收藏本站
LM2595
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
2
LM2595
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 3
GND
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
+V in
+V in
7
LM2595
+V in
+V in
2
LM2595
C in
100 m F
C1
0.1 m F
R1
47 k
5
ON/OFF 6
R2
47 k
GN
D
R2
15 k
Z1
1N5242B
R3
47 k
Q1
C in
100 m F 5
ON/OFF 3
GND
V th ≈ 13 V
2N3904
R1
NOTE: This picture does not show the complete circuit.
15 k
V out
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
reaches a predetermined threshold level with respect to the
ground Pin 3, which is determined by the following
expression:
NOTE: This picture does not show the complete circuit.
Figure 30. Undervoltage Lockout Circuit for
Buck ? Boost Converter
Adjustable Output, Low ? Ripple Power Supply
A 1.0 A output current capability power supply that
features an adjustable output voltage is shown in Figure 31.
This regulator delivers 1.0 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.
) 1.0 ) R2 V
V
th
[ V
Z1
R1
BE
(Q1)
http://onsemi.com
20
发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

*型号 *数量 厂商 批号 封装
添加更多采购

我的联系方式

*
*
*
相关PDF资料
R1S12-0505/P-R CONV DC/DC 1W 05VIN 05VOUT
AS1329B EB BOARD EVAL AS1329B
SJA7501-1-1/2-50-WHITE LOOP WHITE 1 1/2" X 50YD 0.12"
ECM08DRYH CONN EDGECARD 16POS DIP .156 SLD
CS51411EVB EVAL BOARD FOR CS51411 HI FREQ
RBM06DCWD CONN EDGECARD 12POS DIP .156 SLD
A9BAG-1604F FLEX CABLE - AFF16G/AF16/AFE16T
TARQ224K035 CAP TANT 0.22UF 35V 10% AXIAL
相关代理商/技术参数
LM2595ATPBCKGEVB 功能描述:电源管理IC开发工具 LM2595ADJ TO220 BUCK DB RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V
LM2595DSADJG 功能描述:直流/直流开关调节器 1A BUCK SW REG 150KHZ 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
LM2595DSADJR4G 功能描述:直流/直流开关调节器 1A BUCK SW REG 150KHZ 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
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
LM2595S-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
LM2595S12 制造商:Texas Instruments 功能描述:IC SWITCHING REG 1A 12V SMD 2595
LM2595S-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
LM2595S-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
    • 我
    • 采购
    • 搜索
    • 会员