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參數(shù)資料
| 型號(hào)： | MAX802L |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Microprocessor Supervisory Circuits(具有4.65V復(fù)位的,微處理器的監(jiān)控電路) |
| 中文描述： | 微處理器監(jiān)控電路 |
| 文件頁(yè)數(shù)： | 9/12頁(yè) |
| 文件大?。?/td> | 122K |
| 代理商： | MAX802L |
M
Mic roproc essor S upervisory Circ uits
_______________________________________________________________________________________
9
connected directly to the V
MAX690A/MAX692A/MAX802L/MAX802M/MAX805L with
no additional circuitry (see the Typical Operating Circuit.
However, batteries with open-circuit voltages that are
greater
cannot
be used for backup, as current is sourced
into the substrate through the diode (D1 in Figure 3) when
V
CC
is close to the reset threshold.
input of the
Operation
Without a Bac kup Power S ourc e
If a backup power source is not used, ground V
and connect V
to V
. Since there is no need to
switch over to any backup power source, V
does
not need to be switched. A direct connection to V
eliminates any voltage drops across the switch which
may push V
OUT
below V
CC
.
Replac ing the Bac kup Battery
The backup battery can be removed while V
CC
remains
valid, without danger of triggering RESET/
RESET
. As
long as V
stays above the reset threshold, battery-
backup mode cannot be entered. In other switchover
PFO
V
CC
GND
MAX690A
MAX692A
MAX802L
MAX802M
MAX805L
+5V
R
2
R
1
PFI
+5V
0V
PFO
V
TRIP
V-
0V
V-
NOTE:
TRIP
R1
Figure 7. Monitoring a Negative Voltage
5
1.25
1.25 - VTRIP
R2
=
ICs where battery-backup mode is entered whenever
V
gets close to V
, an unconnected V
pin
accumulates leakage charge and triggers
RESET/
RESET
in error.
Adding Hysteresis to the
Power-Fail Comparator
Hysteresis adds a noise margin to the power-fail com-
parator and prevents repeated triggering of PFO when
V
is close to its trip point. Figure 6 shows how to add
hysteresis to the power-fail comparator. Select the
ratio of R
and R
such that PFI sees 1.25V when V
IN
falls to its trip point (V
). R
adds the hysteresis. It
will typically be an order of magnitude greater than R
1
or R
(about 10 times either R
or R
). The current
through R
and R
should be at least 1μA to ensure
that the 25nA (max) PFI input current does not shift the
trip point. R
should be larger than 10k
so it does not
load down the
PFO
pin. Capacitor C1 adds additional
noise rejection.
Monitoring a Negative V oltage
The power-fail comparator can be used to monitor a
negative supply rail using the circuit of Figure 7. When
the negative rail is good (a negative voltage of large
magnitude),
PFO
is low. When the negative rail is
degraded (a negative voltage of lesser magnitude),
PFO
goes high. This circuit’s accuracy is affected by
the PFI threshold tolerance, the V
CC
line, and the resis-
tors.
Interfac ing to μPs with
Bidirec tional Reset Pins
μPs with bidirectional reset pins, such as the Motorola
68HC 11
series,
can
MAX690A/MAX692A/MAX802L/MAX802M
RESET
out-
put. If, for example, the
RESET
output is driven high
and the μP wants to pull it low, indeterminate logic lev-
els may result. To correct this, connect a 4.7k
resis-
tor between the
RESET
output and the μP reset I/O, as
in Figure 8. Buffer the
RESET
output to other system
components
contend
with
the
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX802M | Microprocessor Supervisory Circuits(具有看門(mén)狗和支持備用電池,高精度復(fù)位器) |
| MAX690A | Microprocessor Supervisory Circuits(帶看門(mén)狗和電池開(kāi)關(guān)的復(fù)位器,復(fù)位門(mén)限4.65V) |
| MAX692A | Microprocessor Supervisory Circuits(帶看門(mén)狗和電池開(kāi)關(guān)復(fù)位器,復(fù)位閾值4.40V) |
| MAX8069 | Low-Voltage Reference |
| MAX8069ESA | Low-Voltage Reference |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX802LCPA | 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 |
| MAX802LCPA+ | 功能描述:監(jiān)控電路 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 |
| MAX802LCSA | 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 |
| MAX802LCSA+ | 功能描述:監(jiān)控電路 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 |
| MAX802LCSA+T | 功能描述:監(jiān)控電路 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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