參數(shù)資料
型號： LM27402SQX
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 穩(wěn)壓器
英文描述： SWITCHING CONTROLLER, 1350 kHz SWITCHING FREQ-MAX, QCC16
封裝： 4 X 4 MM, 0.80 MM HEIGHT, 0.65 MM PITCH, LLP-16
文件頁數(shù)： 10/32頁
文件大?。?/td> 653K
代理商： LM27402SQX
30092623
FIGURE 13. Control Loop Schematic Diagram
The powertrain consists of the filter inductor (L) with DCR
(R
DCR), output capacitor (COUT) with ESR (effective series re-
sistance R
ESR), and effective load resistance (RO). The error
amplifier (EA) regulates the feedback pin (FB) to 0.6V. The
passive compensation components around the error amplifier
help maintain system stability. Type III compensation is
shown in Figure 13. The PWM modulator establishes the duty
cycle command by comparing the error amplifier output
(COMP) with an internally generated ramp set at the switching
frequency.
The modulator gain, powertrain and compensator transfer
functions must be taken into consideration when obtaining the
total open loop transfer function. The PWM modulator adds a
DC gain to the open loop transfer function. In a basic voltage
mode system, the PWM gain will vary with input voltage.
However the LM27402 internal voltage feed-forward circuitry
maintains a constant PWM gain of 7:
The powertrain transfer function includes the output inductor
with DCR, output capacitor with ESR, and load resistance.
The inductor and capacitor create two complex poles at a fre-
quency described by:
A left half plane zero is created by the output capacitor ESR
located at a frequency described by:
The complete powertrain transfer function is:
The bode plot of the above transfer function can be seen in
30092698
FIGURE 14. Powertrain Bode Plot
The complex poles (f
LC) created by the filter inductor and out-
put capacitor cause a 180° phase shift as seen in Figure 14.
The phase is boosted back up to -90° by virtue of the output
capacitor ESR zero. The phase shift caused by the complex
poles must be compensated to stabilize the loop response.
The compensation network shown around the error amplifier
in Figure 13 creates two poles, two zeros and a pole at the
origin. Placing these poles and zeros at the correct frequen-
cies will optimize the loop response. The compensator trans-
fer function is:
The pole located at the origin provides high DC gain to opti-
mize DC load regulation performance. The other two poles
and two zeros can be located accordingly to stabilize the volt-
age mode loop depending on the power stage complex poles
and damping characteristic Q. Figure 15 is an illustration of
what the error amplifier compensation transfer function will
look like.
www.national.com
18
LM27402
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM27402SQX/NOPB 功能描述:DC/DC 開關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
LM27403 制造商:TI 制造商全稱:Texas Instruments 功能描述:Synchronous Buck Controller with Temperature-Compensated, Inductor-DCR-Based Overcurrent Protection and Programmable Thermal Shutdown
LM27403EVM 制造商:Texas Instruments 功能描述:LM27403EVM - Boxed Product (Development Kits)
LM27403EVM-POL600 制造商:Texas Instruments 功能描述:BOARD EVAL LM27403
LM27403SQ 制造商:TI 制造商全稱:Texas Instruments 功能描述:Synchronous Buck Controller with Temperature-Compensated, Inductor-DCR-Based Overcurrent Protection and Programmable Thermal Shutdown
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