參數(shù)資料
型號(hào)： LM3743MMX-1000
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 穩(wěn)壓器
英文描述： N-Channel FET Synchronous Buck Controller for Low Output Voltages
中文描述： SWITCHING CONTROLLER, 1150 kHz SWITCHING FREQ-MAX, PDSO10
封裝： PLASTIC, MSOP-10
文件頁(yè)數(shù)： 19/23頁(yè)
文件大小： 1145K
代理商： LM3743MMX-1000
Application Information
(Continued)
as high as possible. Two zeroes f
and f
are placed at the
double pole frequency to cancel the double pole phase lag.
Then, a pole, f
P1
is placed at the frequency of the ESR zero.
A final pole f
is placed at one-half of the switching fre-
quency. The gain of the error amplifier transfer function is
selected to give the best bandwidth possible without violat-
ing the Nyquist stability criteria. In practice, a good crossover
point is one-fifth of the switching frequency, or 60 kHz for this
example. The generic equation for the error amplifier transfer
function is:
In this equation the variableA
is a ratio of the values of the
capacitance and resistance of the compensation compo-
nents, arranged as shown in
Figure 8
. A
is selected to
provide the desired bandwidth. A starting value of 80,000 for
A
should give a conservative bandwidth. Increasing the
value will increase the bandwidth, but will also decrease
phase margin. Designs with 45-60 are usually best because
they represent a good trade-off between bandwidth and
phase margin. In general, phase margin is lowest and gain
highest (worst-case) for maximum input voltage and mini-
mum output current. One method to select A
is to use an
iterative process beginning with these worst-case conditions.
1.
Increase A
EA
2.
Check overall bandwidth and phase margin
3.
Change V
to minimum and recheck overall bandwidth
and phase margin
4.
Change I
to maximum and recheck overall bandwidth
and phase margin
The process ends when both bandwidth and phase margin
are sufficiently high. For this example input voltage can vary
from 4.5V to 5.5V and output current can vary from 0 to 10A,
and after a few iterations a moderate gain factor of 90 dB is
used.
The error amplifier of the LM3743 has a unity-gain band-
width of 30 MHz. In order to model the effect of this limitation,
the open-loop gain can be calculated as:
The new error amplifier transfer function that takes into
account unity-gain bandwidth is:
The gain and phase of the error amplifier are shown in
Figure 10
.
In VM regulators, the top feedback resistor R2 forms a part
of the compensation. Setting R2 to 10 k
±
1%, usually gives
values for the other compensation resistors and capacitors
that fall within a reasonable range. (Capacitances
>
1 pF,
resistances
<
1 M
) C7, C8, C9, R4, and R5 are selected to
provide the poles and zeroes at the desired frequencies,
using the following equations:
20177423
20177424
FIGURE 10. Error Amp. Gain and Phase
L
www.national.com
19
相關(guān)PDF資料
PDF描述
LM3743MMX-300 N-Channel FET Synchronous Buck Controller for Low Output Voltages
LM377 Dual 2 watt Audio Amplifier
LM377N Dual 2 watt Audio Amplifier
LM382 Low Noise Dual Preamplifier
LM383 7W Audio Power Amplifier
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM3743MMX-1000/NOPB 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
LM3743MMX-300 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
LM3743MMX-300/NOPB 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
LM3753SQ 制造商:Texas Instruments 功能描述:IC BUCK CNTRL 2PH 32LLP
LM3753SQ/NOPB 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。

采購(gòu)需求

(若只采購(gòu)一條型號(hào)，填寫一行即可)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

發(fā)布成功！您可以繼續(xù)發(fā)布采購(gòu)。也可以進(jìn)入我的后臺(tái)，查看報(bào)價(jià)

*型號(hào) *數(shù)量 廠商 批號(hào) 封裝
添加更多采購(gòu)

我的聯(lián)系方式

*
*
*