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參數(shù)資料
| 型號： | LM4755TSX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | LM4755 Stereo 11W Audio Power Amplifier with Mute; Package: TO-263; No of Pins: 9 |
| 中文描述： | 11 W, 2 CHANNEL, AUDIO AMPLIFIER, PSSO9 |
| 封裝： | TO-263, 9 PIN |
| 文件頁數(shù)： | 9/24頁 |
| 文件大小： | 530K |
| 代理商： | LM4755TSX |
The above values for
θ
SA vary widely due to dimensional pro-
portions (i.e. variations in width and length will vary
θ
SA).
For audio applications, where peak power levels are short in
duration, this part will perform satisfactory with less heatsink-
ing/copper clad area. As with any high power design proper
bench testing should be undertaken to assure the design can
dissipate the required power. Proper bench testing requires
attention to worst case ambient temperature and air flow. At
high power dissipation levels the part will show a tendency to
increase saturation voltages, thus limiting the undistorted
power levels.
DETERMINING MAXIMUM POWER DISSIPATION
For a single-ended class AB power amplifier, the theoretical
maximum power dissipation point is a function of the supply
voltage, V
S, and the load resistance, RL and is given by the
following equation:
(single channel)
P
DMAX (W) = [VS
2
/ (2
π2 R
L)]
The above equation is for a single channel class-AB power
amplifier. For dual amplifiers such as the LM4755, the equa-
tion for calculating the total maximum power dissipated is:
(dual channel)
P
DMAX (W) = 2 [VS
2
/ (2
π2 R
L)]
or
V
S
2
/ (
π2 R
L)
(Bridged Outputs)
P
DMAX (W) = 4[VS
2
/ (2
π2 R
L)]
HEATSINK DESIGN EXAMPLE
Determine the system parameters:
V
S = 24V
Operating Supply Voltage
R
L = 4
Minimum Load Impedance
T
A = 55°C
Worst Case Ambient Temperature
Device parameters from the datasheet:
T
J = 150°C
Maximum Junction Temperature
θ
JC = 2°C/W
Junction-to-Case Thermal Resistance
Calculations:
2 P
DMAX = 2 [VS
2
/ 2
π2 R
L)] = (24V)
2
/ (2
π2 4) =
14.6W
θ
SA ≤ [(TJ-TA) / PDMAX] - θJC–θCS = [ (150°C - 55°C) / 14.6W]
- 2°C/W–0.2°C/W = 4.3°C/W
Conclusion: Choose a heatsink with
θ
SA ≤ 4.3°C/W.
TO-263 HEATSINK DESIGN EXAMPLES
Example 1:
(Stereo Single-Ended Output)
Given:
T
A=30°C
T
J=150°C
R
L=4
V
S=12V
θ
JC=2°C/W
P
DMAX from PD vs PO Graph:
P
DMAX ≈ 3.7W
Calculating P
DMAX:
P
DMAX = VCC
2
/(
π2R
L) = (12V)
2
/
π2(4)) = 3.65W
Calculating Heatsink Thermal Resistance:
θ
SA < TJ TA / PDMAX θJC θCS
θ
SA < 120°C/3.7W 2.0°C/W 0.2°C/W = 30.2°C/W
Therefore the recommendation is to use 1.5 × 1.5 square inch
of single-sided copper clad.
Example 2:
(Stereo Single-Ended Output)
Given:
T
A=50°C
T
J=150°C
R
L=4
V
S=12V
θ
JC=2°C/W
P
DMAX from PD vs PO Graph:
P
DMAX ≈ 3.7W
Calculating P
DMAX:
P
DMAX = VCC
2
/(
π2R
L)= (12V)
2
/(
π2(4)) = 3.65W
Calculating Heatsink Thermal Resistance:
θ
SA < [(TJ TA) / PDMAX] θJC θCS
θ
SA < 100°C/3.7W 2.0°C/W 0.2°C/W = 24.8°C/W
Therefore the recommendation is to use 2.0 × 2.0 square inch
of single-sided copper clad.
Example 3:
(Bridged Output)
Given:
T
A=50°C
T
J=150°C
R
L=8
V
S=12V
θ
JC=2°C/W
Calculating P
DMAX:
P
DMAX = 4[VCC
2
/(2
π2R
L)] = 4(12V)
2
/(2
π2(8)) = 3.65W
Calculating Heatsink Thermal Resistance:
θ
SA < [(TJ TA) / PDMAX] θJC θCS
θ
SA < 100°C / 3.7W 2.0°C/W 0.2°C/W = 24.8°C/W
Therefore the recommendation is to use 2.0 × 2.0 square inch
of single-sided copper clad.
LAYOUT AND GROUND RETURNS
Proper PC board layout is essential for good circuit perfor-
mance. When laying out a PC board for an audio power
amplifier, particular attention must be paid to the routing of the
output signal ground returns relative to the input signal and
bias capacitor grounds. To prevent any ground loops, the
ground returns for the output signals should be routed sepa-
rately and brought together at the supply ground. The input
signal grounds and the bias capacitor ground line should also
be routed separately. The 0.1 F high frequency supply by-
pass capacitor should be placed as close as possible to the
IC.
17
www.national.com
LM4755
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM4755TSX/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 |
| LM4756 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dual 7W Audio Power Amplifier w/Mute, Standby and Volume Control |
| LM4765 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Audio Power Amplifier Series Dual 30W Audio Power Amplifier with Mute and Standby Modes |
| LM4765T | 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 |
| LM4765T/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 |
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