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| 型号： | LM2594DADJR2G |
| 厂商： | ON Semiconductor |
| 文件页数： | 20/25页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 0.5A 8SOIC |
| 标准包装： | 2,500 |
| 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： | 4.5 V ~ 40 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 150kHz |
| 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： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-SOICN |
| 其它名称： | LM2594DADJR2G-ND LM2594DADJR2GOSTR |
LM2594
Delayed Startup
There are some applications, like the inverting regulator
already mentioned above, which require a higher amount of
startup current. In such cases, if the input power source is
+V in
+V in
7
LM2594
limited, this delayed startup feature becomes very useful.
To provide a time delay between the time when the input
voltage is applied and the time when the output voltage
R2
10 k
R3
47 k
C in
100 m F 5
ON/OFF 6
GN
D
comes up, the circuit in Figure 28 can be used. As the input
voltage is applied, the capacitor C1 charges up, and the
voltage across the resistor R2 falls down. When the voltage
Z1
1N5242B
on the ON/OFF pin falls below the threshold value 1.3 V, the
regulator starts up. Resistor R1 is included to limit the
maximum voltage applied to the ON/OFF pin. It reduces the
power supply noise sensitivity, and also limits the capacitor
R1
10 k
Q1
2N3904
V th ≈ 13 V
C1 discharge current, but its use is not mandatory.
When a high 50 Hz or 60 Hz (100 Hz or 120 Hz
respectively) ripple voltage exists, a long delay time can
cause some problems by coupling the ripple into the
ON/OFF pin, the regulator could be switched periodically
on and off with the line (or double) frequency.
NOTE: This picture does not show the complete circuit.
Figure 29. Undervoltage Lockout Circuit for
Buck Converter
The following formula is used to obtain the peak inductor
current:
x t on
[ Load
in
O
in
peak
2L 1
V
O
x 1.0 , and f osc + 52 kHz.
fosc
where t on +
in
O
+V in
C in
100 m F
+V in
7
C1
0.1 m F
R1
5
LM2594
ON/OFF 6
GN
D
I (V ) |V |) V
I )
in
|V |
V ) |V |
Under normal continuous inductor current operating
conditions, the worst case occurs when V in is minimal.
47 k
R2
47 k
+V in
+V in
7
LM2594
NOTE: This picture does not show the complete circuit.
Figure 28. Delayed Startup Circuitry
Undervoltage Lockout
Some applications require the regulator to remain off until
the input voltage reaches a certain threshold level. Figure 29
shows an undervoltage lockout circuit applied to a buck
regulator. A version of this circuit for buck ? boost converter
is shown in Figure 30. Resistor R3 pulls the ON/OFF pin
high and keeps the regulator off until the input voltage
R2
15 k
Z1
1N5242B
R1
15 k
R3
47 k
Q1
2N3904
C in
100 m F 5
ON/OFF 6
GN
D
V th ≈ 13 V
V out
reaches a predetermined threshold level with respect to the
ground Pin 3, which is determined by the following
NOTE: This picture does not show the complete circuit.
) 1.0 ) R2 V
expression:
V
th
[ V
Z1
R1
BE
(Q1)
Figure 30. Undervoltage Lockout Circuit for
Buck ? Boost Converter
Adjustable Output, Low ? Ripple Power Supply
A 0.5 A output current capability power supply that
features an adjustable output voltage is shown in Figure 31.
This regulator delivers 0.5 A into 1.2 V to 35 V output.
The input voltage ranges from roughly 3.0 V to 40 V. In order
to achieve a 10 or more times reduction of output ripple, an
additional L ? C filter is included in this circuit.
http://onsemi.com
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相关代理商/技术参数 |
参数描述 |
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| LM2594HVM-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 |
| LM2594HVM-12/NOPB | 功能描述:直流/直流开关转换器 150KHZ 0.5A STEP- DOWN VLTG REG 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 |
| LM2594HVM-12/NOPB | 制造商:Texas Instruments 功能描述:DC/DC Converter (DC-DC) / Switching Regu |
| LM2594HVM-3.3 | 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 |
| LM2594HVM-3.3/NOPB | 功能描述:直流/直流开关转换器 150KHZ 0.5A STEP- DOWN VLTG REG 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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