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參數資料
| 型號： | LM4819MBD |
| 廠商： | National Semiconductor |
| 文件頁數： | 2/27頁 |
| 文件大?。?/td> | 0K |
| 描述： | BOARD EVALUATION LM4819M |
| 標準包裝： | 1 |
| 系列： | Boomer® |
| 放大器類型： | AB 類 |
| 輸出類型： | 1-通道（單聲道） |
| 在某負載時最大輸出功率 x 通道數量： | 350mW x 1 @ 16 歐姆 |
| 電源電壓： | 2 V ~ 5.5 V |
| 工作溫度： | -40°C ~ 85°C |
| 板類型： | 完全填充 |
| 已用 IC / 零件： | LM4819 |
| 已供物品： | 板 |
| 相關產品： | LM4819M/NOPB-ND - IC AMP AUDIO PWR .35W MONO 8SOIC LM4819MX/NOPBTR-ND - IC AMP AUDIO PWR .35W MONO 8SOIC LM4819MM-ND - IC AMP AUDIO PWR .35W MONO 8MSOP LM4819MMX-ND - IC AMP AUDIO PWR .35W MONO 8MSOP |
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SNAS133D – FEBRUARY 2001 – REVISED MARCH 2013
APPLICATION INFORMATION
BRIDGE CONFIGURATION EXPLANATION
As shown in Figure 1, the LM4819 consists of two operational amplifiers. External resistors, Ri and RF set the
closed-loop gain of the first amplifier (and the amplifier overall), whereas two internal 20k
resistors set the
second amplifier's gain at -1. The LM4819 is typically used to drive a speaker connected between the two
amplifier outputs.
Figure 1 shows that the output of Amp1 servers as the input to Amp2, which results in both amplifiers producing
signals identical in magnitude but 180° out of phase. Taking advantage of this phase difference, a load is placed
between V01 and V02 and driven differentially (commonly referred to as "bridge mode"). This results in a
differential gain of
AVD= 2 *(Rf/Ri)
(1)
Bridge mode is different from single-ended amplifiers that drive loads connected between a single amplifier's
output and ground. For a given supply voltage, bridge mode has a distinct advantage over the single-ended
configuration: its differential output doubles the voltage swing across the load. This results in four times the
output power when compared to a single-ended amplifier under the same conditions. This increase in attainable
output assumes that the amplifier is not current limited or the output signal is not clipped. To ensure minimum
output signal clipping when choosing an amplifier's closed-loop gain, refer to the Audio Power Amplifier Design
Example section.
Another advantage of the differential bridge output is no net DC voltage across the load. This results from biasing
V01 and V02 at half-supply. This eliminates the coupling capacitor that single supply, single-ended amplifiers
require. Eliminating an output coupling capacitor in a single-ended configuration forces a single supply amplifier's
half-supply bias voltage across the load. The current flow created by the half-supply bias voltage increases
internal IC power dissipation and may permanently damage loads such as speakers.
POWER DISSIPATION
Power dissipation is a major concern when designing a successful bridged or single-ended amplifier. Equation 2
states the maximum power dissipation point for a single-ended amplifier operating at a given supply voltage and
driving a specified load.
PDMAX = (VDD)
2 /(2π2R
L ) (W) Single-ended
(2)
However, a direct consequence of the increased power delivered to the load by a bridged amplifier is an increase
in the internal power dissipation point for a bridge amplifier operating at the same given conditions. Equation 3
states the maximum power dissipation point for a bridged amplifier operating at a given supply voltage and
driving a specified load.
PDMAX = 4(VDD)
2/(2π2 R
L ) (W) Bridge Mode
(3)
The LM4819 has two operational amplifiers in one package and the maximum internal power dissipation is four
times that of a single-ended amplifier. However, even with this substantial increase in power dissipation, the
Lm4819 does not require heatsinking. From Equation 3, assuming a 5V power supply and an 8
load, the
maximum power dissipation point is 633mW. The maximum power dissipation point obtained from Equation 3
must not exceed the power dissipation predicted by Equation 4:
PDMAX = (TJMAX - TA)/θJA (W)
(4)
For the micro DGK0008A package,
θJA = 210°C/W, for the D0008A package, θJA = 170°C/W , and TJMAX = 150°C
for the LM4819. For a given ambient temperature, TA, Equation 4 can be used to find the maximum internal
power dissipation supported by the IC packaging. If the result of Equation 3 is greater than the result of
Equation 4, then decrease the supply voltage, increase the load impedance, or reduce the ambient temperature.
For a typical application using the D0008A packaged LM4819 with a 5V power supply and an 8
load, the
maximum ambient temperature that does not violate the maximum junction temperature is approximately 42°C. If
a DGK0008A packaged part is used instead with the same supply voltage and load, the maximum ambient
temperature is 17°C. In both cases, it is assumed that a device is a surface mount part operating around the
maximum power dissipation point. The assumption that the device is operating around the maximum power
dissipation point is incorrect for an 8
load. The maximum power dissipation point occurs when the output power
is equal to the maximum power dissipation or 50% efficiency. The LM4819 is not capable of the output power
level (633mW) required to operate at the maximum power dissipation point for an 8
load. To find the maximum
power dissipation, the graph Figure 22 must be used. From the graph, the maximum power dissipation for an 8
10
Copyright 2001–2013, Texas Instruments Incorporated
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相關代理商/技術參數 |
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|---|---|
| LM4819MBD/NOPB | 功能描述:音頻 IC 開發(fā)工具 LM4819MBD EVAL MOD RoHS:否 制造商:Texas Instruments 產品:Evaluation Kits 類型:Audio Amplifiers 工具用于評估:TAS5614L 工作電源電壓:12 V to 38 V |
| LM4819MM | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產品: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 |
| LM4819MM/NOPB | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產品: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 |
| LM4819MMX | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產品: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 |
| LM4819MMX/NOPB | 功能描述:音頻放大器 RoHS:否 制造商:STMicroelectronics 產品: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 |
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