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參數(shù)資料
| 型號(hào)： | LM3881 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Power Sequencer |
| 中文描述： | 電力序 |
| 文件頁數(shù)： | 10/14頁 |
| 文件大?。?/td> | 218K |
| 代理商： | LM3881 |
ENABLE CIRCUIT
The enable circuit is designed with an internal comparator,
referenced to a bandgap voltage (1.22V), to provide a preci-
sion threshold. This allows the timing to be set externally
using a capacitor as shown in the diagram below. Alterna-
tively, sequencing can be based on a certain event such as a
line voltage reaching 90% of its nominal value by employing
a resistor divider from VCC to Enable.
30048407
FIGURE 6. Precision Enable Circuit
Using the internal pull-up current source to charge the exter-
nal capacitor C
EN
, the time delay while the enable voltage
reaches the required threshold, assuming EN is charging
from 0V, can be calculated by the equation as follows.
30048404
FIGURE 7. Enable Delay Timing
A resistor divider can also be used to enable the LM3881
based on exceeding a certain VCC supply voltage threshold.
Care needs to be taken when sizing the resistor divider to
include the effects of the internal EN pull-up current source.
The supply voltage for which EN is asserted is given by
30048410
FIGURE 8. Enable Based On Input Supply Level
One of the features of the enable pin is that it provides glitch
free operation. The timer will start counting at a rising thresh-
old, but will always reset if the enable pin is de-asserted
before the first output flag is released. This is illustrated in the
timing diagram below, assuming INV is low.
30048411
FIGURE 9. Enable Glitch Timing, INV Low
If the EN pin remains high for the entire power up sequence,
then the part will operate as shown in the standard timing di-
agrams. However, if the EN signal is de-asserted before the
power-up sequence is completed, the part will enter a con-
trolled shutdown. This allows the system to initiate a con-
trolled power sequence, preventing any latch conditions to
occur. The following timing diagrams describe the flag se-
quence if the EN pin is de-asserted after FLAG1 releases, but
before the entire power-up sequence is completed. INV is as-
sumed low.
www.national.com
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3881EVAL | 功能描述:電源管理IC開發(fā)工具 LM3881 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 |
| LM3881EVAL | 制造商:Texas Instruments 功能描述:EVAL BOARD, LM3881, POWER SEQUENCER |
| LM3881MM | 制造商:Texas Instruments 功能描述:Power Sequencer 8-Pin MSOP T/R 制造商:Texas Instruments 功能描述:IC, POWER SEQUENCER, 2.7 TO 5.5V |
| LM3881MM/NOPB | 功能描述:監(jiān)控電路 POWER SEQUENCER RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| LM3881MME | 制造商:Texas Instruments 功能描述:Power Sequencer T/R |
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