參數(shù)資料
型號(hào)： MAX793
廠(chǎng)商： Maxim Integrated Products, Inc.
英文描述： 3.0V/3.3V Adjustable Microprocessor Supervisory Circuits(具有監(jiān)控器、芯片使能和支持備用電池的復(fù)位器)
中文描述： 3.0V/3.3V可調(diào)、微處理器監(jiān)控電路
文件頁(yè)數(shù)： 14/20頁(yè)
文件大小： 211K
代理商： MAX793
M
3.0V /3.3V Adjustable Mic roproc essor
S upervisory Circ uits
14
______________________________________________________________________________________
The power-fail comparator turns off and PFO goes low
when V
CC
falls below V
SW
on power-down. During the
first half of the reset timeout period (t
RP
), PFO is forced
high, irrespective of V
PFI
. At the beginning of the sec-
ond half of t
RP
, the power-fail comparator is enabled
and PFO follows PFI. If the comparator is unused, con-
nect PFI to V
CC
and leave PFO unconnected. PFO may
be connected to MR so that a low voltage on PFI will
generate a reset (Figure 12b). In this configuration,
when the monitored voltage causes PFI to fall below
V
PFT
, PFO pulls MR low, causing a reset to be assert-
ed. Reset remains asserted as long as PFO holds MR
low, and for 200ms after PFO pulls MR high when the
monitored supply is above the programmed threshold.
Bac kup-Battery S witc hover
In the event of a brownout or power failure, it may be
necessary to preserve the contents of RAM. With a
backup battery installed at BATT, the devices automati-
cally switch RAM to backup power when V
CC
falls. In
order to allow the backup battery (e.g., a 3.6V lithium
cell) to have a higher voltage than V
CC
, this family of μP
supervisors (designed for 3.3V and 3V systems) does
not always connect BATT to OUT when V
BATT
is
greater than V
CC
. BATT connects to OUT (through a
140
switch) either when V
CC
falls below V
SW
and
V
BATT
is greater than V
CC
,
or
when V
CC
falls below
1.75V (typ) regardless of the BATT voltage.
Switchover at V
SW
ensures that battery-backup mode is
entered before V
OUT
gets too close to the 2.0V mini-
mum required to reliably retain data in most CMOS
RAM, (switchover at higher V
CC
voltages would
decrease backup-battery life). When V
CC
recovers,
switchover is deferred either until V
CC
crosses V
BATT
if
V
BATT
is below V
RST
, or when V
CC
rises above the
reset threshold (V
RST
) if V
BATT
is above V
RST
. This
power-up switchover technique prevents V
CC
from
charging the backup battery through OUT when using
an external transistor driven by BATT ON. OUT con-
nects to V
CC
through a 4
(max) PMOS power switch
when V
CC
crosses the reset threshold (Figure 13).
BAT T ON (MAX 793/MAX 794)
BATT ON is high when OUT is connected to BATT.
Although BATT ON can be used as a logic output to
indicate the battery switchover status, it is most often
used as a gate or base drive for an external pass tran-
sistor for high-current applications (see Driving an
External Switch with BATT ON in the Applications
Information section). When V
CC
exceeds V
RST
on
power-up, BATT ON sinks 3.2mA at 0.4V. In battery-
backup mode, this terminal sources 100μA from BATT.
MAX793
MAX794
V
CC
GND
PFI
PFO
R1
R2
V
IN
0V
V
IN
PFO
V
TRIP
V
L
V
PFT
= 1.237V
V
PFH
= 10mV
WHERE
3.0V OR 3.3V
V
TRIP
= R2
+
R1
1
)
(
R2
1
–
R1
V
CC
(V
PFT
+ V
PFH
)
V
L
= R2
+
R1
1
)
(
R2
1
–
R1
V
CC
(V
PFT
)
NOTE: V
TRIP,
V
L
ARE NEGATIVE
V
CC
MAX793
MAX794
V
CC
GND
PFI
PFO
R1
R2
PFO
V
TRIP
V
H
3.0V OR 3.3V
V
IN
V
TRIP
=
)
(
R2
R1
+
R2
V
PFT
V
H
=
(V
PFT
+
V
PFH
)
V
CC
V
IN
MR
(b)
(a)
)
(
R2
R1
+
R2
Figure 12. Using the Power-Fail Comparator to Monitor an Additional Power Supply: (a) V
IN
Is Negative, (b) V
IN
Is Positive
相關(guān)PDF資料
PDF描述
MAX794 3.0V/3.3V Adjustable Microprocessor Supervisory Circuits(具有可調(diào)閾值監(jiān)控器、芯片使能和支持備用電池的復(fù)位器)
MAX796 Step-Down Controllers with Synchronous Rectifier for CPU Power(3.3V/5V/可調(diào),帶有同步整流器的PWM步降控制器，用于筆記本電腦)
MAX797 Step-Down Controllers with Synchronous Rectifier for CPU Power(3.3V/5V/可調(diào),帶有同步整流器的PWM步降控制器，用于筆記本電腦)
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX793RCPE 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)電壓: 欠電壓閾值: 過(guò)電壓閾值: 輸出類(lèi)型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開(kāi)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
MAX793RCPE+ 功能描述:監(jiān)控電路 3/3.3/AdjV MPU Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)電壓: 欠電壓閾值: 過(guò)電壓閾值: 輸出類(lèi)型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開(kāi)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
MAX793RCSE 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)電壓: 欠電壓閾值: 過(guò)電壓閾值: 輸出類(lèi)型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開(kāi)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
MAX793RCSE+ 功能描述:監(jiān)控電路 3/3.3/AdjV MPU Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)電壓: 欠電壓閾值: 過(guò)電壓閾值: 輸出類(lèi)型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開(kāi)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
MAX793RCSE+T 功能描述:監(jiān)控電路 3/3.3/AdjV MPU Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)電壓: 欠電壓閾值: 過(guò)電壓閾值: 輸出類(lèi)型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開(kāi)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
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