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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)： | 11/32頁 |
| 文件大小： | 653K |
| 代理商： | LM27402SQX |
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30092640
FIGURE 15. Type lll Compensation Network Bode Plot
K
m is the mid-band gain of the compensator and can be esti-
mated by:
f
C (Hz) is the desired crossover frequency and is usually se-
lected between one tenth and one fifth of the switching fre-
quency (f
SW). The next set of equations show pole and zero
locations expressed in terms of the components in the com-
pensator feedback loop.
Depending on Q, the complex double pole can cause an in-
crease in gain at the LC resonant frequency and a precipitous
drop in phase. To compensate for the phase drop, it is com-
mon practice to place both compensator zeros created by the
type III compensation network at or slightly below the LC dou-
ble pole frequency. The other two poles should be located
beyond this point. One pole is located at the zero caused by
the output capacitor ESR and the other pole is placed at half
the switching frequency to roll off the higher frequency re-
sponse.
Conservative values for the compensation components can
be found by using the following equations.
After finding the compensation components it is wise to create
a bode plot of the loop response using all three transfer func-
tions. An illustration of the loop response is provided in Figure
16 .
30092644
FIGURE 16. Loop Response
It is important to always verify the stability by either observing
the load transient response or by using a network analyzer.
A phase margin between 45° and 70° is usually desired for
voltage mode controlled systems. Excessive phase margin
can cause slow system response to load transients and low
phase margin may cause an oscillatory load transient re-
sponse. If the load transient response peak deviation is larger
than desired, increasing f
C and recalculating the compensa-
tion components may help but usually at the expense of
phase margin.
MOSFET GATE DRIVE
To drive large MOSFETs with high gate charge, the LM27402
includes low impedance high-side and low-side gate drivers.
Low impedance gate drivers allow high current designs by
enabling fast transition times and increased efficiency. The
high-side gate drive is powered from a charge pump common
to the switch-node and the low-side gate is powered by the
VDD rail shown in Figure 17.
19
www.national.com
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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