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參數(shù)資料
| 型號： | LM4804 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Low Voltage High Power Audio Power Amplifier |
| 中文描述： | 高功率低電壓音頻功率放大器 |
| 文件頁數(shù)： | 9/16頁 |
| 文件大?。?/td> | 820K |
| 代理商： | LM4804 |
Application Information
(Continued)
EXTERNAL COMPONENT SELECTION
Proper selection of external components in applications us-
ing integrated power amplifiers, and switching DC-DC con-
verters, is critical to optimize device and system perfor-
mance. Consideration to component values must be used to
maximize overall system quality.
The best capacitors for use with the switching converter
portion of the LM4804 are multi-layer ceramic capacitors.
They have the lowest ESR (equivalent series resistance)
and highest resonance frequency which makes them opti-
mum for use with high frequency switching converters.
When selecting a ceramic capacitor, only X5R and X7R
dielectric types should be used. Other types such as Z5U
and Y5F have such severe loss of capacitance due to effects
of temperature variation and applied voltage, they may pro-
vide as little as 20% of rated capacitance in many typical
applications. Always consult capacitor manufacturer’s data
curves before selecting a capacitor. High-quality ceramic
capacitors can be obtained from Taiyo-Yuden, AVX, and
Murata.
POWER SUPPLY BYPASSING
As with any amplifier, proper supply bypassing is critical for
low noise performance and high power supply rejection. The
capacitor location on both the bypass and power supply pins
should be as close to the device as possible.
SELECTING THE AUDIO AMPLIFIER’S INPUT
CAPACITOR
One of the major considerations is the closedloop bandwidth
of the amplifier. To a large extent, the bandwidth is dictated
by the choice of external components shown in Figure 1. The
input coupling capacitor, C
, forms a first order high pass filter
which limits low frequency response. This value should be
chosen based on needed frequency response for a few
distinct reasons.
Large input capacitors are both expensive and space hungry
for portable designs. Clearly, a certain sized capacitor is
needed to couple in low frequencies without severe attenu-
ation. But ceramic speakers used in portable systems,
whether internal or external, have little ability to reproduce
signals below 100Hz to 150Hz. Thus, using a large input
capacitor may not increase actual system performance.
In addition to system cost and size, click and pop perfor-
mance is effected by the size of the input coupling capacitor,
C
. A larger input coupling capacitor requires more charge to
reach its quiescent DC voltage (nominally 1/2 V
). This
charge comes from the output via the feedback and is apt to
create pops upon device enable. Thus, by minimizing the
capacitor size based on necessary low frequency response,
turn-on pops can be minimized.
SELECTING THE AUDIO AMPLIFIER’S BYPASS
CAPACITOR
Besides minimizing the input capacitor size, careful consid-
eration should be paid to the bypass capacitor value. Bypass
capacitor, C
B
, is the most critical component to minimize
turn-on pops since it determines how fast the amplifer turns
on. The slower the amplifier’s outputs ramp to their quies-
cent DC voltage (nominally 1/2 V
), the smaller the turn-on
pop. Choosing C
equal to 1.0μF along with a small value of
C
(in the range of 0.039μF to 0.39μF), should produce a
virtually clickless and popless shutdown function. While the
device will function properly, (no oscillations or motorboat-
ing), with C
equal to 0.1μF, the device will be much more
susceptible to turn-on clicks and pops. Thus, a value of C
B
equal to 1.0μF is recommended in all but the most cost
sensitive designs.
OPERATING PRINCIPLE
The LM4804 includes step-up DC-DC voltage regulation for
battery-powered and low-input voltage systems. It combines
a step-up switching regulator, N-channel power MOSFET,
built-in current limit, thermal limit, and voltage reference. The
switching DC-DC regulator boosts an input voltage between
.8V and 14V to a regulated output voltage between 1.24V
and 14V. The LM4804 starts from a low 1.1V input and
remains operational down to below .8V.
This device is optimized for use in cellular phones and other
applications requiring a small size, low profile, as well as low
quiescent current for maximum battery life during stand-by
and shutdown.
Additional features include a built-in peak switch current
limit, a high-efficiency gated-oscillator topology that offers an
output of up to 2A at low output voltages, and thermal
protection circuitry.
L
www.national.com
9
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|---|---|
| LM4804LQ | Low Voltage High Power Audio Power Amplifier |
| LM4817 | Circular Connector; MIL SPEC:MIL-C-5015; Body Material:Metal; Series:GT; No. of Contacts:85; Connector Shell Size:40; Connecting Termination:Crimp; Circular Shell Style:Wall Mount Receptacle; Body Style:Straight |
| LM4849 | Stereo 2W Audio Power Amplifiers with DC Volume Control and Input Mux |
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相關代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4804LQ | 功能描述:音頻放大器 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: 安裝風格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4804LQ/NOPB | 功能描述:音頻放大器 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: 安裝風格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4804LQX | 功能描述:音頻放大器 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: 安裝風格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4804LQX/NOPB | 功能描述:音頻放大器 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: 安裝風格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel |
| LM4805 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:3V, 1W Boosted Boomer |
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