________________________________________________
11
+VDD
-VDD
GND
VOUT
CONVENTIONAL DRIVER-BIASING SCHEME
DirectDrive BIASING SCHEME
VDD/2
VDD
GND
VOUT
Figure 1. Conventional Amplifier Output Waveform vs.
MAX9720 Output Waveform
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX9720AEUE | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX9720AEUE+ | 功能描述:音頻放大器 50mW DirectDrive Headphone Amplifier RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| MAX9720AEUE+T | 功能描述:音頻放大器 50mW DirectDrive Headphone Amplifier RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| MAX9720BEBE | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX9720BEBE+ | 制造商:Maxim Integrated Products 功能描述:AUD AMP HDPH 2CH STEREO 0.05W CLS-AB 16UCSP - Rail/Tube |
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