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參數(shù)資料
| 型號(hào)： | LM4925 |
| 廠商： | National Semiconductor Corporation |
| 元件分類(lèi)： | 音頻放大器 |
| 英文描述： | Single Audio Amplifier |
| 中文描述： | 單音頻放大器 |
| 文件頁(yè)數(shù)： | 10/15頁(yè) |
| 文件大?。?/td> | 1046K |
| 代理商： | LM4925 |
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Application Information
BRIDGE (BTL) CONFIGURATION EXPLANATION
The LM4925 is a stereo audio power amplifier capable of
operating in bridged (BTL) mode. As shown in Figure 3, the
LM4925 has two internal operational amplifiers. The first
amplifier’s gain is externally configurable, while the second
amplifier should be externally fixed in a unity-gain, inverting
configuration. The closed-loop gain of the first amplifier is set
by selecting the ratio of Rf to Ri while the second amplifier’s
gain is fixed by the two external 20k
resistors. Figure 3
shows that the output of amplifier one serves as the input to
amplifier two which results in both amplifiers producing sig-
nals identical in magnitude, but out of phase by 180. Con-
sequently, the differential gain for the IC is
A
VD
= 2 * (R
f
/ R
i
)
By driving the load differentially through outputs VoA and
VoB, an amplifier configuration commonly referred to as
“bridged mode” is established. Bridged mode operation is
different from the classical single-ended amplifier configura-
tion where one side of the load is connected to ground. A
bridge amplifier design has a few distinct advantages over
the single-ended configuration, as it provides differential
drive to the load, thus doubling output swing for a specified
supply voltage. Four times the output power is possible as
compared to a single-ended amplifier under the same con-
ditions. This increase in attainable output power assumes
that the amplifier is not current limited or clipped. In order to
choose an amplifier’s closed-loop gain without causing ex-
cessive clipping, please refer to the Audio Power Amplifier
Design section.
A bridge configuration, such as the one used in LM4925,
also creates a second advantage over single-ended amplifi-
ers. Since the differential outputs, VoA and VoB, are biased
at half-supply, no net DC voltage exists across the load. This
eliminates the need for an output coupling capacitor which is
required in a single supply, single-ended amplifier configura-
tion.
MODE SELECT DETAIL
The LM4925 can be configured for either single ended (see
Figure 2 ) or BTL mode (see Figure 3). When the SE/BTL pin
has a logic high (V
DD
) applied to it, the LM4925 is in BTL
mode. If a logic low (GND) is applied to SE/BTL, the LM4925
operates in single-ended mode. The slew rate of V
DD
must
be greater than 2.5V/ms to ensure reliable Power on reset
(POR). The circuit shown in Figure 4 presents an applica-
tions solution to the problem of using different supply volt-
ages with different turn-on times in a system with the
LM4925. This circuit shows the LM4925 with a 25-50k
.
Pull-up resistor connected from the shutdown pin to V
.
The shutdown pin of the LM4925 is also being driven by an
open drain output of an external microcontroller on a sepa-
rate supply. This circuit ensures that shutdown is disabled
when powering up the LM4925 by either allowing shutdown
to be high before the LM4925 powers on (the microcontroller
powers up first) or allows shutdown to ramp up with V
(the
LM4925 powers up first). This will ensure the LM4925 pow-
ers up properly and enters the correct mode of operation
(BTL or SE). Please note that the SE/BTL pin should be tied
to GND for single-ended (SE) mode, and to Vdd for BTL
mode.
20121161
FIGURE 4. Recommended Circuit for Different Supply Turn-On Timing
L
www.national.com
10
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM49250 | 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:Enhanced Emissions Suppression Stereo Class D Audio Sub-System with Ground Referenced Headphone Amplifier and Mono Earpiece |
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| LM49250RL | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述: |
| LM49250RL/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(lèi)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 |
| LM49250RLEVAL | 功能描述:BOARD EVAL W/LM49250RL RoHS:否 類(lèi)別:編程器，開(kāi)發(fā)系統(tǒng) >> 評(píng)估板 - 音頻放大器 系列:Boomer®, PowerWise® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:- |
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