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参数资料
| 型号： | LM2574DW-ADJR2 |
| 厂商： | MOTOROLA INC |
| 元件分类： | 稳压器 |
| 英文描述： | 1.8 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | PLASTIC, SO-16 |
| 文件页数： | 4/24页 |
| 文件大小： | 396K |
| 代理商： | LM2574DW-ADJR2 |
LM2574
12
MOTOROLA ANALOG IC DEVICE DATA
Procedure (Adjustable Output Version: LM2574–ADJ)
Procedure
Example
4. Inductor Selection (L1)
A. Use the following formula to calculate the inductor Volt x
microsecond [V x
s] constant:
B. Match the calculated E x T value with the corresponding
number on the vertical axis of the Inductor Value Selection
Guide shown in Figure 23. This E x T constant is a measure
of the energy handling capability of an inductor and is
dependent upon the type of core, the core area, the number
of turns, and the duty cycle.
C. Next step is to identify the inductance region intersected by
the E x T value and the maximum load current value on the
horizontal axis shown in Figure 27.
D. From the inductor code, identify the inductor value. Then
select an appropriate inductor from Table 2. The inductor
chosen must be rated for a switching frequency of 52 kHz
and for a current rating of 1.15 x ILoad. The inductor current
rating can also be determined by calculating the inductor
peak current:
where ton is the “on” time of the power switch and
For additional information about the inductor, see the inductor
section in the “External Components” section of this data
sheet.
ton +
Vout
V
in
x
1.0
fosc
Ip(max) + ILoad(max) )
V
in * Vout ton
2L
ExT
+ (V
in *
Vout)
Vout
V
in
x
106
F[Hz]
Vx
ms
4. Inductor Selection (L1)
A.
B.
C. ILoad(max) = 0.4 A
Inductance Region = 1000
D. Proper inductor value = 1000
H
Choose the inductor from Table 2.
ExT
+ (40 * 24) x 24
40
x
1000
52
+ 105 Vx ms
ExT
+ 185 Vx ms
Calculate E x T Vx
ms constant :
5. Output Capacitor Selection (Cout)
A. Since the LM2574 is a forward–mode switching regulator with
voltage mode control, its open loop 2–pole–1–zero frequency
characteristic has the dominant pole–pair determined by the
output capacitor and inductor values.
For stable operation, the capacitor must satisfy the following
requirement:
B. Capacitor values between 10
F and 2000 F will satisfy the
loop requirements for stable operation. To achieve an
acceptable output ripple voltage and transient response, the
output capacitor may need to be several times larger than the
above formula yields.
C. Due to the fact that the higher voltage electrolytic capacitors
generally have lower ESR (Equivalent Series Resistance)
numbers, the output capacitor’s voltage rating should be at
least 1.5 times greater than the output voltage. For a 5.0 V
regulator, a rating of at least 8.0 V is appropriate, and a 10 V
or 16V rating is recommended.
Cout w 13, 300
V
in(max)
Vout xL mH
mF
5. Output Capacitor Selection (Cout)
A.
To achieve an acceptable ripple voltage, select
Cout = 100 F electrolytic capacitor.
Cout w 13, 300 x
40
24 x 1000
+ 22.2 mF
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相关代理商/技术参数 |
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| LM2574DW-ADJR2G | 功能描述:直流/直流开关调节器 500mA Adj. Step Down RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| LM2574HV | 制造商:NSC 制造商全称:National Semiconductor 功能描述: |
| LM2574HVM-12 | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| LM2574HVM-12/NOPB | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| LM2574HVM-12/NOPB | 制造商:Texas Instruments 功能描述:DC/DC Converter IC |
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