- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄385477 > LM2746 (National Semiconductor Corporation) Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller PDF資料下載
參數(shù)資料
| 型號(hào)： | LM2746 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller |
| 中文描述： | 低壓N溝道MOSFET同步降壓穩(wěn)壓控制器 |
| 文件頁數(shù)： | 10/24頁 |
| 文件大小： | 1087K |
| 代理商： | LM2746 |
Application Information
(Continued)
Where f
SW
is in Hz and R
FADJ
is in k
.
TRACKING A VOLTAGE LEVEL
The LM2746 can track the output of a master power supply
during soft-start by connecting a resistor divider to the SS/
TRACK pin. In this way, the output voltage slew rate of the
LM2746 will be controlled by the master supply for loads that
require precise sequencing. Because the output of the mas-
ter supply is divided down, in order to track properly the
output voltage of the LM2746 must be lower than the voltage
of the master supply. When the tracking function is used no
soft-start capacitor should be connected to the SS/TRACK
pin. However in all other cases, a C
value of at least 1nF
between the soft-start pin and ground should be used.
One way to use the tracking feature is to design the tracking
resistor divider so that the master supply’s output voltage
(V
OUT1
) and the LM2746’s output voltage (represented sym-
bolically in
Figure 1
as V
OUT2
, i.e. without explicitly showing
the power components) both rise together and reach their
target values at the same time. For this case, the equation
governing the values of the tracking divider resistors R
T1
and
R
T2
is:
The current through R
should be about 3-4 mA for precise
tracking. The final voltage of the SS/TRACK pin should be
set higher than the feedback voltage of 0.6V (say about
0.65V as in the above equation). If the master supply voltage
were 5V and the LM2746 output voltage were 1.8V, for
example, then the value of R
T1
needed to give the two
supplies identical soft-start times would be 150
. A timing
diagram for the equal soft-start time case is shown in
Figure
2
.
TRACKING A VOLTAGE SLEW RATE
The tracking feature can alternatively be used not to make
both rails reach regulation at the same time but rather to
have similar rise rates (in terms of output dV/dt). This
method ensures that the output voltage of the LM2746 al-
ways reaches regulation before the output voltage of the
master supply. In this case, the tracking resistors can be
determined based on the following equation:
For the example case of V
= 5V and V
= 1.8V, with
R
set to 150
as before, R
is calculated from the above
equation to be 265
. A timing diagram for the case of equal
slew rates is shown in
Figure 3
.
SEQUENCING
The start up/soft-start of the LM2746 can be delayed for the
purpose of sequencing by connecting a resistor divider from
the output of a master power supply to the SD pin, as shown
in
Figure 4
.
20147707
FIGURE 1. Tracking Circuit
20147708
FIGURE 2. Tracking with Equal Soft-Start Time
20147710
FIGURE 3. Tracking with Equal Slew Rates
L
www.national.com
10
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| 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 |
| LM2753SDX | 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 |
|---|---|
| LM2746MXA | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Low Voltage N-Channel MOSFET Synchronous Buck Regulator Controller |
| LM2746MXA/NOPB | 功能描述:IC REG CTRLR BUCK PWM VM 14TSSOP RoHS:是 類別: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 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 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 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) |
| 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 |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。