參數(shù)資料
型號(hào)： LM2746MXA
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類(lèi)： 穩(wěn)壓器
英文描述： Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller
中文描述： SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO14
封裝： PLASTIC, TSSOP-14
文件頁(yè)數(shù)： 17/24頁(yè)
文件大?。?/td> 1087K
代理商： LM2746MXA
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 1.0VP-P for the LM2746. The
inductor and output capacitor create a double pole at fre-
quency f
, and the capacitor ESR and capacitance create a
single zero at frequency f
ESR
. For this example, with V
IN
=
3.3V, 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
is the output
voltage divided by output current. The power stage transfer
function G
is given by the following equation, and
Figure
13
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 4.5kHz causes the phase to drop to
approximately -130 at around 10kHz. The ESR zero, at
20.3kHz, provides a +90 boost that prevents the phase from
dropping to -180
o
. If this loop were left uncompensated, the
bandwidth would be approximately 10kHz and the phase
margin 53. 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 un-
stable 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
20147764
FIGURE 12. Power Stage and Error Amp
20147769
20147770
FIGURE 13. Power Stage Gain and Phase
L
www.national.com
17
相關(guān)PDF資料
PDF描述
LM2746MXAX Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM2746MXA/NOPB 功能描述:IC REG CTRLR BUCK PWM VM 14TSSOP RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤(pán) 包裝:帶卷 (TR)
LM2746MXAX 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller
LM2746MXAX/NOPB 功能描述:IC REG CTRLR BUCK PWM VM 14TSSOP RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:100% 電源電壓:8.2 V ~ 30 V 降壓:無(wú) 升壓:無(wú) 回掃:是 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:是 工作溫度:0°C ~ 70°C 封裝/外殼:8-DIP（0.300"，7.62mm） 包裝:管件 產(chǎn)品目錄頁(yè)面:1316 (CN2011-ZH PDF)
LM2747 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Synchronous Buck Controller with Pre-bias Startup, and Optional Clock Synchronization
LM2747-19AEVAL 功能描述:電源管理IC開(kāi)發(fā)工具 LM2747 EVAL BOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類(lèi)型:Battery Management 工具用于評(píng)估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V
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