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| 型号： | LM22673MRX-5.0/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 13/27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
OUTPUT CAPACITOR
The output capacitor is responsible for filtering the output voltage and supplying load current during transients.
Capacitor selection depends on application conditions as well as ripple and transient requirements. Best
performance is achieved with a parallel combination of ceramic capacitors and a low ESR SP? or POSCAP?
type. Very low ESR capacitors such as ceramics reduce the output ripple and noise spikes, while higher value
electrolytics or polymers provide large bulk capacitance to supply transients. Assuming very low ESR, the
following equation gives an approximation to the output voltage ripple:
(13)
Typically, a total value of 100 μF, or greater, is recommended for output capacitance.
In applications with V out less than 3.3V, it is critical that low ESR output capacitors are selected. This will limit
potential output voltage overshoots as the input voltage falls below the device normal operating range.
BOOT-STRAP CAPACITOR
The bootstrap capacitor between the BOOT pin and the SW pin supplies the gate current to turn on the N-
channel MOSFET. The recommended value of this capacitor is 10 nF and should be a good quality, low ESR
ceramic capacitor. In some cases it may be desirable to slow down the turn-on of the internal power MOSFET, in
order to reduce EMI. This can be done by placing a small resistor in series with the C boot capacitor. Resistors in
the range of 10 ? to 50 ? can be used. This technique should only be used when absolutely necessary, since it
will increase switching losses and thereby reduce efficiency.
OUTPUT VOLTAGE DIVIDER SELECTION
For output voltages between about 1.285V and 5V, the -ADJ option should be used, with an appropriate voltage
divider as shown in Figure 17 . The following equation can be used to calculate the resistor values of this divider:
(14)
A good value for R FBB is 1k ? . This will help to provide some of the minimum load current requirement and
reduce susceptibility to noise pick-up. The top of R FBT should be connected directly to the output capacitor or to
the load for remote sensing. If the divider is connected to the load, a local high-frequency bypass should be
provided at that location.
For output voltages of 5V, the -5.0 option should be used. In this case no divider is needed and the FB pin is
connected to the output. The approximate values of the internal voltage divider are as follows: 7.38k ? from the
FB pin to the input of the error amplifier and 2.55k ? from there to ground.
Both the -ADJ and -5.0 options can be used for output voltages greater than 5V, by using the correct output
divider. As mentioned in the Internal Compensation section, the -5.0 option is optimized for output voltages of 5V.
However, for output voltages greater than 5V, this option may provide better loop bandwidth than the -ADJ
option, in some applications. If the -5.0 option is to be used at output voltages greater than 5V, the following
equation should be used to determine the resistor values in the output divider:
(15)
Again a value of R FBB of about 1k ? is a good first choice.
Vout
R FBT
FB
R FBB
Figure 17. Resistive Feedback Divider
Copyright ? 2008–2013, Texas Instruments Incorporated
Product Folder Links: LM22673
13
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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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