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參數(shù)資料
| 型號： | LM2595 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Octal Buffers/Drivers With 3-State Outputs 20-SOIC -40 to 85 |
| 中文描述： | SIMPLE SWITCHER系列電源轉(zhuǎn)換器150千赫1A步降穩(wěn)壓器 |
| 文件頁數(shù)： | 24/29頁 |
| 文件大?。?/td> | 935K |
| 代理商： | LM2595 |
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Application Information
(Continued)
Because of differences in the operation of the inverting regu-
lator, the standard design procedure is not used to select the
inductor value. In the majority of designs, a 68 μH, 1.5A in-
ductor is the best choice. Capacitor selection can also be
narrowed down to just a few values. Using the values shown
in Figure 25will provide good results in the majority of invert-
ing designs.
This type of inverting regulator can require relatively large
amounts of input current when starting up, even with light
loads. Input currents as high as the LM2595 current limit (ap-
prox 1.5A) are needed for at least 2 ms or more, until the out-
put reaches its nominal output voltage. The actual time de-
pends on the output voltage and the size of the output
capacitor. Input power sources that are current limited or
sources that can not deliver these currents without getting
loaded down, may not work correctly. Because of the rela-
tively high startup currents required by the inverting topology,
the delayed startup feature (C1, R
and R
) shown in Figure
25 is recommended. By delaying the regulator startup, the
input capacitor is allowed to charge up to a higher voltage
before the switcher begins operating.Aportion of the high in-
put current needed for startup is now supplied by the input
capacitor (C
). For severe start up conditions, the input ca-
pacitor can be made much larger than normal.
INVERTING REGULATOR SHUTDOWN METHODS
To use the ON /OFF pin in a standard buck configuration is
simple, pull it below 1.3V (
@
25C, referenced to ground) to
turn regulator ON, pull it above 1.3V to shut the regulator
OFF. With the inverting configuration, some level shifting is
required, because the ground pin of the regulator is no
longer at ground, but is now setting at the negative output
voltage level. Two different shutdown methods for inverting
regulators are shown in Figure 27 and Figure 28
DS012565-39
This circuit has hysteresis
Regulator starts switching at V
IN
= 13V
Regulator stops switching at V
IN
= 8V
FIGURE 24. Undervoltage Lockout with Hysteresis for Inverting Regulator
DS012565-40
C
IN
:
120 μF/50V Elec. Panasonic HFQ
C
OUT
:
— 22 μF/20V Tant. Sprague 595D
120 μF/25V Elec. Panasonic HFQ
— 220 μF/25V Tant. Sprague 595D
FIGURE 25. Inverting 5V Regulator with Delayed Startup
DS012565-41
FIGURE 26. Inverting Regulator Typical Load Current
www.national.com
24
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相關(guān)代理商/技術(shù)參數(shù) |
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| LM2595ADPBCKGEVB | 功能描述:電源管理IC開發(fā)工具 LM2595ADJ D2PAK BUCK DB 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 |
| LM2595ATPBCKGEVB | 功能描述:電源管理IC開發(fā)工具 LM2595ADJ TO220 BUCK DB 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 |
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| LM2595DSADJR4G | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 1A BUCK SW REG 150KHZ RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| LM2595S12 | 制造商:Texas Instruments 功能描述:SWITCHING REG, 1A 12V, SMD, 2595 制造商:Texas Instruments 功能描述:SWITCHING REG, 1A 12V, SMD, 2595; Primary Input Voltage:24V; No. of Outputs:1; Output Voltage:12V; Output Current:1A; Voltage Regulator Case Style:TO-263; No. of Pins:5; Operating Temperature Min:-25C; Operating Temperature ;RoHS Compliant: Yes |
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