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參數(shù)資料
| 型號(hào)： | LM3570SDX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 顯示驅(qū)動(dòng)器 |
| 英文描述： | Low Noise White LED Driver System |
| 中文描述： | LED DISPLAY DRIVER, DSO14 |
| 封裝： | 4 X 3 MM, 0.80 MM HEIGHT, LLP-14 |
| 文件頁數(shù)： | 12/13頁 |
| 文件大?。?/td> | 352K |
| 代理商： | LM3570SDX |
Application Information
(Continued)
their high ESR, as compared to ceramic capacitors. For
most applications, ceramic capacitors with X7R or X5R tem-
perature characteristic are preferred for use with the
LM3570. These capacitors have tight capacitance tolerance
(as good as
±
10%), and hold their value over temperature
(X7R:
±
15% over -55C to 125C; X5R:
±
15% over -55C to
85C). Capacitors with Y5V and/or Z5U temperature charac-
teristic are generally not recommended. These types of ca-
pacitors typically have wide capacitance tolerance (+80%,
-20%), vary significantly over temperature (Y5V: +22%,
-82% over -30C to +85C range; Z5U: +22%, -56% over
+10C to +85C range), and have poor voltage coefficients.
Under some conditions, a nominal 1μF Y5V or Z5U capacitor
could have a capacitance of only 0.1μF. Such detrimental
deviation is likely to cause these Y5V and Z5U of capacitors
to fail to meet the minimum capacitance requirements of the
LM3570.
POWER DISSIPATION
The maximum allowable power dissipation that this package
is capable of handling can be determined as follows:
P
DMax
= (T
JMax
- T
A
) /
θ
JA
Where T
is the maximum junction temperature, T
is the
ambient temperature, and
θ
JA
is the junction-to-ambient
thermal resistance of the specified package. The LM3570
comes in the LLP-14 package that has a junction-to-ambient
thermal resistance (
θ
JA
) equal to 45C/W. This value of
θ
JA
is
highly dependant upon the layout of the PC board (See the
PCB Layout Considerations section of this datasheet for
more information). The actual power dissipated by the
LM3570 follows the equation:
P
DISS
=(V
IN
x I
IN
) - (N(V
DX
x I
DX
) - (V
OUT
xI
OUT
))
Where N equals the number of active outputs, V
is the
LED forward voltage, I
DX
is the current supplied to the diode
by the Dx outputs, V
is the LM3570 output voltage (typ. =
4.35V), and I
is the current draw directly from the LM370
charge pump. Power dissipation must be less than that
allowed by the package. Please refer to the Absolute Maxi-
mum Rating of the LM3570.
THERMAL PROTECTION
The LM3570 has internal thermal protection circuitry to dis-
able the part if the junction temperature exceeds 150C. This
feature will protect the device from damage due to excessive
power dissipation. The device will recover and operate nor-
mally when the junction temperature falls below 140C. It is
important to have good thermal conduction with a proper
layout to reduce thermal resistance.
PCB LAYOUT CONSIDERATIONS
The LLP is a leadframe based Chip Scale Package (CSP)
with very good thermal properties. This package has an
exposed DAP (die attach pad) at the center of the package
measuring 3.0mm x 1.6mm. The main advantage of this
exposed DAP is to offer lower thermal resistance when it is
soldered to the thermal land on the PCB. For PCB layout,
National highly recommends a 1:1 ratio between the pack-
age and the PCB thermal land. To further enhance thermal
conductivity, the PCB thermal land may include vias to a
ground plane. For more detailed instructions on mounting
LLP packages, please refer to National Semiconductor Ap-
plication Note AN-1187.
L
www.national.com
12
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3578 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Switching Regulator |
| LM3578A | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Switching Regulator |
| LM3578AM | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| LM3578AM | 制造商:Texas Instruments 功能描述:SWITCHED MODE REG SMD 3578 SOIC8 |
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