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| 型號： | SP802LEP |
| 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 |
| 文件頁數(shù)： | 10/16頁 |
| 文件大?。?/td> | 631K |
| 代理商： | SP802LEP |
SP690A/692ADS/08 SP690A/692A Low Power Microprocessor Supervisory with Battery Switch-Over
Copyright 2000 Sipex Corporation
10
The
SP805L/M
active-high RESET output is
the inverse of the
SP690A/SP692A/SP802
RE-
SET output, and is valid with V
down to 1V.
Some
μ
P's, such as Intel's 80C51, require an
active-high reset pulse.
Watchdog Input
The watchdog circuit monitors the
μ
P's activity.
If the
μ
P does not toggle the watchdog input
(WDI) within 1.6sec, a reset pulse is triggered.
The internal 1.6sec timer is cleared by either a
reset pulse or by floating the WDI input. As long
as RESET is asserted or the WDI input is
floating, the timer remains cleared and does not
count. As soon as RESET is released and WDI
is driven high or low, the timer starts counting.
It can detect pulses as short as 50ns.
Power-Fail Comparator
The Power-Fail Comparator can be used as an
under-voltage detector to signal the failing of a
power supply (it is completely separate from the
rest of the circuitry and does not need to be
dedicated to this function). The PFI input is
compared to an internal 1.25V reference. If PFI
is less than 1.25V, PFO goes low. The external
voltage divider drives PFI to sense the
unregulated DC input to the +5V regulator. The
voltage-divider ratio can be chosen such that the
voltage at PFI falls below 1.25V just before the
+5V regulator drops out. PFO then triggers an
interrupt which signals the
μ
P to prepare for
power-down.
When V
connects to V
, the power-fail
comparator is turned off and PFO is forced low
to conserve backup-battery power.
Backup-Battery Switchover
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 V
,
the RAM is assured to have power if V
fails.
As long as V
exceeds the reset threshold,
V
connects to V
through a 0.6
PMOS
power switch. Once V
CC
falls below the reset
threshold, V
or V
, whichever is higher,
switches to V
. V
connects to V
through a 5
switch only when V
is below the
reset threshold and V
BATT
is greater than V
CC
.
When V
exceeds the reset threshold, it is
connected to V
OUT
, regardless of the voltage
applied to V
Figure 13
. During this time,
the diode (D1) between V
BATT
and V
OUT
will
conduct current from V
BATT
OUT
if V
BATT
is
more than .6V above V
OUT
.
When V
connects to V
, backup mode is
activated and the internal circuitry will be pow-
ered from the battery
Figure 14
. When V
is
just below V
, in the backup mode the
current drawn from V
will be typically
30
μ
A. When V
drops to more than 1V below
V
, the internal switchover comparator shuts
off and the supply current falls to less than 0.6
μ
A.
Reset Threshold = 4.65V in SP690A/802L/805L
Reset Threshold = 4.40V in SP692A/802M/805M
Figure 13. BACKUP-BATTERY Switchover Block Diagram
SW1
D1
D2
D3
SW2
V
BATT
V
CC
GND
V
OUT
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相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SP802M | Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP802MCN | Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP802MCP | Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP802MEN | Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP802MEP | 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 |
|---|---|
| SP802M | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP802MCN | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP802MCN/TR | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP802MCP | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Low Power Microprocessor Supervisory with Battery Switch-Over |
| SP802MEN | 制造商:Exar Corporation 功能描述:Power Supply Supervisor Circuit, 8 Pin, Plastic, SOP |
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