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參數(shù)資料
| 型號： | LM5008SD |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | High Voltage (100V) Step Down Switching Regulator |
| 中文描述： | 0.61 A SWITCHING REGULATOR, DSO8 |
| 封裝： | 4 X 4 MM, LLP-8 |
| 文件頁數(shù)： | 9/15頁 |
| 文件大?。?/td> | 278K |
| 代理商： | LM5008SD |
High Voltage Start-up Regulator
(Continued)
Regulation Comparator
The feedback voltage at FB is compared to an internal 2.5V
reference. In normal operation (the output voltage is regu-
lated), an on-time period is initiated when the voltage at FB
falls below 2.5V. The buck switch will stay on for the on-time,
causing the FB voltage to rise above 2.5V. After the on-time
period, the buck switch will stay off until the FB voltage again
falls below 2.5V. During start-up, the FB voltage will be below
2.5V at the end of each on-time, resulting in the minimum
off-time of 300 ns. Bias current at the FB pin is nominally 100
nA.
Over-Voltage Comparator
The feedback voltage at FB is compared to an internal
2.875V reference. If the voltage at FB rises above 2.875V
the on-time pulse is immediately terminated. This condition
can occur if the input voltage, or the output load, change
suddenly. The buck switch will not turn on again until the
voltage at FB falls below 2.5V.
ON-Time Generator and Shutdown
The on-time for the LM5008 is determined by the R
resis-
tor, and is inversely proportional to the input voltage (Vin),
resulting in a nearly constant frequency as Vin is varied over
its range. The on-time equation for the LM5008 is:
T
ON
= 1.25 x 10
-10
x R
ON
/ V
IN
See
Figure 3
. R
ON
should be selected for a minimum on-time
(at maximum V
) greater than 400 ns, for proper current
limit operation. This requirement limits the maximum fre-
quency for each application, depending on V
IN
and V
OUT
.
See
Figure 4
.
The LM5008 can be remotely disabled by taking the R
/SD
pin to ground. See
Figure 11
. The voltage at the R
/SD pin
is between 1.5 and 3.0 volts, depending on Vin and the value
of the R
ON
resistor.
(2)
20097906
FIGURE 10. Self Biased Configuration
20097907
FIGURE 11. Shutdown Implementation
L
www.national.com
9
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM5008SD/NOPB | 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 安裝風格:SMD/SMT |
| LM5008SDC | 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 安裝風格:SMD/SMT |
| LM5008SDC/NOPB | 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 安裝風格:SMD/SMT |
| LM5008SDCX | 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 安裝風格:SMD/SMT |
| LM5008SDCX/NOPB | 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 安裝風格:SMD/SMT |
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