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| 型号： | LM27402SQ |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 1350 kHz SWITCHING FREQ-MAX, QCC16 |
| 封装： | 4 X 4 MM, 0.80 MM HEIGHT, 0.65 MM PITCH, LLP-16 |
| 文件页数： | 11/32页 |
| 文件大小： | 653K |
| 代理商： | LM27402SQ |
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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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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM27402SQ/NOPB | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| LM27402SQEVAL/NOPB | 功能描述:电源管理IC开发工具 LM27402SQ EVAL BOARD 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 |
| LM27402SQX | 制造商:NSC 制造商全称:National Semiconductor 功能描述:High Performance Synchronous Buck Controller with DCR Current Sensing |
| LM27402SQX/NOPB | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| LM27403 | 制造商:TI 制造商全称: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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