- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄385477 > LM27241MTCX (NATIONAL SEMICONDUCTOR CORP) Synchronous Buck Regulator Controller for Mobile Systems PDF資料下載
參數(shù)資料
| 型號： | LM27241MTCX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Synchronous Buck Regulator Controller for Mobile Systems |
| 中文描述： | SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | PLASTIC, TSSOP-20 |
| 文件頁數(shù)： | 10/27頁 |
| 文件大?。?/td> | 1336K |
| 代理商： | LM27241MTCX |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁當前第10頁第11頁第12頁第13頁第14頁第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁
Operation Descriptions
GENERAL
The LM27241 is a synchronous buck controller using a
voltage-mode control topology. This topology was selected
to provide fixed-frequency PWM regulation at very low duty
cycles, in preference to current-mode control, because the
latter has inherent limitations in being able to achieve low
pulse widths due to blanking time requirements. Because of
a minimum pulse width of about 30ns for the LM27241, very
low duty cycles (low output, high input) are possible. The
main advantage of current-mode control is the fact that the
slope of its ramp (derived from the switch current), automati-
cally increases with increase in input voltage. This leads to
improved line rejection and fast response to line variations.
In typical voltage-mode control, the ramp is derived from the
clock, not from the switch current. But by using the input
voltage together with the clock signal to generate the ramp
as in the LM27241, this advantage of current-mode control
can in fact be completely replicated. The technique is called
line feedforward. In addition, the LM27241 features a user-
selectable Pulse-skip mode that significantly improves effi-
ciency at light loads by reducing switching losses, and driver
consumption, both of which are proportional to switching
frequency.
INPUT VOLTAGE FEEDFORWARD
The feedforward circuit of the LM27241 adjusts the slope of
the internal PWM ramp in proportion to the regulator input
voltage. See
Figure 1
for an illustration of how the duty cycle
changes as a result of the change in the slope of the ramp,
even though the error amplifier output has not had time to
react to the line disturbance. The almost instantaneous duty
cycle correction provided by the feedforward circuit signifi-
cantly improves line transient rejection.
FORCED-PWM MODE AND PULSE-SKIP MODE
Forced-PWM mode (FPWM) leads to Continuous Conduc-
tion Mode (CCM) even at very light loads. It is one of two
user-selectable
modes
of
LM27241. When FPWM is chosen (FPWM pin high), the
bottom FET will always be turned ON whenever the top FET
is OFF. See
Figure 2
for a typical FPWM plot.
operation
provided
by
the
20120109
FIGURE 1. Voltage Feedforward
20120110
CH1: HDRV, CH2: LDRV, CH3: SW, CH4: I
L
(0.2A/div)
Output 1V
@
0.04A, VIN = 10V, FPWM, L = 10μH, f = 300kHz
FIGURE 2. Normal FPWM Mode Operation at Light
Loads
L
www.national.com
10
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM2746 | Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller |
| LM2746MXA | Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller |
| LM2746MXAX | Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller |
| LM2753SD | High Power Switched Capacitor Voltage Convertor/Flash LED Driver |
| LM2753 | High Power Switched Capacitor Voltage Convertor/Flash LED Driver |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM27241MTCX/NOPB | 功能描述:IC REG CTRLR BUCK PWM VM 20TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝: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 升壓:無 回掃:是 反相:無 倍增器:無 除法器:無 Cuk:無 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)品目錄頁面:1316 (CN2011-ZH PDF) |
| LM27243A E WAF | 制造商:Texas Instruments 功能描述: |
| LM2724A | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:High Speed 3A Synchronous MOSFET Driver |
| LM2724ALD | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:High Speed 3A Synchronous MOSFET Driver |
| LM2724ALD/NOPB | 功能描述:IC DRIVER MOSFET DUAL SYNC 8-LLP RoHS:否 類別:集成電路 (IC) >> PMIC - MOSFET，電橋驅(qū)動器 - 外部開關(guān) 系列:- 標準包裝:50 系列:- 配置:低端 輸入類型:非反相 延遲時間:40ns 電流 - 峰:9A 配置數(shù):1 輸出數(shù):1 高端電壓 - 最大（自引導啟動）:- 電源電壓:4.5 V ~ 35 V 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:TO-263-6，D²Pak（5 引線+接片），TO-263BA 供應(yīng)商設(shè)備封裝:TO-263 包裝:管件 |
發(fā)布緊急采購，3分鐘左右您將得到回復。