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參數(shù)資料
| 型號(hào)： | LM4919 |
| 廠商： | National Semiconductor Corporation |
| 元件分類： | 音頻放大器 |
| 英文描述： | 1.5V, Mono 85mW BTL Output, 14mW Stereo Headphone Audio Amplifier |
| 中文描述： | 1.5V的，單聲道85mW BTL輸出，消耗14mW功率立體聲耳機(jī)音頻放大器 |
| 文件頁(yè)數(shù)： | 10/15頁(yè) |
| 文件大?。?/td> | 568K |
| 代理商： | LM4919 |
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Application Information
SINGLE ENDED (SE) CONFIGURATION EXPLANATION
As shown in Figure 2, the LM4919 has two operational
amplifiers internally, which have externally configurable gain.
The closed loop gain of the two configurable amplifiers is set
by selecting the ratio of Rf to Ri. Consequently, the gain for
each channel of the IC is
A
VD
= -(R
f
/ R
i
)
When the LM4919 operates in Single Ended mode, coupling
capacitors are used on each output (VoA and VoB) and the
SE/BTL pin (Pin 8) is connected to ground. These output
coupling capacitors blocks the half supply voltage to which
the output amplifiers are typically biased and couples the
audio signal to the headphones or other single-ended (SE)
loads. The signal return to circuit ground is through the
headphone jack’s sleeve.
BRIDGED (BTL) CONFIGURATION EXPLANATION
As shown in Figure 3, the LM4919 has two internal opera-
tional amplifiers. The first amplifier’s gain is externally con-
figurable, 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 R
to
R
while the second amplifier’s gain should be 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 signals identical in mag-
nitude, but out of phase by 180. Consequently, the differen-
tial gain for the IC is
A
VD
= 2 *(R
f
/ R
i
).
By driving the load differentially through outputs Vo1 and
Vo2, 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. It provides a differential drive
to the load, thus doubling output swing for a specified supply
voltage. Four times the output power is possible as com-
pared to a single-ended amplifier under the same conditions.
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 excessive
clipping, please refer to the Audio Power Amplifier Design
section.
A bridge configuration, such as the one used in LM4919,
also creates a second advantage over single-ended amplifi-
ers. Since the differential outputs, Vo1 and Vo2, 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 LM4919 can be configured in either Single Ended or
BTL mode (see Figure 2 and Figure 3). The default state of
the LM4919 at power up is single ended. During initial power
up or return from shutdown, the LM4919 must detect the
correct mode of operation by sensing the status of the
SE/BTL pin. When the bias voltage of the part ramps up to
60mV (as seen on the Bypass pin), an internal comparator
detects the status of SE/BTL; and at 10mV, latches that
value in place. Ramp up of the bias voltage will proceed at a
different rate from this point on depending upon operating
mode. BTL mode will ramp up about 11 times faster than
Single Ended mode. Shutdown is not a valid command
during this time period (T
) and should not enabled to
ensure a proper power on reset (POR) signal. In addition,
the slew rate of V
must be greater than 2.5V/ms to ensure
reliable POR. Recommended power up timing is shown in
Figure 5 along with proper usage of Shutdown and Mute.
The mode-select circuit is suspended during C
discharge
time. The circuit shown in Figure 4 presents an applications
solution to the problem of using different supply voltages
with different turn-on times in a system with the LM4919.
This circuit shows the LM4919 with a 25-50k
. Pull-up re-
sistor connected from the shutdown pin to V
DD
. The shut-
down pin of the LM4919 is also being driven by an open
drain output of an external microcontroller on a separate
supply. This circuit ensures that shutdown is disabled when
powering up the LM4919 by either allowing shutdown to be
high before the LM4919 powers on (the microcontroller pow-
ers up first) or allows shutdown to ramp up with V
(the
LM4919 powers up first). This will ensure the LM4919 pow-
ers up properly and enters the correct mode of operation.
Please note that the SE/BTL pin (Pin 8) should be tied to
GND for Single Ended mode, and to V
DD
for BTL mode.
L
www.national.com
10
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM4919MM | 1.5V, Mono 85mW BTL Output, 14mW Stereo Headphone Audio Amplifier |
| LM4921 | Low Voltage I2S 16-Bit Stereo DAC with Stereo Headphone Power Amplifiers and Volume Control |
| LM4923 | 1.1 Watt Fully Differential Audio Power Amplifier With Shutdown Select |
| LM4923LQ | 1.1 Watt Fully Differential Audio Power Amplifier With Shutdown Select |
| LM4925 | Single Audio Amplifier |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM4919A WAF | 制造商:Texas Instruments 功能描述: |
| LM4919MM | 制造商:Texas Instruments 功能描述:AMP STEREO H/P 1.5V 14MW SMD 4919 |
| LM4919MM/NOPB | 功能描述:IC AMP AUDIO MONO/STER AB 10MSOP RoHS:是 類別:集成電路 (IC) >> 線性 - 音頻放大器 系列:Boomer® 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® 類型:H 類 輸出類型:耳機(jī)，2-通道（立體聲） 在某負(fù)載時(shí)最大輸出功率 x 通道數(shù)量:35mW x 2 @ 16 歐姆 電源電壓:1.62 V ~ 1.98 V 特點(diǎn):I²C，麥克風(fēng)，靜音，短路保護(hù)，音量控制 安裝類型:表面貼裝 供應(yīng)商設(shè)備封裝:25-WLP（2.09x2.09） 封裝/外殼:25-WFBGA，WLCSP 包裝:帶卷 (TR) |
| LM4919MMBD | 功能描述:BOARDS EVALUATION LM4919MM RoHS:否 類別:編程器，開發(fā)系統(tǒng) >> 評(píng)估板 - 音頻放大器 系列:Boomer® 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:- |
| LM491-S | 功能描述:基本/快動(dòng)開關(guān) Foot Switch RoHS:否 制造商:Omron Electronics 觸點(diǎn)形式:SPDT 執(zhí)行器:Lever 電流額定值:5 A 電壓額定值 AC:250 V 電壓額定值 DC:30 V 功率額定值: 工作力:120 g IP 等級(jí):IP 67 NEMA 額定值: 端接類型:Wire 安裝:Panel |
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