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参数资料
| 型号： | LM22674MR-5.0/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 9/22页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 5V 0.5A 8PSOP |
| 产品培训模块： | SIMPLE SWITCHER® Regulators LM315x & LM2267x SIMPLE SWITCHER® and WEBENCH |
| 标准包装： | 95 |
| 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： | 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 Width）裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 8-PSOP-EP |
| 配用： | 551600236-001-ND - WEBENCH BUILD IT LM2267X 8-PSOP |
| 其它名称： | LM22674MR-5.0 LM22674MR-5.0-ND |
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SNVS590L – SEPTEMBER 2008 – REVISED APRIL 2013
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5
SAFE OPERATING ARE A
0.0
0.2 0.4 0.6 0.8 1.0
1.2
SHORT CIRCUIT VOLTAGE (v)
Figure 13. SOA
Soft-Start
The soft-start feature allows the regulator to gradually reach steady-state operation, thus reducing start-up
stresses. The internal soft-start feature brings the output voltage up in about 500 μs. This time is fixed and can
not be changed. Soft-start is reset any time the part is shut down or a thermal overload event occurs.
Boot-Strap Supply
The LM22674 incorporates a floating high-side gate driver to control the power MOSFET. The supply for this
driver is the external boot-strap capacitor connected between the BOOT pin and SW. A good quality 10 nF
ceramic capacitor must be connected to these pins with short, wide PCB traces. One reason the regulator
imposes a minimum off-time is to ensure that this capacitor recharges every switching cycle. A minimum load of
about 5 mA is required to fully recharge the boot-strap capacitor in the minimum off-time. Some of this load can
be provided by the output voltage divider, if used.
Thermal Protection
Internal thermal shutdown circuitry protects the LM22674 should the maximum junction temperature be
exceeded. This protection is activated at about 150°C, with the result that the regulator will shutdown until the
temperature drops below about 135°C.
Internal Compensation
The LM22674 has internal loop compensation designed to provide a stable regulator over a wide range of
external power stage components.
The internal compensation of the -ADJ option is optimized for output voltages below 5V. If an output voltage of
5V or greater is needed, the -5.0 option with an external resistor divider can be used.
Ensuring stability of a design with a specific power stage (inductor and output capacitor) can be tricky. The
LM22674 stability can be verified using the WEBENCH? Designer online circuit simulation tool at www.ti.com. A
quick start spreadsheet can also be downloaded from the online product folder.
The complete transfer function for the regulator loop is found by combining the compensation and power stage
transfer functions. The LM22674 has internal type III loop compensation, as detailed in Figure 14 . This is the
approximate "straight line" function from the FB pin to the input of the PWM modulator. The power stage transfer
function consists of a D.C. gain and a second order pole created by the inductor and output capacitor(s). Due to
the input voltage feedforward employed in the LM22674, the power stage D.C. gain is fixed at 20dB. The second
order pole is characterized by its resonant frequency and its quality factor (Q). For a first pass design, the
product of inductance and output capacitance should conform to the following equation:
(8)
Alternatively, this pole should be placed between 1.5kHz and 15kHz and is given by the equation shown below:
Copyright ? 2008–2013, Texas Instruments Incorporated
Product Folder Links: LM22674
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM22674MR-ADJ | 制造商:Texas Instruments 功能描述:REGULATOR, ADJ. VOLTAGE, 0.5A 8PSOP 制造商:Texas Instruments 功能描述:REGULATOR, ADJ. VOLTAGE, 0.5A 8PSOP; Primary Input Voltage:42V; No. of Outputs:1; Output Current:500mA; Voltage Regulator Case Style:SOP; No. of Pins:8; Operating Temperature Min:-40C; Operating Temperature Max:125C; SVHC:No SVHC ;RoHS Compliant: Yes |
| LM22674MR-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 |
| LM22674MRE-5.0 | 制造商:Texas Instruments 功能描述:SIMPLESWITCH 5.0V 4.5~42VIN 8PSOP 制造商:Texas Instruments 功能描述:SIMPLESWITCH, 5.0V 4.5~42VIN, 8PSOP 制造商:Texas Instruments 功能描述:SIMPLESWITCH, 5.0V 4.5~42VIN, 8PSOP, Primary Input Voltage:12V, No. of Outputs:1 |
| LM22674MRE-5.0/NOPB | 功能描述:直流/直流开关转换器 500MA,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 |
| LM22674MRE-5.0/NOPB | 制造商:Texas Instruments 功能描述:Switching Regulator IC |
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