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| 型号： | LM22673MRX-5.0/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 12/27页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 5V 3A 8PSOP |
| 产品培训模块： | SIMPLE SWITCHER® Regulators LM315x & LM2267x SIMPLE SWITCHER® and WEBENCH |
| 标准包装： | 2,500 |
| 系列： | SIMPLE SWITCHER® |
| 类型： | 降压（降压） |
| 输出类型： | 固定 |
| 输出数： | 1 |
| 输出电压： | 5V |
| 输入电压： | 4.5 V ~ 42 V |
| PWM 型： | 电压模式 |
| 频率 - 开关： | 500kHz |
| 电流 - 输出： | 3A |
| 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 Width）裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-PSOP-EP |
| 配用： | 551600236-001-ND - WEBENCH BUILD IT LM2267X 8-PSOP LM22673EVAL/NOPB-ND - BOARD EVALUATION FOR LM22673 |
| 其它名称： | LM22673MRX-5.0 |
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SNVS586N – SEPTEMBER 2008 – REVISED APRIL 2013
(9)
where F sw is the switching frequency and V in should be taken at its maximum value, for the given application.
The above formula provides a guide to select the value of the inductor L; the nearest standard value will then be
used in the circuit.
Once the inductor is selected, the actual ripple current can be found from the equation shown below:
(10)
Increasing the inductance will generally slow down the transient response but reduce the output voltage ripple.
Reducing the inductance will generally improve the transient response but increase the output voltage ripple.
The inductor must be rated for the peak current, I PK , in a given application, to prevent saturation. During normal
loading conditions, the peak current is equal to the load current plus 1/2 of the inductor ripple current.
During an overload condition, as well as during certain load transients, the controller may trip current limit. In this
case the peak inductor current is given by I CL , found in the Electrical Characteristics table. Good design practice
requires that the inductor rating be adequate for this overload condition. If the inductor is not rated for the
maximum expected current, it can saturate resulting in damage to the LM22673 and/or the power diode.
This consideration highlights the value of the current limit adjust feature of the LM22673.
INPUT CAPACITOR
The input capacitor selection is based on both input voltage ripple and RMS current. Good quality input
capacitors are necessary to limit the ripple voltage at the VIN pin while supplying most of the regulator current
during switch on-time. Low ESR ceramic capacitors are preferred. Larger values of input capacitance are
desirable to reduce voltage ripple and noise on the input supply. This noise may find its way into other circuitry,
sharing the same input supply, unless adequate bypassing is provided. A very approximate formula for
determining the input voltage ripple is shown below:
(11)
Where V ri is the peak-to-peak ripple voltage at the switching frequency. Another concern is the RMS current
passing through this capacitor. The following equation gives an approximation to this current:
(12)
The capacitor must be rated for at least this level of RMS current at the switching frequency.
All ceramic capacitors have large voltage coefficients, in addition to normal tolerances and temperature
coefficients. To help mitigate these effects, multiple capacitors can be used in parallel to bring the minimum
capacitance up to the desired value. This may also help with RMS current constraints by sharing the current
among several capacitors. Many times it is desirable to use an electrolytic capacitor on the input, in parallel with
the ceramics. The moderate ESR of this capacitor can help to damp any ringing on the input supply caused by
long power leads. This method can also help to reduce voltage spikes that may exceed the maximum input
voltage rating of the LM22673.
It is good practice to include a high frequency bypass capacitor as close as possible to the LM22673. This small
case size, low ESR, ceramic capacitor should be connected directly to the VIN and GND pins with the shortest
possible PCB traces. Values in the range of 0.47 μF to 1 μF are appropriate. This capacitor helps to provide a
low impedance supply to sensitive internal circuitry. It also helps to suppress any fast noise spikes on the input
supply that may lead to increased EMI.
12
Product Folder Links: LM22673
Copyright ? 2008–2013, Texas Instruments Incorporated
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相关代理商/技术参数 |
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|---|---|
| LM22673MRX-ADJ | 制造商:Texas Instruments 功能描述:Conv DC-DC Single Inv/Step Down 4.5V to 42V 8-Pin PSOP EP T/R |
| LM22673MRX-ADJ/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 |
| LM22673QMR-5.0/NOPB | 制造商:Texas Instruments 功能描述:IC REG BUCK 5V 3A 8SOPWRPAD 制造商:Texas Instruments 功能描述:42V, 3A SIMPLE SWITCHER Step-Down Volta |
| LM22673QMR-ADJ/NOPB | 制造商:Texas Instruments 功能描述:IC REG BUCK ADJ 3A 8SOPWRPAD |
| LM22673QMRE-5.0/NOPB | 制造商:Texas Instruments 功能描述:IC REG BUCK 5V 3A 8SOPWRPAD 制造商:Texas Instruments 功能描述:42V, 3A SIMPLE SWITCHER Step-Down Volta |
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