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| 型号： | TPS54240DGQ |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING REGULATOR, 2500 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封装： | GREEN, PLASTIC, MSOP-10 |
| 文件页数： | 22/48页 |
| 文件大小： | 1759K |
| 代理商： | TPS54240DGQ |
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www.ti.com
SLVSAA6 – APRIL 2010
APPLICATION INFORMATION
Design Guide — Step-By-Step Design Procedure
This example details the design of a high frequency switching regulator design using ceramic output capacitors.
A few parameters must be known in order to start the design process. These parameters are typically determined
at the system level. For this example, we will start with the following known parameters:
Output Voltage
3.3 V
Transient Response 0 to 1.5A load step
ΔVout = 3 %
Maximum Output Current
2.5 A
Input Voltage
12 V nom. 10.8 V to 13.2 V
Output Voltage Ripple
1% of Vout
Start Input Voltage (rising VIN)
6.0 V
Stop Input Voltage (falling VIN)
5.5 V
Selecting the Switching Frequency
The first step is to decide on a switching frequency for the regulator. Typically, the user will want to choose the
highest switching frequency possible since this will produce the smallest solution size. The high switching
frequency allows for lower valued inductors and smaller output capacitors compared to a power supply that
switches at a lower frequency. The switching frequency that can be selected is limited by the minimum on-time of
the internal power switch, the input voltage and the output voltage and the frequency shift limitation.
Equation 12 and Equation 13 must be used to find the maximum switching frequency for the regulator, choose
the lower value of the two equations. Switching frequencies higher than these values will result in pulse skipping
or the lack of overcurrent protection during a short circuit.
The typical minimum on time, tonmin, is 135 ns for the TPS54240. For this example, the output voltage is 3.3 V
and the maximum input voltage is 13.2 V, which allows for a maximum switch frequency up to 2247 kHz when
including the inductor resistance, on resistance output current and diode voltage in Equation 12. To ensure
overcurrent runaway is not a concern during short circuits in your design use Equation 13 or the solid curve in
Figure 40 to determine the maximum switching frequency. With a maximum input voltage of 13.2 V, assuming a
diode voltage of 0.7 V, inductor resistance of 26 m
, switch resistance of 200 m, a current limit value of 3.5 A
and a short circuit output voltage of 0.2 V. The maximum switching frequency is approximately 4449 kHz.
For this design, a much lower switching frequency of 300 kHz is used. To determine the timing resistance for a
given switching frequency, use Equation 11 or the curve in Figure 39.
The switching frequency is set by resistor R3 shown in Figure 49 For 300 kHz operation a 412 kΩ resistor is
required.
Copyright 2010, Texas Instruments Incorporated
29
Product Folder Link(s): TPS54240
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TPS54240DGQ | 制造商:Texas Instruments 功能描述:IC STEP-DOWN DC/DC CONVERTER MSOP-10 |
| TPS54240DGQR | 功能描述:直流/直流开关转换器 3.5-42V Inp,2.5A,2.5 MHz SWIFT Converter 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 |
| TPS54240DRCR | 功能描述:直流/直流开关调节器 3.5-42Vin,2.5A SD Converter 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 |
| TPS54240DRCT | 功能描述:直流/直流开关调节器 3.5-42Vin,2.5A SD Converter 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 |
| TPS54240EVM-605 | 功能描述:电源管理IC开发工具 2.5A SWIFT Converter Eval Mod 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 |
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