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参数资料
| 型号： | LM2637MWC |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, UUC |
| 封装： | WAFER |
| 文件页数： | 4/20页 |
| 文件大小： | 404K |
| 代理商： | LM2637MWC |
Applications Information (Continued)
That is, if f
z = 1.32 kHz, fp = 153 kHz, and A = 4.8x10
6
F,
then the cutoff frequency will be 50 kHz, the phase margin
will be 72, and the DC gain will be that of the error amplifier.
See
Figure 8.
The compensation network component values can be deter-
mined by
Equation (9), since the values of f
z,fp and A are
now known. To more conveniently calculate the values,
Equation (9) can be rearranged as follows:
(11)
Notice there are three equations but four variables. So one
of the variables can be chosen arbitrarily. Since the current
driving capability of the error amplifier is limited to around 3
mA, it is a good idea to have a high impedance path from
EAO to FB. From
Equation (11) it can be told that a larger R
2
will result in a smaller C
1,C2 and a larger R1. Calculations
show that the following combination is a good one: R
2 =
51
,C
1 = 0.022 f, R1 = 5.6 k,C2 = 820 pF.
For a different application or different type of output capaci-
tors, a different compensation scheme may be necessary.
The user can either follow the steps above to figure the ap-
propriate component values or contact National for help.
Linear Section — The linear section is designed for high con-
trol bandwidth operation. The phase margin and cutoff fre-
quency depends on the external N-FET, output capacitors
and their ESR. As a rule of thumb, the designer can choose
any capacitance from 50 F to 4000 F, with a total ESR of
10 m
to 100 m. The larger the capacitance, the lower the
bandwidth. The above capacitors usually result in a control
bandwidth of 250 kHz to 1.2 MHz.
DS100848-17
FIGURE 6. Buck Converter from a Control Viewpoint
DS100848-18
FIGURE 7. Control-to-Output Bode Plots
DS100848-19
FIGURE 8. Loop Bode Plots
www.national.com
12
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| LM2638M | 制造商:Texas Instruments 功能描述: |
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| LM2638MX | 功能描述:IC MOTHERBRD PWR SUPPLY 24-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 应用说明:Ultrasound Imaging Systems Application Note 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:37 系列:- 应用:医疗用超声波成像，声纳 电流 - 电源:- 电源电压:2.37 V ~ 6 V 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:56-WFQFN 裸露焊盘 供应商设备封装:56-TQFN-EP（8x8） 包装:管件 |
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