參數(shù)資料
型號: LM3722IM5X-2.32
廠商: NATIONAL SEMICONDUCTOR CORP
元件分類: 電源管理
英文描述: SMT-AL(V-CHIP) CAPACITANCE=10 VOLT=100
中文描述: 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO5
封裝: SOT-23, 5 PIN
文件頁數(shù): 8/12頁
文件大小: 219K
代理商: LM3722IM5X-2.32
Timing Diagram
20014412
Circuit Information
Reset Output
The reset input of a μP initializes the device into a known
state. The LM3722/LM3723/LM3724 microprocessor voltage
monitoring circuits assert a forced reset output to prevent
code execution errors during power-up, power-down, and
brownout conditions.
RESET is guaranteed valid for V
1V. Once V
exceeds
the reset threshold, an internal timer maintains the output for
the reset timeout period. After this interval, reset goes high
and the microprocessor initializes itself into a known state.
The LM3722 and LM3724 offer an active-low RESET; the
LM3723 offers an active-high RESET.
As V
CC
drops below the reset threshold (such as during a
brownout), the reset activates (see the Negative-Going V
CC
Transients section). When V
CC
again rises above the reset
threshold, the internal timer starts. Reset holds until V
CC
exceeds the reset threshold for longer than the reset timeout
period. After this time, reset releases.
Additionally, the Manual Reset input (MR) will initiate a
forced reset. See the Manual Reset Input section.
The LM3722/LM3723/LM3724 reset outputs ignore short du-
ration glitches on V
and MR. See the Applications Infor-
mation section for details.
Reset Threshold
The LM3722/LM3723/LM3724 are available with reset volt-
ages of 4.63V, 3.08V, and 2.32V which are suitable for
monitoring 5.0V, 3.3V, and 2.5V supplies respectively. Other
reset thresholds in the 2.20V to 5.0V range, in 10 mV steps,
are available; contact National Semiconductor for details.
Manual Reset Input (MR)
Many μP-based products require a manual reset capability,
allowing the operator to initiate a reset. The MR input is fully
debounced and provides an internal 22 k
pull-up. When the
MR input is pulled below V
(0.25V
) for more than 100 ns,
reset is asserted after a typical delay of 2 μs. Reset remains
active as long as MR is held low, and releases after MR rises
above V
IH
and the reset timeout period expires. Use MR with
digital logic to assert reset or to daisy chain supervisory
circuits.
Applications Information
Benefits of Precision Reset Thresholds
A microprocessor supply supervisor must provide a reset
output within a predictable range of the supply voltage. A
common threshold range is between 5% and 10% below the
nominal supply voltage. The 4.63V, 3.08V and 2.32V options
of the LM3722/LM3723/LM3724 use highly accurate circuitry
to ensure that the reset threshold occurs only within this
range (for 5.0V, 3.3V and 2.5V supplies). Table 1shows how
the standard reset thresholds apply to 5.0V, 3.3V, and 2.5V
nominal supply voltages.
L
www.national.com
8
相關(guān)PDF資料
PDF描述
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