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參數(shù)資料
| 型號(hào)： | LM4892M/NOPB |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | 1 W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8 |
| 封裝： | SOIC-8 |
| 文件頁數(shù)： | 2/22頁 |
| 文件大?。?/td> | 1037K |
| 代理商： | LM4892M/NOPB |
Typical Performance Characteristics (Continued)
Output Power vs Supply Voltage
R
L =32
Output Power vs Supply Voltage
Headphone Output, R
L =32
20012780
20012781
Application Information
BRIDGE CONFIGURATION EXPLANATION
As shown in Figure 1, the LM4892 has two operational
amplifiers internally, allowing for a few different amplifier
configurations. The first amplifier’s gain is externally config-
urable, while the second amplifier is internally fixed in a
unity-gain, inverting configuration. The closed-loop gain of
the first amplifier is set by selecting the ratio of R
f to Ri while
the second amplifier’s gain is fixed by the two internal 20k
resistors. Figure 1 shows that the output of amplifier one
serves as the input to amplifier two which results in both
amplifiers producing signals identical in magnitude, but out
of phase by 180. Consequently, the differential gain for the
IC is
A
VD= 2 *(Rf/Ri)
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, 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 LM4892,
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. Without an output coupling capacitor, the half-supply
bias across the load would result in both increased internal
IC power dissipation and also possible loudspeaker damage.
POWER DISSIPATION
Power dissipation is a major concern when designing a
successful amplifier, whether the amplifier is bridged or
single-ended. A direct consequence of the increased power
delivered to the load by a bridge amplifier is an increase in
internal power dissipation. Since the LM4892 has two opera-
tional amplifiers in one package, the maximum internal
power dissipation is 4 times that of a single-ended amplifier.
The maximum power dissipation for a given application can
be derived from the power dissipation graphs or from Equa-
tion 1.
P
DMAX = 4*(VDD)
2/(2
π2R
L)
(1)
It is critical that the maximum junction temperature T
JMAX of
150C is not exceeded. T
JMAX can be determined from the
power derating curves by using P
DMAX and the PC board foil
area. By adding additional copper foil, the thermal resistance
of the application can be reduced from a free air value of
150C/W, resulting in higher P
DMAX. Additional copper foil
can be added to any of the leads connected to the LM4892.
It is especially effective when connected to V
DD, GND, and
the output pins. Refer to the application information on the
LM4892 reference design board for an example of good heat
sinking. If T
JMAX
still exceeds 150C, then additional
changes must be made. These changes can include re-
duced supply voltage, higher load impedance, or reduced
ambient temperature. Internal power dissipation is a function
of output power. Refer to the Typical Performance Charac-
teristics curves for power dissipation information for differ-
ent output powers and output loading.
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. Typical appli-
cations employ a 5V regulator with 10F tantalum or elec-
trolytic capacitor and a ceramic bypass capacitor which aid
in supply stability. This does not eliminate the need for
bypassing the supply nodes of the LM4892. The selection of
a bypass capacitor, especially C
B, is dependent upon PSRR
LM4892
www.national.com
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| LM4892MX/NOPB | 功能描述:IC AMP AUDIO PWR 1W MONO 8SOIC 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) |
| LM4893 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:1.1 Watt Audio Power Amplifier |
| LM4893ITL | 制造商:Texas Instruments 功能描述:AMP POWER AUDIO 1.1W SMD BUMP-9 |
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| LM4893ITLBD | 功能描述:BOARD EVALUATION LM4893ITL 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:- |
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