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参数资料
| 型号： | LM2595J-3.3-QML |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 2.6 A SWITCHING REGULATOR, 173 kHz SWITCHING FREQ-MAX, CDIP16 |
| 封装： | CERAMIC, DIP-16 |
| 文件页数： | 9/33页 |
| 文件大小： | 1016K |
| 代理商： | LM2595J-3.3-QML |
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Block Diagram
Application Information
PIN FUNCTIONS
+V
IN — This is the positive input supply for the IC switching
regulator. A suitable input bypass capacitor must be present
at this pin to minimize voltage transients and to supply the
switching currents needed by the regulator.
Ground — Circuit ground.
Output — Internal switch. The voltage at this pin switches
between (+V
IN VSAT) and approximately 0.5V, with a duty
cycle of approximately V
OUT/VIN. To minimize coupling to
sensitive circuitry, the PC board copper area connected to
this pin should be kept to a minimum.
Feedback — Senses the regulated output voltage to com-
plete the feedback loop.
ON/OFF — Allows the switching regulator circuit to be shut
down using logic level signals thus dropping the total input
supply current to approximately 85 A. Pulling this pin below
a threshold voltage of approximately 1.3V turns the regulator
on, and pulling this pin above 1.3V (up to a maximum of 25V)
shuts the regulator down. If this shutdown feature is not
needed, the ON/OFF pin can be wired to the ground pin or it
can be left open, in either case the regulator will be in the ON
condition.
EXTERNAL COMPONENTS
INPUT CAPACITOR
C
IN — A low ESR aluminum or tantalum bypass capacitor is
needed between the input pin and ground pin. It must be lo-
cated near the regulator using short leads. This capacitor
prevents large voltage transients from appearing at the in-
put, and provides the instantaneous current needed each
time the switch turns on.
The important parameters for the Input capacitor are the
voltage rating and the RMS current rating. Because of the
relatively high RMS currents flowing in a buck regulator’s in-
put capacitor, this capacitor should be chosen for its RMS
current rating rather than its capacitance or voltage ratings,
although the capacitance value and voltage rating are di-
rectly related to the RMS current rating.
The RMS current rating of a capacitor could be viewed as a
capacitor’s power rating. The RMS current flowing through
the capacitors internal ESR produces power which causes
the internal temperature of the capacitor to rise. The RMS
current rating of a capacitor is determined by the amount of
current required to raise the internal temperature approxi-
mately 10C above an ambient temperature of 105C. The
ability of the capacitor to dissipate this heat to the surround-
ing air will determine the amount of current the capacitor can
safely sustain. Capacitors that are physically large and have
a large surface area will typically have higher RMS current
ratings. For a given capacitor value, a higher voltage electro-
lytic capacitor will be physically larger than a lower voltage
capacitor, and thus be able to dissipate more heat to the sur-
rounding air, and therefore will have a higher RMS current
rating.
The consequences of operating an electrolytic capacitor
above the RMS current rating is a shortened operating life.
The higher temperature speeds up the evaporation of the ca-
pacitor’s electrolyte, resulting in eventual failure.
Selecting an input capacitor requires consulting the manu-
facturers data sheet for maximum allowable RMS ripple cur-
rent. For a maximum ambient temperature of 40C, a gen-
eral guideline would be to select a capacitor with a ripple
current rating of approximately 50% of the DC load current.
For ambient temperatures up to 70C, a current rating of
75% of the DC load current would be a good choice for a
conservative design. The capacitor voltage rating must be at
least 1.25 times greater than the maximum input voltage,
and often a much higher voltage capacitor is needed to sat-
isfy the RMS current requirements.
A graph shown in
Figure 13 shows the relationship between
an electrolytic capacitor value, its voltage rating, and the
RMS current it is rated for. These curves were obtained from
the Nichicon “PL” series of low ESR, high reliability electro-
DS012565-21
FIGURE 12.
www.national.com
17
相关PDF资料 |
PDF描述 |
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| LM2595-5.0MDC | 2.6 A SWITCHING REGULATOR, 173 kHz SWITCHING FREQ-MAX, UUC |
| LM2595-5.0MWC | 2.6 A SWITCHING REGULATOR, 173 kHz SWITCHING FREQ-MAX, UUC |
| LM2595-3.3MDC | 2.6 A SWITCHING REGULATOR, 173 kHz SWITCHING FREQ-MAX, UUC |
| LM2595J-5.0-QML | 2.6 A SWITCHING REGULATOR, 173 kHz SWITCHING FREQ-MAX, CDIP16 |
| LM2599-5.0MWC | 7.5 A SWITCHING REGULATOR, 173 kHz SWITCHING FREQ-MAX, UUC |
相关代理商/技术参数 |
参数描述 |
|---|---|
| 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 |
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