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| 型号： | LM2574DW-ADJR2G |
| 厂商： | ON Semiconductor |
| 文件页数： | 11/26页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 0.5A 16SOICW |
| 标准包装： | 1,000 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.23 V ~ 37 V |
| 输入电压： | 4.75 V ~ 40 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 52kHz |
| 电流 - 输出： | 500mA |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SOIC（0.295"，7.50mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 16-SOIC W |
| 其它名称： | LM2574DW-ADJR2G-ND LM2574DW-ADJR2GOSTR |
LM2574, NCV2574
Procedure (Fixed Output Voltage Version) (continued) In order to simplify the switching regulator design, a step?by?step
design procedure and example is provided.
Procedure
5. Output Capacitor Selection (C out )
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 and an acceptable ripple voltage,
(approximately 1% of the output voltage) a value between
100 m F and 470 m F is recommended.
B. 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 at least 8.0 V is appropriate, and a 10 V
or 16 V rating is recommended.
Procedure (Adjustable Output Version: LM2574?ADJ)
Procedure
Given Parameters:
V out = Regulated Output Voltage
V in(max) = Maximum DC Input Voltage
I Load(max) = Maximum Load Current
1. Programming Output Voltage
To select the right programming resistor R1 and R2 value (see
Example
5. Output Capacitor Selection (C out )
A. C out = 100 m F to 470 m F standard aluminium electrolytic.
B. Capacitor voltage rating = 20 V.
Example
Given Parameters:
V out = 24 V
V in(max) = 40 V
I Load(max) = 0.4 A
1. Programming Output Voltage ( selecting R1 and R2)
Select R1 and R2 :
V out + V
1.0 )
Figure 2) use the following formula:
R2
ref R1
where V ref = 1.23 V
V out = 1.23 1.0 )
R2
R1
Select R1 = 1.0 k W
ref
Resistor R1 can be between 1.0 k W and 5.0 k W . (For best
temperature coefficient and stability with time, use 1% metal
film resistors).
R2 + R1
V out
V
* 1.0
+ 1.0 k
10 V
1.23 V
* 1.0
ref
R2 + R1
V out
V
* 1.0
R2 = 18.51 k W , choose a 18.7 k W metal film resistor.
2. Input Capacitor Selection (C in )
To prevent large voltage transients from appearing at the input
and for stable operation of the converter, an aluminium or
tantalum electrolytic bypass capacitor is needed between the
input pin +V in and ground pin Gnd. This capacitor should be
located close to the IC using short leads. This capacitor should
have a low ESR (Equivalent Series Resistance) value.
For additional information see input capacitor section in the
“EXTERNAL COMPONENTS” section of this data sheet.
3. Catch Diode Selection (D1)
A. Since the diode maximum peak current exceeds the
regulator maximum load current the catch diode current
rating must be at least 1.2 times greater than the maximum
load current. For a robust design, the diode should have a
current rating equal to the maximum current limit of the
LM2574 to be able to withstand a continuous output short.
B. The reverse voltage rating of the diode should be at least
1.25 times the maximum input voltage.
2. Input Capacitor Selection (C in )
A 22 m F aluminium electrolytic capacitor located near the
input and ground pin provides sufficient bypassing.
3. Catch Diode Selection (D1)
A. For this example, a 1.0 A current rating is adequate.
B. Use a 50 V MBR150 Schottky diode or any suggested
fast recovery diodes in Table 1.
http://onsemi.com
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| 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 |
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| LM2574HVM-15 | 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 |
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