參數(shù)資料
型號(hào)： LM2744
廠商： National Semiconductor Corporation
英文描述： Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller with External Reference
中文描述： 低壓N溝道MOSFET同步降壓穩(wěn)壓控制器與外部參考
文件頁(yè)數(shù)： 11/22頁(yè)
文件大?。?/td> 663K
代理商： LM2744
Application Information
(Continued)
A desired delay time t
DELAY
between the startup of the
master supply output voltage and the LM2744 output voltage
can be set based on the SD pin low-to-high threshold V
SD-IH
and the slew rate of the voltage at the SD pin, SR
SD
:
t
DELAY
= V
SD-IH
/ SR
SD
Note again, that in Figure 4, the LM2744’s output voltage
has been represented symbolically as V
OUT2
, i.e. without
explicitly showing the power components.
V
is typically 1.08V and SR
is the slew rate of the SD
pin voltage. The values of the sequencing divider resistors
R
and R
set the SR
based on the master supply
output voltage slew rate, SR
OUT1
, using the following equa-
tion:
For example, if the master supply output voltage slew rate
was 1V/ms and the desired delay time between the startup
of the master supply and LM2744 output voltage was 5ms,
then the desired SD pin slew rate would be (1.08V/5ms) =
0.216V/ms. Due to the internal impedance of the SD pin, the
maximum recommended value for R
is 1k
. To achieve
the desired slew rate, R
would then be 274
. A timing
diagram for this example is shown in
Figure 5
.
SD PIN IMPEDANCE
When connecting a resistor divider to the SD pin of the
LM2744 some care has to be taken. Once the SD voltage
goes above V
, a 17 μA pull-up current is activated as
shown in
Figure 6
. This current is used to create the internal
hysteresis (
)
170mV); however, high external impedances
will affect the SD pin logic thresholds as well. The external
impedance used for the sequencing divider network should
preferably be a small fraction of the impedance of the SD pin
for good performance (around 1k
).
MOSFET GATE DRIVERS
The LM2744 has two gate drivers designed for driving
N-channel MOSFETs in a synchronous mode. Note that
unlike most other synchronous controllers, the bootstrap
capacitor of the LM2744 provides power not only to the
driver of the upper MOSFET, but the lower MOSFET driver
20106014
FIGURE 4. Sequencing Circuit
20106011
FIGURE 5. Delay for Sequencing
20106006
FIGURE 6. SD Pin Logic
L
www.national.com
11
相關(guān)PDF資料
PDF描述
LM2796TL Dual-Display White LED Driver with 3/2x Switched Capacitor Boost
LM2796TLX Dual-Display White LED Driver with 3/2x Switched Capacitor Boost
LM2796 Dual-Display White LED Driver with 3/2x Switched Capacitor Boost
LM2925 Cap-Free, NMOS, 150mA Low Dropout Regulator with Reverse Current Protection
LM2925T Cap-Free, NMOS, 150mA Low Dropout Regulator with Reverse Current Protection
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM2744EVAL 功能描述:電源管理IC開(kāi)發(fā)工具 EVAL BOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評(píng)估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V
LM2744MTC 功能描述:DC/DC 開(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
LM2744MTC/NOPB 功能描述:DC/DC 開(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
LM2744MTCX 功能描述:DC/DC 開(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
LM2744MTCX/NOPB 功能描述:DC/DC 開(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
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

*
*
*