參數(shù)資料
型號: MAX6301
廠商: Maxim Integrated Products, Inc.
英文描述: +5V, Low-Power uP Supervisory Circuits with Adjustable Reset/Watchdog
中文描述: +5V、低功耗、微處理器監(jiān)控電路,帶有可調(diào)節(jié)的復(fù)位/看門狗定時器
文件頁數(shù): 6/12頁
文件大?。?/td> 102K
代理商: MAX6301
_______________Detailed Desc ription
Reset Func tion/Output
The reset output is typically connected to the reset
input of a microprocessor (μP). A μP’s reset input starts
or restarts the μP in a known state. The MAX6301–
MAX6304 μP supervisory circuits provide the reset
logic to prevent code-execution errors during power-
up, power-down, and brownout conditions (see Typical
Operating Circuit.
For the MAX6301/MAX6303,
RESET
changes from high
to low whenever the monitored voltage (V
IN
) drops
below the reset threshold voltage (V
RST
).
RESET
remains low as long as V
IN
is below V
RST
. Once V
IN
exceeds V
RST
,
RESET
remains low for the reset timeout
period, then goes high. When a reset is asserted due to
a watchdog timeout condition,
RESET
stays low for the
reset timeout period. Anytime reset asserts, the watch-
dog timer clears. At the end of the reset timeout period,
RESET
goes high and the watchdog timer is restarted
from zero. If the watchdog timeout period is exceeded
again, then
RESET
goes low again. This cycle contin-
ues unless WDI receives a transition.
On power-up, once V
CC
reaches 1V,
RESET
is guaran-
teed to be a logic low. For information about applica-
tions where V
CC
is less than 1V, see the section
Ensuring a Valid
RESET
/RESET Output Down to V
CC
=
0V (MAX6303/MAX6304). As V
CC
rises,
RESET
remains
low. When V
IN
rises above V
RST
, the reset timer starts
and
RESET
remains low. When the reset timeout period
ends,
RESET
goes high.
On power-down, once V
IN
goes below V
RST
,
RESET
goes low and is guaranteed to be low until V
CC
droops
below 1V. For information about applications where
V
CC
is less than 1V, see the section Ensuring a Valid
RESET
/RESET Output Down to V
CC
= 0V (MAX6303/
MAX6304).
The MAX6302/MAX6304 active-high RESET output is
the inverse of the MAX6301/MAX6303 active-low
RESET
output, and is guaranteed valid for V
CC
> 1.31V.
Reset T hreshold
These supervisors monitor the voltage on RESET IN.
The MAX6301–MAX6304 have an adjustable reset
threshold voltage (V
RST
) set with an external resistor
voltage divider (Figure 1). Use the following formula to
calculate V
RST
(the point at which the monitored volt-
age triggers a reset):
V
R2
where V
RST
is the desired reset threshold voltage and
V
TH
is the reset input threshold (1.22V). Resistors R1 and
R2 can have very high values to minimize current con-
sumption. Set R2 to some conveniently high value (1M
,
for example) and calculate R1 based on the desired
reset threshold voltage, using the following formula:
Watc hdog T imer
The watchdog circuit monitors the μP’s activity. If the μP
does not toggle the watchdog input (WDI) within t
WD
(user selected), reset asserts. The internal watchdog
timer is cleared by reset, by a transition at WDI (which
can detect pulses as short as 30ns), or by a transition
at WDS. The watchdog timer remains cleared while
reset is asserted; as soon as reset is released, the timer
starts counting (Figure 2).
The MAX6301–MAX6304 feature two modes of watch-
dog timer operation: normal mode and extended mode.
In normal mode (WDS = GND), the watchdog timeout
period is determined by the value of the capacitor con-
nected between SWT and ground (see the section
Selecting the Reset and Watchdog Timeout Capacitor.
In extended mode (WDS = V
CC
), the watchdog timeout
period is multiplied by 500. For example, in the extend-
ed mode, a 1μF capacitor gives a watchdog timeout
period of 22 minutes (see the graph Extended-Mode
Watchdog Timeout Period vs. C
SWT
in the Typical
Operating Characteristics).
In extended mode, the watchdog function can be dis-
abled by leaving WDI unconnected or by three-stating
the driver connected to WDI. In this mode, the watch-
dog input is internally driven low during the watchdog
R1
R2
V
V
1
RST
TH
=
×
( )
V
R1 R2
(
V
RST
TH
=
×
)( )
0.1μF
MAX6301
MAX6302
MAX6303
MAX6304
V
CC
RESET IN
R2
R1
V
IN
V
RST
= 1.22
(
R1 + R2
)
R2
M
+5V, Low-Power μP S upervisory Circ uits
with Adjustable Reset/Watc hdog
6
_______________________________________________________________________________________
Figure 1. Calculating the Reset Threshold Voltage (V
RST
)
相關(guān)PDF資料
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX6301_10 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:+5V, Low-Power μP Supervisory Circuits with Adjustable Reset/Watchdog
MAX6301CPA 功能描述:監(jiān)控電路 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
MAX6301CPA+ 功能描述:監(jiān)控電路 5V uPower Supervisor 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
MAX6301CSA 功能描述:監(jiān)控電路 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
MAX6301CSA+ 功能描述:監(jiān)控電路 5V uPower Supervisor 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