- 您現在的位置：買賣IC網 > PDF目錄385484 > LM3743MMX-300 (NATIONAL SEMICONDUCTOR CORP) N-Channel FET Synchronous Buck Controller for Low Output Voltages PDF資料下載
參數資料
| 型號： | LM3743MMX-300 |
| 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, 345 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封裝： | PLASTIC, MSOP-10 |
| 文件頁數： | 18/23頁 |
| 文件大小： | 1145K |
| 代理商： | LM3743MMX-300 |
Application Information
(Continued)
One popular method for selecting the compensation compo-
nents is to create Bode plots of gain and phase for the power
stage and error amplifier. Combined, they make the overall
bandwidth and phase margin of the regulator easy to see.
Software tools such as Excel, MathCAD, and Matlab are
useful for showing how changes in compensation or the
power stage affect system gain and phase.
The power stage modulator provides a DC gain A
that is
equal to the input voltage divided by the peak-to-peak value
of the PWM ramp. This ramp is 1.0V
for the LM3743.
The inductor and output capacitor create a double pole at
frequency f
, and the capacitor ESR and capacitance cre-
ate a single zero at frequency f
ESR
. For this example, with
V
IN
= 5.0V, these quantities are:
In the equation for f
, the variable R
is the power stage
resistance, and represents the inductor DCR plus the on
resistance of the top power MOSFET. R
O
is the output
voltage divided by output current. The power stage transfer
function G
PS
is given by the following equation, and
Figure 9
shows Bode plots of the phase and gain in this example.
a = LC
O
(R
O
+ R
C
)
b = L + C
O
(R
O
R
L
+ R
O
R
C
+ R
C
R
L
)
c = R
O
+ R
L
The double pole at 6 kHz causes the phase to drop to
approximately -140 at around 15 kHz. The ESR zero, at
33.9 kHz, provides a +90 boost that prevents the phase
from dropping to -180
o
. If this loop were left uncompensated,
the bandwidth would be approximately 15 kHz and the
phase margin 40. In theory, the loop would be stable, but
would suffer from poor DC regulation (due to the low DC
gain) and would be slow to respond to load transients (due to
the low bandwidth.) In practice, the loop could easily become
unstable due to tolerances in the output inductor, capacitor,
or changes in output current, or input voltage. Therefore, the
loop is compensated using the error amplifier and a few
passive components.
For this example, a Type III, or three-pole-two-zero approach
gives optimal bandwidth and phase.
In most voltage mode compensation schemes, including
Type III, a single pole is placed at the origin to boost DC gain
20177413
FIGURE 8. Power Stage and Error Amp
20177418
20177419
FIGURE 9. Power Stage Gain and Phase
L
www.national.com
18
相關PDF資料 |
PDF描述 |
|---|---|
| LM377 | Dual 2 watt Audio Amplifier |
| LM377N | Dual 2 watt Audio Amplifier |
| LM382 | Low Noise Dual Preamplifier |
| LM383 | 7W Audio Power Amplifier |
| LM383AT | 7W Audio Power Amplifier |
相關代理商/技術參數 |
參數描述 |
|---|---|
| LM3743MMX-300/NOPB | 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 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 輸出端數量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 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 |
| LM3753SQNOPB | 制造商:National Semiconductor 功能描述:Voltage Mode PWM Controller 0.6V to 3.6V 50A 32-Pin LLP EP T/R |
| LM3753SQX/NOPB | 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 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，3分鐘左右您將得到回復。