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參數(shù)資料
| 型號： | LM25010 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 42V, 1.0A Step-Down Switching Regulator |
| 中文描述： | 42V的1.0安培降壓型開關(guān)穩(wěn)壓器 |
| 文件頁數(shù)： | 11/17頁 |
| 文件大?。?/td> | 776K |
| 代理商： | LM25010 |
Current Limit
(Continued)
mode. The load current (I
) is equal to the current limit
threshold plus half the ripple current (
I/2). The ripple ampli-
tude (
I) is calculated from:
(9)
The current limit threshold can be increased by connecting
an external resistor (R
CL
) between SGND and ISEN. R
typically is less than 1
, and the calculation of its value is
explained in the Applications Information section. If the cur-
rent limit threshold is increased by adding R
, the maximum
continuous load current should not exceed 1.5A, and the
peak current out of the SW pin should not exceed 2A.
N - Channel Buck Switch and
Driver
The LM25010 integrates an N-Channel buck switch and
associated floating high voltage gate driver. The peak cur-
rent through the buck switch should not exceed 2A, and the
load current should not exceed 1.5A. The gate driver circuit
is powered by the external bootstrap capacitor between BST
and SW (C4), which is recharged each off-time from V
through the internal high voltage diode. The minimum off-
time, nominally 260 ns, ensures sufficient time during each
cycle to recharge the bootstrap capacitor. A 0.022 μF ce-
ramic capacitor is recommended for C4.
Soft-Start
The soft-start feature allows the regulator to gradually reach
a steady state operating point, thereby reducing startup
stresses and current surges. At turn-on, while V
CC
is below
the under-voltage threshold (t1 in Figure 1), the SS pin is
internally grounded, and V
is held at 0V. When V
exceeds the under-voltage threshold (UVLO) an internal
11.5 μA current source charges the external capacitor (C6)
at the SS pin to 2.5V (t2 in Figure 1). The increasing SS
voltage at the non-inverting input of the regulation compara-
tor gradually increases the output voltage from zero to the
desired value. The soft-start feature keeps the load inductor
current from reaching the current limit threshold during
start-up, thereby reducing inrush currents.
An internal switch grounds the SS pin if V
is below the
under-voltage lock-out threshold, if a thermal shutdown oc-
curs, or if the circuit is shutdown using the RON/SD pin.
Thermal Shutdown
The LM25010 should be operated below the Maximum Op-
erating Junction Temperature rating. If the junction tempera-
ture increases during a fault or abnormal operating condi-
tion, the internal Thermal Shutdown circuit activates typically
at 175C. The Thermal Shutdown circuit reduces power
dissipation by disabling the buck switch and the on-timer,
and grounding the SS pin. This feature helps prevent cata-
strophic failures from accidental device overheating. When
the junction temperature reduces below approximately
155C (20C typical hysteresis), the SS pin is released and
normal operation resumes.
Applications Information
EXTERNAL COMPONENTS
The procedure for calculating the external components is
illustrated with a design example. Referring to the Block
Diagram, the circuit is to be configured for the following
specifications:
V
OUT
= 5V
V
IN
= 6V to 40V
F
S
= 175 kHz
Minimum load current = 200 mA
Maximum load current = 1.0A
Softstart time = 5 ms.
R1 and R2:
These resistors set the output voltage, and their
ratio is calculated from:
R1/R2 = (V
OUT
/2.5V) - 1
R1/R2 calculates to 1.0. The resistors should be chosen
from standard value resistors in the range of 1.0 k
- 10 k
.
A value of 1.0 k
will be used for R1 and for R2.
R
ON
, F
S
:
R
can be chosen using Equation 7 to set the
nominal frequency, or from Equation 6 if the on-time at a
particular V
is important. A higher frequency generally
means a smaller inductor and capacitors (value, size and
cost), but higher switching losses. A lower frequency means
(10)
20172720
FIGURE 4. Inductor Current - Current Limit Operation
L
www.national.com
11
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| LM25010_08 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:42V, 1.0A Step-Down Switching Regulator |
| LM25010EVAL | 功能描述:電源管理IC開發(fā)工具 LM25010 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 |
| LM25010MH | 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 |
| LM25010MH/NOPB | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 42V,1.0A STEP-DOWN SWITCHING REG 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 |
| LM25010MHX | 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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