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參數(shù)資料
| 型號： | LM3485 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Hysteretic PFET Buck Controller |
| 中文描述： | 遲滯PFET的降壓控制器 |
| 文件頁數(shù)： | 11/15頁 |
| 文件大小： | 369K |
| 代理商： | LM3485 |
Functional Description
(Continued)
Start Up
The current limit circuit is active during start-up. During
start-up the PFET will stay on until either the current limit or
the feedback comparator is tripped
If the current limit comparator is tripped first then the fold
back characteristic should be taken into account. Start-up
into full load may require a higher current limit set point or the
load must be applied after start-up.
One problem with selecting a higher current limit is inrush
current during start-up. Adding a capacitance (C
ADJ
) in par-
allel with R
results in soft-start. C
and R
create an
RC time constant forcing current limit to activate at a lower
current. The output voltage will ramp more slowly when
using the soft-start functionality.
The C
also filters unwanted noise so that the ISENSE
comparator will not be accidentally triggered. A value of
100pF to 1nF is recommended in most applications. These
low values for C
ADJ
will have little to no effect on soft-start.
There are example start-up plots for C
ADJ
equal to 1nF and
10nF in the Typical Performance Characteristics.
External Sense Resistor
The V
DS
of a PFET will tend to vary significantly over tem-
perature. This will result an equivalent variation in current
limit. To improve current limit accuracy an external sense
resistor can be connected from V
IN
to the source of the
PFET, as shown in Figure 5
20034627
FIGURE 5. Current Sensing by External Resistor
L
www.national.com
11
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| LM3485MM | Hysteretic PFET Buck Controller |
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| LM3488 | 500kHz and 1MHz High Efficiency 1.5A Switching Regulators; Package: SO; No of Pins: 8; Temperature Range: -40?°C to 85?°C |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
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| LM3485EVAL | 功能描述:電源管理IC開發(fā)工具 LM3485MM EVAL BOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| LM3485LED | 制造商:Texas Instruments 功能描述: |
| LM3485LED EVAL | 功能描述:板上安裝溫度傳感器 LM3485LED EVAL Brd RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風格: 封裝 / 箱體: 設備功能:Temperature and Humidity Sensor |
| LM3485LEDEVAL | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述: |
| LM3485MM | 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風格: 封裝 / 箱體:CPAK |
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