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參數(shù)資料
| 型號(hào)： | SP805MEP |
| 英文描述： | Low Power Microprocessor Supervisory with Battery Switch-Over |
| 中文描述： | 低功耗微處理器監(jiān)控與電池開關(guān)過 |
| 文件頁(yè)數(shù)： | 12/16頁(yè) |
| 文件大?。?/td> | 631K |
| 代理商： | SP805MEP |
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SP690A/692ADS/08 SP690A/692A Low Power Microprocessor Supervisory with Battery Switch-Over
Copyright 2000 Sipex Corporation
12
Allowable Backup Power-Source
Batteries
Lithium batteries work very well as backup
batteries due to very low self-discharge rate and
high energy density. Single lithium batteries
with open-circuit voltages of 3.0V to 3.6V are
ideal. Any battery with an open-circuit voltage
less than the minimum reset threshold plus 0.3V
can be connected directly to the V
input of
this series with no additional circuitry; see
FIGURE 12. However, batteries with open-
circuit voltages that are greater than this value
cannot be used for backup, as current is sourced
into V
OUT
through the diode
(D1 in Figure 13)
when V
CC
is close to the reset threshold.
Operation Without a Backup Power
Source
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
.
Replacing the Backup Battery
The backup battery can be removed while V
remains valid, without danger of triggering
RESET/RESET. As long as V
stays above the
reset threshold, battery-backup mode cannot be
entered.
Adding Hysteresis to the Power-Fail
Comparator
Hysteresis adds a noise margin to the power-fail
comparator and prevents repeated triggering of
PFO when V
is close to its trip point.
Figure 18
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
falls to its trip
point (V
). R
adds the hysteresis. It will
typically be an order of magnitude greater (about
10 times) than R
or R
. The current through R
1
and R
should be at least 1
μ
A 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 Voltage
The power-fail comparator can be used to monitor
a negative supply rail using the circuit of
Figure
19.
When the negative rail is valid, PFO is low.
When the negative supply voltage drops, PFO
goes high. This circuit's accuracy is
affected by the PFI threshold tolerance, the V
CC
voltage, and the resistors, R1 and R2.
Figure 18. Adding Hysteresis to the POWER-FAIL
Comparator
PFI
PFO
R
3
*C
1
R
2
R
1
V
IN
connect to
μ
P
V
CC
+5V
GND
PFO
V
IN
+5V
0V0V
V
L
V
H
V
TRIP
*optional
V
TRIP
=
R
2
R
1
+ R
2
V
H
=
R
2
|| R
3
R
1
+ R
2
|| R
3
1.25
R
2
=V
L
- 1.25
R
1
5.0 - 1.25
R
3
+
1.25
1.25
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SP690A | Low Power Microprocessor Supervisory with Battery Switch-Over(低功耗，微處理器監(jiān)控電路（帶電池開關(guān)）) |
| SP692A | Low Power Microprocessor Supervisory with Battery Switch-Over(低功耗，微處理器監(jiān)控電路（帶電池開關(guān)）) |
| SP690SCP | 3.0V/3.3V Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP690SEN | 3.0V/3.3V Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP690SEP | 3.0V/3.3V Low Power Microprocessor Supervisory with Battery Switch-Over |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SP805R | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:3.0V/3.3V Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP805RCN | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:3.0V/3.3V Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP805RCP | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:3.0V/3.3V Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP805REN | 制造商:Exar Corporation 功能描述:Power Supply Supervisor Circuit, 8 Pin, Plastic, SOP |
| SP805REP | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:3.0V/3.3V Low Power Microprocessor Supervisory with Battery Switch-Over |
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