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參數資料
| 型號： | LM9072S |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | Dual Tracking Low-Dropout System Regulator |
| 中文描述： | DUAL OUTPUT, FIXED POSITIVE LDO REGULATOR, PSSO9 |
| 封裝： | POWER, TO-263, 9 PIN |
| 文件頁數： | 8/15頁 |
| 文件大小： | 477K |
| 代理商： | LM9072S |
Application Information
(Continued)
KEEP-ALIVE INPUT (Pin 8)
This CMOS logic level compatible input provides a system
with the ability to control its own ON/OFF sequencing. The
Keep-Alive Input is OR’ed with the ON/OFF Input so either
one can independently control the regulators.
As shown in the Operational Characteristics a system con-
troller can take the Keep-Alive input high at any time. If the
ON/OFF switch is opened, this high level on Keep-Alive will
keep the regulators ON and the entire system operational.
This control is useful for providing as much time as neces-
sary for a system to perform “housekeeping” chores such as
programming EEPROM with system information prior to
turning itself OFF (by taking the Keep-Alive Input low) and
reverting to the low quiescent current state.
Asecond use of the Keep-Alive Input can be from other mod-
ules which need information from the module powered by
the LM9072, Figure 3 A CMOS logic high level (
>
2V) on
this input will power up the system as needed independent
from the normal ON/OFF switch.
System Keep-Alive Operation
Figure 4 illustrates the basic concept of Keep-Alive opera-
tion. The LM9072 provides regulated supplies to an entire
microcontroller based system or module including remote
sensors. The system is switched ON or OFF by a switch con-
nected to the unregulated input supply and the ON/OFF in-
put, pin 1. When closed the regulators turn ON and the sys-
tem is held in a reset state for the duration of the delayed
reset interval controlled by C
DELAY
.
Once normal operation of the system begins, the controller
needs to set an output line connected to the Keep-Alive in-
put, pin 8, high. The system remains in normal operation un-
til switched OFF by opening the ON/OFF switch. With
Keep-Alive high the entire system remains normally biased
and will remain operational until the Keep-Alive input is taken
low.
Transistor Q1 is shown as a means to inform the controller
that the ON/OFF switch has been opened. This high level on
an input line tells the controller that the system has been
switched OFF. This indicates the start of the Keep-Alive in-
terval. The system can perform whatever actions required to
obtain the proper OFF state before actually powering down.
These general housekeeping tasks can include putting ex-
ternal devices in the proper OFF condition and storing vari-
ous system variables in EPROM for example. With the con-
troller in command of the Keep-Alive interval these tasks can
take whatever time necessary to complete.
When completed the controller takes the Keep-Alive input to
a low level and the entire system shuts down. The LM9072
powers down to a low quiescent current mode with less than
100 μA drawn from the input supply.
To initiate the Keep-Alive routine before actual power down,
it is important for the system controller to know when the sys-
tem has been switched OFF. To eliminate any interface be-
tween the controller and the ON/OFF switch and potentially
noisy unregulated input supply, a simple logic scheme
shown in Figure 5 can be used. With this circuitry the Reset
output from the LM9072 provides the ON/OFF sensing input
to the controller.
When switched OFF, the main regulator output will fall out of
regulation and generate a low logic level on the Reset out-
put. This input to the controller provides the switch OFF indi-
cation and initiates the Keep-Alive interval.
Control of the Keep-Alive duration is set by a logic 1 on the
Keep-Alive output line from the system controller. This high
level prevents the Reset output from resetting the entire sys-
tem and also gates the Keep-Alive input signal to the
LM9072. The inverted Reset signal provides a logic 1 to the
Keep-Alive input of the LM9072.
The Main output will only drop out of regulation for a very
short time before the Keep-Alive input turns it back on.
The Reset output remains low for the delay time interval.
When it returns high the Main output switches OFF and back
ON again very quickly. This continues until the system con-
troller takes the Keep-Alive output line to a logic low level.
DS012906-19
FIGURE 3. Remote ON/OFF Control
L
www.national.com
8
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相關代理商/技術參數 |
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| LM9072SX | 功能描述:IC REG LDO 5V .35A/80MA TO-263-9 RoHS:是 類別:集成電路 (IC) >> PMIC - 穩壓器 - 線性 系列:- 標準包裝:1 系列:- 穩壓器拓撲結構:正，固定式 輸出電壓:4V 輸入電壓:最高 16V 電壓 - 壓降（標準）:0.28V @ 150mA 穩壓器數量:1 電流 - 輸出:150mA 電流 - 限制（最小）:- 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:5-VFBGA 供應商設備封裝:5-uSMD 包裝:Digi-Reel® 其它名稱:LP2985AIBP-4.0DKR |
| LM9072T | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dual Tracking Low-Dropout System Regulator |
| LM9073 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dual High Current Low-Dropout System Regulator |
| LM9073S | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dual High Current Low-Dropout System Regulator |
| LM9073SX | 功能描述:IC REG LDO 5V .7A/.1A TO-263-11 RoHS:否 類別:集成電路 (IC) >> PMIC - 穩壓器 - 線性 系列:- 標準包裝:1 系列:- 穩壓器拓撲結構:正，固定式 輸出電壓:4V 輸入電壓:最高 16V 電壓 - 壓降（標準）:0.28V @ 150mA 穩壓器數量:1 電流 - 輸出:150mA 電流 - 限制（最小）:- 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:5-VFBGA 供應商設備封裝:5-uSMD 包裝:Digi-Reel® 其它名稱:LP2985AIBP-4.0DKR |
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