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| 型号： | TPS54140DGQR |
| 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： | 27/46页 |
| 文件大小： | 1778K |
| 代理商： | TPS54140DGQR |
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Under Voltage Lock Out Set Point
Output Voltage and Feedback Resistors Selection
Compensation
www.ti.com .............................................................................................................................................................................................. SLVS889 – OCTOBER 2008
The Under Voltage Lock Out (UVLO) can be adjusted using an external voltage divider on the EN pin of the
TPS54140. The UVLO has two thresholds, one for power up when the input voltage is rising and one for power
down or brown outs when the input voltage is falling. For the example design, the supply should turn on and start
switching once the input voltage increases above 7.25V (enabled). After the regulator starts switching, it should
continue to do so until the input voltage falls below 6.25V (UVLO stop).
The programmable UVLO and enable voltages are set using a resistor divider between Vin and ground to the EN
pin. Equation 2 through Equation 3 can be used to calculate the resistance values necessary. For the example
application, a 332k
between Vin and EN and a 61.9k between EN and ground are required to produce the
7.25 and 6.25 volt start and stop voltages.
For the example design, 10.0 k
was selected for R2. Using Equation 1, R1 is calculated as 31.25 k. The
nearest standard 1% resistor is 31.6 k
. Due to current leakage of the VSENSE pin, the current flowing through
the feedback network should be greater than 1
A in order to maintain the output voltage accuracy. This
requirement makes the maximum value of R2 equal to 800 k
. Choosing higher resistor values will decrease
quiescent current and improve efficiency at low output currents but may introduce noise immunity problems.
There are several industry techniques used to compensate DC/DC regulators. The method presented here yields
high phase margins. For most conditions, the regulator will have a phase margin between 60 and 90 degrees.
The method presented here ignores the effects of the slope compensation that is internal to the TPS54140.
Since the slope compensation is ignored, the actual cross over frequency is usually lower than the cross over
frequency used in the calculations.
Use SwitcherPro software for a more accurate design.
The uncompensated regulator will have a dominant pole, typically located between 300 Hz and 3 kHz, due to the
output capacitor and load resistance and a pole due to the error amplifier. One zero exists due to the output
capacitor and the ESR. The zero frequency is higher than either of the two poles.
If left uncompensated, the double pole created by the error amplifier and the modulator would lead to an unstable
regulator. To stabilize the regulator, one pole must be canceled out. One design approach is to locate a
compensating zero at the modulator pole. Then select a cross over frequency that is higher than the modulator
pole. The gain of the error amplifier can be calculated to achieve the desired cross over frequency. The capacitor
used to create the compensation zero along with the output impedance of the error amplifier form a low
frequency pole to provide a minus one slope through the cross over frequency. Then a compensating pole is
added to cancel the zero due to the output capacitors ESR. If the ESR zero resides at a frequency higher than
the switching frequency then it can be ignored.
Copyright 2008, Texas Instruments Incorporated
33
Product Folder Link(s): TPS54140
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| TPS54140EVM-429 | 功能描述:电源管理IC开发工具 1.5A,25-42V In SWIFT Cnvrtr 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 |
| TPS54140-Q1 | 制造商:TI 制造商全称:Texas Instruments 功能描述:1.5-A 42-V STEP-DOWN SWIFTa?￠ DC/DC CONVERTER WITH Eco-modea?￠ CONTROL |
| TPS54140QDGQRQ1 | 功能描述:直流/直流开关调节器 AC 3.5-42V Inp,1.5A 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 |
| TPS54140QDRCRQ1 | 功能描述:直流/直流开关调节器 AC 3.5-42V Inp,1.5A 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 |
| TPS54160 | 制造商:TI 制造商全称:Texas Instruments 功能描述:1.5-A, 60-V, STEP-DOWN SWIFT DC/DC CONVERTER WITH ECO-MODE |
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